Conodont Biostratigraphy of the Middle Pennsylvanian Sandia Formation and Lower Gray Mesa Formation in North-Central New Mexico

Home , Caballo Mountains, Conodont biostratigraphy, Fountain Formation, Gray Mesa Formation, Idiognathoides, Madera Group

Paul A. Moore, B.Sc.

A Thesis

Geoscience

Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of

MASTER OF SCIENCES

Approved

Dr. James E. Barrick

Dr. Thomas Lehman

Dr. Dustin E. Sweet

Mark Sheridan Dean of the Graduate School

ACKNOWLEDGMENTS Thank you Dr. Barrick for the time and guidance you gave me to complete this project, and thanks to Spencer G. Lucas (New Mexico Museum of Natural History), Karl Krainer (University of Innsbruck), and Bruce D. Allen (New Mexico Bureau of Mines and Mineral Resources) for providing samples, assistance in the field, and unpublished stratigraphic information. Conodont SEM images were obtained at the College of Arts & Sciences Microscopy facility.

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TABLE OF CONTENTS ACKNOWLEDGMENTS ...... II ABSTRACT ...... V LIST OF TABLES ...... VII LIST OF FIGURES ...... VIII CHAPTERS

1. Introduction ...... 1 2. Regional Geology ...... 3 3. Stratigraphy ...... 9

Sandia Formation ...... 9 Grey Mesa Formation ...... 15

4. Middle Pennsylvanian Chronostratigraphy and Biostratography in North America ...... 22 The Atokan-Desmoinesian Boundary ...... 22

5. Methods and Stratigraphic Section ...... 33

Methods...... 33 Type Sandia Section ...... 34 Tejano Highway Section ...... 35 Cedro Peak Z Section...... 37 Sepultura Canyon Section ...... 37 Presilla A & B Section ...... 38

6. Conodont Biostratigraphy of the Sandia and lower Gray Mesa Formation...... 51 Faunal Interval 1 ...... 51 Faunal Interval 2 ...... 51 Faunal Interval 3 ...... 52 Faunal Interval 4 ...... 53 Faunal Interval 5 ...... 54 Faunal Interval 6 ...... 54 Age of the Faunal Intervals ...... 55

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Ages of the Sandia and Gray Mesa Formations...... 59

7. Systematic Paleontology...... 62

CONCLUSION ...... 103 REFERENCES ...... 105

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ABSTRACT

Middle Pennsylvanian strata in central New Mexico are assigned to the clastic- dominated Sandia Formation, and the overlying carbonate-dominated Gray Mesa

Formation. In northern and central New Mexico the Sandia Formation represents the base of the Pennsylvanian and is recognized by synorogenic deposits associated with the

Ancestral Rocky Mountain Orogeny. The Sandia Formation is generally composed of a mixed siliciclastic and carbonate unit, with thick quartz rich sandstones, conglomerates, and conglomeratic sandstones that rest on Proterozoic igneous and metamorphic rocks.

The overlying lower Gray Mesa Formation is a cherty, cliff-forming limestone unit that includes mudstones, fossiliferous wackestones and packstones. Occasional beds of sandstone, siltstone and shale occur. Based on previous sparse fusulinid data, the age of the Sandia was interpreted to range from the late Morrowan through the Atokan, while the Gray Mesa was early Desmoinesian in age. Five sections containing the Sandia and lower Gray Mesa (Elephant Butte and Whiskey Canyon members) formations were sampled to derive a feasible conodont-based biostratigraphic framework, from north to south: the Type Sandia section and Tejano Highway section in the Sandia Mountains, the

Cedro Peak Z section in the Manzanita Mountains, the Sepultura Canyon section in the

Los Pinos Mountains, and two Presilla sections in the Cerros de Amado, east of Socorro.

Three evolutionary lineages of Neognathodus species were recognized that form the major basis for a series of six conodont faunal intervals: The Neognathodus atokaensis-N. colombiensis II lineage, the N. bassleri-N. asymmetricus lineage, and the N. uralicus-N. caudatus lineage. Faunal Interval 1 is defined by the first occurrence of N. atokaensis.

Faunal interval 2 is split into subintervals, 2a, defined by the first occurrence of N. "pre-

Texas Tech University, Paul Alex Moore, May 2017 colombiensis," and 2b, defined by the first occurrence of Idiognathodus gibbus. Faunal

Interval 3 is split into two subintervals, 3a, defined by the first occurrence of N. colombiensis, and 3b, defined by the first occurrence of N. bothrops. Faunal Interval 4 is defined by the first occurrence of N. asymmetricus and Faunal Interval 5 is defined by the first appearance of I. robustus. Faunal Interval 6 is defined by the first appearance of N. intrala. These faunal intervals improve on the work by Saelens (2014) and Treat (2014) in New Mexico and can be correlated to the Midcontinent conodont zonation of Barrick et al. (2013). Fauna Intervals 1, 2 and 3a are middle to late Atokan in age. The poorly defined Atokan-Desmoinesian boundary appears to lie between 3a and 3b, near the first occurrence of N. bothrops. Faunal Intervals 3b, 4, 5, and 6 extend through most, if not all of the lower Desmoinesian (Cherokee Group equivalent). The oldest conodont faunas (FI

1 and 2) were obtained from the base of the Sandia Formation at the type Sandia section, east of Albuquerque, and the middle of the formation in the Presilla A section in the

Cerros de Amado, east of Socorro. The age of the upper beds of the Sandia and the transition to the carbonate-dominated overlying Gray Mesa Formation varies from section to section. Commonly, the uppermost beds of the Sandia and basal beds of the

Gray Mesa contain a FI 3 fauna, which is like the Red House/Gray Mesa transition to the south (Saelens, 2014). However, in the Los Pinos Mountains (Sepultura Canyon section)

FI 3 appears in the middle of the Sandia Formation.

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LIST OF TABLES

2.1 Range chart of conodont species occurring in each section...... 101

2.2 Intervals respective to each section...... 102

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LIST OF FIGURES 1 ARM Orogeny Map ...... 6

2 Southwest US ARM Orogeny Map ...... 7

3 ARM Orogeny activity ...... 8

4 Nomenclature of lower Pennsylvanian strata ...... 21

5 North American Fusulinid Zonations ...... 28

6 North American Midcontinent Zonations ...... 29

7 Conodont Intervals of the Red House Formation ...... 30

8 Conodont Intervals of the Sandia and Porvenir Formations ...... 31

9 Conodont Zonations ...... 32

10 Map of the study sections ...... 42

11 Generalized strat column ...... 43

12 Type Sandia Section Strat Column ...... 44

13 Tejano Highway Section Strat Column ...... 45

14 Tejano Highway Section Strat Column ...... 46

15 Cedro Peak Z Section Strat Column ...... 47

16 Sepultura Canyon Section Strat Column ...... 48

17 Arroyo de Presilla A Section Strat Column ...... 49

18 Arroyo de Presilla B Section Strat Column ...... 50

19 Distribution of Faunal Intervals ...... 57

20 Comparison of Faunal Intervals to pre-existing intevals ...... 58

21 Idiognathodus ...... 88

22 Idiognathodus ...... 90

23 Idiognathodus ...... 92

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24 Idiognathodus ...... 94

25 Neognathodus ...... 97

26 Neognathodus ...... 100

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Chapter 1 Introduction

Basal Pennsylvanian strata in north-central New Mexico comprise the terrigenous clastic-dominated Sandia Formation, which is overlain by the carbonate-dominated Gray

Mesa Formation. Previous work using fusulinids and shelly fossils suggests that deposition of terrigenous clastics started during the latest Morrowan or early Atokan and shifted to carbonate deposition by the early Desmoinesian. Resolution of the timing of depositional events in north-central New Mexico is complicated by the weak biostratigraphic framework. The Atokan-Desmoinesian boundary is poorly defined and based on isolated fusulinid occurrences from south-central New Mexico and

Midcontinent North America (e.g., Wahlmann, 2013). Revisions of conodont zones for the Middle Pennsylvanian have been proposed by Barrick et al. (2013) for Midcontinent

North America, and by Nemirovska et al. (1999) and Alekseev and Goreva (2001) for the

Moscovian in the Donets Basin and Moscow Basin, respectively. However, the incomplete taxonomic framework for Middle Pennsylvanian species of Idiognathodus and Neognathodus has hindered characterization of the Atokan-Desmoinesian boundary using conodonts. Recent work in New Mexico in the Caballos Mountains (Saelens, 2014) and the Las Vegas area (Treat, 2014; Figure 1) has shown that considerable morphological change occurs in these genera across the Atokan-Desmoinesian boundary, but also that more work needs to be completed before they can be used to reliably characterize the Atokan-Desmoinesian boundary.

This project documents the distribution of conodonts from the Sandia Formation and the overlying Gray Mesa Formation in the Sandia Mountains east of Albuquerque,

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New Mexico, and southward to the Cerros de Amado region, east of Socorro. Recovery and analysis of conodont faunas provided sufficient material to test the applicability of biostratigraphic intervals proposed by Saelens (2014) and Treat (2014) for Atokan and early Desmoinesian strata. Improved age information is presented for the Sandia

Formation and lower Gray Mesa Formation that will better resolve the timing of depositional events associated with Ancestral Rocky Mountain Orogeny.

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Chapter 2 Regional Geology

The Ancestral Rocky Mountain Orogeny (ARM) comprises a series of block uplifts of Pennsylvanian-Permian age that lay adjacent to elongate, related narrow and deep basins (Kues, 2004; Figure 1). In northern New Mexico, elements of the Ancestral

Rocky Mountains consist of the Taos Trough, the southern Uncompahgre uplift and the

Sierra Grande uplift (Sweet and Watters, 2015; Figure 2). Ancestral Rocky Mountains deformation was centered in Pennsylvanian time (Kluth, 1998; Ye et al., 1996), between initiation of tectonism in the latest Mississippian and waning effects during the Early

Permian (Dickinson and Lawton, 2003; Figure 3). Basins in northeastern to eastern New

Mexico started to subside during late Mississippian to early Pennsylvanian, while basins to the south and west generally began subsiding during the Pennsylvanian with a peak in the early Permian (Kues, 2004). Kluth and Coney (1981) suggested that the ARM developed in the tectonic setting of the Ouachita-Marathon thrust system. During the

Middle Pennsylvanian, the collision between Gondwana and Laurasia was at its peak

(Kluth and Coney, 1981). Ye et al. (1996) suggested that the northwest-striking elements of the ARM are explained by northeast-directed, shallow-angle subduction along southwestern North America (Figure 2). Proterozoic mafic and ultramafic rocks have been found along the southwestern margin of the Uncompahgre uplift in the San Juan

Basin, suggesting that deformation within the Ancestral Rockies was also localized by a preexisting zone of weakness within the crust (Baars, 1966; Stevenson and Baars, 1977;

Stone, 1977).

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The Pedernal and Diablo uplifts are north- and northwest–striking basement highs that lie along the trend of the Uncompahgre uplift to the north, and border the Orogrande basin (Ye et al., 1996). Total structural relief that developed during Pennsylvanian and

Permian deposition along the southwestern flank of the Uncompahgre uplift was greater than 15,000 feet, which supplied tremendous amounts of sediments to nearby basins

(Haun and Kent, 1965). However, little of New Mexico's earliest Pennsylvanian

(Morrowan) is preserved due to major erosion and non-deposition associated with eustatic sea-level lowstand in combination with lack of major subsidence (Kues, 2004).

To the east of the Hueco Mountains, there is no record of Morrowan deposition across the southern Pedernal uplift, but it has been proposed that the Morrowan strata that linked the southern Pedernal uplift to the Orogrande was eroded (Ye et al., 1996; Kues, 2004).

Earliest sedimentation of the Orogrande basin comprises easterly derived, early

Pennsylvanian sandstones and chert-cobble conglomerates, suggesting erosion of the

Paleozoic sedimentary cover in the Pedernal and Diablo uplifts at this time (King and

Harder, 1985).

East of the Orogrande basin, Pennsylvanian and older rocks form tight folds and faulted folds on the Pedernal uplift (Ye et al., 1996). Asymmetric folds trend toward the west (King and Harder, 1958), and drilling data with Proterozoic rocks along the western

Pedernal uplift indicate Pennsylvanian strata was folded into northwest-trending anticlines (Otte, 1959; Pray, 1959), with chert conglomerates and sandstone eroded from the Pedernal uplift and deposited into the Orogrande basin during the Morrowan, which indicates that erosion, deformation, and uplift of the Pedernal uplift throughout the

Pennsylvanian, and that deformation was well underway by the Desmoinesian (Ye et al.,

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1996). Shallow marine, marginal marine, and non-marine strand plain sediments were deposited widely across New Mexico during the Atokan (Kues, 2004). Terrigenous clastic sediments were generated by nearby, relatively low uplifts, including the western side of the Pedernal uplift, Joyita uplift, and to the west, the Zuni uplift, (Kues, 2004).

The north-south trending Estancia basin parallels the Pedernal uplift, and accumulated as much as 1700m of Pennsylvanian sediments of Atokan age (Broadhead, 1997). The basin was actively subsiding and receiving sediments from the Pedernal uplift at sufficient rates to keep the basin filled and prograding westward as deltaic systems (Smith, 1999). The

Sandia Mountains border the Estancia basin to the west. The Sandia Mountains region received sediment from the Pedernal Uplift in Mississippian through early Permian time

(Karlstrom et al., 1998).

The modern features of these zones of late Paleozoic foreland deformation appear to be the result of reactivation of older structures due to Mesozoic and Cenozoic tectonic events (Ye et al., 1996; Kues, 2004). Late Paleozoic basins have been buried by younger sediments or, in the western part of the region, deformed again during the Tertiary, thereby obscuring the original structural relationships between the basins and the basement highs that lie adjacent to them (Ye et al., 1996). The Sandia Mountains form part of the eastern flank of the Rio Grande rift, and present structural characteristics are the product of continental extensional tectonism that took place since the beginning of the

Miocene (Karlstrom et al., 1999)

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Figure 1. Paleotectonic map of the ARM orogeny in New Mexico (Kues and Giles, 2004). Saelens’ (2014) study area is denoted by the red star near Las Vegas, NM, while Treat's (2014) study area is denoted by the red star to the south near the Orogrande Basin.

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Figure 2. Map of the southwestern United States displaying uplifts and basin of the ARM (from Sweet et al., 2015)

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Figure 3. Timing of event of the ARM orogeny was focused during the Pennsylvanian and early Permian (from Dickinson and Lawton, 2003)

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Chapter 3 Stratigraphy

Sandia Formation

The Sandia Formation in northern and central New Mexico generally forms the lowermost Pennsylvanian succession, and represents early synorogenic deposits associated with the Ancestral Rocky Mountain Orogeny (Krainer and Lucas, 2013).

Herrick and Bendrat (1900) established the Sandia Series in the Sandia Mountains of

New Mexico based on a section that was 46 m of shale, sandstone, and conglomerate, overlying Precambrian granite. The name Sandia Formation was first proposed by

Gordon (1907; Figure 4) and later Kelley and Northrop (1975) characterized the formation in the Sandia Mountains, Socorro County and neighboring areas to the south, including recognition of a basal, intermittent, thin carbonate sequence as Mississippian in age. The Sandia Formation is known for its mixed carbonate-siliciclastic units, and is characterized by thick quartz sandstone, gravel-bearing sandstones, conglomerates, and small limestone intervals. It rests on Proterozoic rock and is overlain by limestone of the

Gray Mesa Formation.

In the Sandia Mountains, the formation consists of abundant sandstone, shale, limestone, conglomerate, and siltstone. Lateral facies changes are present, siliciclastic beds are always dominant, and limestone beds may be scarce depending on locality.

Shale may be black, gray, or olive in color, and the formation has local coal seams and plant fossils. The Sandia is overlain by the Madera Group, which is now referred to as

Gray Mesa Formation. Toomey (1953) described the Sandia Formation in the northern

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Sandia Mountains as a dominantly siliciclastic unit, with a green quartzite, conglomeratic sandstone, cross-bedded sandstone and fossiliferous calcareous sandstone, gray to black fossiliferous shale, a red conglomeratic shale, and a fossiliferous limestone. The Sandia

Formation in the Sandia Mountains ranges in thickness from 15 to 90 m, and has a poorly constrained age.

Krainer and Lucas (2011) later re-described the Sandia Formation and established a lectotype for the unit in the Sandia Mountains (the Type Sandia section herein; Figure 10). The Sandia Formation rests with an erosional paleorelief on

Precambrian granite. The lower part consists of alternating shale, sandstone, pebbly sandstone, sandy limestone, and limestone. Dark grey to black shale in units 3.3 m thick contains carbonate concretions and plant fossils. Sandstones and pebbly sandstones occur in thin beds up to 4.2 m thick, whereas sandstone beds are massive and exhibit ripple lamination, cross-bedding, and swaley topography. These units also contain carbonate concretions and few fossil fragments, with pebbles that are up to 4 cm in diameter and shale intraclasts that are 10 cm long. Sandy limestone units range from 0.2 to 2 m thick that are massive and without internal bedding and contain mixed siliciclastic-carbonate sandstone or rudstone containing quartz grains and a few crinoidal packages, and limestone beds of 20 to 40 cm thick. The middle part of the formation is 20 m thick and dominated by limestone. The base is composed of a mixed siliciclastic limestone interval, while the upper 4 m is composed of cherty limestone. The upper part is dominated by cross-bedded, coarse-grained and pebbly sandstone, which fine-upwards and display large-scale trough cross bedding. Sandstone is exposed in units 10.4 m thick, while shale is not exposed but probably represented by covered intervals up to 0.5 to 2.7 m thick. The

Texas Tech University, Paul Alex Moore, May 2017 uppermost portion of the Sandia Formation is overlain by the cherty limestone of the

Grey Mesa Formation. Profusulinella was recovered from the upper Sandia Formation, indicating deposition during the middle to late Atokan (Krainer and Lucas, 2011).

To the north, in the Sangre de Cristo Range, the Sandia Formation is thickest, up to 1,555 m (Baltz and Myers, 1999). The Sandia Formation here is composed of dominantly shale that contains interbedded thin-to-thick sandstone beds and granule to pebble conglomerates, and a few thin limestone beds. Clay shale and argillaceous siltstone are common throughout the formation and range from a few centimeters up to

15 m in thickness. Shales range in color from dominantly gray to dark gray, but also display olive brown and yellowish to orange erosive colors. Calcareous shale, thin shaly limestone beds, and clay shale with limestone nodules are also present throughout the formation. Coaly shale is thin and discontinuous and mostly found in the lower Sandia of the southwestern and northeast areas. Sandstone beds range from a few centimeters to 9 m in thickness. In the north, larger sandstone units are thick, ranging up to 135 m in the vicinity of the Mora River, with grains that range in size from very fine sand to cobbles.

In the south, the larger sandstone units vary in grain size and shape. Here the clasts are irregularly shaped and subrounded, medium in size, and composed of translucent quartzite which are cemented together by silica, clay and iron oxide. Generally, from

Manuelitas Creek northward in the eastern mountains, sandstones are feldspathic.

Bedding of the sandstones ranges from thin to massive, with some parallel to subparallel bedding structures. Fossiliferous marine limestones are thin, ranging from a few centimeters to 0.6 to 0.9 m, and a few are as thick as 4.5 to 9 m in the lower and upper parts of the formation. Sandy limestone is common and generally grade into calcareous

Texas Tech University, Paul Alex Moore, May 2017 sandstone. Most limestones are micritic and contain fragments of brachiopods, gastropods, and other broken fossils. The upper 15 to 30 m of limestones in the Sandia contain Fusulinella, indicating deposition during the late Atokan. To the south, just east of the Bernal Fault, Fusulinella aff. F. devexa occurs in shaly limestone 27 m below the top of the Sandia Formation. The uppermost beds of the Sandia grade in to the lowermost beds of the Porvenir Formation as the number and thickness of limestone increases.

Krainer and Lucas (2013) described the Sandia Formation at Tecolote, located near the southern end of the Sandia Mountains. Here the Sandia Formation is 24 m thick, entirely siliciclastic and composed of fining-upward cycles. The lowermost portion is 8 m thick and is composed of conglomerate. It is overlain by a 6.2 m-thick, trough cross- bedded, coarse-grained, pebbly sandstone that grades upward into poorly exposed, fine- grained sandstone and finally into thin sandstone beds that contain marine fossils. This unit is overlain by shale bearing plant fossils, and fine-grained sandstone with ripple lamination. The top of the Sandia Formation is composed of 0.9 m thick, coarse-grained, partly pebbly sandstone displaying trough cross bedding overlain by the wavy bedded, fossiliferous gray limestone of the Grey Mesa Formation.

The Sandia Formation is 13.6 m thick near Cedro Peak in the Manzanita

Mountains, and rests upon the Proterozoic basement of phyllitic schist (Lucas et al.,

2013; Figure 13). The base of the Sandia is a 0.9 m thick, massive greenish sandstone with small quartz pebbles. Above this unit is a covered shale interval, overlain by 2.2 m of red mudstone to siltstone. The uppermost unit is a mostly covered interval of gray shale overlain by the cherty limestone of the Gray Mesa Formation.

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Myers (1982) described the Sandia Formation in the Manzano Mountains as a slope-forming sequence of siltstone, sandstone, and conglomerate, with a few discontinuous thin beds of marine limestone, which lies on Precambrian rock. The thickness ranges from 15 to 92 m, and averages 61 m. Most sections have basal conglomerates, which are overlain by sandstone, siltstone, and shale that contain plant and wood impressions. Overlying these units is a sequence of micaceous sandstone and siltstone, with lenticular beds of calcarenite. The upper section of the Sandia Formation is

21 m thick, and is transitional from terrigenous to marine environments. Shale and carbonates increase relative to sandstone and siltstone and chert is present in the upper 6 m of the section. Myers (1988) noted Atokan fusulinids, Fusulinella, from the Sandia

Formation at Sol de Mete Peak.

At the Priest Canyon section at the south end of the Manzano Mountains the

Sandia Formation is 70 m thick and overlies Precambrian granite (Lucas et al., 2016).

The lowest 0.4 m is composed of coarse-grained, pebbly, conglomeratic sandstone. The overlying 32 m of section consists of several sandstone units, with limestone beds and covered intervals. Individual sandstone units are 0.3 to 1.5 m thick and commonly trough cross-bedded with occasional horizontal laminations, with rare massive textures. The lowest observed limestone is 0.7 m thick and contains Fusulinella, along with

Syringopora and Chaetetes, which indicate a late Atokan age. The upper 38 m section comprises covered shale intervals with one exposed limestone that is 1.3 m thick.

Siemers (1983) studied the Pennsylvanian sections in the Soccoro Country region, including the Magdalena, Lemitar, southeast San Mateo, and northern Oscura Mountains,

Sierra Ladrones, Joyita Hills, Little San Pasqual Mountain, and the Cerros de Amado

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(Kues, 2001). The Sandia Formation overlies Precambrian granite or Ordovician limestones that survived erosional episodes during the Devonian, Mississippian and early

Pennsylvanian. The Sandia varies in thickness from 10 to 211 m and averages 116 m.

The thickest sections are found in the north- to northwest through the central part of the region. The Sandia Formation consists of diverse carbonate and terrigenous lithologies.

Terrigenous siliciclastics dominate the formation, but the southern region displays higher ratios of carbonate to siliciclastic sediments. Most sandstones are grain-supported arenites, which have poorly sorted angular to subangular grains. In the southern region, sandstones are finer grained and better sorted. Fossil fragments consist primarily of crinoids and gastropods in lower sandstones. Sandstone bedding in the Sandia ranges from thin to very thick, and has little vertical consistency, with most sandstone falling into the medium- to thick-bedded range. Lateral continuity of sandstones is difficult to infer due to the slope cover. Other features include thin, sub-parallel, continuous planar and wavy laminations, with occasional low-angle cross-laminations. Carbonates contribute to a small portion of the Sandia Formation, and are medium-gray to black mudstones, wackestones, and packstones.

South of the Cerros de Amado, the Sandia Formation interfingers with, and is replaced by the Red House Formation, the northernmost occurrence of which is at San

Pasqual Mountain in southern Socorro County (Lucas et al., 2012). The two formations differ primarily in the presence of substantial beds of quartzose sandstone in the Sandia

Formation versus the presence of common limestone beds in the Red House Formation

(Krainer et al., 2011). The Red House Formation extends southward, through the Fra

Cristobal, Mud Springs, and Caballo Mountains into the Derry Hills in Sierra County.

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Gray Mesa Formation

The Sandia Formation is overlain by the carbonate-dominated Gray Mesa

Formation except in the Sangre de Cristo Mountains, where the carbonates of the

Porvenir Formation overlie the Sandia. The Gray Mesa Formation was first assigned by

Kelley and Wood (1946) as a division of the Madera Formation (Figure 4), and was referred to as the "Gray Mesa." For many decades, the Gray Mesa was informally called the "lower gray limestone member of the Madera Formation" (Nelson et al., 2013). The

Gray Mesa wasn't recognized formally as a formation until Kues (2001) recommended that the lower gray limestone unit be promoted from a member to a formation, with the

Grey Mesa being the oldest formal name (Nelson et al., 2013).

The Gray Mesa Formation is a unit composed of primarily limestone, in contrast to the formations above and below, which have higher proportions of siliciclastic rocks, and in most sections, 70 % or more of the Grey Mesa Formation is composed of limestone (Nelson et al., 2013). The Grey Mesa is often recognized as a resistant cliff- forming unit, with indistinctly bedded, massive limestones, but with closer inspection, these cliffs show thin bedding separated by clay or stylolitic partings. Cherty limestone of the Gray Mesa Formation is often massive to indistinctly bedded, medium to thick bedded, wavy bedded and nodular, while non-cherty beds are commonly thin and wavy bedded (Nelson et al., 2013). Fossils often found in the Gray Mesa include echinoderm fragments, brachiopods, fusulinids, bryozoans, calcareous algae, solitary corals, and

Syringopora, and Zoophycos, while Chaetetes is common near the base of the formation

(Nelson et al., 2013). Chert makes up 10 to 50 % of beds in the Gray Mesa Formation,

Texas Tech University, Paul Alex Moore, May 2017 and occurs as gray, brown, and black chert (Nelson et al., 2013). Most of the sections in the Gray Mesa contain interbeds of shale, siltstone, and sandstone, but conglomerate and non-fissile mudstone are more rare.

The lower Grey Mesa Formation overlies the Sandia Formation in the north, and

Red House Formation to the south. Generally the contact is placed where the sections turns to limestone, and in particular where the limestone is cherty. The contact at the base of the Grey Mesa may be planar, irregular, and sharp, or there may be a gradation from calcareous shale to shaly limestone. The Gray Mesa Formation stretches across most of central New Mexico from the Nacimiento Mountains in the north to the Caballo and San

Andres Mountains on the south (Nelson et al., 2013). To the east, the boundaries include

Sangre de Cristo Range south through the Sandia, Manzano, Oscura, San Andres, and northern Organ Mountains, and the western limit is the San Juan Basin and west of the

Lucero Uplift, Magdalena Mountains, and Mud Springs Mountains (Nelson et al., 2013).

Krainer and Lucas (2004) documented the type section of the Gray Mesa

Formation in the east-facing escarpment of Mesa Aparejo in the Lucero uplift. At the type section, the Gray Mesa Formation is 388.5 m thick and is divided into three informal members: lower member (185.5 m), middle member (65 m), and upper member (138 m).

The lower member overlies the Sandia Formation, and is characterized by thick- to thin- bedded, gray fossiliferous limestone with chert nodules and silicified fossils and

Chaetetes, limestone that is massive to indistinctly bedded and contains silicified fossils.

Sandstones in the lower member are coarse-grained, poorly to moderately sorted, carbonate-cemented quartz arenite that contains mostly subangular grains. The middle member of the type Gray Mesa section is characterized by 12 m of bedded marly

Texas Tech University, Paul Alex Moore, May 2017 limestone. This section is recognized by a bedded fossiliferous gray limestone unit that is

0.6 to 3 m thick in which individual beds are 0.2 to 0.5 m thick, a meter-thick cherty limestone unit, and a 5.5 m thick massive algal limestone unit. The upper member consists of thin- to thick-bedded fossiliferous limestone, in beds 0.3 to 5.5 m thick and mostly wackestone, phylloid algal limestone, cherty limestones, limestone beds with intercalated marl, and a few 0.5 m thick sandstone intervals.

The Gray Mesa in the Sandia Mountains was first distinguished by Kelley and

Northrop (1975). Wiberg and Smith (1994) described the nature and origin of cyclicity in the Madera Limestone (including the Gray Mesa) in the Sandia Mountains. Repetitive cycles were recognized as transgressive-regressive deposits represented by alterations of deepening and shallowing water facies. Wiberg and Smith (1994) reported that 15 T-R cycles in the Madera Limestone are laterally continuous and could be could be correlated with the fusulinid zones of the Manzano Mountains of Myers (1988). The 15 "lower

Madera" cycles were correlated with a range of time corresponding with the early to middle Desmoinesian Beedeina arizonensis to B. girtyi zones, as discussed by Myers

(1988). Lucas et al. (1999) extended the names of the Los Moyos Limestone and the

Wild Cow Formation from the Manzano Mountains (Meyers, 1982) to the Sandia

Mountains. Later, however, Lucas et al. (2013) recommended that Myers’s names be dropped and older names, including Gray Mesa be applied.

The Gray Mesa Formation at Cedro Peak in the northern Manzanita Mountains contains higher proportions of limestone relative to shale, and very little sandstone compared to the sections in the Sandia Mountains. Here, the three members of the Gray

Mesa Formation have been recognized in the more southern sections, in ascending order,

Texas Tech University, Paul Alex Moore, May 2017 the Elephant Butte Member (47 m), Whiskey Canyon Member (30 m), and Garcia

Member (42 m) (Lucas et al., 2013). The exposed limestones of the Elephant Butte

Member are often 4.9 m thick and are often cherty. Non-cherty limestones are composed of thin, wavy-bedded, crinoidal limestones, and some algal limestones. The Whiskey

Canyon Member is mostly cherty limestone that is wavy, massive to thick bedded with some nodular limestones. The Garcia Member consists of a mixture of siliciclastic units

(sands and sandstones) interbedded with relatively few cherty limestone beds. Vachard et al. (2012, 2013) documented the fusulinids Profusulinella fittsi and Dagmarella iowensis in the Elephant Butte Member, which indicate a latest Atokan to earliest Desmoinesian age. Typical Desmoinesian fusulinids, Beedeina and Wedekindellina species, occur in the Whiskey Canyon and Garcia members.

Read and Wood (1947) used Gordon's (1907) division of the Pennsylvanian section in the Manzano Mountains into the Madera Formation of the Magdalena Group, and subdivided the Madera into the lower "gray limestone" and the upper "arkosic" limestone members (Kues, 2001). Meyers (1982) described the Los Moyos Formation of the Madera Group, which is now referred to as lower Gray Mesa Formation (Lucas et al.,

2013). The Gray Mesa Formation is about 180 m thick, and is a resistant cliff-forming unit that overlies the Sandia Formation. The contact between the underlying Sandia

Formation and the overlying Gray Mesa Formation is gradational. The lower 60 m of the

Gray Mesa are medium gray calcarenites that contain lenses of chert and interbedded shale. Fusulinids include Beedeina arizonensis, Fusulinella famula, and primitive species of Wedekindellina, which indicate an early Desmoinesian age. Lucas et al.

(2016) described the Gray Mesa section in Priest Canyon section in the southern

Texas Tech University, Paul Alex Moore, May 2017

Manzano Mountains. The Elephant Butte Member is about 24 m thick and is dominantly limestone, with minor amounts of chert. Limestone units are 0.6 to 4.5 m thick and are separated by covered shale intervals that are 0.4 to 1.0 m thick. The base of the member contains silicified Chaetetes, brachiopods and corals. The Whiskey Canyon Member is about 84 m of mostly very cherty limestone with common covered intervals. The base of the Garcia Member is a thin sandstone that fills fissures in the uppermost bed of the

Whiskey Canyon. The non-cherty and algal limestones are more common than in the

Whiskey Canyon, but much of the Garcia consists of covered intervals.

Siemers (1983) and Lucas et al. (2009) described the essential features of the

Pennsylvanian section in the Soccoro County region. Siemers (1983) used the term lower

"gray limestone" in the Magdalena Group to describe the Gray Mesa Formation. Lucas et al. (2009) provided more details of the Pennsylvanian stratigraphy and biostratigraphy in the Cerros de Amado area, east of Socorro. The transition between the terrigenous

Sandia Formation and the carbonate Gray Mesa Formation is either rapid where the units may be distinctly seen, or gradational and may be more difficult to pick apart. The thick

Elephant Butte Member (95 m) consists of a variety of thin- to thick-bedded limestones

(nodular limestones, cherty limestone, massive algal limestones, and some intraformational limestone conglomerates). Thin (<1 m) quartz sandstones occur in the lower part, and a thick, 10 m, coarse, pebbly, cross-bedded quartz sandstone occurs 30 m above the base of the member. The lower part of the thinner Whiskey Canyon Member

(35 m) is 25 m of very cherty, fossiliferous limestone. The Garcia Member (at least 55 m thick) is composed of a mixture of siliciclastics (shales and sandstones) thick-bedded crinoidal limestone and less common algal limestones.

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Baltz and Myers (1999) mapped three facies of the Porvenir Formation, the Gray

Mesa equivalent, in the Sangre de Cristo Mountains. The southern facies is composed of limestone, yet with a higher proportion of sandstone than further south, while northward, the limestone grades into sandstone-shale-limestone facies that contains coarser siliciclastics, and toward the northwest, limestone largely gives way to dark shale. These changes may infer proximity to the tectonically active eastern Uncompahgre uplift and to the Taos trough, which sunk rapidly during the Middle-Pennsylvanian (Nelson et al.,

2013). Fusulinids obtained include Beedeina cf. insolata and B. aff. apachensis. Treat’s

(2014) analysis of conodont faunas indicated that the lower part of the Porvenir was latest

Atokan to early Desmoinesian in age.

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Figure 4. Previous, and current nomenclature and division of the lower Pennsylvanian strata (Lucas et al. 2014)

Texas Tech University, Paul Alex Moore, May 2017

Chapter 4 Middle Pennsylvanian chronostratigraphy and biostratigraphy in North America

The Atokan-Desmoinesian boundary

Faunas from late Atokan and early Desmoinesian strata are poorly represented in

Midcontinent North America because of a major unconformity near the base of the

Desmoinesian throughout the region. For this reason, uncertainty about the exact position of the base of the Desmoinesian makes precise biostratigraphic correlation difficult. The underlying Atokan Series was originally defined based on sections in southeastern

Oklahoma, the upper portions of which are non-marine strata (Taff and Adams, 1900;

Spivey and Roberts, 1946; Moore and Thompson, 1949). The type area for the

Desmoinesian Stage is in central Iowa, where Desmoinesian strata rest unconformably on

Mississippian and older units (Keyes, 1893; Moore and Thompson, 1949). Fusulinids have served as the primary means for identification and correlation of the base of the

Desmoinesian for a number of years, and only much later have attempts been made to use conodont faunas.

It was originally accepted that the Zone of Fusulinella (Fl.;Figure 5) represented upper Atokan through lower Desmoinesian strata (Thompson, 1945). Later, Thompson

(1948) revised the definition of the top of the zone to a datum just below the first occurrence of Fusulina (Beedeina for most workers). Earlier, Thompson (1934) had noted that fusulinids from the Desmoinesian stratotype in Iowa, in particular, Fusulinella iowensis, a transitional species between Fusulinella and Fusulina and closely related

Texas Tech University, Paul Alex Moore, May 2017 species (Fl. stouti, Fl. leyi, and Fl. famula) had been reported from Atokan-Desmoinesian boundary intervals across North America (Wahlman, 2013; Figure 5). Fusulinella iowensis occurs sometimes with older species of fusulinids, but more commonly with primitive species of Beedeina, the appearance of which characterizes the Zone of

Beedeina, or the Desmoinesian in fusulinid biostratigraphy. Thus, Fl. iowensis appears to be restricted to a narrow stratigraphic zone around the Atokan-Desmoinesian boundary

(Wahlman, 2013). However, it is unclear whether beds with Fl. iowaenis without

Beedeina should be considered latest Atokan or earliest Desmoinesian in age. Currently, in the fusulinid zonation, the base of the Desmoinesian in the Midcontinent region is defined by the Beedeina insolita-B. leei zone (Figure 5), with Wedekindellina present in the upper area of this zone (Wahlman, 2013). The oldest species of Beedeina appears to be B. insolita.

Fusulinids have been used to approximate the base of the Desmoinesian in New

Mexico. Needham (1937) reported fusulinids from a number of localities in New

Mexico, but it was Thompson (1942) who presented a systematic summary of

Pennsylvanian stratigraphy in New Mexico based on fusulinid faunas. Thompson (1942) proposed the Derry Series as the chronostratigraphic unit underlying the Desmoinesian

Series in New Mexico. The uppermost portion of the Derry Series was Thompson's

Cuchillo Negro Formation (Mud Springs Group) in the Mud Springs Mountains, which corresponds with the upper part of the Zone of Fusulinella (Figure 5). The base of the

Desmoinesian Series was placed at the base of the overlying Elephant Butte Formation

(Armendaris Group), where primitive Fusulina (Beedeina) appears in association with

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Fusulinella. Most subsequent work on the biostratigraphy of Middle Pennsylvanian strata in New Mexico has relied on this definition (e.g., Kottlowski, 1960; Myers, 1988).

Clopine (1992) restudied the fusulinid faunas of the Derryan Series in its type region in the Mud Springs and Caballo Mountains. He confirmed the observation that at the Whiskey Canyon section common Fusulinella devexa occur with rare Beedeina insolita. In the overlying beds several additional species of Beedeina appear. He stated that the first occurrence of Beedeina was the best indicator of the base of the

Desmoinesian, and that Fusulinella ranged from the Atokan into earliest Desmoinesian time.

Few papers have described conodont faunas across the Atokan-Desmoinesian boundary in Midcontinent North America. Sutherland and Grayson (1992) discussed the conodont biostratigraphy of Morrowan and Atokan strata in the Ardmore Basin,

Oklahoma. Uppermost Atokan strata of the Bostwick Member of the Lake Murray

Formation yielded Declinognathodus marginodosus, Neognathodus atokaensis, and an un-described new species, N. "bothrops." From the higher Lester Limestone, which has an early Desmoinesian fusulinid fauna (Waddell, 1966), they reported the presence of N. bothrops and N. medadultimus (=N. caudatus, see below). The base of the Desmoinesian was placed 40 feet below the base of the Lester, where Fusulina (Beedeina) insolita was reported by Waddell (1966).

Lambert (1992) reported Neognathodus caudatus, Idiognathodus amplificus, I. obliquus and I. sp. B from the lowest Desmoinesian strata (marine interval above the

Cliffland Coal) in Iowa. Based on Lambert's work, Barrick et al. (2004) suggested that N.

Texas Tech University, Paul Alex Moore, May 2017 caudatus (the N. caudatus Zone; Figure 6) could be used to recognize basal

Desmoinesian strata. This zone is defined as the first appearance of N. caudatus. This species has also been recovered from the Lester Limestone in the Ardmore basin

(Sutherland and Grayson, 1992; Barrick et al., 2013) and the Hugoton Embayment of western Kansas (Youle et al., 1994).

Boardman et al. (2004), and Marshall (2010) provided additional information on early Desmoinesian conodonts from the Arkoma Basin in east-central Oklahoma. Here the upper Atokan (Hartshorne Formation) is entirely nonmarine and the lowest marine beds, the McCurtain Shale Member, lies at the base of the overlying McAlester

Formation (Fay et al., 1979). The McCurtain Shale Member has been used as the

"traditional" base of the Desmoinesian in the Arkoma Basin. Boardman et al. (2004) reported I. praeobliquus from the McCurtain, but Marshall (2010) re-identified the fauna as forms of I. cf. praeobliquus and I. amplificus. Boardman et al. (2004) reported

Neognathodus bothrops, while Marshall illustrated a form he incorrectly identified as N. caudatus (probably N. colombiensis). Marshall (2010) traced the marine units

(cyclothems) out of the Arkoma Basin into the Kansas subsurface and showed that the marine interval above the Cliffland Coal in Iowa was probably equivalent to the Doneley cyclothem in the Arkoma Basin, two cyclothems higher than the McCurtain cyclothem

(Figure 6). Neognathodus caudatus occurs in the Doneley cyclothem and ranges into the overlying Inola cyclothem as does I. obliquus (Marshall, 2010). Barrick et al. (2013) updated their Midcontinent zonal scheme to incorporate these new data, but did not make any changes to the zonation.

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In New Mexico, Foster (1995) sampled for conodonts across the Atokan

(Derryan)-Desmoinesian boundary at the Whiskey Canyon section in the Mud Springs

Mountains, where Thompson (1942) and Clopine (1992) had reported the presence of

Beedeina insolita. She showed that Neognathodus bothrops appeared just above the first occurrence of B. insolita at the Whiskey Canyon section, but that it occurred with the late

Atokan fusulinid Fusulinella devexa at the nearby Cuchillo Peak section.

Saelens (2014) described the conodont faunas of the Red House Formation and the base of the overlying Gray Mesa Formation in the Caballos and Mud Springs

Mountains (Figures 1 and 7). She recognized four faunal intervals, the uppermost ones of which appear to cross the Atokan-Desmoinesian boundary. Her Faunal Interval 3 lies above the highest occurrence of Neognathodus uralicus. Neognathodus uralicus occurs throughout the southern Midcontinent and represents the middle Atokan (Barrick et al.,

2013). Idiognathodus incurvus II, Idiognathodus gibbus I, Idiognathoides ouachitaensis, and Declinognathodus marginodosus persist from lower intervals into the lower levels of

Faunal Interval 3. Idiognathodus gibbus II, Neognathodus sp. B1, and N. sp. B2 appear in this interval, with N. bothrops appearing near the top of the interval. This faunal interval lies just below the lowest Beedeina (Clopine 1992) and co-occurs with the Fusulinella

Zone, making it late Atokan in age. Saelens's (2014) Faunal Interval 4 occurs at the top of the Red House Formation, and at the base of the Grey Mesa Formation and represents the first occurrence of Idiognathodus sp. H with Neognathodus bothrops. The base of Faunal

Interval 4 was interpreted to correspond approximately with the base of the

Desmoinesian.

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Treat (2014) distinguished conodont faunal intervals in the uppermost Sandia

Formation and the Porvenir Formation in the southern Sangre de Cristo Mountains of northern New Mexico (Figures 1 and 8). Faunal Interval 1 occurs in the uppermost

Sandia and the lowermost Porvenir, and is characterized by Idiognathodus sp. I, which occurs with I. sp. G, Neognathodus bothrops, and Diplognathodus orphanus. Faunal

Interval 2 occurs in the lower Porvenir, and is characterized by the appearance of

Idiognathodus sp. HI, and includes the first occurrences of N. caudatus, and D. coloradoensis. Baltz and Myers (1999) reported Beedeina cf. B. insolita from the lower

Porvenir in beds assigned to Faunal Interval 2 at the Type Porvenir section, from a level above the first occurrence of I. sp. HI (Treat, 2014). Treat (2014) indicated that the first occurrence of I. sp. HI (= I. sp. H of Saelens, 2014) appears to correspond more closely with the base of the Desmoinesian than any other conodont species.

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Figure 5. Fusulinid zonation of Midcontinent North America (from Wahlman, 2013).

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Figure 6. North American Midcontinent conodont zones (from Barrick et al., 2013).

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Figure 7. Conodont intervals of the Red House Formation and lower Gray Mesa Formation in Caballos and Mud Springs Mountains (from Saelens, 2014).

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Figure 8. Conodont intervals of the Sandia and Porvenir Formations in the Sangre de Cristo Mountains of New Mexico (from Treat, 2014).

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Figure 9. Conodont zones of Barrick et al. (2013) compared with faunal intervals of Saelens (2014) Treat (2014).

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Chapter 5 Methods and Stratigraphic Sections

Methods

Five sections of the Sandia Formation and lower part of the Gray Mesa Formation were sampled for conodonts (Figures 10-18). The Type Sandia section and the Tejano

Highway section lie in the southern Sandia Mountains. The Cedro Peak Z section sits to the south in the northern Manzanita Mountains. The Sepultura Canyon section is located in the southern Manzano Mountains and the Presilla B section lies further to the south in the Cerros de Amado area east of Socorro.

Bulk samples of three to four kilograms were collected from beds in each of the sections in conjunction with stratigraphic and sedimentological research by Spencer G.

Lucas (New Mexico Museum of Natural History) and Karl Krainer (University of

Innsbruck). Most sections were sampled by J. Barrick at the time when the sections were originally measured. The Type Sandia and Tejano Highway sections were sampled later by the author and J. Barrick with the assistance of S. Lucas, using previously prepared stratigraphic sections. Samples from the Sepultura section were collected by S. Lucas.

The bed numbers used here correspond with bed numbers used in their stratigraphic sections. In the Sandia Formation, beds that were mostly carbonate and showing skeletal grains were preferentially sampled, including some beds with obvious quartz sand grains.

In the Gray Mesa Formation, beds with concentrations of skeletal grains were preferentially sampled, whereas those composed largely of carbonate mud were generally not sampled.

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Initially about 1.3 kg of the sample was dissolved in fully buffered formic acid. If the sample yielded a conodont fauna, then the remainder of the sample was processed.

Many insoluble residues contained moderate to significant amounts of quartz sand and conodonts were concentrated using heavy liquids. SEM images were obtained using the

Hitachi S-570 in the College of Arts and Sciences Microscopy Center.

Type Sandia Section

Krainer et al. (2011) described the lectostratotype for the Sandia Formation on the eastern side of NM Highway 536, southeast of Doc Long Picnic Area in Cibola National

Park (Figure 12). The section is approximately 123.8 m thick and composed of sandstone/conglomerate, covered shale intervals, and limestone. The lower 69 m rest on

Proterozoic granitic rocks, and consist of alternating shale, sandstone, pebbly sandstone, sandy limestone, and limestone. Shale units measure up to 3.3 m thick, and are commonly micaceous with poorly developed fissility. Sandstones and pebbly sandstones are present as thin layers up to 30 cm thick and units as thick as 4.2 m. Some sandstones contain carbonate material, and a few fragments of brachiopods and crinoids. Sandy limestone horizons range from 0.2 to 2 m in thickness, and lack internal bedding. Some thicker limestone intervals are bedded, and bed thicknesses range from 20 to 40 cm.

Sandy limestone is composed of either mixed siliciclastic-carbonate sandstone or rudstone containing quartz grains. Some crinoidal packstone is present. Limestone beds, much like the sandy limestone intervals, are 0.2 to 2 m thick, gray, fossiliferous, and micritic.

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The middle portion of this section, the "middle limestone member," is 21 m thick, and is composed of bedded gray limestone, with chert nodules in the upper 3.9 m, and a thin limestone bed containing abundant bryozoans. Bedding is slightly wavy, with bed thicknesses of 10 to 30 cm. The upper unit, or the "upper sandstone member" has a sharp contact with the underlying limestone member. This portion is coarse grained, has cross bedding, and is dominated by pebbly sandstones. The sandstone unit here is 10.4 m thick, and shale is represented by covered intervals that are 0.5 to 2.7 m thick. All sandstone units fine upward, and display large trough cross bedding. The uppermost sandstone is overlain by gray, cherty limestone of the Gray Mesa Formation.

The lowermost part of the Sandia Formation in this section yielded the fusulinid

Eostaffella pinguis, which suggests a late Morrowan to early Atokan age (Krainer et al.,

2011). Profusulinella occurs in the upper part of the Sandia and in the base of the Gray

Mesa Formation at this locality, which is representative of a middle to late Atokan age.

Tejano Highway Section

Smith (1999) described the limestone-siliciclastic cycles exposed in the Tejano

Canyon section in roadcuts along NM Highway 536 in the Cibola National Park on the east flank of the Sandia Mountains in northern New Mexico. The Sandia Formation is approximately 55 m-thick, and consists of sandstone and interbedded shale and limestone, while the overlying Madera Formation (=Gray Mesa Formation) consists of a lower 140-m thick, cliff-forming interval composed of limestone, and a 260-m thick upper interval composed of sandstone, limestone and shale. Smith (1999) interpreted the

Tejano Highway section as an uninterrupted succession in which he distinguished 29

Texas Tech University, Paul Alex Moore, May 2017 transgressive-regressive cycles. In contrast, S. Lucas and B. Allen (personal communication, 2016) proposed that the Tejano Highway section should be divided into four partial sections that represent multiple fault blocks (Figures 13, 14). Section 1

(Figure 13) represents the first fault block, which is roughly 40 m of sandstone, limestone, and shale, with few conglomerate beds. Sandstones in this section are 2 to 5 m thick, and range from massive to largely cross-bedded. Limestones are generally 2 to 3 m thick, and are either massive, wavy-bedded, or may be mixed with siliciclastic sediments.

Section 2 (Figure 13), the second fault block, is 35 m thick, and is dominated by sandstone units, with a few large massive limestone units, interbedded shales, and sparse conglomerates. Sandstones units are generally 2 to 8 m thick, with smaller units being 0.5 to 1 m thick. Thick sandstones are dominantly cross-bedded, whereas thinner sandstones are massive. Limestones, which are 1 to 3 m thick, display wavy-bedded textures and sandy limestones are massive. Section 3 (Figure 13), or fault block 3, is composed of shale units and interbedded shale, sandstone, shaly sandstones, and limestone. At the base of the section is a sandstone that is roughly 5 m thick, which exhibits a shaly base and coarsens upward. An upper sandstone unit is dominated by cross-bedded textures.

Limestones are massive to wavy bedded, and may be sandy. The larger units range from

2 to 5 m thick, and smaller units may be a meter or thinner. Section 4 (Figure 14), the final fault block, is composed of shale and interbedded shale, sandstone, and limestone.

Shale intervals are 1 to 2 m thick. Sandstone units may be as thick as 4 m, or occur as small lenses in shales. Sandstones in this section are either massive or display cross bedding. Limestones are either massive or wavy-bedded, and may be as thin as less than

1 m or range up to 5 m thick.

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Cedro Peak Z Section

Lucas et al. (2014) measured a section of the uppermost Sandia Formation and lower Gray Mesa Formation (Elephant Butte Member) at Cedro Peak in the Manzanita

Mountains of Bernalillo Country, New Mexico (Figure 15). Only a few meters of the

Sandia are exposed and the topmost limestone is separated from the basal cherty limestone of the Gray Mesa by less than a meter. About 45 m of the lower Gray Mesa section is discontinuously exposed, most of which is cherty wackestones and uncommon packstone lenses.

Sepultura Canyon

A relatively complete section of the Sandia and lower Gray Mesas formations occurs at Sepultura Canyon, in the Los Pinos Mountains of Socorro Country. Krainer et al. (in press) described the section at Sepultura Canyon (Figure 16). The Sandia

Formation at Sepultura Canyon is unusually thick, 172 m. The Sandia Formation can be divided into three units. The lower unit (18.4 m) is dominated by conglomerate, sandstone, and covered intervals, which overly Proterozoic granite. At the top of this section are two covered intervals that are capped by a quartzose sandstone that displays trough cross bedding. The middle unit (11.3 m) is dominated by shale-siltstone with intercalated greenish siltstone to fine-grained sandstone, black micaceous limestone, and two thin limestone beds. The upper unit is a thick succession (145.5 m) of conglomerate and sandstone with intercalated shale and limestone. Conglomerates are massive, trough cross-bedded, and poorly sorted. Commonly sandstones are fine- to coarse-grained with occasional pebbles, and display trough cross bedding. Massive sandstone units are

Texas Tech University, Paul Alex Moore, May 2017 intercalated in the lower section. Six limestone intervals are intercalated in this section.

These limestones are massive and bedded, and may contain fossils. The top of the Sandia

Formation is identified by quartzose sandstone, overlain by beds of cherty limestone comprising the base of the Gray Mesa Formation.

The Gray Mesa Formation at Sepultura Canyon is thin, only 45 m, relative to the northern and southern localities. The lower Gray Mesa Formation consists of wavy bedded fossiliferous limestone with abundant chert nodules. The middle portion of the

Gray Mesa Formation is composed of thin wavy bedded cherty limestone, with massive chert intervals. The upper part of the Gray Mesa Formation has a covered interval, followed by a fossiliferous wavy bedded limestone with chert nodules.

Presilla A and B Sections

Lucas et al. (2009) measured the Sandia Formation at Arroyo de la Presilla

(Presilla A, Figure 17), located at the eastern flank of the Rio Grande rift about 8 km to the northeast of Socorro in the hills of the Cerros de Amado, New Mexico. The Sandia

Formation here is 162 m thick, and rests on a granitic Proterozoic basement. The Sandia consists of cyclic siliciclastic and carbonate strata, representing nonmarine, and marine strata formed during transgressive-regressive cycles.

The base of the Sandia is 2 m of conglomerates that are quartz rich, with a maximum grain size of 3 cm. The conglomerates grades upward into pebbly sandstone and sandstone, and upper conglomerates that are typically 1 m thick. Sandstone is coarse- grained, pebbly and commonly trough cross-bedded, and rarely display planar cross bedding. Sandstone is quartz rich, reddish and contains individual quartz grains of 1-2 cm

Texas Tech University, Paul Alex Moore, May 2017 in diameter. The sandstone intervals are up to 4.7 m thick, upward fining and composed of multistoried channels. Thick siltstone to fine-grained sandstone intervals of 1.2 -4.7 m occur in the lower Sandia, and are also developed on top of the conglomerate and sandstone units which are up to 1.3 m thick and as thin as 0.3 m in the shale. Facies include horizontally laminated and ripple-laminated siltstone and fine-grained sandstone, with few small scale cross bedding. The "fire clay" in the lower part of the section is light gray claystone, 0.5 m thick and contains plant fossils, which is underlain by dark gray laminated silty clay containing plant fossils (Krainer and Lucas, 2013). Between 21 to 26 m above the base of the Sandia Formation, is a greenish-brown silty shale with a thin micaceous sandy siltstone in the lower part, and a thin fossiliferous limestone in the upper part. In the lower Sandia, only one thin limestone bed (10-20 cm) is exposed, which is either a wackestone or packstone with brachiopods and bryozoans.

The next 46 m of the Sandia comprise siliciclastic strata with several intercalated fossiliferous limestone horizons, while the remaining 70 m are dominantly siliciclastic beds with thin limestone beds in the upper part. Middle and upper limestone intervals are

0.3 to 2.2 m thick, and brownish weathered, gray to dark gray, 5 to 30 cm thick beds.

Limestones are typically coarse grained, sandy and fossiliferous with fragments of crinoids, brachiopods, bryozoans, and corals. Rarely the limestones display cross bedding, or appear massive, and microfacies include wackestone, packstone, floatstone, and rudstone (Krainer and Lucas, 2013).

Textural and structural properties of the sandstone and conglomerates at the bases of the cycles, including erosional bases, trough cross-bedding, poor sorting and rounding, and fossil plants, indicate fluvial origin. The cross-bedded, mixed siliciclastic-carbonate

Texas Tech University, Paul Alex Moore, May 2017 sandstone in the upper part of the section, contains abundant fossils, and formed in a shallow marine, high energy nearshore environment, and the siltstone to fine-grained sandstone and shale is of nonmarine and deltaic to shallow marine origin (Krainer and

Lucas, 2013).

Lucas et al. (2009) documented and measured 192.6 m of Grey Mesa Formation at the Presilla B section (Figure 18). The Grey Mesa Formation was divided, in ascending order, into the Elephant Butte Member (95 m), Whiskey Canyon Member (35 m), and the

Garcia Member (55 m). The Elephant Butte Member consists of multiple limestone types, covered shale intervals, two thin sandstone beds, two thin limestone conglomerates, and a

10 m thick sandstone interval, which displays an erosive base overlain by a coarse, pebble quartzitic sandstone that is cross bedded. Limestone units range from individual beds 0.1 m thick to intervals of multiple beds as thick as 6.4 m. Limestones were divided into different types; thin, wavy-bedded limestone with bed thickness of 10 to 20 cm; thick-bedded limestone, with bed thickness of 20 to 50 cm; thick-bedded, coarse crinoidal limestone; massive to indistinctly bedded algal limestone, 0.9 to 1.8 m thick; and wavy, thin bedded to nodular cherty limestone, 10 to 20 cm thick (Lucas et al., 2009).

Fusulinid biostratigraphy in Cerros de Amado region is incomplete due to patchy distribution of fusulinids in Pennsylvanian strata, but conodonts were reported from the

Sandia Formation and the Lower Gray Mesa Formation, Elephant Butte Member (Lucas et al., 2009). Only one sample from the Sandia yielded sufficient conodonts, unit 27, 47 m above the base of the formation, with the Atokan species, Idiognathodus incurvus, and

Declinognathodus marginodosus. Conodonts from the lower 60 m of the Elephant Butte

Member were reported as I. obliquus, Diplognathodus coloradoensis, Neognathodus

Texas Tech University, Paul Alex Moore, May 2017 bothrops, and N. colombiensis, interpreted to be an early Desmoinesian fauna. A higher conodont fauna from the Elephant Butte Member was obtained 65 m above the base with

N. asymmetricus, which also indicates an early Desmoinesian age.

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Figure 10. Map of the study sections; the Tejano HIghway section in the Sandia Mountains, the Type Sandia section in the Sandia Mountains, the Cedro Peak section in the Manzanita Mountains, the Sepultura Canyon section in the Los Pinos Mountains, and the Presilla A & B section at Cerros de Amado (modified from Lucas et al., 2014).

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Figure 11. Cross sections of the study areas from north to south. Faunal intervals have also been adjusted to help elaborate on the position of the Atokan-Desmoinesian boundary.

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Figure 12. Stratigraphic column of Type Sandia Section (from Krainer et al., 2011). Conodont samples are located using bed numbers on the left side of the column.

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Figure 13. Stratigraphic column of sections 1, 2, and 3 of the Tejano Highway Section. Each partial section may belong to separate fault blocks. (S. Lucas and B. Allen, 2016, unpublished).

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Figure 14. Stratigraphic column of section 4 of the Tejano Highway Section. This partial section may belong to a separate fault block than sections 1, 2, and 3 (S. Lucas and B. Allen, 2016, unpublished).

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Figure 15. Stratigraphic column of the Cedro Peak Z section (from Lucas et al., 2014).

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Figure 16. Stratigraphic column of the Sepultura Canyon section (from Krainer et al., in press).

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Figure 17. Stratigraphic column of the Arroyo de Presilla A section (from Lucas et al., 2009).

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Figure 18. Stratigraphic column of the Arroyo de Presilla B section (from Lucas et al., 2009).

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Chapter 6 Conodont biostratigraphy of the Sandia and lower Gray Mesa Formations

Six succession faunal intervals (FI) defined by first and last occurrences of conodont species can be recognized from the Sandia Formation and lower part of the

Gray Mesa Formation. These faunal intervals are interpreted to range in age from the middle Atokan into the early Desmoinesian.

Faunal Interval 1

The lowest of the intervals, Faunal Interval 1, is defined by the presence of

Neognathodus atokaensis and N. uralicus (Figure 19). This interval was recovered only from the base of the Sandia Formation at the Type Sandia section (unit 8).

Faunal Interval 2

Faunal Interval 2 (Figure 19) is split into two parts, a lower 2a and an upper 2b.

Interval 2a is defined by the first occurrence of Neognathodus pre-colombiensis, and contains N. atokaensis and N. uralicus. Other species to make their first appearances in this interval are Idiognathodus sp. Q, I. sp. Q2, I. sp. Z, N. bassleri, Idiognathoides sp., and Declinognathodus marginodosus. Interval 2a occurs in the Sandia immediately above

FI 1 in the lower Sandia Formation at the Type Sandia section (unit 10). Above this, specimens of N. bassleri were recovered (unit 28) and higher (unit 43), I. sp. Q2 appears.

The upper part, FI 2b, is defined by the first occurrence of Idiognathodus gibbus.

Neognathodus pre-colombiensis, N. bassleri, I. sp. Q, and I. sp. Q2 persist from FI 2a.

Late forms of N. bassleri make an appearance in this interval. In the Cedro Peak section

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FI 2b is occurs at the top of the Sandia Formation and at the base of the Gray Mesa

Formation. Idiognathodus gibbus I. sp. Q, I. sp. Q2, I. sp. Z, N. bassleri, and N. pre- colombiensis were recovered from the top of the Sandia Formation (unit 3). Late forms of

N. bassleri, I. sp. Q, I. sp. Q2, I. gibbus, and I. sp. Z occur at the base of the Gray Mesa

Formation (unit 5).

At the Presilla A section, FI 2 occurs in the middle Sandia Formation. FI 2 is represented by the occurrence of Idiognathodus sp. Q (units 27 and 29) with

Declinognathodus marginodosus (units 27 and 29), and Idiognathoides sp. (unit 27).

Because I. sp. Q occurs with N. pre-colombiensis, it is interpreted that D. marginodosus, and Idiognathoides occur in FI 2. In Presilla B section, the base of the Gray Mesa

Formation (unit 16) yielded only I. sp. Q, which is indicative of FI 2.

Faunal Interval 3

Faunal Interval 3 is one of the more widespread intervals and can be split into two parts, a lower 3a and an upper 3b (Figure 19). Interval 3a is defined by the first occurrence of Neognathodus colombiensis. Other species that have their first appearance in this interval are Idiognathodus sp. H, and I. sp. G. Idiognathodus gibbus and I. sp. Q2 persist into this interval from FI 2. At the Sepultura Canyon section, FI 3a occurs in the middle Sandia Formation (unit 46) based on the presence of N. colombiensis, I. sp. H, I. sp. G, and I. sp. Q2. Interval 3a is also present in the lower Gray Mesa Formation at the

Presilla section B based on the occurrence of I. sp. H (unit 22), and N. colombiensis (unit

28).

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Interval 3b is defined by the first occurrence of Neognathodus bothrops.

Neognathodus colombiensis, I. sp. Q2, I. sp. G, and I. sp. H range up from FI 3a.

Neognathodus aff. N. caudatus, and I. obliquus first occur in this interval. In the Tejano

Highway section, interval 3b occurs in the middle to upper Sandia Formation of the first fault block, where N. bothrops (unit 19), I. sp. H (units 19 and 36), I. sp. G (unit 36), I. sp. Q2 (unit 19) are present. Interval 3b in this section ranges up into the Gray Mesa

Formation based on the presence of N. colombiensis (unit 57) and I. sp. H (unit 68). In the Cedro Peak section, FI 3b may be present in the lower Gray Mesa Formation (unit 13) where N. caudatus, I. sp. H, and I. obliquus occur. At the Presilla B section, Faunal

Interval 3b appears in the lower Gray Mesa where specimens of N. bothrops, and I. sp. H

(units 34 and 41) were recovered.

Faunal Interval 4

Fauna Interval 4 is defined by the first occurrence of Neognathodus asymmetricus

(Figure 19). In FI 4, N. asymmetricus occurs with Idiognathodus sp. H, I. obliquus, N. colombiensis, and N. aff. N. caudatus. Faunal Interval 4 occurs in the Gray Mesa

Formation at the Tejano Highway section at the top of the first fault block (unit 42) and in the middle of the second fault block (unit 61). Neognathodus asymmetricus appears at the Cedro Peak Z section in the lower Gray Mesa Formation (unit 15). FI 4 is present in the Sandia Formation at the Sepultura Canyon section (unit 81), based on the presence of

N. asymmetricus, and I. sp. H. In the Presilla B section, though, N. asymmetricus appears well above the base of the Gray Mesa Formation (unit 86).

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Faunal Interval 5

Faunal Interval 5 is defined by the appearance of Idiognathodus species with a few coarse transverse ridges, such as Idiognathodus robustus (Figure 19). The species

Neognathodus colombiensis II also appears within FI 5 in association with a series of species of the I. iowaensis/I. rectus group, which have relatively straight platforms and few widely spaced transverse ridges. This distinctive Idiognathodus fauna appears in the

Tejano Highway section near the top of the third fault block of the Gray Mesa Formation

(unit 104). Faunal Interval 5 is present at the Sepultura Canyon section near the middle of the Sandia Formation (unit 89) and in the middle Sandia (unit 85) and basal Gray Mesa

(unit 93) at the Type Sandia section.

Faunal Interval 6

The youngest of the intervals, Faunal Interval 6, is identified by the first occurrence of Neognathodus intrala, which may occur with N colombiensis II, and N. aff.

N. asymmetricus, a late form (Figure 19). Idiognathodus species that occur in this faunal interval are the same as those occurring in FI 5. In the Tejano Canyon section, FI 6 appears in the fourth fault block of the Gray Mesa Formation (unit 152) with N. intrala,

N. aff. N. asymmetricus, N. colombiensis II, and I. robustus, and ranges to the top of the

Whiskey Canyon Member. At the Sepultura Canyon section, N. intrala and I. robustus occur at the base of the Gray Mesa (unit 101). Faunal Interval 6 ranges from the upper part of the Whiskey Canyon Member (unit 122) into the base of the overlying Garcia

Member (unit 132) in the Presilla B section.

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Ages of the Faunal Intervals

Faunal Intervals 1 and 2 fit within the Neognathodus atokaensis Zone (Figure 20) of the Midcontinent zonation (Barrick et al., 2013). At the Type Sandia section these intervals occur with the fusulinid Eostaffella pinguis, which gives a broad late Morrowan to early Atokan age. Saelens (2014, p. 26) reported that her similar Faunal Interval 2 occurred with Profusulinella at the type Derry section (Clopine, 1992) and ranged into the Fusulinella Zone at the Whiskey Canyon section, which suggest a middle Atokan age.

The lower boundary of Faunal Interval 3a, defined by the first occurrence of

Neognathodus colombiensis, corresponds to the base of the Midcontinent N. colombiensis

Zone (Barrick et al., 2013; Figure 20). Species occurring in FI 3a are those commonly found in late Atokan beds, especially forms of I. gibbus, which is known only from late

Atokan strata in Iowa (Lambert, 1992) and New Mexico, where it occurs in the

Fusulinella Zone (Saelens, 2014). The appearance of N. bothrops, which marks the base of FI 3b, is associated with a diversification of Idiognathodus species (e.g., the I. sp. H group) and is followed by the appearances of I. obliquus and N. sp. aff. caudatus. The latter two species occur only in certain early Desmoinesian strata (Lambert, 1992; Treat,

2014), but the first occurrence of N. bothrops and the I. sp. H group lie near the first occurrence of Fusulina insolita, which is interpreted to be the working base of the

Desmoinesian (Wahlman, 2013). However, too little data exists to confirm the exact order of occurrence of these taxa. Here, we use the base of FI 3b to approximate the base of the Desmoinesian.

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Faunal Interval 4 is defined by the first occurrence of Neognathodus asymmetricus, which also defines the base of the Midcontinent N. asymmetricus Zone

(Barrick, et al., 2013; Figure 20). Most species from FI 3b range up into FI 4.

The base of Faunal Interval 5 is recognized by the appearance of Idiognathodus robustus and members of the I. rectus/I. iowaensis group. These are the same criteria used to identify the base of the Midcontinent I. rectus/I. iowaensis Zone (Barrick, 2013;

Figure 19).

Faunal Interval 6 is defined by the first occurrence of Neognathodus intrala and many species from FI 5 range into FI 6. Previously, N. intrala has been reported from only the late early Desmoinesian (late Cherokee) Verdigris cyclothem (Stamm and

Wardlaw, 2003), but it is likely that the species appeared somewhat earlier. Faunal

Interval 6 is equivalent to the upper part of the N. asymmetricus Zone in the Midcontinent

(Barrick, 2013; Figure 20).

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Figure 19. Faunal intervals and ranges of selected conodont species in the Sandia and Gray Mesa Formation.

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Figure 20. Comparison of Faunal Intervals from the Sandia and lower Gray Mesa formations with conodont zones of Barrick et al. (2013) and faunal intervals of Saelens (2014) and Treat (2014).

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Ages of the Sandia Formation and Gray Mesa Formation

The oldest conodont faunas recovered from the Sandia Formation are middle

Atokan in age (Faunal Interval 1) from the base of the formation at the Type Sandia section and the middle of the formation at Presilla A. The great thickness of strata below the conodont-bearing level at Presilla A (A 27, 45 m above the base) allow for the possibility the underlying strata may be Morrowan to early Atokan in age.

The boundary between the Sandia and Gray Mesa Formations is generally placed where cliff-forming cherty limestone of the Gray Mesa replaces the less well-exposed siliciclastics of the Sandia. Although this may be a good lithostratigraphic boundary for mapping purposes, the transition from "Sandia" to Gray Mesa" generally involves some interbedding of siliciclastic and carbonate lithofacies and the transition to a carbonate- dominated succession appears to have occurred at different times in the different sections

( Figure 11).

To the north of the study area, the Sandia-Porvenir transition covers just a few meters of interbedded siliciclastics and carbonates before carbonates dominate the succession (Baltz and Meyers, 1999; Treat, 2014). Here the transitional beds and the base of the Porvenir are latest Atokan to earliest Desmoinesian in age (Treat, 2014). To the south of the study area, where the Red House Formation underlies the Gray Mesa

Formation, the transitional interval is also thin (Lucas et al., 2012) and the basal Gray

Mesa is latest Atokan to early Desmoinesian in age (Saelens, 2014). The most southern section of the Sandia overlain by Gray Mesa occurs at the Presilla B section of this study.

As in the Red House/Gray Mesa sections to the south, the transitional interval is

Texas Tech University, Paul Alex Moore, May 2017 relatively thin (Lucas et al., 2009). The lower carbonates of Gray Mesa Formation start in the late Atokan Faunal Interval 2 (unit 16) and Faunal Interval 3a (units 22 and 28) and the early Desmoinesian Faunal Interval 3b appears in unit 34, m above the base of the

Gray Mesa.

At Sepultura Canyon in the Los Pinos Mountain to the north, in contrast, latest

Atokan conodonts of Faunal Interval 3a (unit 45) and early Desmoinesian conodonts of

Faunal Interval 3b (unit 51) appear in the middle of the thick section of the Sandia

Formation, well below the highest major siliciclastic interval. However, to the north, in the Manzanita Mountains, at the Cedro Peak section the carbonate beds assigned to the uppermost Sandia (unit 3) and lowermost Gray Mesa (unit 5) both contain a late Atokan,

Faunal Interval 2b fauna. Faunal Interval 3b appears slightly higher, in unit 13.

The siliciclastic-dominated lower portion of section1 (fault block 1) along Tejano

Highway was assigned to the Sandia Formation by Smith (1999) and section 2 (fault block 2) to the gray limestone member of the Madera (=Gray Mesa), although both contain thick sandstone beds. Lucas and Allen (2016, personal communication) suggested that the fault blocks of the Tejano Highway section were repeated segments of strata within the Sandia, and that the base of the Gray Mesa began only in section 4. The early

Desmoinesian Faunal Interval 3b appears in the middle of section 1 (units 19 and 36), well below a series of thick sandstone beds, and the successive fault blocks yielded successively younger early Desmoinesian faunas (FI 2-FI5). No omission or repetition of strata between successive fault blocks could be ascertained from the conodont faunas.

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At the nearby Type Sandia section, although the basal beds are middle Atokan

(FI 1), conodont faunas higher than unit 28 are undiagnostic until unit 85. Here, the conodont fauna is tentatively assigned to the much younger late early Desmoinesian

Faunal Interval 5. This age assignment differs strongly from the report by Krainer et al.

(2004) that Atokan fusulinids occur in the overlying basal bed (unit 93) of the Gray Mesa

Formation.

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Chapter 7 Systematic Paleontology

Complete revision of the species described here is not feasible because of the incomplete nature of the previous literature. Numerous Atokan and early Desmoinesian conodonts have been illustrated from North America in the older literature, but lack accompanying descriptions and discussions. The original collections will need to be reviewed before adequate comparisons can be made. Faunas of comparable ages from

China, Eurasia, and South America are also poorly documented and will not be considered in this thesis. Only species of Idiognathodus and Neognathodus are included, for they comprise the greatest number of elements and the most significant forms for biostratigraphy.

Conodont element descriptions use the terminology of Purnell et al. (2000) and

Rosscoe and Barrick (2009). Photomicrographs are oriented in the conventional manner, with dorsal end down, for easy comparison with older publications. Specimens are currently reposited in the collections in the Department of Geosciences, Texas Tech

University, but eventually will be transferred to the New Mexico Museum of Natural

History in Albuquerque.

Phylum CONODONTA Pander, 1856

Class CONODONTI Branson, 1938

Order OZARKODINIDA Dzik, 1976

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Family IDIOGNATHODONTIDAE Harris and Hollingsworth, 1933

Genus IDIOGNATHODUS Gunnell, 1931

Diagnosis: P1 element is carminiscaphate, and the upper platform surface is relatively flat with transverse ridges in the dorsal region. Nodes, or lobes, commonly occur along the caudal and rostral margins of the platform.

Remarks: Idiognathodus, Streptognathodus Stauffer and Plummer, 1932, and Swadelina

Lambert, Heckel and Barrick, 2003, are closely related genera commonly occurring in

Pennsylvanian strata. Idiognathodus typically has a flat upper surface, whereas

Streptognathodus and Swadelina have a distinct groove or trough on the upper surface.

Swadelina occurs only in Lower and Middle Pennsylvanian strata and does not have transitional forms to Idiognathodus. Streptognathodus was derived from Idiognathodus in the Late Pennsylvanian (Missourian), where transitional forms do occur (Rosscoe, 2008).

The taxonomy and nomenclature of Atokan and Desmoinesian species of

Idiognathodus have generally been ignored by North American workers, who have either not identified the species, left taxa in open nomenclature, or have used Morrowan,

Atokan, and Desmoinesian names in a broad, uncritical fashion (e.g., recently, May et al.,

2009; Brown et al., 2013). Studies of faunas from Russia and Ukraine (e.g., Nemirovska,

1999; Alekseev and Goreva, 2001) give some indication of the variety of Idiognathodus species present, but do not resolve most of the taxonomic issues. In contrast, Lambert

(1992) and Stamm and Wardlaw (2003) represent significant attempts to interpret Middle

Pennsylvanian Idiognathodus species, but only from limited stratigraphic levels.

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More recent work by Saelens (2014) and Treat (2014) on Atokan and early

Desmoinesian faunas from New Mexico provide a better starting point for consideration of species in this study. Some Atokan species are difficult to place into lineages. Middle

Atokan species were assigned to either Idiognathodus sinuous Grave and Ellison, 1941, or one of two morphotypes of I. incurvus Dunn, 1966. One late Atokan group includes forms with short platforms that show affinity with Idiognathodus gibbus Lambert, 1992.

Another distinctive latest Atokan to early Desmoinesian form has a broad platform with large lobes, I. sp. G. Saelens (2014). Treat (2014) recognized a succession of species with distinctly curved elements that may comprise a lineage crossing from the latest Atokan into the early Desmoinesian. The oldest species I. sp. I, is narrow and lacks a rostral lobes. In I. sp. HI, the rostral lobe appears, the caudal lobe increases somewhat in size and the platform broadens. In the youngest species, I. sp. HA, the platform widens more and both lobes are well developed.

Several new forms of Idiognathodus are recognized here that are difficult to compare to previously described taxa. These are presented in open nomenclature.

Because of the variety of Idiognathodus morphotypes recovered and the incomplete stratigraphic recovery, it is difficult to reconstruct lineages. Species are discussed in the approximate stratigraphic order in which they occur.

Idiognathodus sp. Q (Figure 20: 2, 7, 8, 10-16; Figure 21: 17, 20)

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Diagnosis: P1 element is elongate, wider dorsally, gently curved with the pointed dorsal tip more sharply incurved. The high adcarinal ridge forms most of the rostral margin, continuing dorsally as a series of high nodes.

Description: The P1 element is elongate and curves gently except for the more sharply incurved pointed dorsal tip. The platform is narrow ventrally, widens dorsal of the adcarinal ridges, and then narrows dorsally. The rostral margin is high and is composed of the adcarinal ridge ventrally and a series of high nodes dorsally. The caudal side bears a small lobe of a few nodes. A few nodes may lie outside of the rostral margin.

Transverse ridges (10-12) are slightly deflected or perpendicular to the platform.

Remarks: Idiognathodus species Q is similar to forms illustrated as I. incurvus Dunn,

1966. The incurved dorsal tip is like that reported for I. incurvus, but I. sp. Q can be distinguished from I. incurvus by the high rostral adcarinal ridge that forms the platform margin. Idiognathodus incurvus was also was described as having both caudal and rostral lobes.

Idiognathodus sp. Q2 (Figure 20: 1, 3-6, 9; Figure 21: 16, 21-23)

Diagnosis: P1 element is elongate, curves gently except for the more sharply incurved pointed dorsal tip. The high adcarinal ridge forms most of the rostral margin, continuing dorsally as a series of high nodes. The caudal lobe is well developed and a series of nodes occur outside of the rostral margin.

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Description: The P1 element is slightly curved and elongate. The platform is narrow ventrally, widens dorsally of the adcarinal ridges, and then narrows more dorsally. It bears a well-developed, caudal lobe that is separated from the rest of the platform. The rostral margin is formed by the adcarinal ridge ventrally and high nodes dorsally. The caudal adcarinal groove is longer than the rostral groove and flares out ventrally. The platform bears a series of ridges (10-11), which are slightly oblique or perpendicular to the platform and may be slightly indented.

Remarks: Idiognathodus sp. Q2 resembles I. sp. Q in the features of the rostral margin and incurved dorsal tip. However, I. sp. Q2 has a wider platform, and bears better developed lobes. Idiognathodus sp. Q2 is more like I. incurvus, but the former species differs in its high rostral margin and its poor rostral lobe.

Idiognathodus gibbus Lambert, 1992 (Figure 21: 2-5, 8-11, 14, 15)

Diagnosis: P1 platform is short, robust and subrounded with a blunt dorsal end. Caudal adcarinal ridge is long and extends along platform margin. Rostral adcarinal ridge ends at the distinct widening of the dorsal platform. There is a small caudal lobe and the rostral side may bear a single node.

Description: The P1 element has a stubby, short, wide platform with a long free blade.

Two long narrow adcarinal ridges flank the carina. A poorly developed caudal lobe of a few nodes is present, but the rostral margin generally bears no more than a single node.

The platform widens dorsally of the adcarinal ridges, strongly so on the rostral side. The

Texas Tech University, Paul Alex Moore, May 2017 platform has a series of slightly oblique ridges (9-11) that may be deflected ventrally at a slight medial depression. The dorsal tip is generally wide and rounded .

Remarks: Lambert (1992) described similar forms as Idiognathodus gibbus from upper

Atokan beds in Iowa. Saelens (2014) recognized two morphotypes that she assigned to I. gibbus. Our material resemble her I. gibbus I, which has a larger platform and a round caudal lobe.

Idiognathodus sp. Z (Figure 21:12, 13, 18, 19)

Diagnosis: P1 element has a broad, triangular platform with robust lobes. Caudal lobe is large with concentric rows of nodes. Rostral lobe is expanded and nodose. A series of fine transverse ridges ornament the platform. Flaring caudal adcarinal ridge extends much further ventrally than rostral adcarinal ridge.

Description: The P1 element has a broadly triangular shape because of the well- developed lobes and tapers to a pointed dorsal tip. The caudal lobe is large and composed of up to three concentric rows of nodes. The rostral lobe is smaller, but still expanded and heavily nodose. The rostral adcarinal ridge is short, but the caudal ridge extends much further ventrally and flares outward. The platform has numerous (8-11) fine, transverse ridges, which become more deflected toward the tip of the platform

Remarks: Idiognathodus sp. Z has much better developed, more nodose lobes than other

Middle Pennsylvanian species. It resembles I. obliquus in the degree of node development, but in I. obliquus the rostral lobe stretches further dorsally and the dorsal

Texas Tech University, Paul Alex Moore, May 2017 platform is more strongly incurved with strongly oblique transverse ridges. Some specimens of Saelens (2014, fig. 21.21-22) that were assigned to her I. sp. H, appear to be examples of I. sp. Z.

Idiognathodus sp. G Saelens, 2014 (Figure 21: 1, 6, 7)

Diagnosis: P1 elements have a broad platform with well-developed lobes on the rostral and caudal margins. A slight depression occurs on the dorsal platform.

Description: The platform is broad, slightly curved, and has a semi-rounded tip. The platform has numerous (8-10) fine, transverse ridges, which become more deflected toward the tip of the platform. The platform surface tends to be slightly depressed. The left element of this species has more strongly developed traits compared to the right element.

Remarks: Saelens (2014) and Treat (2014) described a similar species from the Caballos

Mountains and Sangre de Cristo Mountains, respectively. Idiognathodus sp. G comprises lobed specimens that do not conveniently fit into the other species.

Idiognathodus sp. H Saelens, 2014 (Figure 22:1, 12, 12, 14-27)

Diagnosis: P1 element is triangular, wide, strongly curved, and has a large caudal lobe and a restricted rostral lobe. Transverse ridges align with the curvature of the platform.

The dorsal tip is generally pointed.

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Description: The P1 platform is triangular with a wide ventral region, narrows dorsally, and is gently curved. The adcarinal ridges reach to the middle of the lobes. The caudal lobe is moderately large and bears several nodes and the restricted rostral lobe bears just a few nodes. The transverse ridges (8-10) are integrated with the rest of the platform, and the ridges bend in alignment with the curvature of the platform. The dorsal tip is generally pointed.

Remarks: Treat (2014) recognized two forms, HI, which has a small rostral lobe, and HA, which has a larger rostral and caudal lobes. Here, we do not distinguish between the two morphotypes.

Idiognathodus amplificus Lambert, 1992? (Figure 22: 7, 10, 13)

Diagnosis: P1 element is high, long, slender and nearly straight. Caudal and rostral lobes are weakly developed.

Remarks: A small number of P1 elements from Faunal Interval 3b possess high, straight and slender platforms, unlike the common morphotype, I. Species H, which is shorter and broader, more curved and has better developed lobes. Although reported to be characteristic of early Desmoinesian strata in Midcontinent North America, these slender platforms are rare in the New Mexico faunas.

Idiognathodus obliquus Kozitskaya and Kossenko, 1978 (Figure 22: 3-6, 9, 11)

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Diagnosis: P1 element is broad and strongly curved toward the caudal margin such that the numerous fine transverse ridges are obliquely oriented. The caudal lobe is large and the rostral lobe is expanded to elongated.

Description: The P1 element has a subtriangular, broad platform, which curves strongly and downward. The caudal lobe is large and nodose. The nodose rostral lobe is expanded to elongated in length. A series of fine transverse ridges (12-14) occupy the platform, which begins roughly in the middle of the lobes. These ridges align with the curvature of the platform, which makes then run oblique to the carina. The dorsal tip is bluntly pointed to rounded.

Remarks: Idiognathodus obliquus resembles I. sp. HA of Treat (2014). Both species have a broad, curved platform with prominent lobes, but I. obliquus has finer, more numerous transverse ridges, an expanded to elongated rostral lobe, and a more downward curved dorsal end.

Idiognathodus rectus/ I. iowaensis Youngquist and Downs, 1949 (Figure 23: 1-4,7-10)

Remarks: Barrick et al. (2013) recognized a distinctive association of Idiognathodus morphotypes that characterize the upper part of the Cherokee Group in the Midcontinent region that they used to define the I. rectus/I. iowaensis Zone. In contrast to the strongly curved platforms and finer transverse ridges seen in older Desmoinesian taxa, the morphotypes in this younger fauna possess relatively straight platforms, more widely spaced transverse ridges, and small lobes. Pending revision of the type material from

Iowa, they suggested that three older names could be used as follows: Idiognathodus

Texas Tech University, Paul Alex Moore, May 2017 rectus Youngquist and Downs 1949 has a straightly, relatively symmetrical platform with minimal lobes; I. iowaensis Youngquist and Heezen 1948 has a more curved platform with a more prominent caudal lobe; and I. attenuatus Youngquist and Heezen 1948 has a less curved slender platform with a narrow dorsal end and a more prominent caudal lobe.

Because of our small number of specimens, we have not separated the species.

Idiognathodus robustus Kozitskaya and Kossenko? (Figure 23:11-23)

Diagnosis: The P1 element has a triangular platform, which is wider at the ventral margin and narrows dorsally as it gently curves. Well developed caudal and rostral lobes form the ventral margins. A few widely spaced transverse ridges ornament the platform.

Description: The platform has a slightly curved triangular shape and is wider in the ventral platform because of the caudal and rostral lobes. The caudal lobe is more prominent than the rostral lobe. Adcarinal grooves are short. Coarse, straight, widely spaced, transverse ridges ornament the platform that tapers to a sharp dorsal tip.

Remarks: Idiognathodus robustus? is similar to species of the I. rectus/I. iowaensis group, but differs in its strongly triangular shape formed by the lobes on the ventral margins of the platform. We are uncertain whether our material is nonspecific with the original material of I. robustus, which was described from the Donets Basin.

Genus NEOGNATHODUS Dunn, 1970

Type Species: Polygnathus bassleri Harris and Hollingsworth, 1933

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Diagnosis: Carminiscaphate P1 elements are dominated by a medial carina that extends most or all the length of the element. Platform margins vary from the entire margins with adcarinal grooves, to reduction of one or both margins to parapets and nodes, or complete loss on one side.

Remarks: Neognathodus is a widespread Pennsylvanian genus with abundant morphotypes that range from the Morrowan through the Desmoinesian. Morrowan and early Atokan species are dominated by morphotypes with entire platform margins, however, other morphotypes with incomplete margins are present. Desmoinesian strata have a variety of morphotypes in which the margins are reduced to parapets and nodes, or eventually lost, appear and then dominate the faunas. Merrill (1999) proposed that the evolution of Neognathodus through the Desmoinesian can be best described as a "gradual morphological shift from one chronospecies to the next through the Desmoinesian"

(Brown and Rexroad, 2009; Brown et al. 2013). However, this view has been strongly criticized by other workers (e.g., Stamm and Wardlaw, 2003).

In the Sandia and Grey Mesa formations, faunas are dominated by three distinct

Neognathodus lineages/groups. One lineage is characterized by a high carina, and biconvex platform and includes N. bassleri, N. sp. B2, N. bothrops, and N. asymmetricus.

The other two lineages have an asymmetrical triangular platform where one margin is exceedingly higher and more prominent than the other and includes N. atokaensis, N. pre- colombiensis, N. colombiensis, N. colombiensis II, N. uralicus, and N. caudatus.

Neognathodus bassleri- asymmetricus Lineage

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The P1 elements of species of the bassleri-asymmetricus lineage are distinguished by a biconvex platform, straight carina, and two complete adcarinal margins. The ancestral species in this lineage is likely the Morrowan species N. symmetricus (Lane,

1967), which has not been identified in the study sections. Neognathodus bassleri bassleri (Harris and Hollingsworth, 1933) is generally considered to have developed from N. symmetricus during the Morrowan and the species ranges in to the Atokan .

Neognathodus. bassleri bassleri is distinguished by a P1 element with a biconvex, more or less symmetrical platform, which has a thick carina surrounded by adcarinal ridges composing the margins. The carina terminates well before the dorsal tip of the elements, leaving a depression between the end of the carina, and the dorsal tip.

Saelens (2014) described middle to late Atokan morphotypes of N. bassleri bassleri from the Red House Formation in the Caballo and Mud Springs Mountains of

New Mexico. Neognathodus species B1 of Saelens (2014) has a biconvex outline similar to that of typical N. bassleri bassleri, but the platform is more evenly ovate, the margins are slightly lower and the carina is relatively higher. A thin ridge extends dorsally from the end of the carina and partially merges with the rostral margin of the element.

Neognathodus species B2 has lower platform margins, and the carina is level with the margins. The carina extends nearly to the dorsal tip of the platform, but thins dorsally.

These morphotypes were interpreted to be transitional forms from N. bassleri bassleri to

N. bothrops Merrill, 1972 (Saelens, 2014).

Neognathodus bothrops, in contrast to the N. bassleri morphotypes, has a carina that extends to the dorsal end of the platform and forms the dorsal tip of the platform. In slightly younger strata, the dorsal third of the carina becomes deflected to the outer

Texas Tech University, Paul Alex Moore, May 2017 margin, and eventually fuses with it (see Alekseev and Goreva, 2013). Merrill (1972) used the name N. medadultimus to designate the older forms with an asymmetrical carina, but the older name N. asymmetricus (Stibane, 1967) is more appropriate. In younger forms, the carina fuses with the outer margin such that the carina and margin become a single unit

Neognathodus bassleri bassleri Harris and Hollingsworth, 1933 (Figure 25:16, 18-20,

23)

Diagnosis: P1 element has a slightly asymmetrical biconvex platform with a low carina.

The margin outlines are raised above the carina ventrally and merge at the dorsal tip. The dorsal margins are constricted slightly. The carina does not reach the dorsal tip, leaving a depression between the carina and tip of the platform.

Description: The P1 element is biconvex and has an ovate platform. The ventral platform is slightly wider than the dorsal platform, and the margins are high, more or less symmetrical, and wrap around the platform to form a dorsal tip. The margins are slightly constricted in the dorsal half of the platform. The carina is lower than the margins and ends before reaching the dorsal tip, leaving a depression or trough between the end of the carina and the dorsal tip. The dorsal tip generally has a semi-pointed curve, however, few specimens have been recovered with a rounded dorsal tip.

Remarks: We include all biconvex morphotypes in which the carina does not extend completely to the dorsal end in Neognathodus bassleri bassleri. Generally the carina is lower than the margins of the platform. This includes the two morphotypes of Saelens

Texas Tech University, Paul Alex Moore, May 2017

(2014) as discussed above. Treat (2014) described a series of late Atokan to early

Desmoinesian Neognathodus morphotypes that he excluded from N. bassleri bassleri even though the carina did not extend to the dorsal tip of the platform. He noted that the typical Morrowan examples of N. bassleri bassleri possessed ventral margins that were distinctly flared and were higher than the low carina. In his specimens, though, the margins of the elements were more evenly biconvex and the carina was equal in height with the margins.

Neognathodus bothrops Merrill, 1972 (Figure 25: 10, 11, 17)

Diagnosis: The P1 element has a biconvex, nearly symmetrical ovate platform and a medial carina that forms a dorsal tip of the platform. The platform margins are slightly lower than the carina and both sides merge with the carina at the dorsal tip.

Description: The P1 element has a slightly asymmetrical biconvex platform. The carina is elevated above the margin outlines, and extends dorsally slightly past the platform margins to form the dorsal tip of the element. The carina is straight, and thickest at the ventral platform and thins proximal to the dorsal tip. The caudal margin is slightly more prominent, wider than, and elevated slightly above the rostral margin.

Remarks: Neognathodus bothrops is distinguished from the morphotypes of N. bassleri bassleri and similar forms because its carina forms the dorsal termination of the platform and is similar in height to the platform margins. The straight medial carina of N. bothrops distinguishes it from the younger species N. asymmetricus, in which the carina is deflected toward the outer margin and partially fuses with it.

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Neognathodus asymmetricus (Stibane, 1967) (Figure 25: 7, 12-15)

Diagnosis: The P1 element has a biconvex platform with margins that extend to the dorsal tip. The carina is straight on the ventral platform but near mid-length the carina deflects toward the rostral margin and lies near it dorsally.

Description: The P1 element is biconvex with asymmetrical margins. The caudal margin outline is lower than the carina for the entirety of the platform. The carina is straight in the ventral region of the platform, but deviates toward the rostral margin in the middle region. Dorsally, the carina runs adjacent to the rostral margin all the way to the dorsal tip. One morphotype of N. asymmetricus was found only in the Tejano Highway section.

The P1 element has a biconvex platform, wide set margins and is strongly curved in a shape that resembles an "S". The caudal margin outline is prominent, higher than the carina and forms a ridge that is well defined from the rest of the margin. This outline decreases in thickness more proximal to the dorsal tip. The rostral margin is relatively narrow in respect to the caudal margin. The carina mimics the S-shape of the platform outlines, favors the rostral margin, and does not reach the dorsal tip of the platform.

Remarks: Stibane (1967) described N. asymmetricus as having the carina merge or run into the margin where the merged carina/margin may or may not turn into a collection of nodes. We interpret N. medadultimus Merrill, 1972, N. medexultimus Merril, 1972, and

N. asymmetricus to be the same species. In N. medadultimus the carina deflects toward the rostral margin where it runs along the margin and partially fusing with it to the dorsal tip. In N. medexultimus, the carina appears to become the dorsal part of the rostral side of

Texas Tech University, Paul Alex Moore, May 2017 the platform, and the rostral margin is restricted to the ventral platform. Neognathodus bothrops is similar to N. asymmetricus, but the carina is medial and not deflected.

Intermediate specimens with a clear, though slight, deflection of the carina have been assigned to N. asymmetricus.

Neognathodus asymmetricus, late form (Figure 25: 5, 6, 8)

Diagnosis: P1 element has an asymmetrical outline with a complete caudal margin. On the rostral side, the dorsal carina is strongly deflected rostrally where is forms the rostral side of the dorsal platform. The remaining rostral margin forms a short parapet along the ventral platform that is separated from the deflected carina by a small gap.

Description: The P1 element has a narrow, asymmetrical platform. The caudal margin is relatively wide compared to the rostral margin, and is complete to the dorsal end of the platform. However, is becomes more nodose dorsally. The ventral rostral margin is short, with a high parapet that is separated from the rest of the carina/margin by a gap. At midlength, the carina deflects strongly rostrally to form the rostral margin of the platform. It does not appear to connect with the caudal margin in the dorsal tip.

Remarks: Neognathodus asymmetricus, late form, is closely related to N. asymmetricus, but differs by the degree of deflection of the carina and that the carina replaces the original rostral margin of the element. When Merrill (1972) erected N. medadultimus and

N. medexultimus, he distinguished the latter species by the greater fusion of the carina with the dorsal rostral margin. However, on the holotype of N. medexultimus, the carina can still be distinguished from the rostral margin and the ventral rostral parapet. We

Texas Tech University, Paul Alex Moore, May 2017 interpret both of Merrill’s species to be two examples of N. asymmetricus. Our species appears to represent a younger species, one in which the carina has completely replaced the dorsal rostral margin and the ventral rostral margin forms only a parapet. Merrill

(1972) was clear that in his species it was the deflection of the carina that characterized his species. Unfortunately, most workers have subsequently tried to fit all Desmoinesian

P1 elements with a restricted rostral margin into one of his species, including forms in which the carina is straight and the rostral margin has retreated independently of the carina. These forms with a straight carina we provisionally attribute to late forms of N. colombienis (Stibane, 1967; see below).

Neognathodus atokaensis-N. colombiensis Lineage

The Neognathodus atokaensis- N. colombiensis lineage is distinguished by triangular-shaped platforms, long, well defined carinas, and variable development of the platform margins. Alekseev and Goreva (2013) stated that N. atokaensis Grayson, 1984 is the ancestor of N. colombiensis Stibane, 1967). Neognathodus atokaensis has a short rostral margin that terminates well before reaching the dorsal tip, and a long prominent carina. In our samples, N. “pre-colombiensis” is most likely derived from N. atokaensis due to their similarity in platform shape. The rostral margin of N. ―pre-colombiensis,‖ when compared to N. atokaensis, extends to near the dorsal tip. The dorsal margin outlines are composed of nodes and gaps, which tightly constrain the dorsal tip.

Neognathodus " pre-colombiensis" has a bit wider platform that slightly flares out in the ventral caudal margin to produce a more triangular outline for the entire platform.

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Neognathodus “pre-colombiensis” appears to be a transitional morphotype between N. atokaensis and N. colombiensis. Neognathodus colombiensis is defined by a triangular, arrow-shaped platform, with a medial carina that exceeds the platform. The ventral edges of the margins often possess a larger denticle that forms the ventral edges of the triangle.

When compared to N. "pre-colombiensis," N. colombiensis has a better-defined rostral margin, and lacks the gaps and nodes seen in N. "pre-colombiensis." The final form of this lineage, N. colombiensis II, is distinguished by having a triangular platform with a wide, slightly rounded caudal margin and a narrow rostral margin. The rostral margin is often terminated just before the dorsal tip and may breakup into nodes. Neognathodus colombiensis II appears to be the ancestor of N. roundyi (Gunnell, 1931), in which the dorsal portion of the rostral margin is completely lost.

Many authors have confused forms of the Neognathodus asymmetricus lineage with those of the N. colombiensis lineage. In the N. asymmetricus lineage, the dorsal carina is more weakly developed and always shows a strong deflection to merge with rostral platform margin. In contrast, in the N. colombiensis lineage, the high straight carina dominates the element and the rostral margin retreats ventrally from the dorsal tip with little fusion to the carina. This distinction is important because the species of N. asymmetricus lineage modifies the rostral margin earlier in the Desmoinesian (N. caudatus Zone) than do species of the N. colombiensis lineage (I. rectus/iowaensis Zone).

Calculation of the Neognathodus Index (e.g., Brown and Rexroad, 2009; Brown et al.

2013) fails to take these asynchronous changes into account.

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Neognathodus atokaensis Grayson, 1984 (Figure 24: 21-23, 29-32)

Diagnosis: The P1 element has a long carina, and a slightly flaring caudal margin that extends to dorsal end of the carina and that is about the same height as the carina. Rostral margin is lower than carina and ends before the dorsal end.

Description: The P1 element is wide with low margins. The rostral margin extends dorsally only about ¾ of the length of the platform, lies lower than the carina, and does not merge with the carina. The caudal margin flares out slightly, is slightly elevated above the carina ventrally, and becomes level with the carina medially, and is lower than the carina where it merges with it at the dorsal tip. The rostral margin extends further ventrally than the caudal margin, more so in the dextral element.

Remarks: Neognathodus atokaensis was described by Grayson (1984), where a variety of morphotypes were illustrated, including forms later called N. uralicus. Both species have a complete caudal margin, but the rostral margin ends before the dorsal tip. In N. atokaensis, the dorsal end of the carina is smooth to evenly denticulated, whereas in N. uralicus, the dorsal carina and the adjacent narrow caudal platform margin are broken up into a series of coarse conical nodes. Grayson's (1984) holotype best fits the specimens observed in the Sandia Formation. Alekseev and Goreva (2013) claimed that N. atokaensis is a precursor for N. bothrops and N. medadultimus/asymmetricus, due to the elliptical outline of the platform, tapering to the anterior end, and with both parapets extending to the posterior end of the carina, but here we present a different interpretation.

Neognathodus “pre-colombiensis” (Figure 24:12, 19-21)

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Diagnosis: P1 element has an asymmetrical triangular platform .The rostral margin is narrow, and composed of nodes with gaps dorsally. The caudal margin is wider and nearly complete, but may be nodose near where it connects with the carina. The carina is long, straight and extends to tip of the platform.

Description: The platform is triangular with a narrow rostral margin, and a wider caudal margin. The rostral margin is most prominent along the ventral platform and it becomes segmented in the middle region, and ultimately composed of nodes and gaps in the dorsal platform. The caudal margin is wider in comparison to the rostral margin and has weak ridges. The margin retains a complete outline, except near the dorsal end, where small nodes begin to replace the margin near where it connects to the carina. The rostral margin extends further ventrally than the caudal margin, more so in the dextral element. The carina is straight, and thick from the ventral to the middle platform. Large nodes begin to replace the carina in the dorsal region, where is connects with the outer margin.

Remarks: Neognathodus “pre-colombiensis” is interpreted to be a species transitional between N. atokaensis and N. colombiensis (Stibane 1967). When compared to N. atokaensis, N. “pre-colombiensis” shares a similar triangular-shaped platform, but in the latter species, the rostral margin, although composed of nodes and gaps, nearly reaches the dorsal tip of the platform. Neognathodus “pre-colombiensis” is more similar to N. colombiensis as the platforms of both are triangular and have asymmetrical margins.

However, N. ”pre-colombiensis” has nodes and gaps, especially in the rostral margin, on the dorsal platform, whereas N. colombiensis has complete margins. Neognathodus “pre- colombiensis” can be difficult to distinguish from N. colombiensis II because both species have incomplete margin. However, in N. colombiensis II, a larger denticle is

Texas Tech University, Paul Alex Moore, May 2017 present at the ventral outer margin, and the caudal margin is less triangular and slightly rounded.

Neognathodus colombiensis (Stibane, 1967) (Figure 24: 13-17, 24, 25)

Diagnosis: The P1 platform is triangular and contains a rostral margin that is slightly narrower than the caudal margin. The carina is medial, straight, and extends to the dorsal tip.

Description: The P1 element has a nearly symmetrical triangular platform, and is dominated by a thick, high carina, and a wide caudal margin. The caudal margin is higher than the rostral margin and also has a slight curvature and may flare out along the ventral platform. The rostral margin is less prominent and slightly narrower relative to the caudal margin. The rostral margin extends further ventrally than the caudal margin, more so in the dextral element. The ventral end of the rostral margin, and sometimes the caudal margin, may form a larger, outwardly directed node. The carina is straight, thick and extends to the dorsal tip, where is appears to slightly offset along the rostral margin.

Remarks: Stibane (1967) described N. colombiensis having a triangular platform with a carina that exceeds the platform. Most of the specimens recovered from our sections have a triangular platform, a carina that exceeds the platform, but have margins that are not exactly level in elevation, and the rostral margin appears to be narrower than the caudal margin. This species appears to be a precursor to N. colombiensis II, as they share a triangular asymmetrical platform with a wide caudal margin, and narrow rostral margin.

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However in N. colombiensis II, the dorsal rostral margin is composed of nodes and gaps, much like N. "pre-colombiensis".

Neognathodus colombiensis II (Figure 24: 1-5, 7-11, 18)

Diagnosis: The P1 element has an asymmetrical triangular platform with the rostral margin outline becoming partially incomplete dorsally, being composed of disjunct nodes that may seem to fuse with the carina. The carina is either level with or above the margin outlines and reaches the dorsal tip of the platform. The rostral margin also has a large denticle on the ventral end of rostral margin.

Description: The P1 platform is asymmetrically triangular in shape. It has a low narrow rostral margin, which has a ventral large denticle, and is composed of nodes and gaps dorsally. Dorsally, the rostral nodes partially fuse with the nodes of the dorsal carina.

The caudal margin is wider than the rostral margin, lower than the carina, and bears transverse ridges. The carina is straight and thickest in the ventral and middle areas of the platform, and thins out in the dorsal region and reaching the end of the platform.

Remarks: It is likely that Neognathodus colombiensis is the ancestor of N. colombiensis

II, because of the similarity in the triangular platform shape and ventral margins of the margins. In the transition from N. colombiensis to N. colombiensis II, the rostral margin becomes narrower and the dorsal end starts to break up into discrete nodes that partially fuse with the nodes on the dorsal carina. The transition between the two forms is gradual, however, and we choose to assign forms in which the rostral adcarinal groove disappears

Texas Tech University, Paul Alex Moore, May 2017 and the dorsal rostral margins begins to breakup to N. colombiensis II. In the younger species N. roundyi (Gunnell, 1931), the dorsal rostral margin has disappeared completely.

Neognathodus intrala Stamm and Wardlaw, 2003 (Figure 25: 1-4)

Diagnosis: The P1 element has a long, low triangular platform and carina that disappears before reaching the dorsal tip. The rostral margin is broader than the rostral margin and flares outward and flattens ventrally.

Description: The P1 element has a long, low triangular platform that is formed by low continuous margins that extend to the dorsal tip. The caudal margin is relatively narrow and may bear an elevated denticle at it ventral end. The rostral margin is wider and bears transverse ridges. Ventrally the rostral margin flares outward and flattens. The carina is high and prominent on the dorsal platform, but ventrally the carina is reduced to a thin ridge or disappears completely before reaching the dorsal tip of the platform. The grooves between the margins and carina are relatively wide and shallow.

Remarks: The triangular shape and continuous margins of Neognathodus intrala resembles those of N. colombiensis. However, the carina of N. intrala does not reach the dorsal tip as it does in N. colombiensis. Overall, the platform of N. intrala appears flatter than that of N. colombiensis and N. intrala has a ventral rostral margin that flares and lowers dorsally.

Neognathodus uralicus - N. caudatus Lineage

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In a number of Atokan to early Desmoinesian forms of Neognathodus, the dorsal end of the element is modified into a thick nodose carina. The oldest species of this group in our samples is N. uralicus, which is distinguished by an elongate, straight carina, a caudal margin that flares out slightly and reaches the dorsal tip of the platform, and a low rostral margin that terminates before the dorsal platform. Nodes also make up the dorsal caudal margin, and dorsal carina. In younger forms, the caudal margin retreats ventrally, and the dorsal end of the element consists of only the nodose carina. The high rostral margin is reduced to a short ridge that flares outward ventrally and the high caudal margin forms a long ridge parallel to the carina. Both are separated from the carina by deep grooves. Lambert (1992) included similar forms in N. caudatus Lambert, 1992, and noted that it is one of two morphotypes that he included in his species. However, the holotype of N. caudatus possesses more complete platform margins that nearly reach the dorsal tip and these margins form a high platform region that is separated from the carina by shallow grooves. Also, our morphotype appears in the middle Atokan, unlike N. caudatus, which is reported as occurring in only lower Desmoinesian beds (Barrick, et al., 2013).

Neognathodus uralicus Nemyrovska and Alekseev, 1994 (Figure 24: 26-28)

Diagnosis: P1 element has an asymmetrical triangular platform and a high carina that extends to the dorsal tip. The caudal margin is triangular in shape, widest ventrally and tapers to near the dorsal tip of the element. The rostral margin is wide, flaring, and ends

Texas Tech University, Paul Alex Moore, May 2017 well before the dorsal end of the element. The dorsal end of the carina and dorsal caudal margin consist of a few coarse, pointed nodes.

Description: The P1 element is wide, has a triangular platform with a prominent high carina. The caudal margin extends from the ventral to the dorsal part of the platform, but does not connect to the carina. The caudal margin is higher than the carina in the ventral platform, is level with the carina in the middle platform, and is reduced to a low series of nodes dorsally. The rostral margin is wide, lower than the carina, and only present in the middle portion of the platform. The carina is straight, robust, and thickest at the ventral tip, and narrows dorsally, ending as a series of coarse nodes.

Remarks: Neognathodus uralicus has often been misidentified as N. atokaensis (Barrick et al., 2004; 2013). Neognathodus uralicus is distinguished by its wide triangular caudal margin that terminates, as nodes form dorsally. The rostral margin is short and flares outward ventrally. In contrast, N. atokaensis lacks dorsal nodes, the caudal margin merges more smoothly with the carina, and it has a short rostral margin that flares out slightly on its ventral end.

Neognathodus aff. N. caudatus Lambert, 1992 (Figure 24: 6)

Diagnosis: The P1 element has a triangular, asymmetrical platform with a high carina that forms the dorsal tip of the platform. The caudal margin and shorter, flaring rostral margin vary in length, and do not extend to the dorsal end of the element.

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Description: The P1 element has a triangular, asymmetrical platform that is dominated by a high carina. The rostral margin is restricted to the middle platform and does not connect with it the carina. It tends to flares strongly outward ventrally. The caudal margin extends parallel to the carina in the ventral and middle platform region and terminates well before the end of the platform and does not attach to the carina. The carina is straight, elevated above both margins, commonly nodose and forms the dorsal end of the element.

Remarks: We did not recover any specimens that possess the morphology of the holotype of Neognathodus caudatus (Lambert, 1992, Pl. figs. 1-3). Some specimens resemble the second morphotype of N. caudatus (e.g. Lambert, 1992, pl. 1, figs. 4, 11), but even these examples tend to have longer platform margins that partially fuse with the carina.

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Figure 21: Idiognathodus species from the Sandia Formation. Figures are approximately 50X.

1, 3-6, 9 Idiognathodus sp. Q2.

1, 3. Type Sandia, unit 10.

4-6, 9. Type Sandia, unit 43.

2, 7, 8, 10-16 Idiognathodus sp. Q.

2, 7, 8, 14-16. Type Sandia, unit 10.

10-13. Presilla A, unit 27.

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Figure 22. Idiognathodus species from the Sandia and Gray Mesa formations. Figures are approximately 50X.

1, 6, 7. Idiognathodus species G.

1. Cedro Peak Z, unit 3.

6, 7. Cedro Peak Z, unit 5.

2-5, 8-11, 14, 15 Idiognathodus gibbus Lambert, 1992.

2-4, 8, 10, 11, 14, 15. Cedro Peak Z, unit 3.

2, 5, 9. Cedro Peak Z, unit 5.

12, 13, 18, 19 Idiognathodus sp. Z.

12, 13. Cedro Peak Z, unit 5.

18, 19. Cedro Peak Z, unit 3.

17, 20. Idiognathodus sp. Q. Cedro Peak Z, unit 3.

16, 21-23 Idiognathodus sp. Q2.

16, 22. Cedro Peak Z, unit 5.

21, 23. Cedro Peak Z, unit 3.

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Figure 22. Idiognathodus species from the Sandia and Gray Mesa formations. Figures are approximately 50X. Descriptions on previous page.

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Figure 23. Idiognathodus species from the Sandia and Gray Mesa formations. Figures are approximately 50X.

1, 2, 12, 14-27. Idiognathodus sp. H

1, 2, 8. Presilla B, unit 68.

12, 14, 15, 19-21, 25. Presilla B, unit 22.

16, 26, 27. Tejano Highway, unit 36.

17, 18. Cedro Peak Z, unit 13.

22-24. Tejano Highway, unit 19.

3-6, 9, 11. Idiognathodus obliquus Kozitskaya and Kossenko, 1978.

3, 4, 11. Sepultura Canyon, unit 81.

5, 6. Cedro Peak Z, unit 13.

9. Presilla B, unit 41.

7, 10, 13. Idiognathodus amplificus Lambert, 1992?

7. Presilla B, unit 57.

10, 13. Sepultura Canyon, unit 51.

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Figure 23. Idiognathodus species from the Sandia and Gray Mesa formations. Figures are approximately 50X. Descriptions on previous page.

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Figure 24. Idiognathodus species from the Gray Mesa Formation. Figures are approximately 50X.

1-4, 7-10. Idiognathodus rectus/I. iowaensis group.

1, 2, 4. Type Sandia, unit 85.

3, 8, 9. Sepultura Canyon, unit 89.

7. Tejano Highway, unit 104.

10. Type Sandia, unit 93.

5, 6. Idiognathodus obliquus Kozitskaya and Kossenko, 1978? Presilla B, unit

122.

11-23. Idiognathodus robustus Kozitskaya and Kossenko, 1978?

13, 18, 22. Type Sandia, unit 85.

11, 15, 17, 19, 23. Tejano Highway, unit 104.

14, 16. Sepultura Canyon, unit 106.

12, 20, 21. Presilla B, unit 132.

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Figure 24. Idiognathodus species from the Gray Mesa Formation. Figures are approximately 50X. Descriptions on previous page.

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Figure 25. Neognathodus species from the Sandia and Gray Mesa Formation. Figures are approximately 50X.

1-5, 7-11, 18. Neognathodus colombiensis (Stibane, 1967) II.

1. Tejano Highway, unit 165.

2, 5. Tejano Highway, unit 152.

3. Presilla B, unit 132.

4. Sepultura Canyon, unit 120.

7-11, 18. Type Sandia, unit 85.

6. Neognathodus aff. N. caudatus Lambert, 1992. Cedro Peak Z, unit 13.

12, 19-21. Neognathodus "pre-colombiensis"

12. Cedro Peak Z, unit 3.

19. Type Sandia, unit 8.

20, 21. Type Sandia, unit 10.

13-17, 24, 25 Neognathodus colombiensis (Stibane, 1967).

13. Presilla B, unit 34.

14, 15. Sepultura Canyon, unit 81.

16, 17. Presilla B, unit 28.

24. Tejano Highway, unit 19.

25. Sepultura Canyon, unit 46.

21-23, 29-32. Neognathodus atokaensis Grayson, 1984.

21, 22, 29-31. Type Sandia, unit 10.

23, 32. Type Sandia, unit 8.

26-28. Neognathodus uralicus Nemyrovska and Alekseev, 1994.

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26. Type Sandia, unit 10.

27, 28. Type Sandia, unit 8.

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Fig. 25. Neognathodus species from the Sandia and Gray Mesa Formation. Figures are approximately 50X. Descriptions on previous page.

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Figure 26. Neognathodus species from the Sandia and Gray Mesa formations. Figures are approximately 50X.

1-4. Neognathodus intrala Stamm and Wardlaw, 2003.

1. Sepultura Canyon, unit 152.

2. Sepultura Canyon, unit 159.

3, 4. Sepultura Canyon, unit 101.

7, 12-15 Neognathodus asymmetricus Stibane, 1967.

7. Presilla B, unit 86.

12, 15. Tejano Highway, unit 42.

13. Tejano Highway, unit 61.

14. Cedro Peak Z, unit 15.

5, 6, 8 Neognathodus asymmetricus, late form.

5, 6. Tejano Highway, unit 118.

8. Tejano Highway, unit 152.

9 Declinognathodus marginodosus Grayson, 1984.

Presilla A section 29.

10, 11, 17. Neognathodus bothrops Merrill, 1972.

10. Sepultura Canyon, unit 51.

11. Presilla B, unit 34.

16, 18-20, 23 Neognathodus bassleri bassleri Harris and Hollingsworth, 1933.

16, 18-20. Cedro Peak Z, unit 3

23. Type Sandia, unit 28.

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17, 21, 22. Neognathodus bassleri transitional to N. bothrops. Cedro Peak Z, unit

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Figure 26. Neognathodus species from the Sandia and Gray Mesa formations. Figures are approximately 50X. Descriptions on previous page.

100

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Table 1: Range chart of conodont species occurring in each section with their respective units

101

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Table 2: Range chart depicting occurrence of each interval in respect to the sections

102

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Chapter 8 CONCLUSIONS

The Sandia Formation and lower Gray Mesa Formation of central New Mexico record middle Atokan to early Desmoinesian conodont evolution more completely than the Midcontinent North America region. Faunas from sections in this study give greater age resolution and better constraints in terms of conodont biostratigraphy owing to the abundance and diversity of conodonts.

Biostratigraphic changes are more noticeable in Neognathodus species than

Idiognathodus species, making them easier to use for biostratigraphic subdivision. The evolution of Neognathodus is represented by three lineages: the N. bassleri - N. asymmetricus lineage, the N. atokaensis - N. colombiensis II lineage, and the N. uralicus -

N. caudatus lineage. A variety of species of Idiognathodus occur, but are more difficult to resolve because of fewer simple, diagnostic morphological features.

Six biostratigraphic faunal intervals were defined. Faunal interval 1 is based on the presence of Neognathodus atokaensis. Faunal Interval 2 is split into two subintervals.

2a is defined by the first occurrence of N. pre-colombiensis, while 2b is defined by the first occurrence of I. gibbus. Faunal Interval 3 is split into two subintervals. 3a is defined by the first occurrence of N. colombiensis and 3b is defined by the first occurrence of N. bothrops. Faunal Interval 4 is defined by the first occurrence of N. asymmetricus, and lies near the first occurrences of I. obliquus and N. aff. N. caudatus. Faunal interval 5 is defined by the first occurrence of I. robustus and Faunal Interval 6 is defined by the first occurrence of N. intrala. These faunal intervals are similar to faunal intervals recognized

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(2013). Faunal intervals 1-3a are middle to late Atokan in age. The Atokan-Desmoinesian boundary lies near the boundary between subintervals 3a and 3b. Intervals 3b-6 are considered to be early Desmoinesian in age.

The oldest conodont faunas (FI 1 and 2) were obtained from the base of the

Sandia Formation at the type Sandia section, east of Albuquerque, and the middle of the formation in the Presilla A section in the Cerros de Amado, east of Socorro. The age of the upper beds of the Sandia and the transition to the carbonate-dominated overlying

Gray Mesa Formation varies from section to section. Most commonly, the basal beds of the Gray Mesa contain a FI 3 fauna such as at Presilla B east of Socorro, and sections to the south where the Gray Mesa overlies the Red House Formation (Saelens, 2014).

However, to the north in the Los Pinos Mountains (Sepultura Canyon section) FI 3 appears in the middle of the Sandia Formation. In the Manzanita Mountains (Cedro Peak

Z section) and southern Sandia Mountains (Tejano Highway section) FI 3 appears in the uppermost beds of the Sandia Formation. The Gray Mesa Formation (Elephant Butte and

Whiskey Canyon Members, where recognized) ranges from FI 3a or 3b up through FI 6, which is early Desmoinesian ("Cherokee") in age.

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