USING OSTRACODE DYNAMICS TO TRACK ECOSYSTEM RESPONSE TO CLIMATICALLY AND TECTONICALLY INDUCED LAKE-LEVEL FLUCTUATIONS IN FOSSIL BASIN, GREEN RIVER BASIN, WYOMING, USA

A Thesis Presented to The Graduate Faculty of The University of Akron

In Partial Fulfillment of the Requirements for the Degree Master of Science

Andrew J. McFarland December, 2012 USING OSTRACODE DYNAMICS TO TRACK ECOSYSTEM RESPONSE TO CLIMATICALLY AND TECTONICALLY INDUCED LAKE-LEVEL FLUCTUATIONS IN FOSSIL BASIN, GREEN RIVER BASIN, WYOMING, USA

Andrew J. McFarland

Thesis

Approved: Accepted:

______Advisor Dean of the College Dr. Lisa E. Park Dr. Chand K. Midha

______Faculty Reader Dean of the Graduate School Dr. John P. Szabo Dr. George R. Newkome

______Faculty Reader Date Dr. Francisco B. Moore

______Department Chair Dr. John P. Szabo

ii ABSTRACT

The Eocene Green River Formation (USA) contains one of the best known Konservat Lagerstätte in the fossil record. Whereas there have been many studies performed on the vertebrate fauna, particularly the fish, there have been relatively few studies done on the invertebrate fauna such as the ostracodes from this famous fossil deposit. Two species (Candona pagei and Hemicyprinotis watsonensis) were recovered from 16 intervals and three study sites from Fossil Basin, a sub-basin of the Greater Green River Basin. The two species represent differing ecological tolerances, both mud-dwelling and plant- dwelling. This formed the basis for a reconstruction of lake levels throughout the history of Fossil Lake. This in turn can be used to examine biotic response to climate change during the Paleocene-Eocene Thermal Maximum (PETM). Stratigraphic sections were measured at three sites and sampled for ostracodes. A 1 cm x 1 cm grid was used to quantify the number of ostracode valves in each sample. Lamination counts were also performed on samples collected in Smith Hollow Quarry (SHQ), which yielded the number of laminations per millimeter. This was compared throughout the section to assess how it changed throughout Fossil Lake’s history at SHQ. Taphonomic uniformity was quantified by comparing the number of whole valves in the samples of kerogen-poor versus kerogen-rich laminated micrites (kerogen-rich micrites are thought to have been deposited under deep, anoxic water conditions), and then compared to each other. Frequencies of occurrence and abundances of individuals per bed were also compared between the two types of micrites. The trophic structure of the

iii lake was also assembled to attempt a better understanding of the community ecology of Fossil Lake. This study demonstrates the utility of ostracode species assemblages in tracking lake- level fluctuations throughout the history of Fossil Lake during a time of climate change. This has important implications and applications for studies of current climate change.

iv ACKNOWLEDGEMENTS

I would like to express my deepest thanks and gratitude to my thesis advisor, Dr. Lisa Park Boush, for all the help she has given me. Thanks for getting me interested in invertebrate paleontology, specifically ostracodes. Thank you also to my committee members, Dr. John Szabo and Dr. Francisco “Paco” Moore for their guidance during this process as well as in the classes I took with them. A large thank you to Elaine Butcher and Thomas Quick for their help and guidance; they are an invaluable asset to the department. A large thank you also goes to Arvid Aase from Fossil Butte National Monument for his hospitality and help navigating the back roads of Wyoming. I would like to thank Jerome Montgomery, quarry manager for the Green River Stone Company, for letting us use their quarry and for the guidance while we were there. I would like to thank my parents for their love and support throughout this process, from the beginning of my interest in dinosaurs, to a more refined interest in paleontology and geology in general. Thank you to my undergraduate professors, Dr. Lee Gray and Dr. Mark McNaught, who helped to broaden my interest in geology. Thanks also to Blossom Frank for her help in measuring sections in the field and cataloguing data in the lab at the University of Akron. Also thanks to Gary Motz for creating the template used to format this thesis.

v TABLE OF CONTENTS Page LIST OF FIGURES ��������������������������������������������������������������������������������������������������������� viii LIST OF TABLES ������������������������������������������������������������������������������������������������������������� ix CHAPTER I. INTRODUCTION ���������������������������������������������������������������������������������������������������������1 Paleocene-Eocene Thermal Maximum Climate Setting ������������������������������������������������2 Geologic History ������������������������������������������������������������������������������������������������������������3 Fossil Basin ��������������������������������������������������������������������������������������������������������������������5 Green River Fauna ���������������������������������������������������������������������������������������������������������6

II. METHODS ��������������������������������������������������������������������������������������������������������������������9 Sampling ������������������������������������������������������������������������������������������������������������������������9 Lamination Counts ���������������������������������������������������������������������������������������������������������9 Taphonomic Analysis ���������������������������������������������������������������������������������������������������10

III. RESULTS ���������������������������������������������������������������������������������������������������������������������11 Diversity and Lake Level ���������������������������������������������������������������������������������������������11 Fossil Basin Stratigraphy ���������������������������������������������������������������������������������������������11 Road Hollow Section ���������������������������������������������������������������������������������������������������12 Smith Hollow Quarry Section ��������������������������������������������������������������������������������������14 Bear River Gulch Section ��������������������������������������������������������������������������������������������16 Lamination Counts �������������������������������������������������������������������������������������������������������18 Ostracode Taphonomy �������������������������������������������������������������������������������������������������18

IV. DISCUSSION ��������������������������������������������������������������������������������������������������������������22

vi Stratigraphy ������������������������������������������������������������������������������������������������������������������22 Ostracode Diversity Dynamics and Lake Level Fluctuations ��������������������������������������23 Ecological Reconstruction �������������������������������������������������������������������������������������������26 Preservation ������������������������������������������������������������������������������������������������������������������26 Hydrodynamics and Relationship with the Greater Green River Basin ����������������������28

V. CONCLUSIONS ���������������������������������������������������������������������������������������������������������30 REFERENCES ������������������������������������������������������������������������������������������������������������������32 APPENDICES �������������������������������������������������������������������������������������������������������������������37 Appendix a. Rock Descriptions �������������������������������������������������������������������38 appendix B. Ostracode Data �����������������������������������������������������������������������45 appendix c. Lamination counts ������������������������������������������������������������������56

vii LIST OF FIGURES Page Figure 1 Distribution of the Green River Formation within Fossil Basin, indicating the locations of the sites sampled for this study ������������������������������������������������������4 2 Stratigraphic column of the Green River Fm as measured at Road Hollow, showing lithologies and locations of fish and ostracodes ��������������������������������������13 3 Stratigraphic column of the Green River Fm as measured at Smith Hollow Quarry, showing lithologies and locations of fish, plants and ostracodes �������������15 4 Stratigraphic column of the Green River Fm as measured at Bear River Gulch, showing lithologies and locations of fish, plants and ostracodes ���������������17 5 A. Frequency of occurrence chart for the number of beds with ostracodes as compared to the total number of occurrences for both kerogen-poor and kerogen-rich micrites. B. Abundance of individuals per bed for both kerogen-poor and kerogen-rich micrites. C. Number of beds with whole valves preserved for both kerogen-poor and kerogen-rich micrites. ���������������������19 6 Composite stratigraphic section of the Green River Formation exposed in Fossil Basin and comparing lamination counts/mm, ostracode species valve counts/cm2, and an interpretation of lake level throughout the lake’s history �������24 7 Paleoecological web displaying energy transfer from solar radiation at the bottom, through primary producers and primary consumers, to secondary consumers at the top �����������������������������������������������������������������������������������������������27

viii LIST OF TABLES

Table Page

1 Table of ostracodes recovered from Fossil Basin, according to Swain et al. 1971 ����������������������������������������������������������������������������������������������������20

ix chapter i introduction

Understanding how ecosystems in general and terrestrial ecosystems in particular, react to abiotically-induced change in the geological past is important for determining system thresholds and parameters related to biotic response to changes due to climatic and/or tectonic drivers. Knowing the nature and rate at which communities have been modified in relation to changes in climate and basin morphology will help define various boundary conditions that might exist in these heterogenic systems. The geological record is replete with instances of biological changes or shifts in community structure in response to environmental transitions, but examining them over critical intervals of geologic time allows those boundary conditions to be better constrained. In each of these cases, there was a marked response of the ecosystem to these large climate changes. Response thresholds varied and were integrated in feedbacks that pushed the system in various ways that do not necessarily represent present day conditions. Well-documented examples of this climate-biotic response include the Miocene C3/C4 vegetation shift (Cerling, 1991; Pagani et al., 1999), the faunal shift at the Eocene/Oligocene boundary and faunal response to the Carboniferous CO2 excursion (Berner, 2004, 2009; Montanez, et al., 2007; Bishop et al., 2009; DiMichele et al., 2009). But, perhaps the most significant biotic response to warming or cooling climates may be seen in the Paleocene- Eocene Thermal Maximum (PETM) (Bains et al., 1999; Bowen et al, 2004; Pagani et al., 2006; Panchuk et al., 2008; and Zachos et al., 2008).

1 Paleocene-Eocene Thermal Maximum Climate Setting

The Paleocene-Eocene Thermal Maximum (PETM) is one of the best documented and well-known examples of an ancient warming event. Occurring at approximately ~56 million years ago with repeated (millennial-scale) massive releases of “fossil” carbon and a major disruption of the carbon cycle, it spans the Green River Formation and had significant impact on the overall hydrology of the multiple lake system (Bains,et al., 1999; Bowen et al, 2004; Pagani et al., 2006; Panchuk et al., 2008; and Zachos et al., 2008). The exact origin of the large amounts of carbon-based greenhouse gasses that is attributed as the cause of this abrupt climate change is still in debate, but it is agreed that the sudden release of carbon into the ocean-atmosphere system occurred at rates vastly exceeding typical rates known throughout Earth history. The resulting effects on climate were to make mid- to high- latitudes wetter with increased extreme precipitation events, whereas other regions such as the Western Interior became more arid (Schmitz and Pajulte, 2007). The effects on the Eocene ecosystems were profound, causing large-scale ecological disruption, mostly resulting in massive migrations of fauna and flora as well as extinctions, such as marine foraminifera (Dawson et al., 1976; Thomas and Shackleton, 1996; Wing et al., 2003; and Markwick, 2007). As a rare instance where the influence of past rapid thermal change is captured with high resolution, the PETM is critical for understanding future climate conditions in the current Anthropocene. Lakes in the Eocene are associated with rift and thrust zones that are spread across North America, southeast Asia, Australia, and western Europe. The large number of lakes in the Eocene, as shown by their preserved deposits, might have responded to as well as added to the overall climatological changes during this time period (Gierlowski- Kordesch et al., 2008). There are well-known lake deposits from the Eocene time period,

2 many of which contain important fossil deposits. The Green River Formation is arguably the most significant. The Eocene Green River Formation is a large, complex set of lacustrine deposits occurring in various sub-basins and associated drainages that spans southwestern Wyoming, northwestern Colorado, and northeastern Utah, USA. It encompasses various basins in Colorado, such as the Uinta and Piceance Creek, and in Wyoming such as the Gosiute and Fossil basins. Some of these basins were connected at various times throughout their history (Carroll et al., 2008). This study focuses on Fossil Basin of southwestern Wyoming (Figure 1) which was hydrologically connected to the Gosiute and Uinta basins at various times in its history (Carroll et al., 2008; Ingalls and Park, 2010).

Geologic History

Much of the previous work on the Green River Formation has focused on reconstructing the depositional history of the Greater Green River Basin (GGRB) (Bradley, 1929, 1931, 1964, 1970; Picard and High, 1972; Eugster and Hardie, 1975; Lundell and Surdam, 1975; Surdam and Wolfbauer, 1975; Ryder et al. 1976; Desborough, 1978; Eugster and Hardie, 1978; Surdam and Stanley, 1979; Carroll and Bohacs, 2001; Smith et al., 2003; Pietras and Carroll, 2006; Smith et al., 2008) and on documenting and describing the various fossils found within the lake beds (Swain, 1956, 1964; Kaesler and Taylor, 1971; Swain et al., 1971; Taylor, 1972; McGrew, 1975; Grande, 1984; Grande and Buchheim, 1994, Ferber and Wells, 1995; Swain, 1999). These studies have characterized the dynamic history of the three separate basins within the context of tectonic and climatic regimes. The GGRB began as a foreland basin during the Laramide Orogeny (Late Cretaceous to Middle Eocene) and was divided into its various sub-basins 3 Figure 1. Distribution of the Green River Formation within Fossil Basin, indicating the locations of the sites sampled for this study.

4 by uplifts of Precambrian basement rock and by subsequent folding events throughout this time frame. This led to the staggered formation of the three major lake basins—Lake Uinta, Lake Gosiute and Fossil Lake; and one minor basin, the Piceance Creek basin (Beck et al., 1988; Roehler, 1992 A; Rhodes et al., 2002; Pietras and Carroll, 2006). The Piceance and Parachute Creek members were formed and deposited in the Piceance Creek sub-basin in Colorado. The Piceance Creek is separated from the Uinta sub-basin by an east-west trending anticlinal uplift. This basin was formed from a shallow playa lake that responded rapidly to the changes in climate at the end of the Paleocene, similar to the majority of the GGRB (Smith et al., 2008). This study focuses on the smallest of these, Fossil Basin.

Fossil Basin

Fossil Basin is a structural basin created by thrust-faulted ridges of north-south trending Paleozoic-Mesozoic rocks (Buchheim and Eugster, 1998). It is bordered by the Tunp Range to the northwest, Oyster Ridge to the east, and unnamed ridges east of the Crawford Mountains to the southwest (Buchheim and Eugster, 1998). The Green River sediments, mostly micritic and dolomicritic, are present in an asymmetrical syncline trending northeast within the basin; faults have deformed sediments of the western portion of the basin (Buchheim and Eugster, 1998). The age of strata within Fossil Basin has been determined through various methods. Lacustrine units of the basin have been assigned to late Early Eocene age, verified by mammalian fossils, known to be Early Eocene from other studies, found in Wasatch strata (Gazin, 1952; Smith et al. 2003). Fossil Butte, a member within the Green River Formation exposed in Fossil Basin, was radiometrically determined to be 51.66 +/- 0.09

5 Ma (late Early-Middle Eocene) from the K-spar tuff, a marker bed near the top of the member (Buchheim and Eugster, 1998; Smith et al., 2008).

Green River Fauna

The Green River is internationally renowned for its exceptionally well-preserved lacustrine and terrestrial fossils that include spectacular fish and plant faunas and floras, as well as rarer birds, bats, alligators and insects (McGrew, 1975; Grande, 1984; Roehler, 1992 A and 1992 B; Grande and Buchheim, 1994; Ferber and Wells, 1995; Ksepka and Clarke, 2010). The fauna has outstanding preservation, displaying soft tissues as well as rare fossil entities. This exceptional level of preservation is due to various environmental factors involving anoxia and limitation of biological degradation, which mostly are related to water depth and oxygen stratification. The flora of the formation resembles the flora of the southeastern United States, suggesting a warm and humid climate (McGrew, 1975). The most well-known fossils of the Green River Basin are the diverse and abundant fish — considered one of the best examples ofKonservat Lagerstätte in the history of life (Grande, 1984). There are at least 16 different fish families represented within Fossil Basin; the dominant being the herring family (Clupeidae) (Grande, 2001). Others include the Priscacaridae (perch), Lepiosteidae (gars), and even Dasyatidae (a family of the ray superorder). Fish are found throughout Fossil Lake, but each species is thought to have existed within its environmental tolerances. Individual ecologies might have varied but the Clupeidae tend to be surface-feeders, whereas the Gonorynchidae are bottom-feeders. The larger fish were thought to be cosmopolitan, as they searched for prey throughout the lake, and the smaller fish stayed closer to shore. The fish represent both herbivorous and

6 carnivorous species. Juveniles as well as adults are present and are an important part of the ecology of Fossil Lake. Other fossils found within Fossil Basin include turtles, crocodiles, and birds. Mammals such as horses and the earliest-known fossil bat are also present but are relatively rare (Jepson, 1966). It has been determined that the flora surrounding Fossil Lake was a mixed-forest type. Palms, willows, laurels, and fig trees are found nearest to the water, while deciduous trees such as oak, maple, elm, and beech have been found on the lower slopes of the mountains, and conifers-spruce, fir, and pine, have been indicated by fossil pollen. This indicates that the flora of Fossil Basin ranges from tropical, to temperate, to coniferous (McGrew, 1975). Whereas much is known about these macrofaunal and macrofloral elements, less is known about the aquatic invertebrate fauna, primarily the mollusks and ostracodes found within Green River deposits (Swain, 1956, 1964; Kaesler and Taylor, 1971; Swain et al., 1971; Taylor, 1972; Swain, 1999). These taxa include four species of bivalves, five species of gastropods and five species of ostracodes (Swain, 1964; McGrew, 1975). Aquatic gastropods of Fossil Basin were herbivorous and fed in the shallower margins of the lake (McGrew, 1975). Insects are most often found carbonized as flat outlines, a result of large amounts of overlying pressure driving off volatile substances. Beetles and dragonflies are relatively common, but over 80% of the insects found at the 18-inch layer are a species of fly (Grande, 1984). While not a particularly diverse fauna in comparison with the other taxa within the GRF, these aquatic invertebrates provide critical clues to the reconstruction of paleoenvironmental conditions, including the connection of the drainages of the various sub-basins within the greater Green River system (Ingalls and Park, 2010). Ostracodes are microcrustaceans with bivalved carapaces made of low-Mg calcite. They have specific environmental tolerances, abundant distribution, and are typically well

7 preserved (Swain, 1964; Swain et al., 1971; Taylor, 1972; Wells et al., 1999; Frenzel and Boomer, 2005), and as such, they provide an effective means by which to evaluate the biologic response to known and documented lake-level changes, as well as hydrologic connections and drainages of the various basins in the area. Various species are found in different environments ranging from a marginal lake setting to open water (Swain, 1964). Swain published a number of studies on the early Tertiary ostracode distribution throughout the Green River Basin (Swain, 1956, 1964; Swain et al. 1971; and Swain, 1999). His work focused on early Tertiary ostracode zones (Swain, 1956) and the stratigraphic distribution of early Tertiary freshwater ostracodes (Swain, 1964) as well as the paleoecology of fossil Cenozoic non-marine ostracodes (Swain et al., 1971). Taylor initially described the paleoecological aspects of the Green River Formation and found that Lake Gosiute ostracodes generally responded positively to higher clay content. Ostracodes were also found to prefer quiet water, as their shells are small and fragile, and that any valves found in coarser-grained rocks indicative of a higher energy environment must be carefully scrutinized as to make sure they were not transported (Taylor, 1972). By tracking shifts in ostracode assemblages, environmental changes through time can be observed. In this study, I examined changes in ostracode community assemblages as related to lake basin dynamics. Specifically, the questions that I addressed included the following: 1) are there changes in ostracode species diversity that might track lake level fluctuations? 2) are there distinctive preservational modes for ostracodes within Fossil Basin that might differ from Lake Gosiute? and 3) was Fossil Lake hydrologically linked to other contemporaneous lakes, such as Lake Gosiute during the Eocene epoch? and what significance did that have in overall GGRB hydrodynamics?

8 chapter ii methods

Sampling

Stratigraphic sections extending from the Road Hollow Member though the Angelo Member were measured and described at Road Hollow, Bear River Gulch and Smith Hollow Quarry (Figure 1). Each unit that contained ostracodes was sampled at 1-cm intervals to obtain a high-resolution record of ostracode dynamics throughout the measured section(s). Samples containing ostracodes were examined under a binocular dissecting microscope. To quantify the number of ostracodes in each sample, a 1 cm x 1 cm grid was used and placed in random locations on each of the samples. By counting the number of ostracodes in each 1 cm2 grid and totaling the number of ostracodes found throughout each of the grid squares in the sample, the total number of ostracodes was estimated in each sample.

Lamination Counts

Laminated samples were collected throughout the Smith Hollow Quarry site at the following intervals: S1001-1, S1001-2, S007-1, S007-2, S010, S040-1, and S040-2. Thin sections of each interval were created and the number of laminations per millimeter was counted under a binocular microscope. The changes in lamination counts/mm were 9 then compared to the changes in ostracode species throughout the section to better display variation in lake level.

Taphonomic Analysis

The taphonomy and preservational mode of ostracode valves, specifically, whether they were casts, molds, recrystallized or unaltered was examined for all specimens. The dominant mode of preservation in each unit and/or section was compared between the sections using a qualitative scale to establish whether change in species or lake levels affected the taphonomic character of the ostracodes.

10 chapter iii results

Diversity and Lake Level

The ostracodes recovered change along with facies changes (Figure 6). In the middle of the section, where micrites with high lamination counts are found, there are more occurrences of Hemicyprinotus watsonensis, whereas at the top and bottom of the sections, where there are more incidences of bioturbated micrites, and more interbedded sandstones and siltstones in the Angelo Member, there are higher frequencies of Candona pagei.

Fossil Basin Stratigraphy

The stratigraphy of Fossil Basin is currently under debate and in the process of revision (Buchheim et al., 2002). The rocks of the basin were formerly separated into three members and for simplicity’s sake are referred to by the older naming scheme — from oldest to youngest: the Road Hollow, Fossil Butte, and Angelo members. The Road Hollow Member is composed of bioturbated micrites, laminated calcimicrites, siltstones and sandstones. The various siliciclastic rocks found here most likely represent hydrologic connections between Fossil Lake and Lake Gosiute via streams. The Fossil Butte Member is composed of predominantly laminated calcimicrites. It was likely deposited at a time when the lake was at its largest extent, as shown by the laminated 11 calcimicrites which are typically deposited in deep, still water (Buchheim, 1994). The dark color of the rocks could indicate that there was an anoxic zone at the bottom, slowing down bacteria and thus the decomposition of the organism. This is the reason for the excellent preservation of these fossils. The Angelo Member is composed primarily of dolomicrites, sodium bicarbonate salts and chert (Buchheim et al., 2002). This member has been interpreted to represent the gradual shrinking of the lake; as it evaporated, it turned more saline, resulting in the deposition of the characteristic lithologies of this unit.

Road Hollow Section

The section at Road Hollow measured approximately 115 m thick and contained four distinct depositional cycles that consisted of micrites and siliciclastics from the Road Hollow Member (Figure 2). The average thickness of each of the four cycles was approximately 29 m. The section measured at Road Hollow contained alternating carbonate and siliciclastic units toward the upper and lower portions. The upper portion alternated from kerogen-rich laminated micrites to siltstones and sandstones, most likely representing large fluvial inputs into the lake. The lower portion alternated from siltstones to structureless micrites, possibly representing smaller fluvial inputs. Depositional sequences generally graded from laminated micrites or bioturbated micrites, to dolomicrites. Siliciclastics were more prevalent toward the top of the section, with a light tan, fine-grained, moderately-well sorted sandstone capping unit that is the end of the GRF in that location. The microlaminated micrite layers contained ostracodes. Ostracodes recovered from lower units of this member were Candona pagei and are indicative of a more marginal lake setting. The upper units of this member contained ostracodes representative of deeper water, Hemicyprinotis watsonensis. These units also

12 Figure 2. Stratigraphic column of the Green River Fm as measured at Road Hollow, showing lithologies and locations of fish and ostracodes

13 contained orders of magnitude greater numbers of individuals than lower units. Some fish fossils were recovered in separate laminated micrite layers.

Smith Hollow Quarry Section

The measured section at Smith Hollow Quarry was approximately 36 m thick and contained three distinct depositional cycles that consisted of micrites and dolostones, spanning the Upper Angelo and Fossil Butte Members (Figure 3). The average thickness of each cycle is about 12 m. The lower part of the section was dominated by microlaminated micrites, but also included thin beds of siliciclastics; these units were generally volcanic tuffs. These tuffs, while relatively thin, were numerous throughout the section. The upper part of the section was dominated by dolomicrites. Depositional sequences at this site graded from kerogen-rich to kerogen-poor, microlaminated micrites to dolomicrites. The nature of the contacts at this site was generally sharp between siltstones and micrites, and gradational between kerogen- poor and kerogen-rich micrites. This is expected, as one would assume a period of erosion between deep-water and fluvial sediments. Ostracodes were again found in microlaminated micrites, along with dolomicrites. Fish, gastropods and some plant material were also discovered in microlaminated micrites. Abundant fish were found within rocks in this section, mostlyKnightia spp., but larger species — Diplomystus spp., Mioplosus spp., Notogoneus spp., Priscacara spp., and Phareodus spp. were also seen or are known to exist in this member. Ostracodes recovered from this member belong to the species Hemicyprinotis watsonensis and are indicative of a deeper water environment; Candona pagei was not recovered from any rocks of this member.

14 Figure 3. Stratigraphic column of the Green River Fm as measured at Smith Hollow Quarry, showing lithologies and locations of fish, plants and ostracodes.

15 The number of ostracode individuals was relatively high, which correlates to what was previously seen of units with Hemicyprinotis watsonensis individuals from the Road Hollow Member. Ostracodes that were recovered from the Angelo Member at the top of the section belonged to Candona pagei. Small, most likely juvenile fish were also recovered, along with gastropods, indicating a marginal setting.

Bear River Gulch Section

The section at Bear River Gulch measured approximately 166 m thick and contained six depositional cycles consisting of micrites and dolostones of the Road Hollow Member (Figure 4). The average thickness of each cycle is about 27 m. The lower part of the section contained both microlaminated micrites and dolomicrites. The dolomicrites gradually disappeared at the middle, with sandstone intertongues gradually appearing. Toward the top, the section had alternating microlaminated micrites and bioturbated micrites, eventually being capped off by coarse-grained, flaggy sandstones. The depositional sequence generally graded from microlaminated micrites, to bioturbated micrites, to dolomicrites. The units toward the top of the Bear River Gulch section contained several interbedded, kerogen-rich, structureless, and laminated micrites along with sandstones and other siliciclastics. The contacts between structureless and laminated micrites were gradational, whereas contacts between micrites and siliciclastics tended to be abrupt. Due to the lack of dolomicrites characteristic of the Angelo Member, the rocks of this section are most likely from the Road Hollow Member. Ostracodes were found in both microlaminated as well as bioturbated micrites. Some fish were found to occur in microlaminated micrites. Gastropods and plant material were also discovered in dolomicrites and bioturbated micrites, respectively.

16 Figure 4. Stratigraphic column of the Green River Fm as measured at Bear River Gulch, showing lithologies and locations of fish, plants and ostracodes. 17 Lamination Counts

Lamination counts of the seven samples taken from Smith Hollow Quarry had counts/mm ranging from more coarsely-laminated units (2.33 laminations/mm) up to the more finely-laminated (26.5 laminations/mm). If these represent varved sediments, the years represented range from 1.7 years/mm, to 13.3 years/mm. The lamination counts were plotted along with the laminations/mm for each of the samples. The lamination counts were taken from both kerogen-rich and kerogen-poor micrites. The laminations themselves were made up of alternating light and dark bands of calcite. Most were fine-grained, but one layer in the Fossil Butte member had considerably larger-sized siliciclastic grains (Figure 5, GR09FBFB-040). This material was most likely from a different source than the other grains within this unit, possibly from either fluvial or volcanic input.

Ostracode Taphonomy

Two ostracodes species were recovered from 16 intervals throughout the Road Hollow, Fossil Butte and Angelo members. These included the eurytypic plant dwelling species Candona pagei, which occurs in organic and carbonate-rich environments and Hemicyprinotis watsonensis, which was a eurytypic mud dweller that occurs in every type of environment (Kaesler and Taylor, 1971; Swain et al., 1971) (Table 1). An additional mud-dwelling species, Cypridea bisulcata, has been reported from carbonate and bituminous environments within Fossil Basin by Swain (Swain et al., 1971) but that species was not recovered in this study. The ecology of these two species of ostracodes is different from other sub-basins of the Green River Formation. In the Gosiute Basin, the ostracodes recovered were not only 18 Figure 5. A. Frequency of occurrence chart for the number beds with ostracodes as compared to total occurrences Figure 5. Abundance of individuals per bed for both kerogen-poor and kerogen-rich for both kerogen-poor and kerogen-rich micrites. B. micrites. C. Number of beds with whole valves preserved for both kerogen-poor and kerogen-rich 19 1971. et al. Table 1. Table of ostracodes recovered from Fossil Basin, according to Swain Table 1. Table 20 more diverse, six species having been recovered, but were also more abundant, occurring in more units (Ingalls and Park, 2010). In the Gosiute, only a portion of the total ostracode species was found in each unit, with three species being the most abundant. Both species recovered from Fossil Basin were found in the same lithologies in the Gosiute Basin, confirming the ostracodes specific environmental tolerances. Ostracodes were found most often in kerogen-poor, microlaminated micrites and Candona pagei was found in conjunction with this lithology. While more kerogen-poor units contained ostracodes, kerogen-rich units provided more ostracodes per cm2 (Figure 5A, B). The dominant mode of preservation for most of these ostracodes is recrystallization by calcite. There was some preservation of original shell material within kerogen-rich, microlaminated micrites of mostly Hemicyprinotis watsonensis. There were also some examples of three-dimensional preservation most often occurring in kerogen-poor, microlaminated, and structureless micrites. Ostracode valves were mostly found intact and unbroken in kerogen-poor samples, whereas in kerogen-rich samples, they were found compressed and often broken (Figure 5C). Sediments deposited shortly after the major volcanic tuff event within the section proved to be devoid of any fossils. One exception is the unit above the K-spar tuff, which contained ostracodes as well as gastropods and Knightia fish. These organisms were not found until 40 cm above the K-spar, in the unit known as the “minifish layer” which has mostly juvenile Knightia fish preserved.

21 chapter iv discussion

Stratigraphy

Fossil Lake was a dynamic lacustrine system that responded to both climatological and tectonic changes within the basin. In its infancy, it was a fluctuating profundal (balance-filled) lake in which finely-laminated, kerogen-rich micrites were formed and deposited. Over the history of this lake, it progressed into more of an evaporative (underfilled) lake, dominated by dolomites, with salt casts being present in the upper units. It is possible for an underfilled lacustrine system to have fluvial inputs, which can be seen as wedges of coarser-grained sandstones of the Wasatch Member in the upper parts of the measured sections, especially in the sites located toward the margins of the lake basin. The Road Hollow Member in Fossil Basin is representative of an overfilled lake system and represents the earliest stage of Fossil Lake (Buchheim et al., 2011). Micrites comprise the great majority of the rocks of this member (see Appendix A), whereas dolomicrites are relatively rare. The Fossil Butte Member (FBM) is the best known of the three members representing Fossil Lake, containing the “18-inch layer” and the exceptionally well-preserved fossils located within. It is comprised of rocks that are characteristic of a relatively deep, balance-filled, lacustrine system; kerogen-rich and kerogen-poor laminated micrites abound, with some dolomicrites appearing near the top. Various tuffs are also found

22 throughout the member, each around one cm thick, with the thicker K-spar tuff occurring at the top of the member. The lithology changes from kerogen-rich to kerogen-poor micrites up-section in the FBM. This would indicate the lake had an anoxic layer at the bottom and then lost that layer through time. The Angelo Member represents the end of Fossil Lake’s existence, characteristic of an underfilled lake. It is dominated by dolomicrites, with some interfingering sandstone tongues appearing toward the top of the measured section of this member. The measured sections correlate to the overall basin tectonics model in a broad context. As the thrust-faulting event was creating this lake basin during Road Hollow Member-time, the lake was expanding and probably depositing micrites. As basin subsidence slowed down with the end of thrust-faulting, the lake became balance-filled at its largest extent, during Fossil Butte Member-time, developing an anoxic zone on the bottom that allowed for the deposition of kerogen-rich micrites and the excellent preservation of fossils. As time went on, the lake began to dry out, becoming saline and hypersaline toward the end of its existence during Angelo member-time. Fluvial connections were made and led to the deposition of sandstones toward the top of this member, and the lake gradually disappeared at the beginning of the Middle Eocene epoch (Figure 6).

Ostracode Diversity Dynamics and Lake Level Fluctuations

The ostracodes recovered from the Fossil Butte member are indicative of a deeper lake. Although not many ostracodes were found in kerogen-rich micrites deposited under anoxic conditions, many were still deposited in laminated micrites, so the sediments were deep enough not to be disturbed by bioturbation or wave action. There is what is referred to as an “ostracode coquina” toward the top of the section, directly below the K-spar 23 , and an interpretation of lake level throughout the lake’s history. , and an interpretation of lake level throughout the lake’s 2 Figure 6. Composite stratigraphic section of the Green River Formation exposed in Fossil Basin and comparing lamination counts/mm, ostracode species valve counts/cm 24 tuff. It is a kerogen-rich, laminated micrite and has a high number of three-dimensionally preserved Hemicyprinotis watsonensis valves. This could be a mass mortality layer related to anoxia, or transport of the ostracodes from some other location (Figure 3, 7). Fish recovered from this member were mostly small Knightia spp. These are surface feeders, and would most likely stay toward the margins of the lake. Phosphatic deposits were seen in the field parallel to the bedding plane in both kerogen-poor and kerogen- rich, microlaminated micrites, indicative of preserved fish remains. These, however, were not extracted from the rock, so no species identification was available. Large, predatory fish were most likely to venture into the middle of the lake, where it was deepest, and so they could be preserved as these phosphatic deposits. Although only two species of ostracodes were found within the samples collected, they had different environmental tolerances. Hemicyprinotis watsonensis is a eurytypic mud-dweller representative of deeper conditions of the lake, whereas Candona pagei is a eurytypic plant-dweller, and representative of shallower conditions. Hemicyprinotis watsonensis is generally distributed in carbonate and organic-rich environments (Table 1) and what was observed in samples where it was found reinforces that. Hemicyprinotis watsonensis was often found in great numbers, possibly a result of mass mortalities. This could also be indicative of deeper lake conditions, where a turnover of the lake could have created anoxic conditions. It is known that the water level of Fossil Lake fluctuated throughout its history, and this can be seen in the ostracode assemblages. At the Road Hollow locality, a marginal setting, the ostracodes recovered are transitioned from the plant-dwelling Candona pagei to the mud-dwelling Hemicyprinotis watsonensis. This transition from shallower, plant-dwelling species to deeper, mud-dwelling species indicates that the lake level increased, and therefore the lake was growing during this time. The opposite can be seen during Angelo Member time at the Smith Hollow Quarry site. The mud-dwelling

25 Hemicyprinotis watsonensis transitioned to Candona pagei, suggesting a shallowing of lake level. I interpret this as the ostracodes reflecting fluctuations in lake levels over time.

Ecological Reconstruction

Ostracodes were found within the coprolites of an undetermined fish species, possibly Knightia spp., based on the size and shape of the feces. The fecal material could also have been from the bottom-feeding Notogoneus osculus, which could have ingested them, as the structure of its mouth was oriented in a downwards fashion, suggesting that it took in sediment off the substrate and filtered out its food. Larger fish inhabiting Fossil Lake, such as Diplomystus spp., Priscacara spp., and Mioplosus spp., were predators, and, in some cases, have been found fossilized with other fish in their mouths so they most likely did not feed on ostracodes (Grande, 1984). Fossils of Mioplosus spp., a large predator, have been found fossilized with smaller fish in the mouth. This is important because it lends credibility to the fact that it was a top predator in the lake. Phareodus spp. is also considered to be an apex predator within Fossil Lake, (Grande, 1984) (Figure 7).

Preservation

Ostracodes were found to be mostly preserved by recrystallization by calcite. This is similar to what was seen in Lake Gosiute by Ingalls and Park (2010). This could reflect similar conditions in both lakes, yielding similar taphonomic results. There were also some specimens that appeared to be original shell material but a detailed analysis of the

26 Figure 7. Paleoecological web displaying energy transfer from solar radiation at the bottom, through primary Figure 7. Paleoecological web displaying energy producers and primary consumers, to secondary consumers at the top.

27 composition of the valves was not performed. Three-dimensional preservation was also common in kerogen-poor units and some dolomicrites. The taphonomy of Fossil Basin responds to energy of the lake and anoxia levels. The deep, still waters where kerogen-rich, microlaminated micrites were deposited and large numbers of Hemicyprinotis watsonensis were found, also have greater instances of broken valves. This is most likely due to the greater depths of the lake and the higher water pressure associated. The rocks themselves were not cracked, so the valves were most likely broken after deposition, and not as a result of lithification. In the sites dominated by kerogen-poor, bioturbated micrites, anoxia and the pressures associated with deep water were not factors. Because the bioturbation whether by gastropods or fish such as Notogoneus osculus destroyed any bedding planes, the ostracodes were found without any preferential orientation. The valves were found unbroken, and often were found with three-dimensional preservation. These differential modes of preservation of ostracode valves are the result of the depositional changes occurring throughout the existence of Fossil Lake.

Hydrodynamics and Relationship with the Greater Green River Basin

Of the three major basins of the Green River Formation, Fossil Lake is thought to be the deepest, due to the development of kerogen-rich, microlaminated micrites. While actual estimates are difficult, there are estimates of a 4-5 m depth during Road Hollow time. This is relatively shallow, as it is an estimate of the depth during a time where the lake was smaller, with more marginal-indicative sediments were being deposited (Buchheim and Eugster, 1998). Lake Gosiute and Lake Uinta are mostly thought of as playa lakes (Lundell and Surdam, 1975; Surdam and Wolfbauer, 1975), and as such, would have lacked anoxic bottoms. It has been suggested that Fossil Lake might have 28 had a different mixing regime and was potentially permanently stratified during the times of major fossil preservation in Fossil Butte Member time. The permanent anoxia, along

with other factors such as higher levels of CaCO3 deposition during certain parts of the year, would have allowed organisms to have a slower rate of decay, which in turn would have yielded fossilization of soft tissues (McGrew, 1975). Due to its similar modes of preservation, it seems that Fossil Lake could have been connected hydrologically to other contemporaneous lakes, specifically Lake Gosiute as its relatively close proximity to Fossil Lake makes it the strongest candidate for establishing any interbasinal connections of the GGRB. This argument can be strengthened when linked with other factors, such as siliciclastic inputs into Fossil Lake. There are many instances of such inputs during both Road Hollow and Angelo time. During the Road Hollow, there are two large sandstones that mark the end of RH time; these are wedges of the fluvial Wasatch Formation, and most likely come from the ridge separating Fossil Lake and Lake Gosiute. During Angelo unit time, there are many instances of interbedded sandstones. As the lake was drying up, smaller channels may have developed. These perhaps could have developed into proper connections at some point, but more study of the sedimentology of the Wasatch Formation within Fossil Lake and Lake Gosiute is required before it can be said with any certainty.

29 chapter V conclusions

The results of this study illuminate how faunal tracking occurs in response to changes in lake level. The two species of ostracodes, each with their specific ecological tolerances, correlate to other indicators of lake level such as lamination counts and changes in lithology. The ostracodes of Fossil Basin are predominantly preserved by replacement by calcite, and are most often found in kerogen-poor laminated micrites. They are found in greater numbers, however in kerogen-rich micrites. Valves that were found in kerogen-poor micrites tended to be better preserved, often three dimensional; in kerogen-rich, the valves tended to be compressed and broken, most likely due to the greater depths at which they were deposited. Fossil Lake has been shown to have been connected to other contemporaneous Green River lakes, most likely Lake Gosiute due to its close proximity. The ecological dynamics of Fossil Lake discovered during this study can be used to create a better picture of the Greater Green River lakes as one system, rather than separate entities. This in turn is important for understanding climatological and tectonic drivers and the effects they have on entire regions. Future study needs to be done- in particular, better sampling of ostracodes in an attempt to recover more species and individuals. Also necessary is the age-dating of tuffs found within each basin, which can then be used to link Fossil Lake to the other contemporaneous lakes. This is important for the ecological dynamics as well as the sedimentological and hydrological connections between the lakes. However this study

30 reinforces that invertebrates, especially ostracodes and their species dynamics, can be used to assess changes in lake level throughout time. This, when used in other lake basins, can then be compared to modern-day changes to lake level in similar extant lakes. This can be used to extrapolate current rates of climate change versus rates of climate change in the fossil and rock records.

31 references

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36 APPENDICES

37 appendix a Rock Descriptions

Smith Hollow Quarry

GR09FBFB-S1001 Light brown to brown kerogen poor microlaminated micrite, weathers to light tan, laminations range from .50 mm to 1 mm thick, fish, coprolites, and ostracodes present, phosphatic deposits GR09FBFB-S1002 Dark brown tuff, weathers to yellow tan and orange, very fine grained, well indurated GR09FBFB-S001 Brown kerogen rich laminated micrite, weathers to light tan, similar to unit GR09FBFB-1001, laminations are between 0.5 mm and 1 mm, plant material present, moderately to well indurated GR09FBFB-S002 Orange tuff, weathers to light orange, fine grained, well indurated GR09FBFB-S003 Brown kerogen rich microlaminated micrite, weathers to light tan, laminations range from .2 mm to 3 mm thick GR09FBFB-S004 Light orange tuff, weathers to dark orange, medium grained, well indurated GR09FBFB-S005 Dark brown kerogen rich microlaminated micrite, weathers to light tan, laminations range from .2 mm to 1 mm thick, plant material present, bottom 1 cm more organic than top 3 cm GR09FBFB-S006 Light orange tuff, weathers dark orange to burnt orange, reworked, possibly water lain, void spaces GR09FBFB-S007 Dark brown to dark gray kerogen rich laminated micrite, weathers to light tan, laminations range from .5 mm to 2 mm, oily smell GR09FBFB-S008 Blue-gray kerogen rich microlaminated micrite, weathers to light tan, siliciclastic layers 15 cm from the top and reaches 23 cm below that (each 3 cm thick), fish and coprolites present, "18 inch layer" GR09FBFB-S009 Dark gray muddy siltstone, weathers a yellow to light brown, moderately indurated with massive bedding, plant material present GR09FBFB-S010 Light tan and dark brown kerogen rich microlaminated micrite, weathers to buff and light gray, laminations alternate between light tan and dark brown GR09FBFB-S011 Gray muddy siltstone, weathers to light tan, moderately indurated with massive bedding, plant material present GR09FBFB-S012 Gray kerogen rich microlaminated micrite, weathers a light tan to light orange 38 GR09FBFB-S013 Light yellow tuff, weathers to buff, very fine grained, ash filling in undulated surface GR09FBFB-S014 Yellow dolomicrite microlaminated and structureless, weathers to buff GR09FBFB-S015 Tan kerogen poor microlaminated micrite, weathers to yellow-orange GR09FBFB-S016 Creamy orange dolomicrite, weathers white and orange, microlaminated and structureless, undulating contact, ash bed 5 cm thick on top GR09FBFB-S017 Brown kerogen rich laminated micrite, weathers slightly yellow-tan, laminations ~ 1mm, bottom 3 cm contains ostracods GR09FBFB-S018 Light orange tuff, weathers a rusty orange, fine grained, well indurated "K-spar tuff" GR09FBFB-S019 Light tan kerogen poor laminated micrite, weathers buff, some siliciclastic layers, laminations ~ 1 mm, ostracodes, gastropods, and fish present GR09FBFB-S020 Light brown laminated dolomicrite, weathers buff, laminations present are 2-3 mm, well indurated, ostracodes present GR09FBFB-S021 Tan siltstone, weathers light orange tan GR09FBFB-S022 Light brown tuff, weathers to dark brown to dark gray, very fine grained, well indurated, laminations present ranging from < 1 mm to 1 mm GR09FBFB-S023 Brown dolomicrite, weathers to dark gray, laminations ~ 1 mm, muddy, larger dolomite crystals present GR09FBFB-S024 Dark brown tuff, weathers to light brown, fine grained with coarse grains of quartz present, friable, primary ash 1.5-5 cm thick on bottom, reworked ash 20 cm thick in middle, primary ash again 2.5 cm thick on top GR09FBFB-S025 Dark brown kerogen rich microlaminated micrite, weathers to light tan and dark gray, soft sediment deformation, alternating light and dark laminations GR09FBFB-S026 Red/brown laminated siltstone, weathers to light tan, coarse grained, calcareous cement, soft sediment deformation GR09FBFB-S027 Red/brown fine grained sandstone, weathers to light tan, calcareous cement, soft sediment deformation GR09FBFB-S028 Tan siltstone, weathers light orange tan GR09FBFB-S029 Light gray dolomicrite, weathers to pale gray/green, some rust colored clasts GR09FBFB-S030 Orange to green/gray tuff, weathers to light tan, fine grained with coarser grains throughout, moderately indurated GR09FBFB-S031 Dark brown dolomicrite, weathers to tan, reworked ash containing large crystals of quartz present, moderately indurated GR09FBFB-S032 Golden yellow volcaniclastic sandstone, weathers to light creamy orange, very fine grained, no apparent bedding, 3 cm thick ash layer at top GR09FBFB-S033 Dark brown to dark gray microlaminated dolomicrite, weathers to blue gray/light reddish brown, thickness variable, well indurated GR09FBFB-S034 Gray kerogen rich laminated micrite, weathers light gray GR09FBFB-S035 Gray dolomicrtite, weathers to a pale yellow, structureless, rust colored staining, well indurated 39 GR09FBFB-S036 Pale yellow tuff, weathers to white, poorly indurated, chunks of calcareous mud present GR09FBFB-S037 Golden yellow siltstone, weathers to pale yellow with a red rind GR09FBFB-S038 Light gray to pale yellow tuff, weathers darker yellow, very fine grained, well indurated GR09FBFB-S039 Peach dolomicrite, weathers to dark reddish tan, minor lamina tions, well indurated GR09FBFB-S040 Pale yellow to brown laminated micrite weathers white to light brown moderately well indurated, upper part contains alternating light gray and brown laminations GR09FBFB-S041 Gray tuff, weathers golden yellow, very fine grained, well indurated, unit also interbedded with ashes and siliciclastic sandstones GR09FBFB-S042 Brown kerogen rich dolomicrite, weathers to light blue/gray, some layers with coarser grained calcite crystals, oily smell, "Purple Oil Shale" GR09FBFB-S043 Light gray dolomicrite, weathers to light tan with pale green, with rust colored flecks GR09FBFB-S044 Pale orange tuff, weathers orange, fine grained, laminated, moderately well indurated GR09FBFB-S045 Light gray laminated dolomicrite, weathers light brown to pale yellow, laminations are greater than 1mm GR09FBFB-S046 Blue gray kerogen rich dolomicrite, muddy, no apparent bedding, "Blue Oil Shale" GR09FBFB-S047 White to light cream kerogen poor dolomicrite, weathers to yellow/ orange, weakly laminated, "White Marker Bed" GR09FBFB-S048 Light green kerogen rich dolomicrite, weathers to dark gray with some rust coloration, structureless, grain supported GR09FBFB-S049 Light cream kerogen poor microlaminated micrite, weathers to yellower cream, laminations < 1 mm, 3 cm thick light orange very fine grained tuff within layer, fish, ostracodes, and gastropods present "Gastropod Layer" GR09FBFB-S050 Light gray kerogen rich laminated micrite, weathers orange tan to dark gray to dark rust color, laminations > 1 mm, well indurated GR09FBFB-S051 Light gray to white kerogen poor microlaminated dolomicrite, weathers to light tan, laminations < 1 mm, mud supported, salt casts present GR09FBFB-S052 White to light tan tuff, weathers orange, very fine grained, well indurated GR09FBFB-S053 Light gray to very light green dolomicrite, structureless, blocky weathering, mud supported, well indurated, light gray-tan tuff located at 30-35 cm from base of unit GR09FBFB-S054 Yellow dolomicrite, weathers to pale yellow-light tan, structureless, grain supported, well indurated GR09FBFB-S055 Gray dolomicrite, weathers gray to light tan, weakly laminated, laminations < 1 mm GR09FBFB-S056 Brown kerogen poor laminated micrite, weathers light tan, laminations < 1 mm, well indurated

40 Road Hollow

GR09RH-S012 Light brown structureless micrite, weathers to light tan, well indurated GR09RH-S013 Light gray mudstone, weathers to dark gray/green, calcareous cement GR09RH-S014 Light gray kerogen poor structureless micrite, weathers to dark gray GR09RH-S015 Light cream kerogen poor structureless micrite, weathers to light gray, mud supported GR09RH-S016 Light gray kerogen poor laminated micrite, weathers to tan, laminations > 1 mm, mud supported GR09RH-S017 Dark gray to green structureless micrite, weathers to light gray GR09RH-S018 Light gray/green kerogen poor microlaminated micrite, weathers to light tan, laminations < 1 mm, mud supported GR09RH-S019 Light brown kerogen poor structureless micrite, weathers to light tan, structureless, mud supported GR09RH-S020 Light brown fine grained sandstone, weathers dark tan, laminated, calcareous cement GR09RH-021 Light brown kerogen poor microlaminated micrite, weathers to light gray, bioturbated GR09RH-022 Tan structureless micrite, weathers light cream GR09RH-S023 Light tan dolomicrite, weathers to light gray, laminated and bioturbated GR09RH-S024 Green kerogen rich structureless micrite, weathers to light gray, possibly reduced GR09RH-S025 Chocolate brown kerogen rich microlaminated micrite, weathers to light brown, very fissile GR09RH-S026 Light tan kerogen poor dolomicrite, weathers to light gray, mud supported GR09RH-S027A Brown kerogen rich laminated micrite, brown fresh, weathers to light tan, bioturbated GR09RH-S027B Rusty tan kerogen poor microlaminated micrite, weathers to light tan GR09RH-S027C Light cream kerogen rich structureless micrite, weathers to tan, bioturbated GR09RH-S027D Green/gray fine grained flaggy sandstone, weathers brown GR09RH-S027E Chocolate brown kerogen rich microlaminated micrite, weathers to light brown, GR09RH-S028 light tan dolomicrite, weathers to dark tan, structureless, grain supported GR09RH-S029A Light tan kerogen poor structureless micrite, weathers to light cream, structureless GR09RH-S029B Green/gray kerogen rich structureless micrite, weathers to light tan GR09RH-S029C Light gray kerogen poor laminated micrite, weathers to lighter gray GR09RH-S030 Tan fine grained tuff, weathers to buff GR09RH-S031A Chocolate brown kerogen rich microlaminated micrite, weathers light tan, microlaminations < 1 mm, ostracodes present GR09RH-S031B Light cream dolomicrite, weathers to light tan, bioturbated, mud supported, ash and 1 cm of silt 3 cm from bottom GR09RH-S032A Light brown kerogen poor laminated micrite, weathers to light tan 41 GR09RH-S032B Light brown siltstone GR09RH-S032C Interbedded tan kerogen rich laminated micrite and dolomicrite GR09RH-S033 Light brown siltstone, heavily boturbated and interbedded with silt and fine grained sandstone, coarsening upward GR09RH-S034 Light gray tan sandstone, weathers light tan, 90% quartz, 10% others (black mineral-tourmaline?), subangular, moderately-well sorted, calcarious cement, very weakly bedded GR09RH-S035A Gray tan kerogen rich structureless micrite, weathers light brown GR09RH-S035B Light tan kerogen poor microlaminated micrite, weathers light yellow-tan, laminations < 1 mm GR09RH-S035C Gray kerogen rich laminated micrite, weathers light gray-tan, laminations > 1 mm GR09RH-S035D Light blue gray kerogen rich laminated micrite GR09RH-S036 Light gray tan sandstone, weathers light tan, 80% quartz, 15% feldspar, 5% others, subangular, moderately-well sorted, very weakly bedded GR09RH-S037 Light tan sandstone, weathers light yellow-tan, 90% quartz, 10% others , subangular, moderately-well sorted, calcarious cement, very weakly bedded

42 Bear River Gulch

GR09BRG-S002A Light cream kerogen poor laminated micrite, mud supported GR09BRG-S002B Light cream kerogen poor bioturbated micrite, weathers to yellow orange, ostracods present GR09BRG-S002C Light tan kerogen poor structureless micrite, weathers yellow orange, mud supported, ostracods present GR09BRG-S002D Light gray tan kerogen poor laminated micrite, weathers to light yellow tan GR09BRG-S002E Light brown kerogen rich structureless micrite, weathers to tan/gray GR09BRG-S002F Light tan kerogen poor structureless micrite, weathers light cream, ostracods present GR09BRG-S002G Light cream dolomicrite, structureless, mud supported GR09BRG-S002H Light gray tan kerogen poor structureless micrite, weathers to yellow tan, mud supported GR09BRG-S002I Light cream dolomicrite, weathers to light brown GR09BRG-S002J Light cream kerogen poor structureless micrite, weathers a rusty tan, bioturbated, mud supported, plant material present GR09BRG-S002K Light cream dolomicrite, weathers to light tan, mud supported, structureless GR09BRG-S002L Light tan kerogen poor laminated micrite, weathers to gray tan, some green coloration, mud supported, minor calcite veins GR09BRG-S002M Light tan dolomicrite, weathers to light cream, structureless, mud supported GR09BRG-S002N Light cream kerogen poor laminated micrite, weathers light tan, laminations > 1 mm, mud supported GR09BRG-S003A Light cream dolomicrite, structureless, mud supported GR09BRG-S003B Light cream kerogen poor laminated micrite, weathers to light brown, mud supported, fish present GR09BRG-S004 Light cream kerogen poor structureless micrite GR09BRG-S005 Light gray kerogen poor laminated micrite, weathers to light yellow/tan, laminations > 1 mm, ostracods present GR09BRG-S006 Light cream dolomicrite, weathers to brown/gray, structureless, interbedded organic layers, mud supported GR09BRG-S007 Light cream siltstone, weathers to cream/yellow, structureless, calcareous cement GR09BRG-S008 Creamy yellow kerogen poor structureless micrite, weathers to gray/brown, bioturbated GR09BRG-S009 Creamy yellow dolomicrite, weathers to gray/brown, bioturbated GR09BRG-S010 Light cream/yellow kerogen poor structureless micrite, weathers to rusty orange in spots and gray brown, bioturbated, ostracodes present GR09BRG-S011 Light purple gray kerogen poor laminated micrite, weathers to pale yellow, interbedded, laminated, friable GR09BRG-S012 Light cream kerogen poor structureless micrite, mud-supported GR09BRG-S013 Chocolate brown kerogen rich microlaminated micrite, weathers light tan, mud-supported GR09BRG-S014 Light cream kerogen poor microlaminated micrite, weathers light gray-tan, laminations < 1 mm and alternating light cream and light orange, ostracodes present 43 GR09BRG-S015 Chocolate brown kerogen rich microlaminated micrite, weathers light tan, mud-supported GR09BRG-S016 Light gray kerogen poor laminated micrite, weathers light creamy yellow, laminations are 1mm and alternate between light gray and light orange GR09BRG-S017 Light tan microlaminated dolomicrite, weathers to light cream, alternating rust color bands GR09BRG-S018 Light gray kerogen poor microlaminated micrite, weathers to light tan and rusty orange GR09BRG-S019 Green kerogen rich structureless micrite, weathers to light tan GR09BRG-S020 Light gray dolomicrite, weathers light tan, mud supported, burrows and ostracodes present GR09BRG-S021 Light tan kerogen poor structureless micrite, weathers to light cream GR09BRG-S022 Light gray dolomicrite, weathers to light tan GR09BRG-S023 Light gray kerogen poor structureless micrite, weathers to light tan GR09BRG-S024 Light gray dolomicrite, weathers to light tan GR09BRG-S025 Light gray kerogen poor laminated micrite, weathers to light tan laminations > 1 mm, some bioturbation GR09BRG-S026 Chocolate brown kerogen rich microlaminated micrite, weathers to light brown, laminations < 1 mm GR09BRG-S027 Light gray kerogen poor structureless micrite, weathers light tan, some microlaminations present < 1 mm GR09BRG-S028A Light gray-tan dolomicrite, weathers light yellow-tan, weakly laminated GR09 BRG-S029 Light cream kerogen poor structureless micrite, weathers to light tan

44 appendix B Ostracode Data ) 2 SMITH Density Species Presence / HOLLOW (ostracodes/ Absence QUARRY lowest cm2 Ostracodes Area (cm sampled) Fish Ostracodes GR09FBFB- 154 10 38.5 Hemicyprinotus 1 1 S1001:00-10 CM watsonensis GR09FBFB- 0 0 < 0.25 1 0 S1001:10-20 CM GR09FBFB- 2 10 0.5 Hemicyprinotus 1 1 S1001:20-30 CM watsonensis GR09FBFB- 0 0 < 0.25 1 0 S1001:30-40 CM GR09FBFB- 0 0 < 0.25 1 0 S1001:40-50 CM GR09FBFB- 0 0 < 0.25 1 0 S1001:50-60 CM GR09FBFB- 0 0 < 0.25 1 0 S1001:60-70 CM GR09FBFB- 0 0 < 0.25 1 0 S1001:70-80 CM GR09FBFB- 0 0 < 0.25 1 0 S1001:80-90 CM GR09FBFB- 0 0 < 0.25 1 0 S1001:90-100 CM GR09FBFB- 0 0 < 0.25 0 0 S1002

45 )

SMITH 2 HOLLOW Density Species Presence / QUARRY (ostracodes/ Absence lowest cm2 Ostracodes Area (cm sampled) Fish Ostracodes GR09FBFB- 0 0 < 0.25 1 0 S001 GR09FBFB- 0 0 < 0.25 0 0 S002 GR09FBFB- 0 0 < 0.25 0 0 S003 GR09FBFB- 0 0 < 0.25 0 0 S004 GR09FBFB- 0 0 < 0.25 0 0 S005 GR09FBFB- 0 0 < 0.25 0 0 S006 GR09FBFB- 0 0 < 0.25 0 0 S007 GR09FBFB- 0 0 < 0.25 1 0 S008 GR09FBFB- 0 0 < 0.25 0 0 S009 GR09FBFB- 0 0 < 0.25 0 0 S010 GR09FBFB- 0 0 < 0.25 0 0 S011 GR09FBFB- 0 0 < 0.25 0 0 S012 GR09FBFB- 0 0 < 0.25 0 0 S013 GR09FBFB- 0 0 < 0.25 0 0 S014 GR09FBFB- 0 0 < 0.25 0 0 S015

46 ) 2 SMITH Density Species Presence / HOLLOW (ostracodes/ Absence QUARRY lowest cm2 Ostracodes Area (cm sampled) Fish Ostracodes GR09FBFB- 0 0 < 0.25 0 0 S016 GR09FBFB- 3 37.5 0.75 Hemicyprinotus 0 1 S017A watsonensis GR09FBFB- 341 14.5 85.25 Hemicyprinotus 0 1 S017B watsonensis GR09FBFB- 0 0 < 0.25 0 0 S017C GR09FBFB- 0 0 < 0.25 1 0 S018 GR09FBFB- 12 73 3 Candona pagei 0 1 S019 GR09FBFB- 25 72.5 6.25 Candona pagei 1 1 S020 GR09FBFB- 0 0 < 0.25 0 0 S021 GR09FBFB- 0 0 < 0.25 0 0 S022 GR09FBFB- 0 0 < 0.25 0 0 S023 GR09FBFB- 0 0 < 0.25 0 0 S024 GR09FBFB- 0 0 < 0.25 0 0 S025 GR09FBFB- 0 0 < 0.25 0 0 S026 GR09FBFB- 0 0 < 0.25 0 0 S027 GR09FBFB- 0 0 < 0.25 0 0 S028

47 ) 2 SMITH Density Species Presence / HOLLOW (ostracodes/ Absence QUARRY lowest cm2 Ostracodes Area (cm sampled) Fish Ostracodes GR09FBFB- 0 0 < 0.25 0 0 S029 GR09FBFB- 0 0 < 0.25 0 0 S030 GR09FBFB- 0 0 < 0.25 0 0 S031 GR09FBFB- 0 0 < 0.25 0 0 S032 GR09FBFB- 0 0 < 0.25 0 0 S033 GR09FBFB- 0 0 < 0.25 0 0 S034 GR09FBFB- 0 0 < 0.25 0 0 S035 GR09FBFB- 0 0 < 0.25 0 0 S036 GR09FBFB- 0 0 < 0.25 0 0 S037 GR09FBFB- 0 0 < 0.25 0 0 S038 GR09FBFB- 0 0 < 0.25 0 0 S039 GR09FBFB- 0 0 < 0.25 0 0 S040:LOWER GR09FBFB- 0 0 < 0.25 0 0 S040:UPPER GR09FBFB- 0 0 < 0.25 0 0 S041 GR09FBFB- 0 0 < 0.25 0 0 S042

48 ) 2 SMITH Density Species Presence / HOLLOW (ostracodes/ Absence QUARRY lowest cm2 Ostracodes Area (cm sampled) Fish Ostracodes GR09FBFB- 0 0 < 0.25 0 0 S043 GR09FBFB- 0 0 < 0.25 0 0 S044 GR09FBFB- 0 0 < 0.25 0 0 S045 GR09FBFB- 0 0 < 0.25 0 0 S046 GR09FBFB- 0 0 < 0.25 0 0 S047 GR09FBFB- 0 0 < 0.25 0 0 S048 GR09FBFB- 32 15 8 Candona pagei 1 1 S049A GR09FBFB- 0 0 < 0.25 0 0 S049B GR09FBFB- 0 0 < 0.25 0 0 S050 GR09FBFB- 0 0 < 0.25 0 0 S051 GR09FBFB- 0 0 < 0.25 0 0 S052 GR09FBFB- 0 0 < 0.25 0 0 S053A GR09FBFB- 0 0 < 0.25 0 0 S053B GR09FBFB- 0 0 < 0.25 0 0 S053C GR09FBFB- 0 0 < 0.25 0 0 S054

49 )

SMITH 2 HOLLOW Density Species Presence / QUARRY (ostracodes/ Absence lowest cm2 Ostracodes Area (cm sampled) Fish Ostracodes GR09FBFB- 0 0 < 0.25 0 0 S055 GR09FBFB- 0 0 < 0.25 0 0 S056

50 ) 2 ROAD Density Species Presence / HOLLOW (ostracodes/ Absence lowest cm2 Ostracodes Area (cm sampled) Fish Ostracodes GR09RH-012 0 < 0.25 0 0 GR09RH-013 0 < 0.25 0 0 GR09RH-014 0 < 0.25 0 0 GR09RH-015 0 < 0.25 0 0 GR09RH-016 0 < 0.25 0 0 GR09RH-017 0 < 0.25 0 0 GR09RH-018 0 < 0.25 0 0 GR09RH-019 6 19.5 1.5 Candona pagei 0 1 GR09RH-020 0 < 0.25 0 0 GR09RH-021 0 < 0.25 0 0 GR09RH-022 0 < 0.25 0 0 GR09RH-023 0 < 0.25 0 0 GR09RH-024A 0 < 0.25 0 0 GR09RH-024B 0 < 0.25 0 0 GR09RH-025A 0 < 0.25 0 0 GR09RH-025B 0 < 0.25 0 0 GR09RH-026 0 < 0.25 0 0 GR09RH-027A 0 < 0.25 0 0 GR09RH-027B 0 < 0.25 1 0 GR09RH-027C 0 < 0.25 0 0 GR09RH-027D 0 < 0.25 0 0 GR09RH-027E 506 10 126.5 Hemicyprinotus 0 1 watsonensis GR09RH-028 0 < 0.25 0 0 51 ) ROAD 2 Density Species Presence / HOLLOW (ostracodes/ Absence lowest cm2

Ostracodes sampled) Fish Ostracodes Area (cm GR09RH-029A 0 < 0.25 0 0

GR09RH-029B 0 < 0.25 0 0 GR09RH-029C 0 < 0.25 0 0 GR09RH-030 0 < 0.25 0 0 GR09RH-031A 169 12 42.25 Hemicyprinotus 0 1 watsonensis GR09RH-031B 0 < 0.25 0 0 GR09RH-032A 0 < 0.25 0 0 GR09RH-032B 0 < 0.25 0 0 GR09RH-032C 0 < 0.25 0 0 GR09RH-033 0 < 0.25 0 0 GR09RH-034 0 < 0.25 0 0 GR09RH-035A 0 < 0.25 0 0 GR09RH-035B 0 < 0.25 0 0 GR09RH-035C 0 < 0.25 0 0 GR09RH-035D 0 < 0.25 0 0 GR09RH-036 0 < 0.25 0 0 GR09RH-037 0 < 0.25 0 0

52 ) 2 BEAR Density Species Presence / RIVER (ostracodes/ Absence GULCH lowest cm2 Ostracodes Area (cm sampled) Fish Ostracodes GR09BRG- 0 < 0.25 0 0 S002A GR09BRG- 0 < 0.25 0 0 S002B GR09BRG- 16 9 4 Candona 0 1 S002C pagei GR09BRG- 0 < 0.25 0 0 S002D GR09BRG- 0 < 0.25 0 0 S002E GR09BRG- 17 5.5 4.25 Candona 0 1 S002F pagei GR09BRG- 0 < 0.25 0 0 S002G GR09BRG- 0 < 0.25 0 0 S002H GR09BRG- 0 < 0.25 0 0 S002I GR09BRG- 1 4 0.25 Candona 0 1 S002J pagei GR09BRG- 0 < 0.25 0 0 S002K GR09BRG- 2 29 0.5 Candona 0 1 S002L pagei GR09BRG- 0 < 0.25 0 0 S002M GR09BRG- 0 < 0.25 0 0 S002N GR09BRG- 0 < 0.25 0 0 S003A

53 ) 2 BEAR Density Species Presence / RIVER (ostracodes/ Absence GULCH lowest cm2 Ostracodes Area (cm sampled) Fish Ostracodes GR09BRG- 0 < 0.25 1 0 S003B GR09BRG- 0 < 0.25 0 0 S004 GR09BRG- 0 < 0.25 0 0 S005 GR09BRG- 0 < 0.25 0 0 S006 GR09BRG- 0 < 0.25 0 0 S007 GR09BRG- 0 < 0.25 0 0 S008 GR09BRG- 0 < 0.25 0 0 S009 GR09BRG- 0 < 0.25 0 0 S010 GR09BRG- 0 < 0.25 0 0 S011 GR09BRG- 0 < 0.25 0 0 S012 GR09BRG- 0 < 0.25 0 0 S013 GR09BRG- 0 < 0.25 0 0 S014 GR09BRG- 0 < 0.25 0 0 S015 GR09BRG- 0 < 0.25 0 0 S016 GR09BRG- 0 < 0.25 0 0 S017

54 ) 2 BEAR Density Species Presence / RIVER (ostracodes/ Absence GULCH lowest cm2 Ostracodes Area (cm sampled) Fish Ostracodes GR09BRG- 0 < 0.25 0 0 S018 GR09BRG- 0 < 0.25 0 0 S019 GR09BRG- 0 < 0.25 0 0 S020 GR09BRG- 0 < 0.25 0 0 S021 GR09BRG- 0 < 0.25 0 0 S022 GR09BRG- 0 < 0.25 0 0 S023 GR09BRG- 0 < 0.25 0 0 S024 GR09BRG- 0 < 0.25 0 0 S025 GR09BRG- 0 < 0.25 0 0 S026 GR09BRG- 0 < 0.25 0 0 S027 GR09BRG- 2 20 0.5 Candona 0 1 S028 pagei GR09BRG- 64 18.5 16 Candona 0 1 S029 pagei

55 appendix c Lamination counts -

Sample Unit Thickness (m) Lamination Counts Thick Sample ness (mm) Count/ thickness(mm) Possible years represented

S1001-1 1.00 425.00 20.00 21.25 212.50 Light brown to brown kerogen- poor microlaminated micrite, weathers to light tan, laminations range from 0.5 mm to 1 mm thick, fish, coprolites, and ostracodes present, phosphatic deposits S1001-2 1.00 356.00 16.00 22.25 178.00 Dark brown tuff, weathers to yellow-tan and orange, very fine grained, well indurated S007-1 0.80 89.00 5.00 17.80 44.50 Dark brown to dark gray kerogen-rich laminated micrite, weathers to light tan, laminations range from 0.5 mm to 2 mm, oily smell S007-2 0.80 84.00 3.17 26.50 42.00 Dark brown to dark gray kerogen-rich laminated micrite, weathers to light tan, laminations range from 0.5 mm to 2 mm, oily smell S010 0.43 402.00 20.00 20.10 201.00 Light tan/dark brown kerogen- rich microlaminated micrite, weathers to buff and light gray, laminations alternate between light tan and dark brown

56 S040-1 0.90 35.00 15.00 2.33 17.50 Pale yellow to brown laminated micrite weathers white to light brown, moderately well indurated, upper part contains alternating light gray and brown laminations S040-2 0.90 53.00 15.00 3.53 26.50 Pale yellow to brown laminated micrite weathers white to light brown moderately well indurated, upper part contains alternating light gray and brown laminations

57