Neogene Basin Evolution in the Southwestern Dominican Republic: a Foraminiferal Study

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1989 Neogene Basin Evolution in the Southwestern Dominican Republic: A Foraminiferal Study. Peter Paul Mclaughlin Jr Louisiana State University and Agricultural & Mechanical College

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Recommended Citation Mclaughlin, Peter Paul Jr, "Neogene Basin Evolution in the Southwestern Dominican Republic: A Foraminiferal Study." (1989). LSU Historical Dissertations and Theses. 4734. https://digitalcommons.lsu.edu/gradschool_disstheses/4734

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Neogene basin evolution in the southwestern Dominican Republic: A foraminiferal study

McLaughlin, Peter Paul, Jr., Ph.D.

The Louisiana State University and Agricultural and Mechanical Col., 1989

UMI 300 N. Zeeb Rd. Ann Arbor, MI 48106

A Dissertation

submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy

The Department of Geology and Geophysics

by Peter Paul McLaughlin, Jr. B.S., University of Delaware, 1984 May, 1989

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS

I would like to sincerely thank my advisors, Dr. Barun K. Sen Gupta and Dr. Willem A. van den Bold, for their guidance and invaluable support in this study. I came to Baton Rouge with the intention of working on a masters thesis on foraminifera; instead, they enocuraged me to pursue a doctorate and extended to me all of the resources at their disopsal. I will always be grateful for their help and encouragement. I feel especially fortunate to have had the opportunity to work with Wim van den Bold in the last four and one-half years preceding his retirement from the faculty at L.S.U.. Many hours of enthusiastic discussion of Caribbean geology were passed in his office, and these discussions are the basis of many of the ideas developed in this study. I can only describe the support lent me Barun Sen Gupta as "above and beyond the call of duty". On the logistical end, this ranged from arranging financial support for this project to generous access to his personal computer and library; on the academic end, his knowledge of the Foraminifera and critical evaluation of the ideas in this study helped keep it on firm scientific footing. This study would have been much more difficult and much less productive without the enthusiastic cooperation of Dr. Paul Mann (Institute for Geophysics, University of Texas at Austin). Paul originally suggested a biostratigraphic study in the Azua area; from invaluable assistance in the field to stimulating discussions on regional geology and tectonics, his involvement helped considerably to broaden the scope of the study. Special thanks are also extended to Dr. Joseph Hazel. Besides passing on a contagious enthusiasm for stratigraphy, he critically reviewed manuscripts for this dissertation, provided financial support for one semester, and kindly helped in exploring employment opportunities. I also wish to thank Dr. Charles McCabe and Dr. Arnold Bouma for serving as committee members and for their interest in this project. Chad McCabe's interest in looking at the magnetostratigraphy of the Azua Basin sequence and cooperation in the field work are sincerely appreciated. Arnold Bouma was kind enough to agree to join the committee shortly after his arrival at L.S.U.; his special effort to famialiarize himself with a project already well underway and to lend valuable advice on the sedimentology are greatly appreciated. The assistance of the Direcci6n General de Minerfa, Dominican Republic, is gratefully acknowledged, with special thanks to Ivdn Tavares and Edwin Garcfa of the Departmento de Geologfa. Appreciation is also extended to Edwin Deveaux, Luis Pefia, and Javier Rodriguez for their ideas and aid in the field.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Last, but not least, I would like to thank a number of my fellow students, past and present, who were a great support network; their help, ideas, and friendship made this study and degree much easier to complete. Thanks guys (!): Jim Galluzzo, Scott Wendler, Rich Denne, Earl Manning (presently with LSU Museum of Geoscience), Ivan Gill (now on the faculty at Tulane University), Mike Ruth (George Washington University), and Christoph Huebeck (University of Texas at Austin). Research support was supplied by a National Science Foundation grant to van den Bold and Sen Gupta (EAR 872021), two Chevron USA, Inc. Field Scholarships, the Hugh McKee Micropaleontology Scholarship Fund, an ORF Grant from the university's Office of Graduate Planning, and a Cushman Foundation Student Research Grant.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. I dedicate this work to my wife Jennifer, without whose loving support none of this could have been done.

I would also like to give special thanks to my parents for cultivating my interest in learning, for their constant encouragement, and for their financial support down the home stretch.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS

Acknowledgements ii

Dedication iv

List of Tables vii

List of Figures ix

List of Plates xiii

Abstract xiv

Chapter 1 Introduction 1

Chapter 2 Neogene planktonic foraminiferal biostratigraphy 24 of the southwestern Dominican Republic

Chapter 3 Geology of the Enriquillo-Azua Basins, Dominican 66 Republic: Depositional History - Foraminiferal and Ostracode evidence

Chapter 4 Foraminiferal paleoenvironments of the 150 Azua Basin sequence, Miocene-Pliocene, Dominican Republic

Chapter 5 Migration of Neogene marine environments, 226 southwestern Dominican Republic

Chapter 6 Neogene benthic foraminifera from the Dominican 244 Republic: Taxonomic problems and solutions

Chapter 7 Conclusions 289

Appendix 1 List of foraminiferal species identified in the study 299

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix 2 Relative abundance data of benthic foraminiferal species 302 used in multivariate analyses.

Vita 318

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES

Table 2.1 Estimated relative abundance of planktonic foraminifera in 39 samples from the upper Rio Yaque del Sur and San Juan Valleys.

Table 2.2 Estimated relative abundance of planktonic foraminifera in 40 samples from the Quita Coraza area and the Arroyo Las Lajas section of the lower Rio Yaque del Sur Valley and the Rio Via section near Azua.

Table 2.3 Estimated relative abundance of planktonic foraminifera in 41 samples from the Fondo Negro area, lower Rio Yaque del Sur Valley.

Table 3.1 General bathymetric significance of some benthic foraminiferal 81 species from the southwestern Dominican Republic.

Table 3.2 Summary of criteria used to interpret depositional 96 environments for turbidite facies.

Table 3.3 Subsidence in the upper Rfo Yaque del Sur Valley, using 129 the method of Bandy and Amal (1960).

Table 3.4 Subsidence in the lower Rio Yaque del Sur Valley, using 129 the method of Bandy and Amal (1960).

Table 3.5 Summary of the geologic history of the Azua Basin. 135

Table 3.6 Summary of stratigraphic units for the Azua and 136 Enriquillo Basins.

Table 4.1 The rotated factor solutions for Factors 1-6. 171

Table 4.2 Regional comparison of occurrences of selected Azua Basin 185 species in other circum-Caribbean sequences.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 5.1 Paleoenvironmentally important benthic foraminiferal 232 species in the Azua Basin Neogene sedimentary sequence.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES

Fig. 1.1 Location of the dissertation field area on the island of Hispaniola. 3

Fig. 1.2 Map of the southwest Dominican Republic, showing the area 4 of this study, the Azua Basin (A) and the neighboring Enriquillo Basin (E).

Fig. 1.3 Tectonic features of the Caribbean. 5

Fig. 1.4 Structural features on the island of Hispaniola. 7

Fig. 1.5 Stratigraphic units recognized in the Azua Basin. 10

Fig. 2.1 Map of the study area, southwestern Dominican Republic. 28

Fig. 2.2 Map of the lower Rio Yaque del Sur Valley area. 30

Fig. 2.3 Map of the upper Rio Yaque del Sur Valley and 31 San Juan Valley areas.

Fig. 2.4 Map of the Rio Via section, near Azua. 32

Fig. 2.5 Chart showing ranges of species identified in this study. 33

Fig. 2.6 Correlation chart comparing the Neogene sequence of the 49 Azua Basin to other formations on Hispaniola and around the Caribbean.

Fig. 3.1 Location of the study area, in the southwestern Dominican 69 Republic, island of Hispaniola.

Fig. 3.2 Sampling localities in the upper Rfo Yaque del Sur and 71 Rfo San Juan Valleys, northwestern Azua Basin.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 3.3 Sampling localities in the lower Rio Yaque del Sur Valley, 72 southern Azua Basin.

Fig. 3.4 Neogene stratigraphic units in the Azua and Enriquillo Basins. 73

Fig. 3.5 Comparison of Azua Basin biostratigraphic studies 75

Fig. 3.6 Chart showing ranges of species identified in this study. 78

Fig. 3.7 Ostracode zonation of the post-Eocene part of the 80 Caribbean Cenozoic.

Fig. 3.8 Composite stratigraphic section for the upper Rfo Yaque 85 del Sur - San Juan Valley showing the range of bathymetrically-useful forms with the paleoenvironmental interpretation that these suggest for the section.

Fig. 3.9 Composite stratigraphic section for the lower Rfo Yaque 86 del Sur showing the range of bathymetrically-useful forms with the paleoenvironmental interpretation that these suggest for the section.

Fig. 3.10 Measured sections from the Trinchera Formation 92 turbidite sequence.

Fig. 3.11 Photos of outcrops of the Trinchera Formation, 94 Azua - Barahona highway.

Fig. 3.12 Ternary compositional diagrams for sandstones in the 102 Trinchera Formation turbidite sequence.

Fig. 3.13 Ostracod occurrences in the southern Azua Basin. I l l

Fig. 3.14 Measured section from the Arroyo Blanco Formation 114 coastal clastic sequence, Arroyo Las Lajas.

Fig. 3.15 Ostracode occurrences in the Enriquillo Basin. 123

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 3.16 Geographic distribution of the genus Cvprideis in the late 125 Miocene and Pliocene in the Greater Antilles, with greatest concentration of localities in southern Hispaniola.

Fig. 3.17 Paleogeographic cartoon for the Azua and Enriquillo Basins 133 from the Middle Miocene through Middle Pliocene.

Fig. 3.18 Schematic cross-section of the southwestern Dominican Republic. 134

Fig. 4.1 Map of the study area, Azua Basin, southwestern 154 Dominican Republic..

Fig. 4.2 Map of the northwestern arm of the basin, in the upper 159 Rfo Yaque del Sur Valley and the San Juan Valley.

Fig. 4.3 Map of the Rfo Via section, north of Azua. 160

Fig. 4.4 Map of the Cerros de los Quemadillos area, east of the 162 Rfo Yaque del Sur.

Fig. 4.5 The southern part of the basin, in the lower Rfo Yaque 163 del Sur Valley.

Fig. 4.6 Plots of factor scores and measures of diversity for the 167 La Trinchera section.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Fig. 4.7 Plots of factor scores and measures of diversity for the 167 Fondo Negro section.

Fig. 4.8 Plots of factor scores and measures of diversity for the 168 Cerros de los Quemadillos section.

Fig. 4.9 Plots of factor scores and measures of diversity for the 168 Quita Coraza section.

Fig. 4.10 Plots of factor scores and measures of diversity for the 169 San Juan area section.

Fig. 4.11 Plots of factor scores and measures of diversity for the 169 Rfo Via section.

Fig. 4.12 Dendrogram resulting from a Q-mode cluster analysis using 179 Ward's Minimum Variance method.

Fig. 4.13 Plot of the number of clusters against semi-partial R-squared 180 from our cluster analysis.

Fig. 5.1 Map of the sudy area, with important sampling localities. 230 indicated

Fig. 5.2 Bathymetric curves for the Azua Basin Neogene 234 sedimentary sequence.

Fig. 5.3 Diagram of paleoenvironmental migration through the 238 Miocene and Pliocene.

Fig. 6.1 Location of the study area, southwestern Dominican Republic. 247

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF PLATES

Plate 2.1 60

Plate 2.2 62

Plate 2.3 64

Plate 4.1 208

Plate 4.2 210

Plate 4.3 212

Plate 4.4 214

Plate 4.5 216

Plate 4.6 218

Plate 4.7 220

Plate 4.8 222

Plate 4.9 224

Plate 6.1 285

Plate 6.2 287

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT

The Azua Basin sequence is a 2500 m thick Miocene Pliocene regressive interval. Limestones and marls of the Sombrerito Formation, the lowermost unit, ranges from lower Miocene to lowermost upper Miocene. The turbidite sequence of the Trinchera Formation spans an interval from uppermost middle Miocene to lower Pliocene. Blue- green, neritic lower Pliocene siltstones of the Quita Coraza Formation overlie the Trinchera in the seaward part of the basin. Shallow-marine strata in the lower part of the Arroyo Blanco Formation range from uppermost Miocene to middle Pliocene. Principal Components Analysis of rich benthic foraminiferal faunas aided in the recognition of species associations. Positive loadings on Factor 1 define a bathyal-neritic boundary zone assemblage: Bolivina minima (0.88), Cassidulina norcrossi var. australis (0.73), and GvToidina regularis (0.71). Lower bathyal species Pleurostomella altemans (-0.64), Bolivina paula (-0.62), and Cibicides wuellerstorfi (-0.49) show strong negative loadings. Positive loadings on Factor 2 define a middle to upper bathyal assemblage: Oridorsalis umbonatus (0.68), Hoeglundina elegans (0.57), and Uvigerina peregrina (0.51). Factor 3 represents a middle to outer neritic assemblage that includes Angulogerina jamaicensis (0.83), Cassidulina carinata (0.54), and Cibicidoides pachvderma forma sublittoralis (0.51). Factor 4 has heavy loadings on inner neritic species including Havnesina depressula (0.74), and Buliminella elegantissima (0.73). Neritic species associated with Factor 5 include Cancris sagra (0.69) and Bolivina lowmani (0.59). Plots of the factor scores in the stratigraphic sections demonstrate shoaling upward from lower bathyal to inner neritic depths. Cluster analysis reveals seven major sample groupings that correspond almost directly to the faunal zones identified in the Azua Basin by Bermudez (1949).

Migration of foraminiferal environments toward the Caribbean during the Miocene and Pliocene is paralleled by time-transgression of lithofacies.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The southwestern Dominican Republic evolved in two stages: 1) a technically quiet open ocean stage before the late Miocene; 2) a subsequent tectonically-active, laterally- constrained clastic basin stage. These events are interpreted to represent rapid filling of a thrust-block bounded "ramp valley" basin by sediments derived from the uplift of the nearby Cordillera Central, coincident with activation of the Hispaniola restraining bend in the late Miocene.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTEKJ.

INTRODUCTION

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INTRODUCTION AND OBJECTIVES

This dissertation focuses on the foraminiferal faunas and stratigraphy of the Neogene strata of the southwestern Dominican Republic (Fig. 1.1). Specifically, the objective of the study was to integrate planktonic foraminiferal biostratigraphy with benthonic foraminiferal and sedimentary facies in order to trace the evolution of the Azua Basin, an elongate sedimentary trough extending from the Caribbean coast northwestward toward the Haitian border (Fig. 1.2). Hispaniola lies along the Northern Caribbean Plate Boundary Zone (PBZ), a location that makes the study of its geology critical to interpretations of the movement of the Caribbean Plate during the Neogene (Fig. 1.3). Southern Hispaniola is especially important because of the added influence of activity along the Beata Ridge and the Muertos Trough. Study of the evolution of the sedimentary basins is a key to understanding the nature and timing of the tectonic events caused by plate movements. Up to the present time, the evolution of basins in the southwestern Dominican Republic has been poorly understood, mainly because of confusion over stratigraphy. Basically, the Neogene units of the Azua Basin were lain down as a regressive sequence and are now exposed in two regions: the northwestern arm of the basin covers the upper Rio Yaque del Sur Valley and the San Juan Valley; the lower Rio Yaque del Sur Valley and the Azua area comprise the seaward end of the basin. Local facies changes and physiographic boundaries have caused difficulties in geologic interpretation, especially between the northwestern and coastal regions. The Dominican Republic is well known among paleontologists for its excellent fossil localities. Although the most famous of these are in the Cibao Valley in the north, much of the deep water strata in the southwest also contain fine foraminiferal faunas. The classic work of Bermudez (1949) includes descriptions of over 700 species of smaller foraminifera from the Dominican Republic, many of which may be found in the Neogene

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ° ° 69 69 m ile* SANTO DOMINGO REPUBLIC DOMINICAN Azua San Juan HAITI PORT-AU-PRINCE Figure 1.1 - Location of the dissertation field area on the island of Hispaniola. of island the on area field dissertation the of Location - 1.1 Figure ' ' 18 20 ** -

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. r oNo' r Baruhona Ttmayo 's/r/z de f-wlln de lit Mills lit Mills rpbogi! *•0 Du*ctf{ Vs'/v/* §M § Jim a n i the area of this study, the Azua Basin (A) and the neighboring Enriquillo Basin (E). Basin Enriquillo inset showing (see on Figure Republic 1), Figure - Dominican Mapthe of1.2 southwest neighboring the and (A) Basin Azua the study, this of area the

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of the southwestern part of the country. This and other important works done on Tertiary fossil foraminifera of the Caribbean region between 1930 and 1960 were primarily of a taxonomic nature. Since that period, numerical techniques and data from ecological studies of modem foraminifera have become available as tools to analyze the paleoenvironmental significance of fossil faunas. Taxonomic concepts have also changed since the middle part of the century. Three specific objectives were set for this study. First, and most important, detailed examination of the foraminiferal species was planned in order to substantially improve the overall knowledge of Neogene foraminifera of the Caribbean. Problems of stratigraphic correlation among the two major basins were targeted as a second goal; a lack of biostratigraphic and lithostratagraphic control has historically plagued geologic studies of southern Hispaniola. The third objective was a comprehensive analysis of the evolution of the Azua Basin and its relationship to neighboring areas; an understanding of basin evolution in southern Hispaniola should yield insights into the movements of the Caribbean Plate during the Neogene.

GEOLOGIC SETTING

The island of Hispaniola is the second largest of the Greater Antilles, situated between Cuba and Puerto Rico on the northern edge of the Caribbean Sea. The Dominican Republic comprises the eastern two-thirds of the island while the Republic of Haiti makes up the western one-third. The terrain of these countries is marked by alternating flat valleys and high rugged mountains that strike west-northwesterly across the island. The backbone of the island is the Cordillera Central (and its Haitian extension, the Massif du Nord), which is composed of a belt of pre-Middle Albian greenschist metamorphic rocks intruded by Cretaceous to Eocene tonalite bodies (Fig. 1.4). Much of the Cordillera is over 1,000

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. South Sa/nana s — Day FZ " t tt r o t anPoll ) " t tt r o t anPoll B onao FZ B eaia F2 /(— /%«••#• G o n a r r 'Ho/a- to Enriquillo-Plantain Gardan FZ C onoi 0* Figure 1.4 - Structural features on the island of Hispaniola (modified from Weyl, 1950) Weyl, from (modified Hispaniola of island the on features Structural - 1.4 Figure Hohtn in Mtltrn SO Mdomettr SO

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meters in elevation and reaches 3,175 meters at Pico Duarte, the highest point in the Caribbean. Lower Tertiary limestones and minor volcanics are exposed at the cores of smaller mountain ranges on the south side of the island, such as the Sierra de Neiba. Later Tertiary sediments are found on the flanks of the mountain ranges and Pliocene-Quaternary sediments cover valley floors and the coastline. Mann et al. (1984) have proposed that most of the mountainous areas were formed as a result of crustal shortening caused by left-lateral, east-west movement along the Northern Caribbean PBZ acting obliquely on pre-Lale Eocene island arc structures. Anticlinal blocks composed of Cretaceous rocks and lower Tertiary strata are thrust over younger synclinal sedimentory sequences that fill the valleys. A predominantly clastic, Miocene to Pliocene sedimentary sequence crops out along the flanks of the Azua Basin, shallowing from pelagic, deep basinal deposits in the lower part of the sequence to fluvial deposits towards the top. In the northwestern part of the basin, these strata are overthrust by the limestones of the Sierra de Neiba to the south and by Cretaceous to Early Miocene units of the Cordillera Central to the north. Similar strata in the Azua area in the eastern part of the basin are overthrust on the northern edge predominantly by Eocene limestones that comprise the Sierra de Ocoa and the southern Cordillera Central; those to the south in the lower Rio Yaque Valley dip off the flanks of the Sierra de Martin Garcia anticline, at the core of which Paleocene to Oligocene limestones are exposed.

STRATIGRAPHY

Previous studies of the stratigraphy of the Azua Basin have suffered from inconsistent use of stratigraphic names. Ages of these units have been debated, due both to lateral migration of facies and use of outdated biostratigraphic criteria. On the basis of the present study, it is suggested that four Neogene sedimentary formations be recognized: the

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Sombrerito Formation, the Trinchera Formation, the Quita Coraza Formation, and the Arroyo Blanco Formation (Fig. 1.5). The ages used in this section are from my own biostratigraphic data. Stratigraphic descriptions made during my own field studies supplement those of Bermudez (1949), Bold (1975), Bowin (1975), Breuner (1985), Butterlin (1956), Butterlin (1960), Butterlin, Ramirez and Hoffstetter (1960), and Cooper (1983). The characters of the main stratigraphic units are summarized below:

Sombrerito Formation-(01sson, 1942 in Bermudez, 1949) Type Locality: Arroyo Sombrerito on east flank of the Sierra de Neiba Composition: Thin to thick beds of buff to gray, chalky to crystalline, commonly pelagic, limestone and marl. In places, calcarenites containing larger, reefal foraminifera may be interbedded with the marls, likely deposited as sediment gravity flows. An upper member, the Gajo Largo, is present, with interbedded pink calcaienites and tar mals. Stratigraphic relationships: The lower contact is not commonly evident in the field. The upper boundary may be a conformable gradation into the Trinchera Formation or may be in fault contact with the lower Trinchera Formation (as is possible at Canoa Dome). Thickness: Not certain because the base of the formation is not commonly identified; estimated as over 800 m by Osiris de Leon (1978). Biostratigraphy: Lower Miocene (N7) near San Juan to middle Miocene (N12) at Canoa; Gajo Largo Member from upper middle Miocene (N14) to lowermost upper Miocene (lower N16).

Trinchera Formation-(Dohm, 1942 in Bermudez, 1949) Type Locality: Trinchera Bluffs on the east bank of the Rio Yaque del Sur.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. alluvium Recent-Pleistocene Las Matas — — C L V ia Arroyo Seco*”^-^ .. LU upper LU Arroyo CJ Blanco o_ lo w er Quita Coraza

Trinchera upper

Florentino Ls, 2.

LU LU u m iddle

Som brerito

ower

Figure 1.5 - Stratigraphic units recognized in the Azua Basin.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Composition: Characterized by a prograding sequence of interbedded mudstones and turbidite sandstones. In the lower part of the formation, as exposed at the type locality, sandstone beds are thin and rare; most of the sediment is blue-green, or tan where weathered, planktonic foraminiferarich marl to calcareous mudstone. In the middle part, the mudstones are interbedded with immature, lithic-rich sandstones beds that are several-centdmeter thick and have sole marks, including flute casts. In the upper part of the formation, seen at Fondo Negro and Los Bancos, deposits of up to one meter thick of dirty lithic-rich sandstones, pebbly sandstones and pebble to cobble conglomerates with scoured bottoms are interbedded with fine-grained sandstones and siltstones. By definition in Bermudez (1949), this formation was composed of four zones, based primarily on foraminiferal faunas: basal Trinchera, Gaspar, Bao and Quita Coraza. The basal Trinchera zone generally corresponds with the lower Trinchera discussed here while the Gaspar Zone generally corresponds with the middle and upper Trinchera. The Bao and Quita Coraza blue mudstones are now seperated as the Quita Coraza Formation. Stratigraphic Relationships: It overlies the Sombrerito Formation, conformably or by fault contact. It grades conformably into the overlying Quita Coraza Formation in the

southeastern part of the Azua Basin ( lo w e r R j 0 Yaque valley, Azua Coastal Foothills) or into the Arroyo Blanco Formation further northwest (upper Rfo Yaque del Sur valley, Rfo San Juan valley). Thickness: Approximately 2500m in the Fondo Negro Region Biostratigraphy: uppermost middle Miocene (N15) or lowermost upper Miocene (lower N16) at Arroyo Salado to lower Pliocene (N18-19) at Fondo Negro.

Florentino Limestone - (Olsson, 1942, in Bermudez, 1949, p. 27)

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Type Locality: Along Arroyo Florentino (Arroyo de la Guardia Vieja) in the upper Rio Yaque del Sur valley, near Yayas de Viajama. Composition: Massive reefal limestone (coralline framestone) horizon that forms the tops of a series of small hills in a small area near the type locality. Previously assumed to be an autochthonous reef formed after a shallowing event. However, evidence from our field studiues suggests it is an allochthonous unit that slid from the steep shelf-edge down to muddy, lower bathyl depths, and should only be considered a facies of the Trinchera Formation. Stratigraphic Relationships: Overlies lower bathyl mudstones of the Trinchera with an irregular, scoured contact. Nature of upper contact yet unknown, since it forms hilltops, but likely conformable; it lies in the lower part of the Trinchera Formation which nearby grades upward uninterrupted into the Upper Trinchera. Thickness: Approximately 15 meters. Biostratigraphy: Upper Miocene

Quita Coraza Shale-(Quita Coraza Zone of Bermudez, 1949) Type Locality: At the village of Quita Coraza on the Rio Yaque del Sur. Composition: Blue mudstone and siltstone with uncommon thin sandstone beds. The fine material is fairly massive with little bedding evident Also included in this unit are the blue mudstones of the "Bao Zone" found at its type locality two kilometers east of Quita Coraza at Arroyo del Bao, but there may be some environmental differences reflected in the foraminiferal faunas. Stratigraphic Relationships: Conformably overlies the Trinchera Formation and is conformably overlain by the Arroyo Blanco Formation. Thickness: Less than 200 meters east of Quita Coraza to over 500 meters near Fondo Negro.

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Biostratigraphy: Lower Pliocene (N18-19)

Anroyo Blanco Formation-(Dohm, 1942 in Bermudez, 1949, p.33) Type Locality: Described by Dohm along the "Arroyo Blanco" east of Quita Coraza; this appears to be the arroyo now mapped as Canada de la Hicotea; the Arroyo Blanco on present topographic sheets is about 2 km to the west and only cuts through the Trinchera and Quita Coraza Formations. New type section is proposed for along Arroyo Las Lajas, 3 km east. Composition: Shallow water, often trough cross-bedded, sandstone with sandy clay, coralline limestone and conglomerate in the lower part of the formation grading up to marginal marine deposits of red sandstone, mudstone and gypsum beds. A deeper water Higuerito Member is reported from just west of Azua. Stratigraphic relationships: It conformably overlies the Quita Coraza Formation in the lower Rio Yaque valley and Azua Coastal Foothills and overlies the Trinchera Formation in the upper Rio Yaque and San Juan Valleys. The boundary is often set as the first autochthonous coral unit. It grades upward into the marginal marine to non-marine Arroyo Seco Formation. Thickness: Approximately 500 meters Biostratigraphy: Upper Miocene Rfo San Juan Valley to Pliocene in the coastal areas.

PALEONTOLOGY

Hispaniola is includes one of the better known Cenozoic invertebrate fossil collecting regions in the Western Hemisphere, the Cibao Valley of the northern Dominican Republic. The strata of the southern side of the island are not as spectacularly fossiliferous as those of

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. the northern part, but contain fine foraminiferal faunas that represent a wide variety of environments, from pelagic to lagoonal. Many of the over 700 species of smaller foraminifera described in the exhaustive work of Bermudez (1949), "Tertiary Smaller Foraminifera of the Dominican Republic", were recovered from samples collected in the southwestern part of the country. During the period from 1935 to 1955, other notable Cenozoic foraminiferal investigations were conducted around the Caribbean region: among these are Coryell and Rivero (1940) in Haiti; Cushman and Jarvis (1930) from Buff Bay, Jamaica; Cushman and Stainforth (1945) in Trinidad; Cushman and Todd (1945) from Buff Bay, Jamaica; Hedberg (1937) in northeastern Venezuela; D.K. Palmer (1945) from the Bowden of Jamaica; Renz (1948) in Falcon, Venezuela; and Redmond (1953) in northern Colombia. These investigations focused primarily on taxonomy, with some of the more intensive works (notably Bermudez, 1949, and Renz, 1948) attempting to use faunal distributions as a basis for correlation and environmental interpretation. With the advances in our knowledge of the biostratigraphic and paleoenvironmental signifigance of foraminifera developed since that period, there is great potential for deriving significant new information from the Azua Basin. Since the early studies by Blow (1959) and Bolli (1957) of the planktonic foraminiferal faunas of the southern Caribbean region and Indonesia, zonation schemes based on these forms have become increasingly useful. Planktonic foraminifera evolve rapidly and are widely distributed due to their mode of life, making them ideal biostratigraphic tools. The zonation schemes have undergone continual refinement through the 1960's and 1970's and have been vast improvements over the benthic foraminiferal zonation schemes of earlier studies. Advances in paleoenvironmental applications have followed numerous detailed studies of foraminiferal distributions in modem oceans and the development of numerical techniques to analyze abundance data A number of numerical techniques have been proven

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useful in investigations cf foraminiferal faunas: measurements of diversity (including simple species richness and the Shannon-Wiener information function); factor analysis, which allows interpretation of data set variances by the number of factors or species groups present; and cluster analysis, which establishes sample groups based on faunal similarities.

SEDIMENTOLO GY

The sedimentology of the Neogene strata of the southwest Dominican Republic has received only cursory attention in most geologic studies of the area .A fundamental understanding of sedimentation patterns and sedimentary petrology will aid in the resolution of questions of stratigraphic correlation, tectonic activity and depositional history in the area. In this study, the lithofacies present in the Azua Basin are evaluated through comparison to several models for deep-water and shallow-water sedimentation, including Mutti and Ricci Lucchi (1972), Walker (1984), and Selley (1970). We also evaluate the petrology of the sandstones as a source of data about the depositional history of the Azua Basin.Textural characteristics of the sandstones offer insights into their environment of deposition while mineralogical content has implications for both provenance and tectonics (Dickinson and Suczek, 1979).

TECTONICS

Hispaniola is situated along the Northern Caribbean Plate Boundary Zone (NCPBZ) and has been the focus of a number of tectonics-related studies (i.e. Biju-Duval et al., 1983; Ladd and Watkins, 1978; Lewis, 1982; Mann and Burke, 1984; Mann et al., 1984; Nemec, 1982).It has been proposed that the geologic evolution of the island has taken place

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in two phases: a pre-Middle Eocene island-arc phase and a later Cenozoic strike-slip phase. During the island-arc phase, the median metamorphic belt of the island was formed and volcanics, volcaniclastic sediments and limestones were deposited above it. As the stress regime of the Caribbean shifted from northeast-southwest to east-west oriented compression, subduction ceased along the Greater Antilles and began along the Lesser Antilles to the east. Transpressional motion, that is, a combination of transcurrent movement and compressional thrusting, was initiated along west- northwesterly oriented faults (Fig. 4) due to the action of east-west, left-lateral relative motion along the Northern Caribbean PBZ acting on west-northwesterly oriented, pre-Late Eocene island arc structures. As a result, thrust fault bounded montain ranges were uplifted and detritus eroded from them into adjacent basins such as the Azua Basin. Some oblique subduction presently takes place off of the northeast coast of the island in the Puerto Rico Trench (Mann, Burke and Matsumoto, 1984), but activity off of the southern coast at the Muertos Trough is less certain. The Muertos Trough (Fig. 3) extends along the southern margin of the island from the edge of the Barahona Peninsula in the west to Puerto Rico to the east. It has been suggested as a site of subduction on the basis of the morphology of the trough as seen in seismic profiles (Nemec, 1982; Biju-Duval et al. 1983; Ladd and Watkins, 1978). These indicate a listric-faulted subduction complex facing the Caribbean, underlain by the B" layer of the Caribbean floor. Just landward is the San Pedro Basin, a submarine basin with significant sediment accumulations; this is thought to resemble known fore-arc basins. Unfortunately, any conclusive evidence of seismicity or volcanic activity normally associated with subduction is yet to be found. Alternative explanations include the suggestion that it may currently be an inactive subduction zone or that it is an "incipient subduction zone", a region of compression where the deeper crustal levels behave

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plastically while the shallower ones remain brittle, forming a listric faulted complex similar in appearance to (and perhaps an earlier genetic stage of) a true subduction complex. Biju-Duval et al. (1983) noted similarities between the marine complex at the Muertos Trough and the land sections of the southwestern Dominican Republic. They cite a correlation between landward dipping reflectors on offshore seismic profiles and northeastward dipping thrust zones evident in the field (although they fail to mention corresponding southwesterly dipping thrusts on the other side of the mountain chains). Their observations lead them to suggest that the Paleogene strata of the Sierra de Ocoa and the Neogene strata of the Sierra de Neiba represent the landward extension of the accretionary complex and that the San Cristobal Basin (east of the Azua Area) is the landward continuation of the offshore San Pedro "Forearc" Basin. The Azua Basin is vaguely described by these authors as restricted Neogene- Quaternary depositional troughs that developed "immediately north of the pelagic terrain" presently exposed in southernmost Hispaniola. The land section is proposed to have been uplifted by the collision of the Beata Ridge with the rest of Hispaniola at the Muertos Trough subduction zone.lt is obvious that the Muertos Trough has had some significant influence on the geology of southern Hispaniola, but many of the suggestions and conclusions of Biju-Duval et al. are speculative. The Beata Ridge (Fig. 3) may have had an important role in shaping the geology of Hispaniola but the specifics of that role are unclear. The Beata Fault Zone (Fig. 4) projects landward from the fault scarps on the east side of the ridge. It truncates the Bahoruco Mountains along the east coast of the Barahona Peninsula and extends onto the island through the Loma El Numero, Sierra de Ocoa, Cordillera Central and easternmost Azua Basin. Activity along this zone may have affected a number of geologic features in southern Hispaniola: the post-Middle Miocene uplift of the Sierra de Martin Garcia, the uplift of the highest parts of the Cordillera Central (they lie along the strike of the fault), and the

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bending of the Hispaniola Fault Zone at its intersection with the trace of the Beata Fault Zone. Roemer, Bryant and Falquist (1978) identified three periods of differential uplift on the ridge. The earliest came in the Late Cretaceous or Early Tertiary when most of the faulting on the steep eastern side took place. The second phase occurred in the Miocene, uplifting the ridge 1,000 meters as faulting continued on the steep eastern side and new fault scarps developed on the stepped western margin. Following a period of subsidence in the Pliocene, the latest episode of uplift, of later Pliocene and Pleistocene age, affected mainly the southern and southeastern flanks. Exactly how these uplift events are reflected in the geology of Hispaniola is yet to be determined.

ARRANGEMENT OF PAPERS

Five papers which address the objectives set earlier in the chapter are included in this dissertation. The first paper, Chapter 2, establishes a biostratigraphic framework for the Azua Basin using planktonic foraminifera. This framework lays the foundation for the following paper, Chapter 3, on the evolution of the Azua Basin.Ranges of benthic foraminiferal species in the Azua Basin sequence are reported and combined with lithofacies analysis to reconstruct the environments of deposition; sandstone petrography and paleocurrent indicators are used to determine provenance. Putting this data within the biostratigraphic framework, a model for latest middle Miocene development of the Azua Basin is proposed and its tectonic implications discussed. Chapters 4 and 5 relate to detailed analyses of the benthic foraminiferal faunas in the context of their environmental significance. Chapter 4 deals with the entire assemblage. Paleoenvironments are analyzed by using Principal Components Analysis (PCA) of species percentage data to establish species associations; Cluster Analysis (CA) is used to

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determine patterns of sample groupings. Finally, the Azua Basin faunal assemblages are compared to those of other Caribbean areas. In Chapter 5, the migration of faunal zones in the Azua Basin during the Miocene and Pliocene is traced through the occurences of selected, bathymetrically signifigant benthic foraminiferal species. The usefulness of most existing reports on circum-Caribbean Tertiary foraminifera, including that of Bermudez (1949), is limited by taxonomic problems. There is a proliferation of unnecessary species names, and little attempt has been made so far to compare fossil and Recent assemblages. In Chapter 6, an attempt is made to update and supplement the taxonomic information in Bermudez (1949), and place in synonomy a number of Recent and fossil species, on the basis specimens from the Azua Basin. A list of species identified is supplied in Appendix 1 and the numerical data on benthic foraminiferal species abundances ate given in Appendix 2.

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BIBLIOGRAPHY

Bermudez, P.J., 1949, Tertiary Smaller Foraminifera of the Dominican Republic: Cushman Laboratory for Foraminiferal Research Special Publication 25, p. 1-322.

Biju-Duval, B.,G. Bizon, A.Mascle and C.Mueller, 1982, Active margin processes: Field observations in southern Hispaniola: American Association of Petroleum Geologists Memoir 34, p. 325-344.

Blow, W.H., 1959b. Age, Correllation and Biostratigraphy of the Upper Tocuyo (San Lorenzo) and Pozon Formations, Eastern Falcon, Venezuela: Bulletins of American Paleontology v. 39, pt. 178, p. 59-251.

Bold, W.A. van den, 1975, Neogene Biostratigraphy (Ostracoda) of southern Hispaniola: Bulletins of American Paleontology v. 66, no. 286, p. 549-639.

Bolli, H.M., 1957, Planktonic Foraminifera From the Oligocene- Miocene Cipero and Lengua Formations of Trinidad, B.W.I.: U.S. National Museum Bulletin v. 215, p. 155-172

Bowin, C., 1975, The Geology of Hispaniola in The Ocean Basins and Margins 3, A. Naim and F.G. Stehli, eds.: Plenum, New York.

Breuner, T.A., 1985, The Geology of the Eastern Sierra de Neiba, Dominican Republic: Unpublished M.S. Thesis, George Washington University.

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Butterlin, J., 1956, La constitution geologique et la structure des Antilles: Centre National de Recherche Scientifique, 453p.

Butterlin, J., 1960, Geologie generale et regionale de la Republique d'Haiti: Inst. Hautes Etudes de L'Amerique Latine, Traveaux et Memoiies VI. Universite de Paris, 194p., 18 pis., 17 text figs., 13 tables.

Butterlin, J., Ramirez, R., and Hoffstetter, R., 1960, Be d'Haiti (Hispaniola) et iles adjacentes, Republica Dominicana avec une carte: Lexique Stratigraphique International, v.5., Amerique Latine, fasc. 2b, Antilles: 253-411.

Cooper, J.C., 1983, Geology of the Fondo Negro Region, Dominican Republic: Unpublished M.S. Thesis, State Univ. N.Y. at Albany: 125p.

Coryell, H.N., and Rivero, F.C., 1940. A Miocene Microfauna from Haiti: Journal of Paleontology, v. 14, p. 324-344

Cushman, J.A., and Stainforth, R.M., 1945, The foraminifera of the Cipero Marl of Trinidad, British West Indies: Cushman Laboratory for Foraminiferal Research Special Publication 14,75 p., 16 pi..

Cushman, J.A., and Todd, R., 1945, Miocene foraminifera from Buff Bay, Jamaica: Cushman Laboratory for Foraminiferal Research Special Publication 15,73p..

Dickinson, W.A. and Suczek, C.A., 1979, Plate tectonics and sandstone compositions: American Association of Petroleum Geologists Bulletin, v. 63, p. 2-31.

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Hedberg, H.D., 1937, Foraminifera of the middle Tertiary Carapita Formation of northeastern Venezuela: Journal of Paleontology, v. 11, no. 8, p. 661-697, fig. 1, tabs. 1, 2, pis. 90-92.

Ladd, J.W. and Watkins, J.S., 1978. Tectonic development of trench-arc complexes on the northern and southern margins of the Venezuela Basin in J.S. Watkins, L. Montadert and P.W. Dickerson, eds., Geological and geophysical investigations of continental margins: American Association of Petroleum Geologists Memoir 29, p. 363-371

Lewis, J.F, 1982. Cenozoic tectonic evolution and sedimentation in Hispaniola: Transactions, 9th Caribbean Geological Conference (Santo Domingo), p. 191-198.

Mann, P., Burke, K., and Matsumoto, T., 1984, Neotectonics of Hispaniola: plate motion, sedimentation and seismicity at a restraining bend: Earth and Planetary Science Letters v. 70, p. 311- 324.

Mann, P. and Burke, K., 1984, Neotectonics of the Caribbean. Review of Geophysics and Space Physics v. 22, no. 4, 309-362.

Mutti, E., and Ricci Lucchi, F., 1972. Le torbiditi dell’ Appenino settentrionale: introduzione all' analisi di facies: Memoiri, Societi Geologico di Italia v. 11, p. 161- 199 (Translation by T.H. Nilsen, 1978, Turbidites of the northern Appenines: introduction to facies analysis: International Geology Review, v. 20, p. 125-166).

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Nemec, R.C., 1982, A two phase model for the tectonic evolution of the Caribbean: Transactions of the 9th Geological Conference (Santo Domingo), v. 1, p. 23-34.

Palmer, D.K., 1945, Notes on the foraminifera from Bowden, Jamaica: Bulletins of American Paleontology, v. 29, no. 115, p. 5-82.

Redmond, C.D., 1953, Miocene foraminifera of the Tubara beds of northern Colombia: Journal of Paleontology, v. 27, no. 5, p. 708-733.

Renz, H.H., 1948, Stratigraphy and fauna of the Agua Salada Group, State of Falcon, Venezuela: Geological Society of America Memoir 32, p. 1-219.

Roemer, G., Bryant, A., and Falquist, B., 1976. A geophysical investigation of the Beata Ridge: Trans 7th Caribbean Geological Conference, p. 115-125.

Selley, R.C., 1970. Ancient sedimentary environments (2nd ed.): Ithaca, Cornell University Press.

Walker, R.G., 1984. Turbidites and associated coarse clastic deposits in Walker, R.G., ed., Facies Models: Geoscience Canada, Reprint series 1, p. 171-188.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER 2

NEOGENE PLANKTONIC FORAMINIFERAL BIOSTRATIGRAPHY OF THE SOUTHWESTERN DOMINICAN REPUBLIC

(submitted to Journal of Foraminiferal Research)

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ABSTRACT

The Azua Basin of the southwestern Dominican Republic contains a thick (as much as 4000 m or more) Neogene marine sedimentary sequence that is here, for the first time, zoned in detail using planktonic foraminifera. Thirty-five species have been identified and are figured in this report. Age determinations (early Miocene to early or middle Pliocene) are younger than assumed in previous geologic studies and demonstrate a southeastward time-transgression of stratigraphic units. The lower part of the sequence reflects a change from a deep carbonate basin setting, represented by the Sombrerito Formation, to a prograding turbidite regime, represented by the Trinchera Formation. The Sombrerito ranges in age from early Miocene (stratigraphic level: Globigerinatella insueta chronozone) to middle Miocene (Globorotalia fohsi robusta chronozone). The Gajo Largo Member of the Sombrerito is dated as late middle to earliest late Miocene (Globorotalia maveri chronozone to lower Globorotalia acostaensis chronozone). The Trinchera spans an interval from near the middle - late Miocene boundary (equivalent of Globorotalia menardii zone or Globorotalia acostaensis zonel to the early Pliocene (Globorotalia margaritae zone). The upper part of the sequence reflects a transition from shallow-marine to lagoonal paleoenvironments and contains planktonic foraminiferal faunas of variable richness. Blue- green siltstones of the Quita Coraza Formation overlie the Trinchera in the southern and eastern parts of the basin and contains faunas that generally indicate an early Pliocene age (Globorotalia margaritae chronozone). The lower part of the Arroyo Blanco Formation contains relatively poor planktonic foraminiferal faunas of latest Miocene (upper Globorotalia humerosa chronozone) to early or middle Pliocene age (Globorotalia margaritae or Globorotalia miocenica chronozone).

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Re-evaluation of earlier Caribbean region planktonic foraminiferal studies permits correlation of the Azua Basin strata to nine other Neogene stratigraphic sequences. Greater resolution in such regional stratigraphic correlation permits insights into its geologic

evolution.

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INTRODUCTION

The island of Hispaniola lies in the Greater Antilles along the northern boundary of the Caribbean Plate. A partially continuous sedimentary sequence in the Azua Basin of the southwestern Dominican Republic offers some insights into tectonic activity along this plate boundary zone during the Neogene. The proximity of two enigmatic Caribbean structural features, the Muertos Trough and the Beata Ridge (Fig. 2.1), complicate the history of the southern part of the island. Several alternative explanations have been offered for the tectonic evolution of this area. One suggestion is that conveigent-margin tectonics in the Muertos Trough are the most important influence (Biju-Duval and others, 1982). An alternative explanation is that wrench-fault activity along the Northern Caribbean Plate Boundary Zone (PBZ) has been the primary mechanism (Mann and others, 1984). Detailed biostratigraphic data should offer some of the age constraints needed to resolve tectonic modelling. No major studies of the foraminifera of the Dominican Republic have been published since the exhaustive work of PJ. Bermudez in 1949. Although several planktonic foraminiferal species first described in that volume are of interest to biostratigraphers today (i.e. Globorotalia lobata and Globorotalia cibaoensisl. the faunas deserve a complete examination in light of the developments in planktonic foraminiferal biostratigraphy over

the past 40 years. The main objective of this study is to examine the planktonic foraminifera of the Azua Basin in the southwestern Dominican Republic and to provide a precise biochronology for the stratigraphic units. The basin is a Neogene sedimentary trough that extends from the western Dominican Republic southeastward to Neiba Bay, widening towards its junction with the Caribbean. Up to 4,000 m of Neogene marine strata are well exposed on its flanks. Overall, an upward shallowing trend is evident, from pelagic deposits through a

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■st

so CO,

v(N O (S t ' *

r c c « 2 = CO

Figure 2.1 - Map of the study area, southwestern Dominican Republic. The northwesterly trending Azua Basin is bounded on the northeast by the Cordillera Central and on the southwest by the Sierra de Neiba, opening up towards the Ocoa Bay where it meets the Sierra de Martin Garcia. Sample localities are denoted by triangles and basin boundaries by dashed lines. Boxed areas of concentrated sampling are enlarged in subsequent figures (Figs. 2-4).

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thick turbidite succession into shallow marine elastics. Cretaceous and lower Tertiary rocks of the Cordillera Central overthrust the Neogene sequence on the northeastern flank of the basin, whereas lower Tertiary limestones of the Sierra de Neiba and the Sierra de Martin Garcia thrust over much of the southwestern flank. A Caribbean-region stratigraphic correlation scheme is also proposed in this study based on re-evaluation of earlier planktonic foraminiferal studies in Hispaniola, Jamaica, St. Croix, Trinidad, and Venezuela.

METHODS AND MATERIALS

One hundred seventy-seven samples were collected in January, 1985, and January, 1986, from outcrops and roadcuts around the Azua Basin. Much of the sampling was conducted in "airoyos" (small stream valleys) branching off the Rio Yaque del Sur. Other samples were taken from roadcuts along the Azua-Barahona ffighway, from the Rio Via near Azua, from several tributaries of the Rio San Juan, and from the foothills of the Sierra de Martin Garcia (refer to Figs. 2.1-2.4 for sample locations). The largest number of samples was collected from the Trinchera Formation. Others were collected from the Sombrerito, Quita Coraza, and Arroyo Blanco formations. The samples were disaggregated by boiling in Quatemary-O solution and followed by washing through a 63 |im sieve. Eighty-two samples yielded usable planktonic

foraminiferal faunas. The relative abundances of the species in each sample were estimated from counts of 50 specimens and evaluated by the following criteria: rare = less than one percent; common = one to five percent; frequent = five to twenty percent; abundant = greater than twenty percent. The biostratigraphic zonation scheme of Bolli and Saunders (1985) is generally followed in this study, with additional information from Kennett and Srinivasan (1983; Fig. 2.5).

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z < g

O'. O € O'< '*•J

Figure 2.2 - Map of the lower Rio Yaque del Sur Valley area. Best exposures of the Neogene strata are in the low hills bordering the river. The margins of the Sierra de Martin Garcia tend to be obscured by alluvium. Sample localities are denoted by triangles and formational boundaries by dashed lines.

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Reservoir

Figure 2.3 - Map of the upper Rio Yaque del Sur Valley and San Juan Valley areas. Best exposures are in the low hills near the river, structure locally complicated by Quaternary and possibly late Pliocene volcanic stocks. Sample localities are marked by triangles and formational boundaries by dashed lines.

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70°47'

x A rroyo \ 24 j Blanco y v Fm. 2 1 *A22 Q Uita Coraza 9A ^ L - „ F m .

Trinchera Formation

Azua 2km

Figure 2.4 - Map of the Rio Via section, near Azua. Samples were taken from stream cuts; triangles mark localities; dashed lines indicate formational boundaries.

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epiiu eu-apuco popnuueq ciiojoicaci D ejoi'uouQ'S euiia&iSEH EJQi'uoud'Sacjfl buub Bhsch eunnmujes sisdonauipiaiaeuog cqoitiiniu sisooiiouiptcueegds eaunte'P sisooiiBuiP'OJBguos Eieqoi'Q cunnqjQ gsjBAiun guiinqiQ CuOlisuEJl gminojoOCJd ei'dsiue euupcnooqoio Iu53siyopeiwppn5oco/D eBIUPflJElll ei[ElOJOQO|n (rSUOEISOPE EIIEIOJOQOlO .0 . (iPJEueoi 8i|gi9joqoio IS iipjeuoui EiieiojOQOio MDJCU9UJ3PJ0 Ei|E10JOqO|9 BlSUBEn6uS|timos eiitqojOQoio BIIElOJOQOlQ pefciu biiei 6joqoi 9 stsnqoj rsuoi ei|eio«qoic heqoi su o i eiicioJOQoic BinsEtueudued rsuoj enEjoJoqoio tpuojojegoueq «uoi bubiojoqoiq tUltii tCpJOOpaftqCfQ joqru SBpiouusDiQOio cnmsflXB snntxiao sepiouueDiQoio cnnexiqo snn&iQo sbpio u u b Siqoio pouaeudsiq sopiouusO'Qoso puaignpqes snqoiui s bpiou ub Siqoid snqoiw sap'ouuebiqoio saqiuaaou eousSiQoin . lAjrup EouofiiqoiQ . sop»onnq puMOfaqoip BuEiomeuBA euuoBiqoio

UM OdueiQ OAOJJtf siiun omdBjDijBJis UJJI EZBJOOBlinn I I p ix ij E je q o u u i

sg 6 ubj oiMdejBi.jejjsoig jq^ o6.nri o (b q aij oiuBjqiuos

3N3DCTJ

Figure 2.5 - Chart showing ranges of species identified in this study, based primarily on B orland Saunders (1985) with additional information from Kennett and Srinivasan (1983). The N-units are the Neogene zones of Blow (1969) as positioned by Bolli and Saunders. Age ranges of stratigraphic units are based on planktonic foraminiferal content. See text and Tables 1-3 for explanation.

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LITHOSTRATIGRAPHY

The stratigraphic units of the southwestern Dominican Republic were originally described in reconnaissance studies by geologists of the Standard Oil Company of New Jersey (see Bermudez, 1949; Butterlin and others, 1956). These descriptions have since been subject to various interpretations, with ensuing confusion over the geology of the region. The stratigraphy used here is essentially that of Bold (1975 and oral comm., 1986) and Mann (Lebron and others, 1986), which allows characterization of each formation in the context of depositional systems. Stratigraphic thicknesses cited are based upon my own field mapping as well as that of Lebron and others (1986), Breuner (1985), and Cooper

(1983). Four formations are recognized in the thick marine Neogene sequence in the Azua Basin. These are, in ascending order, the Sombrerito, Trinchera, Quita Coraza, and Arroyo Blanco formations. These formations reflect the filling of a deep basin by clastic deposits in Miocene and Pliocene times.

Sombrerito Formation The Sombrerito Formation, lowermost unit of the sequence, is characterized by predominiantly pelagic, deep-marine sediments. The nature of its boundaries is not fully understood; in most places they appear to be fault contacts. The type locality of this unit is on the east flank of the Sierra de Neiba in the Arroyo Sombrerito (RD-124 to 125b; Fig. 2.1). This section is characterized by buff pelagic limestone and marl with scattered intercalated beds of shallow carbonate debris. Similar, but less marly lithologies are exposed to the south in travertine quarries in the structurally complex area at the Canoa Dome (RD-112 to 113; Fig. 2.2). To the northwest, at Rio Los Baos, the Sombrerito is characterized by blue-gray pelagic marls and rhythmically interbedded sediment gravity

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flows composed of pink to buff calcarenites of shallow marine and reefal origin (RD-126 to 127; Fig. 2.1). The Gajo Largo Member of Cooper (1983) is also included in this formation. It is an approximately 200 m-thick interval of intercalated calcareous turbidite sandstones and deep- marine marls that underlie the Trinchera terrigenous turbidite sequence northeast of Canoa (RD-114 and 115; Fig. 2.2). The unit was originally included included in the normally siliciclastic turbidites of the overlying Trinchera, but more closely resembles the underlying Sombrerito. The contact between the Gajo Largo and the Trinchera was mapped by Cooper (1983) as a high-angle strike-slip fault, which he suggested may have a thrust component.

Trinchera Formation The Trinchera Formation is characterized by a thick sequence of interbedded calcareous deep-marine mudstones and dirty turbidite sandstones. The type locality was designated as the bluffs along the Rfo Yaque del Sur at La Trinchera (Fig. 2.3). The thickest interval is in the Fondo Negro area (Fig. 2.2), where more than 2,500 m is exposed. The lower part of the formation is dominated by finer-grained sediments characteristic of lower-turbidite fan facies, with sandstones displaying extensive lateral continuity and thickening-upward sequences. (Walker, 1984; Mutti and Ricci Lucchi, 1972). The lower part of the Trinchera Formation crops out at the Trinchera bluffs (RD-2 to 4; Fig. 2.3), as well as in the lower part of the Arroyo Salado section (RD-6a to 8) and the lowest part of the Azua-Barahona highway section (RD-116; Fig. 2.2). Sandstones in the upper part of the Trinchera are more common, thicker and arranged predominantly in thinning-upward sequences. They often exhibit graded bedding, Bouma sequences, and flute casts. Toward the top of the interval, scoured bottoms and laterally discontinuous bedding are present. Matrix-supported conglomerates, large channels, and

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slump blocks occur in the uppermost strata. Overall, the upper part of the Trinchera is characteristic of more proximal middle- and upper -turbidite fan facies (Walker, 1984; Mutti and Ricci Lucchi, 1972). Intervals sampled include the upper Arroyo Salado section (RD-9 to 13; Fig. 2.3), along the Rio Yaque del Sur at Los Bancos (RD-5 and 6), the section at Arroyo Las Lajitas (RD-132 to 136), most of the section along the Azua - Barahona Highway (RD-117 to 123, RD-72 to 77; Fig. 2.2), the Arroyo El Puerto section (RD-57 to 71), the Arroyo de Bergal - Arroyo del Bao section (RD-30 to 42) and the section at Rfo Via (RD-14 to 16; Fig. 2.4). The name "Florentino Limestone" has been loosely applied to units of "shallow- marine" reefal limestone that lie in the Trinchera Formation or atop the Sombrerito Formation (Olsson, 1942 in Bermudez, 1949; Breuner, 1985; J. Rodriguez and P. Mann, oral comm., 1985). Close examination of hilltop outcrops around the type section (Arroyo de la Guardia Vieja; Fig. 2.2) reveals an abmpt, scoured basal contact with the bathyal mudstones of the underlying Trinchera (RD-128 to 131). The benthic foraminiferal fauna of these mudstones includes the deep-water species Cibicides wuellerstorfi (Schwager). This evidence indicates that these limestone units are allochthonous blocks of reef material emplaced from the shelf into a deep basin.

Quita Coraza Formation The Quita Coraza Formation is a local unit of soft, blue-gray siltstones exposed only in the southern Rfo Yaque del Sur valley and in the Azua area. The siltstones are generally massive, but occasionally contain uncommon thin sandstone beds. This unit was originally described by Bermudez (1949) as a foraminiferal faunal zone of the Trinchera Formation at the village of Quita Coraza, but herein it is considered a formation. It also includes the blue siltstones of Bermudez's "Bao Zone", described from exposures 2 km east of Quita Coraza, in Arroyo del Bao. The "Bao" strata contain slightly shallower-water foraminiferal

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assemblages than the "Quita Coraza" but are lithologically identical and thus mapped as the same unit. The Quita Coraza conformably overlies the Trinchera Formation and is conformably overlain by the Arroyo Blanco Formation. The thickness varies from less than 200 m in the type area to about 500 m near Fondo Negro. This unit was sampled along the bends in the Rio Yaque del Sur west of Fondo Negro (RD-78 to 84 and 99; Fig. 2.2), near Quita Coraza in the Arroyo del Bao (type locality for Bao Zone; RD-43 and 44; Fig. 2.2) and Arroyo de los Guiros (RD-45 to 48), and along Rfo Via near Azua (RD-17 to 22; Fig. 2.4).

Arroyo Blanco Formation The Arroyo Blanco Formation is a shallow marine clastic unit found throughout the study area. It is typified by shallow marine silts, sandstones, and conglomerates, with some coral layers in the lower part and gypsum in the upper part. It conformably overlies the Trinchera Formation in the San Juan and upper Rfo Yaque del Sur Valleys, and the Quita Coraza Formation in the lower Rfo Yaque del Sur Valley and Azua area. It is overlain by non-marine strata. The base of the Arroyo Blanco is recognized in many areas by the appearance of coral beds above the deeper marine Trinchera and Quita Coraza Formations, marking the onset of nearshore deposition. The type locality is in the Arroyo Blanco east of Quita Coraza, but there is some confusion over the exact location of that section. The lower part of this formation was studied in a number of areas, including the microfossiliferous samples plotted on the map and noted in parentheses: the San Juan Valley at Arroyo Las Lajitas (RD-137; Fig. 2.3); the lower Rio Yaque del Sur Valley at Arroyo Las Lajas (PM- 84-7; Fig. 2.1) and Arroyo de Los Guiros near Quita Coraza (RD-49; Fig. 2.2); at Arroyo Barranca across from Fondo Negro (RD-100); and in the Azua area at Rfo Vfa (RD-23 to 26; Fig. 2.4).

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PLANKTONIC FORAMINIFERAL COMPOSITION AND ZONATION

Planktonic foraminifera are present throughout the Neogene marine sequence of the southwestern Dominican Republic. They are most abundant in the lowest part of the sequence (Sombrerito Formation) and are less common in the upper part (Arroyo Blanco Formation). The planktonic foraminiferal species recovered in this study are listed in Tables 2.1 - 2.3 and are figured in Plates 2.1 - 2.3. The biostratigraphy is based on the zones of Bolli and Saunders (1985); for convenience, the numbered zones of Blow (1969) are also provided, based on the correlations provided by Bolli and Saunders (1985). The rules of the Noith American Stratigraphic Code (1983) are here followed for zone terminology. Although uncommon in studies of planktonic foraminifera, this practice, aside from standardizing nomenclature, allows differentiation of a formally defined biozone from the author's interpretation of this zone based on datum planes of other species. Where zone- defining appearances and/or disappearances of taxa are recognized, the strata are placed in the biozones of Bolli and Saunders (1985). Where the zone-defining criteria are not recognized, the strata are referred to as "equivalent to the zone"; these are also refereed to as belonging in the biochronozone of the same name, based on presence/absence of other taxa. Stratigraphic ranges of the species identified in this study (Fig. 2.5) are taken from Bolli and Saunders (1985), with the exception of three species, Globigerina bulloides d’Orbigny, G. drurvi (Akers), and Sphaeroidinellopsis disiuncta (Finlay), for which the ranges of Kennett and Srinivasan (1983) are used. Bolli and Saunders provide no ranges for the former two species and note a middle Miocene first appearance for the latter. This species co-occurs, however, with Globigerinatella insueta Cushman and Stainforth in lower Miocene samples from the Sombrerito Formation, discussed below, and from the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10 2 2 2 1 2 1 ______1 4 1 1 3 1 2 2 1 2 1 1 3 2 3 4 4 4 4 3 3 1 3 3 2 4 A. Las La|llas w 1 3 1 3 3 1 1 1 3 3 3 3 3 3 3= 3 2 ______1 1 2 2 1 1 1 1 1 2 1 1 2 B ancos =common, =common, 2 1 2 3 4 3 2 2 1 2 2 1 1 1 1 4 3 3 4 3 12 13 5 6 132133 134 135 136 137 2 1 2 2 2 3 1 1 1 1 2 3 ______1 1 4 4 1 1 Tr Tr Tr AB 1 1 3 A. Salado 1 8 9 b 10 11 2 1 2 3 4 3 2 4 4 4 4 4 1 3 3 3 2 2 2 3 2 7 2 2 3 1 1 1 3 3 2 3 3 1 4 4 4 3 3 ______3 3 ______4 3 4 3 2 2 1 1 1 2 2 1 1 1 1 3 1 2 1 1 1 1 1 1 1 4 4 4 4 3 1 1 2 1 1 2 1 1 2 3 2 3 3 3 2 21 222223322333 1 1 1 1 1 1 1 128129130131 6 2 T r T r 4 2 3 1 1 2 2 1 3 2 1 3 2 2 3 2 3 2 2 1 1 4 4 4 4 4 1 2 2 2 2 3 3 2 2 2 1 1 2 4 1 1 2 2 2 1 21111 1111111 1 4 4 3 3 3 3 3 3 3 2 22 2 1 2 125125a125b124 1 1 1 1 4 4 3 2 1 2 2 2 1 1 3 3 LosBaos A. Sombrerito Trinchera Florentine; area 1 2 6 1 2 7 S=Sombrerito Fm.; Fm.; S=Sombrerito T=Trinchera Fm.; Coraza QC=Quita Fm.; Blanco AB=Arroyo Fm. Table 2.1 - Estimated relative abundance of planktonic foraminifera in samples from the the from in samples foraminifera planktonic of relative abundance 2.1 Table - Estimated upper Rio Yaque del Sur and Juan San Valleys. See text for more details on localities. frequent, and 4=abundant. 4=abundant. and frequent, Numbers in Table 2.represent estimated relative abundances, with l=rane, with l=rane, abundances, relative estimated 2.represent Table in Numbers Candelna nlllda Orbullna bllobata Orbullna universe Globlgerina druryi Globorotalla scitula Globorotalla mayerl Globlgerlna bulloldes Globlgerlnoides ruber Globfgerinoldes mltra 2 Globorotalla menardii Globlgerina nepenthes 1 1 3 Globoquadrlna alllsplra Hastlgerina slphonifera 1 1 Clavatorella bermudezl Globlgerina venezuelana Praeorbullna transltorla Globorotalla margaritae Globlgerlnoides trllobus 4 4 4 Globoquadrlna dehlscens Globorotalla acostaensls 1 1 1 Globorotalla lenguaensts Globorotalla menardii ”B” Globorotalla praemenardll 2 Hastlgerlna praesiphonlfera 2 2 Globlgerlnoides blsphaerlcus Sphaeroldlnellopsls dlsjuncta Sphaeroldlnellopsls multiloba Sphaeroldlnellopsls semlnullna Globlgerlnoides obllquus obllquus 1 3 3 2 Globorotalla fohsl lobata-robusta Globorotalla fohsf perlpheroacuta Globorotalla fohsl perlpheroronda Globlgerlnoides obllquus extremus Globfgerinoldes trllobus saccullferus 2 2 2 1 2 2 2

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. -p*. o 4 L a|as 84 - 1 2 3 ______3 2 3 4 43 4 2 1 21 2 2 2 3 3 1 3 1 o 1 1 2 4 CM 3 R io V ia 1 2 1 2 3 2 2 1 2 2 1 1 4 4 4 2 2 1 1 1 1 1 3 3 3 2 2 4 6 14 1 6 1 9 11 4 5 2 1 1 2 4 4 4 4 4 4 4 1 1 1 3 2 1 3 3 3 2 1 2 1 2 1 1 2 1 1 2 23 1 4 1 3 2 4 1 3 3 3 4 3 111 1 1 1 1 2 ______3 2 4 4 3 1 2 2 2 1 1 4 3 1 1 1 1 1 1 1 3 2 3 2 3 2 4 3 2 3 3 32 1 2 2 3 1 1 2 3 8 3 9 4 0 41 4 2

4 3 1 1 1 1 2 2 Tr QC Tr QC AB 1 2 2 Qulla Coraza area 1 1 2 1 1 1 3 3 3 3 4 3 5 3 6 3 7 3 3 3 3 12 1 2 2 2 2 2 1 1 1 1 1 2 3 2 2 2 4 4 4 4 4 4 3 111111 3 3 1 3 2 3 3 4 3 3 3 2 2 4 2 2 2 2 2 2 2 1 1 1 2 3 31 2 2 3 4 2 3 2 1 1 1 4 3 3 0 3 4 2 Candelna nltlda Orbullna bllobata Orbullna unlversa Globlgerina druryl Globorotalla scltula 1 Globorotalla mayerl Globlgerina bulloldes Globlgerlnoides ruber Globorotalla menardii Globlgerlnoides mllra Globlgerina nepenthes Globoquadrlna altlsplra Hastlgerlna slphonlfera Clavatorella bermudezl Globlgerina venezuelana Praeorbullna traneltorla Globorotalla margarltae Globlgerlnoides trllobus Globoquadrlna dehlscens Globorotalla acostaensls Globorotalla lenguaensls Globorotalla menardii ’B' Globorotalla praemenardll Hastlgerlna praeslphonlfera Globlgerlnoides blsphaerlcus Sphaeroldlnellopsls dlsjuncta Sphaeroldlnellopsls multiloba srlnoldes trllobus saccullterus Quita Coraza area and the Arroyo Las Lajas section of the lower Rio Yaque del Sur Valley Valley Sur del Yaque Rio lower the of section Lajas Las Arroyo the 2.1). and Table area Coraza of Quita explanation (see Azua near section Via Rio the and Table 2.2 - Estimated relative abundance of planktonic foraminifera in samples from the from the in samples foraminifera ofplanktonic abundance relative Table 2.2 - Estimated Sphaeroldlnellopsls semlnullna Globorotalla fohsl lobata-robusta Globorotalla fohsl perlpheroacuta Globorotalla tohsl perlpheroronda

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1 1 4 4 1 2 2 1 1 4 1 2 3 2 4 4 2 4 2 3 3 3 1 1 1 1 1 3 3 1 4 4 3 3 1 2 1 2 2 3 4 3 3 4 4 1 1 1 1 3 116117118119120 121 122123 2 2 1 3 1 3 4 3 GL Azua-Barahona Highway ssctlon 3 2 AB

1 1 1 2 1 3 3 2 2 2

2 1 1 1 4 2 2 1 1 2 2 1 2 2 2 4 QC 2 1 3 2 2 1 7 7 7 8 ? 2 4 3 7 6

1 2 4 2 3 3

1 2 2 2 2 2 4 4 3 3 3 3

1 2 2 2 2 1 4 4 3 7 3 7 4 a 7 5

2 2 1 2 1 1 4 2 1 2 7 2 2 111 3 3 3 3 71

1 2 2 2 4 7 0 1 1 1 1 1 1 4 4 Fondo Negro area

2 2 2 1 1 2 3 3 1 1 2 2 4 6 6 6 9 1 1112 1 3 3 2 4

1 1 2 1 3 4 1 1 2 3 6 4 3 4 a t 6 5 1 1 2 2 4 4 3 6 3

1 1 2 1 2 2 3 4

2 1 1 1 1 1 1 3 3 2 322233322 11111 11 4 6 0 61 ? 1 11112 11111111 4 4 5 9 2 3 3 2 5 8 3133333321 32332233333 Fondo Negro area, lower Rio Yaque del Sur Valley, (see explanation of Table 2.1). Table of explanation (see Valley, Sur del Yaque Rio lower area, Negro Fondo Table 2.3 - Estimated relative abundance of planktonic foraminifera in samples from the the from in samples foraminifera planktonic of relative Table abundance 2.3 - Estimated Candelna nlllda Orbullna bllobata 1 2 2 1 2 1 2 2 2 Orbullna unlversa Globlgerina druryl Globorotalla scltula 1 Globorotalla mayerl Globlgerina bulloldes Globorotalla menardii 1 GloblgerlnoidesGloblgerlnoides ruber mltra Globlgerina nepenthes Hastlgerlna slphonlfera 2 Globoquadrlna altlsplra Clavatorella bermudezl iioeoquaarmu uumoi.oiio uumoi.oiio iioeoquaarmu . . . Praeorbullna transltorla Globorotalla margarltae Globlgerina venezuelana Globoquadrlna dehlscens Globorotalla acostaensls 2 Globlgerlnoides trllobus Globorotalla lenguaensls Globorotalla menardii "B* Globorotalla praemenardll Hastlgerlna praeslphonlfera Globlgerlnoides blsphaerlcus Sphaeroldlnellopsls dlsjuncta Sphaeroldlnellopsls multiloba Sphaeroldlnellopsls semlnullna 3 1 Globorotalla fohsl lobata-robusta Globorotalla fohsl perlpheroacuta Globlgerlnoides obllquus obllquus Globorotalla fohsl perlpheroronda Globlgerlnoides obllquus extremus Globlgerlnoides trllobus saccullferus

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Jealousy Formation of St. Croix (McLaughlin and others, in prep.), agreeing with its stated appearance in zone N7 by Kennett and Srinavasan (1983).

Upper Rio Yaque del Sur and San Juan Valleys Sombrerito Formation Planktonic foraminifera are abundant in the Sombrerito Formation, commonly comprising as much as 25 weight percent of the rock. It is the richest unit of the study but its fauna is the least well preserved; recrystallization is the major problem. Species identified in Sombrerito samples of this region indicate that it ranges in age from early to middle Miocene. Marls collected along Rfo Los Baos south of San Juan (RD-126 and 127; Fig. 2.1) are the oldest, and contain a rich planktonic foraminiferal fauna, including Globigerinoides bisphaericus Todd, Clavatorella bermudezi Bolli, and Praeorbulina transitoria Blow (Table 2.1). The presence of these species and the absence of Praeorbulina glomerosa (Blow), Orbulina and Globigerinoides obliquus obliquus Bolli suggest placement in the upper part of the lower Miocene, in the lower Globigerinatella insueta chronozone (N7). Farther to the southeast, in its type section, species identified in the upper part of the Sombrerito indicate a middle Miocene age. The presence of Globorotalia fohsi peripheroronda Blow and Banner and Globorotalia praemenardii Cushman and Stainforth in the lower samples (RD-125; Table 2.1) demonstrate equivalence to the lower-middle part of the Globorotalia fohsi fohsi zone (N10). A gradational development of the Globorotalia fohsi peripheroacuta Blow and Banner from G. f. peripheroronda occurs upsection (RD- 125a, 125b, 124) indicating the upper part of the G. f. fohsi chronozone (N10).

Trinchera Formation The Trinchera Formation crops out along many of the arroyos on the east side of the

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Rio Yaque del Sur and Rio San Juan. It generally has a rich microfauna in this region, with planktonics making up over 80 percent of the foraminifera (Table 2.1). The strata at the Trinchera Bluffs (RD-2 to 4), type locality of this unit (Fig. 2.3), contain Globorotalia acostaensis Blow and are placed in the upper Miocene Globorotalia acostaensis zone (N16). The presence of Globiperinoides obliquus extremus Bolli and Bermudez and Candeinanitida d'Orbigny higher in the formation indicate equivalence to the Globorotalia humerosa zone (N17). Previously, the Trinchera in this area was thought to lie in the upper part of the middle Miocene (Bold, 1975). The oldest Trinchera strata identified in this study are found in the lower part of the

Arroyo Salado section (RD- 6a to 8). There a middle to late Miocene fauna that includes Globorotalia lenguaensis Bolli was identified (Table 2.1), indicative of the Globorotalia menardii chronozone (N15) or to the lower part of the Globorotalia acostaensis chronozone (N16). This fauna also contains forms identified as Sphaeroidinellopsis seminulina (Schwager), which Bolli and Saunders consider to first appear in the upper Miocene. These forms, however, may be transitional with the middle to upper Miocene Sphaeroidinellopsis multiloba (LeRoy), which is distinguished by a slightly thinner glassy cortex around the test. The Trinchera at Arroyo Las Lajitas (RD-132 to 136) and at the upper part of the Arroyo Salado section (RD-9b to 13) can correlated with the upper part of the Globorotalia humerosa zone (N17) based on the occurrence of Candeina nitida and Globigerinoides obliquus extremus and the absence of Globorotalia margaritae Bolli and Bermudez (Table

2.1). Strata exposed at the Los Bancos bluffs (RD-5 and 6) may be equivalent. They exhibit the same style of sedimentation, but contain a much poorer fauna, the most stratigraphically useful species being Globigerina nepenthes Todd. Samples of the lower Trinchera Formation taken within 10 m of the base of the "Florentino Limestone" in its type area (RD-129 to 131), yield rich planktonic foraminiferal faunas characteristic of the uppermost Miocene Globorotalia humerosa zone (N17) (Table

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2.1). All lie stratigraphically below the first appearance of Globorotalia margaritae but contain forms that appear at the base of the Globorotalia humerosa zone (specifically Globigerinoides obliquus extremus in RD-129 and 130) or in the upper part of the zone (Candeinanitida in RD-131). Sample RD-128 is stratigraphically below the other three. It contains a poorer fauna with neither of the above forms but does contain the seven and eight chambered Globorotalia menardii "B" Bolli, suggesting placement in the upper part of the Globorotalia acostaensis chronozone (N16) or in the Globorotalia humerosa chronozone (N17) (Bolli and Saunders, 1985).

Arrovo Blanco Formation The Arroyo Blanco Formation in this region is devoid of planktonic foraminifera with the exception of the lowest sample (RD-137) in Arroyo Las Lajitas (Fig. 2.3). This is placed in the upper part of the Globorotalia humerosa chronozone (N17) based on the presence of Candeinanitida and the absence of Pliocene forms such as Globorotalia margaritae and Globigerinoides ruber (d'Orbigny).

Lower Rio Yaque del Sur Valley The lower Rio Yaque del Sur Valley section is long and nearly continuous and may be reliably correlated from section to section (Fig. 2.2).

Sombrerito Formation At the CanoaDome travertine quarries (RD-112 and 113), the Sombrerito Formation contains rich planktonic foraminiferal faunas (Table 2.2). The occurrence of Globorotalia praemenardii and forms transitional between Globorotalia fohsi lobata Bermudez and G. fohsi robusta Bolli place these samples in the middle Miocene G. fohsi robusta chronozone (N12).

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A sample of the Gajo Largo member from the roadcut just east of the Canoa Dome (RD-114) contains a rich middle Miocene fauna, including Globorotalia maveri Cushman and Ellisor and Globigerina nepenthes, which places it in the Globorotalia maveri chronozone (N14). A stratigraphically higher sample (RD-115), from atop the Gajo Largo ridge, is not as rich but can be correlated to the upper Miocene Globorotalia acostaensis zone based on the presence of the nominate taxa, notably small four-chambered forms, and the absence of younger taxa. Bolli and Saunders (1985) noted that small G. acostaensis are typical of the lower part of the zone; upward, larger five-chambered forms develop. The lower Gajo Largo sample (RD-114) is probably only slightly younger than the Sombrerito section exposed on the Canoa Dome (RD-112 and 113). The zone missing between these strata, the Globigerinoides ruber zone (N13), may be difficult to recognize in the Caribbean (Bolli and Saunders, 1985), so the time interval between their deposition was likely very brief. In addition to the lithologic similarities discussed earlier, this is another reason for including the Gajo Largo Member in the Sombrerito rather than the Trinchera.

Trinchera Formation The Trinchera turbidite section in the lower Rfo Yaque del Sur Valley region (Fig. 2.2) ranges from uppermost Miocene to lower Pliocene. The lowest part of this section, exposed along the Azua-Barahona Highway (RD-116 and 117), contains Candeina nitida and is placed in the upper part of the uppermost Miocene Globorotalia humerosa chronozone (Table 2.2). The first appearance of Globorotalia margaritae margaritae Bolli and Bermudez, approximately 300 meters above the Trinchera - Gajo Largo contact (RD-118; Table 2.2), is used to mark the base of the Pliocene. This species persists nearly to the top of the formation (up to RD- 74a) around the Fondo Negro area (highway and Arroyo El Puerto sections). It is notable that nearly all specimens of Globorotalia margaritae margaritae

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recovered from the Trinchera exhibit dextral coiling; Bolli and Saunders (1985) observed that this typically sinistrally-coiled species is commonly dextrally-coiled near the base of the Pliocene. Based on these criteria, the stratigraphic interval between RD-118 and RD- 74a is placed in the lower part of the Globorotalia margaritae margaritae subchronozone (N18). Above sample RD-74a, G. margaritae margaritae is lost, probably as a result of shoaling which excluded deeper-dwelling planktonic forms such as Globorotalia. Globigerinoides ruber appears in RD-75 (Table 2.2), and Globigerina nepenthes is present to the top of the Trinchera (RD-77). From these occurrences, the uppermost Trinchera strata (RD-75 to 77) appear to be chronostratigraphically equivalent to the upper part of the G. margaritae margaritae subzone (N18) or the G. margaritae evoluta subchronozone (N19). The interval between the top of the Gajo Largo Member of the Sombrerito and the first appearance of the Pliocene marker G. margaritae margaritae is approximately 300 m thick. This would seem too thin an interval to represent nearly all of the upper Miocene

considering the rapid sedimentation rates (in places over 100 cm/Ky) in the region at that time. This appears to confirm, then, Cooper's (1983) suspicion that the fault he mapped at the Gajo Largo - Trinchera boundary has a significant thrust component. The foraminiferal data suggest that middle Miocene (and lowest upper Miocene) strata have been thrust up over most of the upper Miocene strata. Farther northeast in Arroyo de Bergal and Arroyo del Bao (Fig. 2.2), samples of the Trinchera (RD-30 to 42) are not quite as rich as in the Fondo Negro area. Rare specimens of Globorotalia margaritae margaritae are found in samples RD-33 and 35 (Table 2.3). This, along with the presence of Globigerina nepenthes throughout the section, the appearance of Globigerinoides obliquus extremus in the lowest sample of the section, and scattered occurrences of Candeina nitida. suggests an early Pliocene age for the section,

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within the Globorotalia margaritae zone (N18 or 19). This is in agreement with field relationships that suggest equivalence to the upper part of the Fondo Negro section.

Quita Coraza Formation The Quita Coraza Formation was sampled in both the Fondo Negro and Quita Coraza areas (Tables 2.2 and 2.3). Planktonic foraminifera are relatively common in the lower part of the formation but they occur less frequently in the upper part. Globorotaliids are especially scarce; shallow-dwelling Globigerinoides spp. dominates the fauna. This unit may be considered equivalent to the upper Globorotalia margaritae margaritae subzone (upper N18) or the G. margaritae evoluta subzone (N19) on the basis of the presence of Globigerina nepenthes throughout the formation and of its stratigraphic position above the first occurrences of Globorotalia margaritae margaritae and Globigerinoides ruber.

Arrovo Blanco Formation Ostracoda (Bold, 1975a; 1981) and benthic foraminifera (including Cancris sagra (d’Orbigny), Elphidium spp.) indicate that the Arroyo Blanco Formation was deposited in shallow and restricted marine environments. As a consequence, planktonic foraminifera are rare, with only two samples yielding a notable number of planktonics. Sample RD-101 (Table 2.2), from Arroyo Barranca across the Rio Yaque del Sur from Fondo Negro (Fig. 2.2), is well above the first occurrence of Globigerinoides ruber and the Pliocene-marking Globorotalia margaritae margaritae and contains Globigerinoides obliquus obliquus. which becomes extinct high in the lower Pliocene. The sample may be assigned to the lower Pliocene in an interval from the middle of the Globorotalia margaritae margaritae subchronozone zone (upper N18) to the upper part of the Globorotalia margaritae evoluta subchronozone (N19). Higher samples contain poor faunas or mostly reworked forms.

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Along Arroyo Las Lajas, about 12 km east of Quita Coraza, one sample (PM-84-7; Fig. 2.1) contains very rare planktonic foraminifera including Globigerinoides ruber, indicating chronozonal placement no lower than the middle of the lower Pliocene Globorotalia margaritae margaritae subzone (N18). The upper stratigraphic limit could not be determined by the fauna. Ostracode studies by Bold (oral comm., 1985) of the upper marginal-marine strata suggest that the formation extends into the upper part of the Pliocene or even possibly into the Pleistocene.

Azua Region The Trinchera (RD-14 to 16) and Quita Coraza (RD-19 to 22) Formations in Rfo Via yielded marginally useful planktonic foraminiferal faunas (Fig. 2.4). Candeinanitida and Globigerina nepenthes occur upward from the lowest sample in the section, but neither Globorotalia margaritae margaritae nor any other Pliocene index species is present. Considering that the lack of Pliocene forms may be due to ecological rather than chronostratigraphic factors, these strata may be considered equivalent to the upper part of the upper Miocene Globorotalia humerosa zone (upper N17) or the lower Pliocene Globorotalia margaritae zone (N18 and/or N19).The Arroyo Blanco Formation samples (RD-23 to 26) contain only meager faunas or reworked forms.

REGIONAL CORRELATION

Earlier biostratigraphic studies can be re-evaluated through the Bolli and Saunders (1985) zonation to establish a regional stratigraphic correlation scheme. In Fig. 2.6, the results of such an analysis of Neogene sequences from Hispaniola and around the Caribbean is presented.

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Planktonic HISPANIOLA Foraminiferal OTHER CARIBBEAN SEQUENCES Azua Central Enrlqulllo Zonation NW hE Basin Plateau Basin Jam aica1 St. Croix Venezuela Venezuela Trinidad Gr. flmbriata B 2

Gg. callda calida

Gr. crass, hessl

Gr. crass, viola

Gr. tosaenste tosaensls

Gr. exllls Salinas Bowden Gs. t. fistulosus Arroyo Morn© Blanco Angostura Mao Gr. m. evoluta Delm as Quita Coraza Gr. m. margaritae Cubagua Gr. humerosa Las Butt Cahobas Bay Gr. acostaensis

Largtt Carnero Lengua Gr. mayerl

Gs. ruber

Gr. fohsl robusta Sombrerito

Gr. fohsl iobata

Gr. fohsl fohsl Som brerito

Gr. fohsl peripheroronda

P. gtomerosa Cipero Madame Jo le

Tocuyo

Figure 2.6 - Correlation chart comparing the Neogene sequence of the Azua Basin to other io’ (1985), Saunders et al. (1986), and

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Four Neogene sequences on Hispaniola can be correlated to the Azua Basin succession. The Central Plateau in east-central Haiti is essentially a western extension of the Azua Basin. The planktonic foraminiferal biostratigraphy has been studied by Hunerman (1972), Bold (1981), and Dubreuilh (1984). Correlation with the Enriquillo Basin, to the south of the Azua Basin, is more difficult due to the prevalence of shallow- water conditions there. Ostracode and foraminifera faunas reported by Bold (1975 and oral comm., 1987) suggest the correlations reported in Fig. 2.6. Deeper-water conditions persisted a bit later in the Haitian continuation of the Enriquillo, known as the Cul-de-Sac Basin. The biostatigraphy of this area has been reported by Bold (1975), Berghe (1983), and Desreumaux and Andreieff (1984). The Neogene sequence of the Cibao Valley in the northern Dominican Republic was recently studied in detail by Saunders, Jung, and Biju- Duval (1986). There a general increase in paleodepth is evident upsection, in contrast the the overall upward shoaling in the Azua Basin. Published descriptions of foraminiferal faunas from Jamaica, St. Croix, Trinidad and Venezuela can be re-evaluated using Bolli and Saunders (1985) and compared to the faunal successions here reported in the southwestern Dominican Republic. The planktonic foraminifera of the Bowden and Buff Bay Formations in Jamaica were discussed by Lamb and Beard (1972). Studies of the Jealousy and Kingshill Formations of St. Croix were done by Lidz (1982) and Andreieff and others (1987). Comparison to the Tertiary sequence of Trinidad is based on the faunas reported by Bolli (1957). The Pozdn Formation of northwestern Venezuela was studied by Blow (1959) and the Camera Formation of northwestern Venezuela by Bolli and Bermudez (1965). Such regional stratigraphic correlations may yield insights into the geologic evolution of an area. For example, many of the sequences evaluated here reflect a marked increase in clastic sedimentation later in the middle Miocene or in the late Miocene: the Azua Basin, the Central Plateau, the Enriquillo Basin, and the Cul-de-Sac Basin on Hispaniola; and the St.

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Croix sequence. In many areas of the northern Caribbean, middle Miocene unconformities are evident (Draper, 1988). This may support the idea that wiench-fault activity along the Northern Caribbean Plate Boundary Zone became an important component of Caribbean tectonics by the close of the middle Miocene (Mann, oral comm., 1988), causing vigorous uplift, erosion, and rapid sedimentation in the stratigraphic sequences.

SUMMARY

Using planktonic foraminifera, I have established a biostratigraphic framework for the Neogene strata of the southwestern Dominican Republic, as follows: Sombrerito Formation - Lower Miocene (Globigerinatella insueta chronozone, about N7) near San Juan de la Maguana to middle Miocene at the type locality (Globorotalia fohsi fohsi chronozone, about N10) and at Canoa Dome (G. fohsi robusta chronozone, about N12); upper part of the middle Miocene (Globorotalia maveri chronozone, about N14) to the lowest part of the upper Miocene (equivalent to lower part of Globorotalia acostaensis zone, about lower N16) in the Gajo Largo member near Canoa. Trinchera Formation - In the Rio San Juan and upper Rio Yaque del Sur Valleys, middle Miocene (Globorotralia menardii chronozone, about N15) or lowest part of the upper Miocene (lower Globorotalia acostaensis chronozone, about lower N16) in the lower part of the section at Arroyo Salado, to uppermost Miocene (upper Globorotalia humerosa chronozone, about N17) at the top of the formation at Arroyo Las Lajitas; in the lower Rio Yaque del Sur Valley, upper Miocene (upper Globorotalia humerosa chronozone, about upper N17) to lower Pliocene (equivalent to Globorotalia margaritae margaritae subzone, about N18) in the Fondo Negro highway section; in the Azua Region, uppermost Miocene (upper Globorotalia humerosa chronozone, about upper N17).

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Quita Coraza Formation - In the lower Rfo Yaque del Sur Valley, lower Pliocene (equivalent to Globorotalia margaritae margaritae subzone, about N18, and possibly G. m. evoluta subzone, about N19); in the Azua Region, uppermost Miocene (upper Globorotalia humerosa chronozone, about upper N17) or possibly lower Pliocene (Globorotalia margaritae chronozone, about N18 and N19). Arroyo Blanco Formation - hi the Rfo San Juan and upper Rfo Yaque del Sur Valleys, uppermost Miocene (upper Globorotalia humerosa chronozone, about upper N17) and above; in the lower Rfo Yaque del Sur Valley, lower Pliocene (Globorotalia margaritae chronozone, about N18 and/or N19) and younger; in the Azua Region, uppermost Miocene (upper Globorotalia humerosa chronozone, about upper N17) or lower Pliocene (Globorotalia margaritae chronozone, about N18 and/or N19) and above. These ages are younger than reported in most previous studies, which lacked detailed information on planktonic foraminifera. Overall, the formations of the Azua Basin appear to become younger southeastward. The upper part of the Sombrerito at its type locality in the upper Rfo Yaque del Sur Valley is of lower middle Miocene age, whereas the upper part of the Sombrerito in the lower Rfo Yaque del Sur Valley is middle middle Miocene in age. The Trinchera - Arroyo Blanco contact in the Rfo San Juan and upper Rfo Yaque del Sur Valleys is of late Miocene age, but in the lower Rfo Yaque del Sur Valley the top of the Trinchera and the bottom of the Arroyo Blanco are of early Pliocene age. The establishment of a detailed biostratigraphic scheme for the Azua Basin allows correlation to formations in other Neogene sequences on Hispaniola and around the Caribbean: Sombrerito Formation - equivalents in the Central Plateau of Haiti (Madame Joie - Thomonde); the Cul-de-Sac Basin of Haiti (lower part of Rivfere Grise); northwestern Venezuela (lower part of Pozdn); St. Croix (Jealousy - lower part of Kingshill); and Trinidad (Cipero).

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Trinchera Formation - equivalents in the Central Plateau (upper part of Thomonde - Las Cahobas); the Cul-de-Sac Basin (upper part of Riviere Grise - lower part of Mome Delmas); the Cibao Basin (Cercado - lower part of Gurabo); northwestern (upper part of Pozdn) and northeastern (Camero - lower part of Cubagua) Venezuela; St. Croix (upper part of Kingshill); Trinidad (uppermost part of Lengua); and Jamaica (lower Buff Bay). Quita Coraza and Arroyo Blanco Formations - equivalents in the Central Plateau (upper part of Las Cahobas); the Enriquillo Basin (Angostura - ?lowermost part of Las Salinas); the Cul-de-Sac Basin (Mome Delmas); the Cibao Basin (Gurabo - Mao); northeastern Venezuela (upper part of Cubagua); St. Croix (upper part of Kingshill); and Jamaica (upper part of Buff Bay - Bowden). This planktonic foraminiferal data should aid in future geologic investigations in the southwestern Dominican Republic, especially those related to the evolution of the Azua Basin and to temporal shifts in its benthic foraminiferal assemblages. It also updates the correlation of stratigraphic sequences around the margins of the Caribbean. Better understanding of these points may aid in delineating the Neogene movements of the Caribbean Plate.

ACKNOWLEDGMENTS

This research was supported in part by the Chevron USA, Inc. Field Scholarship Fund and by the McKee Micropaleontologic Scholarship Fund through the Geology Endowment at Louisiana State University, and by an ORF grant from the university's Office of Graduate Planning. Research funding through the National Science Foundation (grant number EAR 8720201) and the 1987 Joseph A. Cushman Student Research Grant is also gratefully acknowledged.

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Many thanks are owed to W.A. van den Bold and B.K. Sen Gupta (Louisiana State University) for their encouragement and critical reading of the manuscript. J.E. Hazel (Louisiana State University) reviewed the manuscript and offered helpful advice on stratigraphic nomenclature. Helpful comments on the paper by A.J. Melillo (Chevron USA, Inc.) and C.W. Poag (U.S.G.S., Woods Hole) are gratefully acknowledged. Appreciation is extended to P. Mann (Institute for Geophysics, University of Texas) for his valuable cooperation in this study as well as to E. Deveaux, L. Pena and J. Rodriguez

(Santo Domingo, Dominican Republic). The assistance of the Direcci 6n General de Minerfa, Dominican Republic, is gratefully acknowledged, with special thanks to L Tavares and E. Garcia of the Departmento de Geologfa.

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REFERENCES

Andreieff, P., Bouysse, P., and Westercamp, D., 1987, Gdologie de l'arc insulaire des Petites Antilles, et Evolution g^odynamique de l’est Caraibe: Th&se de Doctorat

d'Etat 6s Sciences, no. 921, University de Bordeaux 1,359 p.

Berghe, B. van den, 1985, Evolution s 6dimentaire et structurale depuis le Paleocene du secteur "Massif de la Selle" (Haiti) - "Bahoruco" (Republique Dominicaine) au nord de la ride de Beata dans l'orogene nord-Caraibe (Hispaniola - Grandes Antilles): Unpubl. 3rd Cycle Doctorate Thesis, University de Pierre et Marie Curie, Paris, 205 p.

Bermudez, P.J., 1949, Tertiary smaller foraminifera of the Dominican Republic: Cushman Laboratory for Foraminiferal Research Special Publication 25,322 p.

Biju-Duval, B, Bizon, G., Mascle, A., and Muller, C., 1982, Active margin processes: Field observations in southern Hispaniola: American Association of Petroleum Geologists Memoir 34, p. 325-344.

Blow, W. H., 1959, Age, correlation and biostratigraphy of the upper Tocuyo (San Lorenzo) and Pozon Formations, Eastern Falcon, Venezuela: Bulletins of American Paleontology, v. 39, p.59-251.

------} 1969, Late Middle Eocene to Recent planktonic foraminiferal biostratigraphy: Proceedings First International Conference on Planktonic Microfossils, 1967, v. 1, p.199-442.

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Bold, W.A. van den, 1981, Distribution of Ostracoda in the Neogene of Central Haiti: Bulletins of American Paleontology, v. 79,136 p.

------, 1975, Neogene biostratigraphy (Ostracoda) of southern Hispaniola.

Bulletins of American Paleontology, v. 66, p. 549- 639.

Bolli, H.M., 1957, Planktonic foraminifera from the Oligocene - Miocene Cipero and Lengua Formations of Trinidad, B.W.I.: U.S. National Museum Bulletin, v.215, p.155-172.

------, and Bermudez, P.J., 1965, Zonation based on planktonic foraminifera of middle Miocene to Pliocene warm-water sediments: Boletin Informativo,

Asociacidn Venezolano de Geologia, Minerfa y Petroleo, v. 8 , p.l 19-149.

------, and Saunders, J.B., 1985, Oligocene to Holocene low-latitude planktic foraminifera in Bolli, H.M., Saunders, J.B., and Perch-Nielsen, K., eds., Plankton Stratigraphy: Cambridge, University Press, 1032 p.

Breuner, T.A., 1985, The geology of the eastern Sierra de Neiba, Dominican Republic: Unpublished M.S. Thesis, George Washington University.

Butterlin, J., 1956, La constitution gdologique et la structure des Antilles: Centre National de Recherches Scientifique, 453 p.

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Cooper, J.C., 1983, Geology of the Fondo Negro region, Dominican Republic: Unpublished M.S. Thesis, State Univ. N.Y. at Albany, 125 p.

Desreumaux, C. and Andreiff, P., 1984, T 6ctonique tangentielle et sedimentation du Miocene a l'Holocene dans le sud d'Haiti (Grandes Antilles): 106£me Congrfes National de Socifete de Savantes, Dijon, fasc. 1, p. 323-334.

Draper, G., 1988, Tectonic reconstruction of N. Hispaniola and S.E. Cuba: Dissection of a Cretaceous Island Arc: GSA Abstracts with Programs, v. 20, no. 7, p.60.

Dubreuilh, P., 1984, Evolution du bassin s£dimentaire du centre d'Haiti au Neogene: Bulletin de l'lnstitut Geologique du Bassin d'Aquitaine, Bordeaux, v.35, p.53-76.

Hunerman, A., 1972, Middle Tertiary biostratigraphy of the Central Plateau of Haiti: Unpublished M.S. thesis, Louisiana State University - Baton Rouge.

Kennett, J.P., and Srinivasan, M.S., 1983, Neogene Planktonic Foraminifera - A Phylogenetic Atlas: Hutchinson Ross Publ. Co., Stroudsburg, PA, 265 p.

Lamb, J.L., and Beard, J.H., 1972, Late Neogene planktonic foraminifers in the Caribbean, Gulf of Mexico, and Italian stratotypes: University of Kansas

Paleontology Contributions, Article 57 (Protozoa 8), 67 p.

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Lebron, M.C., Rodriguez, J., Mann, P., and Dolan, J.F., 1986, A 1:100,000 scale geologic compilation map and regional stratigraphic synthesis of southern Hispaniola (abstr.): Geological Society of America Abstracts with Program v. 19,

p. 669.

Lidz, B.H., 1982, Biostratigraphy and paleoenvironment of Miocene-Pliocene hemipelagic limestone: Kingshill Seaway, St. Croix, U.S. Virgin Islands: Journal of Foraminiferal Research, v.12, p.205-233.

Mann, P., Burke, K., and T. Matumoto, 1984, Neotectonics of Hispaniola: Plate motion, sedimentation, and seismicity at a restraining bend: Earth and Planetary Science Letters, v. 70, p.311-324.

Mutti, E., and Ricci Lucchi, F., 1972, Le torbiditi dell’Appenino settentrionale: introduzione all'analisi di facies: Memorias, Societia Geologica Italiana, v. 11, p.161-199 (Translated by T.H. Nilsen, 1978, Turbidites of the northern Appenines: introduction to facies analysis: International Geology Review, v. 20, p.125-166).

North American Commission on Stratigraphic Nomenclature, 1983, North American Stratigraphic Code: American Association of Petroleum Geologists Bulletin, v.67,

p.841-875.

Saunders, J.B., Jung, P., and Biju-Duval, B., 1986, Neogene paleontology in the northern Dominican Republic. 1. Field surveys, lithology, environment and age: Bulletins of American Paleontology, v. 89, p.1-79.

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Walker, R.G., 1984, Turbidites and associated coarse clastic deposits in Walker, R.G., ed., Facies Models: Geoscience Canada, Reprint seies 1, p.171-188.

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PLATE 1 1 Globigerina venezuelana Hedberg. Spiral view, Trinchera Formation (RD-131), xl50. 2 Globigerina bulloides d'Orbigny. Side view, Trinchera Formation (RD-130), x2 0 0 . 3 Globigerina drurvi. (Akers). Umbilical view, Gajo Largo member (RD-114), x2 0 0 . 4 Globigerina nepenthes Todd. Umbilical view, Trinchera Formation (RD-13), x2 0 0 . 5 Globigerinoides trilobus trilobus (Reuss). Spiral view, Trinchera Formation (RD- 70), x200. 6 Globigerinoides trilobus immaturus LeRoy. Spiral view, Trinchera Formation (RD-34), xl50. 7 Globigerinoides trilobus sacculiferous (Brady). Apertural view, Trinchera Formation (RD-70), xl50. 8 Globigerinoides bisphaericus Todd. Spiral view, Sombrerito Formation (RD- 126), xl50. 9 Globigerinoides obliquus obliquus Bolli. Apertural view, Trinchera Formation (RD-7), x200. 10-11. Globigerinoides obliquus extremus Bolli & Bermudez. 10. Apertural view, Trinchera Formation (RD-70), x200.11. Spiral view, Trinchera Formation (RD- 70), xl50. 12-13. Globigerinoides ruber (d'Orbigny). 12.Spiral view, Sombrerito Formation (RD- 113), xl50. 13. spiral view, Trinchera Formation (RD-70), xlOO. 14 Globigerinoides mitra Todd. Side view, Sombrerito Formation (RD-125), xlOO. 15-17 Globorotalia fohsi peripheroronda Blow & Banner. 15. Spiral view, Sombrerito Formation (RD-125), xl50.16. umbilical view, Sombrerito Formation (RD- 125), x200.17. side view, Sombrerito Formation (RD-125), x200. 18-20 Globorotalia fohsi peripheroacuta Blow & Banner. 18. Spiral view, Sombrerito Formation (RD-124), x200.19. Umbilical view, Sombrerito Formation (RD- 124), x200.20. Side view, Sombrerito Formation (RD-124), x200. 21-23 Globorotalia fohsi lobata Bermudez - G. f. robusta Bolli transition. 21.Umbilical view, Sombrerito Formation (RD-113), xlOO. 22. Spiral view, Sombrerito Formation (RD-113), xlOO. 23. Side view, Sombrerito Formation (RD-113), xlOO.

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PLATE 2 1-3 Globorotalia maveri Cushman & Ellisor. 1. Spiral view, Gajo Largo member (RD-114), x200. 2. Umbilical view, Gajo Largo member (RD-114), x200. 3. Side view, Gajo Largo member (RD-114), x200. 4-6 Globorotalia scitula (Brady). 4. Spiral view, Trinchera Formation (RD-70); xl50.5. Umbilical view, Trinchera Formation (RD-70); xl50.6. Side view, Trinchera Formation (RD-70), xl50. 7-9 Globorotalia lenguaensis Bolli. 7. Spiral view, Trinchera Formation (RD-7), x200.8 . Umbilical view, Trinchera Formation (RD-7), x200.9. Side view, Trinchera Formation (RD-7), x200. 10-12 Globorotalia praemenardii Cushman & Stainforth. 10. Spiral view, Sombrerito Formation (RD-125), xl50.11. Umbilical view, Sombrerito Formation (RD- 125), x l5 0 .12. Side view, Sombrerito Formation (RD-125), xl50. 13-15 Globorotalia menardii (Parker, Jones, and Brady). 13. Spiral view, Trinchera Formation (RD-70), x l5 0 .14. Umbilical view, Trinchera Formation (RD-70), xlOO. 15. Side view, Trinchera Formation (RD-70), x200. 16-17 Globorotalia menardii "B" Bolli. 16. Umbilical view, Trinchera Formation (RD- 61), x l5 0 .17. Spiral view, Trinchera Formation (RD-60), xlOO. 18-20 Globorotalia acostaensis Blow. 18. Spiral view, Trinchera Formation (RD-9b), x200.19. Umbilical view, Trinchera Forrmation (RD-9b), x200.20. Side view, Trinchera Formation (RD-9b), x200. 21-23 Globorotalia margaritae marparitae Bolli & Bermudez. 21. Spiral view, Trinchera Formation (RD-74a), x200.22. Umbilical view; Trinchera Formation (RD-74a), x200. 23. Side view, Trinchera Formation (RD-74a), x200. 24-25 Globoquadrina dehiscens (Chapman, Parr & Collins), spiral view; Trinchera Formation (RD-60); xl50.25. umbilical view; Trinchera Formation (RD-60); xl50. 26-28 Globoquadrina altispira (Cushman & Jarvis). 26. Spiral view, Trinchera Formation (RD-60), xlOO. 27. Umbilical view, Trinchera Formation (RD-60), xl50.28. Side view, Trinchera Formation (RD-60), xlOO.

PLATE 3 1-2 Praeorbulina transitoria (Blow). 1. Side view, Sombrerito Formation (RD-126), xl50. 2. Spiral view, Sombrerito Formation (RD-127), xl50. 3 Orbulina universa d'Orbigny. Trinchera Formation (RD-70), xlOO. 4 Orbulina bilobata (d'Orbigny). Trinchera Formation (RD-70), xlOO. 5-6 Sphaeroidinellopsis disiuncta (Finlay). 5. Umbilical view, Sombrerito Formation (RD-125), xl50. 6. Umbilical view, Sombrerito Formation (RD-125), xl50. 7-8 Sphaeroidinellopsis multiloba (LeRoy). 7. Spiral view, Sombrerito Formation (RD-113), xlOO. 8 . Spiral view, Sombrerito Formation (RD-113), xlOO. 9-10 Sphaeroidinellopsis seminulina (Schwager). 9. Spiral view, Trinchera Formation (RD-70), xl50.10. Umbilical view, Trinchera Formation (RD-70), xl50. 11 Hastigerina praesiphonifera (Blow). Lateral view, Sombrerito Formation (RD- 125a), xlOO. 12-13 Hastigerina siphonifera (d'Orbigny). 12. Lateral view, Trinchera Formation (RD- 79), xlOO. 13. Apertural face, Trinchera Formation (RD-79), xlOO. 14-16 Clavatoiella bermudezi (Bolli). 14. Umbilical view, Sombrerito Formation (RD- 125), xlOO. 15. Side view, Sombrerito Formation (RD-125), x200.16. Spiral view, Sombrerito Formation (RD-125), xlOO. 17 Candeina nitida d'Orbigny. Spiral view, Trinchera Formation (RD-19), x200.

GEOLOGY OF THE ENRIQUILLO-AZUA BASINS, DOMINICAN REPUBLIC, 2: DEPOSITIONAL HISTORY - FORAMINIFERAL AND OSTRACODE EVIDENCE

P.P. McLaughlin and W.A. van den Bold

(in review for GSA Special Paper - Geologic and Tectonic Studies on Hispaniola)

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ABSTRACT

The Neogene evolution of the Azua and Enriquillo Basins of the southwestern Dominican Republic has been controlled by tectonic activity along the northern boundary of the Caribbean Plate. The marine sequences change upward from deep-water, pelagic strata of the Sombrerito Formation to coastal clastic rocks of the Arroyo Blanco and Las Salinas Formations. A 2000 m thick, southeastward-prograding turbidite sequence, the Trinchera Formation, reflects this filling in the Azua Basin. A transition from finer-grained outer fan- type facies to coarser-grained inner fan-type facies is evident. Planktonic foraminiferal and ostracode evidence indicates that the Azua Basin marine sequence extends from lower to upper in its northwestern part and from middle Miocene to lower Pliocene in its southern part. The shallow-marine and lagoonal deposits of the Enriquillo Basin appear to extend from the lower Pliocene upward. Benthic foraminiferal paleobathymetry supports the lithofacies interpretation, indicating shoaling from near the lower-middle bathyal boundary to a marginal-marine realm in the Azua Basin. The region evolved in two stages: 1) a tectonically quiet open ocean stage before the late Miocene; 2) a subsequent tectonically-active, laterally-constrained clastic basin stage. The large volumes of elastics laid down during stage 2 indicate uplift and erosion of the Cordillera Central. The axis-parallel paleocurrents in the Azua Basin suggest contemporaneous uplift of the Sierra de Neiba as the laterally constraining structure. These events are interpreted as the result of activation of the Hispaniola restraining bend in the late Miocene.

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INTRODUCTION

The Enriquillo - Azua area of the southwestern Dominican Republic contains some of the thickest (up to 4000 m) and most complete Neogene marine sedimentary sections exposed in the northern Caribbean (Fig. 3.1). This area provides an ideal setting for micropaleontological and sedimentary facies studies. The sections are richly fossiliferous, relatively unfaulted, and well-exposed due to the semi-arid climate of the region. In addition, the southwestern Dominican Republic is a focal point of research on tectonics of the northern Caribbean Plate Boundary Zone. The area is influenced by boundary activity along the northern edge of the island and complicated by its position at the intersection of the Muertos Trough and the Beata Ridge. In a companion paper, Mann and others (this volume) have described the regional structure and stratigraphy of the Enriquillo - Azua area and the influence of this framework on the development of the Neogene basins. The overall aim of this paper is to examine the depositional history of the Enriquillo - Azua Basins by evaluating lithofacies, biofacies, and biostratigraphic data in light of the stratigraphic and structural framework provided by Mann and others (this volume). Specifically, the objectives are: 1) recognition of the sedimentary facies and their composition in the Azua and Enriquillo Basins;

2 ) establishment of a biostratigraphic framework using planktonic foraminifera and ostracodes; 3) characterization of the paleoenvironments present based on benthic foraminiferal and ostracode faunas; 4) integration of the sedimentary, biostratigraphic, and paleoenvironmental results with structural data to create a model for the depositional history of the basins; 5) consideration of the implications of this model for the timing and nature of movements along the Northern Caribbean Plate Boundary Zone.

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Figure 3.1 - Location of the study area, in the southwestern Dominican Republic, island of Hispaniola. The two Neogene basins, the Azua and the Enriquillo, lie between mountain thrust-blocks, the Cordillera Central, Sierra de Neiba, and Sierra de Bahoruco, from north to south. Localities discussed in the text are numbered, and areas of more concentrated sampling are expanded in Figures 2 and 3.

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Regional Setting and Stratigraphy

The southwestern Dominican Republic is characterized by a parallel, NW - SE oriented series of anticlinal thrust-block mountains and synclinal ramp basin valleys (Fig. 3.1). The thrust blocks make up the Cordillera Central, Sierra de Neiba / Sierra de Martin Garcia, and Sierra de Bahoruco, from north to south, and are composed of Cretaceous, Paleogene, and lower Neogene rocks. The Azua Basin, in the north, and the Enriquillo Basin, to the south, are filled with up to 4000m of Neogene marine sediments that exhibit a transition from fine-grained at the base of the sequence to coarse-grained at the top. The Beata Ridge Fault Zone extends northward from the Beata Ridge along the coast of the southern Dominican Republic and into the Bahia de Neiba. The trace of the Mueitos Trough continues westward from the Caribbean onto land in the Enriquillo - Azua area (see Mann and others, this volume). The Azua Basin (Fig. 3.1, A) covers an area from San Juan de la Maguana in the northwest (loc. 1, Fig. 3.1, and Fig. 3.2) to Azua in the southeast (loc. 2, Fig. 3.1) and Canoa in the south (Fig. 3.3). The northwestern part of the basin, between San Juan and Hato Nuevo, is referred to in this paper as the upper Rio Yaque del Sur - Rio San Juan Valley (detailed in Fig. 3.2) whereas the area at the break in the Sierra de Neiba - Sierra de Martin Garcia trend is referred to as the lower Rio Yaque del Sur Valley (detailed in Fig. 3). The Enriquillo Basin (Fig. 3.1, E) encompasses all of the modem Enriquillo Valley and includes strata exposed at and around the salt and gypsum mine near Las Salinas (loc. 7, Fig.l), sections from the Jimanl area (loc. 12, Fig.l), and material from the north shore of Lago Enriquillo (loc. 9, Fig.l). Six marine stratigraphic units are present in the Azua Basin (Fig. 3.4): the Sombrerito Formation, the Gajo Largo Member of the Sombrerito Formation, the Trinchera Formation, the Quita Coraza Formation, the Arroyo Blanco Formation, and the Barranca Member (Loma de Yeso Member of Cooper, 1983) of the Arroyo Blanco Formation. Three units in

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|71°05’ Reservoir

I Los( B a n c o s ' 5.6

SIERRA DE c v o lcan ic NEIBA sto c k s

T rin c h e ra ' B lu ff\\ 2km Florentino Limestone outcrops on hilltops -

-18 35

Figure 3.2 - Sampling localities in the upper Rio Yaque del Sur and Rio San Juan Valleys, northwestern Azua Basin. All samples are from the Trinchera Formation, with the exception of one (RD-137) in the Arroyo Blanco Formation at Arroyo Las Lajitas. The northeastern comer of the map is predominantly deltaic and fluvial deposits of the Arroyo Blanco and Arroyo Seco Formations, and the southwestern comer is dominated by outcrops of the Sombrerito Formation. More detailed geologic information is given on the map enclosure with this volume.

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Q £ < !

LU in

Figure 3.3 - Sampling localities in the lower Rio Yaque del Sur Valley, southern Azua Basin. Outcropping strata of the Trinchera, Quita Coraza, and Arroyo Blanco Formations dip to the northwest off the flank of the Sierra de Martin Garcia. The Sombrerito Formation and its Gajo Largo Member are exposed in a more structurally complex area near Canoa, located in the southwestern comer of the map.

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Azua Basin Enriquillo Basin

Pleistocene Arroyo Jimani Seco Fm. & Via Fms.

Las Salinas Arroyo Fm. Blanco Fm. Pliocene

Quita Coraza Angostura Fm. Fm.

Trinchera Fm.

Miocene

Gajo Largo Mbr.

Sombrerito Fm.

Table 3.4 * Subsidence in the lower Rfo Yaque del Sur Valley, using the method of Bandv and Amal (1960). J

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the Enriquillo Basin are examined in this study (Fig. 3.4): the Angostura Formation, the Las Salinas Formation, and the Jimanf Formation.

Previous work

Several paleontologic studies have been conducted in the Enriquillo - Azua Basins over the past 60 years. However, these studies often relied on poorly located samples collected by workers other than the investigators, and little attempt was made to integrate structural or sedimentary facies data. In Fig. 3.5, we compare various biostratigraphic zonations of the lithostratigraphic nomenclature accepted by Mann and others (this volume). The ages assigned in the previous works are older than those presented by us. The earliest comprehensive micropaleontologic study of the region is included in the foraminiferal monograph of Bermudez (1949), which interprets the Enriquillo - Azua marine sequence as middle Oligocene to lower Miocene. This interpretation can be explained, in part, if viewed in the light of the downward revision of the Oligocene - Miocene boundary since the time of Bermudez' work. Nearly thirty years later, the biostratigraphy was revised in Bowin (1975) and in Doreen (1975), both of whom considered the sequences to be of Miocene age. The former study is based on a review of Bermudez' work, whereas the latter is based on restudy of a small set of his type material. In both studies, the age assignment for the Trinchera Formation was based on inappropriate samples. Bermudez (1949) notes that the Trinchera Formation "occurs widely in the Azua- San Juan basin, the Comendador area and in Trujillo Province." The Comendador area is west of the Azua Basin, near the Haitian border, and contains strata that have been placed in the Trinchera Formation. However, these are more appropriately placed in the Thomonde Formation because of greater lithologic similarity and the fact that it is possible to trace the strata directly to the type area in Haiti but not to the Trinchera Formation in the Azua Basin. The samples of "Trinchera" strata evaluated by Doreen (1975) were collected

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. - v j oi T 1 to Pliocene uppermost Miocene (?) MclaughEnand Bold (this paper)(this Bold O s tra c o d e s T i Mocei Bold (1975) I I 1 NN4 NN11 Brouner(1665) Nannofosslls and others (1962) MOfler in Hju-Duval in Hju-Duval MOfler I T t n s t "f N12 N18/19 N15/16 N ie/i9 N18/19/20 N14 to N16 McLaughlin andMcLaughlin Bold (this paper) I T (N6orN7) L Mocene Doreen (1975) M. Mtoeeoo (N9) M. Foramlnlfera i I I I 1 T Ijabm ah M. MoceneM. Mfcxeo M. Bowin (1975)Bowin L to M U o c e n e Figure 3.5 - Comparison of Azua Basin biostratigraphic studies biostratigraphic Basin Azua of Comparison - 3.5 Figure t I I Miocei U. U. Oligocene U. OBgocene M. M. Oigocene Bermudez (1940) Fm. Fm. Fm. Fm. Mbr. u n its L ltho* VlaFm . Trinchera Gajo Largo Som brerito Ouita Coraza Arroyo Blanco stratigraphic

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in that area. The strata referred to as "Trinchera" in the region east of Banf (formerly Trujillo province) were deposited in a basin distinct from the Azua Basin, cannot be traced between basins, and are part of a finer-grained sequence.The determination (by L. Tjalsma) in Bowin (1975) appears to be based on the presence of Globorotalia fohsi lobata in well samples of these strata from near the village of Yaguate east of Banf. The ostracodes of the Enriquillo and Azua Basins were studied by van den Bold (1975a) in a biostratigraphic survey of southern Hispaniola. The Angostura and Las Salinas Formations were interpreted as spanning the upper Miocene to lower Pliocene in the Enriquillo Basin. These are unconformably overlain by the Jimanf Formation, which was placed in the upper Pliocene. The faunas were suggested as indicative of fluctuations between brackish-water, nearly normal-marine, and hypersaline conditions. In the Azua Basin, ostracodes present in the Arroyo Blanco Formation were determined to show a transition from shallow-marine to brackish-water conditions and interpreted as late Miocene in age. The first integrated biostratigraphic and structural study was carried out by Biju- Duval and others (1982). In the study area, a long road section was measured along the Azua - Barahona highway and more than 100 samples were dated using nannofossils. These workers did not attempt to correlate their results to the biostratigraphic schemes of previous workers. Masters theses by Cooper (1983) and Breuner (1985) included several additional determinations based on planktonic foraminifera, by E. Robinson, and on nannofossils. Detailed sedimentologic studies in the basins are also lacking, except for the unpublished theses of Cooper (1983) and Breuner (1985).

Methods and Materials

This paper is part of a study of the foraminifera and ostracodes of the southwestern Dominican Republic carried out by the authors and B.K. Sen Gupta at Louisiana State

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University, with the cooperation of P. Mann of the University of Texas Institute of Geophysics and of the Diieccidn General de Minerfa of the Dominican Republic. Fieldwork and micropaleontologic sampling were conducted by the authors during four excursions between January, 1985 and April, 1988. Ostracodes were examined in additional material supplied by P. Mann and by R. Maddocks (University of Houston), as well as samples collected by the Dominican Seaboard Oil Company, which are now curated at the Paleontological Research Institute (Ithaca, NY). Particular attention is given to the geology of the Azua Basin in this paper. The shoaling, bathyal to nearshore Neogene sequence there is widely exposed and is an exceptional setting for an integrated foraminiferal / stratigraphic basin evolution study. Both the stratigraphic range and outcrop distribution of the Enriquillo Basin strata are narrower than in the Azua Basin. However, the Neogene brackish-water and shallow-marine ostracode localities of the Enriquillo Basin are probably the best in the Caribbean region (see Bold, 1975a) and significant results are presented here. The biostratigraphy of the Neogene marine sequence of the Azua Basin is based on planktonic foraminifera. They are most abundant in the lowest part of the sequence (Sombrerito Formation) and are less common in the upper part (Arroyo Blanco Formation). The planktonic foraminiferal biostratigraphy is detailed in McLaughlin (in press) and based on the zones of Bolli and Saunders (1985). Approximate "N-zones" of Blow (1979) cited are based on the correlations of Bolli and Saunders (1985). A reference table of the species ranges used for these determinations is presented in Fig. 3.6. Southern Hispaniola is one of the most important areas in the Caribbean for the study of Neogene brackish-water and shallow-marine ostracodes. These forms are biostratigraphically useful in the Enriquillo Basin sequence and upper Azua Basin sequence, and important new information is reported in this study. The ranges of ostracode species in Caribbean region shallow marine and brackish water deposits have been indirectly correlated by Bold (1975a,b,c; 1981; 1983; 1988) to planktonic

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CpiJlU cUI&pUVJ izopniujpg eiiojoiEACio ejoiiuou3Tiuiji5ijs?H BJOJ'UOgOiSOBJd EUU8&USCH euiinumaseqoiuinui fiisooiiduipiojaeqfls gisooiieuipiojaeuos epunisip sisooiiauipiojaEuQs eiEQOI'Q eunnQJO ESJOAlun BuiinQJQ euoiisuFJi euiinqjoaajd cjidsnic cutipenpOQOiD s uawmep BuupenboooiD eEiucOjem ei|Ciojoqo0 5ISU8E1S03B EilEIOJOQOin . 0 . IIWBU8UJ B'lelOJOQOlO i s upjeuaai eiieipjoqoio npJEuaojOEJO e'leiojoqoio s

u jj oiuejqujos

Figure 3.6 - Chart showing ranges of species identified in this study, based primarily on Bolli and Saunders (1985) with additional information from Kennett and Srinivasan (1983). The N-units are the Neogene zones of Blow (1969,1979) as positioned by Bolli and Saunders. Age ranges of stratigraphic units are noted based on faunal content.

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foraminiferal zones through comparison with the planktonic foraminiferal biostratigraphy of over- or underlying open marine strata. The ostracode zonation and its approximate correlation to planktonic foraminiferal zones (Fig. 3.7) follows that proposed in Bold (1983), with the emendation (Bold, 1988) that the base of the Radimella confragosa zone lies near the top of the Globorotalia humerosa zone (N17). Pre - Arroyo Blanco formations could not be placed in this zonation as they do not represent shallow-marine or brackish- water environments. The recognition of foraminiferal biofacies is based mainly on the occurrences of twenty-one benthic foraminifera species (or species-groups) of relatively well-understood bathymetric significance (Table 3.1). Their ranges within the stratigraphic sections are used to resolve the paleobathymetry of the deeper-marine units. Percentages, where cited, are based on sample counts of approximately 300 specimens. In the shallow- to marginal- marine strata, paleoenvironmental determinations are based on ostracodes. The environmental significance of many of the ostracode species is treated in Bold (1975a). Lithofacies analysis is based on study of outcrop sections, including measured sections in the Trinchera and Arroyo Blanco Formations, and on comparisons with the facies models of Mutti and Ricci Lucchi (1972), Walker (1984) and Selley (1970). Petrographic analysis of sandstones from the Trinchera Formation is based on counts of 300 grains and classified according to the scheme of Dickinson and Suczek (1979) and Graham and others (1976).

SOMBRERITO FORMATION

The Sombrerito Formation is a unit of pelagic limestones, marls, and shallow-marine carbonate debris flows. It is distributed from the south flank of the Cordillera Central in the north to the Sierra de Bahoruco in the south. This study focuses on outcrops of the

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Planktonic Ostracode zonea foraminifera zones shallow-marine subzones brackish water

Pleistocene 22/ Gr. iruncatulinoides Radimella wantlandi 23

Cyprideis salebrosa Gr. tosaensis 2 0 / 21 Gr. mlocenica P liocene Radimella contragosa 19 Cyprideis Gr. margaritae subquadraregularis 18 Radimella ovata

C. pascagoulaensis- Gr. humerosa C. subquadraregularis Coquimba congestocostata

16/ 17

M iocene Gr. acostaensis

Cyprideis Procylhereis? pascagoulaensis deform is

15 Gr. menardii

Hermanites 14 Gr. mayeri hutchlsoni

Figure 3.7 - Ostracode zonation of the post-Eocene part of the Caribbean Cenozoic (from Bold, 1988, text-fig. 2; emended from Bold, 1983, fig. 6). Shallow-marine zones are indicated on the left-hand ostracode column with subzones to their right; brackish water zones are listed on the far right. Taxon Range Zones are the observed stratigraphic range of the nominate species and are bounded on top and bottom by solid lines in the columns. Partial Range Zones, bound on top and/or bottomby dashed lines, are that part of the range of the nominate species characterized either by co-occurrence of other taxa (Assemblage Zone) or by the absence of certain other taxa (Interval Zone). Suggested approximate correlation of ostracode zones with planktonic foraminiferal zones, are given based on comparison of ostracode fauna of Antillean shallow-marine and brackish-water strata with the planktonic foraminiferal faunas of under- or overlying open-marine strata. Planktonic foraminiferal zones indicated by N (1-23) or P (18/19) are those of Blow (1969, 1979), whereas those indicated by species name are the zones of Bolli and Saunders (1985).

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Tnxgn . Bsthvffletrv «id remarks 1. Laiicarinina pauperata Reported from >205m (H ) end 300m (9), most common in lower bdhyal zone, in dm Gulf of Mexico; middle and lower bathyal forms are larger (-3mm) than the specimens noted here (10); >200m, mostly 550-3000m in North Atlantic (3,4,11); >200m, mostly 1200-3500 m off California (3,4).

2. Osangularia mcxicana Similar to O. culter, which is >600m in the Gulf of Mexico (11).

3. Karreriella bradyi 150-800m in the Gulf of Mexico (10), 100 to 3000m in the North Atlantic (3. 4, 12).

4. bfelonis pompilioides Specimens identified are inflated Af. pompiiioides (^soldanii) of van Morkhoven et al. (1986), closer to forma rphareoides than to the compressed M. barleeanum form; they probably inhabited the upper bathyal zone in the Miocene (5, 6) rather than the greater depths it characterizes today.

5. EggereUa propinqva >400m in the Gulf of Mexico (9)

6. Siphonina temiicarinata Characterized as outer neritic to middle bathyal, most commonly bathyal, UDL estimated at about 100m (7). Similar to modem carinate Siphonina bradyana which is found at 45-700m in the Gulf of Mexico (10).

7. Pyrgo murrhina In Gulf of Mexico, noted as >45m (9), mostly middle bathyal to abyssal, >600m (7); deeper than 1200m off the western coast of Mexico (2). Similar to P. deprtssa.

8 . Uvigerina hispida Characterized as >1000m (10) in the Gulf of Mexico, or as a bathyal species, 200-2000m (7); typical of 2000-2500m off Punto Arguello, California (1).

9. Cassidulina subglobosa Wide ranging bathymetry, found up to 75 m, mom common and larger @>200m (10) in the Gulf of Mexico; characteristic of >130m, most commonly 500-700m, in the Pacific off Central America (14).

10. Cibicides wuellerstorfi Reported >500m (9) and 700m (11), but most common below 3000m; >630m in the North Atlantic (3. 4, 12).

11. Siilostomella spp. Significant numbers (>5%) noted typical of lower bathyal depths (3).

12. Oridorsalis umbonaius In the Gulf of Mexico, >65m, mostly >80m (11); in the North Atlantic, > 60m, predominantly 1500-3500m (3, 4, 12); characterizes 1300-3200m range off El Salvador (14).

13. Pullenia butloides Predominantly middle-lower bathyal; > 65m in Gulf of Mexico (11); > 150m in the North Atlantic, mostly 500-2500m (3, 4, 11); >175m off California, 2©00-2600m in Catalina Charnel (8), mostly 1200-3500m (3,4); found below 1300m off Panama (2) and El Salvador (14).

14. Sphaeroidina bulloides Small specimens up to -100m in Gulf of Mexico and North Atlantic, most commonly middle-upper bathyal (7).

15. Uvigerina sp. cf. Costate species similar to U. peregrina. In the Gulf of Mexico, U. peregrina is found >S0m, V. peregrina common >100m, most abundant 500-1850m (11); off Pacific Coast of Central America, most frequent >1000m (2).

16. Uvigerina hispidocostala Rare <300m in the Gulf of Mexico (10, 11), found to 1000m.

17. Hoeglundina elegans Ranges from outer neritic to abyssal in the Gulf of Mexico and the North Atlantic^nost common and largest at middle bathyal and greater depths (10, 11); >800m, most frequent around 1500m, off Pacific Coast of Central America (2); off San Diego, living specimens most abundant around 1000m (15).

18. Uvigerina carapitana Fossil species interpreted as bathyal, 200-2000m (7).

19. Cancris sagra Reported (as Cancris obtonga) in the Gulf of Mexico from 22-200m, mostly <120m (11), characterizes 20-90m depth off the Pacific Coast of Central America (13) and California (6).

20. Elphidium spp. Typically <100m; include: E. poeyanum, reported mostmimerous in Gulf of Mexico lagoons, bays, and estuaries, also less numerous on the inner shelf; and £ . lanieri, which is found in Gulf of Mexico carbonate-rich areas (13).

21. Ammonia In these samples, mostly var. typica\ in the Gulf of Mexico, it is a lower eimarine-inner shelf form, parkinsonianum <120m and moat abundant <60 or 70m (11, 13).

Table 3.1 - General bathymetric significance of some benthic foraminiferal species from the southwestern Dominican Republic. Samples are keyed to Figures 10 and 11. References: (1) Bandy, 1953; (2) Bandy and Amal, 1957; (3) Berggren and Haq, 1976; (4) Berggren and others, 1976; (5) Hasegawa, 1984; ( 6) Ingle, 1980; (7) van Morkhoven at al., 1986; (8) Natland, 1933; (9) Parker, 1954; (10) Pflum and Fierichs, 1976; (11) Phleger, 1951; (12) Phleger, Parker, and Peirson, 1953; (13) Poag, 1985; (14) Smith, 1964; (15) Uchio, 1960.

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Sombrerito Formation in the Sierra de Neiba. The type section is located on the southeast end of that range (loc. 5, Fig. 3.1).

Biostratigraphy

Fine grained beds in the Sombrerito Formation are rich in calcareous plankton remains and include up to 25 weight percent of planktonic foraminifera. The faunas indicate that the unit ranges in age from latter early Miocene in the San Juan-Upper Rio Yaque del Sur Valley to the earliest part of the late Miocene in the Azua Valley (Fig. 3.6). Lower Miocene strata outcrop along Rfo Los Baos south of San Juan. (loc. 1, Fig. 3.1). Globigerinatella insueta and Globigerinoides bisphaericus occur throughout the section. Praeorbulina transitoria is present in all but the lowermost samples from the section, and Praeorbulina sicana appears in the highest sample. These occurrences suggest that the interval sampled at Rfo Los Baos spans the upper half of the Globigerinatella insueta zone (upper N7). Slightly younger exposures of the formation are found to the southeast at the type locality, Arroyo Sombrerito (loc. 5, Fig. 3.1). The presence of Globorotalia fohsi peripheroronda lower in the section, G. f. peripheroacuta higher in the section, and Globorotalia praemenardii throughout, justifies its placement in the middle Miocene Globorotalia fohsi fohsi chronozone (N10). In the lower Rfo Yaque del Sur Valley, the Sombrerito Formation crops out in two areas near Canoa. Samples taken near the travertine quarries on the Canoa Dome (Iocs. 112 and 113, Fig. 3) are characterized by large specimens of the middle Miocene Globorotalia fohsi lineage. These forms are transitional between the two most advanced members of the lineage, G. f. lobata and G. f. robusta. suggesting that the samples lie in the G. f. robusta chronozone (N12). The rhythmically-bedded calcareous sandstones of the Gajo Largo Member comprise the other area of outcrops near Canoa (Iocs. 114 and 115, Fig. 3) and

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are found to span the middle-upper Miocene boundary. The lower part is correlated to the Globorotalia maveri zone (N14) based on the presence of the nominative taxon, which has its last-appearance datum (LAD) at the top of the zone, and of Globigerina nepenthes, which has its first-appearance datum (FAD) in this zone. The presence of small, four- chambered forms of Globorotalia acostaensis in the upper Gajo Largo strata indicate placement in the lower part of the Globorotalia acostaensis chronozone. In reality, the apparent gaps between the two Gajo Largo samples and between the Canoa Dome and Gajo Largo strata may represent insignificant intervals. The missing biostratigraphic zones, the Globorotalia menardii (N15) and Globigerinoides tuber (N13) zones, are both considered difficult to recognize in the Caribbean region (Bolli and Saunders, 1985). On the north flank of the San Juan Valley, beds considered equivalent to the Sombrerito Formation contain a shallow-marine ostracode assemblage belonging to the Procvthereis? deformis -Triebelina crumena subzone (Bold, 1983, p.409). Indirect correlation to planktonic foraminiferal zonations (Fig. 3.7) suggests a probable equivalency

to the lower Miocene Catapsvdrax stainforthi zone (N 6).

Lithofacies

The Sombrerito Formation is best exposed in the Rfo Los Baos section south of San Juan (loc. 1, Fig. 3.1). The interval is of about 65 m thickness and shows sedimentologic features typical of the formation. The section is characterized by blue-gray marls interbedded with pink, indurated, calcareous sandstones, with the marls comprising about 90% of the strata. The sandstones are composed mostly of shallow-water carbonate debris and are graded, mostly from coarse-grained to fine-grained sand. Sandstone thicknesses range from 5 to 80 cm, but are most commonly 20-25 cm. Some display convolute lamination, suggesting very rapid deposition from suspension. The intercalated marls, usually of 2 to 3 m thickness, are rich in calcareous plankton remains and deep-water

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benthic foraminifera. Similar strata are exposed at sampling localities in the type section at Anroyo Sombrerito (loc. 5, Fig.3.1) and at the travertine quarries near Canoa (Iocs. 112 and 113, Fig.3.3). The Arroyo Sombrerito section is typified more by buff marls and pelagic limestones than by blue-gray marl. The Canoa quarry outcrops are dominated by more indurated, buff pelagic limestone. The Gajo Largo Member of the Sombrerito Formation (Iocs. 114 and 115, Fig.3.3) is characterized by marls with regularly-bedded calcareous sandstones (Cooper, 1983; Mann and others, this volume). However, these sandstones are not as closely spaced as the overlying siliciclastic Trinchera turbidites, nor are they organized into distinct patterns. All of the above characteristics suggest that deposition of the Sombrerito took place in a deep-marine basin marked by intermittent calcareous turbidity currents that carried debris from the shelf-edge. Overall, this interpretation agrees favorably with the distal basin plain turbidite facies of Mutti and Ricci Lucchi (1972).

Biofacies

Benthic foraminiferal species in the marls and chalks of the Sombrerito Formation are characteristic of middle-bathyal and greater depths (Table 3.1; Figs. 3.8 and 3.9). Cibicides renzi is restricted to the Sombrerito Formation and is noted by van Morkhoven and others (19861 to characterize bathval depths. Laticarinina pauperata and Osangularia mexicana are also typical of the Sombrerito Formation, ranging only a short distance above the top of the unit. These forms are most common at middle bathyal and greater depths (see Table 3.1 for references). Several lines of evidence suggest placement of the Sombrerito samples in the upper part of the lower bathyal zone. Cibicides wuellerstorfi constitutes up to 3% of the benthic foraminiferal fauna in some of the samples. Although scattered occurrences of this species have been noted in the middle bathyal zone, it is most common at lower bathyal and greater

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Q .C poC < o 5 •E II o § *3 12 E5 ^5;g -ciC3 2500 o * .«= ! .«/* "3 .*3 £ * Samples i s c Q) D • DM1-4 5 5 .O ) .V) •138 r l -Si - *C IP £ £ I t'iE 2000 S - cm DM1-3 :§ :i o.' s , g > 137 .*=C o . 5 5 •§" o .§ % -cr l_r 136 c g .§ op 1500 .g>Oj ■8 6 g Aio K %■ <■0 ir> . g ■ S 1000 C s =g

500 129 131

N15? 0 t o 124 125 os ^ CD < S oee

~ t |1 limestone marl I | 1 mudstone sandstone f0°°o°°^ conglomerate

Figure 3.8 - Composite stratigraphic section for the upper Rio Yaque del Sur - San Juan Valley showing the range of baihymetrically-useful forms with the paleoenvironmental interpretation that these suggest for the section. Species numbers are keyed to Table 3.9.

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FORMATION i / ARROYO BIANCO a i ■ 19. Cancris sagra 19. Cancris ■ spp. 20. Elphidium ■ 21. Ammonia parkinsoniana ■ subglobosa 8. Cassidulina inner neritic-nearshore-marginal marine (sm all) •17. Hoeglundina •17. elegans Hoeglundina FORMATION QUITA CORAZA outer nerilic 15. sp. 15. Uvigerina cf. U. peregrina 14. Karreriella bradvi 14. Karreriella 5. lenuicorinoto Siphonino

•jj upper N18 or NT9 1. Oridorsolis umbonotus 1. Oridorsolis 13. bulloides 13. Sphaeroidino / VI thickness (meters) vl Uvigerina hispida Uvigerina 6. Pyrgo munhina 4. Eggerella propinqua 4. Eggerella 9. 9. wuellerstorfi Cibicides -7. ------Stiloslomellids ■10. lower N18 16. hispidocostafa 16. Uvigerina < 18. caropitana 18. Uvigerina <

l/i -l/i - • • • • TRINCHERA FORMATION TRINCHERA v j vO middle bathyal upper bathyal N17 upper N18, N19, or N20 Osongulario mexicana Osongulario 2. 2. Zo 5 (large) w w -t* N12 3 ro S ’ SOMBRERITO ra FORMATION 3 a a lower bathyal? tn c r m S 'l _ o « 5 * 1 s n c» £S o. r» 3 ^ ttO c. 0-^g.TO o> 55 S* CD cr. 3CD § •8 01 B D* c r o cr < N »N S a s i - g l : s * 0 o*2 Miff i s'S'S £ o r“® |i r“® 8 N |Wf&

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depths (Pflum and Frerichs, 1976). Stilostomellids such as Stilostomella and Siphonodosaria are a conspicuous constituent of the fauna and include ornamented forms. Abundant stilostomellids (>5%) suggests depths of over 1000 m (Berggren and Haq, 1976), and ornamented stilostomellids may be typical of the lower bathyal - middle bathyal transition (Bandy and Rodolfo, 1964; Ingle, 1980). The large size of species such as Laticarinina pauperata, Eggerella propinqua, and Sphaeroidina bulloides suggest lower bathyal depths (Pflum and Frerichs, 1976), as does the generally higher diversity agglutinated fauna relative to higher strata

Depositional Environments

Lithofacies and benthic foraminiferal biofacies suggest that the Sombrerito Formation was deposited in a lower slope setting open to the Caribbean Sea. Downslope transport is evident in the shallow-marine carbonate turbidites and debris flow deposits, suggesting strong development of carbonate shelf and reef-associated deposition on the southern Hispaniola coast. However, siliciclastic sediments are conspicuously absent throughout southern Hispaniola during the time of deposition of the Sombrerito Formation.

TRINCHERA FORMATION

The Trinchera Formation is a unit of mudstones and turbidite sandstones that marks the onset of siliciclastic sedimentation in the Azua Basin. The unit is recognized from the San Juan area in the northwest, seaward to the Azua and lower Rfo Yaque del Sur areas (Fig. 3.1). A stratigraphic contact between the Trinchera Formation and the underlying Sombrerito Formation has not been observed in our field studies. In most cases, the juxtaposition of these two units occurs along fault planes. The type section is located at the

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bluffs at La Trinchera in the upper Rfo Yaque del Sur Valley Goes. 2-4, Fig.3.2) and lies in the lower part of the formation.

Biostratigraphy

Planktonic foraminifera indicate that the Trinchera Formation extends from near the middle-upper Miocene boundary to the uppermost Miocene in the upper Rfo Yaque del Sur- San Juan Valley (Fig. 3.2) and from the uppermost Miocene to the lower Pliocene in the lower Rfo Yaque del Sur Valley sections (Figs. 3.3 and 3.6). Although reworking of older nannofossils has been noted to be a problem in this formation (Biju-Duval and others, 1982; P. Cepek, oral comm), the planktonic foraminiferal faunas appear to be relatively unaffected.

The Arroyo Salado section (Iocs. 6a to 13, Fig.3.2) is one of the more complete of the northwestern part of the study area. The oldest strata crop out in the lower reaches of

the section (Iocs. 6a to 8). These are placed around the middle-upper Miocene boundary, constrained biostratigraphically by the presence of Globorotalia lenguaensis. which is known to disappear within the Globorotalia acostaensis zone (N16), and by the absence of Globorotalia maveri. which disappears before the base of Globorotalia menardii zone

(N15). No outcrops are present in the middle part of the section, between Iocs. 8 and 9, which is apparently equivalent to the soft marls present at the Trinchera type locality to the southeast. The upper part of the section is considered uppermost Miocene, equivalent to the Globorotalia humerosa zone (N17), with Candeina nitida present but Pliocene markers such as Globorotalia margaritae absent. To the southeast, at and around the type locality near La Trinchera (Iocs. 2-4, Fig. 3.2), soft marls and mudstones that outcrop at the Trinchera bluffs and in highway and canal cuts contain upper Miocene faunas. The samples from La Trinchera are placed in the Globorotalia acostaensis chronozone (N16) based on the presence of the nominative taxon

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and on the absence of Globigerinoides obliquus extremus. Candeina nitida.. and Globorotalia humerosa. which defines the base of the overlying zone of the same name. Several samples from canal cuts to the southeast include the former two taxa but are below the range of the Pliocene marker Globorotalia margaritae and are referred to the Globorotalia humerosa chronozone (N17). In the lower Rfo Yaque del Sur Valley (Fig. 3.3), the Trinchera was sampled in generally continuous sections near Fondo Negro (the Azua-Barahona highway Iocs. 72 -76 and 116-123, and sites 58-71 in Arroyo El Puerto) and near Quita Coraza (Arroyo de Bergal sites 30-38, Arroyo del Bao Iocs. 39-42). Important foraminiferal datums include the first-occurrence (FO) of Globorotalia margaritae at about 300 meters above the Trinchera-Gajo Largo contact in the highway section (loc. 117), and the first-occurrence of Globigerinoides ruber (site 75) near Fondo Negro, about 200 m below the top of the Trinchera. The lowest part of the section, below the FO's of Globorotalia margaritae along the highway northeast of Canoa, is placed in the uppermost Miocene, in the upper Globorotalia humerosa chronozone. Between the FO’s of Globorotalia margaritae and Globigerinoides ruber, the Trinchera is equivalent to the lower part of the Globorotalia margaritae margaritae subzone. Above the FO of Globigerinoides ruber, useful deeper-dwelling planktonic forms such as Globorotalia margaritae are lost due to shoaling, so the biostratigraphy is less precise. The interval between this datum and the top of the formation is correlated to to the upper part of the G. margaritae margaritae subzone or possibly into the G. margaritae evoluta subzone. The Quita Coraza section is not quite as rich, but contains scattered occurrences of Globorotalia margaritae to near the top of the formation, and is equivalent to the upper part of the Fondo Negro section. The age of samples from Rfo Via near Azua (loc. 2, Fig. 3.1) cannot be as precisely determined due to the general paucity of faunas. Based on the presence of Candeina nitida in the lowest sample and the range of Globigerina nepenthes through the formation, they

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appear to be equivalent to the upper Miocene Globorotalia humerosa zone (N17) or the lower Pliocene Globorotalia margaritae zone (N18 and/or N19). These foraminifera-based ages are slightly younger than the ages assigned by Miiller (Bijc-Duval and others, 1982) on the basis of nannofossils. An upper Miocene position, in zone NN11, is reported for the Azua - Barahona highway section near Fondo Negro.

Lithofacies

Exposures of the Trinchera Formation were studied in roadcuts along the Azua Barahona highway, which cuts obliquely across regional strike between Fondo Negro and Canoa. The sequence is well exposed, relatively complete and uninterrupted, and easily accessible, making it an exceptional site for the study of turbidite facies development in the Azua Basin. Therefore, it is treated in much more detail than any of the other Trinchera sections. Four representative sections within the formation were measured in detail, numbered stratigraphically upward from 1 through 4. These sections are figured in Fig. 3.10 and their localities are noted on Fig. 3.3. Study of these four sections and other exposures indicate that the Trinchera Formation is a prograding turbidite fan sequence, exhibiting an upward transition from more distal outer fan facies associations to more proximal inner fan facies associations. Section 1- Section 1 outcrops on the northwest side of the Azua - Barahona highway just south of its intersection with the old Tamayo road (loc. 116, Fig. 3.3). It is 71.4 m thick and characterized by rhythmically interbedded mudstones and thin sandstones, with a sandstone percentage of about 20% (Fig. 3.10a). Sandstone bed

thicknesses are between 1 to 30 cm, most often around 8 to 10 cm, and are generally graded with grain sizes ranging from medium to very-fine. Bouma T ^ and Tc_e

sequences (Bouma, 1962) are most common, and convolute bedding is evident near the top of some beds. The sandstones range from soft, muddy, olive brown to hard, calcareous, dark gray-brown beds.

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Figure 3.10 - Measured sections from the Trinchera Formation turbidite sequence. Figure 3.2 includes: a) section 1, which displays characteristics comparable to outer fan facies, such as thinning-upward sequences and flute casts; b) section 2 , which is comparable to middle-fan facies associations; c) section 3, which is also comparable to middle-fan facies associations; and (d) section 4 from the upper part of the Trinchera Formation turbidite sequence, which contains many features typical of upper fan facies associations including thickening-upward cycles, pinching out of sandstone beds, and chaotic deposits.

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R l 4

60-

100- 19899587 1 Fining/thinning 4 0 - 4 0 - upward sequence

1 I 7 "7 Coarsening/thickening I upward sequence

2 0 - 20 - I lf T 20 -

369^152965

0 - 0 - 0 meters B meters D

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Six thickening/coarsening-upward sequences are evident in this section. Each shows a transition from mudstone intervals with widely spaced, very-thin (1 to 5 cm), fine grained sandstones to sandier intervals with graded, medium to fine grained sandstones of up to 30 cm thickness. Bedding is even, with flat bases and lateral continuity across the outcrop (Fig. 3.11a). Sole casts are common (Fig. 3.11b). These features are comparable to Facies D of Mutti and Ricci Lucchi (1972). Facies D is associated with the slightly sandier Facies C in outer fan settings whereas it is associated with Facies G in the basin plain. (Table 3.2) Therefore, these deposits probably represent deposition near the outer limits of the submarine fan. The Section 1 features are also compatible with lower fan facies in Walker (1984). Section 2 - Section 2 is exposed on the northwest side of the Azua - Barahona highway at the 49 km marker (loc. 119, Fig. 3.3). It is composed of 48 m of interbedded mudstone and sandstone, with the sandstone comprising 23% of the interval (Fig. 3.10b). The mudstone is light olive-green to tan in color. The sandstones are durable, light olive- tan in color and often covered with a light orange stain. They include numerous very thin (1 to 5 cm) fine grained beds and fewer thicker (up to 55 cm), graded, medium- to fine grained sandstones. The beds generally exhibit base-missing Bouma sequences, Tb_e in thicker and Tc_e in thinner beds, with flaggy tops that result from weathering of aligned plant fragments in the T^ interval.

With only two exceptions (at 33 and 36 m), the sandstones are fairly evenly-bedded and laterally continuous. Several include zones of mudchips suspended near the tops (see at

7 and 8 m). Although not very distinct, two positive cycles (fining/thinning upward) can be identified.The characteristics of Section 2 are compatible with those of Facies D of Mutti and Ricci Lucchi (1972), part of middle and outer fan facies associations (Table 3.2). Fining/thinning upward cycles are noted as common in the middle fan. Apparently, section

2 can be referred to as a deposit from the outer pait of the middle fan, with features

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Figure 3.11 - Photos of outcrops of the Trinchera Formation, Azua - Barahona highway: a) Section 1 in the lower Trinchera Formation, exhibiting thickening-upward sequences typical of outer fan facies; b) Flute and load casts on the base of a sandstone from Section 1; c) Section 4 - thinning-upward cycles evident are common in inner fan facies, also note the shallow channel sandstones and pinching out of beds; d) Chaotic deposit in Section 4, large blocks, mudballs, and cobbles are suspended in a dark gray muddy sand matrix.

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Figure 3.11

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. to CD Salado section (RD6a-8, Fig.2) Example lower part of Quita Coraza Formation upper part of Trinchera Formation; upper parts and Arroyo Salado section (RD12-13,middle part Rg. of Trinchera 2). Formation; middle parts of of Azua-Barahona highway section (RD74, Fig.3) highway section (RD119 and 123, Rg.3), middle part of Arroyo Salado section lower (RD9a-11, part of Rg.2). Trinchera Formation; lower part lower part of Trinchera Formation (transitional to of highway section (RD116, Rg.3), lower part of Arroyo outer fan) facies (after Mutti and Ricci Lucchi, 1972, Table 3.1). Table 1972, Lucchi, Ricci and Mutti (after facies Table 3.2 - Summary of criteria used to interpret depositional environments for turbidite turbidite for environments depositional used to Table interpret of3.2criteria - Summary General characteristics Massive plane-parallel stratified pelites (G) in places with discordant surfaces from slump scarsbodies and/or (A), chaotic sediment(D, E) horizons andonlap more (F), thinrarely shaleythick and Parallel-beddedor gradedsandy turbiditesturbidites.pelites (G) cut by thick sandstone bodies (A, B) on the slope; the pelites can include channelized sandstone and overbank turbidites (D, E) may also be present. megasequences (fining/thinning-upward) are evident. Characterized by thin channel and overbank turbidites (0, E) Predominantly composed of thin turbidites deposited by low- which represent filling of large subm arine valleys; thin channel with coarser, lenticular channel-fill turbidites (A, B); positive density currents (D) and upward) broadly are lenticular typical. "classical" channel Thin turbidites usually deposited dominant, by with low-density thin horizons currents of hemipelagites (D) are (G) often turbidites; negative megasequences (thickening/coarsening- present and rarely dominant. Environment slope inner fan middle fan outer fan basin plain

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transitional to the lower fan. The section is probably also equivalent to the "smooth portion of suprafan lobes" that Walker (1984) notes for middle fan facies associations. Section 3 - Section 3 was studied just south of the 47 km marker along the Azua - Barahona highway (loc. 123, Fig. 3.3). It measures 22.75 m in thickness and is coarser grained than either of the lower sections, with about 42% sandstone (Figure 3.10c). The prominent sandstones are predominantly bluish to greenish gray in color, 10 to 30 cm thick, and slightly less indurated than those of Section 2. Most are graded from medium- to fine-grained and are flaggy towards the top, like those of the lower-middle section. They are separated by blue-green, weathering to tan, mudstone interbedded with very thin (1 to 5 cm) sandstones. Overall, the sandstones do not attain thicknesses as great as those in Section 2. Bouma Ta_e and Tfo_e sequences can be identified, the latter being more

common, associated with deposition by waning turbidity currents. In marked contrast to either of the lower sections, most of the sandstones in this section show lateral variations across the outcrop. Many of the thick- to medium-bedded sandstones are broadly lenticular, thickening or thinning across the outcrop, and some of the thinner sandstones pinch out. However, no lenticular channel-fill deposits are present in this interval. No distinct thinning- or thickening- upward bedding cycles are apparent. These features fit the Facies E of Mutti and Ricci Lucchi (1972), which is characteristic of the middle-fan subassociation (Table 3.2) and probably indicates a transition to the channeled part of the fan in this section, similar to the channelled suprafan lobes of Walker's (1984) middle fan association. These strata probably represent overbank deposits spilled out of shallow-marine channels and reflect a more proximal setting than Section 2. Section 4- Section 4 is the most coarse-grained and thickly-bedded interval of the study (Figure 3.10d). It is located in the deep roadcut approximately 1 km southwest of Fondo Negro (loc. 74, Fig. 3.3). About 55% of the 113.7 m thick section is composed of sandstone with bed thicknesses of up to nearly 2 meters. The sandstones are little

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unindurated, mud-rich, and olive-tan, but otherwise variable in their characteristics. Grain sizes range from cobble to fine sand; mud chips and clasts are also very commonly suspended in the upper portions of the sandstones or along planes of amalgamation. Grading is evident in the thinner beds, from medium- to fine-grained, reflecting deposition by waning currents, but sedimentary structures are difficult to identify due to the softness of the sands. Both full and top-missing Ta_e sequences are seen. We note, however, that sedimentary divisions noimally described as Ta may be better described

through consideration of features associated with deposition by high-density turbidity currents (Lowe, 1982). For example, apparent dish structures noted in this section (47 m) suggest rapid sedimentation of suspended sediment out of a high density turbidity current

(Lowe's S 3 division). Reverse to normal grading is found in thicker, coarser beds (36 m);

this indicates transport by a traction carpet that was initially supported by grain collision

generated dispersive pressure (S 2 ) that gave way to decelerating turbidity support. Flame

structures are also evident (at 40 and 70 m). Abrupt bed thickness variations are evident across the outcrop and erosional bases are common. In some cases, the convex-downward beds appear to be channel-fills that follow topographic lows, with their thickest points on the order of ten meters away from those of underlying lenses. Total or partial amalgamation of beds is very common with rip-up clasts lining the planes between thinner, finer beds or scours between the thicker, coarser beds (Fig. 3.11c). Fining and thinning upward sequences are conspicuous across the section, both on a small and a large scale. Larger sequences measure 10 to 20 m in thickness and may contain smaller sequences of 2 to 5 meters (Fig. 3.10d). Chaotic deposits are also a conspicuous part of this section. The most prominent is a 5 m thick debris flow deposit at 72 m above the base of the section (Fig. 3.10). Suspended within a matrix of dark gray-blue, very muddy fine-grained sand, the components include pebbles, shells, and a variety of clasts and blocks of sandstone and mudstone. Pebbles

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range from 2 mm to 1 0 cm in diameter and include tonalite, metaquartzite, gabbro, greenschist, and pink, gray, and red limestone. Gastropod shells and coral fragments are also present. The largest blocks included are contorted masses of interbedded turbidite sandstones and mudstones of up to 2.5 m length, which apparently slid while still unconsolidated. Sandstone blocks are of 10 to 30 cm diameter while mudstone blocks and clasts range from 5 to 50 cm and are more common towards the top of the deposit. The clasts and blocks are rarely in contact and appear to be supported by the matrix, implying plastic behavior that would result from the cohesive strength of the flow (Lowe, 1979). Other chaotic deposits range in scale from a 60 cm thick unit of contorted mudclast-bearing turbidite at 29 meters to, at 56 m, a 4 m thick deposit of contorted turbidite strata that contains pockets of matrix-supported conglomerate. These were probably produced by minor slippages with short travel distances. The thick intervals of mudstone and siltstone noted in Section 4 (Fig. 3.10d) are referable to Facies G of Mutti and Ricci Lucchi (1972), while the contorted deposits and debris flow deposits can be assigned to Facies F. The sandstones of the section are comparable to those of Facies B, and in some cases Facies A, with thick, lenticular beds with occasional mudclasts; these exhibit evidence of deposition by erosive, high-velocity and/or high concentration turbidity currents and grain flows. This association of facies is comparable to the inner fan facies subassociation (Table 3.2) of Mutti and Ricci Lucchi (1972), and the channelled suprafan lobe and upper fan channel-fill associations of Walker (1984). Other exposures- The type locality of the Trinchera Formation is located at the La Trinchera bluffs in the upper Rfo Yaque del Sur Valley (Iocs. 2-4, Fig. 3.2). The strata exposed there are much finer-grained than what is regarded as typical of the formation. Sandstones comprise less than 10% of the section and are found in very thin, laterally- extensive beds, mostly 1-2 cm in thickness (maximum 5 cm). The sandstones are separated by 20 cm to 1 m, averaging approximately 40 cm, of tan marly, foraminifera-rich

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mudstone. This section is dominated by hemipelagic Facies G sediments of Mutti and Ricci Lucchi (1972), suggesting deposition in a distal basin plain setting. Just to the east and southeast of La Trinchera, an approximately 15-20 m thick unit of pink reefal limestone caps a series of hillsides. This unit has been referred to as the "Florentino Formation" (Olsson, 1942, in Bermudez, 1949) and represents a facies of reefal slip-masses in the Trinchera Formation rather than a change to shallow-marine environments above the Trinchera Formation. It is bounded above and below by deep- water strata and exhibits a basal contact that scours into and contorts the underlying mudstones. The presence of these reefal limestones on the shelf edge implies a reduced influence of clastic sediments in this region. This lack of a local clastic sediment supply may explain the predominantly fine-grained nature of the type section of the Trinchera Formation. Thus, these fine grained strata may have been deposited on the lower fan during an interval of reef-growth on the shelf-edge that limited the supply of elastics. The Arroyo Salado section (Iocs. 6a-13, Fig. 3.2) spans approximately 1700 m of the Trinchera Formation. The interval of marl noted at La Trinchera, 4 km to the southeast, is eroded away and does not crop out at Arroyo Salado. Outcrops of strata that lie above and below the level of the type section are more typical of the Trinchera Formation. The lower

part of the section (Iocs. 6a -8 , Fig. 3.2) is characterized by thin, laterally persistent green

to tan sandstones of up to 8 cm thickness in proportions of up to 40%. This part of the section probably represents deposition on the outermost part of a turbidite fan or on the basin plain, and is referable to Facies D of Mutti and Ricci Lucchi (1972). The upper part of the section (Iocs. 9a-13, Fig. 3.2) consists of strata similar to Sections 3 and 4 near Fondo Negro. Much of this part of the section is characterized by thick (up to 2 m), often lenticular and amalgamated, sandstone beds, Facies B, C, and A of Mutti and Ricci Lucchi (1972). These sequences alternate with intervals of interbedded sandstones and mudstones, the sandstones ranging from 2-15 cm in thickness and comprising approximately 50% of the interval (Facies E). Chaotic deposits (Facies F) are present in the uppermost part of the

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section. Based on the criteria of Mutti and Ricci Lucchi (1972), this interval may be characterized as a middle to upper fan succession. Equivalent strata in the upper Trinchera at the Arroyo Las Lajitas section (Iocs. 132-136, Fig. 3.2) are of a similar nature. The upper 500 m of the Trinchera Formation are exposed at Rfo Via near Azua (loc. 2, Fig. 3.1). There the unit includes more conglomerate than in any of the other localities studied. In the lower part of the section, sandstones of several centimeters thickness are interbedded with green silty mudstone, similar to overbank deposits of Facies E (Mutti and Ricci Lucchi, 1972). Above this, thin mudstone and siltstone intervals alternate with thicker channel-fill deposits. The channel fills include sandstones, which may contain mud intraclasts (Facies B). However, the dominant channel fill deposits are thick pebble conglomerate beds (Facies A). The pebbles are often imbricated and average 2-5 cm in length, with a maximum of 15-18 cm. The association of Facies A, B, and E type deposits in the Rfo Vfa section suggests an inner fan setting (Table 3.2). The anomalously high ratio of conglomeratic beds is probably due to the location of this section directly on the south flank of the central mountain belt (Fig. 3.1).

Sandstone Petrography

A series of thirteen samples were collected for petrographic analysis at typical points in the measured Trinchera sections. Six of the most representative of these were picked for compositional analysis by point counting and for evaluation of texture (Fig. 3.12): two in Section 1, DM4-3 and DM4-5; one in Section 2, DM14-2; one in Section 3, DM14-5; and two in Section 4, DM6-1 and DM14-6a. Percentages are based on counts of 300 grains. The grain types in the six samples evaluated were grouped according to the scheme of Graham and others (1976). The compositional trends are shown in the accompanying series of ternary diagrams (Fig. 3.12): a) QFL; b) QmFLt; c) QmPK; and d) QpLyLg. The

fields in which these points plot may be related to typical source terranes and tectonic

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 102 provenances collision orogen com plex subduclion .provenances } f\ * * 1 \ j K Lv • DM 6-1 o DM 14-6A * DM 14*2 ^ DM 14-5 ■ DM 4-3 ° DM 4-5 Q m recycled provenances Q m provenonces mogmatic mogmatic ore provenances \ continental block provenonces recycled orogen Figure 3.12 - Ternary compositional diagrams for sandstones in the Trinchera Formation Formation inTrinchera the forsandstones diagrams compositional - Ternary 3.12 Figure Dickinson in indicated terranes as source typical ofto fields compared and (1976) others turbidite sequence. The grain types were grouped according to the scheme of Graham and and Graham of scheme the to according grouped were types grain The sequence. turbidite 2, section from DM section 14-2 1, from are -5 and 4-3 DM Samples (1979). Suczek and QmPK, d) quartz, quartz, QpLvLs; Q=quartz, Qp=polycrystalline Qm=monocrystalline DM 14-5 from section 3, and DM 6-1 and 14-6a from section 4. section 4. from 3, from and DMand DM 6-1 section 14-6a 14-5 c) FLt, b) a) Qm QFL, lithics, Lv=volcanic L=lithics, feldspar, K=potassium feldspar, P=plagioclase F=feldspar, lithics Ls=sedimentary

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settings as indicated in Dickinson and Suczek (1979) and Dickinson and others (1982). Texturally, these sandstones are generally immature, containing poorly- to (less commonly) moderately-sorted angular grains with a significant amount of mud matrix. Packing is generally fair to good and is best developed in samples with poorly preserved unstable grains that have been compacted; little burial is needed to compact such lithic-rich sandstones, as compared to arkosic or quartzose sands (Dickinson and Suczek, 1979). Grain sizes range from coarse silt size in the lower highway section (DM4-3) to coarse- very coarse grained sand in the upper highway section (DM6-1). This coarsest sample (DM6-1) is notable as the sole sandstone classified as submature, due to moderate sorting and lack of a significant mud fraction. This sample was taken from a reversely graded interval at the bottom of a thick sandstone bed, probably lain down by the traction carpet of ahigh-density turbidity current. Compositionally, the group sampled can be characterized overall as muddy, calcite- cemented, feldspatholithic to lithofeldspathic sandstones with a notable quartz fraction. The coarser grained samples (DM14-5, DM6-1, DM14-6a) are feldspatholithic. Finer grained samples, those with a mean grain size of about 3 <|> and finer (DM4-3, DM4-5, DM14-2), are lithofeldspathic. This trend is consistent with the fact that the dominant lithic grains, volcanic rock fragments, are less stable than plagioclase grains, especially in a subtropical setting such as Hispaniola, and would be eliminated from the fine grain fraction. Similarly, some of the large polycrystalline quartz would also break down into single crystal grains. The sandstone compositions are generally compatible with a dissected magmatic arc provenance. Although they plot in or near the range of modes associated with recycled orogen provenances, particularly of the subduction complex type, on the QFL (Fig. 3.12a) and QmFLt (Fig. 3.12b) diagrams, it is likely that the detritus had lost many volcanic rock fragments and some feldspar to chemical weathering before deposition. Compensating for this effect would shift the compositional ranges of these sandstones toward the field of the magmatic arc provenances of Dickinson and Suczek (1979). The feldspar is exclusively

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plagioclase (QmPK diagram; Fig. 3.12c) and varies within samples from well-preserved twinned crystals to highly sericitized or calcite replaced grains. Commonly some degradation of the feldspar is evident, especially in finer grain sizes. Volcanics and polycrystalline quartz are both well represented as rock fragments, with the former slightly more abundant, whereas sedimentary rock fragments, other than chert, are rare. The volcanic rock fragments are also commonly very weathered and at times hard to recognize; these include volcanic rock fragments rich in fine plagioclase laths; coarser-textured hypabyssal fragments; and tuff fragments. Other mineral constituents include epidote, chlorite, and actinolitic amphibole, occasionally associated with quartz and plagioclase in metamorphic rock fragments, pyroxene, associated with volcanic or plutonic rock fragments, and biotite. Paleocurrents

Paleocurrent indicators in the Trinchera Formation vary among three regions. In the upper Rfo Yaque del Sur Valley, paleocurrent indicators point to a southeastward direction of sediment transport. Twenty-seven measurements taken from sole marks (primarily flute- casts) by Breuner (1985) give a mean direction of 129°. In the lower Rfo Yaque del Sur Valley, our paleocurrent measurements in the Fondo Negro turbidite sequence indicate a predominantly west-southwestward to westward direction. Fifteen measurements from flute, tool, and groove casts in Section 1 range from 241° to 272° > averaging 256°. In the Section 2, nine tool, flute, and scour casts indicate paleocurrent directions from 241° to 292°, averaging 274°. Paleocurrent indicators in the Section 3 are less common and more difficult to measure accurately due to the softness of the beds. A scour on the base of one bed indicates a direction of 251°, whereas two scours on the base of a higher bed were read as 311° and 308°. Directions of two basal scours, rotated to horizontal, from Section 4 were measured as 220° and 284°.

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At Rio Via, sixty-one measurements of the dip direction of pebble imbrication from eight conglomeratic beds were taken by McLaughlin and P. Mann (University of Texas Institute for Geophysics) in the upper part of the Trinchera Formation. These measurements, with a mean of 28°, indicate south-southwestward sediment transport.

Biofacies

The benthic foraminiferal assemblage trends in the Trinchera Formation turbidite sequence reflect a transition from the base of the middle bathyal to the top of the upper bathyal zone. The lower part of the formation was studied in the upper Rfo Yaque del Sur Valley in Arroyo Salado (Iocs. 6a-9b, Fig.3.2), near La Trinchera (Iocs. 2-4, Fig.3.2) and near Hato Nuevo (Iocs. 128-131, Fig.3.2). In the lower Rfo Yaque del Sur Valley, the lower part of the formation was studied near Fondo Negro in the Azua - Barahona highway section (Iocs. 117-119, Fig.3.3, near turbidite Sections 1 and 2) and the Arroyo El Puerto section (Iocs. 58-66, Fig. 3.3). Similar faunal trends are noted in both of these regions. Most of the species noted in the Sombrerito are present and, in addition, Uvigerina peregrina. Hoeglundina elegans. Karreriella bradvi. and Uvigerina hispidocostata have their first stratigraphic occurrences (Figs. 3.8 and 3.9). Laticarinina pauperata and Osangularia mexicana are lost within the lower Trinchera, and the disappearances of Eggerella propinqua. Uvigerina hispida and Pvrgo murrhina are noted towards the middle of the formation. Based on general upper depth limits of disappearing species and on the bathymetry of newly appearing species, the outer turbidite fan facies of the lower Trinchera are interpreted as deposited in a middle bathyal, shallowing-upwaid environment (see Table 3.1 for bathymetry and references). The upper Trinchera assemblages reflect deposition in the upper bathyal zone. This interval was studied at Arroyo Salado (Iocs. 11-13, Fig. 3.2) and Arroyo Las Lajitas Goes. 132-137, Fig. 3.2) in the upper Rfo Yaque del Sur Valley. Localities in the lower Rfo

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Yaque del Sur Valley include Arroyo El Puerto (Iocs. 69-71, Fig.3) and highway outcrops (Iocs. 72-76, Fig. 3, near turbidite sections 3 and 4) near Fondo Negro, and the Arroyo de Bergal / Arroyo del Bao section (Iocs. 30-42, Fig. 3) in the Quita Coraza area. Sphaeroidina bulloides. Pullenia bulloides. Cassidulina subglobosa. Uvigerina peregrina. and Hoeglundina elegans. which decrease in abundance above about 200 m, persist to at least the top of the Trinchera. The deeper-water species noted earlier for the lower Trinchera Formation, which are most common below 500 m water depth (Table 3.1; Figs.

8 and 9), are absent in the upper bathyal, inner turbidite fan deposits of the upper Trinchera Formation. Downslope transport of shallow-water species is evident in some of the samples from both parts of the Rio Yaque del Sur Valley but is not a major factor. In contrast, samples from conglomerate-rich strata of the upper Trinchera Formation at Rio Via near Azua have notable proportions of shallow-marine contaminants, notably species of Amphisteeina, Asteriperina. Elphidium. and Planorbulina. mixed in with deeper water species. The deeper water forms, such as Pullenia bulloides. Sphaeroidina bulloides. and several stilostomellid species, suggest deposition in the upper bathyal zone.

Depositional Environments

Both lithofacies and benthic foraminiferal biofacies indicate that the Trinchera Formation was deposited in a prograding, shoaling slope setting. The slope advanced in the late Miocene and early Pliocene through the growth of a laterally-contained turbidite fan. The infilling of the basin by large volumes of siliciclastic sediment caused rapid shoaling in most areas. Benthic foraminifera indicate a change from middle bathyal depths of nearly

10 0 0 m in the lower part of the formation to upper bathyal depths of approximately 2 0 0 m at the top. This is supported by an overall upward decrease in the percentage of planktonics in the foraminiferal fauna, from over 95% to nearly 70%.

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The large volumes of conglomerates and pervasiveness of shallow-marine faunal contaminants in the Trinchera Formation at Rio Via suggests a steeper gradient of the slope in that region. This is a reasonable assumption considering the close proximity of this section to the Cordillera Central.

QU1TA CORAZA FORMATION

The Quita Coraza Formation is present only in the southern and eastern parts of the study area (loc. 2, Fig.3.1; Fig. 3.3) and is characterized by blue-green siltstones. This soft, fine-grained unit conformably overlies the Trinchera Formation and is conformably overlain by the Arroyo Blanco Formation. The lower Rio Yaque del Sur Valley follows the outcrop trend of the formation, as it is more easily eroded than the surrounding strata Outcrops in the Azua area are also marked by topographic lows. This formation takes its name from the Quita Coraza foraminiferal faunal zone of Bermudez (1949). As presently defined, the formation includes strata placed in both the Quita Coraza and Bao zones by Bermudez (1949).

Biostratigraphy

In the lower Rio Yaque del Sur Valley, samples of the Quita Coraza Formation from its type area (Iocs. 45 and 46, Fig. 3.3) and from near Fondo Negro (Iocs. 78-84, Fig. 3.3) are placed in the lower Pliocene (Fig. 3.6). The formation lies within the range of Globigerina nepenthes, which persists to the top of the Globorotalia margaritae zone (N19), and above the FADs of Globorotalia margaritae and Globigerinoides ruber, which lie in the base and middle of the Globorotalia margaritae margaritae subzone (N18), respectively, supporting placement within the upper three-fourths of the lower Pliocene.

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In Rio Via (Fig. 3.1, loc. 2), poor faunas make the biostratigraphy less precise. The presence of both Globigerina nepenthes and Candeinanitida suggests an age range of latest Miocene to early Pliocene.

Lithofacies

The Quita Coraza Formation is distinguished by massive blue to blue-green siltstones and mudstones with little coarse clastic material. Its contact with the underlying Trinchera Formation is conformable and gradational, generally placed at the top of the highest distinct turbiditic sandstone. However, thin and discontinuous sandstone beds persist into the lower Quita Coraza Formation. Likewise, a gradational contact is present between the Quita Coraza Formation and the overlying Arroyo Blanco Formation. The base of the Arroyo Blanco is usually marked by the first in-place coral beds in the lower Rio Yaque del Sur Valley, but intermittent pulses of sand and coral rubble are evident in the upper Quita Coraza Formation. In the lower Rfo Yaque del Sur Valley, it thickens from less than 200 meters east of Quita Coraza (loc. 4, Fig. 3.1) to nearly 700 meters west of Fondo Negro (see Fig. 3.3). At Rio Via near Azua (Fig. 3.1, loc. 2), the unit is approximately 540 m thick and displays the same characteristics as in the southern part of the basin.

Biofacies

The Quita Coraza Formation faunas reflect a transition from an outer to inner neritic

setting (Fig. 3.9). Some sm all Hoeglundina eleeans continue from the Trinchera Formation into the lower part of the Quita Coraza Formation, and small Cassidulina subglobosa are found through most of the unit. The presence of these species suggests depths of greater than 100 m (Phleger, 1951; and Table 3.1) for the lower part of the formation. In the upper

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part, Cancris sagra. Elphidium lanieri. and E. poevanum are present, all three typical of less than 100 m depth in the Gulf of Mexico (Phleger, 1951; Poag, 1985; and Table 3.1). In the Rio Via section, the Quita Coraza Formation contains Cassidulina subglobosa, Sphaeroidina bulloides. Oridorsalis umbonatus. Karreriella bradvi. and some stilostomellid species, suggesting deposition in uppermost bathyal or outermost neritic depths (Table 3.1).

Depositional Environments

The Quita Coraza Formation was laid down in a quiet shelf environment in the early Pliocene. It represents fairly rapid fine clastic sedimentation in the southern and eastern Azua Basin, with shoaling from outer neritic to inner neritic depths in a time span of

probably less than 1 million years, as suggested by the planktonic foraminiferal biostratigraphy. Influx of coarse clastic sediments was low.

ARROYO BLANCO FORMATION

The Arroyo Blanco Formation includes the stratigraphically highest marine sedimentary rocks of the Azua Basin. It conformably overlies the Trinchera Formation in the upper Rio Yaque del Sur (Fig. 3.2) and the Quita Coraza Formation in the lower Rfo Yaque del Sur Valley (Fig. 3.3) and Azua area (loc. 2, Fig. 3.1). The unit includes nearshore shallow-marine strata in its lower part and marginal marine strata higher up. In most areas, the base is marked by the stratigraphically-lowest prominent coral bed. Although originally defined by Dohm (1942 in Bermudez, 1949) in an "Arroyo Blanco" east of Quita Coraza, no exposures of this formation are found in the arroyo presently bearing that name. Instead, the section at Arroyo Las Lajas serves as the best example of

this formation.

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Biostratigraphy

The change from nearshore to marginal marine settings within the Arroyo Blanco Formation decreases the utility of planktonic foraminiferal biostratigraphy, but ostracodes become important index fossils (Fig. 3.13). However, ostracodes have only been noted in samples of the Arroyo Blanco Formation from the lower Rio Yaque del Sur Valley and have not been recovered in the upper Rfo Yaque del Sur Valley or the Azua area. In the Arroyo Las Lajas - Canada de Hicotea area (Iocs. 3 and 4, Fig. 3.1), the ostracode Radimella confragosa is found in the lower part of the Arroyo Blanco Formation (Fig. 3.13a b). This occurrence suggests that these strata are latest Miocene or younger, probably temporally equivalent to the upper Globorotalia humerosa chronozone (upper N17) or the Globorotalia margaritae chronozone (N18 and N19; Bold, 1983,1988). In this same area, Cvprideis salebrosa also occurs near the base of the Arroyo Blanco (Fig. 3.13 a). This species was originally described from the Talparo Formation of Trinidad (Bold, 1963) and has been reported from the upper part of the Mome Delmas Formation in Haiti, the Las Salinas and Jimam Formations in the Dominican Republic (Bold, 1975a), the Santiago Formation in Cuba (Bold, 1975b), and the upper part of the Lajas beds in Puerto Rico (Bold, 1975c). The base of the Cvprideis salebrosa brackish-water ostracode zone is defined by the first-occurrence of the nomimate taxon; comparison with planktonic foraminifera in over- and underlying marine strata in Caribbean sections has suggested placement above the last-occurrence of Globigerina nepenthes, within the Globorotalia margaritae evoluta subchronozone (N19) (Bold, 1983). Cvprideis sp. aff. C. portuprospectuensis Bold (Cvprideis n. sp.?, Bold, 1981) is found somewhat higher in the Arroyo Blanco in this area (Fig. 3.13a), and has been noted in the St. Marc area of Haiti (Bold, 1981). In this form, the left valve overlaps the right, as is normal in Cvprideis. rather than the reversed valve overlap evident in the otherwise

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Bold Bold Bold Hartmann Forester Brody P. P. pumila Bold Bold (Brady) sp. (Brody) off. Bold portusprospectuensis (Edwords) Bold Bold (Brady) Bold (Brody) sp. (Puri) sp. aff. C. sp. Bairdia Caribella yoni Cyprideis salebrosa Cyprideis moissadensis Cyprideis sp. Cyprideis similis Gangamocytherideo dictyon Cytherefloidea Loxoconcha (loxoconcha) levis Loxoconcha (Loxoconcha) Loxoconcha (Touroconcho) lopidiscola Orionina serrulate Perissocytheridea compressa Perissocytheridea cytheridelfoformis Perissocytheridea n. sp. Uraleberis torqvata Perissocytheridea subrvgosa Proteoconcha evai Ouadracythere producta Ouadracythere Radimello con&agosa — (Brady) Delorme Howe Brody Brody Swain Bold (Brody) feonensis (Bold) Bold Forester Bold Bold L. L. ceriotvberoso (Edwards) (Puri) Tressler Teeter (Bold) Sandberg Bold C. pufchra Coryell & Fields sp. A n. sp. Bold Coryell and Fields Bold sp. aff. C. (Puri) off. sp. off. sp. sp. sp. Cvshmanidea sp. Cyprideis mexicano Bairdoppilata oblongata Caribef/o yom CatWella navis Cyprideis moissadensis Cyprideis Limnocythere CytberelloideQ Cythereffo sp. Heterocypris sp. loxoconeha (Loxoconcha) levis Loxoconcha (Loxocomicvfum) dorsotubercvlata Loxoconcha (Touroconcho) lapidiscofa Hartmann Neocaudites scottoe Orionina similis Paracyris Paracylheridea tschoppi Paranesidea antiifea Pelfucistomo howei Perissocytheriea bicelliformo Perissocytheridea compressa Perissocytheridea plauta Perissocytheridea pumila Perissocytheridea Perissocytheridea Pvriono minuta Ouadracythere howei Rodimella confrogosa Perissocytheridea subrvgosa Xestofeberis anti/lea Xeslofeberis punctata Xestofeberis Swain Formation, Cafiada de Hicotea, Azua Basin, samples were collected by van den Bold; b) b) Bold; van den by were collected Basin, samples Azua de Hicotea, Cafiada Formation, Figure 3.13 - Ostracod occurrences in the southern roughly two, in listed samples Basin, Azua Azua Las Basin:Lajas, Arroyo Formation, Blanco Arroyo a) Arroyo Blanco Arroyo the of strata gypsum-associated upper, the c) TX); (Austin Mann P. by PM84- and parallel stratigraphic successions, with prefixes BW- and DM5- collected by the authors the authors by collected BW- DM5- and prefixes with successions, parallel stratigraphic thede M-prefixed flank ofNeibaSierra with Elsoutheast Yeso area, Formation, Blanco samples collected by the Dominican Seaboard Oil Company and A-prefixed by van den by specimens. den and van Company Oil collected Seaboard A-prefixed more samples the by Dominican or = 10 line wider specimens; 10 than less = line Narrower Bold. Bold Tressler Bold Bold sp. sp. Cyprideis moissadensis Cyprideis salebrosa limnocythere Orionina Perissocytheridea bicellibrma Xestofeberis antillea Xestofeberis punctata

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identical C. portuprospectuensis. These forms have only rarely been found together with C. salebrosa. which is probably due to slightly different environmental preferences. The most common ostracode of the Arroyo Blanco Formation is Cvprideis maissadensis. This species is found from Central Haiti to the Azua area, including occurrences in the highly gypsiferous Loma de Yeso Member of the Arroyo Blanco (Fig.

3.13c) on the southeast end of the Sierra de Neiba (loc. 6 , Fig. 3.1), but is absent in the evaporite-rich Enriquillo Basin sequence and in the Cul-de-Sac Basin of Haiti. From the above, it appears that in the shallow-marine ostracode zonation, the lowermost Arroyo Blanco is placed in the Radimella confragosa zone. In the brackish- water ostracode zonation, the Arroyo Blanco belongs to the Cvprideis salebrosa zone (Fig. 3.7). Planktonic foraminifera are absent in most samples of the Arroyo Blanco Formation from the upper Rfo Yaque del Sur and San Juan Valleys. Samples near the base of the formation in Arroyo Las Lajitas (loc. 137, Fig.2) contain late Miocene forms such as Candeina nitida but lack Pliocene forms. This indicates that the base of the Arroyo Blanco there lies within the uppermost Miocene, in the upper part of the Globorotalia humerosa chronozone (N17). Only two samples in the lower Rfo Yaque del Sur Valley can be assigned ages based on planktonics. The lowest part of the formation at Arroyo Barranca northwest of Fondo Negro (loc. 101, Fig. 3) may be placed in the upper part of the lower Pliocene or the lower part of the middle Pliocene. It lies above the FADs of Globorotalia margaritae and Globigerinoides ruber and below the LAD of Globoquadrina altispira. in an interval between the upper part of the Globorotalia margaritae margaritae subchronozone (upper N18) and the Globigerinoides trilobus fistulosus subchronozone (N20). If, additionally, the loss of Globigerina nepenthes before this interval is considered to be of stratigraphic significance rather than a result of shoaling, the middle Pliocene (N20) assignment would be favored (Fig. 3.6). Along Arroyo Las Lajas (loc. 3, Fig.l), one sample contains a very

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poor Pliocene fauna that includes Globigerinoides ruber, suggesting placement above the middle of the Globorotalia margaritae margaritae (middle N18) subchronozone.

Lithofacies

The Arroyo Blanco Formation is typified by siltstones, sandstones and conglomerates. Coral beds are common towards the bottom, while gypsum may be found

in its upper part in the El Yeso area (loc. 6, Fig. 3.1). Overall, the formation is a coarsening-upward regressive sequence, from a coralliferous- to siltstone dominated interval near the base to conglomerate- and sandstone-dominated strata towards the top. Arroyo Las Lajas - The section at Arroyo Las Lajas (loc. 3, Fig. 3.1; and Fig. 3.14) is a nearly complete, well-exposed example of the facies progression in the Arroyo Blanco Formation. Discussion is based in a laige part on section measurements generously provided by P. Mann (University of Texas Institute for Geophysics). In the lowest part of the section, three primary facies may be identified: 1) sandstone, which is common and includes muddy, shell-fragment-rich beds and cross-bedded strata;

2 ) coralliferous beds, less commonly present, are mostly redeposited coral rubble beds and coral rubble-rich mudstones, but several growth-position units are also noted; 3) siltstone and mudstone, the dominant facies type, which is commonly well bioturbated and of gray- green to olive-brown color. Individual coral beds and sandstones generally may not be traced more than several kilometers laterally. The relationship of these facies might suggest a shallow-marine offshore setting for the lower Arroyo Blanco (Selley, 1970), with the sandstones representing bar sands and the coral reflecting scattered reef buildups. This would be similar to the present setting off the southwestern Dominican Republic coast.The upper seven-tenths of the section is typified by fining- and thinning-upward cycles of conglomerates, sandstones and siltstones. The lower part of this interval includes fine- to medium-grained sandstones of up to 4 m thickness, mud-rich and shelly in the finer

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. caret bed - b'anchinq cwat b e d - h e o d Itouqh * '.tram corxjlorrn':’* C o< ol Plane paioHe* fumince Cwal limestone M ud'till inle/Iomince upward sequence fining/thinning Cooaeninq/rhidiening J J ‘ ‘ ] Plonat x st»um , .] / upward sequence X j . 7 1 U J*lfolo*rrxiliona! .. ED | ” ~ * ] | >11:i| 0ioturboi'oo [ 7 T ] Shell [ ~y[ j 770m I \/ \ coveted interval 1 sequence, Arroyo Las Lajas. Section reads continuously from lower left to upper right. The The right. upper to left lower from continuously reads Section Lajas. Las Arroyo sequence, complex. Figure 3.14 - Measured section from deposition, the shallow-marine Arroyo offshore of indicative Blancofacies include section Formationthe part of lowest delta coastal coastal coarse-grained small, clastic ofa part as deposition suggest strata upper the whereas L coortt silt— ” — line mud—I j|*— medium

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grained examples or exhibiting tabular-planar and trough cross-bedding in the coarser- grained. The siltstones and mudstones are often in groups of alternating red- and green- colored beds. The sandstones of the upper part of this interval are similar to the lower, but

are generally more common, coarser-grained (often gravelly) and thicker (usually over 1 m and occasionally up to 5). Trough cross-bedding is common, as well, with alternating directions evident in some beds. The fine grained beds between the sandstones are mostly brown siltstone and very-fine sandstone. This upper seven-tenths of the section appears to have formed part of a small delta complex, transporting high volumes of coarse -grained sediments over a short distance and steep gradient ftom the Cordillera Central to a submarine fan at the slope-break. The sandstones probably originated in delta and tidal channels choked with sediment. These channels laterally migrated or were abandoned, and then capped by fine-grained sediments, producing the fining-upward cycles. Nearly identically developed lithofacies are seen in Canada de Hicotea (loc. 4, Fig. 3.1), which is located only 2 kilometers to the west of Arroyo Las Lajas. Other exposures- The lower boundary of the Arroyo Blanco Formation is difficult to recognize precisely in the upper Rio Yaque del Sur and Rio San Juan Valleys. For example, in the Arroyo Las Lajitas section (Fig. 3.2, Iocs. 137 to 138 and DM1-3 to DM1- 4), the transition between the underlying Trinchera Formation and the Arroyo Blanco is gradational. In the southern part of the study area, these units are separated by the Quita Coraza Formation, and the base of the Arroyo Blanco Formation is marked by a distinct, coral horizon. Several indistinct coral beds are present in the Arroyo Las Lajitas section and, although these are probably composed of transported material, the lowest is arbitrarily chosen as the basal bed of the formation. Above this level, the formation is composed of interbedded silty mudstones, siltstones, sandstones, and conglomerates. The sandstones may contain transported gastropod and bivalve (including oyster) shells. The conglomerates are made up mostly of igneous clasts and in places include blocks of over 50 cm in diameter.

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At Rio Via (loc. 2, Fig. 3.1), the Arroyo Blanco Formation is more conglomeratic than in other areas and grades upward into the fluvial or alluvial fan facies of the Via Formation. The conglomerate beds may range up to several meters in thickness and contain clasts of up to 15 cm, but mostly near 5 cm, in size. The composition of the clast population is approximately one-half plutonic and one half sedimentary (limestone and sandstone), reflecting a Cordillera Central provenance. Sandstones in this part of the section are of lenticular geometry, pebbly in places, and often contain transported shells.The base of the formation is marked by an approximately 1 m thick bed of coral rubble. Other coral rubble beds are present higher in the formation, with the long axes of the the coral branch fragments oriented east-west.

Paleocurrents

Paleocurrent measurements from the lower part of the Arroyo Blanco Formation at Arroyo Las Lajas (loc. 3, Fig. 3.1) indicate a dominantly southeastward direction of sediment transport. The measurements, supplied by P. Mann (University of Texas Institute for Geophysics), are based on the alignment of coral branch fragments in mass flow deposits and of cross bedding directions and channel alignments in sandstones. Mean paleocurrent directions in 3 coral debris deposits in the lower 30 m of the formation range from 96° to 169 °. Mean directions from cross-bedded sandstones in the next 100 meters lie between 80° and 120°. Above that level, scattered measurements from cross-bedding and channel lineations vary from 60° to 160°.

Biofacies

The benthic foraminifers Cancris sagra and Elphidium spp. are common in the lower nearshore strata of the Arroyo Blanco Formation in the lower Rfo Yaque del Sur Valley, as

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at Airoyo Barranca (loc. 101, Fig. 3.3; and Fig. 3.9). These species are typically inner shelf forms, from water depths of less than 100 m (Phleger, 1951; Poag, 1985; and Table 3.1). Large specimens of Sorites are also present in the lower part of the formation at Arroyo Las Lajas (loc. 3, Fig. 3.1). This form is common in eel grass environments (Sen Gupta and Schaefer, 1973; Brasier, 1975). Strata placed in the basal Arroyo Blanco Formation in the upper Rfo Yaque del Sur / San Juan Valley and in the Azua region appear to have been deposited at uppermost bathyal depths. In the former area, rare Cibicides wuellerstorfi are present in one sample (loc. 137, Fig. 3.2; Fig. 3.8); Oridorsalis umbonatus. Pullenia bulloides. Sphaeroidina bulloides. Uvigerina peregrina. Hoeglundina elegans and stilostomellid species also characterize the interval. From the middle of the formation upward, the fauna is composed of exclusively shallow- to marginal marine faunas that include Elphidium and Ammonia Although more poorly preserved and lower in diversity, the basal Arroyo Blanco fauna at Rfo Via (loc. 2, Fig. 3.1) also appears to be an uppermost bathyal or outer neritic type. Cassidulina subglobosa. Martinotiella sp., costate Uvigerina. and stilostomellid species are notable constituents, in addition to badly abraded, transported Amphistegina and Asterigerina Ammonia parkinsoniana becomes more abundant above the base of the formation in more conglomeratic, less fossiliferous strata, suggesting an upward change to more marginal marine settings. The ostracodes of the Arroyo Blanco reflect the same environmental change suggested by the foraminifera in the lower Rfo Yaque del Sur sections. As noted earlier, Cvprideis salebrosa is found near the base of the Arroyo Blanco, as seen in the Canada de Hicotea section (Fig. 3.13a; loc. 4, Fig. 3.1). This species is restricted to very low salinity environments. Radimella confragosa is present in this same interval in Canada de Hicotea and Arroyo Las Lajas (Fig. 3.13a and b; loc. 3, Fig. 3.1). This suggests a shallow marine setting where brackish water forms were washed in from nearby lagoons. Higher up in the formation, the predominant species are brackish-water types (Fig. 3.13); towards the top,

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most of the samples are barren. This is particularly notable in the El Yeso area (loc. 6 , Fig. 3.1; and Fig. 3.13c) where gypsiferous facies are well-developed. Macrofossils from the Arroyo Las Lajas section indicate a similar ecologic setting (E. Petuch for P. Mann, written comm., 1984). The macrofauna includes the bivalves and gastropods Bulla sp. cf. B. striata. Orthaulax gabbi. Siphocvpraea lenckeni. Strombus proximus. Turritella sp. cf. T. patunensis complex and Ceratolithus dominicense. and the coral Porites furcatus.

Depositional Environment

The Arroyo Blanco Formation represents deposition in a shallow marine - fluvial deltaic setting. The lithofacies suggest an upward progression from a elastics dominated shelf with scattered coral reefs to a coastal deltaic complex that produced a thick, coarsening upward sequence composed of many fining upward cycles. This lithofacies progression is paralleled by vertical biofacies changes. In the lower Rfo Yaque del Sur Valley (Fig. 3.3), the lowermost strata are characterized by inner shelf foraminifera and ostracode species, with occasional occurrences of lagoonal species as a result of local transport. Macrofossils include coral and molluscs typical of patch reefs and associated turtle grass communities. Higher in the formation, the microfauna is composed nearly exclusively of brackish ostracodes, indicating a lagoonal or fluvially-influenced bay environment. Barren samples near the top of the unit probably reflect a full transition to fluvial conditions. The basal Arroyo Blanco Formation in the upper Rfo Yaque del Sur Valley (Fig. 3.2) was lain down in a slightly deeper-water setting than in the lower part of the valley. The contact with the underlying Trinchera Formation is gradational with the basal Arroyo Blanco representing a transition from aturbidite-dominated submarine fan setting to a

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coastal deltaic fan complex. Higher in the formation, the foraminifera are typical of inner neritic environments. The Rio Via section (loc. 2, Fig. 3.1) appears to represent deposition off a steep shoreface.as part of a submarine fan - delta - alluvial fan complex that advanced over the Azua area in the late Miocene and/or early Pliocene. The strata of the Arroyo Blanco Formation are more richly conglomeratic at Rio Via than at other localities. Foraminifera in the lowest part of the section include species typical of outer neritic or uppermost bathyal settings, but the nearly ubiquitous presence of nearshore foraminifera, molluscs, and corals indicates extensive downslope transport. The nature of the Arroyo Blanco Formation in the three regions discussed above suggests that variations in sedimentology are in a large part attributable to paleoslope. The conglomeratic lithology and extensively transported fauna of the Rio Via section suggest that the steepest paleoslopes existed in the Azua region. Both in the Azua and similarly steeply sloped upper Rio Yaque del Sur / San Juan Valley, Arroyo Blanco deltaic fan deposition began at upper bathyal or outer neritic depths. Gentle paleoslopes appear to have affected the Arroyo Blanco Formation in the lower Rio Yaque del Sur Valley. The lower part of the formation is predominantly sandstone and siltstone, with reefal units and foraminiferal faunas characteristic of an inner neritic setting. These suggested paleoslopes are consistent with the present-day physiography, with the Rio Via section situated at the foot of the island's central mountain belt, the source of the Neogene sediments of the basin, whereas the lower Rio Yaque del Sur Valley sections Goes. 3 and 4, Fig. 3.1; loc. 47, Fig. 3.3) are located more than 30 km to the southwest.

ANGOSTURA FORMATION

The Angostura Formation is the lowest unit exposed in the several thousand meter thick late Neogene sequence of the Enriquillo Basin. It is characterized by interbedded

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evaporites and shales that outcrop in a narrow belt on the southern flank of the Enriquillo Basin

Biostratigraphy

The Angostura Formation has an ostracode fauna that is very poor, but compositionally identical to that of the lower part of the overlying Las Salinas Formation (Bold, 1975a). The species Cvprideis subquadraregularis and Cvprideis pascaguolaensis were reported in an earlier study Bold (1975a), suggesting placement near the Miocene - Pliocene boundary in the Cvprideis nascagoulaensis - Cvprideis subquadraregularis zone

(Fig. 3.7).

Lithofacies

The Angostura Formation is characterized by thick deposits of gypsum and halite. Green, black, and reddish platy gypsiferous shales are common and some black to reddish calcareous sandstones occur near the top of the formation. The evaporitic facies are well- developed at Mina de Sal y Yeso (loc. 7, Fig. 3.1) on the east end of the southern flank of the valley. There they may be characterized as repeating shale-gypsum-halite cycles with thicknesses on the order of 0.75,2.5, and 2 to 2.5 m respectively (M. Nova, mine director, oral comm., 1985).

Biofacies

The ostracode fauna of the Angostura Formation was discussed in Bold (1975a). It includes Cvprideis subquadraregularis and Cvprideis pascaguolaensis, species which suggest brackish-water or hypersaline conditions.

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Depositional Environment

The Angostura Formation was deposited in a restricted, shallow lagoon environment of high salinity. The ostracode faunas are indicative of brackish or hypersaline waters. This is compatible with the presence of thick accumulations of gypsum and halite which indicate that high salinity conditions prevailed in the Enriquillo Basin, at times reaching at least ten times that of normal seawater. Deposition of similar evaporitic sequences is usually indicative of water depths of less than 5 m (Kendall, 1984). Possible scenarios might include obstruction of the connection between the Enriquillo Valley and the Caribbean Sea by a structural barrier or by a pile of sediment deposited by a proto-Rio Yaque del Sur drainage system, leaving an isolated saline lake in the Enriquillo Valley.

LAS SALINAS FORMATION

The Las Salinas Formation is a unit of shallow-marine and marginal-marine clastic sediments of over 2000 m thickness. It is exposed in an elongate belt on the south side of

the Enriquillo Basin.

Biostratigraphy

The shallow marine to lagoonal setting of the Enriquillo Basin in the Neogene is more favorable to ostracodes than to planktonic foraminifera, so the biostratigraphy relies upon the former. The oldest beds containing ostracodes, south of Duvergd, were mapped as Arroyo Blanco Formation by geologists of the Dominican Seaboard Oil Company. On the map accompanying this volume, it is indicated as Las Salinas Formation. The fauna includes the

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brackish-water form Cvprideis pascagoulaensis. a species which has so far not been found in beds definitely younger than latest Miocene (Fig. 3.7). The Las Salinas Formation shows scattered occurrences of the shallow-marine species Radimella confragosa. which is known from approximately the upper Globorotalia humerosa chronozone (upper N17) to the Holocene. The formation also contains Cvprideis subquadraregularis in its lower part. This species is replaced upward by Cvprideis salebrosa. which usually appears at a level approximately equivalent to the Globorotalia margaritae evoluta subchronozone (N19) (Bold, 1983; and Fig. 3.7). In the Arroyo Aculadero section (Fig. 3.15b), C. salebrosa is gradually replaced by Cvprideis portuprospectuensis. accompanied by Peratocvtheridea karlana. Other than its regular appearance above the base of the range of C. salebrosa. the exact position of £. portuprospectuensis in the stratigraphic zonation is not yet clear. Its other known occurrences are in the Harbour View beds (overlying the August Town Formation) of Jamaica, where it was originally described, as well as in the Jimarn Formation of the Enriquillo Basin (although not in the type section, see Fig. 3.15c) and the upper part of the Mome Delmas Formation in the Cul-de-Sac Basin of Haiti (Bold, 1975a). These occurrences indicate that, in the brackish-water zonation, the basal Las Salinas lies within the Cvprideis subquadraregularis zone, with the greater part of the formation placed in the Cvprideis salebrosa zone. In the shallow-marine ostracode zonation, the Las Salinas belongs to the Radimella conffagosa zone (Fig. 3.7).

Lithofacies

The Las Salinas Formation conformably overlies the Angostura and is over 2000 m thick. Overall, the formation is typically soft reddish-brown to buff claystone, green-gray to blue-gray shale, red-brown to green-brown sandstone, coral and mollusc coquinoid

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ro co Forester Brody Bold Swoin subsp. Broo***ker Broocfcokker sp. A. Bold, 1975 (0 . F. Muller) Swoin? Broodbokker? Bold Sondberg r ttk v h la Purper sp. A. BoW. 1975 n. sp ierfano (Stephenson) onguhto sp. A. Bold. 1975 (Brody) sp. gr. tphoeroidea sp 1 •> gr. •* pr. stevemoni (Brody l> Robertson) Perissocytheridea eytheridellobrmis Perissocytherideo rvgato Perissocytherideo Physocypriasp Pseudocandono coribeono Sfrondfjio loxoconcho (loxoconcho) Perxslocytberideo Perissocytheridea bieellibrmo Perissocytheridea bicelhfomso Pernsocythendea Heferocypris loxoconcho (loxoconcha) lens Cyprideis mexkano Cyprideis portusprospectvensis Cyprideis sotebroso Cyprideis similis Cytheridello boldi Dorwmub Hemkypris Cyckxypris Compybcythere Condone ex 11 (Brody) (Krytok) Brody Sworn (Brody) lews Brody (Brody) Bold pvkbro (Edw rdi) Bold Sondberg (Brody) Brody (Brody) Coryell & Fields off. C. ip. sp. (loxocomicvlum) dortoh&ertvhto sp simihs sp.

"Campylocythere"perieri Parocytherideo fteheppi Pellvcisioma Neocoudites Orionino serrvioto Perissocytheridea bkeWfotma Pvriona Kodimelb eonhogoso Catrvrlla novis Cyprideis mexicono Cyprideis tolebroso C y p r u s Cytberello pofito loxoconcha (loxoconcha) tojroconcfto loxoconcha (loxocomicvlum) tricomato Xesioieberis Cytherel/o sp Cyfffervro sp. Jugosocythereis ponnoso s

f ? r r f if S’? Narrower line = less than 10 specimens; wider line = 10 or more specimens. more or = 10 line wider specimens; 10 than less = line Narrower t o

S « in tt&sp. (Brody) “ S E n n S S S V c ) Formation Jimanf north of Jirnanl, s ^ p k s coheacd by P. Mm" Gutttrtog & Benson

underlying Holocene reef sediments, Arroyo Aculaaero secuon, & vrann sse -m S itS g Bold. 1975 Bold Sondberg Bold (Brody) sp. Cyprideis mexkano Cyprideis salebrosa Cyprideis similis Heierocypris Umnocythere fhridooo Keysetlimnocythen staptini Perissocytherideo bicethformo Perissocytheridea bkolOformo Perissocytheridea subrvgosa Perissocytheridea %p Xestoteberis pntilha

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sandstone, and some limestone conglomerates. The sandstones are often trough cross bedded. At its type area northeast of Loma de Sal y Yeso on the south flank of the valley (loc. 7, Fig. 3.1), its base is marked by a two meter thick, resistant bed of pink molluscan limestone. Fine to medium-grained symmetrically-rippled green sandstone is found just above this limestone. Symmetrical ripples form in a protected lagoonal setting such as this in water of no more than several meters depth (Clifton, 1976). The section at Arroyo Aculadero (loc. 11, Fig. 3.1) to the west is finer grained than the type section. Soft brown claystone, siltstone, and light gray shale are the most common rock types, often containing small bivalve and gastropod shells. Outcrops of strata referred to as "Arroyo Blanco" by geologists of the Dominican Seaboard Oil Company (Bermudez, 1949), but not typical of that unit, are noted near

Duvergd on the southern side of the valley (loc. 8 , Fig. 3.1). These include soft, chalky limestone, soft sandy red clay shales, and reddish conglomerate with associated sandy red claystone. These are tentatively placed in the Las Salinas Formation.

Biofacies

Paleoenvironmental interpretations are primarily based on species of the genus Cvprideis. Although widely distributed, the different species are strongly influenced by changes in salinity. Cvprideis subquadraregularis and Cvprideis pascagoulaensis are present in the lower Las Salinas Formation as part of a fauna nearly identical to, but somewhat richer than, that of the underlying Angostura Formation. These two species appear to favor slightly higher salinities within the brackish-water environment (Bold, 1975a). The shift from Cvprideis subquadraregularis to C. salebrosa higher in the lower part of the Las Salinas suggests a drop in the salinity. Cvprideis salebrosa is typical of very low salinity environments and is quite often found together with freshwater ostracodes (Bold,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 125 1: Harbour View beds, Hope River, St. Andrews Parish, Jamaica 2: Santiago Formation, Sontiogo, Cuba 3: "las Cohobos" Formation, SI. More, Haiti 4: las5: Cohobas M6: ome JimoniDelmarFormation,7: Formation, Las Formation, Salinas Plateau Jimani,Formation, Cul-de-SocCentral, Dominican Bosin, Enriquillo Haiti Republic HoitiBosin, Dominican Republic 8: East9: Barbarita, Arroyo Blanco Enriquillo Formation, Basin, lomo Dominican de Republic Yeso, Dominican Republic 10: Arroyo11: CercadoBlanco12: lajasFormation,Formation, beds, Azua Cibao SouthwestProvince, Basin, Dominican DominicanPuerto RepublicRicoRepublic

Bold (B rady )

(Mincher) S a n d b erg Bold C. C. porlusprospectuensis (B rady ) sp . a ff. Bold Cyprideis moissadensisCyprideis Bold Cyprideis mexkanoCyprideis poscogouloensis Cyprideis porlusprospectuensisCyprideis salebroso Cyprideis Cyprideis similis Cyprideis Cyprideis subquadraregularis Cyprideis Cyprideis Figure 3.16 - Geographic distribution ofthe genus Cvprideis in the late Miocene and Pliocene Pliocene in the Greater Antilles, with greatest Hispaniola. concentration of localities in southern

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1975a). In the upper Las Salinas Formation in the Arroyo Aculadero section, Cvprideis portuprospectuensis becomes the dominant species of the genus, so a higher salinity would have been probable there. Moreover, the different species of Cvprideis appear to occur in roughly east-west trending belts (Fig. 3.16): Cvprideis maissadensis from eastern Cuba over the Central Plateau of Haiti to the Azua region; Q. sp. aff. C. portuprospectuensis from the St. Marc area of Haiti to the Azua area; C. subquadraregularis from eastern Cuba through the Enriquillo Valley to southwest Puerto Rico; and C. portuprospectuensis from Jamaica through the Cul-de-Sac and Enriquillo Basins.

Depositional Environment

The Las Salinas Formation is characterized by lithofacies and biofacies that indicate deposition in a shallow embayment with varying marine influences. The sedimentary structures of some of the sandstones point to deposition in a restricted, relatively low- energy nearshore setting. Microfossils indicate that the salinity varied from brackish or possibly hypersaline water, to nearly-normal marine, suggesting intermittent connection to the Caribbean. JIMANI FORMATION

The Jimanf Formation is the uppermost unit named in the Enriquillo Valley. It typically includes fossiliferous limestones with associated fine-grained sediments that lie unconformably on the Las Salinas Formation. The geology of the Jimanf Formation is briefly discussed here to complete the outline of the ostracode biostratigraphy of the Enriquillo Basin. However, more detailed treatment of the Quaternary of the basin is planned for later papers.

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Biostratigraphy

Rare occurrences of "Campvlocvtheie" perieri are reported by Bold (1975a) in the

Jimanf Formation, notably on the south side of Lago Enriquillo east of Lago Lim 6n (loc. 10, Fig. 3.1). No occurrences are noted in the type area of the formation north of Jimanf (loc. 12, Fig. 3.1). This species so far has not been found in beds older than Quaternary (Bold, 1975a), suggesting a Pleistocene age for at least this part of the formation. North of Lake Enriquillo, strata exposed in the East Barbarita section (loc. 9, Fig. 3.1) below the Holocene-reef sediments have been mapped as Arroyo Blanco Formation. However, samples of these strata carry a fauna (Fig. 3.15a) which includes "Campvlocvthere" perieri , suggesting correlation with the Jimanf Formation on the south side of the lake.

Lithofacies

The Jimanf Formation on the south side of Lago Enriquillo is composed of intercalated claystones, calcareous siltstones, and coquinoid limestones. On the north side of the lake, strata believed equivalent to the Jimanf Formation are coarser-grained sediments including calcareous siltstones and claystones with intercalated conglomerates and sandstones.

Biofacies

Ostracode faunas of the Jimanf Formation reflect environmental variation between nearly-freshwater and shallow-marine conditions. The presence of Cvprideis salebrosa and Limnocythere staplini suggest a fresh- to brackish-water setting for some intervals of this unit (Fig. 3.15a and b; also see Table 3.2, Bold, 1975a). The occurrences of Loxoconcha

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laevis and Radimella confragosa suggest brackish to shallow-marine conditions in other intervals of the Jimanf Formation (Fig. 3.15a; see also Table 3.2, Bold, 1975a).

Depositional Environments

The geologic framework and microfauna of the Jimanf Formation suggest deposition during the Pleistocene in a lagoon with intermittent marine connections to the Caribbean. Ostracodes reflect temporal variation of salinity in the stratigraphic sections. The predominantly fine-grained nature of the clastic sediments on the south side of the basin reflect prevailing calm conditions in the Pleistocene saline lake. The greater abundance of coarse clastic sediments on the north side of the basin is probably due to the proximity of the sampling sites to the Sierra de Neiba.

SUBSIDENCE

Comparison of bathymetric changes versus stratigraphic thicknesses indicates significant subsidence of the floor of the Azua Basin in the late Miocene and Pliocene. Evidence from both the lower and upper Rfo Yaque del Sur Valley sequences demonstrates that the Azua Basin was filled by a sediment thickness of over two and one-half times its original depth. The amount of subsidence in each stratigraphic unit was calculated using the method of Bandy and Amal (1960) and is shown in Tables 3.3 and 3.4. The rate of subsidence can be estimated by comparing the subsidence in these sections to the geochronology of planktonic foraminiferal datum planes in Beiggren and others (1985). Subsidence is difficult to interpret for the Sombrerito Formation because overall, stratigraphic control is poor due to extensive faulting in this unit. However, by all indications, subsidence was slow prior to the late Miocene during deposition of the Sombrerito Formation. No significant depth change is evident between the oldest and

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 129 350 950 775 450 1400 Subsiden 75 425 800 25 50 350 150 800 Shoaling 25* -50 0 -1000 -50 -200 -1000 500 500 150 1750 800 400 600 2200 0 1750 -200 2750 2250 0 level Thickness bathymetry 4000 25* 2800 3200 2200 Stratigraphic Paleo- and Amal (1960). Amal and Table 3.3 - Subsidence in the upper Rfo Yaque del Sur Valley, using the method of Bandy Bandy of method the using Valley, Sur del Yaque Rfo upper the in Subsidence - 3.3 Table and Amal (1960). Amal and Table 3.4 - Subsidence in the lower Rfo Yaque del Sur Valley, using the method of Bandy Bandy of method the using Valley, Sur del Yaque Rfo lower the in Subsidence 3.4 - Table unit______unit______level Thickness bathymetry Shoaling Subsidence unit Stratigraphic Stratigraphic Stratigraphic Paleo- Stratigraphic Trinchera Trinchera Fm. Quita Coraza Fm. Coraza Quita Trinchera Trinchera Formation marine Arroyo Blanco Fm. Blanco Arroyo marine marine Arroyo Blanco Fm. Blanco Arroyo marine deltaic and fluvial sediments fluvial and deltaic deltaic and fluvial sediments fluvial and deltaic

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youngest Sombrerito strata studied. This suggests that the rate of sedimentation generally kept pace with the rate of subsidence of the basin floor. The deposits are dominated by pelagic and hemipelagic sediments, with scattered influxes of shallow-marine carbonate debris. A 67 m thick section at Rfo Los Baos (loc. 1, Fig. 3.1), the longest, continuous interval in the Sombrerito Formation, was found to span most of the upper half of the Globigerinatella insueta planktonic foraminiferal zone (N7). Assuming that this interval is approximately equivalent to zones M4 and M5 of Berggren (1983), it represents a time span of approximately 0.5 m.y., giving an approximate sedimentation rate of 134 m/m.y.. The rate of basin subsidence should be of the same order. In the late Miocene and later, subsidence apparently increased significantly. At the same time, the sedimentation rate greatly increased with the rapid accumulation of turbidite fan and coarse deltaic deposits. In the upper Rfo Yaque del Sur Valley section (Table 3.3), a total of 1300 m subsidence is estimated for the clastic marine portion of the interval. Deposition of this sequence took place from approximately the middle Miocene - late Miocene boundary (near FAD Globorotalia acostaensisl to just before the Miocene - Pliocene boundary (just above FAD Candeina nitidah a period of approximately 3.5 m.y.. This suggests a subsidence rate of approximately 370 m/m.y. in the late Miocene. Similarly, 2200 m of subsidence is estimated for the clastic marine strata of the lower Rfo Yaque del Sur Valley (Table 3.4). Planktonic foraminifera suggest that this interval was lain down between the latest Miocene (just below FAD Globorotalia margaritae') and just before the end of the early Pliocene (above LAD Globigerina nepenthes), an estimated time span of 3 m.y.. These values suggest a subsidence rate of approximately 730 m/m.y. in the early Pliocene. No correction was made for sediment compaction in the calculations of subsidence. Compaction would be especially significant in the shale-sandstone sequence of the Trinchera Formation, so the estimates given here would be somewhat lower than the true subsidence. In addition, any detailed analysis of subsidence rates within each stratigraphic

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unit is beyond the resolution of the planktonic foraminiferal biostratigraphy in the short time interval considered and would be complicated by disagreement over the details of zonation around the Miocene-Pliocene boundary. However, it is clear from the data that late Miocene and later subsidence was rapid and significantly greater than in the lower and middle Miocene. Late Miocene and Pliocene subsidence of the floor of the Enriquillo Basin appears to have also been significant. Wells drilled in the in the central part of the basin (Mella 1 and 2, Charco Largo; see Mann and others, this volume) have penetrated about 4000 m of Neogene shallow-marine sediment of the Angostura Formation, Las Salinas Formation, and Quaternary strata. Lithologic, ostracode, and foraminiferal data for these units suggest a similar setting as exists today. Thus, as the basin was only a shallow depression through most of its history, the thick accumulation of sediments was accommodated almost entirely by subsidence of the basin floor. The increase in subsidence in the late Miocene reflects overthrusting of the Azua and Enriquillo Basins by northeast- and southwest-bounding fault blocks. Studies of subsidence in foreland basins (Price, 1973; Jordan, 1981; Beaumont, 1981) indicate that the load of thrust sheets in adjacent fold-thrust mountain belts drive isostatic subsidence of the region through lithospheric flexure. In the case of a ramp valley basin, such as the basins in this study, loading occurs on both flanks of the basin due to overthrusting of the bordering mountains. Generally, this type of basin is narrow, 20 to 30 km against the 100's of kilometers common in foreland basins. As a result, the load from the bounding thrust blocks is concentrated in a narrow belt centered around the axis of the basin, causing rapid subsidence. Basin subsidence should be further driven by rapid accumulation of sediments derived from the mountain blocks, as modeled for foreland basins by Jordan (1981).

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NEOGENE DEPOSITIONAL HISTORY OF THE ENRIQUILLO - AZUA AREA

Integration of the paleontologic and sedimentologic data constrains the Neogene basin history of southern Hispaniola. The Enriquillo and Azua Basins appears to have evolved in two stages: a pie-late Miocene open-ocean stage; and a late Miocene and younger laterally- confined clastic basin stage (Figs. 3.17 and 3.18). The evidence for this development is most evident in the Azua Basin (Table 3.5). The open ocean stage includes late-early and early-middle Miocene age pelagic deposits of the Sombrerito Formation (Table 3.6), which are known from the south flank of the Cordillera Central to near the southern edge of the island. Apparently these strata were lain down at depths of 1000 m or more and deposited off a Hispaniola slope open to the Caribbean Sea (Figs. 3.17a and 3.18a). Sandstones of this period are turbidites composed of shallow- marine carbonate-debris, siliciclastic sands being conspicuously absent. The lack of erosion products from the Cordillera Central suggests low relief of the core of the island. This implies relative tectonic stability of Hispaniola during the first half of the Miocene. By the late Miocene, several striking changes had taken place: the onset of rapid siliciclastic sedimentation with a source in the Cordillera Central; an increase in subsidence rates; and the apparent rise of a barrier on the south side of the Azua Basin (Table 3.6). The initiation of siliciclastic sedimentation in the Azua Basin is reflected in the sedimentology of the Trinchera Formation, a unit of mud-rich, lithic- and feldspar-rich sandstones deposited by turbidity currents (Figs. 17b and 18b). The compositional trends in these sandstones show strong relationships to the rocks exposed today to the north of the basin in the Cordillera Central. The dominant rocks today in the central and northern parts of this range are actinolitic epidote amphibolite greenschists of the Duarte Formation (Bowin, 1975) and are represented in the petrology of the Mio-Pliocene sandstones. On the south flank of the cordillera, Cretaceous andesitic to dacitic volcanics, as well as tuffs and quartz keratophyre

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. MIDDLE PLIOCENE EARLIEST PLIOCENEEARLIEST ond mods ond LATE EARLY PLIOCENE I , J n sequence, proximot focies focies proximot sequence, t £ u i ) . «... - . ... ., I" :-: l hxbtdle ostic TrmcheroBn-siUtc . c .. LATEST MIOCENELATEST ______ond sholes sholes ond Angostura Pm-Wite, gypsum. Pm-Wite, gypsum. Angostura twbidite hero Fm*silitkk«tk Trine LV.Vv'j P '""1 limestones Sombwho Fm-pelogic f t # MIOCENELATE EARLY W 7 7V/A \ .ijM ilA TE MIDDLE MIOCENE 7'*NC'4py>4' \ 7'*NC'4py>4' BAHQRUCO clostics ond corol limestone limestone corol ond clostics BvvSw* BvvSw* [iK ljj Ui2-U more* non clostics more* Frtwnorginol Blonco Arroyo R§3§j«J . IflO ij ' n fooes o o q Fm-gypsiferous “,r Blonco Arroyo tstone si Fm-r*ri!ic Coraio Qurto f :-r - I? -l . . L iiiU dutol sequence. foctes r ^ s j Seco/Viofm- Arroyo . E*y*v*l Figure 3.17 - Paleogeographic cartoon for the Azua and Enriquillo Basins from the Middle Middle the from Basins Enriquillo and Azua the for cartoon Paleogeographic - 3.17 Figure Miocene through Middle Pliocene. Southeastward migration of clastic wedge in the Azua Azua the in wedge clastic of migration Southeastward Pliocene. Middle through Miocene directions. paleocurrent indicate Arrows evident. is Basin

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‘SECTIONsa; _

SW NE

1500m S e a L e v e l fAN PELAGIC LIMESTONE

15km MIDDLE MIOCENE

500m

LATE MIOCENE

S ie r r a d e S ie rr o d e C o r d ille r a Bahoruco N e ib a Central

evaporites 5 0 m

MIDDLE PLIOCENE

Figure 3.18 - Schematic cross-section of the southwestern Dominican Republic. Shows the change from a tectonically-quiet open ocean basin in the Middle Miocene to a pair of tectonically-active, laterally restricted basins in the Pliocene.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 135 rejuvenation of uplift in the Cordillera Central. te c to n ic s uplift of S ierraand d e Cordillera N eiba Central. uplift of Sierra d e N eiba and Cordillera Central. creation of Sierra de Neiba; relatively stable. uplift of S ierra d e N eiba and Sierra de Bahoruco. uplift of Sierra d e N eiba; creation of de SierraBahoruco (?) uplift of Sierra d e Neiba. relatively stable. Sombrerito Fm. Blanco in southern region. fan; Arroyo BlancoCoraza deltaics shelf in silts NW, Quita and some upper Trinchera and lower Arroyo Blanco in S and E southeastward upper advance Trinchera of turbidite fan/lower fan; Arroyo Blanco dellaic depositionfan deposition in NW, in S lower and Trinchera E. Sombrerito Fm. lagoonal and shallow marine deposits of the Las Salinas Fm. lagoonal and shallow marinelacustrine deposits evaporites of of the Angostura Fm. the lower Las Salinas Fm. and lagoonal/ open ocean pelagic carbonate deposition, high fluvial in NW and E regions, deltaic Arroyo high southeastward advance of della/turbidite low siliciclastic sedimentation commences; high open ocean pelagic carbonate deposition, high high low high ra p id rap id rap id slow subsidence sedimentation sea level depositional environment ra p id rap id ra p id Table 3.5 - Summary of the geologic history of the Azua and Enriquillo Basins. Enriquillo and Azua the of history geologic the of Summary - 3.5 Table a g e middle Pliocene early Pliocene late Miocene middle Miocene slow early Pliocene rapid late Miocene rapid ? ? middle Miocene slow rapid Azua Basin Enriquillo Basin middle Pliocene rapid rapid

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 136 faunal types marginal marine inner neritic outer to inner neritic upper bathyal middle bathyal lower bathyal lacustrine to marginal-marine shallow- and marginai-marine to hypersaline(?) marginal-marine lithofacies types deltaic-coastal coastal-offshore sh e lf middle to inner turbidite fan basin plain to middle turbiditepelagic carbonates fan shelf/lagoonal/lacustrine elastics shelf/lagoonal/lacustrine elastics lagoonal/lacustrine evaporitic fo rm atio n upper Arroyo Blanco Fm. lower Arroyo Blanco Fm. upper Trinchera Fm. Quita Coraza Fm. lower Trinchera Fm. Sombrerito Fm. Las Salinas Fm. Jim anf Fm. Angostura Fm. Table 3.6 - Summary of stratigraphic units for the Azua and Enriquillo Basins. Enriquillo and Azua the for units stratigraphic of Summary - 3.6 Table a re a A zua Basin Enriquillo Basin

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(Tireo Formation), are widespread. These probably served as the source for the significant proportion of volcanic rock fragments noted. Hypabyssal stocks of pyroxene diorite and gabbro known in the central Dominican Republic were probably also sand sources. The lack of K-feldspar suggests apotassium-poor magmatic arc source and reflects the dominant plutonic rock types of Hispaniola: tonalites, quartz trondhjemites, and gabbros (Bowin, 1975), all poor in K-feldspar. The paucity of sedimentary rock fragments reflects the dominance of limestone in the sedimentary rocks of the source area. Limestone is very susceptible to chemical weathering processes and is commonly absent in subaerially- derived sandstones of subtropical regions. The facies present in the Trinchera, such as those in the Azua-Barahona highway section west of Fondo Negro, suggest that the formation follows a similar vertical succession as the turbidite fan facies model of Mutti and Ricci Lucchi (1972).The sequence changes from thinly-bedded, fine grained turbidites in the lower part of the formation to thickly-bedded, channel-filling coarse-grained turbidites near the top. Sedimentary structures, bedding patterns, and grain sizes are all similar to those predicted in the Mutti and Ricci Lucchi (1972) model and indicate a transition from the outer to the inner part of the proximal turbidite fan province. Paleobathymetry is consistent with this interpretation, steadily shallowing upward from near the base of the middle bathyal zone, at approximately 1000 m, to the top of the upper bathyal zone, about 200 m (Table 3.5). Laterally, the Trinchera Formation is confined to a narrow, elongate valley that opens out into the Caribbean Sea, bounded on both sides by thrust blocks. The northern block, the Cordillera Central, contains igneous, metamorphic, and sedimentary rocks of an ancient island arc of Cretaceous and Paleogene age. This block was obviously in existence prior to the deposition of the Trinchera Formation. The southern block is composed of pelagic limestones of Paleogene to middle-middle Miocene age that are now thrust up over Mio- Pliocene strata. Paleocurrent data in the Trinchera shows basin axis-parallel flow of deep- sea sands out of the northwest during the late Miocene in the central part of the basin

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(Breuner, 1985), swinging to westward in the late Miocene and early Pliocene near Fondo Negro. This suggests deposition in a narrow basin, opening up into the Caribbean between Fondo Negro and Azua where the turbidity currents began to lose their lateral containment. Because the primary provenance of the sandstone appears to be the Cordillera Central, axis-normal transport on the flanks of the basin is assumed to have carried sand from the Cordillera Central into the center of the basin before the currents turned parallel to the basin axis. Apparently a submarine high located along the trend of the present-day Sierra de Neiba was responsible for this lateral containment of the turbidity currents. The coarsening-upward Trinchera sequence appears to have been deposited by a narrow, prograding turbidite fan that advanced southeastward across Azua Basin through the late Miocene into the early Pliocene, filling the basin behind it (Fig. 3.17b-e; Fig. 3.18c). This same model was proposed by Hsii (1977) for the Plio-Pleistocene turbidite sequence of a similar ramp valley basin, the Ventura of southern California. The sediment influx was probably a response to initiation of rapid uplift in the Cordillera Central. The barrier that apparently formed on the south side of the basin, deflecting turbidity currents, was probably associated with thrusting faulting and rise of the Sierra de Neiba block (Fig. 18c). Indeed, Bourgois and others (1979) have identified late Miocene nappes in the southern part this range. The shallow marine-fluvial deltaic complex of the Arroyo Blanco Formation (Table 3.5) was lain down between the late Miocene and the middle Pliocene, advancing seaward behind the same turbidite fan it fed (Fig. 3.17c-f). Paleocurrents mostly indicate southeastward sediment transport, consistent with the basin axis. In the early Pliocene in the lower Rfo Yaque del Sur Valley, neritic siltstones of the Quita Coraza Formation occur between the Trinchera and Arroyo Blanco Formations (Fig. 3.17e). These siltstones may reflect deposition on the shelf between feeder channels that carried coarse elastics from the coastal-deltaic complex to the deeper turbidite wedge. The low input of coarse elastics in the Quita Coraza Formation may also be influenced by

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isolation of sediment on the shelf during the early Pliocene highstand (Haq and others, 1987). The microfauna, however, indicates continuous upward shoaling in the late Miocene and early Pliocene, suggesting that the rate of sediment accumulation was more rapid than any relative sea level rise. Tectonics appear to exercise the main control on the depositional history of the Azua Basin. Subsidence in the Azua Basin has most likely resulted from isostatic response to the overthiusting of the basin on its northeastern and southwestern flanks. The late Miocene uplift of the Cordillera Central has provided a source of voluminous sediment, and the rapid loading of these sediments into the basin probably accelerated the isostatic subsidence. Concomitant uplift of the Sierra de Neiba provided the paleogeographic constraints needed to produce the present basin geometry (Fig. 3.18). The pre-Pliocene history of the Enriquillo Basin is not as clear as that of the Azua Basin. Lower to middle Miocene pelagic limestones and marls of the Sombrerito Formation are known to the north and south of the valley, suggesting the basin was part of the same open-ocean complex. The early Pliocene and later history of the basin is reflected in the lagoonal-shallow marine complex of the Angostura and Las Salinas Formations (Fig. 3.17f). Bio- and lithofacies suggest that the Enriquillo Valley was intermittently isolated from and reconnected to the sea over this period. Today Hispaniola forms a restraining bend along the northern margin of the Caribbean Plate (Mann and others, 1984; Mann and others, this volume). Our results suggest that it became active in the late Miocene and resulted in the compressional uplift of the Cordillera Central, Sierra de Neiba, and Sierra de Bahoruco blocks with rapidly subsiding ramp valley basins, the Azua and Enriquillo Basins, in between.

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CONCLUSIONS

1) The sedimentary facies of the Azua Basin indicate a shallowing-upward sequence, from pelagic carbonates through volcanic lithic- and feldspar-rich turbidites to coastal deltaic coarse elastics. Strata exposed in the Enriquillo Basin include evaporites and coastal- lagoonal clastic sequences. 2) Planktonic foraminifera indicate that the marine sequence in the Azua Basin ranges in age from early Miocene to middle Pliocene and demonstrates a southeastward time- transgression of lithostratigraphic boundaries. Ostracodes in the marginal-marine strata in the upper part of the sequence suggest early to middle Pliocene ages; those in the Enriquillo Basin suggest early Pliocene and younger ages. 3) Paleoenvironments represented in the Azua Basin range from near the lower- middle bathyal boundary in the lowest part of the sequence to coastal-fluvial at the top, and migrate southeastwardly through time. In the Pliocene and younger sediments of the Enriquillo Basin, fluctuations from near-normal marine to brackish and hypersaline environments are suggested by the ostracode faunas. 4) The region evolved in two phases: a pre-late Miocene open ocean pelagic stage, and a subsequent laterally-constrained clastic basin stage. The change from the first to the second was probably brought on by rejuvenation of the uplift of the Cordillera Central in the late Miocene supplying large volumes of coarse clastic sediment. Contemporaneous uplift of the Sierra de Neiba produced two separate narrow basins, the Azua and the Enriquillo. The Azua Basin was filled by a southeastward- prograding clastic wedge from the late Miocene to the middle Pliocene. In the Enriquillo Basin, only the post-Miocene neritic-lagoonal history is known well. 5) A period of renewed tectonic activity along the Northern Caribbean Plate Boundary Zone appears to have commenced in the late Miocene, causing uplift of thrust blocks in the Hispaniola restraining bend.

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ACKNOWLEDGMENTS

Research support was supplied by the National Science Foundation (grant number EAR 8720201). Funding for McLaughlin also included the Chevron USA, Inc. Field Scholarship Fund and the McKee Micropaleontologic Scholarship Fund through the Geology Endowment at Louisiana State University, an ORF grant from the university’s Office of Graduate Planning, and a Cushman Foundation Student Research Grant. Additional support for van den Bold was provided through the LSU Geology Endowment. Special thanks are due to P. Mann (University of Texas Institute for Geophysics, Austin) for his encouragement and valuable cooperation in this study. The advice and support of B.K. Sen Gupta (LSU - Baton Rouge) are also appreciated. The assistance of the Direction General de Minerfa, Dominican Republic, is gratefully acknowledged, with special thanks to I. Tavares and E. Garcia of the Departmento de Geologfa. Appreciation is also extended to E. Deveaux, L. Pena and J. Rodriguez (Santo Domingo, Dominican Republic) for their ideas and aid in the field. Ostracode samples were kindly provided by R. Maddocks and C. Glenn (Univ. of Houston) This paper has benefitted greatly from critical reviews of an earlier draft by P. Mann, G. Keller (Princeton Univ.), and J. Saunders (Naturhistorisches Museum, Basel). We would also like to thank J. E. Hazel (LSU - Baton Rouge) for comments on the manuscript, A.J. Bouma (LSU - Baton Rouge) and D. Lowe (Stanford Univ.) for advice on the sedimentology, and J.A. Nunn (LSU - Baton Rouge) for a helpful discussion on basin tectonics.

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Mann, P., Deveaux, E., McLaughlin, P., Cooper, C., Lebron, M.C., Rodriguez, J., and Burke, K., this volume. Geology of the Enriquillo - Azua Basins, 1: Structure, stratigraphy, and tectonics m Mann, P., Draper, G., and Lewis, J.F., Geologic and tectonic studies in Hispaniola. Geological Society of America Special Paper, in review.

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Phleger, F.B., 1951. Ecology of foraminifera, northwest Gulf of Mexico; Part 1 - Foraminifera distribution: Geological Society of America, Memoir 46, v.l, p. 1-88.

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FORAMINIFERAL PALEOENVIRONMENTS OF THE AZUA BASIN SEQUENCE, MIOCENE -PLIOCENE, DOMINICAN REPUBLIC

(to be submitted to Journal of Paleontology)

150

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ABSTRACT

The Azua Basin is an elongate sedimentary trough filled with over 2,500 m of Miocene and Pliocene sedimentary rocks. Principal Components Analysis of rich benthic foraminiferal faunas aided in the recognition of significant species associations in the Sombrerito, Trinchera, Quita Coraza, and Arroyo Blanco Formations. These species associations are based on the loading of species on six factors. Factor 1 represents a "shelf- edge" assemblage, with strong positive factor loadings on Bolivina minima (0.88), Cassidulina norcrossi var. australis (0.73), and Gvroidina regularis (0.71). Lower bathyal species such as Pleurostomella altemans (-0.64), Bolivina paula (-0.62), and Cibicides wuellerstorfi (-0.49) show strong negative loadings. Factor 2 represents middle to upper bathyal assemblages; Oridorsalis umbonatus (0.68), Hoeglundina elegans (0.57), and Uvigerina peregrina (0.51) all have strong positive loadings. Factors 3,4, and 5 all have positive loadings of neritic species. Factor 3 represents a middle to outer neritic assemblage that includes Angulogerina iamaicensis (0.83), Hanzawaia sp. A (0.77), Cassidulina subglobosa (0.59), Cassidulina carinata (0.54), and Cibicidoides pachvderma forma sublittoralis (0.51). Factor 4 has heavy loadings on inner neritic species including Havnesina depressula (0.74), Buliminella eleeantissinaa (0.73), and Rosalina concinna (0.66). Species having strong associations with Factor 5 include Cancris sagra (0.69),

Bolivina lowmani (0.59), and Gavelinopsis sp. A (0.52). Factor 6 represents a current- winnowed assemblage. Plots of the factor scores in the stratigraphic sections demonstrate shoaling upward from lower bathyal to inner neritic depths; this trend is paralleled by decreasing diversity and by lithofacies progressions. Cluster analysis reveals sample groupings that correspond almost directly to the faunal zones identified in the Azua Basin by Bermudez (1949). Seven major clusters were indicated. Cluster 1 is predominantly Sombrerito samples, Cluster 2 corresponds to the

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Basal Trinchera Zone, and Cluster 3 matches the Gaspar Zone. Clusters 4 and 5 split the

Bao Zone, Cluster 7 represents samples from the Quita Coraza Zone, and Cluster 6 is mostly composed of Arroyo Blanco samples. Placed within the biostratigraphic framework for the basin, these benthic foraminiferal trends indicate migration of paleoenvironments toward the Caribbean during the Miocene and Pliocene. This parallels a similar time-transgression of lithofacies and appears to represent rapid filling of a "ramp valley" basin by sediments derived from the uplift of the nearby Cordillera Central, coincident with activation of the Hispaniola restraining bend. Comparison of the Azua Basin faunas to those of a number of other circum- Caribbean Neogene sequences indicates that the deep-water fauna of the region is relatively homogenous with a strong modem aspect; the shallow-marine fauna is relatively unique for the region, reflecting the dominance of clastic versus carbonate sedimentation.

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INTRODUCTION

This study focuses on the benthic foraminiferal record and paleoenvironments of an elongate sedimentary trough, the Azua Basin, located on the Greater Antilles island of Hispaniola in the southwestern part of the Dominican Republic. The Azua Basin provides an ideal setting for the study of the paleoenvironmental significance of Caribbean region Neogene foraminiferal faunas. The basin covers a broad geographical extent, ranging nearly 80 km northwestward into the island from its Caribbean Coast, and includes a nearly continuous lower Miocene to middle Pliocene marine sedimentary sequence of up to 4000 m thickness (Fig. 4.1). The semi-arid climate of the valleys of southern Hispaniola leaves the Neogene strata well-exposed and little-weathered. The foraminifera in these strata are generally abundant and well preserved. Resolution of paleoenvironmental trends through analysis of the foraminifera should aid in reconstructing the geologic evolution of southern Hispaniola during the Neogene. The foraminifera were examined in over 150 samples which were collected in the region bounded by Azua, San Juan, and Barahona. The statigraphic sequence is predominantly siliciclastic; the lowermost strata are pelagic limestones and marls, which are succeeded upward by a turbidite sequence and a coastal marine deltaic complex. The biostratigraphy of this sequence has been outlined in McLaughlin (1989) and follows the zonation of Bolli and Saunders (1985). This paleoenvironmental is primarily based on the benthic foraminifera in 54 samples chosen from our collection as the most fossiliferous, best preserved, and most geologically important.

METHODS

The samples were each disaggregated by boiling in a solution of "Quatemary-O" or

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70 40 to Santo Domingo BAY ^.jM ueuos Fig- 3 \ JDOM. \ \ OCOA \ CENTRAL HAITI / HAITI \ CORDILLERA SIERRA MART NGARC A Barahona Arroyo JRD-125 Sombreritoi^RD-124 DM2-1 «* DM243 9r»J

flaoS

DE NEIBA .n i q s SIERRA t«ARD-126 • L del Rincon to Neiba -18 20 Figure 4.1 - Map of the study area, Azua Basin, southwestern Dominican Republic. Details Details Republic. Dominican southwestern Basin, Azua area, study the of Map - 4.1 Figure are ofthese areas outside localities in 2-5; the samping given ofFigures boxed areas are indicated here. indicated

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by treatment with mineral spirits and washed using a 63 micron (230 mesh) sieve to remove the silt and clay. Dried sample residues were each split to a fraction of approximately 300 specimens. The fauna was sorted, the taxa identified, and the relative abundances of each form tabulated. Three numerical tools have been used in our analysis of Neogene paleoenvironments: measurements of species diversity; principal components analysis; and cluster analysis. The measurement of species diversity in each sample included calculations of species richness (S), the Shannon-Wiener Information Function (H(S)), and equitability (E'). The Shannon-Wiener Information Function is given by the equation: H(S) = -Z pi lnpi It has the advantage over simple species richness (S) in that it gives a measure of diversity that is minimally influenced by sample size (Gibson and Buzas, 1973). Equitability expresses the degree of equal distribution of the species in a sample, using the equation (Gibson and Buzas, 1973): E' = eH(S)/S Principal components analysis was based on a limited group of species selected by a variance ranking of all species with 1% or greater abundances in at least one sample. The selection of the 53 highest ranked species allows us to meet a requirement accepted by some researchers (Anderson, 1984; Cassell and Sen Gupta, 1989) that the number of variables (here species, m) be less than the number of observations (here samples, n). Percentage data of these 53 species were transformed by loglO to approximate normal distribution. The Principal Components Analysis (PCA) of this data matrix, using the SAS system (SAS Institute, Inc., 1985), creates 53 new variables which are referred to as components or factors; these are orthogonal linear combinations of the original variables that preserve the maximum variance of each variable (Hazel, 1977). After examination of

the scree plot of the variance explained by each factor and evaluation of the factor scores, 6

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factors were retained; these explain 50% of the variance present in our data. Eliminating the

extraneous factors, the 6 factor axes were rotated using the VARJMAX scheme in order to maximize the variance of the loadings on the factors (Davis, 1973). A Q-mode cluster analysis, using Ward's Minimum Variance Method, was done on log-transformed

percentage data of all species with frequencies of greater than 1 % in one or more samples (m=167).

GEOLOGIC SETTING

The geologic setting and stratigraphy of the Azua Basin are discussed in Chapter 2 (McLaughlin and Bold, in review). The geology of this area holds important clues into the timing and nature of movement of the Caribbean Plate along its northern boundary. The island of Hispaniola lies at the intersection of several major tectonic features. The Northern Caribbean Plate Boundary Zone (PBZ) runs along the northern side of the island, as an east-west trending left-lateral stike-slip zone between the Puerto Rico Trench and the Cayman Trough. The island has been referred to as a "restraining bend" in this plate boundary (Mann et al., 1984); the influence of the strike-slip boundary zone on northwesterly-oriented Mesozoic island-arc structures causes transpression (transcurrent movement + compression), forming alternating anticlinal fold-thrust mountain belts and synclinal ramp-valley basins on the southern side of the island. The Beata Ridge Fault Zone extends from the Beata Ridge along the coast and into the Bahfa de Neiba. The trend of the Muertos Trough continues westward from offshore eastern Hispaniola onto land in the Barahona area; it has been suggested that the Muertos Trough is a subduction zone (Biju- Duval et al., 1982), but so far the evidence is inconclusive. The Azua Basin is a NW-SE oriented Neogene sedimentary trough in the southwestern Dominican Republic (Fig. 4.1). It is composed of two areas, a narrow

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northwestern arm in the upper Rio Yaque del Sur and Rio San Juan Valleys and a wider seaward end that extends from Azua to near Barahona. The northwestern arm is a synclinal ramp-valley basin, bounded by Cretaceous to lower Neogene rocks that comprise thrust- blocks of the Cordillera Central to the northeast and the Sierra de Neiba to the southwest. The seaward end of the basin is overthrust on the northeast by the Cordillera Central. To the southwestern side, near the tip of the Sierra de Neiba, the strata dip off the flanks of the Sierra de Martin Garcia and are interrupted by faulting near Canoa. Four formations comprise the Neogene marine sedimentary sequence. The lowest, the Sombrerito Formation, is characterized by soft buff pelagic limestones and marls. Its thickness has been estimated to be over 800 m (Osiris de Leon, 1978). However, this unit generally occurs in scattered outcrops and is faulted in many places. In the southern part of

the basin, a 2 0 0 m thick interval of alternating pink carbonate-debris calcarenites and blue- green marls at the top of the Sombrerito Formation is referred to as the Gajo Largo Member. The Trinchera Formation overlies the Sombrerito. Bermudez's (1949) definition of the Trinchera Formation was broad, including both deep- and shallow-marine deposits. The formation was subdivided into four faunal zones based on foraminifera content: Basal Trincher, Gaspar, Bao, and Quita Coraza. However, these have been misinterpreted by some workers as lithologic units rather than the faunal zones they were meant to be. The Trinchera, as we now define it, is a deep-marine turbidite fan sequence that includes strata in which Bermudez identified his lower two zones, the Basal Trinchera and Gaspar, as well as the lower occurrences of his Bao Zone. It is represented by 1300 - 2200 m of interbedded deep-marine mudstones and turbidite sandstones and is exposed in long, nearly continuous sections. A progression may be traced from outer turbidite-fan facies in the lower part of the formation to inner fan facies in the upper part (McLaughlin and Bold, in

review).

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The strata from which the upper part of the Bao Zone and the entirety of the Quita Coraza Zone were identified are soft, blue-green siltstones referred to as the Quita Coraza Formation and are distinct from the coarser underlying turbidite deposits. Occurrences of this unit are restricted to the lower Rio Yaque del Sur Valley and the Azua area, with thicknesses ranging from 300 - 700 m. Also included in this formation are lithologically indistinguishable beds assigned to the Higuerito Member of the Arroyo Blanco Formation in Bermudez (1949). The Arroyo Blanco Formation overlies the Trinchera in the northwestern arm and the Quita Coraza on the seaward end of the Azua Basin. It is composed of up to 1000 m of nearshore elastics which form a coarsening-upward coastal-deltaic complex that includes numerous fining-upward sequences (McLaughlin and Bold, in review). Scattered coral beds near the base of the formation are best developed in the Quita Coraza area, and gypsum is present in the upper part of its westerly exposures (Loma de Yeso area).

We discuss our samples in terms of 6 composite stratigraphic sections: the San Juan and the La Trinchera sections in the northwestern arm of the basin; and from east to west, the Rio Via, Cerros de los Quemadillos, Quita Coraza and Fondo Negro sections in the seaward end of the basin. The San Juan section is the most fragmented of the study. The Sombrerito samples are from a continuous section along Rio Los Baos (Fig. 4.1) south of San Juan. To the north, sample DMR17 is in the Trinchera Formation, but the contact between the Sombrerito and the Trinchera is buried by alluvium and is assumed to be a thrust fault. The highest Trinchera sample, DM1-1, (Fig. 4.2) was collected to the east at Arroyo Las Lajitas, as was the Arroyo Blanco sample DM1-4. The La Trinchera section (Fig. 4.2) include Trinchera strata exposed in the Arroyo Salado and in the Hato Nuevo de Cortds area. The lowest sample in that section, RD125, is from the type locality of the Sombrerito Formation (Fig. 4.1) which is in fault contact with the Trinchera. The Rio Via section near Azua (Fig. 4.3) is a continuous section that ranges from the upper part of the

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Reservoir

5 .6

SIERRA DE ^ ^V _ volcanic NEIBA s to c k s

T rinchera 2 ,3 .4 ' B lu ff\\ 2km Florentino Limestone outcrops on hilltops -

Figure 4.2 - Map of the northwestern arm of the basin, in the upper Rfo Yaque del Sur Valley and the San Juan Valley. This area includes samples placed in the La Trinchera and San Juan sections.

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•7

‘C Figure 4.3 - Map of the Rfo Vfa section, north Azua. of north section, Vfa Rfo the of Map - 4.3 Figure

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Trinchera to the upper part of the Quita Coraza. Also included in the Rio Via section is a sample from near Higuerito to the west. The name of this area was taken for the Higuerito Member of Dohm (see Bermudez 1949), described as a deep-water facies of the Arroyo Blanco Formation. We now place these strata in the Quita Coraza Formation, but the Higuerito area is structurally disrupted and the stratigraphic position of sample HW-3 in the formation is uncertain. The Cerros de los Quemadillos section (Fig. 4.4) includes samples of uppermost Trinchera strata, the Quita Coraza Formation, and the Arroyo Blanco Formation collected from outcrops in the Cafiada del Burro, Canada Las Palmitas, and Arroyo Las Lajas. The Quita Coraza section (Fig. 4.5) spans the uppermost part of the Trinchera Formation in the Canada de Bergal and roadcuts to the west, and the Quita Coraza and Arroyo Blanco Formations in Canada del Bao. The Fondo Negro section (Fig. 4.5) is the longest in the study area and includes samples covering an area from Fondo Negro to Canoa in the southwest. The Sombrerito Formation, which was studied in the Canoa Dome area, is separated from the overlying Trinchera by a thrust fault. The Trinchera outcrops along the Azua-Barahona Highway can be reliably traced to the Arroyo El Puerto outcrops in constructing this composite section, with the exception of a portion of the section at sample RD59 and below, which is disrupted by faulting. However, the lower part of the Trinchera is not exposed in this area and has probably been faulted out. The Quita Coraza Formation was sampled in bluffs along the south side of the Rio Yaque del Sur, and the Arroyo Blanco on the north side at Arroyo Barranca.

BIOSTRATIGRAPHY

Planktonic foraminifera indicate that the Azua Basin sedimentary sequence extends from lower Miocene to middle Pliocene (McLaughlin, 1989). Samples from the Sombrerito Formation range from lower to upper Miocene. The oldest samples are found in the

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s. \r«, Q. => SB N P ' O ' o

CO -O1 UJ ~ D €

Figure 4.5 - The southern part of the basin-, in the lower Rio Yaque del Sur Valley. This area includes the Fondo Negro and Quita Coraza sections.

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northwestern arm of the basin near Rfo Los Baos. The presence of Globigerinoides bisphaericus. Praeorbulina transitoria. and Globigerinatella insueta place these strata in the lower Miocene Globigerinatella insueta zone. Further east, at Arroyo Sombrerito, the presence of Globorotalia fohsi peripheroacuta and Globorotalia praemenardii suggest equivalence to the Globorotalia fohsi fohsi zone. In contrast, the faunas present in the southern exposures of the Sombrerito are indicative of the middle and upper Miocene. Globorotalia fohsi robusta and Globorotalia menardii are present in samples collected near Canoa, placing them in the upper part of the Globorotalia fohsi robusta zone. Several kilometers to the northeast, the Gajo Largo Member was found to range from the middle Miocene Globorotalia maveri zone into the lower part of the upper Miocene Globorotalia acostaensis zone, where small 4 chambered forms of the nominate species are present. The depsition of the Trinchera Formation was diachronous between the landward and seaward ends of the Azua Basin. In the northwestern part of the basin, the lower part of the Trinchera ranges from near the middle Miocene - upper Miocene boundary (Globorotalia menardii chronozone or lower part of the Globorotalia acostaensis chronozone), based on the presence of Globorotalia lenguaensis. to the uppermost Miocene (upper part of the Globorotalia humerosa chronozone), based on occurrences of Candeina nitida. This same interval spans the Miocene / Pliocene boundary in the southern part of the basin, where Globorotalia margaritae margaritae first appears 300 m above the base of the 2200 m thick Trinchera section. Upper Trinchera samples collected in the northwestern arm of the basin are placed in the uppermost part of the Miocene (upper part of the Globorotalia humerosa zone), based on the presence of Candeina nitida and the absence of any Pliocene marker species. Outcrops in the southern end of the basin are lower Pliocene, within the upper three-fourths of the Globorotalia margaritae zone. Globorotalia margaritae margaritae and Globigerina nepenthes are present, and Globigerinoides ruber reappears approximately

2 0 0 m below the top of the formation.

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Planktonic foraminifera are present in reduced numbers and diversity in the Quita Coraza Formation. Globorotaliids are generally restricted due to shoaling. However, the position of the Quita Coraza above the first-occurrences of Globorotalia margaritae margaritae and Globigerinoides Tuber, and the presence of Globigerina nepenthes indicate a position somewhere in the upper part of the lower Pliocene Globorotalia margaritae chronozone. Spotty planktonic foraminiferal occurrences in the lower part of the Arroyo Blanco Formation suggest it may also follow a southward-younging trend. The presence of Candeina nitida and absence of Pliocene markers in the northern part of the basin indicate a position in the upper part of the upper Miocene Globorotalia humerosa chronozone. The stratigraphic position and the persistence of Globigerinoides obliquus obliquus and Globoquadrina altispira altispira suggest that the more southerly exposures lie in the upper part of the lower Pliocene Globorotalia margaritae chronozone.

BENTHIC FORAMINIFERAL SPECIES

The faunas of the Azua Basin represent a wide range of paleoenvironments, from lower bathyal to nearshore, and most of the samples show high species diversities. Faunal counts in the sample splits show that 167 species or varieties of benthic foraminifera are present at the 1% level of abundance, that is each of the constitutes Wo or more of the assemblage in at least one sample. In addition, a number of rarer species were identified in supplementary scans of whole samples. A species list is provided in Appendix 1, with the rare (< 1%) species denoted with an (r). The original citations of these species are provided, as are signifigant synonyms where appropriate. However, the taxonomic status

of a number of the species is quite complex and is discussed in detail in Chapter 6. The suprageneric placements of the species are found in Loeblich and Tappan (1987).

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DIVERSITY TRENDS

An overall upward decrease in diversity is evident in the Azua Basin sedimentary sequence. Species richness, S, diminishes from 177 in mixed faunas in the Sombrerito Formation (RD 125; Fig. 4.6) to as low as 29 in the Arroyo Blanco Formation (RD 101; Fig. 4.7). The Shannon-Wiener Function, H(S), which is much less affected by sample size than S, ranges from 4.71 in the Sombrerito (RD125; Fig. 4.6) to as low as 1.94 also in the Sombrerito Formation (RD 113; Fig. 4.7). Values of H(S) in the Trinchera Formation indicate high diversity but show no signifigant upsection trends; over 75% of the values lie in the 3.5 to 4.0 range, with outliers of low diversity down to 2.60 (RD59; Fig. 4.7). The diversity steadily drops from the base of the Quita Coraza Formation into the Arroyo Blanco. Values of H(S) in the basal Quita Coraza are similar to those in the upper Trinchera, generally just above 3.5, and drop to below 3.0 in the middle of the formation and below 2.5 at the top; one notable exception is a value of 2.51 in middle Quita Coraza sample DM13-1 (Fig. 4.8). Values of H(S) in the Arroyo Blanco are low, several lying between 1.9 and 2.3 (Fig. 4.7,4.8). However, slightly higher values (2.62,2.71) are noted in samples from the reefal base of the formation (Fig. 4.7,4.9) and in the northwestern part of the basin (2.57, Fig. 4.10). Several samples show anomalously low diversity, often due to the dominance of one or several species. For example, Sombrerito samples RD126 and RD113 as well as lower Trinchera sample RD59 all have H(S) values of less than 3.0, which are related to the strong dominance of Bolivina plicatella var. mera £15-33%) and Bolivina paula (25-54%). Low diversity outliers of the upper Trinchera and Quita Coraza (DM13-1) reflect the dominance (16-33%) of Cassidulina carinata in the samples. In a study of diversity trends of benthic foraminifera, Gibson and Buzas (1973) demonstrated a general increase of diversity in deeper waters for Recent faunas studied in

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F1 F2 F3 F4 F5 H(S) S E' lioo 1000 1 4 0 0 1200 1000 R D 7 - too R D 1 2 9 ' t o 1 3 1 000 400 R D 7 ' 200 R D 1 2 5 ' On •10 1 -10 1 1 0 1 1 0 1 1 0 1 0 1 2 3 4 0 50 100150 0 0.5

Arroyo Blanco Fm. m Quita Coraza Fm. Em Trinchera Fm. 11 ‘ 11 Sombrerito Fm.

Figure 4.6 - Plots of factor scores (F1-F5) and measures of diversity (H(S), S, and E') for the La Trinchera section. The lower part of the section is discontinuous, with a thrust-fault contact between the Sombrerito and Trinchera Formations.

F1 F2 F3 F4 F5 H(S) S E'

r rD, o ,-_

R D 7 9 - ; < < * R D 7 6 “ R D 7 4 - R D 7 0 “ RD66_ ^ ^ R D 6 A - R D 5 9 r '.iir.ir3T.ifi R D 1 1 9 * £ £ £ $ R D 1 1 7 - D M 3 * 2 R 0 1 1 5 « 3 = m c

R D 1 1 3 e t ES x D M 6 -1 1 101 -1 01 -1 01 -1 01 -1 01 01234020400 OS

M il Arroyo Blanco Fm. t^ jt Oita Coraza Fm. E#d TrincharaFm. | Sombrerito Fm.

Figure 4.7 - Plots of factor scores (F1-F5) and measures of diversity (H(S), S, and E') for the Fondo Negro section. The lower part of the section is discontinuous; the contact between the Sombrerito and Trinchera Formations is a thrust fault, and the Sombrerito Formation is also broken up by faulting.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. I I Arroyo Blanco Fm. Quita Coraza Fm. Trinchera Fm. Sombrerito Fm.

Figure 4.8 - Plots of factor scores (F1-F5) and measures of diversity (H(S), S, and E’) for the Cerros de los Quemadillos section.

F1 F2 F3 F4 F5 H(S) S E'

1200

R D 4 6 . 1000 D M 1 1 - 2 ' D M 1 2 - 1 ' BOO R D 4 2 ' 6 0 0

R D 3 8 400 R D 3 6 200

R D 3 3 0 5

H ill Arroyo Blanco Fm. t-VH Quita Coraza Fm. Trinchera Fm. f e t Sombrerito Fm.

Figure 4.9 - Plots of factor scores (F1-F5) and measures of diversity (H(S), S, and E') for the Quita Coraza section.

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F1 F2 F3 F4 F5 H(S) S E' DMM 2SOO

2000 DM1-1 1500

1000

500 Om •1 o 1 •1 o 1 •1 o 1 •1 0 1 -10 10 05

| Arroyo Bianco Fm. m O ita Coraza Fm. m Trinchera Fm. Sombrerito Fm.

Figure 4.10 - Plots of factor scores (F1-F5) and measures of diversity (H(S), S, and E') for the San Juan area section. The lower part of the section is discontinuous, with a thrust- rault contact between the Sombrerito and Trinchera Formations. The straticraphic thickness between samples DMR17 and DM1-1 is an estimate, as the Loma La Basura area and Arroyo Las Lajitas subsections are separated by nearly 5 km along strike

F1 F2 F3 F4 F5 H(S) S E' 1000 RD22 RD21 too R019' 600

RD16-

200

On 0 5

Arroyo Blanco Fm. O ita Coraza Fm. m T rinchera Fm. Sombrerito Fm.

Figure 4.H - Plots of factor scores (F1-F5) and measures of diversity (H(S), S, and E') for the Rfo Via section.

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traverses along the Atlantic and Gulf coasts of North America. The results were compared with diversity trends in the Miocene of the Atlantic Coastal Plain; a correlation between greater paleodepths and higher diversity values was evident in an areal analysis of the Calvert and Yorktown Formations (and their equivalents), and in an analysis of a section through the Pungo River and Yorktown Formations at Lee Creek Mine, North Carolina. Our samples from the Quita Coraza and Arroyo Blanco Formations have a comparable (but slightly higher) range of values of S and H(S), reflecting deposition at similar neritic depths; the values in the Trinchera and Sombrerito are significantly higher. Overall, then, the upsection decrease in diversity supports other geologic evidence for shoaling in the Azua Basin.

PRINCIPAL COMPONENTS ANALYSIS

Principal Components factor analysis of our sample data reveals foraminiferal assemblages that are consistent with diversity trends. Six factors were extracted, and the resulting factor loadings of 53 benthic foraminiferal species used are shown in Table 4.1. Known environmental preferences of species with strong positive and negative loadings on any factor allow us to interpret its paleoenvironmental signifigance. The influence of each factor in the stratigraphic sections is displayed in plots of the factor scores of each sample in Figs. 4.6-4.11. Species with strong positive loadings on Factor 1 include Bolivina minima. Cassidulina norcrossi var. australis. Gvroidina regularis. Gvroidina umbonatus. Bolivina alata. Uvigerina auberiana. Uvigerina parvula. Siphonina pulchra, and Melonis affinis. Members of of this assemblage found in Recent faunas of the Gulf and Atlantic coasts of North America are most strongly associated with uppermost bathyal and outermost neritic environments (van Morkhoven et al., 1986; Parker, 1948,1954; Pflum and Frerichs,

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F a c to r 1 F a c to r 2 F a c to r 3 F a c to r 4 F a c to r 5 F a c to r 6 Bolivina minima 0.87537 0.03252 -0.10038 -0.24086 -0.05708 0.10629 Cassidullna norcrossl var. australis 0.72514 0.21638 -0.02320 -0.07846 -0.01167 •0.07271 Gyroidina regularis 0.71288 0.04207 -0.04100 I -0.34290 I -0.06255 0.05929 Gyroidina umbonata 0.59624 -0.17705 I 0.39095 I -0.09271 0.09119 -0.05363 Clbiddoldes bametti 0.56735 -0.26057 -0.13302 -0.07172 -0.00290 I 0.38864 Bolivina alata 0.56312 0.28581 -0.20205 0.00182 0.08841 020956 Uvigerina azuana 0.55832 0.01188 -0.25463 0.02346 -0.12023 -0.20875 Siphonlna pulchra 0.55654 -0.04602 0.19657 -0.03171 -0.17537 0.01436 Uvigarina parvula 0.49304 -0.32316 0.07883 -0.14636 0.02273 -0.09079 Uvigarina aUberiana 0.47989 0.31529 -0.20646 ■0.25479 -0.17836 -0.24349 Welonis aflinis 0.45730 0.03314 I 0.36457 I -0.01439 -0.24337 026296 Bolivina sp . 0 -0.33095 -0.21135 0.13414 -0.24375 -0.08817 -0.19626 Cibiddes wuellerstorti -0.49222 I 0.39109 I -0.00822 -029978 -0.03215 -0.08790 Bolivina marginata var. multicostata -0.49550 0.11271 -0.12997 -0.17546 -0.15667 -0.07138 Bolivina piscHormis -0.49613 I 0.31630 I -0.03323 1 -0.32689 -0.11308 -0.15683 Bolivina sp . A -0.60214 -0.25962 -0.36508 -0.08812 -0.18693 -0.06789 Bolivina paula -0.61717 -0.25475 -0.37359 -0.04879 -0.09326 -0.02668 Plaurostomella altemans -0.63522 0.15719 -0.12159 I -0.30119 -0.02651 -0.03790 Recurvoides trincherasensis 0.05660 0.71237 -0.02933 -0.08151 -0.09489 -0.07882 Oridorsalts umbonatus 0.06593 0.67886 -0.22480 -0.15361 0.02245 -0.10563 Bulimina sodalis 0.03366 0.61909 -0.10378 -025535 0.00135 0.11589 Hoeglundina etegans 0.08461 0.57029 -0.00826 0.01425 -0.00667 •0.00402 Sigmollopsis schlumbergeri -0.02543 0.56745 -0.12873 0.00472 -0.15862 0.07412 Bermudezinalla riveroi -0.24094 0.56581 -0.09095 -0.08858 0.01344 -0.04513 Gyroidina trincherasensis 0.12777 0.53208 -0.10815 -022919 -0.16433 -0.18394 Uvigerina peregrina -0.08581 0.50689 0.12568 0.02011 -0.12663 0.15124 Cbiddoides pachyderma (orma bathyalis 0.03940 0.46094 ■0.14455 -0.19872 I -0.33061 -0.18997 Gavelinopsis transluscens 0.17062 0.24817 -0.09925 -020037 -0.21595 -0.08207 Angulogerina jamaicensis -0.04815 -0.13912 0.83072 0.12387 -0.08652 0.03415 H anzaw aiasp. A -0.07820 0.02930 0.77426 0.13254 -0.12756 -0.10550 Cassidullna subglobosa 0.21621 -0.19668 039921 -0.32123 0.18111 -0.08739 Cassidullna carinata I 0.34758 I -0.38631 I 0.54452 -0.31029 0.25293 -0.01331 Cbiddoides pachyderma forma sublittoralis 0.18657 -0.14107 0.51010 0.04544 1 0.50337 1 -0.07582 Nonion sp. 0.07066 -0.10247 0.39120 0.21238 0.18472 -0.11242 Gyrddina sp. d. G. umbonata -0.02929 -0.12727 0.28551 0.00843 -0.05709 0.04173 Bolivina plicatella var. mera -0.23875 -0.27332 I -0.47925 I 0.04662 -0.33856 •0.19364 Haynesina depressula 0.06120 -0.28360 0.13696 0.73912 -0.06851 -0.14637 Buliminella elegantissima 0.03307 -0.17622 -0.14357 0.72947 -0.08704 -0.07079 Rosalina condnna 0.06618 -0.40992 I -0.06919 0.65689 -0.14687 -0.15784 R eussella spinulosa 0.06495 -0.25368 I 0.33249 I 0.52341 -0.24356 -0.19269 Ammonia paridnsoniana -0.05753 0.28371 0.04087 0.44233 0.08619 024239 Bolivina inflata f -0.36761 I -0.18121 0.01932 -0.37379 -0.15697 -0.20527 Bolivina abatrossi 0.23738 0.20118 -0.10411 -0.42120 -0.18539 -0.13166 Bolivina? sp . K -0.02029 -0.13291 -0.03652 0.00603 0.70004 -0.09832 Cancris sagra -0.03418 -0.19529 0.04390 0.08490 0.68595 0.02187 Bolivina lowmani -0.01001 -0.13622 •0.19148 -024327 0.59236 -0.20752 Gavelinopsis sp. A 021662 -0.23907 -0.02082 -0.13321 0.51865 0.09625 Uvigerina pigm aea 029218 I -0.31389 I -0.02277 1 -0.33751 I -0.33894 0.07766 Cibiddes lobatulus 026948 -0.23182 0.02797 -024335 -0.45409 -0.26803 Asterigerina carinata -0.03939 -0.36331 -0.25035 0.11599 -0.49794 -0.21456 Uvigerina vlaensis 0.07285 -0.83200 -0.07023 0.04708 0.01266 0.89626 Bolivina obscuranta 0.11188 -0.10185 ■0.07343 -0.04272 -0.01938 0.88996 Valvulineria mexicana I 0.32930 I 0.26876 I 0.39564 I -0.04363 -0.13409 0.47208 % variance explained 14.5 12.1 7.0 6.2 5.7 4.6

Table 4.1 - The rotated factor solutions for Factors 1 - 6 . Assemblages may be recognized by strong positive or negative associations with the factors; significant factor loading values are encosed within boxes. Knowing the environmental significance of some of the assemblage members allows use of die factors as paleoenvironmental indicators,

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1976; Phleger, 1951; Phleger, Parker, and Peirson, 1953). Two fossil species, Cibicidoides bametti and Uvigerina azuana also have strong positive loading, so can be regarded as bathyal-neritic boundary forms, as well. Strong negative loadings are evident for species usually associated with Recent middle bathyal or deeper faunas, including Cibicides wuellerstorfi. Pleurostomella altemans. and Bolivina paula. We also find Bolivina sp. A. Bolivina sp. C. Bolivina pisciformis. Bolivina marginata var. multicostata. and Bolivina inflata to have strong disassociations with Factor 1. From this, it appears that the bathyal-neritic boundary fauna, which is associated with clastic sediments, contrasts strongly with a lower-middle bathyal fauna, which is associated with more carbonate-rich pelagic sediments. Factor 1 explains 14.5% of the variance in our data. Factor 2 is interpreted as the middle to upper bathyal factor. The assemblage of species with strongly positive factor loadings includes Oridorsalis umbonatus. Hoeglundina elegans. Bulimina socialis. Sigmoilopsis schlumbergeri. Bermudezinella riveroi. Gvroidina trincherasensis. Uvigerina peregrina. Cibicidoides pachyderma forma bathvalis. and Cibicides wuellerstorfi. All have been reported as important faunal constituents of various continental slope faunas of the Gulf of Mexico and the North Atlantic (van Morkhoven et al., 1986; Parker, 1948,1954; Pflum and Frerichs, 1976; Phleger, 1951; Phleger, Parker, and Peirson, 1953). Recurvoides trincherasensis, which has only been reported in the Mio-Pliocene of southern Hispaniola, also loads heavily on Factor 2 and can be characterized as a middle to upper bathyal species. Typically shallow- water species have negative loadings. Factor 2 explains 12.1% of the variance. Factor 3 represents a middle to outer neritic assemblage. Cassidulina subglobosa. Cassidulina carinata. Cibicidoides pachyderma forma sublittoralis and Reussella spinulosa. forms that in the Recent may reach greatest abundance between 100 and 200m (Boltovskoy and Wright, 1976; Murray, 1973; Parker, 1948; Phleger, 1951), all have strong positive loadings on Factor 3. Shelf edge faunal constituents such as Gvroidina umbonata.

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Valvulineria mexicana. and Melonis affinis are also part of this assemblage. We find that these species most often occur in neritic mudstones, so this factor is probably also related to fine grain substrates. Fossil species that load heavily on Factor 3, such as Angulogerina jamaicensis and Hanzawaia sp. A can be considered neritic species with a preference for fine-grained substrates. Three species of Bolivina that can be very abundant in our Sombrerito samples (B. paula. B. plicatella var. mera. and B. sp. A) have negative loadings. Factor 3 accounts for 7% of the variance. Factor 4 contains heavy loadings on inner neritic species such as Havnesina depressula. Buliminella elegantissima. Rosalina concinna. Reusella spinulosa.and Ammonia parkinsoniana forma tvpica. Two species present in the neritic assemblage of Factor 3, Cassidulina subglobosa and Cassidulina carinata. have negative loadings, which indicates a strong disassociation with the Factor 4 assemblage. Factor 4 accounts for 6.15% of the variance. Bolivina sp. K, Cancris sagra. Bolivina lowmani, Gavelinopsis sp. A and Cibicidoides pachyderma forma sublittoralis are important components of Factor 5. These form a neritic assemblage distinct from that of Factor 3. Although the exact significance of Factor 5 is unclear, it may be associated with a slightly shallower, more stressed environment with a higher sedimentation rate than Factor 3. Species in this assemblage are common in middle to inner neritic environments; associated strata are coarser grained, with more silt and very fine sand. Gavelinopsis sp. A is a species similar to G. praegeri. but has a greater number of chambers, a larger umbilical plug, and a rounder periphery; G. praegeri has been associated with sandy and shelly substrates (Murray, 1973). However, this is inconsistent with the importance of Bolivina lowmani. which has been correlated to areas of finer-grained substrata and high sedimentation (Lankford, 1959; Sen Gupta, 1979; Sen Gupta and Strickert, 1982). Cibicides lobatulus and Asterigerina carinata. two species often associated with areas of carbonate or reefal sedimentation (Brasier, 1975; Sen Gupta and

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Schaefer, 1973), have strongly negative loadings.Factor 5 accounts for 5.7% of the variance.

Factor 6 appears to represent the effect of sediment winnowing rather than paleoecology. Uvigerina viaensis and Bolivina obscuranta. both large robust species usually found as rare constituents of Azua Basin shelf-edge type faunas, have very large factor loadings. They are most common in sandstones where smaller, more delicate forms

have been removed by current activity. Factor 6 accounts for 4.6% of the variance and will not be treated further in our paleoenvironmental discussions. The Principal Components Analysis (PCA) allows us to recognize an upsection progression from lower bathyal to inner neritic environments (Figs. 4.6-4.11). Strongly negative scores of Factor 1 in the Sombrerito Formation (Figs. 4.6,4.7,4.10) indicate the strength of the negatively-loaded, lower to middle bathyal assemblage. Factor 3 generally has negative loadings in the Sombrerito, reflecting the abundance and in some cases near dominance of three Bolivina species: B. paula. B. plicatella var. mera. and B. sp. A. The samples with the most negative Factor 3 scores, RD126 and RD113, both also have anomalously low diversities for such deepwater deposits. Bolivina-dominated faunas have been related to low oxygen conditions (Bandy and Amal, 1957), where reduced diversity would also be expected. It is possible, then, that periods of low oxygen bottom water conditions affected the Azua Basin in the early and middle Miocene. Species present in the Sombrerito Formation but not used in the PCA include: Cibicides cicatricosus. Planulina renzi. Uvigerina hispida. Cibicidoides mundulus. Laticarinina pauperata. Gvroidina altiformis. Siphonina bradvana. Karreriella bradvi. Siphonodosaria lepidula. S. nuttalli. JL. vemeuili. S. paucistriata. Sigmavirgulina tortuosa. Sphaeroidina bulloides. Pullenia bulloides. Qsangularia culter. Cibicidoides bradvi. Pullenia subcarinata. Chilostomella czizecki. Bolivina goessi. Anomalina flintii. and Pvrgo murrhina. The presence of these

species also suggests paleodepths in the area of 1 0 0 0 m.

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The negative influence of Factor 1 persists but in decreasing importance, into the lower and middle parts of the Trinchera Formation (Figs. 4.6,4.7). These faunas are interpreted to reflect depths in the lower part of the middle bathyal zone and include many of the same non-numerically analyzed species as the Sombrerito Formation. In the northwestern arm of the basin, a negative peak in Factor 5 is evident in samples RD7 and RD131 (Fig. 4.1) from the lower Trinchera.The peaks reflect the presence of downslope- transported reefal and shallow-marine carbonate species such as Cibicides lobatulus and Asterigerina carinata. This is not unexpected for sample RD131; it was collected just below the base of a several kilometer wide slip mass of reefal material referred to as the Florentino Limestone (Bermudez, 1949). Sample RD130 (Fig. 4.2), which was collected about 10 m below the RD131, shows a strong negative peak on Factor 4. This reflects the abundance of several bathyal Bolivina species that have negative loadings on this factor, namely B. inflata. B. pisciformis and B. albatrossi. In the Fondo Negro section of the southern part of the basin, the basal part of the Trinchera has been faulted out and is not exposed. Lower Trinchera sample RD119 has an unusually high abundance of Uvigerina auberiana (26.6%); this species has positive loadings on both the "shelf edge" factor (Factor 1) and the middle to upper bathyal factor (Factor 2), so RD119 scores unusually high on the plots of these factors (Fig. 4.7). The middle and upper parts of the Trinchera Formation are characterized by an increase in positive scores of Factor 2 (Figs. 4.6,4.7,4.10) compared to the lower Trinchera. This indicates further shoaling in this interval through the middle and upper bathyal zones. Sample RD12 (Fig. 4.6) shows a notable negative loading on Factor 5 reflecting the presence of transported specimens of Cibicides lobatulus. The uppermost Trinchera is strongly associated with Factor 1, the "shelf edge" factor, and the values of Factor 2 decrease significantly ( Figs. 4.7,4.8,4.9). Only a few scattered scores outside of+/ -1 are evident from other factors in the middle and upper Trinchera: negative excursions at sample RD38 for Factors 2 and 4, due to a high abundance of C. carinata; a

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negative kick in Factor 3 for sample RD42, probably due to the occurence of Bolivina plicatella var. mera and B. paula: negative values of Factors 2 and 5 in the Rio Via section (RD14 and RD16), due to high abundances of Astergerina carinata and Cibicides lobatulus: and a negative peak in Factor 4 for sample RD16, probably related to the importance of Cassidulina subglobosa and C. laevigata The evidence from the Rio Via suggests that downslope transport is a significant contributor to the foraminiferal fauna, which is compatible with its location closer to the high relief of the Cordillera Central Species associations in the lower part of the Quita Coraza Formation (Figs. 4.7,4.8, 4.9,4.11) differ little from those of the upper Trinchera Factor 1 continues to be the major assemblage, with scores near or greater than 1.0. Near the base, Factor 3 is insignifigant, but rises in value toward the middle of the formation, tracing a transition to a middle neritic environment from near the bathyal-neritic boundary. Associations in the upper part of the Quita Coraza ( Figs. 4.7,4.8,4.11) vary from inner neritic to middle neritic faunas associated with coarse substrata (Factor 5). The base of the Arroyo Blanco Formation is marked by small coral reefs in a belt trending eastward from the Quita Coraza area to the Cerros de los Quemadillos area (Fig. 4.1). Samples from these areas (Figs. 4.8,4.9) exhibit negative scores on Factor 5, reflecting the presence of negatively-loaded carbonate environment species. Less microfossiliferous samples that were not numerically analyzed contain Ouinqueloculina and large Sorites , suggesting the presence of eel-grass environments (Sen Gupta and Schaefer, 1973). Further to the west (Fig. 4.7) near Fondro Negro, the fauna in a basal Arroyo Blanco siltstone sample scores a strongly positive value on Factor 5, suggesting a middle neritic setting with a coarse grained substrate. Samples of the Arroyo Blanco Formation in the northwestern arm of the basin are poorly fossiferous. Sample DM1-4 has a factor score

of over 6.0 on Factor 6, which appears to represent a current winnowed, upper bathyal or outer neritic fauna. Otherwise, it shows no strong relationship to any other factors. Melonis

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affinis. Cibicidoides bametti. Cassidulina carinata. Cibicidoides pachyderma forma bathvalis and Valvulineria mexicana are also present at >2% in DM1-4 and are consistent with an upper bathyal to outer neritic settiing. From this, it would appear that the strata referred to basal Arroyo Blanco in the northwest part of the Azua Basin represent deeper- water environments than those in its more seaward end. The northwestern area is closer to the high relief of the Cordillera Central, and more source-proximal lithofacies were probably able to develop in deeper water. Most samples from higher in the Arroyo Blanco Formation are only sparsely microfossiliferous and contain nearshore and marginal marine species of Elphidium and Ammonia. However, siltstone sample (DM5-11) from high in the Arroyo Las Lajas section contains a fauna that scores highly on Factor 5 (Fig. 4.8). This represents a middle neritic assemblage which may be related to areas of high sedimentation and coarser-grained substrates. The fauna also appears to represent deeper water than most of the underlying samples in the Arroyo Las Lajas. Although we do not have sufficient biostratigraphic control in this part of the section to say for certain, it is possible that the apparent deepening is related to the trangression reported for the middle of the Pliocene by Haq et al. (1987).

CLUSTER ANALYSIS

The results of our Q-mode, Ward’s minimum variance cluster analysis of species percentage data in the Azua Basin samples can be conveniently discussed in the context of the faunal zones reported in the well-known Dominican Republic monograph of Bermudez (1949). Based on a suite of samples collected in early reconnaissance investigations of the geology of the Azua Basin, Bermudez described the foraminifera from the Sombrerito, Trinchera and Arroyo Blanco Formations (as then defined) and divided the Trinchera into four faunal zones, the Basal Trinchera, Gaspar, Bao, and Quita Coraza.

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Our study is based on a more extensive collection of samples with more precise stratigraphic control. We find 7 sample groups that match closely to the faunal zones of Bermudez (Fig. 4.12). A plot of the value of the semi-partial R-squared for each cluster (Fig. 4.13) begins to level off at about 0.03, above which level the clusters become less significant. Cluster 1 includes all of the samples from the Sombrerito Formation and two samples from the Trinchera Formation (RD-59 and 117). The two Trinchera samples, which are Bolivina-rich types with reduced diversity, reflect a phenomena common in Sombrerito samples which we interpret to reflect low oxygen conditions. Cluster 2 is composed of samples from the lower part of the Trinchera Formation, as well as the stratigraphically highest sample of the Gajo Largo Member of the Sombrerito Formation. These samples lie in the stratigraphic range of the type locality of Bermudez's Basal Trinchera zone, located at La Trinchera (Fig. 4.2). The assemblage includes Eggerella propinqua. Recurvoides trincherasensis. and Ammodisus dominicensis. three species listed by Bermudez (1949) as distinctive in this zone. Cluster 3 compares closely to the Gaspar Zone. It is comprised by samples from the middle part of the Trinchera Formation, equivalent to the type strata that crop out in Arroyo Gaspar. Bermudez's marker species for this zone, such as Uvigerina carapitana. Valvulineria gasparensis. Bolivina furcata. and Uvigerina peregrin a. are present in nearly all of the samples of Cluster 3. The Bao Zone of Bermudez was defined on faunas that span the Trinchera-Quita Coraza boundary in the seaward part of our study area, specifically Arroyo del Bao and Rfo V ia. Its lower occurences are in sand- and conglomerate-rich turbidite strata of the upper Trinchera, and its more fossiliferous higher occurences lie in the lower part of the mudstone interval that is now defined as the Quita Coraza Formation. Clusters 4 and 5 are composed of strata from the upper Trinchera-lower Quita Coraza interval. Cluster 4 is

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semi-partial R-squared

DM2-1 (S) RD139 (S) DM2-8 (S) DM6-1 (S) RD113 (S) RD59 (T) RD115 (S) RD117 (T) RD125 (S) RD114 (S) AW1 (T) FL2 (T) RD7 (T) RD64 (T) RD12 (T) FL1 (T) DM3-2 (S) DMR17 (T) RD33 (T) RD66 (T) RD70 g> RD9 g) RD13 g) DM1-1 g) DM 10-2 (T) DM 10-1 (T) RD14 g) RD19 (Q) RD16 g> RD21 (Q) DM13-1 (Q) RD22 (Q) RD38 g ) RD46 (Q) DM11-2 (Q) RD79 (Q) DM1-4 (A) RD119 g> RD42 g) RD76 g ) RD36 g) RD74 g) DM 12-1 (T) TAB5 g) TAB1 (Q) RD49 (A) DM 13-8 (A) DM5-1 (A) RD84 (Q) DM13-3 (Q) RD101 (A) DM5-11 (A) DM13-4 (Q) HW3 (Q)

Figure 4.12 - Dendrogram resulting from a Q-mode cluster analysis using Ward's Minimum Variance method. Seven clusters are used for our interpretations; this number was chosen on the basis of the scree plot in Figure 5.13. Sample indications: S=Sombrerito, T=Trinchera, Q=Quita Coraza, and A=Arroyo Blanco.

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0.15 i

■o « » 0.10 ccI

_o r break point - a 0.05 7 clusters o . I E c«

0 10 2 0 30 4 0 50 60 # of clusters

Figure 4.13 - Plot of the number of clusters against semi-partial R-squared from our cluster analysis. A break in the slope is evident at approximately cluster 7, indicating that little variance would be accounted for by further clusters.

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dominated by samples from the Quita Coraza Formation; it also includes 3 Trinchera samples (RD14, RD16, RD38) with notable proportions of transported fauna, as well as one sample from lower Arroyo Blanco strata (DM1-4). Cluster 5 groups together 7 upper Trinchera samples and one sample from lower Quita Coraza strata (TAB1). It represents deposition in deeper water than Cluster 4.

Cluster 6 is made up of 3 samples from the basal part of the Arroyo Blanco Formation (RD49, DM5-1, DM13-8). All 3 of these samples have a strong influence of inner neritic species, most notably Havnesina depressula. Cluster 7 groups together 4 samples from the Quita Coraza Formation and 2 from the Arroyo Blanco. These can be referred to the Quita Coraza zone and are restricted to the seaward end of our study area. The fauna in those samples is typically inner to middle neritic. Many of the samples contain Angulogerina guraboensis. Bermudez (1949) reported A. azuana as characteristic of both the Quita Coraza Zone and the Higuerito member of the Arroyo Blanco; however, all specimens found by us from the type area of A. azuana appear to be closer to A. guraboensis. Overall, then, our cluster analysis demonstrates that the faunal zones defined by Bermudez (1949) form distinct, recognizable groups in the Azua Basin. Within these groups, samples from seaward of the basin appear to be younger than those in the northwest arm. Their environmental and biostratigraphic associations are summed up as follows:

1. The Sombrerito samples in Cluster 1 contain a lower to middle bathyal fauna and range from the uppermost lower Miocene to lowermost upper Miocene. 2. The Basal Trinchera Fauna (Cluster 2) represents a middle bathyal assemblage and range from uppermost middle Miocene to lowermost Pliocene.

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3. The stratigraphically higher Gaspar fauna (Cluster 3) reflects deposition near the boundary of the middle bathyal and upper bathyal zones and ranges from upper Miocene to lower Pliocene. 4. The lower Pliocene Bao zone spans the Trinchera-Quita Coraza formational boundary and is placed in the lower Pliocene. An upper Trinchera subgroup (Cluster 5) may be distinguished from a Quita Coraza Formation/ Rfo Via subgroup (Cluster 4), the former containing a fauna with bathyal-neritic boundary zone species and the latter with the added influence of typically middle to outer neritic species ( see principal components analysis, previous section). 5. The Quita Coraza zone (Cluster 7) also includes lower Pliocene strata, with faunas representative of inner to middle neritic environments.

6. The Arroyo Blanco samples in Cluster 6 are from inner neritic sedimentary rocks and restricted to the lower Pliocene of the seaward end of the Azua Basin.

Considering the usefulness of the "Hispaniola Fauna" as reference material for deep- water Neogene foraminifera, special caution needs to be exercised in using references to Bermudez's assemblages. Bermddez applied his Trinchera faunal zone terminology to samples collected to the west in the Las Matas-Elias Pina/Comendador area and to the east in the San Cristobal area. The Comendador area lies in a northwestern extension of the Azua Basin west of San Juan but has undergone a notably different geologic history. Most of the marine strata are lower and middle Miocene, lain down before the late Miocene onset of rapid uplift and resultant erosion of the Cordillera Central. We favor the use of the stratigraphic nomenclature of the Central Plateau of Haiti to describe the sedimentary succession, which is much finer grained than that of the Azua Basin. The San Cristobal area also has a different geologic history including a Neogene folding event, erosion and subsequent unconformable deposition (Huebeck and Mann, MS) in a lower to middle

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Miocene sequence. An assumption that data derived from these areas apply to the Azua Basin, or vice versa, may lead to misinterpretations. In some cases, Bermudez associated species with certain faunal zones based only on occurences in the Comendador or San Cristobal areas and not in the type areas in the Azua Basin. In the case of Cibicicoides matanzasensis (Hadley), Bermudez refers to the locality of his plesiotypes as the Gaspar zone of the Yaquate area, near San Cristobal. Although this species has not been noted above the middle Miocene zone (N12), subsequent references to his specimens (e.g. van Morkhoven et al, 1986) report its occurence in the Trinchera Formation, a unit that does not extend below the uppermost part of the middle Miocene.

GEOLOGIC IMPLICATIONS

As pointed out in the previous section, the Azua Basin sequence exhibits a steady vertical transition from lower or middle bathyal environments to a nearshore setting. Considered within the context of the biostratigraphic framework of the Azua Basin, the benthic foraminiferal assemblages also to show a geographic trend of seaward deepening. This is reflected in the factor scores of the samples if several "time frames" are examined. In the base of the upper Miocene part of the section, for example, the scores on Factor 1 tend to be more strongly negative in the Fondo Negro area (~-l) than in the northwest

(~-.6) , indicating a better development of the lower to middle bathyal fauna in the south. In the uppermost Miocene of the northwest, Factor 2 scores are strongly positive, indicating the importance of middle to upper bathyal species there; in contrast, equivalent samples from near the Miocene-Pliocene boundary in the Fondo Negro area have distinctly negative scores on Factor 1, indicating a notable lower to middle bathyal assemblage. Within any cluster of related samples, this same trend is reflected as a younging of cluster members towards the more seaward parts of the basin.

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Paleoenvironmental trends parallel areal lithostratigraphic variations (Chapter 2; McLaughlin and Bold, MS) in the Azua Basin and indicate Caribbean-ward progradation of a coastal delta-submarine turbidite fan complex during the Miocene and Pliocene. Environmental migration began sometime near the close of the middle Miocene as the Azua Basin began to fill with large volumes of siliclastic sediments. The basin filling appears to reflect denudation of the rapidly uplifted remnant Mesozoic to Eocene island arc complex that forms the core of the Cordillera Central. Uplift of the Sierra de Neiba appears to have begun simultaneously, resulting in the evolution of the Azua Basin as a ramp valley with anticlimal thrust blocks bounding a synclinal sedimentary trough. Mann et al. (1984) have suggested that Hispaniola is a " restraining bend" in the Northern Caribbean Plate Boundary Zone (NCPB2), with pervasive oblique compression ("transpression") resulting from the interaction of east-west left-lateral strike-slip on older, northwest -trending island- arc structures. Our findings are compatible with this idea; furthermore, we suggest that our foraminiferal evidence helps constrain the timing of restraining bend initiation to the end of the middle Miocene.

REGIONAL COMPARISONS

The faunas of the Azua Basin Neogene sedimentary sequence show strong relationships to a number of others in the Caribbean region (Table 4.2).However, several considerations are important in the comparison of assemblages reported in different studies:

1) stratigraphy - we focus primarily on studies for which the regional stratigraphy was sufficiently known; in cases where the stratigraphy was misunderstood, misleading impressions of the significance of the faunas has resulted.

2 ) taxonomy - especially in the case of older studies, it may not be certain that we are using the same name to describe the same species as those to which we make

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Ammodfscusdetomite Ammonia parklreonlana Amphteteolna ofobosa Anaukxwrtna anot/tosa A. carinata v. bradvana exlmla . tamateens/s A. occklentalls seteovenste Anom alfna flfmll Astertoerina carinata Bermudezlnella rlverol Boltvlna alata B. albatross! B. aria B. bvram ensis B. furcala B.ooessl Inflata B. lowmanl B. marolnata v. multlcostata B. minima

B. plBcHormls B. olfcatella v- mera a o v a m a s a B. teciiformlB B. so. T fas B. tectlformla) Bullmina alazanertsle B. mexlcana B. so d alls B. tessellata Bullmlrwlta eteoanttsslma Cancrts saora Casskiulna crassa C. curvata C. carinata / ♦laevigata C. norcmssl var. australis C. reflexa C.subotobosa CassJdullnoWes brady) rftffliobullmlna alazanartsls Chllostomella czizekl ClblckJea dcatricosus C. tobatulus wuellerstorfl Ctolddoldes Incrassatus

C. pachvderma f. bathyalls chvderma f. subllttorallfl erforatus AF AG AF At AJ AQ AF AS AT AV AWAX AY AZ C o lo m b ia Panama M e x ic o Clbao C. Haiti Cuba road v e n e z . 186 X X 4 X 4 X X X X AZ XX X XX XX X X X X X X X XXX X XX XX X X 4 X XXX Mexico AX AY X XX 4 4 X w 4 XX XX 4 X X X X XX 4 4 X 4 X XX AU AV X 4 X X 4 XXX X 4 X XXX 7 X XXX 4 AF AS AT Panama C. Rica X 4 X X X XX X 4 X 4 4 XX 4 XX AF AO Ec X X AO X Mi X 4 7 7 X X X X AK AL AIM X X X 4 X AJ XX X 4 X AFAl X X X Colombia X X 4 7 X 4 4 X AFAG 7 4 AE 4 4 XX 4 AC AC 4 AB AA 4 XXXXX z X X X Venez. 4 X 4 X X X X X XXXX X X X 4 X XY Ar X XX X w X X XXX X X r d a d X XX X X X X X XXXXXXXXX X XX 4 4 v t X XXXXXXX X X X X XXX X X XXXXX 4 XXXX Jam . s T u V XX R 4 XXX X XX Q X 4 4 4 XX 4 XXX p XXX X 4 4 XXXX X XXX X XXX X XXX o X X 4 X X 4 X XX X 4 4 XXXX 4 XX 4 X X X Cuba 4 MN 4 X X L X 4 4 XXXX 4 4 X XX X X X X JK XX 4 X X X X I X X H X X X X X XXXXX X XX G X XX X XX X XX X XX X F 4 E C. C. Haiti Bani X X X X X XXX X 4 XI XX 4 >p XX XX X X X X 7 4 X X X X X X X XX XXXX 4 XX X X X X X X X X X X X 7 7 XXX XXX X B c 0 4 XX X XX X Clbao X X 7 7 4 4 X X X X XX XX XX X X X X A T 4 C. robertsonlanus/bradvl Ctavullna mexlcana Derttalina communis Eaaerrella bradvl C. slntstralis Ehrenberoina soirrasissima Eplstomlnella ad/ena Elphidlum lanleri E.DOevanum F. Dontonl Eexloua Fursenkolna comoressa Gvroidlna altlformlB Globobullmlna Dacltlca G. altlsplra G. alrardana G. laevls G. reaularl8 G. trinchorasertslsZ+soldanll Martlnotlella nodulosa Havneslna deoressula Hoeafurtfnaeleaans Karreriella bradvl M. M. pompllloldes Planulfna ariminensls latlcarfnlna oauperata G.umbonaia Mefonfs afffnls Nonion so. dorsalis Ori umbonatus Planutlna renzl P. oratetouDi Pleurostomella afternansPseudononion atlantfcum P. sallsburvl Osanaularta cutter Puffenta bulJoktefi Pvrao murrhlna P. subcarinaia RectobolMna mexlcana Recurvofdes trincberasenslsReussella 6o(nuto&a Qulnoueloculina semlnullna Rosallna Horidana Saorina pulchella Slgmollina tenuis S. tenuicarlnata/bradvana S. pulchra Stamavlraullna tortuosa Siamollopsls schlumberaerl Slohoninapozonensis

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission 187 X X 4 4 XX X XX AY AZ 4 X X X AX X X AH X X XX AU AV XX X X XXXXX XX X XXXX 4 4 X Ec Panama C. Rica Mexico AF AO AR AS AT X X XX X AO Aft Aft 1 4 4 4X 4 AL AK X X AF A l A J X AG 1 X X AF X X X X 4 4 AA AE AC AC AE X z X XX XX V 4 X X 4 4 ArVenez. Colombia X w X X XXX XXX V Td ad X X XXX u VI X X T XXXX s ♦ X X X X X XXX XXXX XXXXX XX X p Q R X X X 0 XX XX X X XXX 4 4 N C u b a Jam , M L JK 1 B a n l X XX X XX GH X X X F E C. H aiti X XX X X D pp XX XX XXX X XX circum-Caribbean sequences. X=recorded occurrence, +=occurrence of similar form a form or ofsimilar +=occurrence occurrence, X=recorded sequences. circum-Caribbean A=Mao Fm., B=Gurabo Fm., C=Cercado Fm.; D=Port-au-Prince beds, Haiti; E=Las Fm., I=lower Banf Fm., Miocene strata, strata; area J=Matanzas L=Canimar K=LaCruz X form suspected to be die same. The names of the host strata for the data columns are: are: columns data the for strata host the of names The same. die be to suspected form Table 4.2 - Regional comparison of occurrences of selected Azua Basin species in Basin other species Azua of selected of occurrences Table 4.2 comparison - Regional Cahobas Fm., F=Thomonde Fm., Joie G=Madame Fm.; H=middle Miocene Ban! area X X R=Tinguaro Fm; S=Bowden Fm., T=Buff Bay beds, Jamaica; zone U= becarij Jealousy AB=R. Gp.; Fm. Blanco AA=Cabo and Fm., Z=Carapita Gp., Salada Y=Agua Aruba; Fm., Fm., M=Guines Fm., N=Cojimar Fm., 0=Nipe Series, P=Maquay Fm., Q=Jaruco Fm, of X=Miocene Trinidad; Croix W=St. Fm., part Fm., lower V=Cipero Fm.; ofKingshill c of the Carmen-Zembrano area, northern Colombia, AC=U. subpereerina zone. AD=B. carmenensis zone, zone, dissimilis AG=G. tenuis basispinata zone, zone, AE=S. AF=S. Piojo the of strata AK=upper Fm., AJ=Tubara AI=ChoneraFm., zone; perlucidus AH=C. of Manta area, Ecuador; AQ=Gatun Fm., AR=Culebra Fm., AS=Aquaqua & Arruza Fms., Fms., Arruza & AS=Aquaqua Fm., AR=Culebra Fm., AQ=Gatun Ecuador; area, Manta of AN=Hibacharro-Gallinazo Fm., AO=Miocene of Goajira Peninsula; AP=middle Miocene Miocene AP=middle Peninsula; Goajira of AO=Miocene Fm., AN=Hibacharro-Gallinazo AT=Caimito Fm.; AU=Moin Fm., AV=Rio Banano Fm., AW=Uscari Fm; AX=upper Concepcion biozone of the Salinas Basin, AY=lower Concepcion biozone, AZ=Encanto AZ=Encanto biozone, Concepcion the ofBasin, AY=lower biozone Salinas Concepcion biozone. / Saco Fms., AL=lower strata of the Piojo / Saco Fms., AM=Perdices Fm., X X B C ib a o XX XX XX XX A martaereJs Sohaerddlna bultoides X X Stalnforthla conmfanataSlcbonodosaria nuttalli S. nuttalli v. S. araclllfma paucfstriata X X Trifarlna bradvl IMaerina auberfana S. leoJdula S. verneulll U. caraoliana U. hfeokJaU. hteokJocostata X X X U. U. oarvula U. perearina U. Dtamaea Valvullneria mexlcana X X

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comparisons; where possible, comparisons have been made with illustrations, but caution must be used in comparison to studies with poor illustrations or none at all. An attempt has been made to characterize the reliablity of the comparisons made in this study based on these considerations. In Table 4.2, reliable species occurrences are denoted by "X" whereas occurrences which are suspected to be the same species or a similar form are marked with "+". Very reliable comparisons may be made between the Azua Basin faunas and those of Haiti, Jamaica, St. Croix, and other parts of the Dominican Republic. In the northwestern continuation of the Azua Basin into Haiti, a similar but less coarsely clastic sequence is present. Examination of foraminiferal faunas collected during the senior author’s field studies in the Elias Pina /Comendador area of the western Dominican Republic, as well as those reported in the Plateau Central of Haiti (Hunerman, 1972), suggests a similar faunal succession to the Azua Basin. The faunas of the Madame Joie Formation (lower Miocene) and Sombrerito Formation are nearly identical, lower to middle bathyal types; middle to upper bathyal assemblages of the lower part of Thomonde Formation (middle Miocene) are comparable to those of the the Trinchera, and outer neritic assemblages in the upper part of the Thomonde to the Quita Coraza. Lower Miocene carbonate-rich strata on the north side of the basin contain rich, shallow-marine and reefal assemblages; these strata are referrable to the Arc Formation. The Haitian-Comendador material, however is older than the Azua Basin material and differs in the presence of some deep water species that appear to have become extinct before deposition of the Trinchera and most of the Sombrerito (i.e. Cibicidoides matanzasensis. Siphogenerina transversa. S. senni: see van Morkhoven et al., 1986). To the east of the Azua Basin, in the Banf-San Cristobal area, the senior author has found the lower and middle Miocene strata to include many of the same deep-water foraminiferal species present in the Sombrerito Formation and lower part of the Trinchera

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Formation. Higher, in the middle Miocene, outer neritic deposits predominate, with some faunal similarities to the Quita Coraza Formation. The faunas of the Cibao Basin, northern Dominican Republic were reported in Bermudez (1949) and resemble those of the upper portion of the Azua Basin sequence. However, the Cibao faunas reflect a different paleoenvironmental succession, with deepening upward through most of the sequence followed by shoaling near the top. The Cercado Formation (upper Miocene; Saunders et al., 1986) and upper part of the Mao Formation (lower-middle Pliocene) appear to be predominantly neritic strata and contain a number of forms in common with the Quita Coraza Formation. The Gurabo Formation (upper Miocene-lower Pliocene) includes many of the same forms as the other two units as well as deeper water species (U. carapitana. Cibicidoides bradvil: overall, it is comparable with the upper part of the Trinchera Formation. Coryell and Rivero (1941) reported a rich deep water fauna from the "Port-au-Prince beds" of southern Haiti which is nearly identical to that of coeval Trinchera deposits to the east. Although these strata were referred to as Miocene, they are probably referrable to the Rivibre Grise Formation, which is known to be Pliocene (van den Berghe, 1985; Andreieff et al., 1987). Neogene foraminiferal faunas reported from Jamaica shows similarities to some of the Azua Basin faunas. Cushman and Todd (1945) and Cushman and Jarvis (1930) reported middle to upper bathyal species (and shallow-marine contaminants) in the Buff Bay deposits (upper Miocene-lower Pliocene), with many species common to the middle and upper parts of the Trinchera Formation. The foraminifera of the Bowden Formation (lower to upper Pliocene) were reported by D.K.Palmer (1945) and Cushman (1919). The assemblage appears to reflect a setting near the neritic-upper bathyal boundary and is comparable to that of our uppermost Trinchera and lowermost Quita Coraza samples.

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The senior author, along with I. Gill (Tulane University), has studied the benthic foraminifera from a number of test well cores of the Jealousy and Kingshill Formations (lower to middle Miocene) of St. Croix; ditch samples from 3 wells that penetrated these strata were also studied by Cushman (1946). The lower Kingshill and the Jealousy assemblages are nearly indistinguishable from each other, and are nearly identical to those in some of our Sombrerito samples. All contain rich assemblages of deep water species with relatively high abundances of Bolivina common. Good comparisons may also be made to faunas described fron Trinidad, Aruba, Venezuela, Colombia, Costa Rica, and Mexico. In Trinidad, the lower and middle Miocene benthic foraminifera in "Zones II and III" of the Cipero Marl (Cushman and Stainforth, 1945) comprise a middle bathyal or deeper assemblage, similar to Sombrerito assemblages or to those in the lower part of the Trinchera Formation. Cushman and Renz (1941) report a foraminiferal fauna from the middle Miocene strata referred to as the "St. Croix Formation"; in fact, these strata represent apart of the Cipero Formation that includes large oliststromes. Many species reported are present in the Trinchera Formation, but they also note older species of Siphogenerina fS. transversa. S. basispinata’) whose ranges appear to end before the Trinchera. Drooger (1953) reported a fauna comparable to that of the upper Trinchera from the subsurface of Aruba (lower Pliocene). Neogene benthic foraminifera of Venezuela have been reported by Bermtidez and Fuenmayor (1962) for the Cabo Blanco Group near Caracas, by Hedberg (1937) for the Carapita Formation of northeast Venezuela, and by Renz (1948) for the Agua Salada Group of northwest Venezuela. The Playa Grande and Mare Formations (Pleistocene) of the Cabo Blanco Group contain predominantly neritic species, with some nearshore forms, in an assemblage very similar to that of the Quita Coraza Formation. The fauna of the Carapita Formation (Miocene) appears to resemble that of the Trinchera in the Azua Basin; Hedberg

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(1937) estimated depths of over 300m. in the upper part of the formation in the Agua Salada Group. In the Agua Salada Group, the Tocuyo (San Lorenzo) Formation and the lower part of the Pozon Formation (middle Miocene) contain rich, middle to upper bathyal benthic foraminiferal faunas which are comparable to those of the Trinchera Formation. Although they are significantly older than the Azua Basin faunas, lower Miocene foraminifera reported from the Sillamana and Uipra areas of the Goajira Peninsula, northeast Colombia (Becker and Dusenbury, 1958), are similar to the upper bathyal assemblages of the upper part of the Trinchera Formation. The foraminifera of the Magdalena Basin of northern Columbia were reported in Bordine (1974) and Redmond (1953). The middle Miocene Hibacharo-Gallinazo Formation and Perdices Formation faunas are dominated by deep bathyal faunas comparable to the lower part of the Trinchera or the Sombrerito. Higher in the section, the Piojo and Saco Formations show a transition from late Miocene, upper bathyal faunas to Pliocene, neritic to marginal-marine faunas; a similar faunal transition, including many of the same species, is evident between the upper part of the Trinchera and the upper part of the Quita Coraza. An inner shelf fauna, very similar to the upper part of the Quita Coraza, characterizes the Pliocene Tubara Formation. The highest marine unit, the Chorrea Formation (Pliocene) includes middle shelf to marginal marine faunas comparable to those of the upper part of the Quita Coraza and the lower part of the Arroyo Blano. Petteis and Sarmiento (1956) established 7 foraminiferal zones in the Carmen-Zembrano area (upper Oligocene-upper Miocene?) of northern Columbia ranging from upper Oligocene to the upper Miocene. From the top of the lowest zone fCibicides perlucidus zone) through the next 3 zones (Globigerina dissimilis. Siphogerina basispinata. Sigmolina tenuis’), a shift in foraminiferal assemblages is evident that closely parallels that from the Sombrerito through the Trinchera. The next 2 overlying zones fBolivina carmenensis and Uvigerina subperegrina zones) contain faunas typical of the Trinchera-Quita Coraza boundary and the Quita Coraza, respectively. The uppermost

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zone r'Rotalia becarii’’1 has poorer faunas, but the species present are the same as or similar to upper Quita Coraza and Arroyo Blanco constituents. Cassell (1986), Cassell and Sen Gupta (1989) and Taylor (1975) investigated the foraminifera of the Uscari, Rio Banano, and Moin Formations on the Caribbean side of Costa Rica. The Uscari (lower to lower middle Miocene) displays a transition of assemblages similar to that of the Trinchera Formation; these range from middle bathyal in the lower part to outer neritic-upper bathyal in the upper. The Rio Banano Formation (upper Miocene to middle Pliocene), the assemblages change upward from predominantly nearshore and reefal types to more open marine, inner to middle neritic types; these bear some similarity to some of the higher Quita Coraza assemblages. The Moin Formation (upper Pleistocene) is dominated by middle to outer shelf faunas comparable to the middle and upper Quita Coraza assemblages. Kohl (1985) subdivided the Pliocene of the Salinas Basin of southeastern Mexico into three foraminiferal zones. The lowest, called the Encanto Biozone, contains a middle to upper bathyal fauna with strong similarities to that in the Trinchera Formation. The middle zone, called the lower Conception Biozone, contains an outer neritic fauna with many species typical of the Trinchera - Quita Coraza transition. The fauna of the upper zone, the upper Concepcion, is closely related to the middle to outer neritic Quita Coraza fauna in the Azua Basin. Less reliable comparisons may be made to faunas described from Cuba, Ecuador, and Panama. Although several extensive studies of Tertiary smaller foraminifera have been done in Cuba, most of these were in the 1930’s and 1940’s. Since that time, and especially since the Cuban revolution, much more extensive stratigraphic work has been done and has revealed in some cases that the older confused stratigraphy resulted in the lumping together of faunas from separate horizons (Bold, oral comm., 1989). In western Cuba, the lower Miocene Tinguaro Formation (=Finca Adelina Marls, Palmer and Bermudez, 1936b)

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contains a middle to upper bathyal fauna with strong similarities to the Trinchera Formation. Bermudez (1950) correlated the lower to middle Miocene deposits of the Jaruco Formation to the Sombrerito Formation; his species list includes many forms in common with the Sombrerito and the lower part of the Trinchera. The Cojimar Formation (middle Miocene) fauna reported by Palmer (1940a, b; 1941a, b) is suggestive of the neritic-bathyal zone transition. Bermudez (1950) suggested that it is the equivalent of the Trinchera, consistent with our findings of many common species between the Cojimar and the upper Trinchera / lower Quita Coraza faunas. The Giiines Formation (upper Miocene) is a good example of stratigraphically-mixed faunas that have been described in areas of confused stratigraphy; Bermudez (1950) also included material from the lower Miocene Arabos Member (Bold, written comm., 1989). These are miliolid- and peneroplid-rich shallow marine strata which do not compare closely to any Azua Basin material. Overlying the Giiines is the Canimar Formation (uppermost Miocene or lower Pliocene), which includes a middle to outer neritic assemblage similar to that of the middle part of the Quita Coraza Formation. A rich, "deep water" fauna is reported from the Matanzas Formation (upper Pliocene-Pleistocene?) by Palmer and Bermudez (1936a). The species repotted in this unit are, in large part, typical of the Quita Coraza Formation. Li the Miocene Maquey Formation of southern Oriente Province, Keijzer (1945) reported typically upper bathyal species that are also found in the upper Trinchera. From the Nipe area, further north in Oriente Province, the Nipe series (middle Miocene) yields a rich, middle to upper bathyal foraminiferal assemblage typical of our findings in the Trinchera formation. The LaCruz Formation (Mio-Pliocene ?) faunas (Keijzer, 1945) represent coastal facies (Bermudez, 1950) but include many miliolids, peneroplids and larger reef-type foraminifera, unlike the coastal deposits of the Azua Basin. Galloway and Money (1929) reported a deep bathyal assemblage of foraminifera from the Pacific coastal region near Manta, Ecuador in middle Miocene strata. The

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assemblage shares many species in common with the Sombreritio and the lower part of the Trinchera, including Bolivina pisciformis. first described in the Manta study. This barb- edged species is present throughout the deep water strata of the Azua Basin, wheras the more typical Gulf of Mexico - Caribbean form B. barbata is absent. The study of Cushman (1918) from the Canal Zone of Panama may be cautiously compared to the Azua Basin. The strata referred to the Culebra Formation (lower Miocene) reported by Cushman (1918) shares some species with the upper part of the Trinchera; species reported from strata placed in the Gatun Formation (upper Miocene) are similar to or the same as some typical Quita Coraza forms. Teny (1956) reported the foraminifera from several of the Neogene Formations of the Caribbean coast of western Panama. Faunas from the Aquaqua (upper Miocene), Aruza ( upper Miocene) and Caimito (middle Miocene; refered to as Uscari) Formations appear to reflect deposition in middle to upper bathyal settings and share a number of species with the Trinchera Formation. From this comparison, it is evident that the deep-marine assemblages of the Sombrerito and Trinchera Formations share many species with diverse assemblages of the Antilles and Central America. These comprise some of the finest reference material for the Neogene of the Caribbean region; the environmental interpretations of species associations in the Azua Basin should be useful in paleoenvironmental studies of other Neogene marine sequences of the Caribbean region.The shallow-marine Neogene faunas of the Azua Basin are distinctly different than most others of the circum-Caribbean region. They are generally poorer in miliolids and peneroplids, reflecting the dominance of clastic versus carbonate sedimentation. Overall, the Caribbean region middle Miocene and younger benthic foraminiferal faunas have a very modem aspect. Upper Oligocene to lower middle Miocene faunas include a greater proportion of extinct species that give the fauna an older character, but nevertheless contain a surprisingly large number of extant forms.

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CONCLUSIONS

Numerical analysis of species abundances in the Neogene of the Azua Basin reveal three significant faunal characters: upward shoaling; Caribbean-ward deepening and time- transgression; and faunal zonation.

We have interpreted 6 factors based on a Principal Components Analysis. The shifts of the scores of these factors upsection reflects steady shoaling between the lower Miocene and middle Pliocene. Negative scores on Factor 1 in the Sombrerito Formation and the lower part of the Trinchera Formation reflect the dominance of lower to middle bathyal assemblages that include Cibicides wuellerstorfi. Pleurostomella altemans. and Bolivina paula. From the middle to the upper parts of the Trinchera, a shift from middle to upper bathyal assemblages (Factor 2) to shelf-edge assemblages (Factor 1) is evident; this reflects a change from a Recurvoides trincherasensis-Oridorsalis umbonatus-Hoeglundina elegans- Sigmoilopsis schlumbergeri association to one characterized by Bolivina minima. Cassidulina norcrossi var. australis, and Gvroidina regularis. The dominance of shallow- marine assemblages in the Quita Coraza and Arroyo Blanco Formations is reflected in the scores of Factors 3,4, and 5. Factor 3 includes typically middle to outer neritic species (Angulogerina iamaicensis. Cassidulina subglobosa. Cassidulina carinata. Reussella spinulosa! and scores strongly in the Quita Coraza Formation. Factor 4 is dominated by inner neritic species such as Havnesina depressula. Buliminella elegantissima. and Rosalina concinna and is most important in the Arroyo Blanco Formation. Factor 5, which scores heavily in the higher Arroyo Blanco strata, is interpreted as a neritic assemblage and is characterized by Cancris sagra. Bolivina lowmani. and Gavelinopsis sp. A. Factor scores in the sections indicate, in any one time plane, the occurence of deeper water faunas seaward of the northwestern end of the basin. This Caribbean-ward

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deepening is corroborated by a time-transgression of paleoenvironments, with a trend toward assemblages of similar environmental signifigance becoming younger toward the coastal region. Our cluster analysis resolves sample groups that correspond almost directly to the faunal zones of Bermudez (1949). The seven sample groups recognized are: Sombrerito Formation; Basal Trinchera Zone; Gaspar Zone; lower part of the Bao Zone; upper part of the Bao Zone; Quita Coraza Zone; and Arroyo Blanco Formation. The shoaling evident in the Azua Basin reflects the onset of rapid siliclastic sedimentation near the start of the late Miocene. The time transgression migration of faunal assemblages towards the Caribbean parallels that of the lithofacies. These suggest that uplift of the Sierra de Neiba and Cordillera Central began near the end of the middle Miocene, with deposition in the Azua Basin proceeding in the style of a fault-block bounded, synclinal ramp valley. The Azua Basin faunas span a wide range of environments and comprise some of the best reference material for Caribbean foraminifera. Our survey of a number of other circum-Caribbean Neogene assemblages demonstrate close relationships to those identified in our study and suggest that the Azua Basin fauna may serve as a useful reference material in future paleoenvironmental investigations.

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Cushman, J.A., and Renz, H.H., 1941. New Oligocene - Miocene foraminifera from Venezuela. Contributions from the Cushman Laboratory for Foraminiferal Research, v. 17, no. 1, p. 1-27, Pis. 1-8.

Cushman, J.A., and Stainforth, R.M., 1945, The Foraminifera of the Cipero Marl Formation of Trinidad, British West Indies: Cushman Laboratory for Foraminifera Research, Special Publication 14, p. 3-75, pis. 1-16.

Cushman, J.A., and Todd, R., 1945, Miocene foraminifera from Buff Bay Jamaica: Cushman Laboratory for Foraminiferal Research, Special Publication No. 15,73 pp., 12 pis..

Davis, J.A., 1973, Statistics and data analysis in geology: John Wiley and Sons, New York, 656 p.

Door, J.B., 1933, New data on the correlation of the Lower Oligocene of South and Central America with that of southern Mexico: Journal of Paleontology, v. 7, p. 432-

438.

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Doreen, J.M., 1979. A recorrelation of Miocene formations in the Dominican Republic: Journal of Petroleum Geology, v. 2, p. 47-53.

Drooger, C.W., 1953. Miocene and Pleistocene foraminifera from Oranjestad, Aruba (Netherland Antilles). Contributions from the Cushman Foundation for Foraminiferal Research, v. 4, no. 4, p. 116-147, tab. 1, chart, pis. 19-24.

Galloway, J.J., and Heminway, C.E., 1941. The Tertiary foraminifera of Porto Rico, in Sclaikjer, E.M., ed., Scientific Survey of Puerto Rico and the Virgin Islands, v. 3, no. 4, p. 275-491, tabs. 1-4, pis. 1-36. The New York Academy of Sciences, New York.

Galloway, J.J., and Morrey, M., 1929. A lower Tertiary foraminiferal fauna from Manta, Ecuador. Bulletins of American Paleontology, v. 15, no. 55, p. 7-56, Pis., 1-6.

Gibson, T.G., and Buzas, M.A., 1972, Species diversity - patterns in modem and Miocene foraminifera of the eastern margin of North America: Geological Society of America Bulletin, v. 84, p. 217-238.

Haq, B.U., Hardenbol, J., and Vail, P.R., 1987. Chronology of fluctuating sea levels since the Triassic: Science, v. 235, p. 1156-1167.

Hazel, J.E., 1977. Use of certain mutivariate and other techniques in assemblage zonal biostratigraphy - examples utilizing Cambrian, Cretaceous, and Tertiary benthic invertebrates in Kaufman, E., and Hazel, J.E., eds., Concepts and methods in biostratigraphy: Hutchinson Ross Publishing Company, Stroudsburg, PA, p. 187-212.

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Hedberg, H.D., 1937. Foraminifera of the middle Tertiary Carapita Formation of northeastern Venezuela. Journal of Paleontology, v. 11, no. 8, p. 661-697, Fig. 5.1, tabs. 1, 2, pis. 90-92.

Hunerman, A., 1972, Middle Tertiary biostratigraphy of the Central Plateau of Haiti: Unpublished M.S. thesis, Louisiana State University - Baton Rouge.

Keijzer, F.G., 1945. Outline of the geology of theeastem part of the province of Oriente, Cuba (E of 76° W longitiude), with notes on the geology of other paits of the island. Utrecht University, Geographische en Geologische Mededeelingen, Physiographisc- Geologische, ser. 2, no. 6, 334 pp., 11 pis., 1 map, 19 tabs..

Kohl, B, 1985. Early Pliocene benthic foraminifers from the Salina Basin, southeastern Mexico. Bulletins of American Paleontolgy, v. 88, no. 322, p. 5-173, text-figs. 1-18, tab. 1, pis. 1-37.

Lankford, R.R., 1959, Distribution and ecology of foraminifera from the east Mississippi delta margin: Bulletin, American Association of Petroleum Geologists, v. 43, no. 9, p.

2068-2099.

Loeblich, A.R., and Tappan, H., 1988, Foraminiferal genera and their classification: Van Nostrand Reinhold, New York, v. 1, 970 p.

Mann, P., Burke, K., and Matumoto, T., 1984. Neotectonics of Hispaniola: plate motion, sedimentation, and seismicity at a restraining bend: Earth and Planetary Science Letters, v. 70, p. 311-324.

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McLaughlin, P.P., 1989. Neogene planktonic foraminiferal biostratigraphy of the southwestern Dominican Republic. Journal of Foraminiferal Research (in press).

McLaughlin, P.P., and Bold, W.A. van den, in review. Geology of the Enriquillo-Azua Basins, 2: Depositional History - Foraminiferal and Ostracode evidence in Mann, P., Draper, G., and Lewis, J., eds, Geologic and tectonic studies in Hispaniola: GSA Special Paper.

McLaughlin, P.P., and Sen Gupta, B.K., in preparation, Neogene benthic foraminifera from the Dominican Republic - Taxonomic problems: To be submitted to Journal of Paleontology.

McLaughlin, P.P., and Sen Gupta, B.K., in preparation, Neogene paleoenvironmental migration, southwestern Dominican Republic, and implications for Northern Caribbean Plate Boundary Zone Activity - Foraminiferal evidence: To be submitted to Geology.

McKee, W.H., 1985, Tertiary foraminifera of the Puntarenas Province, Costa Rica: Louisiana State University, Baton Rouge, M.S. Thesis, 280 p.

Murray, J.W., 1973, Distribution and ecology of living benthic foraminiferids: Heinemann Educational Books, London, 274 p.

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Nuttall, W.L.F., 1932. Lower Oligocene foraminifera from Mexico. Journal of Paleontology, v. 6, no. 1, p. 3-35, pis. 1-9.

Osiris de Leon, R., 1978. Aspectos geologicos e hidrogeologicos de la region suroeste. Museo National de Historia Natural (Republica Dominicana), Publicaciones Especiales, Numero 4, 25 pp.

Palmer, D.K., and Bermudez, P J., 1936a. Late Tertiary foraminifera from the Matanzas Bay region, Cuba. Sociedad Cubana de Historoia Natural, Memorias, La Habana, v. 9, no. 4, p. 237-258, pis. 20-22.

Palmer, D.K., and Bermudez, P.J., 1936b. An Oligocene foraminiferal fauna from Cuba. Sociedad Cubana de Historoia Natural, Memorias, La Habana, v. 10, p. 227-316, pis,. 13-20.

Palmer, D.K., 1940a, Foraminifera of the Upper Oligocene Cojimar Formation of Cuba; Part 2. Memoria de la Sociedad Cubana de Historoia Natural "Felipe Poey", v. 14, pt. 2, p. 113-132, pis. 17,18.

Palmer, D.K., 1940b, Foraminifera of the Upper Oligocene Cojimar Formation of Cuba; Part 3. Memoria de la Sociedad Cubana de Historoia Natural "Felipe Poey", v. 14, pt. 4, p. 277-303, pis. 51-53.

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Palmer, D.K., 1941a, Foraminifera of the Upper Oligocene Cojimar Formation of Cuba; Part 4. Memoria de la Sociedad Cubana de Historoia Natural "Felipe Poey", v. 15, pt. 2, p. 181-200, pis. 15-17.

Palmer, D.K., 1941b, Foraminifera of the Upper Oligocene Cojimar Formation of Cuba; Part 5. Memoria de la Sociedad Cubana de Historoia Natural "Felipe Poey", v. 15, pt. 3, p. 281-309, pis. 28-30.

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Phleger, F.B., 1951. Ecology of foraminifera, northwest Gulf of Mexico; Part 1 - Foraminifera distribution: Geological Society of America, Memoir 46, v.l, p. 1-88.

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tabs., 12 pis..

SAS Institute, Inc., 1985, SAS Users Guide - Statistics: Cary, N.C., 956 p.

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Sen Gupta, B.K., 1979, Foraminfera of the South Atlantic / Georgia Bight, in South Atlantic OCS Benchmark Program 1977 Report, Volume 3: Dallas, Texas, Texas Instruments Incorporated, p. 341-396.

Sen Gupta, B. K., and Schaefer, C.T., 1973. Holocene benthonic foraminifera in leeward bays of St. Lucia, West Indies: Micropaleontology, v. 19, p. 341-365.

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tabs. 1,2 , pis., 1-12.

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PLATE 4.1

1 . Clavulina mpxipanp. RD131. xlOO 2, 3. Recurvoides trinchpra$pnsi$. RD13. 2. dorsal view. 3. ventral view. x75 4. Eeeerella propinqug. RD129v. xlOO 5. Karreriella bradyi. RD 66v. xlOO 6. Sigmoilopsis schlumbergeri. RD74a. xl50 7. Hoeglundina plegans. RD 66v. xlOO 8 . Bolivina furcata. RD131. xlOO 9. Bolivina alata. RD74a. xl50 10. Bolivina marginata var. multicostata. RD125. xl50 11. Bolivina arta. RD119. xl50 12. Bolivina pisciformis. RD130. xl50 13. Bolivina plicatella var. mpra. RD59. xl50 14. Bolivina albatrossi. RD59. xl50 15. Bolivina minima. RD22. xl50 16. Bolivina paula. RD59. xl50 17. Bolivina sp. 0. RD59. xl50 18. Bolivina sp. A. RD59. xl50

PLATE 4.2

1. Bolivina obscuranta. RD131. x!50 2. Bolivina lowmani. RD59. xl50 3. Bolivina inflata. RD130. xl50 4. Bolivina? sp. K. RD101. x!50 5. Cassidulina curvata. RD131. side view. x200 6. Cassidulina carinata. RD130. side view. x200 7. Cassidulina notcrossi var. australis. RD79. side view. x200 8 . Cassidulina subglobosa, RD59v. side view. xl50 9. Bulimina alazanensis. RD131. xlOO 10. Bulimina mexicana. RD131. xlOO 11, 12. Bulimina tessellata. 11. RD74a, xl50; 12. RD36, xl50 13. Bulimina socialis. RD131. xlOO 14. Buliminella elegantissima. DM13-8. xl50 15, 16. Uvigerina carapitana. RD131.15. microspheric form, xlOO; 16. megalospheric form, xlOO 17. Uvigerina hispidocostata. RD13v. xlOO 18. Uvigerina hispida. RD9v. x!50

1, 2 . Uvigerina ppregrina. 1. RD70v, xlOO; 2. RD131, xl50 3. Uviserina azuana. RD76. xl50 4. Uvigerina viaen§is. RD131. xlOO 5. Uvigerina pigmaeg. RD16. xl50 6. Uvigerina parvpla. DM13-1. xl50 7, 8 . Uviserina auberiana. RD119. xl50 9, 10. Angulogerina selsevensis. 9. RD117. x200:10. RD19. x200 11, 12. Angulogerina jamaicensis. DM13-4. x350 13. Angulogerina eximia. RD22. xl50 14. Reussella spinulosa. RD46v. x200 15, 16. Pleurostpmella altemans. RD131.15. side view: 16. edge view. xlOO 17. Siemavirgulina tortuosa. RD59. xl50

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PLATE 4.4

1. Siphonodosaria paucistriata. RD9v. x75 2. Siphonodosaria nuttalli. RD9v. x75 3, 4, 5. Gavelinopsis sp. A. DM5-11. 3. ventral view, 4. edge view, 5. dorsal view, x200 6, 7. Gavelinopsis transluscens. DM10-2. 6. ventral view, 7. dorsal view, x200 8 , 9. Valvulineria mexicana. RD131. 8 . ventral view, 9. dorsal view, xl50 10,11. Valvulineria gasparensis. RD74a. 10. dorsal view, 11. ventral view, xl50 12, 13. Cancris sagra. RD84v. 12. dorsal view, 13. ventral view, x200 14,15, 16. Eponides weddellensis. RD117.14. dorsal view, 15. edge view, 16. ventral view, x350 17, 18, 19. Rosalina concinna. DM13-8. 17. ventral view, 18. edge view, 19. dorsal view, x350

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PLATE 4.5

1. Sphaeroidina bulloides. RD9v. xlOO 2. Siphonina bradvana. RD59v. xlOO 3. Siphonina pulchra. RD76v. xlOO 4. Laticarinina pauperata. RD131v. xlOO 5, 6. Planulina renzi. RD125.5. dorsal view, 6. ventral view, x50 7, 8 . Planulina ariminensis. RD131.7. ventral view, 8 . dorsal view, x75 9, 10. Cibicides wuellerstorfi. RD131v. 9. dorsal, 10. ventral, xlOO 11, 12, 13. Cibicides lobatulus. RD14. 11. ventral view, 12. edge view, 13. dorsal view, xlOO 11, 12. Cibicides cicatricosus. RD126.14. dorsal view, 15. ventral view, xlOO

PLATE 4.6

1, 2. Cibicidoides bametti. RD38.1. dorsal view, 2. ventral view, xlOO 3, 4. Cibicidoides bradvi. RD 66. 3. dorsal view, 4. ventral view, xlOO 5, 6, 7. Cibicidoides incrassatus. 5 , 6, RD36. 5. ventral view, 6. edge view, x75; 7. RD131. dorsal view, x75 8, 9, 10. Cibicidoides mundulus. RD129. 8 . dorsal view, 9. edge view, 10. ventral view, xlOO 11,12,13. Cibicidoides pachvderma forma bathvalis. RD36.11. ventral view, 12. edge view, 13. dorsal view, xlOO 14,15. Cibicidoides pachvderma forma siihlinoTalis. DM13-4.14. dorsal view, 15. ventral view, x200 16, 17. Cibicidoides perforatus. RD119.16. ventral view, 17. dorsal view, xlOO

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PLATE 4.7

1, 2, 3. Cibicidoides sinistralis. RD36.1. dorsal view, 2. edge view, 3. ventral view, x75 4. Asterieerina carinata. RD131. ventral view, x75 5, 6. Anomalina flintii. RD119.5. dorsal view, 6. ventral view, xlOO 7, 8. Nonion? sp. A. DM13-4.7. edge view, 8. side view, x350 9, 10. Havnesina depressula. DM13-3. 9. side view, 10. edge view, x350 11. Pseudononion atlanticum. RD84v. xl50 12. Pseudononion grateloupi. RD84v. xl50 13, 14. Melonis pompilioides. RD9b. 13. side view, 14. edge view, xl50 15, 16. Melonis affinis. RD74a. 15. side view, 16. edge view, xl50

PLATE 4.8

1, 2. BermudezineUa riveroi. RD33.1. side view, 2. edge view, xl50 3, 4. Pullenia bulloides. RD131v. 3. side view, 4. edge view, x200 5, 6. Pullenia subcarinata. RD66. 5. egde view, 6. side view, x200 7, 8. Oridorsalis umbonatus. 7. RD36. ventral view, xlOO. 8 . RD131v. dorsal view, xlOO 9,10. Gvroidina sp. cf. G. umbonata. DM13-3. 9.ventral view, 10. dorsal view, x200 11, 12,13. Gvroidina umbonata. RD76.11. ventral view, 12. edge view, 13. dorsal view, x200 14,15. Gvroidina trincherasensis juveniles. DM10-2.14. ventral view, 15. dorsal view, xl50 16, 17, 18. Gvroidina trincherasensis. RD12.16. ventral view, 17. edge view, 18. dorsal view, x50. 19, 20. Gvroidina laevis. RD76.19. ventral view, 20. dorsal view, xlOO 21, 22, 23. Gvroidina altiformis. RD131. 21. dorsal view, 22. edge view, 23. ventral view, xlOO

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PLATE 4.9

1, 2, 3. Gvroidina altispira. RD129.1. dorsal view, 2. edge view, 3. ventral view, x75 4, 5. Gvroidina girardana juveniles. RD113. 4. dorsal view, 5. dorsal view, xl50 6, 7, 8 . Gvroidina girardana. RD113. 6. dorsal view, 7. edge view, 8. ventral view, x75 9, 10, 11. Gvroidina regularis. RD38. 9. dorsal view, 10. edge view, 11. ventral view, x350 12,13. Hanzawaia sp. A. RD131.12. ventral view, 13. dorsal view, xlOO 14,15. Ammonia parkinsoniana RDlOlv. 14. dorsal view, 15. ventral view, xl50 16. Elphidium gunteri forma salsum. RD lOlv. xl50

MIGRATION OF NEOGENE MARINE ENVIRONMENTS, SOUTHWESTERN DOMINICAN REPUBLIC

(to be submitted to Geology)

226

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ABSTRACT

A 4000-m-thick regressive sequence of Neogene elastics is preserved in the Azua Basin, an elongate, NW-SE oriented, sedimentary trough in the southwestern Dominican Republic. Shifts of benthic foraminiferal facies boundaries between stratigraphic sections demonstrate a southeastward migration of faunal depth zones in the late Miocene and early Pliocene. This is corroborated by the disposition of time-transgressive lithofacies. The top of the lowest Neogene unit in the Azua Basin, the Sombrerito Formation, is approximately coincident with the lower bathyal - middle bathyal zone boundary. The boundary between the middle and upper bathyal biofacies is indicated near the middle of Trinchera Formation turbidite sequence by the disappearances of Pvrgo murrhina. Eggerella propinqua. Uvigerina hispida. and Cibicides wuellerstorfi. The highest stratigraphic occurrences of Siphonina tenuicarinata. Pullenia bulloides. Sphaeroidina bulloides. Oridorsalis umbonatus. Uvigerina peregrina. and Karreriella bradvi mark the termination of the upper bathyal biofacies near the top of the Trinchera Formation. Typical neritic species, such as Cassidulina laevigata. Siphonina pulchra. Pseudononion atlanticum. P. grateloupi. Reussella spinulosa. Cancris sagra. Elphidium lanieri. and Ammonia parkinsoniana. appear above this level in two clastic units, the Quita Coraza and the Arroyo Blanco Formations. The lower bathyal pelagic sediments of the Azua Basin range from upper lower Miocene in the northwestern end of the basin to lower upper Miocene in the south. The marine clastic sequence ranges from upper middle Miocene to upper upper Miocene in the northwest and from upper Miocene to lower Pliocene in the southern part. In the northwest, the placement of the boundary between the middle and upper bathyal biofacies falls within the upper part of the upper Miocene Globorotalia humerosa chronozone; the bathyal-neritic facies boundary lies near the top of the same zone. In contrast, towards the

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southeastern (i.e., seaward) end of the basin, the middle-upper bathyal biofacies boundary is just above the base of the lower Pliocene Globorotalia margaritae chronozone, and the bathyal-neritic transition falls within the upper three-fourths of the same zone. The timing of paleoenvironmental migration and accompanying transgression of lithofacies suggests that the Hispaniola "restraining bend" was activated near the beginning of the late Miocene.

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INTRODUCTION

A thick, nearly continuous Neogene sedimentary sequence in the Azua Basin of the southwestern Dominican Republic records the effects of neotectonic activity along the northern boundary of the Caribbean Plate. Deep-marine carbonates, turbidites, and shallow-marine elastics together comprise a sequence of up to 4000 m thickness that is well-exposed in dry streams and roadcuts in this semi-arid region. Generally rich and well- preserved foraminiferal faunas from this area were first described by Bermudez (1949). These faunas were considered Oligocene and Miocene in age and ascribed to a variety of environments, from deep-sea to nearshore. We have examined the foraminiferal assemblages in over 50 systematically collected samples from all parts of the Azua Basin and have constructed a model for the migration of marine environments through the Miocene and Pliocene.

REGIONAL SETTING AND STRATIGRAPHY

The Azua Basin is an elongate, northwest-southeast oriented synclinal sedimentary trough that opens up towards the Caribbean Sea. The north / northwestern arm of the basin is bounded by Cretaceous and Paleogene rocks that comprise thrust blocks of the Cordillera Central to the northeast and the Sierra de Neiba to the southwest (Fig. 5.1). The more seaward, southerly end of the basin lies at the distal end of the Sierra de Neiba fold-thrust belt and is slightly more removed from the Cordillera Central than the northern arm. The Neogene marine sedimentary record is represented by a dominantly clastic, 4000 m thick regressive interval which includes 4 formations, in ascending order: the Sombrerito Formation; the Trinchera Formation; Quita Coraza Formation; and Arroyo Blanco Formation. The Sombrerito Formation is characterized by soft, buff pelagic

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Strata Non-marine Alluvium Plio-Pleistocene Stock Paleocene-Oligocene Strata Volcanic with Plunge Arroyo Blanco Fm. Trinchera Fm. Quaternary Undifferentiated Quito Coraza Fm. Sombrerito Fm. Fold Fold Axes ■:Tob:: A Thrust Faults | Qal | Quaternary fejnmjj Undifferentiated llT qct brtrj £ 3 S

70 40

Trough Bay ^•~_r.'Muertos_ CENTRAL D O M . •' A CORDILLERA <3"//A O coa HAiTV „ REP. HAITI

DE 5 SIERRA MARTINGARCIA Figure 5.1 - Generalized geologic map of the Azua Basin. Azua the of map geologic Generalized - 5.1 Figure yUlf/miik

DE " i s - ' NEIBA L del Rincon SIERRA -18 40 -18 -18 20

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limestones and marls. This unit occurs in scattered outcrops and is in most places structurally disrupted. Although we have only studied short intervals, its thickness is estimated to be over 800 m (Osiris de Leon, 1978). The Gajo Largo Member of the Sombrerito comprises the upper 200 m of the unit in the southern part of the basin. It includes a significant volume of rhythmically-bedded, shallow-marine carbonate sediment gravity flow deposits. The Trinchera Formation is characterized by a thick sequence (1300 - 2200 m) of interbedded deep-marine mudstones and dirty turbidite sandstones and is generally well exposed in continuous sections. An upward trend from outer turbidite fan facies in the lower part of the formation to inner fan facies in the upper part is evident throughout the basin. In the southern part of the basin, shallow-marine siltstones and mudstones of the Quita Coraza Formation are present. However, this unit is absent in the northern arm of the basin, where the Trinchera Formation passes directly into the Arroyo Blanco Formation. Its thickness ranges from 300 to 700 m. The Arroyo Blanco Formation is a predominantly clastic unit dominated by nearshore and non-marine sediments. It apparently represents a coastal deltaic complex that

produced a thick (1000 m) coarsening-upward sequence composed of many fining-upward cycles. In the southern part of the basin, scattered coral beds and small reefs occur near the base of the sequence and gypsum is present in the upper strata.

BENTHIC FORAMINIFERA AND PALEOENVIRONMENTS

Benthic foraminiferal faunas from Sombrerito Formation sections in both the north and south ends of the basin are quite similar. Environmentally notable species present in this unit are listed in Table 5.1. Cibicides wuellerstorfi is present in nearly all samples of

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S o m b re rito lower Trinchera upper Trinchera Laticarinina pauperata (I) Laticarinina pauperata Oridorsalis umbonatus Pyrgo murrhina Pyrgo murrhina Pullenia bulloides Oridorsalis umbonatus Oridorsalis umbonatus Siphonina tenuicarinata Pullenia bulloides Pullenia bulloides Cibicides wuellerstorfi (r) Siphonina tenuicarinata Siphonina tenuicarinata Cassidulina subglobosa Uvigerina hispida Uvigerina hispida Sphaeroidina bullloides Eggerella propinqua (I) Eggerella propinqua Stilostomella sp p . Cibicides wuellerstorfi Cibicides wuellerstorfi Siphonodosaria spp. Cassidulina subglobosa (I) Cassidulina subglobosa Karreriella bradyi Sphaeroidina bullloides (I) Sphaeroidina bullloides Uvigerina peregrina Stilostomella sp p . Stilostomella sp p . Uvigerina carapitana Siphonodosaria spp. Siphonodosaria sp p . Hoeglundina elegans Melonis pompiloides (r)

Quita Coraza Arrovo Blanco Cassidulina subglobosa Cancris sagra Heoglundina elegans Haynesina depressula Reussella spinulosa Elphidium sp p . Siphonina pulchra Ammonia parkinsoniana Pseudononion atlanticum Pseudononion grateloupi Cassidulina laevigata Cancris sagra Haynesina depressula Elphidium spp. Ammonia parkinsoniana

Table 5.1 - Paleoenvironmentally important benthic foraminiferal species in the Azua Basin Neogene sedimentary sequence. (r)=rare, (l)=large.

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the Sombrerito; it generally only becomes common at depths of 1000 m or greater (van Morkhoven et al, 1986; Pflum and Frerichs, 1976). Another common Sombrerito group, the stilostomellids (mainly species of Stilostomella and Siphonodosaria'). are most strongly associated with the lower bathyal - middle bathyal boundary and deeper environments (Berggren and Haq, 1976; Bandy and Rodolfo, 1964; Ingle, 1980). Occurrences of Osangularia mexicana are most common in this interval; this species appears to be related to Osangularia culter. which characterizes Recent lower bathyal - middle bathyal faunas (Denne and Sen Gupta, 1988; Pflum and Frerichs, 1976; Phleger and Parker, 1951). The large size of some species evident here, such as Eggerella propinqua. Sphaeroidina bulloides. Laticarinina pauperata. and Cassidulina subglobosa. has been associated with v lower bathyal faunas (Pflum and Frerichs, 1976). Based on these criteria, the Sombrerito faunas are interpreted to represent deposition in the upper part of the lower bathyal zone (Figure 5.2). The onset of siliclastic sedimentation reflected in the Trinchera Formation is accompanied by shoaling in both the northern and southern parts of the basin.The benthic foraminiferal faunas in the outer and middle turbidite fan facies of the lower part of the Trinchera Formation (Table 5.1) show strong affinities with the underlying Sombrerito faunas but contain fewer species of agglutinated foraminifera. Typically middle bathyal or deeper species such as Laticarinina pauperata. Osangularia mexicana. Pvrgo murrhina. Eggerella propinqua. and Uvigerina hispida (van Morkhoven et al, 1986; Pflum and Frerichs, 1976) have their stratigraphically-highest occurrences in this part of the Trinchera. Therefore, the lower part of the Trinchera Formation is interpreted as middle bathyal. The benthic foraminifera present in the middle and inner submarine fan facies of the upper part of the Trinchera Formation (Table 5.1) indicate shoaling to upper bathyal depths. Middle bathyal species of the lower Trinchera interval disappear near the middle of

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C z

7H < 3500 O' z K o 2000 o <

3000

1500

2500 CO Z z iooo H £ i 2000 - f - ? H

500 H lO.

1500 H o his? co < o i o o o H b)

500 H

z Exjr q limestone frjrr^jj morl

G A J0 1 I mudstone yvft.v-; sandstone LARGO conglomerate

Figure 5.2 - Bathymetric curves for the Azua Basin Neogene sedimentary sequence, a) the southern part of the basin; b) the north and northwestern part of the basin

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the formation, while Cibicides wuellerstorfi barely persists into the upper part of the formation. A number of species which are typical of Recent and Neogene upper bathyal faunas, including Karreriella bradvi. Uvigerina peregrin a. Uvigerina carapitana. and Hoeglundina elegans (Denne and Sen Gupta, 1988; van Morkhoven et al, 1986; Pflum and Frerichs, 1976; Phleger and Parker, 1951), appear or are most common in the upper part of the Trinchera. The Quita Coraza Formation represents a neritic environment. Typically bathyal species present in the Trinchera Formation, such as Siphonina tenuicarinata, Pullenia bulloides. Siphonina bulloides. Oridorsalis umbonatus. Karreriella bradvi. and Uvigerina peregrina disappear below the base of the Quita Coraza. The lower part of the Quita Coraza contains an assemblage (Table 5.1) comparable to those from Recent outer neritic environments in the Gulf of Mexico (Phleger and Parker, 1951; Poag, 1985) and the Caribbean region (Drooger and Kaasschieter, 1958; Todd and Bronnimann, 1957). Upward this changes into an inner neritic assemblage characterized by Ammonia parkinsoniana. Cancris sagra. Havnesina depressula. and species of Elphidium. The Arroyo Blanco Formation contains nearshore, shallow- to marginal-marine benthic foraminifera (Table 5.1). Cancris sagra and Havnesina depressula are present in some samples and reflect more normal-marine settings, but marginal-marine Ammonia parkinsoniana and species of Elphidium dominate in most.

BIOSTRATIGRAPHY

The planktonic foraminifera suggest that Sombrerito deposition is diachronous between the northern and southern parts of the basin. Based on the zonation of Bolli and Saunders (1985), the northern faunas are characteristic of the lower and middle Miocene. In the westernmost exposures sampled, at Rio Los Baos, the presence of Globigerinoides

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bisphaericus. Praeorbulina transitoria. and Globigerinatella insueta are indicative of the lower Miocene Globigerinatella insueta zone. Further east, at Arroyo Sombrerito, the presence of Globorotalia fohsi peripheroacuta and Globorotalia praemenardii suggest equivalence to the Globorotalia fohsi fohsi zone. In contrast, the faunas present in the southern exposures of the Sombrerito are indicative of the middle and upper Miocene. Globorotalia fohsi robusta and Globorotalia menardii are present in samples collected near Canoa, placing them in the upper part of the Globorotalia fohsi robusta zone. Several kilometers to the northeast, the Gajo Largo Member was found to range from the middle Miocene Globorotalia maveri zone into the lower part of the upper Miocene Globorotalia acostaensis zone, where small 4 chambered forms of the nominate species are present. Planktonic foraminifera indicate that the lower part of the Trinchera Formation becomes younger towards the south. In the northern part of the Azua Basin, this interval ranges from near the middle Miocene - upper Miocene boundary (Globorotalia menardii chronozone or lower part of the Globorotalia acostaensis chronozone), based on the presence of Globorotalia lenguaensis. to the uppermost Miocene (upper part of the Globorotalia humerosa chronozone), based on occurrences of Candeina nitida. This same interval spans the Miocene / Pliocene boundary in the southern part of the basin, where Globorotalia margaritae margaritae first appears 300 m above the base of the 2200 m thick Trinchera section. The same trend appears to hold in the upper part of the Trinchera; it is younger in the southern part of the basin. Samples collected in the northern arm of the basin are placed in the uppermost part of the Miocene (upper part of the Globorotalia humerosa zone), based on the presence of Candeina nitida and the absence of any Pliocene marker species. Outcrops in the southern end of the basin are lower Pliocene, laying in the upper three- fourths of the Globorotalia margaritae zone. Globorotalia margaritae margaritae and

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Globigerina nepenthes are present, and Globigerinoides ruber reappears approximately 200 m below the top of the formation. Planktonic foraminifera are present in reduced numbers and diversity in the Quita Coraza Formation. Globorotaliids are generally restricted due to shoaling. However, the position of this unit above the first-occurrences of Globorotalia margaritae margaritae and Globigerinoides ruber, and the presence of Globigerina nepenthes, indicates a position somewhere in the upper part of the lower Pliocene Globorotalia margaritae chronozone. Spotty planktonic foraminiferal occurrences in the lower pan of the Arroyo Blanco Formation suggests it may also follow a southward-younging trend. The presence of Candeina nitida and absence of Pliocene markers in the northern part of the basin indicates a position in the upper part of the upper Miocene Globorotalia humerosa chronozone. Stratigraphic position and the persistence of Globigerinoides obliquus obliquus and Globoquadrina altispira altispira suggest that the more southerly exposures lie in the upper part of the lower Pliocene Globorotalia margaritae chronozone.

MIGRATION OF PALEOENVIRONMENTS

From the foraminiferal data presented here, the migration of paleoenvironments may be traced through the Miocene and Pliocene for the Azua Basin (Figure 5.3). In the middle of the middle Miocene and earlier, all of the southwestern Dominican Republic appears to have been at lower bathyal depths and greater. Middle bathyal faunas first appeared in the later part of the middle Miocene at the northwestemmost end of the Azua Basin and migrated to the open southern end of the basin in the late Miocene. This same path was followed by the upper bathyal faunas in the late Miocene. By the early Pliocene, bathyal faunas were restricted to the southern part of the basin, with shallow- and marginal- marine environments advancing from the north through the Pliocene.

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middle middle Miocene earliest Pliocene

late middle Miocene1 late early Pliocene

.1000, 1000

early late Miocene middle Pliocene

latest Miocene

■600. marginal/non* marine g g g j middle bathyal [600 n eritic □ lower bathyal

upper bathyal 0 ^ ^ bathymetric contour

Figure 5.3 - Diagram of paleoenvironmental migration through the Miocene and Pliocene.

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The seaward migration of paleoenvironments demonstrated here is paralleled by time transgression of lithofacies. Paleocurrents and lithofacies distribution indicate that the basin took on its present thrust-block bound configuration in the late Miocene (McLaughlin and Bold, in review). The environment changed at that time from a deep, open-ocean setting to an elongate sedimentary trough that was filled by a sudden influx of large volumes of elastics derived from the bounding mountain blocks. Sole marks in the Trinchera turbidite sequence demonstrate predominantly southeastward, basin axis-parallel sediment transport in the northwestern part of the basin and shift southwestwardly in the southern part of the basin where it opens up into the Caribbean.

TECTONIC IMPLICATIONS

The paleoenvironmental migration described above appears to reflect rapid infilling of a subsiding sedimentary trough. The Azua Basin was filled by a sediment thickness of up to two and one-half times its original depth during the late Miocene and Pliocene. Uplift of the bordering Cordillera Central and Sierra de Neiba fold-thrust belts apparently provided the load needed to drive isostatic subsidence of the basin floor through lithospheric flexure, as well as providing a sediment source. Petrographic analysis of sandstones in the Trinchera Formation indicates that the Cordillera Central was the primary source for the large influx of sediments (McLaughlin and Bold, in review). The basin-axis parallel paleocurrent trend suggests that the Sierra de Neiba had arisen on the southwest side of the basin, deflecting sediment flowing southwestward from the Cordillera Central into a southeasterly oriented sedimentary trough. Mann et al. (1984) have proposed that the island of Hispaniola foims a "restraining bend" in the northern Caribbean Plate Boundary Zone. The northwestward anticlinal thrust block mountain belts and intervening synclinal basins that characterize Hispaniola may have

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been shaped through transpressional, wrench fault neotectonic activity in this restraining bend. We suggest that these transpressional neotectonics began near the start of the late Miocene. Our study of the foraminfera of the Azua Basin indicates that a seaward advance of paleoenvironments took place in the late Miocene and early Pliocene. This advance accompanied the formation and rapid growth of the Trinchera turbidite fan out an elongate sedimentary trough, the Azua Basin, that was bounded by two rising fold-thrust belts, the Cordillera Central and the Sierra de Neiba.

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REFERENCES

Bandy, O.L., and Rodolfo, K.S., 1964. Distribution of foraminifera and sediments, Peru- Chile trench area. Deep Sea Research, v. 11, p. 817-837.

Berggren, W.A. and Haq, B.L, 1976. The Andalusian Stage (Late Miocene): Biostratigraphy, biochronology, and paleoecology: Paleogeography, Paleoclimatology, Paleoecology, v. 20, p. 67-129.

Bermudez, P.J., 1949. Tertiary smaller foraminifera of the Dominican Republic: Cushman Laboratory for Foraminiferal Research Special Publication, v. 25,322 p.

Denne, R.A., and Sen Gupta, B.K., 1988. Abundance variations of dominant benthic foraminifera on the northwestern Gulf of Mexico slope: relationship to bathymetry and water mass boundaries. Inst. Geol. Bassin d'Aquitaine, Bull., v.44, in press.

Drooger, C.W., and Kaasschieter, J.P.H., 1958. Foraminifera of the Orinoco-Trindad- Paria shelf. Reports of the Orinoco Shelf expedition, v. 4. Veihandelingen der Koninklijke Nederlandse Akademie van Wetenschappen, Afdeling Natuurkunde,

ser. 1, v. 2 2 , p. 1-108.

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Mann, P., Burke, K., and Matumoto, T., 1984. Neotectonics of Hispaniola: plate motion, sedimentation, and seismicity at a restraining bend: Earth and Planetary Science Letters, v. 70, p. 311-324.

Morkhoven, F.P.C.M. van, Berggren,W.A., Edwards, E., and collaborators, 1986. Cenozoic Cosmopolitan Deep-water Benthic Foraminifera: Pau, Bulletins de Centres de Recherche Exploration-Production Elf-Aquitaine, Mem. 11,421 p.

Osiris de Leon, R., 1978. Aspectos geologicos e hidrogeologicos de la region suroeste. Museo National de Historia Natural (Republica Dominicana), Publicaciones Especiales, Numero 4,25 pp.

Pflum, C.E., and Frerichs, W.E., 1976. Gulf of Mexico deep-water foraminifers: Cushman Foundation for Foraminiferal Research, Special Publication 14, p. 7-125.

Phleger, F.B., 1951. Ecology of foraminifera, northwest Gulf of Mexico; Part 1 - Foraminifera distribution: Geological Society of America, Memoir 46, v.l, p. 1-88.

Poag, C.W., 1981. Ecologic Atlas of Benthic Foraminifera of the Gulf of Mexico: Stroudsburg, Pennsylvania, Hutchinson Ross Publishing Company, 174 p.

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Todd, R., and Brdnnimann, P., 1957. Recent Foraminifera and Thecomoebina from the eastern Gulf of Paria. Cushman Foundation for Foraminiferal Research, Special Publication 3, p. 1-43.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. C H A E IE B L ti

NEOGENE BENTHIC FORAMINIFERA FROM THE DOMINICAN REPUBLIC: TAXONOMIC PROBLEMS AND SOLUTIONS

(to be submitted to Journal of Foraminiferal Research)

244

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT

The Neogene foraminifera of the southwestern Dominican Republic comprise a rich fauna sharing species with both Recent and Neogene assemblages of the circum-Caribbean region. Although a number of species similar to existing forms have been described in previous reports from this region, no serious comparative studies have been undertaken. In this paper, we propose new synonymies for 7 species: Angulogerina iamaicensis. Angulogerina selsevensis. Bulimina tessellata. Cibicides cicatricosus. Eponides weddellensis. Gvroidina laevis. and Uvigerina carapitana. Study of the Dominican Republic foraminifera supports synonymies previously proposed for 7 other species: Bulimina mexicana. Cibicidoides incrassatus. Cibicidoides mundulus. Cibicidoides pachvderma. Gvroidina umbonata. Pullenia subcarinata. and Melonis affinis.

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INTRODUCTION

The Neogene strata of the Dominican Republic contain rich deep-marine to nearshore foraminiferal faunas. The island of Hispaniola, of which the Dominican Republic is a part, is divided into a series of northwesterly-trending mountain belts alternating with Neogene sedimentary basins. These basins were studied and sampled in the early 1940s by geologists of the Dominican Seaboard Oil Company. In an extensive study of these samples, Bermudez (1949) described over 833 species and varieties of smaller foraminifera, including 243 new forms. This study has brought attention to the Dominican Republic foraminifera; for example, van Morkhoven et al. (1985) ieccognize the "Hispaniola Fauna" as a representative example of Neogene deep-marine assemblages. However, the usefulness of existing reports, including that of Bermudez (1949), in current foraminiferal studies is hindered by two primary problems. First, in most studies conducted earlier in the century, little effort was made to compare fossil and Recent assemblages. Second, references to ages of benthic foraminiferal species, such as those in the "Hispaniola Fauna", have been based upon older, outdated biostratigraphy and may give misleading impressions of the ranges of species. We have had the opportunity to examine the Miocene and Pliocene smaller foraminifera of the southern part of the Dominican Republic (Fig. 6.1), where the deep- marine faunas described by Bermudez (1949) are best developed. Our study reveals that a number of Neogene and Recent species described under separate names are synonymous. The proliferation of taxonomic names used for these forms has prevented full understanding of the paleoecologic and biostratigraphic significance of Neogene benthic foraminifera and has resulting in the entrenchment of some junior synonyms in the literature. In this paper, we discuss the taxonomic problems related to 14 benthic foraminiferal

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Strata Non-marine Paleocene-Oligocene Strata Alluvium Plio-Pleistocene Stock Volcanic Trinchera Fm. Undifferentiated Arroyo Blanco Fm. Quito Coraza Fm. Fold Fold Axes Sombrerito Fm. 4 k Quaternary * Ai Thrust Faults >:Tab;:: Ejnmj] Undifferentiated | | Qal | Quaternary EH E < 4 - with Plunge

70 40 70 trough CENTRAL 10 20km _i _i i CORDILLERA O c o a Bay HAITI/ HAITI/ DOM.

DE DE • '/// SIERRA? MARTINGARCIA Figure 6.1 - Generalized geologic map of the Azua Basin. Azua the of map geologic Generalized - 6.1 Figure ■ jfnm w K Tp / Qat U U //l//jt Juan

Rincon

" I s - - ' DE L. del del L. NEIBA SIERRA 18 40 18

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species present in the Azua Basin. In several cases, we point out that more obscure species names originally applied to Neogene taxa of the Caribbean - Gulf of Mexico region are senior synonyms of more well-known species described from the Recent. In others, we propose solutions to a maze of nomenclature applied to very similar forms. In addition, we discuss the distribution of these benthic species in the context of recent planktonic foraminiferal biostratigraphy in the basin (McLaughlin, 1989).

GEOLOGIC SETTING

The Azua Basin is an elongate, northwest-southeast oriented synclinal Neogene sedimentary trough partially bounded by Cretaceous - Paleogene rocks that comprise the thrust blocks of the Cordillera Central and the Sierra de Neiba (Figure 6.1). The basin is filled with a predominantly clastic, south to southeastward time-transgressive, upward- coarsening marine sedimentary sequence that includes four sedimentary units (McLaughlin and Bold, in review). The Sombrerito Formation represents lower to middle bathyal, predominantly carbonate deposition, and ranges from uppermost lower Miocene to lowermost upper Miocene. Most of our samples are from the Trinchera Formation, which is a unit of middle to upper bathyal turbidite deposits that extends from the uppermost middle Miocene to the lower Pliocene. The Quita Coraza Formation is found only in the southern end of the basin and includes middle to outer neritic mudstones placed in the lower Pliocene. Lower Pliocene inner neritic to nearshore deposits comprise the Arroyo Blanco Formation.

TAXONOMY

Suborder ROTALENA Delage and Hdrouard, 1896

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Superfamily BULIMINACEA Jones, 1875 Family BULIMINIDAE Jones, 1875 Genus BULIMINA d'Orbigny, 1826

Bulimina mexicana Cushman. 1922 Plate 6.1, Fig.l

Bulimina inflata Sequenza var. mexicana Cushman, 1922, p. 95, PI. 21, fig. 2. Bulimina bleeckeri Hedberg, 1937, p. 675, PI. 91, figs. 12,13; Bermudez, 1949, p. 180, PI. 12, fig. 7; Becker and Dusenbury, 1958, p. 28, PI. 4, fig. 7. Bulimina striata d'Orbigny var. mexicana Cushman. Cushman and Parker, 1940, p. 16, PI. 3, fig. 9. Bulimina striata mexicana Cushman. Akers and Dorman, 1964, p. 29, PI. 7, fig. 15; Kohl, 1985, p.67, PI. 20, fig. 4. Bulimina mexicana Cushman, van Morkhoven, Berggren and Edwards, 1985, p. 59, pi. 60.

Description.- Test free, triserial, conical in outline, chambers with approximately 5-7 strong, longitudinal costae ending in narrow spines which slightly overhang the previous whorl; upper surface of the final 3 chambers and surface between costae smooth and porous, costae occasionally with pores; aperture loop-shaped with internal toothplate. (after van Morkhoven et al., 1985) Distribution.- This species is widely distributed in the Gulf of Mexico and Caribbean regions in both recent and Neogene deposits. Most occurrences in the Azua Basin are from upper Miocene and lower Pliocene bathyal deposits of the Trinchera Formation.

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Remarks.- Bulimina mexicana was determined by van Morkhoven et al. (1985) to include several similar, previously described species of Bulimina which vary in the quantity and development of costae and the presence or absence of spines. Although suspecting that Bulimina costata d'Orbigny and Bulimina striata d'Orbigny may lie within this group, they were not able to locate the type material of either of the species for comparison and chose to use the name B. mexicana for this form. We agree with this approach and consider the form figured by Bermudez (1949) as B. bleeckeri to represent B. mexicana.

Bulimina tessellata Cushman and Todd, 1945 Plate 6.1, Figs. 2, 3

Bulimina marginata d'Orbigny var. tessellata Cushman and Todd, 1945, p. 39, PI. 6, fig. 9. Bulimina spicata Phleger and Parker, 1951, p. 16, pi. 7, fig. 25, 30, 31; Parker, 1954, p.

510, PI. 6, figs. 22, 23; Kohl, 1985, p. 6 6, PI. 20, fig. 5.

Description.- Test free, small, triserial, conical, longer than broad, initial end often with small spine; 3 to 4 whorls in test; last formed whorl comprises over one-half of test length; chambers fairly distinct, slightly inflated, those of each whorl slightly overhanging previous ones, with indistinct short costae ending in downward projecting sharp spines at margin; surface of final whorl and between costae is smooth with distinct pores; aperture loop-shaped, elongate, (after van Morkhoven et al., 1985) Distribution.- This species is found in the upper Miocene and lower Pliocene Trinchera Formation and less commonly in the lower Pliocene strata of the lower part of the Quita Coraza Foormation. It is known from the Pliocene of Jamaica (Cushman and Todd, 1945), and as B. spicata from the Recent of the Gulf of Mexico (Phleger and Parker,

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1951; Parker, 1954) and the Pliocene of the Salinas Basin of southeastern Mexico (Kohl, 1985). Remarks.- Cushman and Todd described B. marginata var. tessellata only as differing from the typical form in "the somewhat coarser spines and the wall which has large, prominent perforations arranged in linear patterns especially noticeable on the smooth, later portion of the chambers." The figures also appear to show indistinct costae on the lower part of the chambers. We have examined the holotype of Bulimina marginata var. tessellata and specimens of B. spicata Phleger and Parker from the northwestern Gulf of Mexico and have found them to be identical, sharing the characteristic indistinct costae, spines, and perforate wall.

Family UVIGERININAE Haeckel, 1894 Subfamily UVIGERININAE Haeckel, 1894 Genus UVIGERINA d’Orbigny, 1894

Uvigerina carapitana Hedberg. 1937. Plate 6.1, Figs. 4, 5

Uvigerina canariensis d'Orbigny var. Cushman, 1918, p. 63, PI. 22, fig. 6. Uvigerina carapitana Hedberg, 1937, p. 677, PI. 91, fig. 20; Cushman and Edwards, 1938, p. 82, PI. 14, fig. 2; Renz, 1948, p. 174, PI. 7, fig. 21; Bermtidez, 1949, p. 202, PI. 13, fig. 1; Becker and Dusenbury, 1958, p. 33, PI. 4, fig. 14. Uvigerina laviculata Coryell and Rivero, 1940, p. 343, PI. 44, fig. 24; Cushman and Todd, 1941, p. 49, PI. 12, fig. 5; Cushman and Todd, 1945, p. 50, PI. 7, fig. 25; Bermudez, 1949, p. 207, PI. 13, fig. 34. Uvigerina quadrata Coryell and Rivero, 1940, p. 343, PI. 42, fig. 27.

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Uvigerina gasparensis Bermudez, 1949, p. 205, PI. 13, figs. 2, 3.

Description.- Test free, triserial, elongate, weakly triserial in cross-section, approximately twice as long as broad, tapering, apical end bluntly pointed in microspheric forms, rounded in megalospheric; chambers inflated, laterally Iobed, increasing rapidly in size as added, last chamber squared on top; sutures distinct, depressed, with crenulations in some larger specimens; surface smooth, polished, some specimens with faint longitudinal striae which are usually best developed on the earlier portion; aperture terminal, in a depression near indented margin of last chamber, on a short neck with a lip. Distribution - This species is found in the middle and upper parts of the Trinchera Formation, which were lain down at middle and upper bathyal depths in the upper Miocene and lower Pliocene. Its occurrences appear to be restricted to the environmentally similar Miocene and Pliocene strata of the Caribbean region: the Dominican Republic (Bermudez, 1949); Haiti (Coryell and Rivero, 1940; Cushman and Todd, 1941); Cuba (Cushman and Edwards, 1938); Jamaica (Cushman and Todd, 1945); Panama (Cushman, 1918); Venezuela (Hedberg, 1937; Cushman and Edwards, 1938); and Colombia (Becker and Dusenbury, 1958). Remarks.- Uvigerina carapitana was first described from the Miocene of Carapita, Venezuela by Hedberg (1937). Uvigerina gasparensis. described from the Gaspar Zone of the Trinchera Formation by Bermudez (1949), was noted to differ from U. carapitana in its "greater size, more depressed and slightly crenulated sutures and more tapering form." Our examination of the holotype of U. carapitana confirms that it is indeed smaller than our Azua Basin "U. gasparensis" specimens; however, the forms are otherwise very similar, with variations in size as well as between forms with crenulated sutures and forms lacking distinct crenulations. Coryell and Rivero (1940) characterized

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their species U. laviculata as having a very lightly striate surface. Hedberg's (1937) description of U. carapitana noted faint longitudinal striarions on the early chambers, and our specimens exhibit variations between nearly imperceptibly striate to distinctly striate forms. Bermudez (1949) placed U. quadrata Coryell and Rivero in synonymy with IL carapitana.

Subfamily ANGULOGERININAE Cushman, 1927 Genus ANGULOGERINA Cushman, 1927

Angulogerina iamaicensis Cushman and Todd, 1945

Plate 6.1, Figs. 6, 7

Angulogerina iamaicensis Cushman and Todd, 1945, p. 53, PI. 8 , fig. 3. Angulogerina porrecta (H.B. Brady) var. fimbriata (Sidebottom). Bermudez, 1949, p. 218, PI. 13, fig. 56; Becker and Dusenbury, 1958, p. 36, PI. 4, fig. 21.

Description.- "Test small for genus, elongate, two to two and one-half times as long as broad, periphery slightly lobulate in front view, in end view triangular with concave faces; chambers numerous, loosely arranged, upper part of each wall excavated, lower part projecting; sutures deeply depressed; wall ornamented by high, sharp, longitudinal costae, about 5 to a chamber, those on each chamber independent and most strongly developed on the central part of the chamber, aperture at the end of a long, slender neck, with a phialine lip." (Cushman and Todd, 1945) Distribution.- This species is present in the Quita Coraza Formation, outer neritic deposits of lower Pliocene age. It is also known from the Miocene of northern Colombia (Becker and Dusenbury, 1958) and the Pliocene of Jamaica (Cushman and Todd, 1945).

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Remarks.- Angulogerina iamaicensis was described by Cushman and Todd (1945) from the Pliocene of Buff Bay, Jamaica. Based on our examination of the holotypes of A. iamaicensis. we feel that the Dominican form designated A. porrecta var. fimbriata by Bermudez is closely comparable to A. jamaicensis. Uvigerina porrecta var. fimbriata. described from off east Australia, is a predominantly uniserial form that does not appear to be triangular in cross section and probably is not an Angulogerina Sidebottom's description of this variety notes minute serrations at the peripheral edges of the chambers, but chamber surfaces otherwise free from decoration. In contrast, both Bermudez (1949) and Becker and Dusenbury (1958) figure costate forms with a triangular cross-section, overhanging chambers, and costate surface like that described for A. iamaicensis.

Angulogerina selsevensis (Heron-Alien and Eariand, 1909)

Plate 6.1, Figs. 8 , 9,10

Uvigerina selsevensis Heron-Alien and Eariand, 1909, p. 437, PI. 18, figs. 1-3; Cushman, 1913, p. 93, PI. 42, fig. 5. Angulogerina selsevensis Bermudez, 1949, p. 218, PI. 13, fig. 53.

Angulogerina bella Phleger and Parker, 1951, p. 12, PI. 6, figs. 7, 8 . Trifarina bella (Phleger and Parker). Bock, 1971, p. 49, PI. 17, fig. 13.

Description.- Test free, elongate, triserial; initial end subacute with irregular chambers, often with a few short, blunt terminal spines; in later portion of test, cross-section is irregular to triangular, strongly overhanging chambers with small spines along the bottom edge, chamber sides flattened to concave, sutures slightly depressed; aperture terminal, on a slender neck with a lip. (after Phleger and Parker, 1951)

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Distribution.- We find this species to be most common in the lower Pliocene Quita Coraza and Arroyo Blanco Formations with scattered occurrences in the upper Miocene and lower Pliocene strata of the Trinchera Formation. This species was described as a fossil from Sussex, England of unspecified age and has also been noted in Recent neritic and upper bathyal sediments of the North Pacific (Cushman, 1913), the Gulf of Mexico (as A. bella: Phleger and Parker, 1951) and the Straits of Florida (as T. bella: Bock, 1971). Remarks.- A. selsevensis Heron-Alien and Eariand and A. bella Phleger and Parker appear to be the same species. Both exhibit an irregular to triangular cross-section and overhanging, undercut chambers. However, the type description of A. selsevensis is very general and does not note details such as the pointed projections under the overhanging chambers that were attributed to A. bella. Nevertheless, the type figure of U. selsevensis bears great resemblance to A. bella and the A. selsevensis figured in Bermudez (1949) is identical in nearly all details.

Superfamily DISCORBACEA Ehienberg, 1838 Family EPONIDAE Hofker, 1951 Subfamily EPONIDAE Hofker, 1951 Genus EPONIDES de Montfort, 1808

Eponides weddellensis Eariand. 1936 Plate 6.1, Figs. 11,12,13, 14

Eponides weddellensis Eariand, 1936, p. 57, PL 1, figs. 65-67. Eponides rotundus Husezima and Maruhasi, 1944, p. 399, PI. 34, fig. 12a-c. Eponides pusillus Parr, 1950, p. 360, PI. 14, fig. 16a-c.

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Eponides turgidus Phleger and Parker, 1951, p. 22, PI. 11, figs. 9a, b; Poag, 1981, PI. 1, fig. 4, PI. 2, fig. 4.

Description.- Small, biconvex test, 3 to 5 whorls; rounded periphery; 4 or 5 chambers in the last whorl, long and narrow, slightly inflated dorsally, more distinctly inflated ventrally; sutures distinct, slightly depressed, in some cases strongly depressed on the ventral side; wall thin, transluscent, very finely perforate; aperture along, low slit about midway between the periphery and the umbilical region of the ventral side; diameter generally 0.14 to 0.19mm, thickness 0.09 to 0.14mm. Distribution.- We find this species in scattered samples from the Trinchera, Quita Coraza, and Arroyo Blanco Formations (upper Miocene to lower Pliocene). Its Recent distribution is cosmopolitan. Eariand (1936) described this species from the Weddell Sea ia an area of 3000- 5000m depth. This same form was also recorded (as E. pusillusl from 122-155m depth off eastern Tasmania (Parr, 1950), and (as E. turgidus') from 40m to over 3400m in the Gulf of Mexico (Phleger and Parker, 1951). Specimens have also been noted (as E. rotundusl in the Pliocene of Honshu Island Japan (Husezima and Maruhasi, 1944). Remarks.- This minute Eponides species was first described by Eariand as E. weddellensis. Other subsequently described small Eponides species such as E. rotundus. E. pusillus. and E. turgidus all represent the same form and correspond to our description above. Within populations that we have examined from the Neogene of the Azua Basin, the Holocene-Pleistocene of the Venezuela and Grenada Basins of the Caribbean, the Holocene of the Gulf of Mexico, and the Holocene-Pleistocene of the Sierra Leone Basin of the South Atlantic, E. weddellensis exhibits the same ranges of variation. The height of the whorl on the dorsal side and the degree of inflation of chambers on the ventral side may vary, giving slight differences in test thickness. For

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example, the form figured by Poag (1981) has a high conical dorsal spire. In the more ventrally-inflated forms, the degree of depression of the ventral sutures is commonly greater than in the flatter forms, and their curvature may appear to be less. In the flatter forms, each whorl is commonly narrower than in the thicker forms, and the periphery may become more acute. Most of our Azua Basin specimens are flatter types, with narrower whorls, lower spires, and less ventrally inflated chambers.

Superfamily DISCORBINELLACEA Sigal, 1952 Family PARRELLOIDIDAE Hofker, 1956 Genus CIBICIDOIDES Thalmann, 1939

Cibicidoides incrassatus (Fichtel and Moll, 1798) Plate 6.1, Figs. 15,16,17

Nautilus incrassatus Fichtel and Moll, 1798, p. 38, PI. 4, figs. a-c.

Truncatulina nucleata Seguenza, 1880, p. 64, PI. 7, fig. 8 . Cibicides nucleata (Seguenza), Galloway and Morrey, 1929, p. 31, PI. 4, fig. 9.

Truncatulina trinitatensis Nuttall. 1928, p. 97, PI. 7, figs. 3,5, 6. Cibicides trinitatensis (Nuttall), Nuttall, 1932, p. 33, PI. 7, fig. 9; Palmer and Bermudez, 1936, p. 315; ? Bermudez, 1949, p. 307, PI. 24, figs. 19-21. Anomalina nucleata (Sequenza), Coryell and Rivero, 1940, p. 334, PI. 44, fig. 2; Galloway and Heminway, 1941, p. 388, PI. 22, fig. 2. Cibicides nucleatus (Sequenza), Palmer, 1941, p. 296; Palmer, 1945, p. 73; Bermudez, 1949, p. 303, PI. 24, figs. 16-18. Anomalinoides trinitatensis (NuttalD. Renz, 1948, p. 115, PI. X, fig. 11. Cibicides dohmi Bermudez, 1949, p. 297, PI. 4, figs. 25-27.

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Cibicides robustus Phleger and Parker, 1951, p. 31, PI. 17, figs. 1-4 (homonym of Q robustus LeCalvez. 1949). Cibicides corpulentus Phleger and Parker, 1952 (nom. nov.), p. 14; Parker, 1954, p. 541,

PL 12, figs. 4, 8 . Anomalinoides corpulentus (Phleger and Parker), LeRoy and Levinson, 1974, p. 16, PI.

8 , figs. 4-6; Kohl, 1985, p. 96, PI. 35, fig. 1. Cibicidoides corpulentus (Phleger and Parker), Poag, 1981, p. 52, PI. 31, fig. 1, PI. 32, Fig. 1(??) Cibicidoides incrassatus (Fichtel and Moll), van Morkhoven, Berggren, and Edwards, 1985, p. 83, PL 25A, B, C.

Description. - Test free, large, robust, trochospiral, planoconvex to biconvex, approximately 13 chambers in the last whorl; approximately three and one-half whorls in the adult, inner whorls on dorsal side covered with shell material forming a well-defined glassy plug with scattered coarse pores surrounded by a distinct furrow, chamber sutures slightly curvaed and limbate, raised on the dorsal side, flush on the ventral; ventral sutures meet at slightly elevated glassy umbo; wall coarsely perforate between sutures; aperture interiomarginal and equatorial, extending onto dorsal side, (after van

Morkhoven et al., 1985; Phleger and Parker, 1951; and R 6gl and Hansen, 1984) Distribution.- In the Azua Basin, occurrences of this species are scattered through the Trinchera and Quita Coraza Formations and it is generally not abundant. It is a widely distributed species, and has been noted frequently (under a variety of names) as a component of Tertiary foraminiferal faunas of the Caribbean and Gulf of Mexico regions. Remarks.- van Morkhoven et al.(1985) discussed the basis for the placement of Nautilus incrassatus Fichtel and Moll in the genus Cibicidoides and for its synonymy with C.

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nucleatus. C. trinitatensis. and C. corpulentus. We have examined the holotypes of Cibicides dohmi Bermudez and beleive that it is also synonymous. Specimens we have found in our samples of lower Pliocene neritic deposits from the type area of C. dohmi ("deep-water" Higuerito Member of the Arroyo Blanco Formation sensu Bermudez = Quita Coraza Formation) compare closely to C. incrassatus and its synonymous forms: ”14 or 15 (chambers) in the last figured whorl; spiral suture depressed, not very distinct, chamber sutures strongly limbate, elevated, slightly oblique, thickening at the junction with the spiral suture; dorsal side with a large umbo of transparent shell material, umbilicus filled with clear shell material; wall thick, coarsely perforate in the areas between the limbate sutures." In our opinion, the forms identified as C. dohmi by Woodruff and Douglas (1981; Miocene of the Pacific) and by van Morkhoven et al. are probably another species. Figured speciemens show the same robust, unequally biconvex test shape as Bermudez's form. However, these forms are marked by a small number of large perforations and appear to lack glassy umbos and distinctly thickened limbate chamber sutures, van Morkhoven at al. (1985) reported that C. dohmi is a lower bathyal-abyssal taxon with a youngest known occurrence of middle Miocene (N9), whereas we find that Cibicides dohmi Bermudez (=€ . incrassatus! was first described from lower Pliocene outer neritic deposits.

Cibicidoides mundulus (Brady, Parker, and Jones, 1888) Plate 6.1, Figs. 18,19, 20

Truncatulina mundula Brady, Parker, and Jones, 1888, p. 228, PI. 45, fig. 25. Cibicides sp. 2 Phleger and Parker, 1951, p. 32, PI. 18, figs. 1,2.

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Cibicides kullenbergi Parker (in Phleger, Parker, and Peirson) 1953, p. 49, PI. 11, figs. 7,

8 -

Description.- Tset free, biconvex, trochospiral, biumbonate, approximately 10-12 chambers in the last whorl, 3 whorls in the adult, periphery acute with a narrow, thickened keel; on dorsal side, sutures oblique, slightly curved, thickened but flush, coarse perforations on final whorl and visible on earlier whorls through clear umbo; on ventral side, sutures thickened but flush, curving near periphery, surface finely perforate; aperture interiomarginal, equtoraial, extending onto dorsal side. ( after van Morkhoven et al., 1985; and Parker, Brady, and Jones, 1888) Distribution.- This species has rare occurrences in middle Miocene to lower Pliocene deep- marine strata of the Sombrerito Formation and the lower half of the Trinchera Formation. The present day distribution of this species is cosmopolitan and it occurs in bathyal and abyssal deposits. Remarks.- We follow the convention of van Morkhoven et al.(1985) who consider £. kullenbergi a junior synonym of C. mundulus. They note that size is the only essential difference they noted between the types of the two species.

Cibicidoides pachvderma (Rzehak, 1886) Plate 6.2, Figs. 1, 2, 3, 4,5

Truncatulina pachvderma Rzehek, 1886, p. 87, PI. 1, fig. 5a, b, c. Truncatulina ungeriana (d'Orbigny), Brady, 1884, p. 664, PI. 94, figs. 9a, b, c.

Cibicides pseudoungeriana (Cushman), Cushman, 1931, p. 123, PI. 22, figs. 3,4, 6. Cibicides pseudoungerianus (Cushman), Galloway and Heminway, 1941, p. 392, PL 23, fig. 5; Bermudez, 1949, p. 304, pi. 24, figs. 28-30.

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Cibicides floridanus (Cushman), Coryell and Rivero, 1940, p. 344, PI. 44, fig. 10; Galloway and Heminway, 1941, p. 392, PI. 23, fig. 2.

?Cibicides falconensis Renz. 1948, p. 128, PI. 11, figs. 7, 8 . Cibicides aff. floridanus (Cushman), Phleger and Parker, 1951, p. ?, PI. 16, figs. 1-4. Cibicides cf. pseudoungerianus (Cushman), Pflum and Frerichs, 1976, p. 29, PI. 2, fig. 9, PI. 3, figs. 1, 2. Cibicides "floridanus" forma bathvalis Poag, 1981, p. 53, PI. 29, fig. 1, PI. 30, fig. 1. Cibicides "floridanus" forma sublittoralis Poag, 1981, p. 53, PI. 29, fig. 2, PI. 30, fig. 2. Cibicidoides pachvderma (Rzehak), van Morkhoven, Rerggren, and Edwards, 1985, p.

6 8, PL 22.

Description.- see van Morkhoven et al. (1985). Distribution.- This is the most ubiquitous cibicidid in the Azua Basin Neogene, found in nearly every sample in the Trinchera and Quita Coraza Formations in abundances of up to 15%. van Morkhoven et al. (1985) report that this species is nearly cosmopolitan in distribution and ranges from the early Oligocene to the Recent. Remarks.- This form appears to have been referred to as C. pseudoungerianus by Bermudez (1949) in his study of Dominican Republic Tertiary foraminifera. Poag (1981) noted that many forms referred to as C. aff. floridanus and Q. floridanus differ from C. floridanus (Cushman) described from the upper Miocene of Florida, van Morkhoven et al. (1985) suggested placement of these forms in C. pachvderma and pointed out the synonymy of a number of others, including many references to Neogene and Holocene C. pseudoungeriana. Two ecophenotypes of this form were distinguished by Poag (1981): a thicker-walled bathyal type, C. ''floridanus" forma bathvalis, which refers to forms often referred to as C. floridanus: and a smaller thinner-walled outer neritic type, C. "floridanus" forma sublittoralis. which corresponds to forms that have

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been commonly called C. pseudoungerianus. We suggest retaining this "forma" terminology to distinguish the two ecophenotypes; forma bathvalis is figured in Plate 6.2, Figs. 1,2, 3, and forma sublittoralis is figured in Plate 6.2, Figs. 4, 5. Cibicides falconensis Renz may be an example of forma sublittoralis.

Cibicidoides sinistralis (Coryell and Rivero, 1940)

Plate 6.2, Figs. 6, 7, 8

Cibicides sinistralis Coryell and Rivero, 1940, p. 335, PI. 44, fig. 12; Galloway and Heminway, 1941, p. 396, PI. 24, fig. 5; Bermudez, 1949, p. 305, PI. 25, PI. 19-21. Cibicides umbonatus Phleger and Parker, 1951, p. 31, PI. 17, figs. 7-9; Parker, 1954, p.

543, PI. 12, figs. 17,18; Akers and Dorman, 1964, p. 31, PI. 17, figs. 7, 8 ; Kohl,

1985, p. 98, PI. 35, figs. 5, 6. Cibicides sp. cf. C. umbonatus (Phleger and Parker). Poag, 1981, p. 55, PI. 31, fig. 4, PI. 32, fig. 4.

Description.- Test free, trochospiral, biconvex, about three and one-half whorls, periphery acute with a narrow thickened keel; dorsal side covered by a transparent deposit of clear shell amterial, with distinct, thickened, flush, slightly oblique sutures; ventral sutures are slightly depressed, curved backward toward the periphery, may be sigmoid in larger specimens, meeting at an umbo of clear shell material; wall smooth, perforate, thin, transluscent; aperture interiomaiginal, equtorial, extending onto dorsal side, with slight lip. (after Coryell and Rivero, 1941; Phleger and Parker, 1951) Distribution.- This species is found in Recent and Neogene bathyal zone deposits of the Caribbean and Gulf of Mexico regions. We note C. sinistralis in the Trinchera Formation, which is comparable lithologically, environmentally, and biostratigraphically

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to the Port-au-Prince beds (=Rivi&re Grise Formation) located to the west in Haiti, from which this species was described. Remarks.- Cibicides umbonatus Phleger and Parker appears to be identical to C. sinistralis. Both forms are biconvex with a narrow thickened keel and have 9-12 chambers in the last whorl. The ventral sutures curve backward toward the periphery, and the dorsal sutures are distinct, thickened, and slightly oblique. Most diagnostic are the characteristic hyaline carbonate-filled umbilicus and transparent carbonate deposit over the dorsal spiral.

Superfamily PLANORBULINACEA Schwager, 1877 Family CEBICIDIDAE Cushman, 1927 Subfamily CIBICIDINAE Cushman, 1927 Genus CIBICIDES de Montfort, 1808

Cibicides cicatricosus (Schwager, 1866) Plate 6.3, Figs. 9,10

Anomalina cicatricosa Schwager, 1866, p. 260, PI. 7, figs. 4,108.

Truncatulina akneriana Brady (non d'Orbigny), 1884, PI. 94, fig. 8 . Cibicides cicatricosus (Schwager, 1866), Thalmann, 1932, p.309. Cibicides azuanas Bermudez, 1949, p. 294, PI. 24, figs. 40-42. Cibicidoides cicatricosus (Schwager, 1866), van Morkhoven, Berggren, and Edwards, 1985, p. 53, PL 16.

Description.- Test free, medium, slightly trochospiral, tightly coiled, 10-12 chambers in the last whorl; dorsal side slightly concave, ventral side overall slightly convex but

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somewhat depressed in the umbilical region, periphery broadly rounded; sutures thick, limbate in early portion of test, fusing to obscure the central area, distinct and depressed in later portion; both sides of test densely and coarsely perforate; aperture extending on both side of test, on the dorsal side with a distinct lip. (after van Morkhoven et al., 1985; and Srinivasan and Sharma, 1980) Distribution.- We have noted this species in the middle Miocene of the Sombrerito Formation and the lower Pliocene of the Trinchera Formation. It is widely distributed in Recent deep-sea samples. Remarks.- C. azuanus was described by Bermudez from the Sombrerito Formation and was characterized as "more compressed and more ornamented" than C. cicatricosus. However, we find this form to be identical to C. cicatricosus figured by van Morkhoven et al. (1985) from the middle Miocene of the Gulf of Mexico.

Superfamily NONIONACEA Schultze, 1854 Family NONIONIDAE Schultze, 1854 Subfamily PULLENIINAE Schwager, 1877 Genus MELONIS de Montfort, 1808

Melonis affinis (Reuss. 1851) Plate 6.2, Fig. 11, 12

Nonionina affinis Reuss, 1851, p. 72, PI. 5, figs. 32a, b.

?Nonionina barleeana Williamson. 1858, p. 32, PI. 3, figs. 68, 69.

Nonionina formosa Seguenza, 1880, p. 63, PI. 7, fig. 6. Nonion barleeanum (Williamson). Cushman, 1930, p. 11, PI. 4, fig. 5. Nonion planatum Cushman and Thomas, 1930, p. 37, PI. 3, fig. 5.

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Nonion nicobarense Cushman, 1936, p. 67, PI. 12, fig. 9; Galloway and Heminway 1941, p. 357, PI. 10, fig. 1; Palmer, 1945, p. 42; Bermudez, 1949, p. 166, PI. 11, fig.

20.

Nonion affine (Reuss). Renz, 1948, p. 148, PI. 6, figs. 3a, b; Smith, 1964, p. 41, PI. 4, figs. la, b; Boltovskoy, 1958, p. 195. Nonion cf. barleeanum (Williamson). Parker, 1948, p. 224, PI. 3, fig. 3. Nonion cf. pompilioides (Fichtel and Moll). Phleger and Parker, 1951, PI. 5, fig. 20. Nonion parkerae Uchio, 1960, p. 60, PI. 4, figs. 9,10.

Gavelnonion barleeanum (Williamson). Barker, 1960, p. 224, PI. 109, fig. 8, 9.

"Nonion" barleeanus (Williamson). Andersen, 1961, p. 82, PI. 18, fig. 6a, b. Melonis affinis (Reuss). Belford, 1966, p. 184, PI. 31, figs. 1-4; Kohl, 1985, p. 100, PI. 36, fig. 4.

Melonis barleeanus (Williamson). Wantland, 1967, p. 244, PI. 16, fig. 8 ; Wantland, 1975,

p. 398. Pflum and Frerichs, 1976, p. 28, PI. 7, figs. 5, 6.

Description.- Test free, planispiral, involute, equally compressed, diameter generally twice

that of width, 10-11 slightly curved chambers in the last whorl, rounded peripheral margin; sutures limbate, of variable width, generally wider near the umbilicus where they meet to form a circle of varying size around a distinct umbilical cavity; wall densely and coarsely perforate; aperture interiomarginal, equatorial crescent with an indistinct enlargement in the central pait of the base of the apertural face, extending on both sides as a fissure along the basal line, (after Boltovskoy, 1958) Distribution.- We have found this cosmopolitan species in the Trinchera and Quita Coraza Formations, primarily upper bathyal-outer neritic deposits. Remarks.- Boltovskoy (1958) proposed a lengthy (but also admittedly cautious) synonymy for Nonion affine C=M. affinis-). including some forms referred to as N. barleeana. Other

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forms referred to as N. barleeana (his "second list of synonyms") were separated from N. affine (as possible subspecies) based on greater thickness of sutures and coarser, less dense perforation. Boltovskoy was not able to examine original or topotype material of N. barleeana. however, and did not include it in synonymy with N. affine.

N0rvang (1959) proposed that most of the above listed forms should be placed in Nonion pompilioides (Fichtel and Moll). However, Andersen (1961) considered N. barleeanum (Williamson) to be a flatter form than N. pompilioides (Fichtel and Moll). We also consider the flatter Melonis species to be distinct from the stouter forms of the M. pompilioides - M. soldanii complex (=Boltovskoy's "first list of synonyms"; see van Morkhoven et al., 1985, for a discussion of this complex). We follow Boltovskoy's synonymy of M. affinis for the flatter forms, and also include in synonymy his "second list of synonyms."

Genus PULLENIA Parker and Jones, 1862

Pullenia subcarinata (d'Orbigny, 1839) Plate 6.2, Fig. 13,14

Nonionina subcarinata d'Orbigny, 1839, p. 28, PI. 5, figs. 23, 24. Nonionina quinqueloba Reuss, 1851, p. 71, PI. 5, fig. 31a, b.

Pullenia compressiuscula Reuss var. quadriloba Reuss, 1867, p. 87, PI. 3, fig. 8. Pullenia compressiuscula Reuss var. quinqueloba Reuss, 1867, p. 87. Nonionina quatriloba Sequenza, 1880, p. 430, PI. 17, fig. 15. Pullenia quinqueloba (Reuss). Brady, 1884, p. 617, PI. 84, figs. 14,15; Cushman and

Todd, 1943, p. 10, PI. 2, fig. 5. PI. 3, fig. 8 ; Phleger and Parker, 1951, p. 29, PI. 15,

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figs. 12, 13; Becker and Dusenbury, 1958, p. 27, PI. 6, figs. 3a, b; Kohl, 1985, p. 93,

PI. 32, fig. 6.

Pullenia subcarinata (d'Orbigny). Heron -Allen and Earland, 1932, p. 402, PI. 13, fig. 8 ; Barker, 1960, p. 174, PI. 84, figs. 14,15; Andersen, 1961, p. 115, PI. 25, figs. 9a, b. Pullenia quadriloba Reuss. Cushman and Todd, 1943, p. 15, PI. 2, figs. 20,21.

Description.- Test free, planispiral, involute, compressed, periphery rounded to subrounded and slightly lobulate, last whorl consisting of 4-6 inflated chambers which gradually increase in size as added; sutures distinct, narrow, slightly depressed, radial, slightly curving toward periphery; wall smooth, without conspicuous perforations; aperture interiomarginal, equatorial crescent extending to the umbilicus on either side, with a distinct lip. Distribution.- This species is present as a rare component of the Trinchera Formation fauna. It is a cosmopolitan Recent and Neogene form. Remarks.- Heron-Alien and Earland (1932) placed P. quinqueloba (Reuss) in synonymy with P. subcarinata (d'Orbigny). Phleger and Parker (1951) considered P. quadriloba Cushman and Todd (sic) to be a synonym of P. quinqueloba.

Superfamily CHILOSTOMELLACEA Brady, 1881 Family GAVELINELLIDAE Hofker, 1956 Subfamily GAVELINELLINAE Hofker, 1956 Genus GYROIDINA d'Orbigny, 1826

Gvroidina laevis d'Orbigny, 1826 Plate 6.2, Fig. 15,16

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Gvroidina laevis d'Orbigny, 1826, p. 278, no. 3; Parker, Jones and Brady, 1871, PI. 12, fig. 150; Fomasini, 1898, p. 260, fig. 7; Coryell and Rivero, 1940, p. 336, PI. 43,

figs. 2 0 , 28. Gvroidina orbicularis d'Orbigny. Parker, 1948, PI. 4, fig. 13; Phleger and Parker, 1951, p. 22, PI. 11, figs. 11,12; Parker, 1954, p. 543, PI. 9, figs. 13-18. Gvroidina cibaoensis Bermudez. 1949, p. 252, PI. 17, figs. 61-63. ?Gvroidina io Resig, 1958, p. 304, text-fig. 15a-c.

•v

Description.- Test free, trochospiral, inequally biconvex, about 10 chambers in the last whorl, peripherty subrounded; dorsal side nearly flat with flush, narrow, slightly oblique chamber sutures that curve toward the periphery, spiral suture flush, may be slightly channeled in larger specimens; ventral side convex, sutures narrow, flush, curving slightly toward the periphery, with a very small, shallow umbilicus; wall thick, very smooth, polished, and bright without conspicuous perforations; aperture elongate slit at base of final chamber. Distribution.- Occurrence of this species has been noted in several areas of Hispaniola. It is an uncommon constituent of upper Miocene and lower Pliocene Trinchera Formation deposits in the Azua Basin. In the Pliocene of southern Haiti, it has been recorded as Si laevis. and in the Pliocene of the Cibao Valley of the Dominican Republic as Si cibaoensis. It has been noted in the Recent of the North Atantic (Parker, 1948) and the Gulf of Mexico (Phleger and Parker, 1951; Parker, 1954) as G. orbicularis. Remarks.- As noted by Phleger and Parker (1951), since there is no type description or figure for G. orbicularis d'Orbigny, it is difficult to make a certain comparison to figures of d'Orbigny's model. The same case holds true for Gvroidina laevis d'Orbigny, which appears to have been confused with G. orbicularis by some authors. After making comparisons to some of the earlier figures of both G. laevis and G. orbicularis, we

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believe that the form we see in the Trinchera Formation should be assigned to G. laevis. This form exhibits a characteristic smoothly finished surface, rounded peripheral margin, slightly oblique and slightly curved sutures, and fewer and wider whorls. Coryell and Rivero (1940) recognized this form as G. laevis in the Pliocene of Haiti. We believe that the figures referred to G. orbicularis in Parker (1948), Phleger and Parker (1951) and Parker (1954) depict G. laevis. as do the type figures of G. cibaoensis Bermudez. Gvroidina io Resig also is very similar in appearance. Recognizing the difficulty in comparing our forms to a species for which there is no type figure or description, it is possible that it may be better referred to by Bermudez’s name. However, for the present we prefer to use d'Orbigny's name. In any case, the holotypes of G. cibaoensis are identical to forms referred to as G. orbicularis from the northwestern Gulf of Mexico. Other references to G. orbicularis are found in Brady (1884), Cushman (1914), and Kohl (1985). These forms have more and narrower whorls, a distinctly furrowed spiral suture, a more acute peripheral margin, and more distinctly oblique but less curved dorsal chamber sutures. We believe that these probably represent the true G. orbicularis. The species figured by Phleger, Parker, and Peirson (1953) as G. orbicularis appears to be different than G. laevis and G. orbicularis. Gvroidinoides planulata Cushman and Renz may be a related form but is flatter and has a wide umbilicus.

Gvroidina umbonata (Silvestri. 1898) Plate 6.2, Fig. 17,18,19

Rotalia soldanii (d'Orbigny) var. umbonata Silvestri, 1898, p. 239, PI. 6, figs. 14a-c. Gvroidina parva Cushman and Renz, 1941, p. 23, PI. 4, figs. 2a-c.

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Gvroidina narva Cushman and Renz var. oraniestadensis Drooger, 1953, p. 137, PI. 22,

fig- 4. Gvroidina umbonata (Silvestri). AGIP Mineraria, 1957, p. 49, fig. 3; Kohl, 1985, p. 94, PI. 33, fig. 3. Gvroidina sp. A Todd and BrOnnimann, 1957, p. 37, PI. 11, figs. 5a-c. Gvroidina cf. neosoldanii Brotzen. Drooger and Kaasschieter, 1958, p. 48, PI. 3, figs. 2a- c.

Description.- "Test free, small, trochospiral, biconvex, spiral side slightly convex, umbilical side strongly convex, circular in outline with broadly rounded periphery; chambers inflated, five to six in the last whorl, gradually increasing in size as added; sutures distinct, depressed, oblique on the spiral side, radial on the umbilical side; wall smooth, calacreous, hyaline, finely perforate; aperture an interiomarginal slit extending from a depression in the apertural face near the periphery to the umbilicus, with a distinct lip." (Kohl, 1985) Distribution.- This species has been found in the Neogene and Holocene of the Caribbean region and in the Neogene of the Mediterranean. We have noted it in upper Miocene and lower Pliocene samples from the upper part of the Trinchera Formation, the Quita Coraza Formation, and the Arroyo Blanco Formation. Remarks.- Our specimens from the Azua Basin share with the other forms the characteristic rounded periphery, inflated chambers, and depressed sutures of G. umbonata. We also note a thinner shelled form with more inflated chambers and a slightly looser coil that we refer to as G. sp. cf. G. umbonata.

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ACKNOWLEDGMENTS

cooperation in undertaking this study. The assistance of the Direcci 6n General de Minerfa, Dominican Republic, is gratefully acknowledged, with special thanks to I. Tavares and E. Garcfa of the Departmento de Geologfa.

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REFERENCES

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Bock, W. D., 1971. A handbook of benthonic foraminifera of Florida Bay and adjacent waters in Jones, J. I., and Bock, W.D., (eds.), A symposium of Recent South Florida foraminifera. Miami Geological Society Memoir No. 1,72 p., 1 map. 1 tab., 24 Pis..

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------, and Parker, F.L., 1940. The species of the genus Bulimina having Recent types. Contributions from the Cushman Laboratory for Foraminiferal Research, v. 16, no. 1, p. 7-23, Pis. 2, 3.

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, 1943. The genus Pullenia and its species. Contributions to the Cushman Laboratory for Foraminiferal Research, v. 19, p. 1-23,3 pis.

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12 pis..

------s 1948. Foraminifera from the Red Bluff - Yazoo section at Red Bluff (Hiwanee), Mississippi. Contributions to the Cushman Laboratory for Foraminiferal Research, v. 24, p 1-12.

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Douglas, R.G., and Woodruff, F., 1981. Deep-sea benthic foraminifera in Emiliani, C., ed., The Oceanic Lithosphere, The Sea, v. 7,1233-1327. John Wiley and Sons, New York.

Drooger, C.W., and Kaasschieter, J.P.H., 1958. Foraminifera of the Orinoco- Trinidad-Paria shelf. Reports of the Orinoco shelf expedition, v. 4. Veihandelingen der Koninklijke Nederlandse Akademie van Wetenschappen, Afdeling Natuurkunde, ser. 1, v. 22, no. 1, p. 1-108, text-figs. 1-4, maps 1-41, pi. 1-5.

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Fomasini, C., 1898. Contribute alia conosceza della microfauna terziaria italiana - Formainiferi del Pliocene superiors di San Pedro in Lama Presso Lecce. Reale Accademia Sciencia Institute Bologna, Memorias ScienciaNaturali, ser. 5, v. 7, p.

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Galloway, J.J., and Morrey, M., 1929. A lower Tertiary foraminiferal fauna from Manta, Ecuador. Bulletins of American Paleontology, v. 15, no. 55, p. 7-56, Pis.,

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Hedberg, H.D., 1937. Foraminifera of the middle Tertiary Carapita Formation of

northeastern Venezuela. Journal of Paleontology, v. 11, no. 8 , p. 661-697, fig. 1, tabs. 1, 2, pis. 90-92.

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Husezima, R., and Maruhasi, M., 1944. A new genus and thirteen new species of foraminifera from the core-sample of Kasiwazaki oil-field, Niigata-ken. Sigenkagaku Kenkyusyo, Journal, v. 1, no. 3, p. 391-400, PI. 34.

Keijzer, F.G., 1945. Outline of the geology of theeastem part of the province of Oriente, Cuba (E of 76° W longitiude), with notes on the geology of other parts of

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the island. Utrecht University, Geographische en Geologische Mededeelingen,

Physiographisc-Geologische, ser. 2, no. 6, 334 pp., 11 pis., 1 map, 19 tabs..

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McLaughlin, P.P., 1989. Neogene planktonic foraminiferal biostratigraphy of the southwestern Dominican Republic. Journal of Foraminiferal Research (in press).

McLaughlin, P.P., and Bold, W.A. van den, in review. Geology of the Enriquillo- Azua Basins, 2: Depositional History - Foraminiferal and Ostracode evidence m Mann, P., Draper, G., and Lewis, J., eds, Geologic and tectonic studies in Hispaniola: GSA Special Paper.

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Nuttall, W.L.F., 1928. Tertiary foraminifera from the Naparima region of Trinidad (British West Indies). Quarterly Journal of the Royal Geological Society of London, v. 84, no. 1, p. 57-117, pis. 3-8.

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Paleontology, v. 6, no. 1, p. 3-35, pis. 1-9.

Orbigny, A. d', 1826. Tableaus mdthodique de la classe de Cdphalopodes. Annales des Sciences Naturelles, Paris, sdr. 1, v. 7, p. 96-314, pis. 10-17.

Palmer, D.K., 1941, Foraminifera of the upper oligocene Cojimar Formation of Cuba; Part ?. Sociedad Cubana de Historoia Natural, Memorias, La Habana, v. 15, pt. 5, p. 281-309, pis. 28-30.

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------and Bermudez, P.J., 1936a. Late Tertiary foraminifera from the Matanzas Bay region, Cuba. Sociedad Cubana de Historoia Natural, Memorias, La Habana, v. 9, no. 4, p. 237-258, pis. 20-22.

------and Bermudez, P.J., 1936b. An Oligocene foraminiferal fauna from Cuba. Sociedad Cubana de Historoia Natural, Memorias, La Habana, v. 10, p. 227-316, pis,. 13-20.

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------51954. Distribution of the foraminifera in the northeast Gulf of Mexico. Bulletin of the Museum of Comparative Zoology, Harvard University, v. Ill, no. 10, p. 453-588, figs. 1-9, tabs. 1-30, pis. 1-13.

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Phleger, F.B., and Parker, F.L., 1952. New names for northwestern Gulf of Mexico foraminifera. Contributions from the Cushman Foundation for Foraminiferal Research, v. 3, no. 1, p. 14.

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Phleger, F.B., Parker, F.L., and Peirson, J.F., 1953. North Atlantic Foraminifera. Swedish Deep Sea Expedition, 1947-1948, Reports, v. 7, no. 1, p. 1-122, PI. 1-

12, 26 text-figs..

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Falc6n, Venezuela. The Geological Society of America, Memoir No. 32,219pp., 15 figs., 19 tabs., 12 pis..

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------, 1867. Die fossile Fauna der Steinsalzlagerung von Wieliczkain Galizien. Kaiserliche Akademie Wissenschaft Wien - Narturwissen Classe, Sitzungber., Wien, Austria, v. 55, pt. 1, p. 17-182, text-figs. 1-8.

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Rzehak, A., 1886. Die Foraminiferenfauna der Neogenformation der Umgebung von Mahr.-Ostrau.. Naturforschender Verein Briinn, Verhandlungen, Briinn (Bmo), v. 24, p. 77-126, pi. 1.

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Thalmann, H.E., 1932. Nomenclaior (Urn- und Neubenennungen) zu den Tafeln 1 bis 115 in H.B. Brady's Werk Uber die Foraminiferen der Challenger-Expedidon, London, 1884. Eclogae geolische Helvetiae, v. 25, no. 2, p. 293-312.

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Woodruff, F., 1985. Changes in Miocene deep-sea benthic foraminiferal distribution in the Pacific Ocean: Relationship to paleoceanography. Geological Society of America Memoir, 163, p. 131-175.

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Woodruff, F., and Douglas, R.C., 1981. Response of deep-sea benthic foraminifera

to Miocene paleoclimatic events, DSDP site 289. Marine Micropaleontology, v. 6, p. 617-632, figs. 1-8, tabs. 1, 2.

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PLATE 6.1

1. Bulimina mexicana. RD131. xlOO 2, 3. Bulimina tessellata. 2. RD74a. xl50: 3. RD36. xl50 4, 5. Uvieerina carapitana. RD131.4. microsDheric form. xlOO; 5. meealospheric form, xlOO 6, 7. Aneuloeerina iamaicensis. DM13-4. x350 8 , 9, 10. Aneuloeerina selsevensis. 8 . RD19. x200: 9.10. RD117, x200 11, 12,13, Eoonides weddellensis. RD117. 11. ventral view. 12. dorsal view, 13. edee 14. view, 14. edge view, x350 15, 16, 17. Cibicidoides incrassatus. 15. RD131. dorsal view, x75:16,17, RD36. 16. edge view, 6. ventral view, x75 18, 19, 20. Cibicidoides mundulus. RD129.18. dorsal view. 19. edee view, 20. ventral view, xlOO

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PLATE 6.2

I, 2, 3. Cibicidoides pachvderma forma bathvalis. RD36.1. dorsal view, 2. edge view, 3. ventral view, xlOO 4, 5. Cibicidoides pachvderma forma sublittoralis. DM13-4.4. dorsal view, 5. ventral view, x200 6, 7, 8. Cibicidoides sinistralis. RD36. 6. dorsal view, 7. edge view, 8. ventral view, x75 9, 10. Cihicides cicatricosus. RD126. 9. dorsal view, 10. ventral view, xlOO II, 12. Melonis affinis. RD74a. 15. edge view, 16. side view, xl50 13, 14. Pullenia subcarinata. RD66.13. egde view, 14. side view, x200 15, 16. Gvroidina laevis. RD76.15. dorsal view, 20. ventral view, xlOO 17, 18, 19. Gvroidina umbonata. RD76.17. ventral view, 18. edge view, 19. dorsal view, x200

CONCLUSIONS

289

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1) The Neogene marine sedimentary record of the Azua Basin is represented by a dominantly clastic, 4000 m thick regressive interval which includes 4 formations, in ascending order: the Sombrerito Formation; the Trinchera Formation; Quita Coraza Formation; and Arroyo Blanco Formation. The sedimentary facies reflect shallowing upward, from pelagic carbonates through volcanic lithic- and feldspar-rich turbidites to coastal deltaic coarse clastics.The Sombrerito Formation is characterized by soft, buff pelagic limestones and marls that occur in scattered outcrops. The Gajo Largo Member of the Sombrerito comprises the upper 200 m of the unit in the southern part of the basin and includes a significant volume of rhythmically-bedded, shallow-marine carbonate sediment gravity flow deposits. The Trinchera Formation is characterized by a thick sequence (1300 - 2200 m) of interbedded deep-marine mudstones and dirty turbidite sandstones and is generally well exposed in continuous sections. An upward trend from outer turbidite fan facies in the lower part of the formation to inner fan facies in the upper part is evident throughout the basin. In the southern part of the basin, 300-700m of shallow-marine siltstones and mudstones comprise the Quita Coraza Formation. This unit is absent in the northern arm of the basin, where the Trinchera Formation continues directly into the Arroyo Blanco Formation. The Arroyo Blanco Formation is a predominantly clastic unit dominated by nearshore and non-marine sediments. It apparently represents a coastal deltaic complex that produced a thick (1000 m) coarsening-upward sequence composed of many fining-upward cycles. In the southern part of the basin, scattered coral beds and small reefs occur near its base and gypsum is present in its upper strata; in the northwestern part of the basin, the Arroyo Blanco is much more conglomeratic, reflecting greater proximity to the Cordillera Central source.

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2) Planktonic foraminifera indicate that the marine sequence in the Azua Basin ranges in age from early Miocene to middle Pliocene. These ages are younger than reported in most previous studies, which lacked detailed information on planktonic foraminifera. Sombrerito Formation - Lower Miocene (Globigerinatella insueta chronozone, about N7) near San Juan de la Maguana to middle Miocene at the type locality (Globorotalia fohsi fohsi chronozone, about N10) and at Canoa Dome (G. fohsi robusta chronozone, about N12); upper part of the middle Miocene (Globorotalia maveri chronozone, about N14) to the lowest part of the upper Miocene (equivalent to lower part of Globorotalia acostaensis zone, about lower N16) in the Gajo Largo member near Canoa. Trinchera Formation - In the Rfo San Juan and upper Rfo Yaque del Sur Valleys, middle Miocene (Globorotralia menardii chronozone, about N15) or lowest part of the upper Miocene (lower Globorotalia acostaensis chronozone, about lower N16) in the lower part of the section at Arroyo Salado, to uppermost Miocene (upper Globorotalia humerosa chronozone, about N17) at the top of the formation at Arroyo Las Lajitas; in the lower Rio Yaque del Sur Valley, upper Miocene (upper Globorotalia humerosa chronozone, about upper N17) to lower Pliocene (equivalent to Globorotalia margaritae marearitae subzone, about N18) in the Fondo Negro highway section; in the Azua Region, uppermost Miocene (upper Globorotalia humerosa chronozone, about upper N17). Quita Coraza Formation - In the lower Rio Yaque del Sur Valley, lower Pliocene (equivalent to Globorotalia margaritae margaritae subzone, about N18, and possibly G. m. evoluta subzone, about N19); in the Azua Region, uppermost Miocene (upper Globorotalia humerosa chronozone, about upper N17) or possibly lower Pliocene (Globorotalia margaritae chronozone, about N18 and N19). Arroyo Blanco Formation - In the Rio San Juan and upper Rio Yaque del Sur Valleys, uppermost Miocene (upper Globorotalia humerosa chronozone, about upper N17) and above; in the lower Rio Yaque del Sur Valley, lower Pliocene (Globorotalia margaritae

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chronozone, about N18 and/or N19) and younger; in the Azua Region, uppermost Miocene (upper Globorotalia humerosa chronozone, about upper N17) or lower Pliocene (Globorotalia margaritae chronozone, about N18 and/or N19) and above.

3) The biostratigraphy demonstrates a southeastward time-transgression of lithostratigraphic boundaries. The upper part of the Sombrerito at its type locality in the upper Rfo Yaque del Sur Valley is of lower middle Miocene age, whereas the upper part of the Sombrerito in the lower Rfo Yaque del Sur Valley is middle middle Miocene in age. The Trinchera - Arroyo Blanco contact in the Rfo San Juan and upper Rfo Yaque del Sur Valleys is of late Miocene age, but in the lower Rfo Yaque del Sur Valley the top of the Trinchera and the bottom of the Arroyo Blanco are of early Pliocene age.

4) An overall upward decrease in diversity is evident in the Azua Basin sedimentary sequence. Species richness, S, ranges between 177, in mixed faunas in the Sombrerito Formation, to as low as 29, in the Arroyo Blanco Formation. The Shannon-Wiener Information Function, H(S) diminishes from a high of 4.71 in the Sombrerito to below 2.0 in the Arroyo Blanco Formation. This trend of decreasing diversity is consistent with shoaling upsection.

5) In splits of 54 samples from the Azua Basin, 167 species or varieties of benthic foraminifera were identified at the 1% abundance level. Six factors were selected in a Principal Components Analysis (with VARIMAX rotation) of the 53 species with the greatest variance in this set. Factor 1 is the shelf-edge factor, with positive loadings of Bolivina minima. Cassidulina norcrossi var. australis, and Gvroidina regularis. and negative loadings of deep-bathyal species Cibicides wuellerstorfi. Pleurostomella altemans. and Bolivina paula. Factor 2 is the middle to upper bathyal factor, with positive loadings of

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Recurvoides trincherasensis. Oridorsalis umbonatus. Hoeglundina elegans. and Sigmoilopsis schlumbergeri. Factor 3 is the middle to outer neritic factor, species including Angulogerina iamaicensis. Cassidulina subglobosa. Cassidulina carinata. Reussella spinulosa have positive loadings. Inner neritic species including Havnesina depressula. Buliminella elegantissima. and Rosalinaconcinna load strongly on Factor 4. Cancris sagra. Bolivina lowmani. and Gavelinopsis sp. A have positive loadings on Factor 5, which can be charcterized as a neritic factor. Factor 6 appears to reflect a current-winnowed upper bathyal or outer neritic fauna, with large, robust specimens of Uvigerina viaensis and Bolivina obscuranta being most characteristic.

6) The shifts of the factor scores upsection reflect steady shoaling between the lower Miocene and middle Pliocene. Negative scores on Factor 1 in die Sombrerito Formation and the lower part of the Trinchera Formation reflect the dominance of lower to middle bathyal assemblages. From the middle to the upper parts of the Trinchera, a shift from middle to upper bathyal assemblages (Factor 2) to shelf-edge assemblages (Factor 1) is evident. The dominance of shallow-marine assemblages in the Quita Coraza and Arroyo Blanco Formations is reflected in the high positive scores of Factors 3,4, and 5; Factor 3 scores strongly in the Quita Coraza Formation, Factor 4 is most important in the Arroyo Blanco Formation and Factor 5 scores heavily in the higher Arroyo Blanco strata.

7) Paleoenvironments migrate southeastwaidly through time in the Azua Basin. In the middle of the middle Miocene and earlier, all of the southwestern Dominican Republic appears to have been at lower bathyal depths and greater. Middle bathyal faunas first appeared in the later part of the middle Miocene at the northwestemmost end of the Azua Basin and migrated to the open southern end of the basin in the late Miocene. This same path was followed by the upper bathyal faunas in the late Miocene. By the early Pliocene,

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bathyal faunas were restricted to the southern part of the basin, with shallow- and marginal- marine environments advancing from the north through the Pliocene This is supported by factor scores in the sections that, in any one time plane, indicate the occurence of deeper water faunas seaward of the northwestern end of the basin.

8) Cluster analysis of species percentage data from die Azua Basin samples resolves groups that correspond very closely to the faunal zones of Bermudez (1949).Cluster 1 is dominated by samples from the Sombrerito Formation and corresponds closely to Bermudez's Sombrerito assemblage. Cluster 2 is composed mostly of samples from the lower part of the Trinchera Formation and is comparable to the Basal Gaspar Zone. The samples in Cluster 3 contains assemblages that fit into the Gaspar Zone, mostly from the middle part of the Trinchera Formation. Clusters 4 and 5 correspond to the Bao Zone; Cluster 4 is mostly Quita Coraza samples, and Cluster 5 is predominantly Trinchera. Cluster 6 is a group of samples from the lower part of the Arroyo Blanco Formation. Cluster 7 is comparable to the Quita Coraza Zone, with samples from the Quita Coraza Formation and, less commonly, from the Arroyo Blanco.

9) Our study reveals that a number of Neogene and Recent species described under separate names are synonymous. The proliferation of taxonomic names used for these forms has prevented full understanding of the paleoecologic and biostratigraphic significance of Neogene benthic foraminifera as well as resulting in the entrenchment of junior synonyms in the literature. In several cases encountered in the study of the taxonomy of the Azua Basin fauna, we have noted that more obscure species names originally applied to Neogene taxa of the Caribbean - Gulf of Mexico region are senior synonyms of more well-known species described from the Recent; in others, we have proposed solutions to a maze of nomenclature applied to similar forms. New synonymies for 7 species are

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proposed: Angulogerina iamaicensis. Angulogerina selsevensis. Bulimina tessellata. Cibicides cicatricosus. Eponides weddellensis. Gvroidina laevis. and Uvigerina carapitana. In addition, we discuss these benthic species in light of recent planktonic foraminiferal biostratigraphy in the basin (McLaughlin, 1989).

10) Integration of the paleontologic and sedimentologic data suggests that regional tectonics were the main control on the Neogene basin history of southern Hispaniola. The Azua Basin appears to have evolved in two stages: a pre-late Miocene open-ocean stage; and a late Miocene and younger laterally-confined clastic basin stage. The open ocean stage includes late-early and early-middle Miocene age deep-marine pelagic deposits of the Sombrerito Formation deposited off a Hispaniola slope open to the Caribbean Sea. The lack of siliciclastic erosion products from the Cordillera Central suggests low relief of the core of the island and implies relative tectonic stability of Hispaniola during the first half of the Miocene. By the late Miocene, several striking changes had taken place: the onset of rapid siliciclastic sedimentation with a source in the Cordillera Central; an increase in subsidence rates; and the apparent rise of a barrier on the south side of the Azua Basin. The initiation of siliciclastic sedimentation in the Azua Basin is reflected in the sedimentology of the Trinchera Formation, a unit of mud-rich, lithic- and feldspar-rich sandstones deposited by turbidity currents at bathyal depths. Laterally, occurrences of this unit are confined to a narrow, elongate valley that opens out into the Caribbean Sea, bounded on both sides by thrust blocks. The northern block, the Cordillera Central, contains igneous, metamorphic, and sedimentary rocks of an ancient island arc of Cretaceous and Paleogene age which apparently was in existence prior to Trinchera deposition. The southern block, the Sierra de Neiba, is composed of pelagic limestones of Paleogene to middle-middle Miocene age. Sole marks in the Trinchera indicate basin-axis parallel paleocurrents in the northwest end

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of the basin, suggesting that the Sierra de Neiba acted as a barrier on the southwest side of the basin, deflecting sediment flowing southwestwaid from the Cordillera Central into a southeasterly oriented sedimentary trough. The orientation of the paleocurrents appear to be southward and southwestward in the Fondo Negro area, suggesting that the basin opend up into the Caribbean there and the turbidity currents lost their lateral containment. From this, it appears that the Trinchera Formation was deposited by a narrow, prograding submarine fan that advanced southeastward across Azua Basin through the late Miocene into the early Pliocene, filling the basin behind it The sediment influx was probably a response to initiation of rapid uplift in the Cordillera Central to the north; the compositional trends in these sandstones show strong relationships to the rocks exposed along the southern margin of these mountains. The shallow marine-fluvial deltaic complex of the Arroyo Blanco Formation was lain down between the late Miocene and the middle Pliocene, advancing seaward behind the same turbidite fan it fed. Paleocurrents mostly indicate southeastward sediment transport, consistent with the basin axis. In the early Pliocene in the lower Rfo Yaque del Sur Valley, neritic siltstones of the Quita Coraza Formation occur between the Trinchera and Arroyo Blanco Formations. These siltstones may reflect deposition on the shelf between feeder channels that carried coarse elastics from the coastal-deltaic complex to the deeper turbidite wedge. The low input of coarse elastics in the Quita Coraza Formation may also be influenced by isolation of sediment on the shelf during the early Pliocene highstand (Haq et al., 1987). The microfauna, however, indicates continuous upward shoaling in the late Miocene and early Pliocene, suggesting that the rate of sediment accumulation was more rapid than any relative sea level rise. Uplift of the Cordillera Central and Sierra de Neiba fold-thrust belts apparently provided the load needed to drive isostatic subsidence of the floor of the Azua Basin

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through lithospheric flexure, as well as providing a sediment source. Petrographic analysis of sandstones in the Trinchera Formation indicates that the Cordillera Central was the primary source for the large influx of sediments (McLaughlin and Bold, in review).

11) A period of renewed tectonic activity along the Northern Caribbean Plate Boundary Zone appears to have commenced in the late Miocene. Mann et aL (1984) have proposed that the island of Hispaniola forms a Neogene "restraining bend" in the Northern Caribbean Plate Boundary Zone. The formation of the northwestward-trending anticlinal thrust block mountain belts and intervening synclinal basins that characterize Hispaniola appear to have begun toward the end of the middle Miocene through associated transpressional, wrench fault neotectonic activity. This is reflected in the change from the pre-late Miocene open ocean stage to the late Miocene to Recent laterally-constrained basin stage. We feel that this indicates initiation of transpressional neotectonics along the NCPBZ near the start of the late Miocene.

12) The foraminiferal biostratigraphy and paleoenvironments of the Azua Basin sequence can be compared to that of other sequences of the circum-Caribbean region. The establishment of a detailed biostratigraphic scheme for the Azua Basin allows correlation to formations in other Neogene sequences on Hispaniola and around the Caribbean: The Azua Basin faunas span a wide range of environments. Our survey of a number of other Caribbean Neogene assemblages demonstrate close relationships to those identified in our study and suggest that the Azua Basin fauna may serve as a most useful reference material in future paleoenvironmental investigations.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX 1 - Species identified in abundances of greater than 1% in at least one sample from the Azua Basin.

# = used in Principal Components Analysis * =present as <1% but environmentally significant Ammobaculites sp. Ammodiscus dominicensis Bermudez var. deformis Bermudez, 1949 Ammonia parkinsoniana (d'Orbigny) = Rotalia parkinsoniana d'Orbigny, 1839 # Amphistegina gibbosa d'Orbigny. 1839 Anguloeerina angulosa (Williamson) = Uvigerina aneulosa Williamson, 1858 Angulogerina carinata Cushman var. bradvana Cushman, 1932 Angulogerina eximia Cushman and Jarvis, 1936 Angulogerina guraboensis Bermudez, 1949 Angulogerina iamaicensis Cushman and Todd, 1945 # Angulogerina occidentals Cushman, 1923 Angulogerina selsevensis (Heron-Allen and Earland) = Uvigerina selsevensis Heron-Allen and Earland, 1909 = Angulogerina bella Phleger and Parker, 1951 Anomalina flintii Cushman. 1931 Anomalinoides sp. Asterigerina carinata d'Orbigny. 1839# Bermudezinella riveroi (Bermudez) = Pulleniariveroi Bermudez, 1949 # Bolivina alata (Seguenza) = Vulvulina alata Seguenza, 1862 # Bolivina albatrossi Cushman, 1922 # Bolivina arta Macfadyen, 1930 Bolivina bvramensis Cushman = Bolivina caelata Cushman var. bvramensis Cushman, 1923 Bolivina daggarius Phleger and Parker, 1951 Bolivina furcata Cushman and Jarvis, 1930 Bolivina goessi Cushman, 1922 Bolivina inflata Heron-Alien and Earland, 1913 # Bolivina lowmani Phleger and Parker, 1951 # Bolivina marginata Cushman var. multicostata Cushman = Bolivina aenariensis (Costa) var. multicostata. 1918 # Bolivina minima Phleger and Parker, 1951 # Bolivina obscuranta Cushman, 1936 # Bolivina paula Cushman and Cahill, 1932 # Bolivina pisciformis Galloway and Money, 1929 # Bolivina plicatella Cushman var. mera Cushman and Ponton, 1932 # Bolivina pygmaea H.B. Brady, 1884 Bolivina striatula Cushman var. spinata Cushman, 1936 Bolivina tectiformis Cushman, 1926 Bolivina sp. A # Bolivina sp. C Bolivina sp. D Bolivina sp. E Bolivina sp. G Bolivina sp. L # Bolivina sp. O # Bolivina sp. R Bolivina sp. S Bolivina sp. T Bolivina? sp. K # Buccella hannai (Phleger and Parker) = Eponides hannai Phleger and Parker, 1951

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Bulimina alazanensis Cushman, 1927 Bulimina mexicana Cushman= Bulimina inflata Seguenza var. mexicana Cushman, 1922 Bulimina socialis Bomemann. 1855 # Bulimina tessellata Cushman and Todd = Bulimina marginata d'Orbigny var. tessellata Cushman and Todd, 1945 Buliminella elegantissima (d'Orbigny) = Bulimina elegantissima d'Orbigny, 1839 # Burseolina palmerae (Bermudez and Acosta) = Cassidulina palmerae Bermudez and Acosta, 1940 Cancris saera (d'Orbigny) = Rotalia sagra d'Orbigny, 1839 # Cassidulina carinata Silvestri = Cassidulina laevigata d'Orbigny var. carinata Silvestri, 1896# Cassidulina crassa d'Orbigny, 1839 Cassidulina curvata Phleger and Parker, 1951 Cassidulina norcrossi Cushman var. australis Phleger and Parker = Cassidulina norcrossi australis Phleger and Parker, 1951 # Cassidulina reflexa Galloway and Wissler, 1927 Cassidulina subglobosa H.B. Brady, 1884 # Cassidulinoides bradvi (Norman) = Cassidulina bradvi Norman, 1880, in Wright, 1880 Cassidulinoides sp. A Chilostomella czizeki Reuss. 1850 Cibicides cicatricosus (Schwager) = Anomalina cicatricosa Schwager, 1866 Cibicides lobatulus (Walker and Jacob) = Nautilus lobatulus Walker and Jacob, 1798 # Cibicides wuellerstorfi (Schwager) = Anomalina wuellerstorfi Schwager, 1866 # Cibicidoides bradvi (Trauth) = Truncatulina bradvi Trauth, 1918 Cibicidoides corvelli (Bermudez) = Cibicides corvelli Bermddez,1949 Cibicidoides incrassatus (Fichtel and Moll) = Nautilus incrassatus Fichtel and Moll, 1798 Cibicidoides mundulus (Brady, Parker, and Jones) = Truncatulina mundula Brady, Parker, and Jones, 1888 Cibicidoides pachvderma (Rzehakl forma bathvalis Poag = Truncatulina pachvderma Rzehak, 1886 = Cibicidoides "floridanus" forma bathvalis Poag, 1981 # Cibicidoides pachvderma (Rzehak) forma sublittoralis Poag = Truncatulina pachvderma Rzehak, 1886 = Cibicidoides "floridanus" forma sublittoralis Poag, 1981 # Cibicidoides perforatus (Coryell and Rivero) = Cibicides perforatus Coryell and Rivero, 1940# Cibicidoides sinistralis (Coryell and Rivero) = Cibicides sinistralis Coryell and Rivero, 1940 Clavulina mexicana Cushman = Clavulina humilis Brady var. mexicana Cushman, 1922 Dentalina communis (d'Orbigny') = Nodosaria (Dentaline) communis d'Orbigny, 1826 Eggerella bradvi (Cushman) = Vemeuilina bradvi Cushman, 1911 Elphidium gunteri Cole forma salsum Poag, 1978 = Cribroelphidium salsum Cushman and Bronnimann, 1948 Elphidium lanieri (d’Orbigny) = Polvstomella lanieri d'Orbigny, 1839 Elphidium poevanum (d'Orbigny) = Polvstomella poevana d’Orbigny, 1839 Epistominella advena (Galloway and Morrey) = Rotalia advena Galloway and Morrey, 1929 Epistominella exigua (Brady) = Pulvinulina exigua Brady, 1884 Epistominella sp. P Epistominella sp. S Eponides weddellensis Earland, 1936 Fissurina alveolata H.B. Brady, 1884 Fissurina laevigata Reuss. 1850 Fursenkoina compressa (Bailey) = Bulimina compressa Bailey, 1851 Fursenkoina pontoni (Cushman) = Virgulina pontoni Cushman, 1932

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Gavelinopsis praegeri Heron-Alien and Earland, 1913 # Gavelinopsis transluscens Phleger and Parker, 1951 # Globobulimina paciflca Cushman, 1927 Gvroidina altiformis R.E. and K.C. Stewart, 1930 Gvroidina altispira Cushman and Stainforth, 1945 Gvroidina pirardana (Reuss) = Rotalina girardana Reusss, 1851 # Gvroidina laevis d'Orbigny. 1826 Gvroidina regularis (Phleger and Parker) = Eponides regularis Phleger and Parker, 1951 # Gvroidina trincherasensis Bermudez, 1949 Gvroidina umbonata (Silvestri, 1898) # Gvroidina sp. cf. G. umbonata # Hanzawaia isidroensis (Renz) = Cibicides isidroensis Renz, 1948 # Havnesina depressula (Walker and Jacob) var. matagordana = Nonion depressula (Walker and Jacob) var.matagordana Komfeld # Hoeelundina elegans (d'Orbigny) = Rotalia (Turbinulinal elegans d'Orbigny, 1826 # Karreriella bradvi (Cushman) = Gaudrvina bradvi Cushman, 1911 Laterostomella subspinescens = Bolivina subspinescens Cushman, 1922 Lenticulina americana (Cushman) = Cristellaria americana Cushman. 1918 Lenticulina dicamplva (Franzenau) = Cristellaria dicamplva Franzenau, 1894 Lenticulina intusvortex (Bermudez) = Robulus intusvortex Bermudez, 1949 Lenticulina sp. A Lenticulina sp. B Loxostonum gelbi Andersen. 1961 Martinotiella nodulosa (Cushman) = Clavulina communis H.B. Brady var. nodulosa Cushman, 1922 Melonis affinis (Reuss) = Nonionina affinis Reuss, 1851 # Nodosaria longiscata d’Orbigny. 1846 Nodosaria subtertenuata Schwager. 1866 Nonion sp. # Oolina globosa (Montagu) = Vermiculum globosum Montagu, 1833 Oridorsalis umbonatus (Reuss) = Rotalina umbonata Reuss, 1851 # Orthomorphina aminaensis (Bermudez) = Nodogenerina aminaensis Bermudez, 1949 Osangularia culter (Parker and Jones) = P kr orbulina farcta (Fichtel and Moll) var. ungeriana (d'Orbigny 1 subvar. culter Parker and Jones, 1865 Planulina renzi Cushman and Stainforth, 1945 * Planulina ariminensis d'Orbigny. 1826 Pleurostomella altemans Schwager, 1866 # Pleurostomella cubensis Cushman and Bermudez Pseudononion atlanticum (Cushman) = Nonionina atlantica Cushman, 1947 Pseudononion grateloupi (d'Orbigny) = Nonioina grateloupi d'Orbigny, 1826 Pullenia bulloides (d'Orbigny) = Nonionina bulloides d’Orbigny, 1826 Pullenia salisburvi Stewart and Stewart, 1930 Pullenia subcarinata (d'Orbigny) = Nonionina subcarinata d'Orbigny, 1839 Pvrgo murrhina (Schwager) = Biloculina murrhina Schwager, 1866 Ouinqueloculina mexicana Ouinqueloculina seminulina (Linn6) = Serpula seminulum Linn6,1785 Rectobolivina mexicana (Cushman) = Siphogenerina mexicana Cushman, 1926 Recurvoides trincherasensis Bermudez, 1949 # Reussella spinulosa (Reuss) = Vemeuilina spinulosa Reuss, 1850 # Rosalina concinna (H.B. Brady) = Discorbis concinna H.B. Brady, 1884 # Rosalina floridana (Cushman) = Discorbis floridanus Cushman, 1922 Sagrina nulchella d’Orbigny. 1839 Sigmavirgulina tortuosa (Brady) = Bolivina tortuosa H.B. Brady, 1884

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Sigmoilina tenuis (Czjzek) = Ouinqueloculina tenuis Czjzek, 1847 Sigmoilopsis schlumbergeri (A. Silvestri) = Sigmoilina schlumbergeri A. Silvestri, 1904 # Siphonina bradvana Cushman, 1927 Siphonina pozonensis Cushman and Renz, 1941 Siphonina pulchra Cushman, 1919 # Siphonodosaria lepidula (Schwager) Siphonodosaria nuttalli (Cushman and Jarvis) = Ellipsonodosaria nuttalli Cushman and Jarvis, 1934 Siphonodosaria nuttalli (Cushman and Jarvis) var. gracillima (Cushman and Jarvis) - Ellipsonodosaria nuttalli Cushman and Jarvis var. gracillima Cushman and Jarvis, 1934 Siphonodosaria paucistriata (Galloway and Morrey) = Nodosarella paucistriata Galloway and Morrey, 1929 * Sphaeroidina bulloides d'Orbigny. 1826 Stainforthia complanata (Egger) = Virgulina schreibersiana Czjzek var. complanata Egger, 1893 Stilostomella? granulifera Stilostomella? sp. A Textularia leuzingeri Cushman and Renz, 1941 Textularia mexicana Cushman, 1922 Textularia vaguatensis Bermudez, 1949 Textularia vasicaensis Bermudez. 1949 Trifarina bradvi Cushman, 1923 Uvigerina auberiana d'Orbigny. 1839 # Uvigerina azuana Bermudez, 1949 # Uvigerina carapitana Hedberg, 1937 Uvigerina ciperana Cushman and Stainforth, 1945 Uvigerina hispida Schwager, 1866 Uvigerina mantaensis Cushman and Edwards, 1938 Uvigerina parvula Cushman = Uvigerina peregrina Cushman var. parvula Cushman,1923 # Uvigerina peregrina Cushman, 1923 # Uvigerina pigmaea d'Orbigny. 1826# Uvigerina proboscidea Schwager, 1866 Uvigerina viaensis Bermudez, 1949 # Valvulineria floridana Cushman Valvulineria gasparensis Bermudez, 1949 Valvulineria mexicana Parker, 1954 #

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 303 22 RD 0.8 2.1 0.3 1.8 0.8 0.5 0.8 0.3 2.3 1.6 10.9 1.6 2.4 0.4 19 21 1.6 1.2 1.6 1.2 1.2 0.8 0.8 4.5 1.7 0.4 1.3 3.1 11.8 14 16 1.8 1.3 0.8 6.9 5.7 0.3 0.5 0.8 0.3 DM FD FD RD FD 0.7 10-1 4.8 DM 0.4 10-2 0.7 0.9 3.2 0.4 4.6 13 RD 1.2 7.3 0.4 0.8 1.4 0.8 0.7 0.3 1.6 10.8 12 2.2 2.25.44.74.8 0.4 0.4 3.7 9 0.6 0.4 0.3 0.6 4.5 0.4 1.0 0.3 0.4 4.3 0.7 2.5 0.4 1.4 3.2 11.2 2 7 FL FD FD RD 0.3 0.3 0.3 0.3 4.9 10.8 1.9 0.4 13.7 12.7 12.7 14.0 1 1.7 1.0 0.7 1.0 0.3 2.3 8.0 1.0 1.3 7.0 AW FL 1.6 6.3 4.2 0.6 1.1 0.3 1.3 0.3 2.3 0.3 7.8 3.2 0.6 1.1 3.1 7.5 0.33.0 1.5 0.32.0 6.2 0.3 3.35.7 1.0 0.4 RD 125 1 2.8 1.1 0.7 0.8 0.2 0.9 0.3 1.0 0.4 1.7 0.9 0.9 5.3 2.2 17 5.8 0.4 0.4 2.7 0.4 0.4 0.4 0.8 1.6 2.3 0.4 0.4 1.3 1.6 DM DMR 0.3 0.4 0.3 1.7 1.1 25.2 139 2-8 0.6 0.3 2.4 2.3 3.0 3.3 1.7 25.7 32.4 18.1 DM FD 2-1 1.1 1.8 1.5 0.3 1.8 0.4 0.3 0.3 8.7 4.0 2.4 4.2 29.5 NUMBERS SAMPLE Ammobaculites sp. Ammodiscus dominicensis var. deformis Ammonia parkinsoniana Amphisteqina qibbosa Anquloqerina anqulosa Anquloqerina carinata var.Anquloqerina bradyana eximia Anquloqerina quraboensisAnquloqerina iamaicensis Anomalinaflintii Anquloqerina selsevensis Anquloqerina occidentalis Bolivina alata Anomalinoides sp. Asteriqerina carinata Bermudezinella riveroi Bolivina albatrossi Bolivina byramensis Bolivina arta Bolivina daqqaria Bolivina furcata Bolivina inflata Bolivina qoessi Bolivina lowmani Bolivina minima Bolivina marqinata var. multicostata Bolivina obscuranta Bolivina pisciformis Bolivinapaula Bolivina pyqm aea Bolivina plicatella var. m era Bolivina tectiformis Bolivina striatula var. soinata Bolivina sp. A Bolivina sp. C

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 304 0.5 0.3 0.3 39.0 24.9 RD RD RD 1.2 1.2 1.3 3.7 8.3 1.6 6.9 16 19 21 22 0.4 0.8 0.3 0.9 1.3 1.6 0.8 6.1 4.4 2.0 0.3 2.6 2.2 14 0.3 0.8 1.3 1.0 7.3 1.3 10-1 2.8 0.3 0.3 6.9 i DM DM RD RD 0.4 3.2 10-2 4.0 0.4 7.6 3.2 5.9 5.3 4.6 1.4 3.1 2.3 0.4 3.8 8.9 1.1 0.4 1.9 1.4 1.5 4.4 8.1 1.5 3 .0 12.7 4.5 0.3 0.4 0.6 0.4 11.9 1.8 0.6 1.9 3.2 3.4 5.6 1.2 2.5 3.3 2.5 0.6 0.7 1 2 7 9 12 13 2.0 1.6 0.4 1.0 0.4 0.8 5.3 5.2 2.0 1.0 0.6 0.4 2.2 1.7 4.8 1.7 2.7 1 1.6 1.3 2.2 18.4 1.9 3.1 0.3 RD AW FL FL RD RD RD RD 1.7 0.2 0.6 1.1 0.9 0.6 5.6 0.2 2.8 0.4 0.4 1.2 2.2 1.6 0.9 2.3 1.6 1.3 4.0 3.3 3.3 0.4 2.0 1.2 6.5 1.2 2.2 0.4 1.3 3.3 2-8 17 125 0.3 0.4 0.2 0.3 0.3 0.8 0.8 0.8 0.3 1.0 0.4 1.4 1.1 0.3 5.8 1.6 0.3 0.3 FD DM DMR 139 1.8 1.0 1.0 0.3 3.9 DM 2-1 0.4 0.4 0.4 1.1 0.4 0.3 0.4 2.8 0.3 0.4 0.6 2.5 . . E sd Bolivina sp. D NUMBERS SAMPLE Bolivina Bolivina sp. G Bolivina sp. R Bolivina sp. L Bolivina sp. 0 Bolivina sp. S Bolivina sp. T Buccella hannai Bolivina? sp. K Bulimina alazanensis Buliminellaeleqantissima Bulimina mexicana Bulimina socialis Bulimina tessellata Burseolina palmerae Cancris saqra Cassidulina carinata Cassidulina crassaCassidulina curvata Cassidulina norcrossi var. australis Cassidulina reflexa Cassidulinoides bradyi Cassidulina subqlobosa Chilostomella czizeki Cassidulinoides sp. A Cibicides cicatricosus Cibicidoides corvelli Cibicidoides barnetti Cibicidoides bradyi Cibicides lobatulus Cibicides wuellerstorfi Cibicidoides incrassatusCibicidoides mundulus Cibicidoides pachyderma forma bathyalis 1.8

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 305 22 5.2 0.3 0.3 0.3 1.3 1.3 0.5 0.5 21 RD RD 10.2 0.8 1.2 RD 0.4 0.4 0.8 0.8 16 19 RD 0.9 5.2 1.3 3.3 0.8 RD 0.8 0.4 0.5 1.7 1.0 10-1 14 1.0 0.3 0.3 1.0 0.3 3.5 DM DM 2.5 10-2 0.4 0.7 0.4 13 RD 0.41.4 0.80.8 FD 3.4 0.7 0.4 0.4 1.1 1.0 0.4 1.5 RD 1.9 0.7 2.3 2.4 1.3 3.8 0.4 2.7 2.5 2.8 1.1 1.1 0.6 a RD 0.7 0.7 2.00.7 1.40.3 1.6 2.9 1.5 2.5 1.7 0.5 0.3 0.7 0.3 0.5 0.4 0.3 0.3 1 2 7 9 12 1.0 0.3 0.3 1.3 0.3 0.7 1 1.6 AW a 1.9 0.7 0.3 1.7 0.9 0.3 2.0 0.3 0.4 0.9 125 0.2 0.40.3 2.2 4.00.7 0.9 2.0 0.9 0.4 0.4 1.6 0.8 0.4 9.7? 4.7 DMR FD 1.6 0.3 0.8 0.3 0.3 0.4 0.3 FD DM 0.3 139 2-8 17 0.3 0.3 3.7 0.3 DM 2-1 3.6 1.1 2.2 2.2 SAMPLE NUMBERS Cibicidoides pachydermaCibicidoides forma sublittoralis sinistralis Clavulina mexicana Dentalina communis Eqqerrella bradyi Elphidium qunteri forma salsum Elphidium lanieri Elphidium poeyanum Epistominella advena Epistominella exiqua Fissurina alveolata Epistominella sp. P Epistominella sp. S Eponides weddellensis Fursenkoina pontoni Fissurina laeviqata Fursenkoina compressa Globobulimina pactfica Gyroidina altiformis Gavelinopsis transluscensGavelinopsis sp. A Hanzawaia sp. A Gyroidina altispira Haynesina depressula var. mataqordana Gyroidina sp. cf. G. umbonata Hoeqlundina eleqans Gyroidinaqirardana Gyroidina laevis Gyroidina umbonata Karreriella bradyi Gyroidina reqularis Laterostomella subspinescensLenticulina americana Gyroidina trincherasensis Lenticulina dicamplya

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 306 22 RD 0.5 1.0 1.6 1.8 1.3 0.8 0.8 21 RD 1.2 3.5 4.9 1.2 1.2 0.4 1.2 3.5 2.8 16 19 0.4 0.4 3.5 1.7 0.4 0.3 1.0 2.5 2.8 2.0 4.6 2.8 0.5 DM FD RD RD 1.4 1.0 0.3 0.4 1.7 3.1 3.1 0.4 0.3 1.0 1.4 0.3 10-2 10-1 14 2.9 0.4 2.5 13 1.9 2.3 12 7 12 FD RD DM 1.1 1.3 0.7 0.7 0.3 0.3 0.4 0.4 0.3 0.30.6 0.7 0.4 0.7 0.6 5.3 9.7 9.4 0.4 0.7 0.90.4 0.7 0.4 0.7 1.3 0.4 2.9 0.7 1.9 0.4 2.9 0.7 0.4 3.1 0.4 0.4 0.4 2.2 0.7 1.6 1.1 2.8 0.4 2.9 1.3 0.3 0.3 1.0 0.3 0.4 FL FL RD FD 0.3 0.3 0.3 0.7 0.3 0.4 1.3 1.0 0.7 0.6 1.2 0.9 0.3 RD AW 125 1 1 2 7 9 0.4 0.7 1.1 1.1 0.4 0.9 0.2 1.7 0.2 0.6 0.7 0.3 1.2 0.8 0.9 0.3 0.8 4.8 2.2 0.8 0.4 0.8 1.2 0.4 0.3 0.8 0.4 0.3 1.2 0.6 0.3 0.3 0.4 0.8 139 2-8 17 0.6 0.3 0.3 0.3 0.3 0.4 0.3 1.8 0.6 DM FD DM DNfl 2-1 1.1 1.1 1.1 0.4 NUMBERS SAMPLE Lenticulina intusvortex Lenticulina sp. A Lenticulina sp. B Loxostonum geibi Martinotiella nodulosa Melonis affinis Nodosaria longiscata Nonion? sp. Nodosaria subtertenuata Oolina qlobosa Planulina ariminensis Pleurostomella afternans Oridorsalis umbonatus 3.3 Pleurostomella cubensisPseudononion atlanticumPseudononion qrateloupi Orthomorphina aminaensisOsanqularia culter i Pullenia bulloides Pullenia salisburyi Pullenia subcarinata Rectobolivina mexicana Pyrqo murrhina Ouinqueloculina seminulina Recurvoides trincherasensisReussella spinulosa Rosalinafloridana Ouinqueloculina sp. Rosalina concinna Sagrina pulchella Siqmavirqulina tortuosa Siqmoilopsis schlumberqeriSiphonina bradyana Siphonina pozonensis Siqmoilinatenuis

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 307 22 RD 3.1 83 11.7 0.31 0.4 0.4 0.3 8.3 2.57 3.24 0.27 2.5 1.2 0.4 1.2 0.4 1.7 0.8 3.1 79 75 49 3.85 3.70 0.60 0.54 1.5 2.3 1.7 1.3 5.2 6.1 1.3 5.2 113 DM RD RD RD RD 0.7 0.3 79 1.4 0.4 1.2 2.8 1.1 1.4 85 4.0 5.0 0.61 0.55 0.47 13 10-2 10-1 14 16 19 21 0.4 1.2 6.6 1.1 63 1.9 1.1 0.49 3.44 3.95 3.78 3.98 12 74 0.4 1.5 3.64 RD RD RD DM 0.3 0.4 0.3 2.3 3.1 66 0.3 3.33 0.42 0.51 RD 0.40.6 0.4 0.4 0.4 0.4 0.3 80 1.8 0.4 3.68 0.49 2 7 9 0.7 1.6 1.2 0.3 0.3 0.63 1 FL FL 1.0 1.0 7.0 2.0 2.9 1.9 1.9 80 74 1.0 3.3 0.4 3.7 0.61 0.3 1.1 0.3 96 0.3 0.3 1.6 3.81 3.89 3.84 0.47 RD AW 0.4 0.3 125 1 0.4 1.7 0.2 6.2 0.2 0.4 0.4 0.4 0.6 0.3 0.4 5.6 2.7 12.8 0.2 0.3 0.50 0.63 DM DMR 0.8 98 87 177 3.36 3.78 4.71 RD 139 2-8 17 0.3 0.6 2.67 0.20 0.29 DM 2-1 0.4 3.33 0.35 qracillima NUMBERS SAMPLE Siphonina pulchraSiphonodosaria lepidula 0.6 0.6 1.2 2.30.4 Siphonodosaria nuttalli Siphonodosaria nuttalli var.Sphaeroidina bulloides Stilostomella sp. A Stainforthia complanata Stllostomella granulifera Uviqerina auberiana Textularia leuzinqeri Textularia mexicana Textularia yaquatensis Uviqerina azuana Uviqerina carapitana Textularia yasicaensisTrifarina bradyi Uviqerina ciperana Uviqerina mantaensis Uviqerina hispida Uviqerina parvula Uviqerina pereqrina Uviqerina piqmaea Uviqerina proboscidea Uviqerina viaensis Valvulineriafloridana Valvulineria mexicana 0.4 0.7 Valvulineria qasparensis 4.7 SHANNON-WEINER DIVERSITYFXN EQUITABILITY SPECIES RICHNESS 80 71

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission 308 74 RD 1.3 0.6 0.3 0.8 11.6 5.6 0.3 2.5 1.6 0.3 1.9 2.2 8.2 66 70 RD FD 1.3 0.3 0.3 5.4 4.7 0.6 0.30.3 64 1.0 0.3 3.0 0.6 0.3 15.2 3.6 2.8 2.7 5.4 1.3 2.4 0.3 1.9 0.6 1.0 2.24.1 2.7 3.5 1.7 18.0 17.6 3.8 3.1 2.9 38.5 6.1 5.1 0.6 RD RD RD 6.1 RD 0.3 0.3 3.9 0.9 11.6 42 46 49 59 RD 2.2 1.8 4.5 1.6 18.0 2.4 14.3 0.2 0.9 0.3 0.3 0.5 3.1 11.6 RD RD 0.4 0.4 0.4 0.6 0.4 0.2 2.7 0.4 1.2 6.0 1.7 3.6 2.1 5.2 RD 0.3 0.6 7.4 0.3 0.3 7.7 0.3 2.0 0.2 0.9 0.3 0.6 4.3 0.3 6.2 0.7 7.9 2.6 6.3 0.3 RD RD 0.4 1.80.30.3 0.3 0.3 0.3 1.1 0.7 0.4 0.4 2.9 0.3 0.6 4.1 1.1 0.4 0.4 1.1 2.1 0.6 0.7 1.8 8.1 37.5 4.6 1.1 18.3 0.4 0.3 0.3 1.9 0.7 0.3 0.3 3.3 16.5 0.7 5.3 0.4 2 .2 0.4 1.3 2.8 4.6 9.7 FD RD RD DM 1.4 1.4 1.6 0.7 1.8 0.7 5.2 15.3 6-1 113 114 115 3-2 117 119 33 36 38 DM 1.1 0.5 0.4 0.4 0.4 1.50.7 1.22.8 0.4 4.3 0.4 11.1 35.5 53.1 18.4 17.4 0.7 NUMBERS Ammnbaculites sp. SAMPLE Ammonia parkinsoniana Ammodiscus dominicensis var. deformis Amphisteqinaqibbosa Anquloqerina angulosa Anquloqerina carinata var. bradyana Anquloqerina eximia Anqulogerina jamaicensis Anomalinaflintii Anquloqerina quraboensis Anquloqerina occidentalisAnquloqerina selseyensis Asteriqerina carinata Bermudezinella riveroi Bolivina alata Bolivina albatrossi Anomalinoides sp. Bolivina arta Bolivinadaqqaria Bolivina byramensis Bolivina furcata Bolivina qoessi Bolivina inflata Bolivina lowmani Bolivina marqinata var. multicostata Bolivina minima Bolivina pyqm aea Bolivina pisciformis Bolivina plicatella var. mera Bolivina obscuranta Bolivina paula Bolivina striatula var. soinata Bolivina tectiformis Bolivina sp. A Bolivina sp. C

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 309 74 1.3 0.8 1.3 3.4 0.3 6.7 7.9 1.1 1.6 0.8 1.9 1.1 RD RD RD 0.3 0.3 1.4 64 66 70 1.0 0.9 1.0 2.7 0.3 0.3 1.3 0.3 0.3 1.3 59 RD RD 1.9 1.0 0.3 2.7 1.3 0.6 0.9 49 1.5 2.1 1.2 RD RD 0.3 2.1 13.1 42 46 1.8 0.4 0.9 0.9 0.4 1.8 2.8 3.6 38 RD FD 1.2 1.0 0.9 0.6 0.6 0.2 0.2 1.6 9.2 1.8 4.2 0.3 3.7 1.9 0.4 3.6 0.8 1.6 5.5 1.2 0.4 2.4 1.6 33 36 0.3 2.8 0.3 0.60.33.2 1.8 0.3 0.6 119 2.6 0.9 1.5 0.4 0.3 0.71.0 0.3 16.9 1.3 0.9 0.7 FD RD PD RD 0.4 0.7 1.2 0.8 1.1 1.1 3 .7 0.4 2.2 0.4 0.4 2.2 1.1 0.3 FD DM 0.3 1.3 2.2 0.3 1.8 0.3 0.6 1.0 1.5 0.7 1.9 RD 114 115 3-2 117 1.4 1.5 0.7 1.1 8.2 0.2 0.2 2.1 0.5 0.4 0.5 DM FD 6-1 113 9.3 2.3 1.1 0.4 1.1 0.4 0.7 0.7 NUMBERS SAMPLE Bolivina sp. D Bolivina sp. E Bolivina sp. G Bolivina sp. 0 Bolivina sp. R Bolivina? sp. K Bolivina sp. L Bolivina sp. S Bolivinasp. T Buccella hannai Bulimina alazanensis Bulimina mexicana Bulimina socialis Bulimina tessellata Buliminella eleqantissima Burseolina palmerae Cassidulina carinata Cancris saqra Cassidulina crassa Cassidulina curvata Cassidulina norcrossiCassidulina var. australis reflexa Cassidulina subqlobosa Cassidulinoides bradyiCassidulinoides sp. A Cibicides cicatricosus Cibicidoides bradyi Chilostomella czizeki Cibicides lobatulus Cibicides wuellerstorfi Cibicidoides barnetti Cibicidoides corvelli Cibicidoides incrassatusCibicidoides mundulus Cibicidoides pachyderma forma bathyalis I

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 310 74 4.2 1.9 2.6 FD RD 0.6 0.6 3.7 1.1 0.6 1.9 66 70 FD 0.6 1.3 0.9 1.7 3.2 0.3 64 1.4 2.5 0.70.3 1.7 1.7 0.6 1.4 0.3 0.3 0.8 FD FD 0.9 0.6 0.3 0.3 0.6 0.6 0.3 1.9 1.5 0.3 29.7 0.6 0.3 3.9 0.3 3.0 3.9 0.3 42 46 49 59 FD FD FD 1.3 0.9 0.8 1.1 1.3 2.1 38 1.0 0.5 1.3 1.9 15.0 4.9 6.6 RD RD 5.1 2.8 0.9 0.2 FD 33 36 1.5 3.2 0.3 0.3 0.6 0.3 1.5 6.0 0.3 0.3 FD 0.3 0.3 0.3 1.3 0.3 0.4 FD 117 119 2.1 0.7 2.0 0.6 0.4 0.4 1.1 0.4 0.3 1.1 0.3 2.0 0.3 0.3 1.4 2.3 0.3 0.4 FD RD RD DM 0.5 2.8 DM 6-1 113 114 115 3-2 0.7 0.4 1.1 3.0 0.4 0.4 SAMPLE NUMBERS Cibicidoides pachyderms forma sublittoralis Dentalina communis Cibicidoides sinistralis Clavulina mexicana Eqqerrellabradyi Elphidium gunteriforma salsum Elphidium lanieri Elphidium poeyanum Epistominella advena Epistominella exigua Epistominella sp. P Fissurina alveolata Epistominella sp. S Eponides weddellensis Fursenkoina compressaFursenkoina pontoni Fissurina laevigata Gavelinopsis transluscens Gavelinopsis sp. A Globobulimina pacifica Gyroidina altiformis Gyroidina qirardana Hanzawaia sp. A Gyroidina attispira Gyroidina laevis Gyroidina regularis Gyroidina sp. cf. G. umbonata Haynesina depressulaHoeglundina var. matagordana elegans Karreriellabradyi 0.7 1.4 0.43.0 Gyroidina trincherasensisGyroidina umbonata Laterostomella subspinescens Lenticulina dicamplya Lenticulina americana

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. RD 0.3 0.8 1.9 1.1 0.6 0.8 66 70 74 0.3 0.8 2.2 0.6 1.3 0.9 3.5 1.7 1.1 3.5 0.7 1.9 3.1 0.7 1.7 0.30.3 0.9 0.3 59 64 0.6 1.0 0.9 0.3 3.7 1.6 0.3 1.6 0.7 0.6 1.0 1.8 4.0 17.7 RD RD FD RD RD RD 0.6 0.3 0.9 0.9 42 46 49 1.3 38 FD RD 1.2 0.2 1.2 0.2 4.0 1.2 1.6 2.0 0.4 4.3 2.0 1.8 0.6 33 36 0.6 0.9 5.1 5.1 1.3 2.5 0.3 0.6 0.4 3.7 2.4 3.0 2.8 3.4 0.9 4.2 1.6 2.5 2.8 2.52.4 0.60.3 1.3 119 2.3 2.6 1.1 1.1 0.4 1.1 1.0 0.4 2.3 3-2 117 0.4 1.5 0.3 0.40.4 0.7 0.7 0.6 0.40.4 0.6 0.6 1.1 0.4 0.2 FD DM RD RD FD RD 0.3 1.2 0.3 0.4 0.6 1.1 11.0 3.9 114 115 0.4 3.2 4.6 1.3 1.8 1.1 0.4 0.4 0.4 1.1 1.1 FD RD 1.1 0.9 0.4 1.1 0.5 0.4 DM 6-1 113 1.1 0.4 2.2 0.4 0.2 1.8 0.4 A NUMBERS SAMPLE Lenticulina intusvortex Lenticulina sp. Lenticulina sp. B Loxostonum qelbi Martinotiella nodulosa Melonis affinis Nodosaria lonqiscata Nodosaria subtertenuata Nonion? sp. Oolina qlobosa Planulina ariminensis Pleurostomella alternans Oridorsalis umbonatus Orthomorphinaaminaensis Pleurostomella cubertsiaPseudononion atlanticum Osanqularia cutter Pseudononion arateloupi Pullenia bulloides Pyrqo murrhina Pullenia salisburvi Pullenia subcarinata Recurvoides trincherasensis Rectobolivina mexicana Reussella spinulosaRosalina concinna Quinqueioculina seminulina Quinqueloculina sp. Rosalinafloridana Saqrina pulchella Siqmavirqulina tortuosa Siqmoilopsis schlumberqeri Siphonina pozonensis Siqmoilinatenuis Siphonina bradyana

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 312 5.3 1.3 3.82 0.6 0.3 0.6 2.2 0.6 0.3 2.8 104 85 0.3 1.6 0.3 4.7 1.1 1.1 3.99 4.01 0.3 0.3 0.41 0.67 0.53 0.54 59 64 66 70 74 0.6 0.7 4.1 1.4 0.6 51 57 77 82 RD RD RD RD RD RD FD 1.5 0.3 0.9 2.1 0.3 2.4 1.0 1.3 9.4 7.1 3.60 2.71 2.60 3.46 0.9 0.3 6.7 9.8 1.8 2.2 0.53 0.48 0.29 0.24 0.5 5.3 0.7 0.36 FD FD RD 1.2 6.7 0.7 1.2 2.7 1.6 64 52 65 77 3.2 5.8 4.0 3.69 2.93 3.53 0.62 33 36 38 42 46 49 RD 1.2 1.2 8.6 0.3 0.57 RD 119 1.6 0.2 2.0 3.36 4.01 2.5 3.1 3.2 117 2.5 26.6 0.7 3.20 0.7 FD DM FD 73 90 79 78 97 1.9 0.7 0.3 3.1 5.2 FDFD 0.2 0.3 0.4 113 114 115 3-2 48 98 0.2 0.5 DM 6-1 0.4 81 0.4 0.27 0.15 0.42 0.31 0.43 0.31 0.37 NUMBERS SAMPLE Siphonodosaria lepidula Siphonina pulchra Siphonodosaria nuttalli Siphonodosaria nuttalli var. gracillima Sphaeroidina bulloides Stainforthia complanata Stilostomella granulifera Stilostomella sp. A Textularia leuzingeriTextularia mexicana 2.1 Textularia yaquatensisTextularia yasicaensis Uviqerina auberiana 0.30.7 Uviqerina azuana Trifarina bradyi Uviqerina carapitana Uviqerinaciperana Uviqerina hispida Uviqerina mantaensis Uviqerina parvula Uviqerinapereqrina Uviqerinapiqmaea Uviqerina proboscideaUviqerina viaensis 3.6 1.8 Valvulineria qasparensis Valvulineria floridana EQUITABILITY Valvulineria mexicana SHANNON-WEINER DIVERSITY FXN 3.10 1.94 3.72 3.13 3.65 SPECIES RICHNESS

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 313 1-4 3.9 43.6 0.8 0.9 0.4 0.4 2.1 0.4 0.8 0.6 4.6 3 1-1 HW DM DM 1.0 6.3 7.7 1 0.3 TAB 1.0 5 0.8 0.3 0.3 1.0 1.1 0.7 1.1 1.4 1.1 1.0 0.3 0.3 8.9 3.8 1.0 DM TAB 13-8 4.2 2.5 DM DM 0.3 0.5 0.3 3.1 5.3 0.3 13-3 13-4 0.3 1.7 0.3 1.2 0.3 0.3 DM 1.4 0.7 0.5 2.0 10.20.3 4.7 7.6 DM 0.3 1.0 0.3 5-11 13-1 0.3 2.8 1.0 2.1 4.0 1.0 0.3 2.3 5-1 0.3 1.3 0.5 0.2 0.8 0.7 0.8 3.4 0.3 2.2 0.7 2.4 0.4 2.6 0.3 7.5 10.9 0.4 RD DM DM DM 101 12-1 11-2 7.3 2.1 6.6 1.1 0.3 RD 2.3 1.1 0.5 0.7 0.9 0.4 0.2 1.0 0.3 1.4 1.4 0.9 2.2 1.1 3.7 1.4 3.2 0.2 1.7 0.3 76 79 84 RD RD 1.5 0.7 0.7 0.40.7 1.7 3.0 0.61.70.3 1.5 2.0 0.4 1.1 0.7 1.5 0.7 4.1 0.7 NUMBERS SAMPLE Ammodiscus dominicensis var. deformis Amphisteqina qibbosa Ammonia parkinsoniana Ammobaculites sp. Anquloqerina carinata var. bradyana Anquloqerina anqulosa Anquloqerina eximia Anquloqerina quraboensisAnquloqerina jamaicensis Bolivina alata Anomalinaflintii Anquloqerina occidentalisAnquloqerina selseyensis Bolivina albatrossi Bermudezinella riveroi Anomalinoides sp. Asteriqerina carinata Bolivina arta Bolivina bvram ensis Bolivinadaqqaria Bolivina furcata Bolivina qoessi Bolivina inflata Bolivina lowmani Bolivina minima Bolivina marqinata var. multicostata Bolivina obscuranta Bolivina paula Bolivina pisciformis Bolivina plicatella var. mera Bolivina pyqm aea Bolivina striatula var. spinataBolivina tectiformis Bolivina sp. A Bolivinasp. C

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 0.6 2.1 3.9 DM DM 1.7 0.4 3 1-1 1-4 0.3 0.3 0.7 1.4 8.8 0.7 1.4 2.5 1.8 0.6 0.7 0.8 2.8 2.7 0.6 4.5 0.9 10.0 13-4 13-8 5 1 23.6 1.7 1.7 5.2 0.8 0.3 1.0 0.52.03.1 1.5 0.3 2.4 1.4 1.0 13.4 8.0 0.9 2.2 3.1 15.3 1.3 0.3 DM DM DM DM TAB TAB HW 4.1 1.7 10.5 32.2 4.1 DM 0.3 2.8 3.7 0.7 DM DM 1.0 0.8 1.3 11-2 5-1 5-11 13-1 13-3 3.0 3.2 1.0 3.4 0.2 0.4 0.4 1.8 4.0 0.7 0.5 2.9 1.8 3.9 3.7 33.9 2.5 4.7 RD DM 1.8 26.7 84 101 12-1 RD 1.4 5.5 1.4 2.8 14.4 6.8 5.0 0.7 2.4 31.2 1.5 79 4.0 7.4 0.7 0.3 76 RD RD 0.4 0.4 0.9 0.4 0.4 2.2 5.7 0.4 2.2 0.4 Bolivina sp. D NUMBERS SAMPLE Bolivina sp. E Bolivina sp. G Bolivina sp. L Bolivina sp. O Bolivina sp. R Bolivina sp. S Bolivinasp. T Bolivina? sp. K Buccella hannai Bulimina alazanensis Bulimina mexicana Buliminella eleqantissim a Burseolinapalmerae 0.7 Bulimina tessellata Bulimina socialis 1.1 Cassidulina carinata Cassidulina crassa Cancris sagraCassidulina curvata 1.9 3.2 9.1 Cassidulina norcrossi var. australis Cassidulina retlexa Chilostomella czizeki Cassidulinoides bradyi 1.1 Cassidulina subglobosa Cassidulinoides sp. A Cibicides cicatricosusCibicides lobatulus Cibicides wuellerstorfi Cibicidoides coryelli Cibicidoides barnetti Cibicidoides bradyi Cibicidoides mundulus Cibicidoides incrassatus 0.4 Cibicidoides pachydermaforma bathyalis 3.0 I

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1-4 1.8 0.6 0.3 1-1 1.3 1.7 1.7 0.8 0.4 0.4 0.8 0.4 0.4 7.3 1.7 0.3 6.6 1.7 1 3 0.3 1.0 2.8 1.4 3.5 2.8 1.0 1.0 0.3 2.2 0.3 TAB TAB HW DM DM 0.3 0.7 2.5 2.2 DM 26.3 0.7 0.3 DM 13-4 13-8 5 0.7 2.4 2.4 1.0 3.1 0.33.4 7.3 4.5 16.1 13-1 13-3 0.3 0.3 0.7 0.3 0.3 38.1 0.3 0.6 0.7 0.2 0.5 0.7 5.1 9.5 1.0 0.8 11.3 0.8 DM DM DM DM DM DM 6.50.4 5.6 0.7 0.6 1.0 0.6 0.3 15.2 2.7 5.1 5.5 2.1 3.4 84 101 12-1 11-2 5-1 5-11 RD RD 3.7 3.7 0.5 0.4 1.0 1.3 1.7 19.7 FD 1.7 0.31.3 2.5 0.8 3.4 2.5 0.3 0.3 0.3 0.6 10.7 0.3 2.2 0.3 3.4 1.7 3.0 0.5 5.0 76 79 RD 0.7 0.4 0.7 0.4 2.3 0.7 1.5 0.9 1.1 0.4 8.6 0.4 0.4 0.7 0.7 A . . sd SAMPLE NUMBERS Cibicidoides pachyderms forma sublittoralis Dentalina communis Cibicidoides sinistralis Elphidium lanieri Eqqerrella bradyi Elphidium qunteri forma salsum Clavulina mexicana Epistominella advena Elphidium ooevanum Epistominella exiqua Epistominella sp. P Epistominella sp. S Eponides weddellensis Fursenkoinacompressa Fissurina alveolata Fissurina laevigata Fursenkoina pontoni Gavelinopsis transluscens Gavelinopsis sp. A Gyroidina altiformis Globobulimina pacifica Gyroidina aftispira Gyroidina qirardana Gyroidina reqularis Haynesina depressulavar. mataqordana Gyroidina laevis Hoeqlundina eleqans Gyroidina trincherasensis Gyroidina sp. cf. G. umbonataHanzawaia Karreriella bradyi Lenticulina dicamplya Laterostomella subspinescensLenticulina americana Gyroidina umbonata

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2.4 DM DM 0.8 0.4 0.6 0.8 3 1-1 1-4 HW 0.3 0.3 19.5 0.3 20.2 1 4.2 2.4 0.7 0.7 0.3 3.50.3 4.9 0.3 5 0.6 0.6 0.4 6.4 0.3 0.3 0.3 0.2 0.8 3.3 0.3 2.8 1.2 2.0 8.3 1.3 33.5 1.3 1.9 0.3 6.5 0.3 1.4 1.30.3 DM DM DM TAB TAB 13-3 13-4 13-E 0.7 0.5 0.7 0.3 0.6 0.8 1.7 2.4 DM 5-11 13-1 5-1 0.7 0.32.8 0.3 0.7 7.3 2.7 3.0 40.2 0.3 0.3 1.3 1.1 0.7 4.8 0.2 0.2 2.6 0.2 1.4 0.7 2.2 0.4 0.2 5.4 1.8 12.3 0.6 84 101 12-1 11-2 0.5 1.4 1.3 3.2 79 RD RD RD DM DM DM DM 0.3 0.3 0.4 0.7 76 0.4 0.4 0.4 3.0 1.1 1.5 0.5 0.4 NUMBERS Lenticulina intusvortex Lenticulina sp. A SAMPLE RD Lenticulina sp. B Maitinotiella nodulosa Loxostonum gelbi Melonis affinis 3.7 Nodosaria subtertenuata 1.1 Nodosaria longiscata Nonion? sp. Oolina globosa Planulina ariminensis Oridorsalis umbonatusPleurostomella alternansPleurostomella cubensis 3.0 Orthomorphina aminaensisOsangularia cutter Pseudononion qrateloupi Pseudononion atianticum Pullenia bulloides Pullenia salisburvi Pullenia subcarinata Pyrgo murrhina Recuivoides trincherasensis 1.9 Quinqueloculina seminulinaRectobolivina mexicana Reussella spinulosaRosalina concinna 0.7 Quinqueloculina sp. Rosalinafloridana Siqmavirqulina tortuosa Saqrina pulchella Siqmoilopsis schlumberqeri Siqmoilinatenuis 0.42.1 Siphonina bradyanaSiphonina pozonensis 2.6

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 317 0.6 0.6 0.6 7.9 2.57 1-1 1-4 DM DM 0.8 1.7 2.5 1.3 7.6 0.7 35 75 57 8.7 1.7 3.8 0.7 TAB HW 84 2.4 5 1 3 1.7 0.8 0.8 3.4 0.3 1.7 6.6 7.3 7.6 0.4 TAB 0.6 0.7 2.2 2.5 0.3 0.53 0.60 0.44 0.48 0.23 3.83 3.91 2.73 3.59 DM DM 2.5 13-4 13-6 1.3 0.2 0.35 0.23 DM 2.1 1.0 0.8 13-2 7.9 3.59 3.01 2.25 31 85 57 41 87 5.1 0.40 0.43 5-11 13-1 0.33.4 0.8 0.3 1.92 2.51 DM DM DM 0.7 0.7 0.3 56 34 0.3 2.62 0.2 0.2 2.7 0.50 0.25 0.20 1.1 0.4 0.8 0.3 1.8 1.1 2.2 1.4 1.0 0.4 3.68 3.76 101 12-1 11-2 5-1 84 2.68 2.29 0.32 0.34 0.49 RD RD RD DM DM 1.0 0.5 7.2 2.1 64 45 29 81 85 0.3 0.5 1.7 10.4 1.7 0.7 3.38 76 79 0.4 0.4 86 1.1 0.7 0.4 3.95 NUMBERS Siphonina pulchra Siphonodosaria lepidula 1.1 SAMPLE RD Siphonodosaria nuttalli Siphonodosaria nuttalli var. gracillima Stainforthia complanata 0.4 Sphaeroidina bulloides Stilostomella granulifera Stilostomella sp. A Textularia leuzingeri Textularia mexicana 0.7 Uviqerina auberiana 6.4 Uviqerina azuana 7.9 Trifarina bradyi Textularia yaguatensisTextularia yasicaensis Uviqerina carapitana Uviqerinaciperana Uviqerina hispida Uviqerina mantaensis Uviqerinaparvula Uviqerina pereqrina 0.5 Uviqerinapiqmaea Uviqerina proboscidea Uviqerina viaensis Valvulineria floridana Valvulineria qasparensis EQUITABILITY 0.60 0.46 Valvulineria mexicana SHANNON-WEINER DIVERSITYFXN SPECIES RICHNESS

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. VITA

Peter P. McLaughlin was bom on August 4,1962 in Yeadon, PA. He was raised just outside of Dover, DE, and gradutaed from Caesar Rodney High School in June of 1980. In 1984, he obtained a B.S. in geology from the University of Delaware, with a senior thesis under the direction of Dr. F.M. Swain entitled "Jurassic foraminifera of the Cotton Valley Group, northern Louisiana". He is married to the former Jennifer Lee Picard of Dover, DE, and they have two children, Margaret Elizabeth and Katherine Elizabeth. He started graduate work at Louisiana State University in August, 1984, and completed and defended his dissertation in March, 1989. He is currently employed as a micropaleontologist in the Exploration Concepts section of Exxon Production Research Company, Houston, TX.

318

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DOCTORAL EXAMINATION AND DISSERTATION REPORT

Candidate: PETER P. MCLAUGHLIN, JR.

Major Field: GEOLOGY

Title of Dissertation: NEOGENE BASIN EVOLUTION IN THE SOUTHWESTERN DOMINICAN REPUBLIC: A FORAMINIFERAL STUDY

A pproved:

W.Arvan den BOLD Major Professor and Chairman

— d / / ? /? T- Dean of the Graduate

EXAMINING COMMITTEE:

B.K. SEN GUPTA______Major Professor - co-chairman

ARNOLD H. BOUMA //

JOSEPH E. HAZEL

CHAD L. MCCABE r- 0

Date of Examination:

______MARCH 16. 1989

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