RICE UNIVERSITY

PALEO-ENVIRONMENTS OF MIDDLE CHAETETES LITHOTOPES, TEXAS AND NEW MEXICO

by

JOAN MUSSLER SPAW

A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF

MASTER OF ARTS

THESIS DIRECTOR'S SIGNATURE:

Houston, Texas

April, 1977 ABSTRACT

PALEO-ENVIRONMENTS OF MIDDLE PENNSYLVANIAN

CHAETETES LITHOTOPES, TEXAS AND NEW MEXICO

Joan Mussler Spaw

Detailed field studies and petrographic analyses of

Chaetetes-bearing sections reveal Chaetetes in the presence of Profusulinella in the La Tuna and Berino Formations (Morrowan-Atokan) of the Magdalena in the Northern Franklin and Hueco Mountains, Texas and New Mexico. Chaetetes and non-Chaetetes lithotopes are characterized by a diverse and abundant assemblage of benthonic organisms typical of a clear, well-illuminated shallow-water carbonate platform of

the late Paleozoic. Two chaetetid growth forms with apparent

écologie significance were observed: shingle-form Chaetetes and club-form Chaetetes. Shingle-form Chaetetes are charac¬ terized by numerous increases or decreases in width of the upward-growing colony, and commonly form anastomosing com¬ plexes of colonies. Club-form Chaetetes evidence subtle changes in width, emphasizing growth along the vertical axis;

clustering of solitary club forms is common. Both growth forms are excluded from high-energy shoaling environments. Shingle-form Chaetetes are restricted to the base of litho¬

topes characterized by prolific growths of phylloid algae. Cuneiphycus, and tubular organisms. Competition with these organisms for substrate space apparently limits Chaetetes distribution on the platform. Common, erratic growth dis¬ continuities in shingle forms and associated burrow-churned wackestones and packstones imply frequent fluctuations in the physical and biological environment. Stagnant, poorly oxygenated conditions on the sea floor limit solitary club- form Chaetetes to the base of a laminated bioclastic mudstone lithotope. Relatively stable conditions in quieter, deeper water are suggested by the associated discretely burrowed, well-laminated mudstones and wackestones. ACKNOWLEDGEMENTS

This study was made possible thanks to the support of several individuals and organizations. I would like very much to thank Dr. J. L. Wilson for suggesting and supervising this study, and for identifying the fusulinids; Dr. R. E. Casey and Dr. J. E. Warme, members of my thesis committee, for their suggestions with the thesis work; Dr. D. V. LeMone, of the University of Texas at El Paso, for discussions on taxonomy and suggestions on field studies; and Richard, my husband, for his invaluable assistance in the field, and for comments on earlier manuscripts; and my parents, Mr. and Mrs. George Muss1er, for their encouragement and support. Financial assistance for travel and field expenses was provided by a Doherty

Foundation Grant and a Penrose Bequest Research Grant; incidental expenses were covered by the Weiss Fund. During this study, the writer has been supported by a Doherty

Fellowship and a Weiss Fellowship. CONTENTS Page Introduction 1 Purpose and Scope 1 Methods of Study 3 History of Previous Investigations 7 Taxonomy 7 Stratigraphy 8 Paleo-environmental Studies 10 Description of Chaetetes 12 General Morphology 12 Growth Form 14 Significance of Growth Form 14 Chaetetid Growth Forms 15 Growth Banding 20 Interpretation of Growth Forms 24 Ecologie Controls of Chaetetes Growth and Distribution 32 Lithotope Relationships 32 Physical Environment 32 Depth and Water Movement 32 Light 37 Turbidity 38 Salinity 38 Organic Productivity 38 Nature of the Substrate 39 Geomorphology of the Sea Floor 41 Stability of the Environment 41 Biological Environment 43 Mutualism 43 Competition 44 Conclusions 46 References 47

Appendix I. Lithotope Descriptions 63 Appendix II. Measured Sections 79 ILLUSTRATIONS

Figure Page 1. Index map for the Hueco and Northern 2 Franklin Mountains.

2. Generalized stratigraphic sections for the 5 Hueco and Northern Franklin Mountains. 3. Index map for the Llano region of center 6 Texas. 4. General morphology and terminology 13 for Chaetetes. 5. Shingle growth forms of Chaetetes. 17 6. Shingle-form Chaetetes form large 18 anastomosing complexes. 7. Rugose encrusted by Chaetetes. 19 8. Club growth form of Chaetetes. 21

9. Regeneration in Chaetetes. 22 10. Comparison of growth-banding in shingle- 25 form and club-form chaetetids. 11. Enclosed- versus open-skeletal systems. 28 12. Chaetetes-bearing lithotopes. 33

13. Substrate colonizers. 35 14. Submounded surfaces. 40

15. Idealized reconstruction of a shallow 42 carbonate shelf showing Chaetetes distributions (in black) and lithotope relations. Plate Page 1. Shingle-form Chaetetes. 58 2. Large anastomosing complex of shingle- 59 form Chaetetes. 3. Large anastomosing complex of shingle- 60 form Chaetetes. 4. Club-form Chaetetes. 61

5. Clustering of club-form Chaetetes. 62

I. Oolitic Grainstone; Archaeolithophyllid 74 Grainstone II. Osagid Grainstone; Oncolithc Grainstone 75 III. Calcitornellid Packstone-Grainstone; 76 Cuneiphycus Packstone-Grainstone.

IV. Crinoidal Packstone-Grainstone; 77 Intraclastic Bioclastic Wackestone. V. Encrusted Phylloid Algal Wackestone; 78 Phylloid Algal Wackestone-Packstone. VI. Pelleted Foraminiferal Wackestone-Packstone; 79 Tubular Pspecies Wackestone-Packstone.

VII. Abraded Bioclastic Packstone; Laminated 80 Bioclastic Mudstone-Wackestone. 1

PALEO-ENVIRONMENTS OF MIDDLE PENNSYLVANIAN

CHAETETES LITHOTOPES,

TEXAS AND NEW MEXICO V

INTRODUCTION

Purpose and Scope

The Chaetetes-Profusulinella faunizone is a restricted, nearly synchronous time-stratigraphic marker for the Middle

Pennsylvanian (Atokan) of the Cordillerans, and has greater stratigraphic range in the mid-continent being most abundant in the Desmoinesian (Dott, 1955); however, knowledge of the environmental factors controlling the time-stratigraphic range of Chaetetes has remained limited (Winston, 1963a and b,

1965; Rich, 1969; Lustig, 1971; Nelson and Langeheim, 1974).

The purpose of the present investigation is to determine the biostratigraphic range and écologie controls for the

Middle Pennsylvanian Chaetetes lithotopes of the Hueco

Mountains, Texas and the Northern Franklin Mountains, New

Mexico. This study concentrates on the basic growth forms and growth histories of Chaetetes colonies including obser¬ vations on variations in form, size, orientation, and facies relationships of the colonies. Similar observations are made on Chaetetes colonies from the Lower Pennsylvanian Marble

Falls Formation, Texas. Associated biofabrics, macro¬ organisms, micro-organisms, and epiphytes and epizoans are studied through detailed lithologic decriptions and petro¬ graphic analyses of lithologic samples from the Hueco and Text-figure 1. Index map for the Hueco and Northern

Franklin Mountains. FIGURE L 3 Northern Franklin Mountains to determine micro-facies and faunal/floral relationships of the Chaetetes lithotopes.

Methods of Study Two sections with Chaetetes-bearing units were measured with a Jacob's Staff and were sampled approximately every 1.5 meters or less in order to determine the paleo- environment of Chaetetes. The Northern Franklin Mountains' section was measured in Anthony Gap, Dona Ana County, New Mexico - Texas boundary, instead of at the type locality of the Magdalena Group in Vinton Canyon because of the need for three-dimensional control on the chaetetid growth forms. The Anthony Gap section contains 215 meters of cliff- and ridge-forming of the La Tuna Formation (Morrowan) and the and shale Atoka equivalent of the Berino Formation of the Magdalena Group as defined by LeMone et al. (1976) . The second section was measured on the south side of Pow Wow Canyon in the Hueco Mountains, El Paso County, Texas. This section contains 101 meters of cliff-forming Lower Magdalena Limestone (Morrowan - Atokan) as defined by King et al. (1945). The Magdalena of the Hueco and Franklin Mountains has been given local names even though it is equivalent because of its discontinuous regional outcrop pattern (Harbour, 1972, p. 44). Text-figure 1 gives locality information, and a stratigraphic column is presented in text-figure 2. Sections of the Pennsylvanian Marble Falls Formation in the Llano region, Texas measured by Winston (1963a) and 4

Stitt (1964) were examined and selectively sampled for the purpose of comparing the Chaetetes paleo-environments to those occurring in the Hueco and Franklin Mountains. Two sections on the Cecil B. Smith Ranch, Saline County, Texas measured by Winston (1963a, sections 48 and 49) were surveyed, and Chaetetes outcropping in the Upper Member of the Marble Falls Formation in the Bend area, San Saba County were studied at two sections measured by Stitt (1964, Middle Cherokee Creek Section and Bend Dump Section).

Locality information is given in text-figure 3. Polished slabs and wet acetate peels of approximately 130 rock samples were prepared and examined petrographically. Lithotopes were differentiated by comparing types and relative percentages of matrices, grains, , secondary features, and impurities, and were given rock names based on the Dunham system of carbonate rock classification (Dunham, 1969). The term "lithotope" is used as defined in the American Geological Institute's Glossary of Geology (1974): "an area or surface of uniform sediment or sedimentation; an area of uniform sedimentary environment, or a place distinguished by relative uniformity of the principal environmental conditions of rock deposition (including occurrence of kinds of organisms associated with these conditions)." Analysis of the biological associations and textural aspects of Chaetetes-and non-Chaetetes-bearing lithotopes provides the paleoecologic information necessary for the identification of the environmental controls on Chaetetes distirbutions. Text-figure 2. Generalized stratigraphic sections for

the Hueco and Northern Franklin Mountains. GENERAL STRATIGRAPHY

FRANKLIN MOUNTAINS HUECO MOUNTAINS (LeMone et gl., 1976) (King et gl., 1945)

VIRGILIAN PANTHER SEEP FM UPPER

NVINVA“USNN3d DIVISION DUaiDpÔDUJ

MISSOURIAN DU9|Dp6DUJ dUOlS9UJI| dnojô MIDDLE DES MOINESIAN BISHOP CAP FM DIVISION

ATOKAN BERINO FM LOWER DIVISION MORROWAN LA TUNA FM Text-figure 3. Index map for the Llano region of central Texas, Winston's (1963a) and Stitt's (1964) measured sections are indicated:

MCH - Middle Cherokee Creek Section (Stitt, 1964; see Appendix II) BdD - Bend Dump Section (Stitt, 1964; see

Appendix II) 48 and 49 - Llano River Sections (Winston,

1963; see Appendix II) FIGURE 3^ History of Previous Investigations Taxonomy Chaetetes has interested investigators since it was first reported in the literature by Fischer de Waldheim in Eichwald (1829) because of its value as a stratigraphic tool. Most studies have concentrated on the systematic position of Chaetetes because of the difficulties that arise in determining the level of organization of the simple chaetetid form, a form shared by many groups.

Additional problems in classification are due to the original use of "Chaetetes" and "Tabulata" as catch-all terms for organisms with similar simple forms including bryozoans, stromatoporoids, tetratids, calcareous algae, and tabulates with porous walls (Sokolov, 1962, p. 252). Sokolov (1955, 1962) presents a comprehensive discussion of the history of Chaetetes classification.

In the first report of Chaetetes, Fischer de Waldheim (1829) classified this organism as a zoantharian tabulate. Today most authors place Chaetetes in the tabulate coelenterates; however, chaetetids have been placed in many different classes and orders of coelenterates including

Hexacoralla (Struve, 1898; Neumayer, 1899), Tetracoralla (Bassler, 1950), Alcyonaria (Duncan, 1872; Nicholson, 1879), and Hydrozoa (Koechlin, 1947; Fischer, 1970). Comparable morphologies and paléontologie histories led Sokolov (1939, 1955, 1962) to conclude that chaetetids were a hydrozoan class closely related to stromatoporoids. Okulitch (1936a) 8 established a subclass Schizocoralla for chaetetids, heliolitids, and tetratids; however, this is regarded as an artificial classification (Lustig, 1971, p. 16). Lindstrom (1876, 1899) grouped some chaetetids with hydrozoans and others with bryozoans. Other authors who have classified Chaetetes as are Dollfuss (1875), Zittel (1876) and Peterhans (1929). Most recently Chaetetes has been classified as a Porifera of the class Sclerospongia because of the resemblance of certain of the family Chaetetidae to Ceratoporella nicholsoni (Hartman and Goreau, 1970, 1972) and Merlia normanni (Kirkpatrick, 1911)- Lustig

(1971) disagrees with the Porifera classification because of essential differences between Chaetetes and the sclerosponges in astogenetic development and modes of

skeletal increase; Lustig concludes that Chaetetes is a

tabulate. I recognize Chaetetes as a coelenterate in the tabulate family.

Stratigraphy Chaetetes, first reported from the Middle of the Kuznetsk Basin, Kazhstan, U.S.S.R. (Fischer de Waldheim, 1829), is known from the Middle Devonian through the of Western Europe, European Russia, the Urals, Central Asia, China, Japan, Southwest Asia, the Arctic, and North America. Possible occurrences of Chaetetes in the

Mesozoic were first reported by Haug (1883). Occurrences have been noted in the of Turkey (Cuif and Fischer, (1974) and the of Europe (Peterhans, 1929; 9

Bachmayer and Flugel, 1961; Schnorf - Steiner, 1963) with questionable occurrences in the Eocene (Rios and Almela, 1944). Although Chaetetes has a wide stratigraphic range, the Chaetetes-Profusulinella faunizone is considered a reliable stratigraphic marker of the Atokan in the Great Basin of Nevada and western Utah (Dott, 1954, 1955; Nygreen, 1958, p. 19; Hose and Repenning, 1959, p. 2174; Rich, I960» Douglass, 1960, p. 181; Langenheim et al.,

1960, p. 151; Kellogg, 1960, p. 193; Steele, 1960, p. 99). Only Lane (1960, p. 116) has reported the occurrence of

Chaetetes above the Chaetetes-Profusulinella faunizone in

Nevada. Newell et al. (1953) and Mendivil (1972) have reported Chaetetes in the Fusulinella-Profusulinella Zone in Peru. The occurrence of Chaetetes with the syringoporoid coral Multithecopora hypatiae Wilson is useful in the Great

Basin for Atokan age determinations. Wilson (1963) first described the Chaetetes-Multithecopora association in Dott's Chaetetes-Profusulinella faunizone, and Webster (1969) has reported this association in a middle and upper Atokan-age Fusulinella zone in southern Nevada. The present study found Chaetetes in the presence of Profusulinella in the Hueco Mountains as indicated by stratigraphic correlation with sections by Thompson (1948, p. 71), and in the Northern Franklin Mountains by correlation with Harbour (1972, p. 43-45) and by fusulinid identification (see Appendix II). The Chaetetes-Profusulinella faunizone 10

(Dott, 1955), considered to be a valid time-stratigraphic marker for the lower Middle Pennsylvanian of the Cordillerans, is not extended to the Hueco and Northern Franklin Mountains. It is questionable if the mutual occurrence of Chaetetes and Profusulinella in this region has time-stratigraphic

significance. Chaetetes is found in the Morrowan and Atokan in the Northern Franklin Mountains and ranges from the Morrowan through the Desmoinesian of the Horquilla Formation

to the south in the Palomas Mountains, northern Mexico (Wilson et al., 1969), and in the Desmoinesian of the Jarillo Mountains (Schmidt and Craddock, 1964) , the San Andres Mountains (Kottlowski et al., 1956), the Mud

Springs Mountains (Thompson, 1942) and the Paradox Formation,

San Juan Canyon, southeast Utah (Wengard, 1962, 1963; Pray and Wray, 1963). Further eastward in the Llano

region of central Texas, Morrowan through Desmoinesian Chaetetes have been identified (Plummer, 1950, p. 21, p. 56). Desmoinesian Chaetetes are also known from Illinois (Heritsch, 1933), Indiana and Oklahoma (Lane and Martin, 1966), Kansas (Beede, 1900), and Missouri Keyes, 1894) .

Paleo-environmental Studies Recent studies have concerned the paleo-environmental

aspects of Chaetetes biostromes. The presence of Chaetetes bioherms in the Desmoinesian of the Paradox Formation, Utah was noted by Wengard (1962, 1963). Winston (1963a and b,

1965) concluded that Pennsylvanian Chaetetes in the Llano 11 region of Texas favored surfaces of bypassing and scour of varying depths with a slow accumulation of fine particles on a shallow-water carbonate shelf. Three separate studies of Pennsylvanian Chaetetes biostromes of the Great Basin have revealed additional paleo-environmental information. Chaetetes-bearing rocks are varied, mostly mud- and grain- supported calcarenitic limestones that Rich (1969) inter¬ preted as being "deposited in an environment transitional in depth and energy, and containing the most diverse biotic elements and the most groups." Lustig (1971) enumerated the following environmental parameters; an inter¬ mediate to shallow depth, below wave action, not subject to significant currents, a relatively rapid sedimentation rate and considerable infaunal and epifaunal biological activity. Chaetetes colonies "selectively settled" on hummocks produced by organic activity. Microfacies and faunal analysis of Chaetetes biostromes and autecological studies of Chaetetes by Nelson and Langenheim (1974) indicated

that Chaetetes require a solid substrate, and that the colonies were capable of regeneration if choked by fine sedi¬ ments; however, Nelson and Langenheim were unable to determine any environmental factors restricting Chaetetes distribution. 12

DESCRIPTION OF CHAETETES

General Morphology

The genus Chaetetes Fischer de Waldheim, 1829 is characterized by a massive to lamellar or encrusting skeleton of slender cylindrical or polygonal calcareous tubes. Tube walls are shared by adjacent tubes and contain no mural pores. The tubes are aseptate, approximately equal in diameter, and are characterized by thin, complete or incom¬ plete horizontal tabulae. If complete, the tabulae may appear to be septa (pseudosepta), and may form a meandroid pattern on the skeletal surface. Tabulae do not connect between adjacent tubes, nor are they positioned at the same levels in adjacent tubes. Colonies multiply by longitudinal fission with no later enlargement of the basal surface of the skeleton, and successive growth increments form more or less concentric banding. Text-figure 4 details Chaetetes morphology. Chaetetes skeletons range in size from thin flat lamellar

sheets of several centimeters thickness and length to columnar heads, .3 meters in diameter and reaching heights of 3.7 meters. Due to preferential silicification, Chaetetes commonly appear as rusty-brown, more résistent colonies in

light buff- to grey-weathering calcareous mudstones and wackestones. The term "colony" is used as adapted for paléontologie study by Oliver (1968): Text-figure 4. General morphology and terminology for Chaetetes. FIGURE 4. 14

"individuals must have preservable skeletons that hold together after the removal of soft parts. The nature of the living connections between individuals are not necessarily indicated by the fossil, as such connections can be completely outside the skeletal mass; however, continuity of skeletal tissue itself and the presence of openings between individual skeletons may be suggestive."

Growth Form

Significance of Growth Form The responsiveness of growth forms to prevailing environmental conditions is based on the assumption that: "forms of living things, and of the parts of living things, can be explained by physical considerations, and to realize that in general no organic forms exist save such as are in conformity with physical and mathematical laws."

(D'Arcy Thompson, 1942) Environmentally adaptive growth forms have been well-documented for bivalvia (Stanley, 1971), brachiopoda (Rudwick, 1959), bryozoa (Ryland, 1971), and echinodermata (Nichols, 1969). Coral growth forms and environmental controls have been correlated by Wood-Jones (1907), Boschma (1948, 1958), Mayor (1924) , and Stephanson and Stephanson (1933). Marshall and Orr (1931) and Manton and Stephanson (1935) related coralline growth forms to direct responses of the to sediment movements. Vaughan (1918), Edmondson (1929) and R0os (1967) reported variation in forms due to phototrophic responses; whereas studies by Faurot (1888), Vaughan (1919), Wells (1957), Maxwell (1968), Logan et al. (1969), and Rosen

(1971) indicated that water turbulence and circulation are 15 major morphologie controls. Recent investigations by Braithwaite (1973), Hubbard (1970, 1974a and b), Hubbard and Pocock (1972), and Garret et al. in Zankl and Schroeder (1972) have revealed that the use of coralline growth forms as indicators of specific environments may be an oversimplification. Several factors are shown to be effective in controlling coral morphology including water movement, the availability of nutrients, light distribution, and the adverse effects of salinity, temperature and suspended sediments. Hubbard and Pocock's study (1972) indicated that growth form is not only responsive to these factors with regard to the colony's écologie position and orientation on the sea floor, but also with regard to the distribution of polyps within the colony. Additional caution must be taken to determine the relative in importance of genetic control versus environmental control over growth form (Hubbard, 1970, 1972, 1974a and b; Hubbard and Pocock,

1972). As Wells reported (1957, p. 1088-1089): "Some species show little plasticity of form and each is indicative of a certain écologie niche. Others are highly plastic and may be found in a variety of situations, in each case showing a form adapted not only to survival but for successful competition with other organisms." By cautiously comparing growth forms by locality and by using sedimentologic criteria, studies of colony morphologies can be effective in determining paleo-environmental controls.

Chaetetid Growth Forms As reported by Lustig (1971, p. 48), the basic 16 chaetetid geometry is a function of the ratio between the maximum rate of vertical growth along the central axis of the colony and the lateral growth rates that decrease in value towards the periphery of the colony. Two growth forms, based on this geometry, are exhibited by the Chaetetes colonies observed in the present investigation; these are termed shingle forms and club forms. The shingle form chaetetid is characterized by numerous increases or decreases in the width of the upward-growing colony (text-figure 5; plate 1). These changes in diameter occur at distinct, often silicified, growth discontinuities that are readily apparent in cross-sectional view in the field. This banding gives the shingle-form colony the aspect of having several individual packages of growth increments of varying dimensions stacked upon one another. Shingle- form Chaetetes grow upward and outward from small flat encrusting forms approximately 10 centimeters in diameter and 1 to 2 centimeters in height to form large anastomosing complexes several meters in diameter and approximately one meter in height (text figure 6; plates 2 and 3). This growth form adapts readily to an encrusting growth mode; it has been observed encrusting solitary rugose corals that had settled within a large Chaetetes complex (text-figure 7).

Shingle-form Chaetetes are associated with foraminiferal and algal wackestone-packstones in the Hueco and Northern Franklin Mountains. Growth banding is virtually indistinguishable in the field in club-form Chaetetes. Club-form Chaetetes emphasize Text-figure 5. Shingle growth forms of Chaetetes: A. shingle-form evidencing increases and decreases

in width and prominent growth discontinuitites. Drawn from photograph of Chaetetes at 66 meters,

Northern Franklin Mountains section.

B. initial lamellar form. Drawn from photograph of Chaetetes at 9 meters, Northern Franklin Mountains section. SHINGLE-FORM CHAETETES

40 centimeters

20 centimeters

FIGURE 5. Text-figure 6. Shingle-form Chaetetes form large anastomosing complexes, Drawn from photographs of Chaetetes at: a. 65 meters, Hueco Mountains section

b. 63 meters, Northern Franklin Mountains section FIGURE 6. Text-figure 7. Rugose coral encrusted by Chaetetes,

Hueco Mountains section, 40.6 meters. CHAETETES- ENCRUSTED

chaetetes rugosa—

2 centimeters 20 growth along the vertical central axis, and show only subtle changes in width. Major growth discontinuities are occasionally visible, though they are rarely silicified (text-figure 8). Chaetetes clubs range in size from less than one meter up to 3.7 meters in height and from .5 to 1.5 meters in diameter (plate 4). Within a lithologic unit, they are commonly found in groups of three or four solitary clubs or in clusters of 20 or more colonies (plate 5). This growth form is associated with laminated bioclastic mudstone-wackestones. A nodular form of Chaetetes was also observed; however, these appear to be skeletons that have been rounded by reworking on the sea floor. Nodules of Chaetetes occur in coated grainstones.

As reported by Nelson and Langenheim (1974), Chaetetes is capable of regeneration. Micro-scale and macro-scale regeneration can be observed (text-figure 9). If growth is terminated because of an injury to a small area of the colony, the adjacent corallites will repair the damaged portion of the skeleton by growing over that portion of the skeleton. Clubs overturned by periodic high-energy water movement are capable of regeneration, and several small colonies may "branch" from the large overturned colony.

Growth Banding

Growth bands in invertebrate skeletons are physical markings of periodic growth processes. Researchers have related these bands to several biological controls including Text-figure 8. Club growth form of Chaetetes« A. Major growth discontinuities are not

silicified, but are distinguished by color changes. Drawn from photograph of Chaetetes in Bend Dump section. B. Large clubs evidence only subtle changes in

width. Growth along the vertical axis is

emphasized. Drawn from photograph of Chaetetes at 118.5 meters, Northern Franklin

Mountains section. FIGURE 8. Text-figure 9. Regeneration in Chaetetes. Microscale: growth and repair of skeleton by corallites adjacent to injured tubes. Chaetetes from Llano River section.

Macroscale: clubs "branching" from large

over-turned head. Chaetetes at 118 meters, Northern Franklin Mountains section. REGENERATION

MICROSCALE

MACROSCALE 23 well-defined seasonal reproductive cycles under lunar

influence (Davenport, 1938; Korring, 1957; Thorson, 1950; Craig and Hallam, 1963; Wells, 1963; Barker, 1964; Scrutton,

1964; Clark, 1968; Hose and Farrow, 1968; Pannella and MacClintok, 1968; Yonge, 1969), temperature factors (Ma, 1937; Farrow, 1972; Hudson et al. 1976), and nutrient supply (Wells, 1963). Lustig (1971) presents a comprehensive discussion of growth banding in Chaetetes with which observations on

chaetetid growth banding in the present study generally coincide. She concluded that: 1) Chaetetes lack external evidence of growth

banding because their skeletons have no epithecal covering which is where growth banding is usually exhibited in rugose corals. 2) Each band is parallel to the external shape of

the colony and is perpendicular to the direction of growth. 3) Alternating light and dark color bands are

regularly spaced and have the same average thick¬ ness of 2 mm at all localities. 4) Light color bands contain numerous tabulae giving

a lighter aspect than a virtually tabula-free dark color increment. 5) Light color bands indicate minimal accretion; dark color bands indicate faster accretion. 24 Lustig defines a growth band as consisting of a dark and a light color layer, with each growth band consisting of 10 to

13 fine laminae. She postulates that the color differences are related to the spacing of growth laminae with the crowding of laminae giving the appearance of one thick, light-colored layer, and the more widely spaced laminae affecting a darker coloration. Lustig was unable to determine the origin of the differential color banding, and postulated that color differences may reflect primary differences in skeletal material related to varying organic content or crystal structure. The present study notes that although alternating light and dark bands are present in all colonies, this affect is best observed in polished slabs. Often in hand specimen, only major discontinutites or silicified bands can be discerned. Shingle-form Chaetetes characteristically contain

regularly-spaced dark and light bands. Major changes in the shape of these colonies are commonly marked by silicified growth bands or by distinct dark bands. Club-form Chaetetes appear to have abnormally thick dark bands (4 cm or more) and contain few major discontinuities. A comparison of growth banding in the two growth forms is presented in text-figure 10.

Interpretation of Growth Forms

Chaetetes appears to have a limited number of growth form responses. The author disagrees with Lustig (1971, p. 45) who concluded that the external factors in growth

determination were minimized by the relatively quiet-water Text-figure 10. Comparison of growth banding in shingle- form and club-form chaetetids.

Shingle-form Chaetetes have regularly spaced growth bands (A) composed of 2mm thick dark (1) and light (2) color layers. A major change in the width of the colony appears to coincide with the development of a major growth discontinuity (B). The growth bands (A) in club-form Chaetetes are also composed of alternating dark (1) and light (2) color layers; however, dark color layers may be as thick as

4cm (3). Major growth discontinuities (B) are more regularly spaced and do not necessarily signal changes in the width of the colony.

26 environment where the Chaetetes colonies lived. Instead, the limited growth responses appear to be functions of the two fundamental growth form controls; intraspecific variation and plasticity of growth form. Intraspecific variation results from the genetic control potential of an organism. Chaetetes, a colonial organism, was a clone consisting of a founding individual and a number of asexually produced daughter individuals that had not separated from each other (as defined by Oliver, 1968, p. 16). The resulting lack of genetic variation within the Chaetetes colony resulted in a limited genetic response to varying environmental conditions. The plasticity of the chaetetid growth form appears to have been controlled primarily by the nature of the polyp- skeleton system, and secondarily by local environmental factors influencing polyp distributions. The concept of the closed-system colony versus the open-system colony as defined by Hubbard (1972) provides a model for interpreting chaetetid growth forms. In a closed-system colony, the abundant organic tissues and their secretions act as powerful buffers at the micro-environmental level, so that the internal skeleton is isolated from the external marine environment. Skeletal growth of closed-system corals records only major or seasonal environmental changes. The tissue-clad colony of Porites furcata (Lamarck) is an example of such an enclosed system. In contrast, a coral colony such as Eusmilia fastigiata (Fallas) with minimal tissue development is an example of 27 an open system. Due to the 'nakedness' of its skeleton, this colony is more sensitive to micro-environmental and even to ephemeral changes in the environment that may be recorded daily or even hourly in the numerous skeletal growth episodes.

Without the natural buffers of the closed-system tissues, the 'naked' systems are also open to greater encrustation and bioerosion. Text-figure 11 contrasts with the open- versus the closed-skeletal systems.

The thin, contiguous tubes of the Chaetetes skeleton are indicative of a closed-system colony. Internally, Chaetetes are characterized by rhythmic growth banding and periodic growth discontinuities. These features are con¬ sistent at all localities and for different depositional environments. This similarity in basic internal form does not appear to be related to a quiet-water environment, but to the buffering effects of the polyps covering the skeleton. Only major or seasonal changes in environmental factors such as mechanical water movement, light distribution, nutrient availability, and salinity and temperature should be reflected in the chaetetid skeleton. The abundant, widely spaced growth discontinuities in shingle-form Chaetetes suggests that these forms were sub¬

jected to frequent and/or severe seasonal or catastrophic environmental fluctuations; whereas, the absences of numerous growth discontinuities in club-forms may reflect greater stability in the water column with respect to time. Regularly spaced, 2 mm growth bands found in both growth forms are probably a function of periodic, possibly lunar-influenced, Text-figure 11. Enclosed-versus open-skeletal systems. Porites furcata, characterized by closely spaced corallites, exemplifies the enclosed skeletal system. The internal skeleton is buffered from

the external marine environment by organic

tissues.

Eusmilia fastigiata, with widely spaced corallites, is an open skeletal system. Without organic tissues enclosing its skeleton, the marine

environment and the internal skeleton are in constant contact ENCLOSED SKELETAL SYSTEM

ASk

WBm,iV& M&*

Porites furcoto VQpipi

OPEN SKELETAL SYSTEM

fostiqiato

L5cm

FIGURE II, 29 growth or reproductive cycles. Wider dark growth bands, characteristic of club forms suggest the possibility of prolonged conditions favorable to growth or prolonged conditions encouraging more rapid growth. Lustig (1971, p. 51-55) calculated absolute time values for the growth bands by comparing chaetetid growth band measurements with known Recent and fossil coral growth rates. She concluded; "an average annual value of 2 mm of yearly growth in a massive, non-reef-building coral like Chaetetes falls within reasonable known ranges. The presence of 10 to 13 growth laminae probably representing approximately of lunar month's growth." Greater variability in Chaetetes' external form compared to its internal form may be a function of the polypal response to local environmental controls. Hubbard and Pocock (1972) related two local environmental controls to the distribution patterns of polyps within a colony in Holocene Caribbean and Western Atlantic coral species:

1) the positive factor - competitive growth control is determined by the polyp's competence at

filtering the content of the water. 2) the negative factor - (survival factor), the

polyp's ability to extract itself from the

'smothering* effects of offending sediment and excrement. Hubbard and Pocock found that hemispherical growth forms are the only forms exposing all polyps to a uniform food supply, illumination and current strength. Polypal distribution on club-form Chaetetes closely approaches the hemispherical 30 form; whereas, polypal orientation on shingle forms more

closely approaches a horizontal plate. The above consid¬ erations lead to the interpretation that club-form Chaetetes were subjected to more uniform environmental conditions than were the shingle forms. One can speculate that the club-forms were living in deeper, less current- and wave-agitated portions

of the shelf and were subjected to equal illumination, current- strength and food supply. Growth-form distributions of the Holocene scleractinian coral Montastrea (Wilson, 1975, p. 73) appear to contradict

the present study's findings for chaetetid growth form distributions. Massive hemispherical forms of Montastrea are found in depths greater than 10 meters but less than

30 meters, and sheety forms are found in deeper darker waters below 30 meters. If hemispherical forms are indicative of

uniform illimination, nutrient supply and current strength, the sheety forms are adaptations to less than ideal conditions. As upwelling is intense along present day fore-reefs, and would provide water agitation as well as a nutrient supply, the sheety form is probably an adaptation to receive optimum

illumination. It can be inferred that there was no upwelling in the basin inhabited by the Chaetetes as there is no evidence of a shelf break. In an environment with high organic productivity and good illumination, waters with poor circulation would soon develop anoxic conditions on the sea floor. Vertical elongation of the central axis of club-form Chaetetes suggests that chaetetids were attempting 31 to escape the inhospitable, poorly oxygenated conditions of the sea floor. Shingle forms may have adapted to their plate-like form in an attempt to improve their stability in those well-illuminated portions of the shelf with greater mechanical water movement. 32

ECOLOGIC CONTROLS OF CHAETETES GROWTH AND DISTRIBUTION

Lithotope Relationships

Study of the Chaetetes-bearing units of the Hueco and

Northern Franklin Mountains sections reveals that Chaetetes is associated with four lithotopes; encrusted phylloid algal wackestones, tubular Pspecies packstones, Cuneiphycus packstones, and laminated bioclastic mudstone-wackestones

(text-figure 12). These units were compared to the non- Chaetetes-bearing lithotopes and sedimentary structures and fossil constituents diagnostic of Chaetetes-bearing lithotopes were noted, resulting in the delineation of physical and biological factors that may have controlled Chaetetes dis¬ tributions. Lithotope descriptions and their environmental

implications are given in Appendix I. The biologic law of minima and maxima that governs

Recent scleractinian coral distribution patterns appears applicable to Chaetetes distribution. This law states that "the key distribution patterns are influenced by the limi¬ tations of extremes rather than an admixture of tolerable conditions" (Hubbard, 1974a, p. 122).

Physical Environment

Depth and Water Movement

Chaetetes are excluded from high-energy shoals and deeper waters with sluggish circulation. Chaetetes in growth position are absent from oolitic grainstones, osagid Text-figure 12. Chaetetes-bearing lithotopes. For legend,

refer to Appendix II.

1) Shingle-form Chaetetes at the base of an encrusted

phylloid algal wackestone. Northern Franklin

Mountains section, 6 to 18 meters.

2) Tubular ?species wackestone-packstone with

associated pelleted foraminiferal wackestone-

packstone contains shingle-form Chaetetes.

Underlain and overlain by tubular ?species foraminiferal

wackestone-packstone. Northern Franklin

Mountains section at 60 meters.

3) Club-form Chaetetes up to one meter in height

are contained in a laminated bioclastic mudstone-

wackestone. A unit of rounded and abraded Chaetetes

is found in the overlying abraded bioclastic

wackestone-packstone. Northern Franklin Mountains

section at 114 meters.

4) Rounded nodules of Chaetetes are contained in the

osagid grainstone. Shingle-form Chaetetes are

found at the base of an encrusted phylloid algal

wackestone. Hueco Mountains section, 36 to 39

meters. 5) Pelleted foraminiferal wackestone-packstone

contains rounded nodules of Chaetetes. Encrusted phylloid algal wackestones with shinglë-form Chaetetes form the flanking beds of a phylloid

algal mound composed of phylloid algal wackestone-

packstones. Hueco Mountains section, 48 to 51 meters. 6) Shingle-form Chaetetes in the top of an encrusted

phylloid algal wackestone-packstone are also found in the base of the overlying Cuneiphycus packstone and calcitornellid packstone-grainstone. Hueco Mountains section, 69 to 72 meters. 7) Cuneiphycus packstone contains small shingle- form Chaetetes near the top of the unit.

Northern Franklin Mountains section, 63 to 65 meters. CHAETETES-BEARING LITHOTOPES

7TT 1 1 encrusted , 1 phylloid algal wackestone 7TT r i

osagid grainstone VV>g7>

encrusted phylloid 1,1, algal wackestone

phylloid algal wkstn - pkstn

encrusted phylloid ^Pf oelleted foram atSjtJ

calcitornellid pkstn - gnstn tubular ?species VF~R (& pelleted foram) (Cuneiphvcus pkstn) wackestone - i \*-T- encrusted phylloid packstone crinoidal pkstn - JrJ L gnstn 6.

Cuneiohycus abraded bioclastic packstone wkstn - pkstn x=i tubular ? species y ■Mr1 1 laminated rzI wkstn - pkstn bioclastic l&âs; wkstn - pkstn itf-fej 3. - 3 meters

FIGURE 12. 34 grainstones, and archeolithophyllid grainstones. These units contain occasional rounded Chaetetes heads and may contain Chaetetes debris beds. Oolitic grainstones form today on oolitic shoals in waters less than two meters deep at Brown Cay, Bahamas (Bathurst, 1971, p. 316). These shoals are high-energy environments that are subjected to daily tidal currents and waves and frequent storm activity. Osagid-type and archeolithophyllid-type coated grains also indicate relatively shallow, current-agitated shoaling environments (Toomey, 1969).

Other organisms that typify a shallow-water carbonate platform are associated with Chaetetes. Codiacean phylloid algae are diagnostic of shallow wave-sheltered environments.

Because of the nature of their broad calcareous bladed leaves, they probably could not have withstood current and wave agitation (Konishi and Wray, 1961; Wray, 1962; Heckel and Cocke, 1969; Toomey and Winland, 1973; Toomey, 1969, 1976) and were rarely preserved with articulated thalli

(text-figure 13). Recent codiacean algae and Thalassia are known to grow in wave-sheltered troughs between oolite shoals (Bathurst, 1971, p. 316). Dense thickets of Cuneiphycus, a calcareous red alga similar in form to phylloid algae, also characterize the carbonate platform biota. Preserved specimens of this delicately branched and segmented plant are commonly articulated suggesting that Cuneiphycus may have inhabited a zone well below normal wave agitation (Toomey, 1969, p. 1315). Intricate networks of tubular organisms are a Text-figure 13. Substrate colonizers. Phylloid algae - commonly grew in dense thickets and mounds on the sea floor with associated encrusters, grazers and those organisms that could live in their shadows. Phylloid algae

trapped muds, stabilizing the sea floor. Tubular organisms - formed delicate chains and

networks that covered the sea floor and were capable of trapping muds. PHYLLOID ALGAE

(modified from Toomey, 1976)

TUBULAR ORGANISMS

FIGURE 13. 36 third group that colonized and dominated the sea floor

(text-figure 13). These organisms probably cemented themselves to the substrate or clung to the substrate in a manner similar to benthonic foraminiferids (Murray, 1973, p. 218). In the sections measured, smaller rugose solitary corals appear to prefer intermittent phylloid algal troughs, indicating that Chaetetes may have required slightly greater depths than those required by the Rugosa. Rugose corals are commonly overturned, whereas most Chaetetes are in growth position suggesting that both corals were subjected to periodic high-energy wave motion. Most non-fusulinid smaller foraminiferids and millerellids associated with Chaetetes have broad distributions on shallow-water carbonate platforms and give little specific paleoecologic information (Toomey, 1972; Toomey and Winland, 1973). The basinward limit of Chaetetes distribution appears to be a function of water circulation rather than of depth. The low abundance and low diversity of normal marine organisms and the presence of pyritized fossils in the laminated biolcastic mudstone-wackestones suggests slightly reducing conditions resulting from stagnant, poorly oxygenated water. Relatively quiet water is indicated also by the occurrence of the opthalmid-calcitornellid foraminiferid consortium. Recent opthalmids occur in relatively quiet water in depths ranging from 7 meters in the backreef of the Florida Reef Tract to 40 meters in the reef foreslope (Moore, 1957). The presence of fusulinaceans in this lithotope suggests a deep, 37 open-water environment (Thompson, 1964). Chaetetes probably required a certain degree of water circulation to aid in the removal of potentially suffocating wastes and sediments, and would not have been able to survive under prolonged conditions of stagnation on the sea floor.

Light Chaetetes apparently preferred well-illuminated waters. Association with abundant and diverse algal floras that require light for photosynthetic activity indicates that Chaetetes lived within the photic zone. The absence of green algae from some of the Chaetetes-bearing lithotopes suggests that Chaetetes may have lived within the lower limits of the photic zone. Precise depths cannot be given because of the differing light requirements of red, green and blue-green algae, and because the depth range of the photic zone may vary considerably depending on the turbidity of the water column and latitude. If Chaetetes were hermatypic corals, they would have contained symbiotic algae, zooxanthellae, that would have required their living in the photic zone. Encrusting foraminiferids also are diagnostic of a depositional setting within the photic zone. Plano-convex and discoidal foramini¬

ferids, preserved as free specimens, characteristically encrusted marine grasses or algae (Henbest, 1958; Murray, 1973; Toomey and Winland, 1973; Toomey, 1969, 1972, 1976;

Frost and Langenheim, 1974). Frost and Langenheim report that these foraminiferids may contain zooxanthellae which would further necessitate their living in the photic zone. 38

Turbidity The absence of silicic clastic deposits and the presence of normal marine limestones suggests that Chaetetes grew in clear water. Non-turbid water is requisite for calcium carbonate precipitation. A large-scale or prolonged influx of clay- or silt-sized silicic particles into the depositional environment would have been detrimental to the polyps, clogging their feeding systems. Large club-shaped Chaetetes are found in the Brownwood Shale, Brownwood, Texas, a shale that supports abundant filter-feeders such as , rugose, corals, and bryozoans (Wilson, 1976, personal communication). The presence of these organisms in such abundance may have helped to cleanse the water of much of the

suspended detrital materials, preventing clogged feeding systems.

Salinity

Chaetetes lived in waters of normal marine salinity.

None of the organisms associated with Chaetetes typify hypersaline or fresh water-conditions.

Organic Productivity

Corals need a partial diet of zooplankton to supplement the nutrients supplied by symbiotic zooxanthellae (Hubbard, 1974a); thus, it would be advantageous for Chaetetes, whether,

or not it contained zooxanthellae, to live in waters with high organic productivity. Chaetetes-bearing lithotopes

contain abundant benthonic foraminiferids which according to 39

Murray (1973) indicates high productivity.

Nature of the Substrate Although corals today require a solid substrate for colony initiation (Edmondson, 1929; Hubbard, 1974a), Paleozoic corals lived freely on muddy substrates (Hubbard, 1974 a, p. 618; Wells, 1957, p. 773). Nelson and Langenheim (1974) concluded that a solid substrate is essential for Chaetetes growth. The present investigation found evidence for

Chaetetes preferring stabilized substrates. The basal sections of Chaetetes are usually plano-convex indicating a preference for places on the sea floor with subtle relief. Lustig (1971, p. 84-94) postulated an organic origin for sub-corallum mounds. She suggested that sediment-binding organisms, possibly algal mats, produced the hummocky topo¬ graphy on which Chaetetes "selectively settled." The present investigation found no evidence of algal mats; furthermore, hardened algal mats are restricted to intertidal zones. The external mound surface of the Chaetetes studied commonly was outlined by large encrusting foraminiferids. In other places

Chaetetes were attached to such solid surfaces as cephalopod shells and rugose corals. Sub-mound surfaces are illustrated in text-figure 14. An additional indication of Chaetetes1 preference for stable substrates is the exclusion of Chaetetes from grainstone lithotopes. Grainstones were deposited on a rapidly shifting sea floor. Text-figure 14. Submound surfaces. Small shingle-form chaetetid encrusting fragment of ?cephalopod shell and encrusting foraminiferid. (Sample from Hueco Mountains section; x 1.5). ENCRUSTING F0RAM1NIFERID

CEPHALOPOD SHELL 41

Geomorphology of the Sea Floor

Although individual colonies apparently required a hummocky topography, there is no evidence of larger scale topographic relief on the sea floor beneath groups of Chaetetes. A mechanism similar to the one postulated by

Hubbard (1974a, p. 117; 1974 b, p. 145) for patch reef development may be responsible for the clumping of Chaetetes. The corals themselves influence the hydrodynamic setting, maximizing the irregular topography of the sea floor, and result in the development of monospecific mounds. In the Hueco Mountains section, at 48 meters, Chaetetes were found flanking a phylloid algal mound. This occurrence appears to be controlled by the biological environment and not the physical setting. For further discussion of this case, see the following section on biological environment. For a reconstruction of the sea floor, see the conclusions and especially text-figure 15.

Stability of the Environment Environmental stability promoted more rapid growth in Chaetetes. Growth bands in Chaetetes apparently reflected major fluctuations in environmental conditions. Lustig (1971, p. 76) postulated that major growth discontinuities may have been caused by mass mortality corresponding to plankton blooms initiated in nutrient-rich waters at low- latitudes during unusually warm weather. The present investigation found no preserved evidence of plankton blooms, associated faunas and floras are diverse. Text-figure 15. Idealized reconstruction of a shallow carbonate shelf showing Chaetetes distributions

(in black) and lithotope relations. FIGURE 15. 43

Fine laminations and discrete zoophycus-type burrows associated with the lithotopes containing club-form Chaetetes are evidence of slow sedimentation rates. At the Bend Dump section, feeding tracks and trails are especially obvious. In contrast, shingle-form Chaetetes-bearing lithotopes contain homogeneous, commonly massive beds. These units are pelleted, well-churned and lack discrete burrows. Either a more constant food and nutrient supply and/or more constant temperatures are expressed by the rare, periodic growth discontinuities in club-form Chaetetes, compared to the numerous growth discontinuities in the shingle-form Chaetetes.

Biological Environment The diverse and abundant benthos occurring in Chaetetes- bearing lithotopes typify the 'normal* marine biota of a late Paleozoic shallow-water carbonate platform (Toomey and

Winland, 1973; Toomey, 1969, 1972, 1976; Winston, 1963a). These organisms also occur in non-Chaetetes-bearing lithotopes, and generally give little specific paleoecologic information. Organisms associated with each lithotope are summarized in Appendix I.

Mutualism

Caninostrotion(?) and Multithecopora hypatiae, reported to be intimately associated in the Bird Spring Formation, southern Nevada (Lustig, 1971) were observed in the Lower Marble Falls Formation, Texas. Multithecoporids and Chaetetes are mutually exclusive in the Northern Franklin Mountains 44 section and are absent from the Hueco Mountains section. Chaetetes and solitary rugose corals are found together in both sections. The present investigation agrees with Lustig that these coral associations are not symbiotic relationships; instead, the corals have similar environmental requirements. Rugose corals and Chaetetes often occur exclusive of one another, with the rugose corals occurring at slightly shallower depths than Chaetetes and Chaetetes occurring at greater depths than the rugose corals. All four coral types, Caninostrotion(?), multithecoporids, rugose corals and Chaetetes, apparently used one another as stable substrates when necessary, without detriment to the host coral.

Because of the enclosed nature of the Chaetetes skeleton, it is most likely that Chaetetes was encrusted at the site of dead corallites or by post-mortem infestation of the skeletons exposed on the sea floor.

Borings and encrustations other than those by the previously mentioned corals are rare in Chaetetes. Okulitch

(1936) reported a "parastitic" spiral annelid embedded in a Chaetetes skeleton; however, none were found in the

skeletons examined. ?Vermetid tubes and foraminiferid

encrustations rarely were found on the bases of shingle-form Chaetetes (text-figure 14). These organisms appear to have

used Chaetetes as a stable support for growth.

Competition

Chaetetes distribution appears to be based on competition for substrate space. This is evidenced by the interaction of 45

Chaetetes with phylloid algae, Cuneiphycus, and tubular organisms. As evidenced in text-figure 12, Chaetetes flank phylloid algal mounds and are restricted to the bases of encrusted phylloid algal, Cuneiphycus and tubular ?species lithotopes. All of these organisms require a stabilized substrate for attachement. The shorter life cycles of the phylloid algae, Cuneiphycus and tubular organisms enable these organisms to expand rapidly and dominate the sea floor. As described by Toomey (1976) for a phylloid algal community, once the plant growth has completely overshadowed the sub¬ strate, a plant-oriented and plant-controlled community evolves, cohabited only by epiphytes, epizoans, browsers and nibblers...

"those organisms that could live on, live within, or live under a plant umbrella would be able to

successfully compete and survive the span of their potential life spans." Chaetetes larvae would no longer be able to settle on the stabilized substrates, and the already established juvenile Chaetetes would be unable to keep pace with the prolific growths of the other organisms on the sea floor. 46 CONCLUSIONS

Chaetetes occurs with Profusulinella in the Hueco and

Northern Franklin Mountains, and is found in the Morrowan and Atokan in the sections measured. Eastward in the Llano region, Chaetetes is found in the Morrowan, Atokan and Desmoinesian.

Two chaetetid growth forms with apparent écologie significance are noted: shingle-form Chaetetes and club-form Chaetetes. Shingle-forms are characterized by prominent increases and decreases in width, and have common, erractically spaced growth discontinuities. Large anastomosing complexes of shingle-form Chaetetes are associated with phylloid algal, Cuneiphycus and tubular ?species wackestone-packstone lithotopes. These units are commonly massive and are burrow- mottled. Club-forms emphasize growth along the vertical axis, showing subtle changes in width associated with regular, periodic growth discontinuities. Clusters of two to four club forms are found in the discretely burrowed, laminated bioclastic mudstone-wackestone lithotope. An idealized reconstruction of Chaetetes distributions on a shallow-water carbonate shelf is possible based on the relative stratigraphic positions of the lithotopes, and on inferred physical and biological environmental parameters

(text-figure 15). Precise distributions of most faunal and floral constituents cannot be determined because most of the organisms are not sediment-dwelling and are therefore prone to post-mortem transport. Chaetetes lived in clear, warm. 47 well-illuminated shallow waters on carbonate platforms. These waters were moderately to highly productive containing an abundant and diverse assemblage of benthonic organisms.

Chaetetes were restricted from high-energy shoals that pro¬ duced coated grainstones, and from low energy, poorly oxygenated deeper waters within the lower limits of the photic

zone that resulted in anoxic bottom conditions. Shingle-form Chaetetes were common across the shallow portions of the

shelf where their broad, plate-like forms prevented their overturning in the current- and wave-agitated waters. This growth form thrived where sea grasses, red and green

calcareous algae and tubular organisms were capable of trapping and stabilizing the sediments. Shingle-forms were excluded from areas of only sparse growths of these organisms were

unable to stabilize the sediments, and from places where the

sediment-trapping organisms grew in great profusion and

monopolized the sea floor. Club-form Chaetetes may have been

restricted to deeper, less turbulent waters where more stable physical conditions prevailed. REFERENCES

American Geological Institute, 1973. Gary, M., McAfee, R., Woof, C. L., (editors): Glossary of Geology, Washington, D. C., 805 p. Bachmayer, F. and Flugel, E., 1961. Die "Chaetetiden" aus dem Ober-Jura Ernstbrunn (Niederosterreich) u. Stramberg (C.S.R.), Paleontographica, 116:144-174. Bassler, R.S., 1950. Faunal lists and descriptions of Paleozoic corals. Geol. Soc. Am., mem. 44, 315 p. Barker, R.M., 1964. Microtextural variation in pelecypod shells. Malacologia, 2z69-86.

Bathurst, R.G., 1971. Carbonate sediments and their diagenesis. Developments in Sedimentology 12, Elsevier Publishing Co., 620 p. Boschma, H., 1948. The species problem in Millepora. Rijksmus. Nat. Hist., Leiden, Zool. Verhandl. no 1:115.

Braithwaite, C.J.R., 1973. Reefs; just a problem of semantics? Am. Ass. Petr. Geol., Bull 57 (6):1100-1116. Clarke, G.R., III, 1968. Mollusc shell: daily growth lines. Science, 161:800-803. Craig, G.Y. and Hallam, A., 1963. Size frequency and growth-ring analyses of Mytilus edulis and Cardium edule and their paleoecological significance. Palaeontology, 6:731-750.

Cuif, J.P. and Fischer, J.-C., 1974. Etude systématique sur les Chaetetida du Trias de Turque. Ann. Paleontol., Invertébrés,: 60 (1):3-14. Davenport, D.B., 1938. Growth lines in fossil pectens as indicators of past climates. Jour. Paleo., 12:514-515. Dollfüss, M.G., 1875. Observations critiques sur la classifications des polypiers paléozoïques. Compt. Rend. Acad. Sci. 80. Dott, R.H., Jr., 1954. Chaetetes, important marker in Pennsylvanian of central Great Basin (abstr,). Geol. Soc. Am. Bull., 65:1245-1246. Dott, R.H., Jr., 1955. Pennsylvanian strata of Elko and northern Diamont Ranges, northeastern Nevada. Am. Assoc. Petr. Geol., Bull. 39:2211-2305. Douglass, W.B., Jr., 1960. Geology of the Southern Butte Mountains, White Pine County, Nevada, in; Guidebook to the Geology of East Central Nevada, J. W. Boettcher and W. W. Sloan, Jr., (editors):181-185. Duncan, P.M., 1872. Third report on the British Fossil Corals. Rept. Brit. Assoc., 41:116-137. Dunham, R.J., 1962. Classification of carbonate rocks according to depositional texture. In; Classification of carbonate rocks, W. E. Ham (ed.), Am. Assoc. Petr. Geol., mem 2:108-121. Edmondson, C.H., 1929. Growth of Hawaiian corals. Bull. Bishop Mus. Honolulu, 53:1-38. Eichwald, C.E. von, 1829. Zoologia specialis quam expositis animalibus turn vivus, turn fossilibus potissimum rossiae in universum, et poloniae in specie, in usum letionum... (Vilna), 1:1-314. Farrow,, 1972. Periodicity structure in the bivalve shell: Analysis of stunting in Cerastoderma edule from the Berry Inlet (South Wales), Palaeont., 15:61-72. Fischer, J.-C., 1970. Revision et essai de classification des Chaetetida (Cnidaria) post-paléozoiques. Ann. Paleontol. Invertébrés, 56:149-233. Freeman, T.J., 1962. Carboniferous stratigraphy of the Brady area, San Saba and McCulloch Counties, Texas. Unpublished Ph.D. dissertation, Univ. Texas, 219 p. Frost, S.H. and Langenheim, R.L., Jr., 1974. Cenozoic reef biofacies - Tertiary larger foraminifera and scleractinian corals from Chiapas, Mexico. Northern Illinois University Press, DeKalb, Illinois, 388 p. Harbour, R.L., 1972. Geology of the Northern Franklin Mountains, Texas and New Mexico, U. S. Geol. Survey, Bull. 1298:1-129. Hartman, W.D. and Goreau, T.F., 1970. Jamaican coralline sponges: their morphology, ecology, and fossil relatives Symp. Zool. Soc. London, no. 25:205-243. Hartman, W.D. and Goreau, T.F., 1972. Ceratoporella (Porifers: Sclerospongiae) and the chaetetid "corals". In: Growth by Intussusception, Ecological Essays in Honor of G. Evelyn Hutchinson, E. S. Deevey (ed.) Conn. Acad. Arts and Sciences Trans. 44:133-148. Haug, E., 1883. Uber sogenannte Chaetetes aus mesozoischen ablagerungen. Neues Jahrbuch f. Minéralogie, 1:171-179. Heckel, P.H. and Cocke, J.M., 1969. Phylloid algal mound complexes in outcropping Upper Pennsyvlanian rocks of mid-continent. Am. Ass. Petr. Geol., Bull 53: 1058-1074.

Henbest, L.G., 1958. Ecology and life association of fossil algae and foraminifera in a Pennsylvanian limestone, McAlester County, Oklahoma. Contr. Cushman Foundation Foram. Res., j): 104-111. Hose, R.K. and Repenning, C.A., 1959. Stratigraphy of Pennsylvanian, , and lower Triassic rocks of Confusion Range, west-central Utah. Am. Assoc. Petr. Geol., Bull. 42:2167-2196. Hubbard, J.A.E.B., 1970. Sedimentological factors affecting the distribution and growth of Visean caninoid corals in North-West Ireland. Palaeont., 13:191-209. Hubbard, J.A.E.B., 1972. Cavity formation in living scleractinian reef corals and fossil analogues. Geol. Rundsch. 61:551-564. Hubbard, J.A.E.B., 1974a. Scleractinian coral behaviour in calibrated current experiment: an index to their distribution patterns. Proceedings of 2nd International Coral Reef Symposium. Great Barrier Reef Committee, Brisbane, 2:107-126. Hubbard, J.A.E.B., 1974b. Coral colonies as micro¬ environmental indicators. Ann. Soc. Geol. Belgique, 97(1) .-143-152.

Hubbard, J.A.E.B. and Pocock, Y.P., 1972. Sediment rejection by recent scleractinian corals: a key to paleoenvironmental reconstruction. Geol. Rundsch., 61(2): 598-626. Hudson, J.H., Shinn, E.A., Halley, R.B. and Lidz, B.H., 1976. Autopsy of a dead coral reef. Am. Assoc. Petr. Geol. 1976 Annual Mtg., Abstract: 76. Kellogg, H.E., 1960. Geology of the southern Egan Range, Nevada. In: Guidebook to the Geology of East Central Nevada, J.W. Boettcher and W.W. Sloan, Jr., (editors): 189-197. King, P.B. and Knight, J.B., 1945. Geology of the Hueco Mountains, El Paso and Hudspeth counties, Texas. U. S. Geol. Survey Oil and Gas Invest. Prelim. Map 36, 2 sheets. Kirkpatrick, R., 1911. On Merlia normani, a sponge with a siliceous and calcareous skeleton. Q. Jl. Microsc. Sci., 56:657-702. Koechlin, E., 1947. Chaetetiden aus dem Malm des Berner Jura. Schweiz. Paleontol., 65 (1):16. Konishi, K. and Wray, J.L., 1961. Eugonophy11um, a new Pennsylvanian and Permian algal genus. J. Paleo., 35:659-666. Korring, A.P., 1947. Relations between the moon and period¬ icity in the breeding of marine animals. Ecol. mongr. 17:347-381. Kottlowski, P.E., Flower, R.H., Thompson, M.L. and Foster, R.W., 1956. Stratigraphic studies of the San Andres Mountains, New Mexico. N. Mex. Inst. Min. and Tech., State Bur. Mines and Mineral Res., Mem. 1.

Lane, B., 1960. The Ely Limestone in the vicinity of Moorman Ranch, Nevada. In: Guidebook to the geology of East Central Nevada, J. W. Boettcher and W. W. Sloan, Jr. (editors):114-116.

Langenheim, R.L., Jr., Barr, F.T., Shank, S.E., Stensaas,L.J. and Wilson, E.C., 1960. Preliminary report on the geology of Ely no. 3 Quad, White Pine County, Nevada, In: Guidebook to the geology of East Central Nevada, J.W. Boettcher and W.W. Sloan,Jr. (editors):148-156.

LeMone, D.V. and Lovejoy, E.M.P. (editors), 1976. General stratigraphy of the Franklin Mountains. In: El Paso Geol Soc. Symposium on the Franklin Mountains, Quinn Memorial Volume:3-5.

II Lindstrom, G., 1876. Affinities of the anthozoa tabulata. Ann. Mag. Nat. Hist., ser. 4, 18.

II Lindstrom, G., 1899. Remarks on Heliolitidae. Kongl. Svenska Vetenskaps-Akad. Handlingar, no. 1, 32. Logan, B.W., Harding, J.L., Ahr, W.M., Williams, J.D. and Snead, R.G., 1969. Carbonate sediments and reefs, Yucatan shelf, Mexico. Am. Ass. Petr. Geol., mem. l^L : 1-198. Lustig, L.D., 1971. Middle Pennsylvanian Chaetetes (Tabulate) from the Bird Spring Formation of Southern Nevada. Master's thesis, UCLA, 147p. Ma, T.Y.H., 1937. On the growth rate of reef corals and its relation to sea water temperatures. Nat. Inst. Zool. Bot. (Acad. Sinica) Zool., 1:1-266.

Manton, S.M. and Stephanson, T.A., 1935. Ecological surveys of coral reefs. Great Barrier Reef Exped. 1928-29, Sci. Rept. Brit. Mus. (Nat. His.), 3(10): 274-312. Marshall, S.M. and Orr, A.P., 1931. Sedimentation on Low Isles Reef and its relation to coral growth. Great Barrier Reef Exped. 1928-29. Sci. Rept. Brit. Mus. (Nat. Hist.), 1(5):94-133. Maxwell, W.G.J., 1968. Atlas of the Great Barrier Reef. Elsevier, Amsterdam. Mayor, A.G., 1924. Growth rate of Samoan corals. Carnegie Inst. Wash., pub. 340:51-72. Mendivil, S., 1972. El Carbonifero en el Peru (abstr). In: International Symposium on the Carboniferous and Permian Systems in South America, Abstr. Acad. Bras. Cienc. - Sao Paulo, Univ. Inst. Geoscience : 33-35. Milliman, J.D., 1974. Marine carbonates. Springer, Berlin- Heidelberg-New York, 375p. Moore, W.E., 1957. Ecology of Recent foraminifera in northern Florida Keys. Am. Ass. Petr. Geol., Bull. 41:727-741. Murray, J.W., 1973. Distribution and Ecology of Living Benthic Foraminiferids. Crane, Russak and Company, Inc., New York, 274 p. Nelson, W.J. and Langenheim, R.L., Jr., 1974. Ecological observations of Chaetetes in southern Nevada (abstr.). In: South-Central Section 8th Annual Meeting, Geol. Soc. Amer. Abstr., 6(2):118-119.

Neumayer, M., 1899. Die stamme des thierreiches. Viena, 1:283-303. Newell, N.D., Chronic, J., and Roberts, T.G., 1953. Upper Paleozoic of Peru. Geol. Soc. Amer., mem. 58:l-276. Nichols, D., 1969. Echinoderms. Hutchinson Univ. Library, 4th edition, London, 192 p. Nicholson, H.A., 1879. 0n the structure and affinities of the tabulate corals of the Paleozoic period. Edinburgh, London, 342 p. Nygreen, P.W., 1958. The Oquirrh Formation, stratigraphy of the lower portion in the type area and near Logan, Utah. Utah Geol. Mineral. Survey, Bull. 61:1-67. Okulitch, V.J., 1936a. On the genera Heliolites, Tetradium, and Chaetetes. Amer. Jour. Sci. , 32^361-379. Okulitch, V.J., 1936b. Streptindytes chaetetidae a new species of "parasitic" annelid found on Chaetetes radians. Am. Midland Nat., 17:983-984. Oliver, W.A., Jr., 1968. Some aspects of colony development in corals. Jour. Paleo., 42(mem. 2, pt II, supp. to no. 5):16-35. Pannella, G., and Maclintock, C., 1968. Biological and environmental rhythms reflected in molluscan shell growth. Paleont. Soc., mem. 2^:64-79. Peterhans, E., 1929. Des chaetetidides der Lias et du Dogger. Ecol. Geol. Helv., 22:113-131. Rich, M., 1960. Chaetetes in the Bird Spring Formation near Lee Canyon, Clark County, Nevada. Jour. Paleo., 34(4):761-762. Rich, M., 1969. Petrographic anaylsis of Atokan carbonate rocks in Central and southern Great Basin. Am. Assoc. Petr. Geol., Bull., 53:340-366. Rios, J.M. and Almela, A., 1944. Un chaetetido del Eoceno espaxSol. Notas Inst. geol. Esp., 12:1-19. R0os, P.J.R., 1967. Growth and occurrence of the reef coral Porites astreoides Lamarck in relation to sub¬ marine radiance distributions. Academic proefschrift. Utrecht. Rosen, B.R., 1971. Principal features of reef-coral ecology in shallow-water environments of Mane, Seychelles. In: Regional variation in Indian Ocean coral reefs: Zool. Soc. London Symp. 28:163-183. Rudwick, M.J.S., 1970. Living and fossil brachiopods. Hutchinson Univ. Library, London, 199 p. Ryland, J.S., 1971. Bryozoans. Hutchinson Univ. Library, London, 175 p.

Schmidt, P.G. and Craddock, C., 1964. The Geology of the Jarilla Mountains, Otero County, New Mexico. State Bureau of Mines and Min. Resources, New Mex. Inst. Min. and Tech. Campus Station, Socorro, New Mex., Bull. 82, 55 p. Schnorf-Steiner, A., 1963. Sur quelque "Chaetetidae” du Jura. Ecol. Geol. Helv., 56:1117-1129. Scrutton, C.T., 1964. Periodicity in Devonian coral growth. Paleont. , 7 (4):552-558. Sokolov, B.S., 1939. Stratigraphical value and types of Chaetetidae of the Carboniferous of the USSR. C.R. Acad. Sci. URSS,23:409-412. Sokolov, B.S., 1955. Tabulyaty Paleozoya evropeyskoy chasti SSR; Trudy VNIGRI 85:1-527. (Paleozoic tabulates from the European USSR. English translation, 1967, 735 p., Dept. Secy. State, For. Lang. Div., Ottawa, Canada). Sokolov, B.S., 1962. Gruppa Chaetetida. In: Osnovy Paleontologii, Yu. A Orlov (editor), Akad. Nauk. SSSR, Moscow, 2:169-176. (Fundamentals of Paleontology, English translation, Israel Prog. Sci. Trans., 2:259-270). Stanley, S.M., 1971. Relation of shell form to life habits in the Bivalvia (Mollusca). Geol. Soc. Amer., mem. 125:1-283. Steele, C., 1960. Pennsylvanian - Permian stratigraphy of East-Central Nevada and adjacent Utah. In: Guidebook to the geology of East Central Nevada, J. W. Boettcher and W. W. Sloan, Jr. (editors), 91-113. Stephanson, T.A., and Stephanson, A., 1933. Growth and asexual reproduction in corals. Brit. Mus. (Nat. History), Great Barrier Reef Exped., 1928-29, Sci. Rept. 3(7):167-217.

Stitt, J.H., 1964. Carboniferous stratigraphy of the Bend area, San Saba County, Texas. Unpublished Master's Thesis, Univ. Texas, 152 p. Struve, A., 1898. Ein beitrag zue kenntnis des festen gerustes der steinkbrallen. Structur der hexacorallen. Verhandlungen der Russisch-Kaiserlichen Mineralogischen Gesell. zu St. Petersberg, 35(2):43-45. Thompson, D'A. W., 1942. On growth and form. Cambridge Univ. Press, Cambridge (2nd edition), 1116 p.

Thompson, M.L., 1948. Studies of American fusulinids. Protozoa Article no. 1, Univ. Kansas Pub., 184 p. Thompson, M.L., 1964. Fusulinacea. In: Treatise on In¬ vertebrate Paleontology, Part C, Protista 2, by Loeblich, A.R. and Tappan, H., edited by R. C. Moore, Geol. Soc. Amer, and Univ. Kansas Press. Thorson, G., 1946. Reproduction and larval ecology of marine invertebrates. Biol. Rev. 25:1-45. Toomey, D.F., 1969. The biota of the Pennsylvanian (Virgilian) Leavenworth Limestone, midcontinent region Part 2: Distribution of Algae. Jour. Paleo., 43:1313-1330. Toomey, D.F., 1972. The biota of the Pennsylvanian (Virgilian) Leavenworth Limestone, midcontinent region Part 3: Distribution of calcareous foraminifera. Jour. Paleo. 46:276-298. Toomey, D.F., 1976. A Permian marine plant controlled community, Northern Franklin Mountains, West Texas. El Paso Geol. Soc. Symposium: Stratigraphy and structure Franklin Mountains, Quinn Memorial Vol:67-76. Toomey, D.F. and Winland, H.D., 1973. Rock and biotic facies associated with Middle Pennsylvanian (Desmoinesian) algal buildup, Nena Lucia field, Nolan County, Texas. Am. Assoc. Petr. Geol., Bull. 57:1053-1074. Vaughn, T.W., 1918. Some shoal-water corals from Murray Island (Australia), Cocos-Keeling Islands, and Fanning Island. Pap. Dep. mar. Biol. Carnegie Instn. Wash. 9:49-219. Vaughn, T.W., 1919. Coral and the formation of reefs. Smithsonian Instn., Ann. Rept. for 1917:189-238. Webster, G.D., 1969. Chester through Derry conodonts and stratigraphy of northern Clark and southern Lincoln Counties, Nevada. Univ. of Calif. Pub, in Geol. Sci. 79. Wells, J.W., 1957. Corals reefs. In: Treatise on Marine Ecology and Paleoecology, 1, Ecology. Geol. Soc. Amer., mem. 67:609-631. Wells, J.W., 1963. Coral growth and chronometry. Nature, 197:948-950. Wengard, S.A., 1962. Pennsylvanian sedimentation in Paradox Basin. 4 Corners Region. In: Pennsylvanian System in the United States - A Symposium: Am. Assoc. Petr. Geol:264-330. Wengard, S.A., 1963. Stratigraphic section at Honaker Trail, San Juan Canyon, San Juan County, Utah. In: Shelf Carbonates of Paradox Basin. 4th Field Conference Four Corners Geol. Soc. Symposium, R.O. Bass, and S.L. Sharp (editors):235-243. Wilson, E.C., 1963. The tabulate coral Multithecopora Yoh from the Chaetetes-Profusulinella faunizone in eastern Nevada. Jour. Paleo., 37(l):157-163. Wilson, J.L., 1975. Carbonate facies in geologic history. Springer-Verlag, New York-Heidelberg-Berlin, 471 p. Wilson, J.L., Madrid-Solis, A., and Malpica-Cruz, R., 1969. Hicrofacies of Pennsylvanian and Wolfcampian strate in Southwestern USA and Chihauhau, Mexico. In: Guidebook of the Border Region, Cordoba, D.A. et al. (editors), New Mexico Geol. Soc., Twentieth Field Con f erence: 8 0-9 6.

Winston, Don, 1963a. Stratigraphy and carbonate petrology of the Marble Falls Formation, Mason and Kimble Counties Texas. Unpublished Ph.D. dissertation, Univ. Texas, 344 p.

Winston, Don, 1963b. Carbonate cycles: Lower Pennsylvanian Marble Falls Formation, Mason and Kimble Counties, Texas. Am. Assoc. Petr. Geol., Bull. 47(2):376.

Winston, Don, 1965. Chaetetes biostromes - Pennsylvanian surfaces of bypassing and scour (abstr.). Geol Soc. Amer., special paper 82:227. Wood-Jones, F., 1907. On the growth forms and supposed species in corals. Zool. Soc. London, Proc:518-556. Wray, J.L., 1962. Pennsylvanian algal banks, Sacramento Mountains, New Mexico. In: Kansas Geol. Soc. 27th Annual Field Conf., Guidebook. Wichita Kansas Geol. Soc., 158 p. Yonge, C.M., 1960. Ecology and physiology of reef building corals. In: Perspectives in Marine Biology, Univ. Calif. Press: 177-135. Zankl, H., and Schroeder, J.H., 1972. Interaction of genetic processes in Holocene reefs off North Eleuthera Island, Bahamas. Geol. Rundsch., 61:520-541. Zittel, K.A., 1876. Palaozoologie (Handbuch der Palaontologie, v. 1), Munich and Leipzig, l(VII)îl-715. Plate 1. Shingle-form Chaetetes. Numerous increases

and decreases in width are evidenced in this chaetetid. Locality: at 65 meters, Northern Franklin Mountains section.

Plate 2. Large anastomosing complex of shingle-form

Chaetetes. Locality: at 65 meters, Hueco Mountains section.

Plate 3. Large anastomosing complex of shingle-form Chaetetes. Locality: at 63 meters, Northern

Franklin Mountains section.

Plate 4. Club-form Chaetetes; a. Typical club-form chaetetids from Northern Franklin Mountains section at 118.5 meters. b. 4 meter club-form lying prone on bedding

surface; Winston section 49, Llano-region, Texas.

Plate 5. Clustering of club-form Chaetetes. a. Small groups solitary club-forms at Bend Dump section, Llano-region, Texas. b. Cluster of several colonies. Vinton Canyon,

Northern Franklin Mountains, Texas.

Appendix I Lithotopic Descriptions

Oolitic Grainstone (plate I) Oolitic grainstones contain multilaminated rounded grains that are occasionally multinucleate. Nuclei of these coated grains commonly are rounded fragments of brachiopods and , less common are fragments of ramose bryozoa, gastropods, and phylloid algae. Associated megafossils include brachiopods, crinoids and large phylloid algal plates. Crinoidal debris forming nuclei of coated grains are preferentially moderately to heavily iron-stained and are poorly preserved. Oolitic grainstones are well-sorted with parallel elongate grains and contain no mud. Trough cross-bedding characterizes this unit. Oolitic grainstones are indicative of high energy shoaling depositional environments.

Archaeolithophyllid Grainstone (plate I) The rounded coated grains of archaeolithophyllid grainstones have thick laminae exhibiting an internal structure similar to the red algal Archaeolithophyllum sp. Of. A. lamellosum Wray, 1964. Original structures of the well-rounded nuclei tend to be obscured though fragments of brachoipods, crinoids, lithoclasts, phylloid algae and ramose bryozoa are present as are trace occurrences of foraminiferids. These coated grains are well-sorted and are generally less iron-stained than are the oolitic grains. Megafossils include silicified brachiopods and crinoidal debris. No sedimentary structures are associated with archaeolithophyllid grainstones.

This coated grainstone lithotope was deposited in a high-energy shoaling environment.

Osagid Grainstone (plate II)

The small ellipsoidal bean-shaped grains of this lithotope have been badly abraded, have a single, thin indistinct lamina and are often recrystallized and iron- stained. Abraded crinoidal debris are the most readily distinguishable nuclei, though the benthonic and encrusting foraminiferids, çalcitornellids, Climacammina, and ramose bryozoa are also present. , and abraded coral debris are associated megafossils. In the Hueco Mountains, abundant rounded Chaetetes give this grainstone a "nodular limestone" aspect. Whereas oolitic grainstones and archaeolithophyllid grainstones contain no muds, in-

filtered muds, intraclasts and large pelletoids may comprise up to 15% of this rock. Osagid grainstones are poorly sorted and have no associated sedimentary structures.

Osagid grainstones were deposited in waning high-energy environments. The degree of abrasion and thin lamination of the coated grains suggests that these grains may be oolitic and archaeloithophyllid grains that have been extensively

reworked. Infiltered muds and other interstitial materials imply periods of deposition in lower energy environments. Oncolitic Grainstone (plate II) This lithotope contains rounded to angular, moderately to heavily iron-stained pebble-size lithoclasts and rugose coral debris. These clasts are thickly laminated. Large rock slabs .25 to .5 meters in length, and petrified logs are also pre¬ sent. This unit contains trough cross-beds and is poorly sorted.

Erosion of shelf and adjacent terrestrial deposits and subsequent deposition of this debris in shallow-water channels probably produced this lithotope.

Calcitornellid Packstone-Grainstone (plate III)

Calcitornellid packstone-grainstones are characterized by abundant calcitornellid-calcivertellid fragments. Crinoidal debris is common, with less common to trace occurrences of

Climacammina, fusulinids, Tetrataxis, Cuneiphycus, fragments of phylloid algae, ramose bryozoa and brachiopods. Discrete pelletoids and clotted muds comprise from 0 to 25% of this packstone-grainstone. In polished slabs burrow-mottles are infilled with pelmicrite. Megafossils commonly include brachiopods, crinoidal debris and abraded rugose corals. Chaetetes, Chaetetes-encrusted Rugosa and rugose corals are associated with a calcitornellid packstone in the Hueco Moun¬ tains section; however, Chaetetes are excluded from the over- lying calcitornellid grainstone. Occasional chert nodules and traces of glauconite are associated with this lithotope. The growth forms of Calcitornella and Calcivertella suggest that these encrusting foraminiferids required attachment surfaces. As they are rarely found in their encrusting growth positions, it is likely that these foraminiferids were attached to non-fossilizable materials. This growth mode and the associated fauna and flora suggests that this lithotope typifies a shallow-water sea-grass thicket similar to Thalassia thickets with Melobesia- encrusted Thalassia blades (Milliman, 1974, p. 175). Upon decay of the sea grasses, Melobesia contribute to the under¬ lying sediments.

Cuneiphycus Packstone - Grainstone (plate III)

The Cuneiphycus packstone-grainstone lithotope contains up to 75% primarily disarticulated thalli of Cuneiphycus sp. cf. C. texana Johnson. In polished slabs, crinoid stems are common and "Girvanella" tubes, calcivertellids, Tuberitina, fusulinids, millerellids and fragments of brachiopods and fistuloporid bryozoa occur less frequently. Chaetetes may occur as megafossils. The matrix is white to very light tan or grey micrite and pelmicrite with moderately iron-stained or oil-stained borrow-mottled micrites. Thickets of the red alga Cuneiphycus probably flourished at slightly greater depths and/or in more open criculation than did the green codiacean phylloid alga thickets. A preference for more open shelf conditions is suggested by the presence of greater numbers of more open-marine organisms.

Crinoidal Packstone - Grainstone (plate IV)

Crinoidal grainstones are composed almost entirely of crinoidal debris with rare brachiopod fragments; whereas crinoidal packstones also contain abundant, poorly sorted, subrounded to subangular micritic lithoclasts and pellets, and rare to trace abundances of calcivertallids, millerellids,

Cliitiacammina, glauconite and ramose bryozoa. Thin, silty, iron-stained stylolites characterize this lithotope. This lithotope was deposited in a high-energy shelf environment as indicated by the lack of mud in the grain- stones and by the presence of lithoclasts in the packstones. Poor sorting and the angularity of the lithoclasts suggest that these packstone-grainstones may be related to inter¬ mittent high energy waves and currents or storm activities rather than constant shoaling conditions.

Intraclastic Bioclastic Wackestone (plate IV) Angular intraclasts and pelmicrites comprise from 60 to 70% of this wackestone. Skeletal fragments are more abun¬ dant than are whole skeletal grains. The most abundant allochems are tiny fragments of foraminiferid tests that are too small to positively identify; crinoid stems and spines are also abundant. Whole foraminiferids are rare and include calcitornellids and Tuberitina. Ramose and

fistuloporid bryozoa, coral and brachiopod debris is common with traces of phylloid algae and ostracods. Megafossils include prone rugose corals without epithecas and brachiopods

and can occur in chert nodules within this unit. Intraclastic

bioclastic wackestones are burrow-mottled with light oil- stained silt infillings. Some of the intraclasts appear to be the products of in-situ bioturbation. The presence of these floral and faunal constituents and the presence of muds suggest that deposition of this

lithotope was on a shallow-water shelf adjacent to sea- grass thickets.

Encrusted Phylloid Algal Wackestone (plate V)

Encrusted phylloid algal wackestones are characterized by a diverse, yet specialized assemblage or organisms.

Recrystallized whole plates and fragments of phylloid algae are most abundant (30 to 70%) and occasionally are encrusted by calcitornellids and fistuloporid bryozoa. If abundances of phylloid algae are lower (50%), then other organisms will be present in trace to common abundances including: common-

brachiopods, pelecypods, crinoids; rare to common - Endothyra Calcivertalle, Bradyina, Tetrataxis, Tuberitina, millerellids fusulinids; trace - gastropods, ostracods, ramose bryozoa.

Coarsely pelleted and clotted pelmicrites comprise up to 45% of the wackestone. Rugose corals and Chaetetes are associated with lower abundances of phylloid algae. Occa¬

sionally this wackestone appears to be burrow-mottled or it may contain chert nodules. Though capable of forming massive, ridge-forming units, encrusted phylloid algal wackestones can also be bedded with wavy bedding planes. The presence of commensual organisms as well as other bottom-sediment dwelling organisms suggests that this wackestone was deposited on a shallow-water sea floor covered with sparse to densely populated patches of phylloid algae. These calcareous algae lived within the photic zone, and due to the delicate nature of their thalli, phylloid algae probably lived below the normal wave base.

Phylloid Algal Wackstone - Packstone (plate V)

Large recrystallized plates of phylloid algae dominate this lithotope. The encrusting foraminiferids, Calcivertella

and Calcitornella, and ostracods and brachiopods occur in trace to rare abundance. Muds infiltered between thalli are rarely pelleted and spar-infillings are common. In the field units form massive hummocky beds or loaf¬

shaped mounds. The large abundant thalli form wiggly laminae on the outcrop surface. Phylloid algal wackestone-packstones characterize portions of the sea-floor that were dominated by phylloid algae. These flourished in prolific numbers, excluding other bottom dwellers from the sea floor, and developing

tabular or loaf-shaped mounds.

Pelleted Foraminiferal Wackestone - Packstone (plate VI)

Pelleted foraminiferal wackestone-packstones contain up to 65% pelmicrites consisting of numerous small pelletoids with larger pellets preserved in burrow structures. A diverse planktonic fauna of fusulinids and smaller non-fusulinid foraminiferids characterizes this

lithotope and includes Endothyra, Climacammina, Calcivertella, Tetrataxis, millerellids, and tubular organisms. Less

common are ostracods and benthonic organisms including Cuneiphycus, brachiopods, ramose and fistuloporid bryozoa.

Very small fragments of phylloid algae and crinoidal debris are abundant. Megafossils include crinoidal debris and brachiopods. Chert nodules and chert layers are also present. Light grey or tan pelmicrites may be lightly oil-stained or iron-stained. This lithotope is interbedded with encrusted phylloid algal wackestones and tubular ?species wackestone - packstones. This relationship suggests that these pelleted foraminiferal wackestone-packstones were deposited on parts of the sea floor that were not dominated by the benthonic organisms characteristic of the other lithotopes.

Tubular ?species Wackestone - Packstone (plate VI)

This lithotope is composed of up to 75% tubules and networks of benthic tubular organisms. Some of these organisms are preserved in growth position. Crinoid stems, Climacammina, Tuberitina, fusulinids, millerellids and brachiopods may compose up to 45% of this rock.

Ramose bryozoa and Tetrataxis are rare. Two to 15% of this rock consists of infiltered micrites and pelmicrites with trace occurrences of small rounded lithoclasts. This matrix is very light, almost white in color, but can be moderately oil-stained. Tubular Pspecies wackestone-packstones are often associated with laminated bioclastic wackestone-packstones.

These tubular organisms are similar to Winston's "tubular algae" (1963a, p. 66) which were assigned to the genus Donezella by Freeman (1962, p. 10). Stitt (1964, p. 62) believes that the tubules are growth forms of Cuneiphycus and Komia. This author finds a striking similarity between this "tubular organism" and the tubular nubecularid foraminiferid Cornuspirimia as figured in Thompson (1964, C446); however, a more detailed study would be necessary before this organism could be identified as tubular foraminiferid.

The presence of open-shelf foraminiferids and the absence of algae suggests '‘that this lithotope was deposited in more open circulation, deeper waters of the outer shelf region.

Abraded Bioclastic Packstone (plate VII)

Abraded bioclastic packstones contain moderately well-sorted, parallel elongate skeletal grains and lithoclasts. Crinoidal debris, fusulinellids, millerellids and productid spines are abundant; Globovalvulina, Tuberitina, Climacammina, endothyrids, Calcivertella, tubular organisms, Cuneiphycus, ramose bryozoa and sponges are rare to common. Some biolclasts are pyritized and lithoclasts may be

heavily oil-stained. Associated micrites may be laminated and moderately oil-stained and iron-stained. This lithotope is commonly interbedded with laminated

bioclastic mudstone-wackestones. The great diversity of faunal components in addition to the heavy iron-staining and abrasion of the bioclasts, parallel elongate clasts and degree of sorting suggests that reworking on the sea floor has occurred. This debris may have been washed across the shelf, eventually to be deposited in the deeper, quieter shelf waters.

Laminated Bioclastic Mudstone - Wackestone (plate VIII) This lithotope contains interbedded homogeneous black spiculitic micrites and laminated black and iron-stained micrites with Calcivertella-Nubecularia consortiums.

Bioclasts are rare and include productid spines, crinoidal debris, helical gastropods, sponges, ramose bryozoa, Globovalvulina, endothyrids and fusulinids. Associated megafossils include club-form Chaetetes, brachiopods and large gastropods. Euhedral dolomite rhombs pervade some of the spiculitic micrites, and iron-stained seams emphasiz laminations in the wackestones. Bioclasts including delicate sponge networks may be pyritized. Discrete, zoophyeus-type burrows appear in the spiculitic micrites.

Laminated bioclastic mudstone-wackestones are occasionally interbedded with tubular ?species wackestone-packstones. and with abraded bioclastic packstones.

The paucity of benthonic organisms and the open-marine nature of these organisms suggest that this lithotope was deposited in outer shelf waters where poor circulation resulted in poorly oxygenated conditions on the sea floor. Plate I

Photographs of polished slabs. All figures are oriented with top to top of the plate. Sample numbers refer to localities and sample numbers in Appendix II. Scale = x 1.7.

Figure

A. Oolitic grainstone (1-03) B. Archaeolithophyllid grainstone (1-02).

75

Plate II

Figure A. Osagid grainstone (1-49).

B. Oncolitic grainstone (2-63). A B 76 Plate III

Figure A. Calcitornellid packstone - grainstone (2-38).

B. Cuneiphycus packstone - grainstone (2-30). A B Plate IV

Figure

A. Crinoidal packstone - grainstone (1-38).

B. Intraclastic bioclastic wackestone (2-01). A 78

Plate V

Figure A. Encrusted phylloid algal wackestone (1-18). B. Phylloid algal wackestone - packstone (1-13). A B 79

Plate VI

Figure A. Pelleted foraminiferid wackestone - packstone

(2-22) B. Tubular ?species wackestone - packstone {2-21).

80

Plate VII

Figure

A. Abraded bioclastic packstone (2-37).

B. Laminated bioclastic mudstone - wackestone (2-55). B A Appendix II LEGEND

Porticle Types a phylloid algae A encrusting forominifera a Cunelphvcus ® pelagic forominifera brachiopods A tubular organisms T ☆ crinoids gastropods n ramose bryozoa €> productid spines ft fistuloporid bryozoa sponge spicules

© Rugose corals introdosts 09 Choetetes • pellets 4 fusulinids

% of Allochems T trace <5% R rare *5% «30% C common - 30 % «70 % A abundant >70 %

Weolhering Profile

thick-bedded or massive

thin-bedded

chert nodule

S3 chert layer

Choetetes SES za: burrow-mottled Rugose corals ÜTHOTOPES

Coated Grainstones 1. oolitic grainstone

2. archaeotithophyllid grainstone

3. osagid grainstone

4. oncolitic grainstone

Skeletal Packstone - Grainstones

5. calcitornellid packstone - grainstone

6. Cuneiphvcus packstone

7 crinoidal packstone-grainstone

Skeletal Wackestone - Packstones

8. intraclastic bioclastic wackestone

9. encrusted phylloid algal wackestone

10. phylloid algal wackestone - packstone 11. pelleted foraminiferal wackestone-packstone

12. tubular ? species wackestone - packstone

13. abraded bioclastic wackestone - packstone

Mudstone - Wackestones

14. laminoted bioclastic mudstone-wackestone

15. sittstone

16. shale Hueco Mountains Section

The Hueco Mountains Section was measured on the south side of Pow Wow Canyon. It can be reached from El Paso, Texas by driving east on Highway 62 and 180, 6/10 of a mile east of the turn-off for the Hueco Tanks State Park. The section faces the south side of Highway 62 and 180, and begins at the top of the talus slope with the first outcrop of limestone. SECTION 1= HUECO MOUNTAINS, TEXAS

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A T c T 7 C T c A l J 9 L 87 t-55 - •fH -1-55 ^uj «N» lira ag

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1-51 ■ -1-51 c" C C C â C 2 —fault—

A © 7 "e 0 © 1 1 *r\ ☆ © w I T *i V ZJ SMPL. UTHO- SMPL. PARTICLE TYPES NO. TOPE NO. MEASURED SECTION: SMPL. UTHO- WEATHERING CUM. NO. TOPE PROFILE METERS 0 0 YT Tt Y « o » 1 A ® * $ Q \ 0 • »

c c c c T A A 1-58 - .1-58 99 il 1-67 « -1-57 -J , 1 1 1 <§> A • 0 0 T ☆ Y Y O P? 1 A T * O V SMPL. UTHO- SMPL. PARTICLE TYPES NO. TOPC NO. Northern Franklin Mountains Section

To reach this section, proceed north on Highway 20 through the town of Anthony, Texas-New Mexico. Turn east on New Mexico 404, continue for 4-9/10 miles to the dirt road on the south side of the highway. Proceed through the gate, following the dirt road to the small non-operative quarry at the base of the mountain. The section begins with the first limestone ridge outcropping above the quarry» Beds in the line of section dip 51° NE. SECTION 2s NORTHERN FRANKUN MOUNTAINS

| MEASURED SECTION: [ SMPL. UTHO- WEATHERING CUM. A NO. TOPE PROFILE MET ER Si £ £ ☆ i « © P ï a £ £ V » 9m c R A R c C c X

i

s 21 T ~R C c X X 2-12 & 2-12 A £ “c T X C T C ~R T X 2-11 2-11

18 C" R_ 2-10 w 2-10 c £ X X A c C T T c X c R T A w 15 2-09. w 2-09 m 2-08 2-08 X C C T Ti c c T c X T X S A C c T T c T c R T A ETEt 12 s? CO 9 A c c T T c c T c W T X 2-07. 2-07 2-05 2-05 2-06 ijB 2-06 A c "c T c c X T T R! 7 • f ®l < 9 6 2-04 ZT 2-04 overed X £ X X £ £ £ X ■fl .-.J? Y

WL1L3 ■ T X 2-03 3 T c T T c £ £ A 2-03 2-02 w 2-02 R £ R £ X £ T R 8 2-01 I «k*11 .2-01 lQQQE»3@aca^HQE!BDl! SMPL UTHO- SMPL. PARTICLE TYPES NO. TOPC NO.

Jk profusln«tlo

* toutin') !o MEASURED SECTION» SMPL. UTHO- WEATHERING CUM. TOPE PROFILE METERS A • NO. vr « O ft T ♦ ♦ o ■V O <» r

. 165

Vcovered 162

159

T T c c c T 14 156 2-58- ■ A "2-58

153

V 150

147 12 A c C T c C A A » 2-57- -2-sr 12 1 4 wT l" n

T A Üj A e> 0 • # ft A * O ft 1 T 4 V SMPL. UTHO- SMPL. PARTICLE TYPES NO. TOPE NO. MEASURED SECTIONS SMPL. UTHO- WEATHERING CUM.

7" • NO. TOPC PROFILE METERS ✓ ff ☆ vr « O î? 1 A ® ♦ $ V 0 9 \/ covered /\ c c c 14 M 1 ! l - 189 7

covered 186

C c C c c c c R 14 = FF 183 2-60 - Wi ; 2-60

180 \/covered

177 1 A A A t T T R c R T c A A 9 ► 2-59 2-59 . ’ 174

171 Vcovered A V A <§) A o <> • © it * 4 © W 1 T « V SMPL. UTMO- SMPL. PARTICLE TYPES NO. TOPC NO. | MEASURED SECTION} j SMPL. UTHO WEATHERING CUM. NO. TOPE PROFILE METERS t tf ☆ 1 © » 1 A i 1 1 o •

I R R Â J 2-63 - 4 §339 -2-63

T A R R z X Ü 8 • 213 -J-rVH \ / covered

210 T A R R c A c 8 L 2-62 - •2-62 \ / covered

/N 207 T R C c R

• 204

201

covered

1 ■ 198

195

SMPL. UTHO* SMV PARTICLE TVPES NO. TOPE A NO. Middle Cherokee Creek Section

The Middle Cherokee Creek section measured by Stitt (1964) is now owned by Eliot Matsler. To reach this section, drive southwest from Bend, Texas, 1.5 miles on

Farm Road 580, turning left on Farm Road 501 and continue

0.7 mile to the High Valley Church. Turn left into the gravel road east of the church, following the road across Cherokee Creek. Obtain permission from Mr. Matsler. His house is on the right side of the road about 0.2 mile from the creek. The section starts south of the bridge, about 250 yeards with the first resistant bed and continues along the east side of the creek. Stitt reports that the section was painted by Humble Oil and Refining Company geologists in 1957; numbers run from 145 to 210 feet, and beds dipping 6° NW in the line of section. MIDDLE CHEROKEE CREEK SECTION

based on Stitt (1964) Bend Dump Section

Stitt's (1964) Bend Dump Section is located 0.9 miles southwest of the center of Bend on Farm Road 580 in the Bend City Dump. The section starts 150 yards

north of the dump entrance, and is at the edge of river

below the expsoure of the Smithwick Shale. BEND DUMP SECTION

MEASURED SECTION: SMPL. UTHO- WEATHERING CUM. • NO. TOPC PROFILE METERS * * « © pf s A & ♦ * O V o 9

* R R R TT I4 • 6

I"I*7

T R T R C 3 * I4

X BdD-2: :BdO-2 C A A A BdD-l I4 BdO-l

A I) & Ô 0 • © ft ft T ☆ 1 $ © w i T 4 V SMPL. UTHO- SMPL. PARTICLE TYPES NO. TOPE NO.

based on Stitt (1964) * olto cephalopods Bend Sections #48 and 49

Bend sections #48 and 49 were measured by Winston (1963) in the Cecil B. Smith ranch. From Fredericksburg Texas, drive west on Highway 290 for 23 miles to Harper. Three miles west of Harper go north on Highway 385 for 28 miles. Turn east on Ranch Road 1871 and go 6 miles to the gate of the Cecil B. Smith Ranch. After obtaining permission at the house, proceed on the pasture road for .05 miles then take the Smith fork and continue on the road as far as possible. Walk down the steep hillside to Little Rocky Creek and follow the creek bed to the bend in the Llano River. Sections

48 and 49 are along the east bank of the Llano River. Section 48 is 1500 feet north of the flat terrace in the bend of the river and section 49 is 1000 feet north of section 48 BEND SECTION **48

MEASURED SECTION: SMPL. UTHO WEATHERING CUM. Ü4LTHÏ.Ï?© HA.*® LL® NO. TOPE PROFILE METERS

12

II

14

■ 6 12

12 a

A (|) a \o * 4 Q 99 SMPL. UTHO* SMPL. PARTICLE TYPES NO. TOPE NO.

bosed on Winston (1963) BEND SECTION *49

based on Winston (1963)