Open VF MS Thesis Final.Pdf

The Pennsylvania State University

The Graduate School

College of Earth and Mineral Sciences

OCEANIC ANOXIA EVENT 2 (93.9 MA) IN THE U.S. WESTERN INTERIOR

SEAWAY: HIGH RESOLUTION CALCAREOUS NANNOFOSSIL RECORD OF THE

TROPIC SHALE FORMATION

A Thesis in

Geosciences

Victoria Fortiz

Submitted in Partial Fulfillment of the Requirements for the Degree of

Master of Science

December 2017 The thesis of Victoria Fortiz was reviewed and approved* by the following:

Timothy J. Bralower Professor of Geosciences and Interim Head of the Department of Geosciences Thesis Adviser

Michael A. Arthur Professor of Geosciences

Mark E. Patzkowsky Professor of Geosciences

Demian Saffer Professor of Geosciences and Associate Head for Graduate Programs and Research

*Signatures are on file in the Graduate School

ABSTRACT

OCEANIC ANOXIA EVENT 2 (93.9 MA) IN THE U.S. WESTERN INTERIOR SEAWAY: HIGH RESOLUTION CALCAREOUS NANNOFOSSIL RECORD OF THE TROPIC SHALE FORMATION December 2017 Victoria Fortiz, B.S., University of Texas at Austin M.S., The Pennsylvania State University Advised by: Timothy J. Bralower

Oceanic Anoxia Event 2 (OAE2) occurred at the Cenomanian/Turonian Boundary

(CTB; 93.9 MA) and had a duration of < 1 m.y.. This event involved the global deposition of organic carbon rich sediments, a distinctive positive shift in carbon isotope values, and significant species turnover, including changes in calcareous nannofossil assemblages. Organic C-rich sediment deposition is thought to have been triggered by volcanism that led to increased productivity and/or enhanced organic matter preservation. The temporal succession of volcanism, organic matter deposition, and changes in biota such as nannofossils, is crucial to understanding the dynamics of these major environmental perturbations during OAE2.

Calcareous nannofossil assemblages during OAE2 in the WIS are marked by large shifts between taxa with eutrophic and oligotrophic affinities. Assemblages have the potential to qualitatively assess changes in nutrient and surface-ocean temperature conditions during OAE2. Here we study nannoplankton in an expanded section of the

Tropic Shale in southern Utah near the western margin of the Western Interior Seaway to assess the relationships between anoxia, organic matter deposition, and planktic biotas during OAE2. Samples were collected from a 30-m section of a core that

iii contains well preserved nannoplankton. Relative abundance data are complemented with Total Organic Carbon and Carbonate values to determine whether organic rich sediments were a response to high surface ocean fertility or water column stratification.

Paleoecological/paleoceanographic interpretations of calcareous nannofossil assemblage change in this study suggest warm and oligotrophic conditions at the base of OAE2. Gradually, surface ocean conditions at the western margin cool and become eutrophic towards the end of the event as suggested by the increase in B. constans and

Zygodiscus spp. Results from this study along with those from the Rebecca Bounds and

Portland Core suggest a counterclockwise circulation of Tethyan and Boreal waters as modeled by Slingerland et al. (1996) in the WIS during the late transgression phase of the latest Cenomanian to early Turonian.

TABLE OF CONTENTS

Page

LIST OF TABLES………………………………………………..………………………….....vii

LIST OF FIGURES…………..………………………………………………………………..viii

LIST OF SUPPLEMENTARY FIGURES……………………………………………………...x

ACKNOWLEDGEMENTS………………………………………………………………...... xi

CHAPTER

1. CLIMATIC AND BIOTIC EVENTS OF THE LATE CRETACEOUS………………….....1

1.1 Introduction………………………………………………………………………….1

2. GEOLOGIC SETTING……………………………………………………………………….5

2.1 Study Area: U.S. Western Interior Seaway………………………………………5 2.2 Study Chronostratigraphy………………………………………………………….8

3. MATERIAL AND METHODS………………………………………………………………11

3.1 Field Methods……………………………………………………………………...11 3.2 Calcareous Nannofossil Methods……..…………………………..…………….11 3.3 Total Carbon, Total Inorganic Carbon and Total Organic Carbon Analysis...13 3.4 Statistical Techniques…………………………………………………………….14

4. RESULTS……………………………………………………………………………………18

4.1 Calcareous Nannofossil Assemblage…………………………………………...18 4.2 Geochemistry………………………………………………………………………19 4.3 Statistical Analysis………………………………………………………………...21

5. DISCUSSION……………………………………………………………………………….28

5.1 Non-ecological Factors: Preservation and the closed-sum effect……...... 28 5.2 Interpretation of calcareous nannofossil assemblages...... ……………………31 5.3 Changes in calcareous nannofossil assemblages during OAE2………………35

6. CONCLUSIONS…………………………………………………………………………….45

APPENDICES

A. TABLES…………………………………………………………………………….47 B. MULTIVARIATE ANALYSIS METHODS………………………………...... 56 C. SUPPLEMENTARY FIGURES…………………………………………………..70

BIBLIOGRAPHY……………………………………………………………………………….80

LIST OF TABLES

Table Page

1. Calcareous Nannofossil Relative Abundance Data………………………………...48

2. Calcareous Nannofossil Paleoecological Affinities…………………………………52

3. Smoky Hollow #1 Core Taxa Correlation Coefficients……………………………...53

4. Smoky Hollow #1 Core Taxa and Geochemistry Correlation Coefficients………..54

5. Smoky Hollow #1 Core Taxa Correlation Coefficients after First Difference…...…55

vii

LIST OF FIGURES

Figure Page

1. Paleogeography of the Late Cretaceous (Late Cenomanian-Early Turonian)

Western Interior Seaway……………………………………………………………….9

2. Chronostratigraphic correlation between southwest Utah and the Cenomanian-

Turonian GSSP in Colorado………………………………………………………….10

3. Stratigraphic column of SH#1 near Big Water, UT with geochemical data……...16

4. Comparison of relative abundance data for SH#1-66-120.250 m……...... 17

5. Relative abundance patterns of calcareous nannofossils in the Cenomanian-

Turonian Boundary from the SH#1 core…………………………………………….24

6. Relative abundance patterns of calcareous nannofossils in the Cenomanian-

Turonian Boundary from the SH#1 core………………………………………….....25

7. SH#1 Species/ Genera Dendrogram……………………………………………...... 26

8. SH#1 Species/ Genera DCA………………………………….……………………...27

9. Relative abundance of eutrophic and cool water taxa plotted alongside

oligotrophic and warm water taxa for SH#1 Core……………………………….....40

10. Heatmap of Pearson correlation coefficients between calcareous nannofossil

taxa for SH#1…………………………………………………………………………..41

11. Comparison of the relative abundance of W. barnesae for the SH#1, Portland

(PO) and Bounds (BO) Cores throughout the Cenomanian-Turonian Boundary

during OAE2……………………………………………………………………………42

viii

12. Comparison of the relative abundance of Zygodiscus spp. for the SH#1, Portland

(PO) and Bounds (BO) Cores throughout the Cenomanian-Turonian Boundary

during OAE2……………………………………………………………………………43

13. Comparison of the relative abundance of B. constans for the SH#1, Portland

(PO) and Bounds (BO) Cores throughout the Cenomanian-Turonian Boundary

during OAE2……………………………………………………………………………44

LIST OF SUPPLEMENTARY FIGURES

Figure Page

S1. SH#1 calcareous nannofossil assemblage sampling resolution………………...71

S2. SH#1 %Carbonate and relative abundance of C. margerelii (%)

comparison…………………………………………………………………………….72

S3. NU and PSU %TOC and %Carbonate comparison……………………………….73

S4. Pyrite Framboid abundance in the Cenomanian-Turonian interval of the SH#1

core……………………………………………………………………………………..74

S5. DCA of calcareous nannofossil samples across OAE2 for the SH#1 core……..75

S6. DCA of calcareous nannofossil samples coded by age across OAE2 for the

SH#1 core……………………………………………………………………………..76

S7. DCA of calcareous nannofossil species and genera across OAE2 for the SH#1

core overlain by environmental vectors…………………………………………….77

S8. DCA of calcareous nannofossil samples across OAE2 for the SH#1 core

overlain by environmental vectors…………………………………………………..78

13 S9. δ Corg records for SH#1, Portland (PO), and Bounds (BO) Cores used to

correlate between sections…………………………………………………………..79

ACKNOWLEDGMENTS

I would like to thank my advisor, Tim Bralower, for his guidance and support throughout this project and my time at PSU. To my lab mates, Rosie, Heather, and

Ashley, thank you for making the lab a great place for discussion and peer mentorship/ support. I would also like to thank the members of my committee, Mike Arthur and Mark

Patzkowsky, for their helpful comments and suggestions during this project.

I want to thank the National Science Foundation and the Pennsylvania State

University Department of Geosciences for funding and supporting this research. I wish to express my gratitude to all collaborators in the NSF-ELT grant. I would like to thank

Matt Jones and Brad Sageman for their geochemical contributions to this project and for providing additional samples. I would also like to thank Amanda Parker and Mark Leckie for their foraminiferal record contribution to this project. Special thanks to Scott Karduck,

Aileen McNamee, and Cheng Tarng for helping prepare and collect geochemical results.

A special thank you to my family for their unconditional support and love during the last two years. Finally, I would like to thank Steve Cantu for his love, support, and patience.

CHAPTER 1

CLIMATIC AND BIOTIC EVENTS OF THE LATE CRETACEOUS

1.1 Introduction

The Cenomanian-Turonian Boundary (93.9 Ma) was characterized by abrupt warming and the deposition of organic C-rich sediments on a global basis. Oceanic

Anoxic Event 2 (OAE2) corresponded to deep-water temperatures ~19°C (Huber et al.,

2002), pCO2 ~3-5 times preindustrial levels (Barclay et al., 2010; Jarvis et al., 2011), high seafloor spreading rates (Arthur et al., 1985; Larson, 1991; Seton et al., 2009) and peak transgression (Kauffman, 1977; Haq et al., 1987; Gale et al., 2008). Extensive volcanism is thought to have triggered the climatic and biogeochemical perturbations at

OAE2 (Arthur et al., 1985; Larson, 1991; Turgeon & Creaser, 2008; Seton et al., 2009).

Elevated CO2 input into the atmosphere from volcanic sources caused increased terrestrial weathering and nutrient input from rivers, weakened ocean circulation, water column stratification, and decreased oxygen levels in bottom ocean waters ( Schlanger

& Jenkyns, 1976; Arthur et al., 1987; Burns & Bralower, 1998; Leckie et al., 1998;

Leckie et al., 2002; Eleson & Bralower, 2005). These changes led to deposition of organic C-rich sediments for a period of ~0.5 Ma on a global basis. OAE2 is characterized by a positive carbon isotope excursion (CIE) measured in bulk organic

13 13 carbon (δ Corg) and bulk carbonate (δ Ccarb), presumably as a result of the burial of isotopically light carbon (Jenkyns, 2010; Scholle & Arthur, 1980). By comparison, the event is associated with highly variable changes (~1-30%) in percent total organic carbon (TOC) in a wide range of settings, from broad rises and plateaus in the Pacific, the Tethyan continental margins, and the shallow shelf of northeastern Europe

(Schlanger & Jenkyns, 1976). The event has significant potential in informing us about possible future responses to anthropogenically induced climate and environmental change, including ocean acidification and hypoxia in coastal environments.

The Cenomanian-Turonian Boundary (CTB) is also marked by a local mass extinction event in the Western Interior Seaway (WIS) including ammonites (93% extinction), semi-infaunal and boring bivalves (90% extinction), and gastropods (84% extinction) (Raup & Sepkoski, 1982; Elder, 1989, 1991; Harries & Little, 1999).

Calcareous nannoplankton turnover rates increased at the CTB, but only rare species went extinct (Watkins, 1985; Bralower, 1988; Leckie et al., 2002). The relationship between the extinction and turnover of marine organisms and ocean anoxia is not well understood.

Two possible mechanisms, alone or in concert, explain the deposition of organic

C-rich sediments during OAE2: increased productivity and/or increased water-column stratification and preservation (Watkins, 1989; Burns & Bralower, 1998; Arthur &

Sageman, 2005; Eleson & Bralower, 2005; Meyers, Sageman, & Lyons, 2005; P.

Hardas & Mutterlose, 2007; Mort et al., 2007; Turgeon & Creaser, 2008; Elderbak &

Leckie, 2016). Increased productivity could have resulted from the rapid influx of micronutrients from hydrothermal activity associated with large igneous province eruption, and increased seafloor spreading rates (Kerr, 1998; Leckie et al., 2002; Snow et al., 2005; Turgeon & Creaser, 2008; Barclay et al., 2010). Alternatively, elevated productivity could have been caused by runoff of nutrients resulting from increased hydrologic cycling and continental weathering (Arthur et al., 1987; Leckie et al., 2002;

Arthur & Sageman, 2005; Sageman et al., 2006; Van Helmond et al., 2014). Increased

2 water column stratification is a potential response to warming and changes in water density as the sources of surface waters shifted from Boreal to Tethyan during OAE2

(Arthur et al., 1987; Burns & Bralower, 1998; Leckie et al., 2002; Erba, 2004; Eleson &

Bralower, 2005; P. Hardas & Mutterlose, 2007; Jenkyns, 2010; Corbett & Watkins,

2013; Elderbak & Leckie, 2016).

The Tropic Shale formation lies near the western edge of the Western Interior

Seaway. Due to its proximal location, its record of the global signal of OAE2 is heavily influenced by regional changes in water mass stratification and mixing, increased productivity due to fluvial input, changes in relative sea level and ocean circulation, benthic ventilation, and changes in dominant surface water mass from Tethyan and

Boreal sources (Schlanger & Jenkyns, 1976; Arthur et al., 1987; Burns & Bralower,

1998; Leckie et al., 1998; Leckie et al., 2002; Eleson & Bralower, 2005).

Calcareous nannofossil assemblages during OAE2 in the WIS are marked by large shifts between taxa with eutrophic and oligotrophic affinities (Watkins, 1989; Burns

& Bralower, 1998; Eleson & Bralower, 2005; Corbett & Watkins, 2013; Lowery et al.,

2014). Assemblages have the potential to qualitatively assess changes in nutrient and surface-ocean temperature conditions using known paleocological affinities of taxa (Hill,

1975; Thierstein, 1980; Roth & Krumbach, 1986; Premoli Silva et al., 1989; Roth, 1989;

Watkins, 1989; Erba et al., 1992; Mutterlose & Kessels, 2000; Hardas et al., 2012). This study addresses the response of calcareous nanoplankton assemblages to the paleoclimatic/paleoceanographic perturbations that occurred at the onset and duration of OAE2 along the westernmost margin of the WIS.

The western edge of the WIS is an ideal location for this reconstruction as fossil preservation is excellent and depositional rates are high, readily allowing for high temporal resolution. Our investigation of assemblages is coupled with analyses of percent CaCO3 and TOC, as well as the abundance of pyrite framboids in a continuous core across the CTB. In particular, we are interested in the following questions: 1) What was the response of calcareous nanoplankton assemblages to environmental perturbations during OAE2 in the western prodeltaic shoreline of the WIS? (2) What are the mechanisms that control shifts in nannofossil assemblages? (3) Is there a correlation between calcareous nannofossil assemblages, CaCO3, and TOC that provides information about the mechanisms controlling organic carbon burial? (4)

Finally, what is the nature of water mass and nutrient influx changes suggested by calcareous nannofossil assemblages from this study in combination with data from other sites across the basin?

CHAPTER 2

GEOLOGIC SETTING

2.1 Study Area: U.S. Western Interior Seaway

The Late Cretaceous Western Interior Seaway extended ~5,000 km from the

Arctic Ocean to the Gulf of Mexico and ~1,500 km from Iowa to Utah with an estimated water depth of 100 to 300 m for peak C-T transgression (Kauffman, 1977; Sageman &

Arthur, 1994). The epicontinental seaway connected polar Boreal and subtropical

Tethyan waters. Freshwater influx to the seaway came from the Sevier Highlands to the west, the Mogollon Highlands to the southwest, and from the stable craton to the east.

These fluvial inputs along with shifts in the dominance of Boreal and Tethyan water likely caused major changes in water column structure and circulation patterns

(Watkins, 1986; Fisher et al., 1994; Burns & Bralower, 1998; Leckie et al., 1998).

Circulation patterns may have also been partially restricted in the basin due to bathymetric highs formed during the Sevier Orogeny (Leckie et al., 1998).

The Smoky Hollow drill site is located within the Grand Staircase-Escalante

National Monument on the Kaiparowits Plateau near Big Water, south central Utah

(Figure 1). In this location, the Tropic Shale Formation is ~200-m thick and consists of rhythmically-bedded dark gray, laminated calcareous shale, sandy mudstone and carbonate-rich layers. These cycles likely represent Milankovitch-style orbital forcing of climate and tectonically-induced variations of the foreland basin subsidence (Elder et al., 1994; Meyers et al., 2012b; Meyers et al., 2012a). Sediments of the Tropic Shale

Formation were deposited during the Greenhorn Cyclothem, a large-scale third-order transgressive-regressive cycle, when the WIS was at its maximum western extent

(Kauffman, 1977; Elder et al., 1994). During the Greenhorn Cyclothem transgression the shoreline was pushed further west and coarse-grained fluvial deposits of the Dakota

Formation were replaced by fine-grained mudstones of the Tropic Shale Formation.

The Tropic Shale Formation can be correlated with age equivalent strata across the WIS using several significant bentonite layers (A-D) along with limestone beds (e.g.,

Elder et al. 1994). This interval is represented by the Upper Cenomanian and Lower

Turonian Metoicoceras mosbyense, Sciponoceras gracile, Neocarioceras juddii and

Watinoceras devonense Ammonite Biozones (Elder et al., 1994; Tibert et al., 2003).

The Tropic Shale was deposited in a prodeltaic environment within ~150 km of the western margin of the WIS (Leithold, 1993; Parker, 2016) and overlies the Dakota

Formation, a highly bioturbated marginal marine facies (Schmeisser McKean and

Gillette, 2015). In southern Utah there are six fourth-order depositional sequences in the

Tropic Shale superposed on the third-order transgressive-regressive Greenhorn Cycle

(Leithold, 1994). Superposed on these fourth-order cycles are progradational shoreline deposits attributed to Milankovitch climatic forcing of sediment supply (Elder et al.,

1994). Each fourth-order sequence is bounded by a maximum flooding surface correlated with cyclic sedimentation across the basin (Elder et al., 1994; Leithold, 1994).

The proximal transgressive lags and concretion horizons in Utah correlate with distal limestones in Colorado and Kansas, while progradational sands and silts correlate with the offshore mudrocks and shales (Elder et al., 1994).

Fossils in the Dakota Formation include fish, freshwater sharks, rays, lungfish, lizards, frogs, crocodilians, turtles, dinosaurs, and a diverse therian mammal fauna

(Kirkland, 1987; Eaton, 1993). Calcareous nannofossils are absent in samples of the

Dakota Formation, and, where present, are poorly preserved, therefore unusable for assemblage counts. Tropic Shale Formation faunas are dominated by marine invertebrates such as ammonites, epifaunal bivalves, inoceramids and gastropods

(Pratt et al., 1985; Elder et al., 1994; Schmeisser McKean and Gillette, 2015). Marine vertebrates such as sharks, turtles, bony fish, plesiosaurs, a mosasaur and a dinosaur have also been found in this formation (Albright et al., 2007; Zanno et al., 2009;

Schmeisser McKean, 2012; Albright et al., 2013; Schmeisser et al., 2015). According to

Schmeisser et al. (2015), the marine vertebrates are concentrated in the lower portion of the Tropic Shale Formation. The preservation of these marine vertebrates led

Schmeisser et al. (2015) to interpret the depositional environment as one of low energy with some weak bottom currents and low benthic-oxygen levels.

Foraminifera have been studied in outcrop sections of the Tropic Shale

Formation, KPS1 and KPS2, near Big Water, Utah. A low diversity assemblage with major shifts in abundance of planktic and benthic foraminifera was found in these sections (Parker, 2016). Changes in foraminiferal assemblages suggest low salinity conditions associated with Boreal waters and increased productivity in the early stage of

OAE2, followed by a pulse of Tethyan waters that coincides with rapid and widespread improvement of ventilation associated with transgression. Finally, in the late

Cenomanian and early Turonian productivity increased followed by the incursion of the oxygen-minimum zone to the western margin of the WIS (Parker, 2016).

2.2 Study Chronostratigraphy

The chronostratigraphic framework for this study was set up using macrofossil assemblages and four basinwide bentonite beds, A to D, that provide reliable correlation through the late transgressive phase of the Greenhorn Cycle (Figure 2). Sample ages were calculated using dates of A to D from the USGS #1 Portland Core at Rock

Canyon, CO (Meyers et al., 2012b) assuming linear sedimentation rates (Parker, 2016).

Figure 1. Late Cretaceous paleogeographic reconstruction of the Western Interior Seaway (Ziegler et al., 1987; McCabe and Parrish, 1992). To the west of the shoreline, the Sevier and Mogollan Highlands provided freshwater influx. To the east, a relatively shallow seaway extended from Alaska to Mexico connecting the Boreal Sea and Tethys Ocean (Kauffman, 1977, 1984). Modified from Parker (2016).

asand figures

Turonian GSSP near TuronianGSSP near

D are D Elder from noted (1988,

between southern Utah and Utah southern Cenomanian the between

order relative sea level cycles are recognized across the Colorado across are the sea Colorado recognized cycles level orderrelative

orderand fourth

Figure 2. Chronostratigraphic correlation Figure2. Chronostratigraphic Third Pueblo, Colorado. based wellasParker on (2016), boundary and stage Correlation Plateau1994). (Leithold, Bentonites references). for A studiesdescriptionspublished from figure (see et Parker From al. Meyers (2016). based (2012). 1991). on Ages

CHAPTER 3 MATERIAL AND METHODS

3.1 Field Methods

The Smoky Hollow Drill core (USGS SH#1) was recovered in July 2014, and includes a ~30-m (100 ft.) thick section extending from the Dakota Formation

(Cenomanian) to the Tropic Shale Formation (Turonian) (Figure 3). A second drill core was also recovered, USGS SH#2, but OAE2 was less completely recovered in this core, thus we focused investigation on SH#1. A fresh outcrop section nearby was also measured and described (Parker 2016).

Calcareous nannofossil assemblages were studied in 155 samples from the

Tropic Shale Formation. Sampling resolution generally decreases upcore and is the highest around the onset of OAE2 (Figure S1). Additional sampling was done to constrain peaks in nannofossil assemblage counts. The resolution fluctuates between three intervals:

• Interval # 1 (94.56-104.70 m; 93.97-94.26 Ma): 8 Kyr between samples

• Interval # 2 (104.83-119.00 m; 94.26-94.69 Ma): 5 Kyr between samples

• Interval # 3 (119.45-122.34 m; 94.69-94.78 Ma): 2 Kyr between samples

3.2 Calcareous Nannofossil Methods

In the laboratory, samples were left to disaggregate in water to ensure that nannofossils were not broken apart during slide preparation. More lithified samples were disaggregated by using a mortar and pestle gently (Monechi & Thierstein, 1985). Smear

11 slides were made using standard techniques from well-mixed, unsettled sediment solutions so that the assemblages accurately represent the average composition of samples.

Nannofossil specimens were observed under a Carl Zeiss Axioskop 2 Plus light microscope at a magnification of 1000x and identified using standard taxonomy as described by Perch-Nielsen (1985). Specimens one-half the size of a coccolith or larger were identified and a total of over 31,000 specimens were counted. However, identification at the species level was not always possible due to variation in preservation and taxonomic difficulties. Counts of 100, 200 and 300 specimens were made in different regions of the same smear slide for one sample and show within

10%difference in the dominant taxa (Figure 4). However, 200 specimen counts provide a representative sample of the assemblage. Species richness was determined by counting the number of species in each sample. Pyrite framboid counts were made in 5 vertical traverses of the smear slides.

Although 63 species were identified, only 11 species or groups of species within a genus were chosen for detailed paleoecological analysis. Species/genus groups were removed from analysis if the taxa amounted to less than 1% of the total sample count throughout the core. Some of the species chosen for paleoecological analysis have well established paleoecological affinities, whereas others are not currently well understood.

The paleoecolgical affinity of these taxa is explored through statistical analysis.

Paleoecologic and/or paleoceanographic interpretations are made from the abundances of certain nannofossil taxa. Over the past 30 years, studies have constrained the affinities of species to variations in fertility, temperature and salinity

(Roth and Krumbach, 1986; Premoli Silva et al., 1989; Roth, 1989; Watkins, 1989; Erba et al., 1992). Two of the most commonly accepted affinities are that of Biscutum constans with high surface-water fertility and Watzanaueria barnesae with low surface- water fertility (Thierstein, 1980; Roth and Krumbach, 1986; Premoli Silva et al., 1989;

Roth, 1989; Watkins, 1989; Erba et al., 1992; Burns and Bralower, 1998; Lees, 2002;

Eleson and Bralower, 2005; Linnert and Mutterlose, 2015). Therefore, in moderately to well preserved assemblages, W. barnesae and B. constans negatively correlate (Erba et al., 1992; Williams and Bralower, 1995). Along with these two taxa other species and genus groups such as Zygodiscus spp., Eiffellithus turriseiffelii, Prediscosphaera spp. and Retecapsa spp. are also used to make paleoecological and/or paleoceanographic interpretations (Table 2).

3.3 Total Carbon, Total Inorganic Carbon and Total Organic Carbon Analysis

All samples were powdered and analyzed with a UIC coulometer. Weight percent total carbon (TC) values were obtained by combustion at 950°C in a stream of ultra-high purity oxygen using the UIC CM5200 Autosampler/Furnace. Weight percent total inorganic carbon (TIC) values were obtained by acidification with phosphoric acid using the UIC CM5240 TIC Autoanalyzer. The CO2 liberated by each process was titrated in a coulometer cell to determine TC and TIC (Engleman et al., 1985). Weight percent total organic carbon (TOC) values were obtained by calculating the difference between TC and TIC. Weight percent CaCO3 values were calculated from TIC based on stoichiometry of CaCO3. Carbonate standards, in house standards (Devonian Black

Shale) and blanks were included in every run to calculate the precision of the coulometric analysis.

3.4 Statistical Analysis

The structure of calcareous nannofossil assemblages was investigated using

Cluster Analysis, Detrended Correspondence Analysis (DCA), and Nonmetric

Multidimensional Scaling (NMS). These analyses were performed with the program R

(www.r-project.org) using the “cluster”, “sparcl” and “vegan” packages. Results from

DCA and NMS provided similar outcomes, however, DCA was chosen for interpretation.

Analyses were performed on the core section and at the resolution described in the Field Methods section. Samples are labeled with respect to depth, from 94.56 m -

122.34 m, with taxa names as variables of the main data matrix. The sample attributes data matrix is composed of the variables: Species richness, Pyrite Framboids (count/ 5

13 18 traverses), Total Organic Carbon (%), CaCO3 (%), δ Corg (‰), δ O (‰), Age

(Cenomanian/ Turonian), and Stage (Pre-, During, Post-OAE2). Data were investigated two ways for each type of analysis: using the Q and R-mode in Cluster Analysis and the sites (samples) and species scores in DCA. Transformations, distance measures and methods used for Cluster Analysis and DCA are outlined in Appendix B.

Relative abundance values were used to calculate Pearson’s correlation

13 coefficients for each of the 11 taxa relative to one another and to the δ Corg, TOC,

CaCO3 values and pyrite framboid abundance (Tables 3 & 4). In addition, to test whether changes in nannofossil assemblages were random first difference was applied

14 to relative abundance values. The first difference values for taxa were then used to calculate Pearson’s correlation coefficients for each of the 11 taxa relative to one another (Table 5). Only significant correlations (95-99% confidence interval) are discussed.

Figure 3. Stratigraphic column for SH#1 near Big Water, Utah with geochemical data. The Tropic Shale Formation is mainly composed of calcareous shale and mudstone. The depositional environment of the Tropic Shale Formation is a prodeltaic environment within ~150 km of the western margin of the WIS (Leithold, 1993; Parker, 2016). %TOC and %Carbonate were collected 13 at PSU. Stratigraphic column and δ Corg from Jones et al. (in prep).

Figure 4. Relative abundance data for counts of 100, 200 and 300 specimens in different regions of SH#1-66-120.25 m. This comparison indicates that 200 specimens provide a representative sample of the assemblage. Difference between counts are less than 10% of the relative abundance of the sample for each taxa.

CHAPTER 4 RESULTS

4.1 Calcareous Nannofossil Assemblage

The calcareous nannofossil assemblage composition shows distinct changes during the Carbon Isotope Excursion (CIE; Jones et al., in prep) that defines the stratigraphic extent of OAE2 between 121.15 m and 103.69 m in the SH#1 Core. Higher relative abundance taxa are shown in Figure 5 including Biscutum constans,

Zygodiscus spp., Tranolithus orionatus, and Watznaueria barnesae. Lower relative abundance taxa include: Bronsonia signata, Eiffellithus turriseiffelii, Prediscosphaera spp., Retecapsa spp., Eprolithus floralis, Eprolithus moratus, and Cyclagelosphaera margerelii (Figure 6).

The relative abundance of B. constans is variable but generally high before and after the excursion and generally decreases from 119.95 m to 106.29 m coincident with much of the CIE (Figure 5a, b). Zygodiscus spp. decreases during three intervals: the early stage of the CIE from 120.21 m to 111.28 m, the late stage of the CIE from 106.90 m to 101.30 m, and in the uppermost lower Turonian above the CIE from 99.29 m to

95.69 m (Figure 5c). T. orionatus shows a slight increase in relative abundance during the CIE from 121.11 m to 106.50 m with a sharp increase in a sample at 110.50 m and variable changes before and after the excursion (Figure 5d). W. barnesae shows cyclic increases in relative abundances throughout the study interval (Figure 5e), for example, from 120.25 m to 109.90 m and from 109.90 m to 101.69 m. These intervals also coincide with lower relative abundance of Zygodiscus spp.

The relative abundance of B.signata increases significantly during the CIE from

118 m to 110.91 m, from 110.30 m to 102.28 m, and above the excursion in the uppermost lower Turonian from 100.50 m to 94.90 m (Figure 6b). E. turriseiffelii fluctuates throughout the study interval with a minimum value of 0% at 122.26 m and a maximum value of 11% at 119.66 m (Figure 6c). The relative abundance of

Prediscosphaera spp. shows short-term increases before and during the CIE from

122.34 m to 103.69 m with a decrease above the excursion and variable changes in the lower Turonian (Figure 6d). Retecapsa spp. fluctuates throughout the study interval although it shows a slight increase in abundance from 119.55 m to 101.90 m and an increase up into the uppermost lower Turonian (Figure 6e). The relative abundance of bloom taxa E. floralis and E. moratus exhibit a variable trend throughout the section with a sharp increase during the CIE from 113.50 m to 103.52 m (Figure 6f, g). Finally, C. margerelii shows gradual relative abundance changes coincident with the CIE with a sharp decrease just below the excursion (Figure 6h). Additionally, changes in the relative proportion of C. margerelii correlate well with three intervals of higher CaCO3 %

(Figure S2).

4.2 Geochemistry

PSU TOC% and CaCO3% analyses are plotted side by side to those from Jones et al. (in prep) in Figure S3. PSU TOC% and CaCO3% replicate the trend obtained by

Jones et al. (in prep) although samples are offset by a couple of centimeters in some intervals. TOC and CaCO3 values collected at PSU are described below.

TOC values range from 0.20% to 2.20% (Figure 3). Mean and standard deviation for TOC for the whole section are 0.98% and 0.41%, respectively. There is a short-term increase in values correlating to the onset of the CIE at 121.05 m with a sharp decrease thereafter, from 2.07% to 0.23%, low values continue throughout the early part of the CIE from 120.85 m to 115.19 m. TOC values increase during the middle to later part of the CIE from 115.19 m to 105.50 m with a mean of 1.27%. At the top of the CIE, TOC values decrease to a mean of 1.10% but are still higher than at the onset of the excursion.

CaCO3 values range from 2.17% to 57.48% (Figure 3) with mean and standard deviation of 21.21% and 12.91%, respectively. There is a sharp increase in values at the onset of the CIE at 121.05 m with a sharp decrease thereafter. CaCO3 values are low from 120.45 m to 118.40 m with a mean of 6.45%, and variable during the early to middle stages of the CIE from 118.40 m to 110.10 m with a mean of 19.62%. At the top of the CIE, %CaCO3 values increase to a mean of 34.81%. CaCO3 values are high from

109.90 m to 100.09 m into the mid-lower Turonian, and constant thereafter with an average of 26.36%, higher than pre-CIE values.

Counts of pyrite framboids per 5 traverses range from a minimum of 16 to a maximum of 960 (Figure S4). There is a sharp increase in framboids at the onset of the

CIE at 121.89 m with an abrupt decrease thereafter. Pyrite framboids slowly increase to the maximum value of 960 at 118.60 m in the early stage of the CIE. The highest abundance of pyrite framboids occur throughout the early to middle portion of the CIE with a mean of 370 framboids, followed by a decrease in mean values to 125 framboids

20 towards the top of the CIE into the uppermost lower Turonian with a couple of samples with increased framboids.

4.3 Statistical Analysis

Cluster Analysis- The cluster analysis of taxa yielded two primary groupings throughout the section: one containing more abundant species and/or genera and the other containing rarer species and/or genera (Figure 7). These are then further subdivided into six clusters. The first subgroup in the low abundance group consists of

B. signata and E. turriseiffelii. The second subgroup is composed of Retecapsa spp. and C. margerelii. The third subgroup contains bloom taxa, E. floralis and E. moratus.

The high abundance group is also divided into three subgroups. The first subgroup consists of B. constans and Zygodiscus spp. The second subgroup is solely composed of T. orionatus. Finally, the remaining taxa, W. barnesae and Prediscosphaera spp., compose the third subgroup. Cluster analysis of samples for the entire dataset are included in Appendix B.

Detrended Correspondence Analysis- The DCA of taxa yielded distinctive groupings (Figure 8). Species with different paleoecological affinities separate on DCA1.

On this axis, we see expected trends, such as the split between the eutrophic and cool water species B. constans and the oligotrophic and warm water species W. barnesae

(Table 2). Additionally, we find previously unobserved paleoecological affinities, such as

C. margerelii, E. floralis, and E. moratus grouping with species linked to oligotrophic and warm water conditions. DCA2 values are split between dissolution resistant taxa (B.

21 signata, E. floralis, and W. barnesae) and dissolution susceptible taxa (B. constans).

The divide between the two categories on this axis is less clear since the interpretation is based on few species such as: B. constans, W. barnesae, C. margerelii, E.floralis, and B.signata. DCA 1 accounts for 43.21% of the variance in the original matrix and

DCA2 accounts for 22.60%.

SH#1 samples coded by sample depth do not show a clear trend on either DCA1 or DCA2, or a combination of the two axes (Figure S5). To further explore temporal trends, sample scores were overlain by age, Cenomanian or Turonian (Figure S6).

Samples coded by age still show no distinctive trends in DCA2. However, there is a weak relationship between DCA1 and age (Figure S6a). Samples coded by age on

DCA3, on the other hand, show a clearer split between Cenomanian age and Turonian age (Figure S6b). Cenomanian samples have more negative and lower values on

DCA3, while Turonian samples have more positive and higher values on DCA3. Often,

DCA1 is controlled by age in paleoecological datasets (Schneider et al., 2013). It is possible that both DCA1 and DCA3 have a relationship with age in our dataset.

Additional plots of samples coded by external variables for the entire dataset are included in Appendix B.

13 13 18 An environmental fit of % TOC, % Carbonate, δ Corg, δ Ccarb, δ O, and Pyrite

Framboid vectors were overlain on the DCA ordination with both species and sites

(sample) scores (Figure S7 & S8). The arrow of the fitted vector points to the direction of most rapid change in the environmental variable. Additionally, the length of the arrow is proportional to the correlation between the ordination and environmental gradient. All

22 environmental variables were significant based on the environmental fit except for the pyrite framboid counts.

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Figure 6. Relative abundance patterns of selected calcareous nannofossils in the in nannofossils selected of Figurecalcareous patterns abundance 6. Relative stratigraphic log the iscore. SH#1 timescale, Included the Boundaryrelative interval from core represent gaps) paleoec water taxa, blue shown OAE2 Extentbased CIE the on of is 25

Figure 7. Cluster analysis of species and genera for the entire dataset. Species and/or genera divide into two main groups: high abundance and low abundance in the section. These main groups can be further subdivided into subgroups by environment. These descriptions are based on the overall paleoecological affinities of the species and/or genera included within the grouping (see Table 6).

Figure 8. DCA plot showing species and genera across OAE2 for the SH#1 Core. The groupings are labeled by paleoecological affinity (DCA1) of the taxa.

CHAPTER 5

DISCUSSION

5.1 Non-ecological Factors: Preservation and the closed-sum effect

Before interpreting changes in calcareous nannofossil assemblages as paleoecological and paleoceanographic indicators, it is important to note that nannofossil preservation and relative abundance can be significantly altered during diagenesis

(Thierstein and Roth, 1991). Thorough light microscope observations do not show considerable variation in nannofossil preservation throughout most of SH#1. However, preservation can be addressed indirectly based on changes in CaCO3%, the abundance of dissolution-resistant taxa such as Watznaueria barnesae and species of Eprolithus

(Hill, 1975; Roth & Krumbach, 1986; Williams & Bralower, 1995), and the Coccolith

Fragmentation Index (CFI) (Bralower et al., in prep).

The abundance of W. barnesae is commonly used to interpret preservational changes in Cretaceous-age samples (Roth and Bowdler, 1981). Dissolution experiments using Cenomanian-age assemblages by Hill (1975) show an increase in the abundance of W. barnesae with increasing levels of dissolution. Previous studies have interpreted high abundances of W. barnesae as an indicator of poorly preserved assemblages

(>40%, Thierstein, 1981; Roth and Krumbach, 1986; >70%, Williams and Bralower,

1995). Consequently, high relative abundance of this species along with light microscope observations are used to make a first order assessment of the preservational bias in the core.

Calcareous nannofossil preservation in SH#1 varies from good to excellent based on light microscope observations and the low relative abundance of W. barnesae. The mean abundance of W.barnesae is 10%, with minimum and maximum percentages of

3% and 21%, respectively. Additionally, the mean abundance of Eprolithus spp. in the core is 3.32%, with a minimum and maximum value of 0% and 30.5%. Moreover, samples showing a bloom or high concentrations of Eprolithus spp. do not coincide with samples in which we see the highest abundance of W. barnesae (Figures 5 & 6). Based on the relative abundance of W. barnesae in SH#1 to other CTB sections, nannofossil preservation of the SH#1 Core appears to be better than the Portland Core (mean=

43.91%, min= 20.78%, max= 76.21%) and the Bounds Core (mean= 26.65%, min=

8.46%, max= 48.28%) (Burns & Bralower, 1998).

The relationship of CaCO3% with calcareous nannofossil preservation is not clearly understood. Previous studies have observed that samples with a CaCO3 content greater than 60% generally have overgrown nannofossils while samples with CaCO3 less than

40% have etched nannofossils (Thierstein and Roth, 1991). Carbonate contents in the studied section are mostly below 40%, especially in samples around the four bentonite layers, but never exceed 60% (Figure 3). Therefore, we expect that nannofossils are characterized more by etching than by overgrowth. W. barnesae shows a weak positive correlation (95% confidence level) with CaCO3% (Table 4). On the other hand, the two

Eprolithus species, E. floralis and E. moratus, have a weak negative correlation (95% confidence level) and a moderate negative correlation (99% confidence level) with

CaCO3%, respectively (Table 4). Overall, the SH#1 Core calcareous nannofossil preservation is good, but etching is present.

Interpreting calcareous nannofossil assemblages can be complex due to the

“closed-sum effect”, whereby high abundances or an increase of one species resulting from primary or diagenetic factors may directly cause low abundances of other taxa. For example, low abundance of the dissolution-susceptible B. constans could result from an increase in the dissolution-resistant W. barnesae due to preferential preservation of the less susceptible species. On the other hand, the low percentage of the taxon B. constans may be caused by paleoecologic/paleoceanographic changes independent of an increase in percentage of another taxon.

The “closed-sum” problem is more noticeable when preservation is poor throughout a section and the abundance of dissolution-resistant taxa, like W. barnesae, is high. Good coccolith preservation in a sample allows more confident paleoecological interpretations, although the “closed-sum” problem cannot be ruled out. To address the

“closed-sum” problem in this study, eutrophic and cool water taxa are plotted alongside oligotrophic and warm water taxa (Figure 9). This plot shows that increases in taxa of one paleoaffinity correspond to a decrease with taxa of the opposite affinity, the relationship might be due to ecology, the “closed-sum effect” or both factors. Good preservation and relatively low abundance of dissolution-resistant taxa suggest that diagenesis is not responsible for a closed-sum effect in SH#1 nannofossil assemblage data.

5.2 Interpretation of calcareous nannofossil assemblages

A complex problem to be considered in the interpretation of calcareous nannofossil paleoecology is the decoupling of temperature and productivity. For example, taxa that were adapted to eutrophic environments may have also proliferated in cold-water environments. Alternatively, oligotrophic taxa may be more common in warm-water environments. The cluster dendrogram and DCA of species are used as a first order assessment of taxa paleoaffinities.

The cluster dendrogram of species shows a split between eutrophic-mesotrophic and cool water taxa and oligotrophic and warm water taxa (Figure 7). The paleoecology of species with unknown affinities can be determined from those of the nearest neighboring taxa. For example, the ecology of E. turriseiffelii can be interpreted from its neighbor, B. signata, a eutrophic and cool water indicator. The cluster dendrogram of species shows expected trends from previous studies (Table 2). For example, the widely observed split between B. constans and W. barnesae is also present in SH#1 (Roth &

Krumbach, 1986; Burns & Bralower, 1998; Erba et al., 2002; Eleson & Bralower, 2005;

Lowery et al., 2014; Linnert & Mutterlose, 2015). However, affinities of the bloom taxa,

E.floralis and E. moratus, cannot be determined since these taxa are removed from those with known paleoecological affinities.

To further address the ecology of species, we interpret the DCA1 and DCA2 of species scores (Figure 8). Negative DCA1 values correspond to eutrophic-mesotrophic and cool water taxa such as T. orionatus, B. constans, B. signata, E. turriseiffelii, and

Zygodiscus spp (Table 2). Positive DCA1 values correspond to oligotrophic and warm water taxa such as W. barnesae, Prediscosphaera spp., Retecapsa spp., C. margerelii,

E. floralis, and E. moratus (Table 2). DCA1 does not necessarily represent a gradient from the most eutrophic to the most oligotrophic taxa, but sets a division between these paleoaffinities. The distribution of taxa along DCA1 confirms taxa paleoaffinities from previous studies (Table 2). For example, T. orionatus groups with eutrophic to mesotrophic and cool water taxa as found by Roth (1981), Thierstein (1981), Lees (2002), and Linnert and Mutterlose (2015). On DCA2, some dissolution-resistant taxa plot above zero (B. signata & E. floralis) and some dissolution-susceptible taxa plot below zero (B. constans). However, this axis does not appear to show a clear relationship with an ecological or preservational variable. A couple of taxa are grouped at the center of the

DCA plot because they are present in most samples. Using the correlation of DCA1 with nutrient levels and temperature, we can reconstruct how surface habitats changed during

OAE2 and compare our results with previous interpretations. Moreover, DCA of species allows us to correlate C. margerelii, E. floralis, and E. moratus to oligotrophic and warm water conditions, refining the conclusions of previous studies (Table 2). The occurrence of Eprolithus spp. has been related to dissolution (Hill, 1975; Roth & Krumbach, 1986;

Bralower, 1988; Williams & Bralower, 1995), while few have explored its paleoecological/paleoceanographic affinity (Eshet & Almogi-Labin, 1996; Hardas et al.,

2012; Linnert & Mutterlose, 2015).

An alternative method to examine the ecology of taxa is to determine their correlation with one another. Several groups of calcareous nannofossil taxa show significant correlations in the SH#1 Core (Figure 10 & Tables 3 & 5). The abundance of eutrophic species Biscutum constans shows no significant correlation with the oligotrophic species Watznaueria barnesae (-0.15 ; 93% confidence level) (Figure 10).

After the first difference is applied to the relative abundance data, a highly significant negative correlation exists between these taxa (-0.25; 99% confidence level) (Table 5) which is consistent with previous studies (Roth & Krumbach, 1986; Watkins, 1989; Erba et al., 1992; Williams & Bralower, 1995). The first difference transformation is applied to time series to test whether changes, assemblage shifts in this case, result from a directional trend or are stochastic (McKinney & Oyen, 1989). This is determined from the difference between consecutive values of a time series.

Biscutum constans shows significant negative correlations with other taxa that lie in the oligotrophic and warm-water region of the species DCA plot (e.g. Prediscosphaera spp., E. floralis, E. moratus, and C. margerelii) (Figures 8 & 10). If we test the relationship of B. constans with these taxa after the first difference, we see that these correlations do not hold up (Table 5). Therefore, our data may support the widely-held interpretation that

Biscutum constans was adapted to eutrophic surface waters if we take into consideration that random walk may also be an important factor in the correlation.

In this study, Zygodiscus spp. exhibits correlations that contradict previous interpretations (Erba et al., 1992; Williams & Bralower, 1995). For example, Zygodiscus spp. exhibits a highly significant negative correlation with the eutrophic and cool-water taxon B. constans (Figure 10). Moreover, this species does not show a significant negative correlation with taxa linked to oligotrophic and warm-water environments (Table

3 & 5). Watkins (1989) showed that not all species within a genus have the same paleoecologic affinities. Thus, the mixed signal we observe at SH#1 from Zygodiscus spp. might be caused by the amalgamation of species with different paleoaffinities in this genus. Therefore, care must be taken when applying Zygodiscus spp. as a

33 paleoecological proxy. For simplicity, Zygodiscus spp. will be interpreted as a eutrophic and cool-water taxa based on the species DCA plot results (Figure 8) and previous studies (Roth & Krumbach, 1986; Watkins, 1989; Erba et al., 1992; Burns & Bralower,

1998).

Broinsonia signata exhibits significant positive correlations with taxa with eutrophic and cool water affinities, including E. turriseiffelii (0.24; 99% confidence level) and T. orionatus (0.18; 95% confidence level) (Figure 10). Additionally, B. signata exhibits a significant negative correlation with Zygodiscus spp. (-0.19; 95% confidence level) (Figure

10) which is also interpreted as eutrophic. Since Zygodiscus spp. and E. turriseiffelii lie within the same region in the species DCA plot (Figure 8), it is difficult to interpret the statistical relationships between the taxa. B. signata also shows significant negative correlations with taxa linked to oligotrophic and warm-water environments,

Prediscosphaera spp. (-0.21; 99% confidence level) and E. moratus (-0.18; 95% confidence level) (Figure 10). After applying the first difference to the relative abundance data, the only correlation that holds is the significant negative correlation with Zygodiscus spp. (-0.16; 95% confidence level) (Table 5). Therefore, our data suggest that there might also be a decoupling between nutrients and/or temperature sensitivities between these two taxa, as between B. constans and Zygodiscus spp.

Eprolithus floralis shows a significant positive correlation with Eprolithus moratus

(0.69; 99% confidence level) (Figure 10). This result is expected since both species belong to the same genus. However, these species also show a significant positive correlation with a taxon of the same proposed paleoaffinity, oligotrophic and warm water indicator, C. margerelii, 0.24 and 0.35 (99% confidence level), respectively. After applying

34 the first difference, the only correlation that holds is the significant positive correlation between E. floralis and E. moratus (0.40; 99% confidence level) (Table 5).

While some of the relationships between calcareous nannofossils are inconsistent as paleoecological proxies, several species with well-established affinities (Biscutum constans, Broinsonia signata, and Watznaueria barnesae) display relationships consistent with those observed in previous studies. In addition, we propose that the bloom species E. floralis, E. moratus, and C. margerelii are dissolution-resistant oligotrophic and warm-water taxa.

5.3 Changes in calcareous nannofossil assemblages during OAE2

To explore potential drivers for changes in assemblage in more detail, we discuss

13 correlations between the relative abundance of different taxa and δ Corg, TOC%, and

%carbonate (Table 4). The positive CIE characteristic of OAE2 is related to the burial of large quantities of organic matter in the ocean (Pratt, 1985; Arthur et al., 1987). Values of

13 δ Corg show statistically significant correlations with several nannofossil taxa in the

13 section (Table 4). For example, positive correlations are observed between δ Corg and

B. signata (0.29; 99% confidence level), T. orionatus (0.24; 99% confidence level), and

Zygodiscus spp. (0.26; 99% confidence level) (Table 4).

The relative abundance of the eutrophic species Biscutum constans shows the

13 opposite trend to the δ Corg curve in the SH#1 section (-0.43; 99% confidence level)

(Figure 5 and Table 4). The relative abundance of B. constans decreases at the onset of the positive CIE and later increases at the top of the CIE. However, the correlations

13 between other eutrophic-mesotrophic and cool-water taxa and δ Corg are positive (Table

4). The decoupling of trends amongst taxa with the same paleoaffinity suggests a difference in how taxa respond to changes in either surface-water nutrients or temperature.

Total organic carbon and carbonate values also show statistically significant correlations with several nannofossil taxa (Table 4). Positive correlations exist between

%TOC and B. signata (0.17; 95% confidence level), Retecapsa spp. (0.18; 95% confidence level), E. floralis (0.25; 99% confidence level), and C. margerelii (0.17; 95% confidence level) (Table 4). Although most of these taxa are oligotrophic and warm-water indicators, B. signata is a dissolution-resistant species like E. floralis and C. margerelii.

Testing the relationship between these species and %TOC in other CTB sections will be crucial to determining if these taxa are markers of increased surface-water productivity and/or increased preservation during OAE2.

Carbonate values show positive correlations with B. signata (0.42; 99% confidence level) and W. barnesae (0.16; 95% confidence level) (Table 4). Although W. barnesae is commonly used as an indicator of calcareous nannofossil preservation, the weak positive correlation with %carbonate does not support this interpretation. Since high relative abundances of W. barnesae are interpreted as poor nannofossil preservation or dissolution, and lower CaCO3 samples should be characterized by more dissolution, the correlation between %carbonate and W. barnesae should be negative. Along with the changes in relative abundance, the correlation of W. barnesae with carbonate% suggests that the species is ubiquitous. The positive correlation of B.signata with %carbonate at

SH#1 suggests that this species is a stronger indicator for calcareous nannofossil

36 preservation than W. barnesae. However, the relative abundance of this species is not as high as W. barnesae throughout the section and other CTB studies have not interpreted the abundance changes of this species during OAE2. Negative correlations exist between carbonate values and Prediscosphaera spp. (-0.17; 95% confidence level), E. floralis (-

0.19; 95% confidence level), and E. moratus (-0.30; 99% confidence level) (Table 4).

Calcareous nannofossil assemblage changes in the SH#1 Core show similar trends to the Portland (PO) and Rebecca Bounds (BO) Cores (Burns & Bralower, 1998) but the changes are different in magnitude. The PO and BO Cores are from similar latitudes as SH#1 in central Colorado and western Kansas, respectively, but are more distally located in the basin and were deposited at lower sedimentation rates (Burns &

Bralower, 1998) (Figure 1). There are similarities between W. barnesae, Zygodiscus spp., and B. constans in the three sections.

W. barnesae shows the same trend at the different sites with a decrease in relative abundance at the onset of OAE2 followed upsection by an increase, decrease, and increase (Figure 11). Changes in the relative abundance of W. barnesae are most similar between the SH#1 and PO Cores due to higher sampling resolution. Although the BO

Core, which was sampled at lower resolution, shows more variability throughout the event, the lowest relative abundance values for W. barnesae lie within OAE2 as in SH#1.

For Zygodiscus spp., SH#1 and BO show the same decrease after the onset of OAE2 with the highest values thereafter and a decrease towards the end of the event (Figure

12). However, the trend observed at PO seems to mirror that of SH#1.

Finally, changes in the relative abundance of B. constans are similar between

SH#1 and PO with a decrease in relative abundance right after the onset of OAE2 (Figure

13). However, in the latest portion of the event the relative abundance of B. constans increases at PO stratigraphically before it does at SH#1. The relative abundance of B. constans at BO also shows an increase towards the end of OAE2, but decreases before the onset of the event with some of the lowest values occuring during OAE2. The significant decrease in B. constans, a eutrophic and cool-water taxon, at SH#1 suggests a decrease in either surface-water fertility or increase in water temperatures during OAE2 at the westernmost edge of the WIS.

If we combine the interpretation of B. constans and Zygodiscus spp. we can attempt to decouple their sensitivity to nutrients or temperature. The sharp decrease in B. constans during OAE2 is likely due to a change in water temperature and the incursion of warm Tethyan waters. Therefore, the early decrease in B. constans at BO before the other sites could be a sign of the counterclockwise circulation of Tethyan and Boreal waters modeled by Slingerland et al. (1996) in the WIS during the late transgression phase of the latest Cenomanian to early Turonian.

Other studies of the CTB in the WIS have also discussed the incursion of warmer

Tethyan waters in temperate latitudes (Kauffman, 1977; Elder, 1985 and 1991; Elder &

Kirkland, 1985; Watkins, 1986 and 1993; Hay et al., 1993; Fisher et al., 1994; Leckie et al., 1998; Eleson & Bralower, 2005; Lowery et al., 2014). Although we do not show a simple relationship between the major surface water fertility indicators, B. constans and

W. barnesae, at SH#1, previous studies such as Paul et al. (1999), Gale et al. (2000), and Corbett and Watkins (2013) show increases in nannofossil taxa during OAE2 that are typically associated with lower latitudes. The observed decrease in surface water productivity during OAE2 at SH#1 was thus likely due to the incursion of warmer, saline

38 waters from the south that increased stratification and reduced mixing leading to anoxia and enhanced burial of organic carbon. The foraminiferal record from the KPS1 and KPS2 outcrops near Big Water, UT are interpreted as showing a pulse of Tethyan waters associated with the transgression of the Greenhorn Cyclothem followed by increased productivity and the incursion of the oxygen minimum zone during the latest stage of

OAE2 (Parker, 2016).

This study supports the idea that increased water column stratification and preservation was the mechanism for organic rich sediment burial during OAE2 as proposed by previous authors (Arthur et al., 1987; Burns & Bralower, 1998; Leckie et al.,

2002; Erba, 2004; Eleson & Bralower, 2005; P. Hardas & Mutterlose, 2007; Jenkyns,

2010; Corbett & Watkins, 2013; Elderbak & Leckie, 2016). Paleoecological/ paleoceanographic interpretations of calcareous nannofossil assemblage change suggest warm and oligotrophic conditions at the base of OAE2. Gradually, surface ocean conditions at the western margin cool and become eutrophic towards the end of the event as suggested by the increase in B. constans and Zygodiscus spp (Figure 5).

Figure 9. Relative abundance of eutrophic and cool water taxa (green line) plotted alongside oligotrophic and warm water taxa (blue line) for SH#1 Core. Eutrophic and cool water taxa include B. signata, B. constans, T. orionatus, E. turriseiffelii, and Zygodiscus spp. Oligotrophic and warm water taxa include E. floralis, W. barnesae, C. margerelii, Prediscosphaera spp., Retecapsa spp., and E. moratus.

Figure 10. Heatmap of Pearson correlation coefficients between calcareous nannofossil taxa for SH#1. The color of each square represents whether the correlation between taxa is positive (red) or negative (purple). Color shade of each square shows strength of the correlation.

Figure 11. Comparison of the relative abundance of W. barnesae for the SH#1, Portland (PO) and Bounds (BO) Cores throughout the Cenomanian-Turonian Boundary during OAE2. PO and BO data are from Burns and Bralower (1998). Sections have been correlated in time using the “B” interval of the organic carbon isotope excursion as defined by Pratt and Threlkeld (1984). For a 13 correlation of δ Corg records of the sites see S9.

Figure 12. Comparison of the relative abundance of Zygodiscus spp. for the SH#1, Portland (PO) and Bounds (BO) Cores throughout the Cenomanian-Turonian Boundary during OAE2. PO and BO data are from Burns and Bralower (1998). Sections have been correlated in time using the “B” interval of the organic carbon isotope excursion as defined by Pratt and Threlkeld (1984). 13 For a correlation of δ Corg records of the sites see S9.

Figure 13. Comparison of the relative abundance of B. constans for the SH#1, Portland (PO) and Bounds (BO) Cores throughout the Cenomanian-Turonian Boundary during OAE2. PO and BO data are from Burns and Bralower (1998). Sections have been correlated in time using the “B” interval of the organic carbon isotope excursion as defined by Pratt and Threlkeld (1984). For a 13 correlation of δ Corg records of the sites see S9.

CHAPTER 6

CONCLUSIONS

The Tropic Shale Formation of southwestern UT represents a prodeltaic muddy shelf deposited during the Greenhorn Cyclothem, a large-scale third-order transgressive-regressive cycle, when the WIS was at its maximum western extent

(Kauffman, 1977; Elder et al., 1994). The environmental and ecological perturbations of

OAE2 are captured in sediments of the Tropic Shale at SH#1 giving us the opportunity to explore changes in calcareous nannofossil assemblages. The Tropic Shale is associated with significant calcareous nannofossil assemblage changes. The most notable change amongst taxa is that of dissolution-susceptible eutrophic and cool water taxon Biscutum constans (Figure 5). Synchronous to the CIE, B. constans shows a

13 decrease of ~10% in relative abundance compared to pre-CIE values. As δ Corg values return to pre-CIE values, there is an ~15% increase in relative abundance of this species.

Cluster analysis and DCA help refine the paleoecological/paleoceanographic affinities of C. margerelii, E. floralis, and E. moratus (Figure 7 & 8). While C. margerelii lies next to Retecapsa spp., an oligotrophic and warm water taxa, in a cluster dendogram of species, the paleoaffinity of E.floralis and E. moratus cannot be determined since these taxa are removed from those with known paleoecological affinities. However, in DCA C. margerelii, E. floralis, and E. moratus clearly lie within the oligotrophic and warm water region of DCA 1 with other taxa with set paleoaffinities.

An increase in water column stratification and preservation during OAE2 is inferred in the WIS at SH#1 from the pronounced decrease in the eutrophic taxon Biscutum constans. Although we do not observe similar changes of the same duration and magnitude in other eutrophic-mesotrophic taxa, we believe this is due to the decoupling or breakdown of paleoaffinities. This can be seen specifically between B. constans and

Zygodiscus spp. showing a similar trend of a decrease at the beginning of OAE2 but in the second half of the event Zygodiscus spp. abundance values increase while B. constans values stay low until the latest portion of the event (Figure 5). The significant decrease in B. constans, a eutrophic and cool-water taxon, at SH#1 suggests a decrease in either surface-water fertility or increase in water temperatures during OAE2 at the westernmost edge of the WIS. The sharp decrease in B. constans during OAE2 is likely due to a change in water temperature and the incursion of warm Tethyan waters from the

Greenhorn Cyclothem. Therefore, B.constans is more sensitive than Zygodiscus spp. to changes in water temperature and nutrient inputs to the basin at SH#1.

Although the calcareous nannofossil assemblages from SH#1 were compared to those of the PO and BO Cores, to be confident in taxa paleoaffinities it is crucial to expand the datasets used in multivariate analysis. Doing this can provide regional confidence for paleoaffinities of nannofossils from the CTB. Furthermore, it can improve our interpretation of which mechanism (increased productivity or water column stratification and preservation) was active during OAE2 and deposited organic rich sediments during the event if we are using calcareous nannofossils as a paleoclimatic/ paleoceanographic proxy.

APPENDIX A TABLES

TABLE 1.- CALCAREOUS NANNOFOSSIL RELATIVE ABUNDANCE DATA

Table 2. Known paleoecological affinities for calcareous nannofossil species/genus used in analyses. Eurytopic organisms have the ability to live in a wide variety of habitats and tolerate a wide range of environmental conditions. Information for this table was compiled from previous studies (Bornemann et al., 2005; Burns and Bralower, 1998; Corbette and Watkins, 2013; Eshet and Almogi-Labin, 1996; Eleson and Bralower, 2005; Erba et al., 1986, 1992; Hardas et al., 2012; Hill, 1975; Kessels et al., 2003; Lees, 2002; Linnert and Mutterlose, 2013, 2015; Lottaroli and Catrullo, 2000; Lowery et al., 2014; Mutterlose and Kessels, 2000; Popischal and Wise, 1990, 1992; Premoli Silva et al., 1989; Roth 1981, 1989; Roth and Bowdler, 1981; Roth and Krumbach, 1986; Thierstein, 1981; Watkins, 1989).

Values given are Pearson coefficients are Pearson given Values

TAXA CORRELATION COEFFICIENTS CORRELATION TAXA

Bold type indicates values that are significant at the 99% confidence level. confidence 99% the at significant are that values type indicates Bold

Italic type indicates values that are significant at the 95% confidence level. confidence 95% the at significant are that values type indicates Italic

SMOKY HOLLOW #1 CORE SMOKYHOLLOW

TABLE 3 TABLE

TABLE 4.- SMOKY HOLLOW #1 CORE TAXA AND GECHEMISTRY CORRELATION COEFFICIENTS1

Italic type indicates values that are significant at the 95% confidence level. Bold type indicates values that are significant at the 99% confidence level. 1Values given are Pearson coefficients

confidence level. confidence

Values given are Pearson coefficients are Pearson given Values

Bold type indicates values that are significant at the 99% 99% the at significant are that values type indicates Bold

Italic type indicates values that are significant at the 95% confidence level. confidence 95% the at significant are that values type indicates Italic

SMOKY HOLLOW #1 CORE TAXA CORRELATION COEFFICIENTS AFTER FIRST DIFFERENCE COEFFICIENTSAFTER CORRELATION #1 CORE TAXA SMOKYHOLLOW

TABLE 5 TABLE

APPENDIX B

MULTIVARIATE ANALYSIS METHODS

B.1 Cluster Analysis

The transformation and distance measure chosen for cluster analysis in Q-mode

(samples) were the Wisconsin Transformation and the Bray-Curtis Distance.

Transformations improve the normal linearity and make variables (i.e. taxa) comparable; distance measures constrain the distance between samples in multivariate space

(McCune and Grace, 2002). The Wisconsin transformation was chosen because it normalizes both rows and columns by the maximum value. The coefficient of variation for rows was 5.78 (low effect) and 87.96 (high effect) for columns. The Bray-Curtis

Distance was chosen because it is ideal for analyzing ecological datasets. Additionally, the Bray-Curtis Distance Measure and Ward’s method create compact and identifiable groups and produce a high agglomerative coefficient. The agglomerative coefficient expresses the strength of clusters. The clustering method Group Average was also tested, but agglomerative coefficient values were higher with the Wisconsin

Transformation, Bray-Curtis Distance and Ward’s Method (Figure B1). External variables from the sample attributes matrix were overlain on the sample cluster to find trends in the data (Figure B2-B7).

For cluster analysis in R-mode (species), the transformation and distance measure used were Column Maxima and Bray-Curtis Distance. The Column Maxima transformation relativizes values in columns by the highest value. The combination of using Column Maxima Relativization, Bray-Curtis Distance and Ward’s Method resulted in the highest agglomerative coefficient value.

B.2 Detrended Correspondence Analysis

The Wisconsin transformation was chosen for DCA because it normalizes both rows and columns by the maximum value. DCA uses a Chi-square Distance metric so that the distance between sites and species scores is proportional to their chi-square value. This type of distance metric gives a lot of weight to rare species which is ideal for the Smoky Hill assemblage. Eigenvalues can be transformed to percent variance by calculating the total of the first four DCA axes and dividing each individual eigenvalue by that total. The percent variance explained for DCA using the Wisconsin Transformation and Chi-square Distance metric for the first four axes are: 43.21%, 22.60%, 19.27%, and 14.92%. External variables from the sample attributes matrix were overlain on site scores to find trends in the data (Figure B8-B12).

in the the in

d using different hierarchical clustering methods. The clustering using d hierarchical different

hand side created using the Group Average Method. Note the the Average Note difference Method. the Group handusing created side

hand side was created using the Ward’s Method and shows simple structure unlike unlike and structure simple shows Method handusing side the Ward’s created was

create Dendrograms Sample SH#1FigureB1. dendrogram the on left right dendrogram the the on dendrograms. coefficientagglomerative the between two

Figure B2. SH#1 Sample Dendrogram showing samples across OAE2 overlain by age of the sample.

Figure B3. SH#1 Sample Dendrogram showing samples across OAE2 overlain by stage of the event the sample belongs to.

Figure B4. SH#1 Sample Dendrogram showing samples across OAE2 overlain by TOC% of the sample.

Figure B5. SH#1 Sample Dendrogram showing samples across OAE2 overlain by Carbonate% of the sample.

13 Figure B6. SH#1 Sample Dendrogram showing samples across OAE2 overlain by δ Corg of the sample.

Figure B7. SH#1 Sample Dendrogram showing samples across OAE2 overlain by δ18O of the sample.

by stage of the event the the stage event the of by

heSH#1 Core overlain

owing samples across OAE2 for t for across samples owing OAE2

. DCA plot sh . DCA

FigureB8 samplebelongs to.

TOC% of the sample. the of TOC%

n by n

heSH#1 Core overlai

owing samples across OAE2 for t for across samples owing OAE2

. DCA plot sh . DCA

FigureB9

by Carbonate% the of by

overlain

heSH#1 Core

owing samples across OAE2 for t for OAE2 across samples owing

. DCA plot sh DCA .

FigureB10 sample.

of the the of

org

by δ by

overlain

heSH#1 Core

owing samples across OAE2 for t for OAE2 across samples owing

. DCA plot sh DCA .

FigureB11 sample.

O of the the O sample. of

by δ by

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owing samples across OAE2 for t for OAE2 across samples owing

. DCA plot DCA .

FigureB12

APPENDIX C SUPPLEMENTARY FIGURES

Figure S1. SH#1 calcareous nannofossil assemblage sampling resolution. Sampling resolution was adjusted throughout the core to constrain peaks in nannofossil assemblage counts. Resolution generally decreases upcore and is the highest around the onset of OAE2.

Figure S2. SH#1 %Carbonate values and relative abundance of C. margerelii (%). Changes in the relative proportion of C. margerelii correlate with three intervals of increased changes in CaCO3%.

Figure S3. Comparison of NU (Jones et al., in prep) and PSU %TOC and %Carbonate. %TOC and %Carbonate values were collected at PSU to complement calcareous nannofossil assemblage counts for statistical analysis.

Figure S4. Abundance of pyrite framboids in the Cenomanian-Turonian interval of the 13 SH#1 Core. Included are the δ corg values (Jones et al., in prep) and TOC % (this study).

Figure S5. DCA plot showing samples across OAE2 for the SH#1 Core. Samples are labeled by depth, 122.335 m being the oldest sample and 94.56 m the youngest sample. No clear trend in age was found in plotting the samples by depth on DCA1, DCA2 or a combination of the two axes.

Figure S6. DCA plot showing samples across OAE2 for the SH#1 Core overlain by Age of the sample. Samplessample. the of by Core SH#1 the for acrossAge overlain OAE2 samples showing plot Figure S6. DCA age.Turonian are in color light green age in in are the those color the in while green dark Cenomanian

Figure S7. DCA plot showing species and genera across OAE2 for the SH#1 Core overlain by 13 environmental vectors. Vectors included are: %TOC, % Carbonate, δ Corg, Pyrite Framboids, 13 18 13 13 18 δ Ccarb, and δ O. δ Corg, δ Ccarb, and δ O values are interpolated from Jones et al (in prep).

Figure S8. DCA plot showing sample across OAE2 for the SH#1 Core overlain by environmental 13 13 18 vectors. Vectors included are: %TOC, % Carbonate, δ Corg, Pyrite Framboids, δ Ccarb, and δ O. 13 13 18 δ Corg, δ Ccarb, and δ O values are interpolated from Jones et al (in prep).

13 Figure S9. δ Corg records for SH#1, Portland (PO), and Bounds (BO) Cores used to correlate between sections. A, B, and C intervals of the organic carbon isotope excursion as defined by 13 13 Pratt and Threlkeld (1984) are labeled alongside δ Corg values. δ Corg record for SH#1 from 13 13 Jones et al (in prep). δ Corg record for PO from Sageman et al. (2006). δ Corg record for BO from Scott et al. (1998).

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