Insights Into the Early Transgressive History of Lake Bonneville from Stratigraphic Investigation of Pilot Valley Playa, UT/NV, USA

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Theses and Dissertations

2012-10-30

Insights into the Early Transgressive History of Lake Bonneville from Stratigraphic Investigation of Pilot Valley Playa, UT/NV, USA

Kevin A. Rey Brigham Young University - Provo

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BYU ScholarsArchive Citation Rey, Kevin A., "Insights into the Early Transgressive History of Lake Bonneville from Stratigraphic Investigation of Pilot Valley Playa, UT/NV, USA" (2012). Theses and Dissertations. 3803. https://scholarsarchive.byu.edu/etd/3803

This Thesis is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Insights into the Early Transgressive History

of Lake Bonneville from Stratigraphic

Investigation of Pilot Valley

Playa, UT/NV, USA

Kevin A. Rey

A thesis submitted to the faculty of Brigham Young University in partial fulfillment of the requirements for the degree of

Master of Science

Alan L. Mayo, Chair Stephen T. Nelson Barry R. Bickmore

Department of Geological Sciences

Brigham Young University

October, 2012

Insights into the Early Transgressive History of Lake Bonneville from Stratigraphic Investigation of Pilot Valley Playa, UT/NV, USA.

Kevin A. Rey Department of Geological Sciences, BYU Master of Science

Multiple shallow sediment cores were obtained from Pilot Valley playa, a sub-basin located in the northwestern Bonneville basin. Analysis of stratigraphy, ostracodes, mineralogy, chemistry, total inorganic carbon (TIC), total organic carbon (TOC), and stable isotopes were performed to better place these sediments into proper context with respect to the Lake Bonneville cycle. Results showed Pilot Valley playa contains a nearly full sequence of Lake Bonneville deep-water marl in addition to sediments deposited before and after the Lake Bonneville cycle. Within the marl is a sequence of organic rich algal laminated marl correlated with the Stansbury oscillation. Four 14C ages ranging from ~22.4 k 14C years to ~15.8 k 14C years from preserved algae filaments in this sequence place it well within the time frame of the Stansbury oscillation. Oolitic sand found below this sequence indicates the existence of a shallow (<~5 m), saline lake in Pilot Valley prior to the transgression of Lake Bonneville. Analysis of sediments deposited during the late regressive phase of Lake Bonneville indicates the lake may have fallen to levels below that of Pilot Valley prior to transgressing to the Gilbert level.

Keywords: Lake Bonneville, Lake Bonneville marl, Stansbury oscillation, Pilot Valley playa, Pilot Valley stratigraphy

ACKNOWLEDGEMENTS

I would like to thank my committee chair, Dr. Alan Mayo, for his patience as I worked though the details of this project. I also want to thank my committee members Dr. Steve Nelson and Dr. Barry Bickmore for their insight and advice as I was writing. Dr. Charles G. “Jack”

Oviatt, of Kansas State University, was instrumental in helping me understand how to catalog and interpret various aspects of each core used in this project and in analyzing ostracodes. David

Tingey provided many hours of laboratory instruction during sample preparation and analysis.

Jeffery Rampton and Shawn Wiggins spent time with me in Pilot Valley on blisteringly hot summer days as well as frigidly cold and muddy winter days collecting cores. Their contribution proved invaluable. This entire project would not have been possible were it not for the financial support of the BYU Hydrogeochemistry Laboratory. Finally I must thank my wife, April, who for the past two years has put up with me as I have finished my Master’s Degree.

TABLE OF CONTENTS

TABLE OF CONTENTS ...... iv LIST OF FIGURES ...... v LIST OF TABLES ...... vi INTRODUCTION ...... 1 Purpose and objectives ...... 4 SITE DESCRIPTION ...... 5 METHODS ...... 6 Field methods ...... 6 Laboratory Methods ...... 6 Ostracodes ...... 7 Mineralogy ...... 7 Chemistry—Major and Trace Elements ...... 8 Total Inorganic Carbon and Total Organic Carbon ...... 9 Stable Isotopes—δ13C and δ18O ...... 9 Dating ...... 10 RESULTS ...... 11 Overview of Stratigraphy ...... 11 Detailed Stratigraphy of PVC 15 core ...... 14 Ostracodes ...... 15 Mineralogy ...... 15 Bulk Chemistry—Major and Trace elements ...... 18 Total Inorganic Carbon and Total Organic Carbon ...... 19 Stable Isotopes— δ18O and δ13C ...... 19 Dating ...... 20 DISCUSSION ...... 20 Unit V ...... 20 Unit IV ...... 21 Unit III ...... 24 Unit II ...... 25 Unit I ...... 27 CONCLUSIONS...... 28 REFERENCES ...... 31 FIGURES ...... 36 TABLES ...... 54 Appendix A ...... 58

LIST OF FIGURES

Figure 1. Map showing major Lake Bonneville levels and study area...... 37 Figure 2. Pilot valley and surrounding area ...... 38 Figure 3. Core locations in Pilot Valley...... 39 Figure 4. Schematic stratigraphic column ...... 40 Figure 5. Stratigraphic cross-section across Pilot Valley ...... 41 Figure 6. Unit V: PVC 15 oolitic sand ...... 42 Figure 7. Unit IV: PVC 15 algal laminated marl ...... 42 Figure 8. Photo micrograph of algae filaments ...... 43 Figure 9. Unit III: PVC 15 olive gray massive marl ...... 43 Figure 10. Sand bed in PVC 20 ...... 44 Figure 11. Unit II: PVC 15 yellow gray massive marl ...... 44 Figure 12. Unit I: PVC 15 laminated silt and sand bed ...... 45 Figure 13. Bar graph of ostracodes first and last appearance ...... 46 Figure 14. PVC 15 core depth vs. mineralogy ...... 47 Figure 15. PVC 15 depth vs. calcite and aragonite ...... 47 Figure 16. Normalized calcite and aragonite ...... 48 Figure 17. Plots of XRF results...... 49 Figure 18. PVC 15 TIC and TOC as a function of depth ...... 50 13 18 Figure 19. Scatter plot of δ CVPDB vs. δ OVSMOW ...... 51 18 13 Figure 20. Depth vs. δ OVSMOW and δ CVPDB in PVC 15 ...... 52 Figure 21. 14C sample locations ...... 53

LIST OF TABLES

Table 1. UTM coordinates of core locations in Pilot Valley ...... 55 Table 2. Table of stratigraphic units ...... 55 Table 3. Sample depths from core PVC 15...... 56 Table 4. Table of TIC and TOC ...... 57

INTRODUCTION

The study of topographically closed basins in the western United States, which contained pluvial lakes, dates back more than 100 years. In many basins evidence for their existence has come from the study of geomorphology, stratigraphy, chemistry, and mineralogy. Gilbert (1890) and Russell (1885) wrote pioneering works which dealt with the identification and description of features related to Lakes Bonneville and Lahontan, respectively. Climatic factors such as precipitation, evaporation, temperature, and wind are believed to have exerted the greatest control on the timing and size of these lakes (Madsen et al., 2001; Oviatt, 1997).

The Bonneville basin, located in the northeastern Great Basin of the western United

States (Figure 1), has been the location of pluvial lakes for at least the last 800 ka (Eardley et al.,

1973; Oviatt et al., 1999). The latest large lake was Lake Bonneville with the Great Salt Lake being the largest remnant (Currey, 1990; Gilbert, 1890). Much work has been done to decipher the history and timing of events as they relate to Lake Bonneville as well as climatic variation in the Bonneville basin (Benson et al., 1992; Benson et al., 2011; Madsen et al., 2001; Nelson et al.,

2005; Oviatt, 1997).

Most evidence on Lake Bonneville has been collected from outcrops related to ancient shorelines (Godsey et al., 2005; Godsey et al., 2011; Morrison, 1965; Oviatt, 1991, 1997, 2002;

Oviatt et al., 1990; Oviatt, McCoy, et al., 1994). Lake Bonneville shorelines are seen as wave cut terraces along most mountain ranges throughout the Bonneville basin. Due to their conspicuous nature these ancient shorelines are relatively easy to identify and correlate as low, middle, and high lake stands which allows for the direct calculation of lake size. In addition, shorelines preserve evidence for the transgressive/regressive nature of the lake.

In the Bonneville basin four major shorelines from Lake Bonneville have been identified

(Figure 1). From oldest to youngest they are Stansbury, Bonneville, Provo, and Gilbert with

approximate elevations of 13601, 1555, 1444, and 1300 meters above sea level (masl) (Currey,

1980, 1982; Oviatt, 1987; Oviatt et al., 1990; Oviatt et al., 1992). Stansbury formed during the initial transgressive phase. The Bonneville shoreline represents a period of relatively stable lake levels where the lake spilled over a natural threshold into the Snake River drainage. Provo and

Gilbert formed during the regressive phase of Lake Bonneville. Evidence for the Bonneville,

Provo, and Gilbert shorelines is widespread due to preservation of their respective shorelines throughout the Bonneville basin. However, evidence for Stansbury is more scarce since it formed during the transgressive phase of the lake and has been overprinted by other shorelines. There are only a few localities where Stansbury shore deposits have been preserved well enough to allow for detailed study (Currey, 1982; Green & Currey, 1988; Oviatt, 1987; Patrickson et al., 2010).

The majority of work done on Lake Bonneville has been accomplished at outcrops.

However, looking at the Bonneville basin as a whole, it is apparent that much of it is occupied by broad flat basins which contain sediments deposited on the lake bed. A practical method for study in these basins is by obtaining cores of the sediments from within these basins.

Published work on the Bonneville Basin taken from coring projects is not extensive.

Eardley et al. (1973) studied a core obtained near the south arm of the Great Salt Lake in which they identified multiple lake cycles over the past 800 ka. Spencer et al. (1984) collected several cores from the south arm of the Great Salt Lake and analyzed them for various stratigraphic and geochemical features to correlate with outcrop-based studies. Thompson et al. (1990) analyzed chemistry, mineralogy, and crustaceans, as well as performing AMS 14C dating on organic mud

1 The Stansbury stage of Lake Bonneville consists of several visible shorelines in the Bonneville basin. The elevation used in the paper follows an average value from the conclusions of Oviatt et al. (1990).

from Lake Bonneville sediments. Benson et al. (2011) collected two cores from a warm spring area and, using a paleomagnetic secular variation (PSV) based model for one of their cores as an

age control, provided a continuous record of lake-level change for the period 45.1 – 10.5 ka.

They analyzed the cores for changes in δ18O and total inorganic carbon and found they generally

matched what had been published based on outcrops but noted differences in the timing of some

hydrologic events.

In each of these studies there is a sequence of dark brown to black organic rich mud.

Oviatt et al. (1990) believe this organic rich mud to correlate with the Stansbury level of Lake

Bonneville. Several methods were employed to date this sequence. With the exception of

Spencer et al. (1984), 14C ages were obtained from within this sequence. Published ages in 14C

years include 20,930 ± 230 from Oviatt et al. (1990), 22,500 ± 190 and 21,050 ± 320 from

Thompson et al. (1990), and 18,440 ± 60 from Benson et al. (2011). The 14C age from Benson et

al. (2011) is significantly younger than the other reported ages, does not fit with ages obtained

from their surrounding samples, and was left out of their palaeomagnetic secular variation (PSV)

chronology. Benson et al. (2011) relied on their PSV chronology and changes in δ18O and total

inorganic carbon (TIC) which provided an age of approximately 25 ka. Spencer et al. (1984)

used a method of linear extrapolation between dated tephras. The great differences in published

ages leaves open the opportunity to better constrain and evaluate the sequence of organic-rich

mud.

Cores analyzed by Benson et al. (2011) and Spencer et al. (1984), and one outcrop

analyzed by Oviatt et al. (1990), imply that this sequence of finely laminated organic rich mud

appears to be part of the early transgression of Lake Bonneville, perhaps the Stansbury

oscillation. Dates for this sequence range from about 24.4 ka to 29.5 ka depending on the source.

This wide spread in dates provides a poor constraint. Our coring on Pilot Valley playa exhibits a similar sequence of laminated, organic-rich mud which may correlate with the laminated sequence found in other studies. Using a systematic approach by obtaining ages from multiple stratigraphic levels in the organic rich mud would help narrow and better understand the timing of its deposition. Knowing the spatial distribution of the mud and the character of the playa sediments will allow for greater understanding of factors related to lake depth, climate, water chemistry, etc.

Oviatt (1987) labels the white marl of Gilbert (1890) as representing chemically precipitated, shallow to deep-water, sediments. Taking this information and applying it to sediments deposited during the open water phase of Lake Bonneville seems appropriate for the purpose of consistency. As such the term marl will be used to refer generally to the sediments which comprise the shallow subsurface of Pilot Valley.

Purpose and objectives

The purpose of this work is to characterize and interpret the sequence of laminated organic rich marl obtained from cores in Lake Bonneville sediments by investigating the stratigraphy of cores taken from Pilot Valley playa. Objectives include:

1. Characterize shallow playa stratigraphy from Lake Bonneville time to present

2. Obtain 14C ages from the organic rich laminated marl to better constrain the timing of

deposition

3. Evaluate the chemistry and mineralogy of shallow cores obtained from Pilot Valley playa

4. Correlate playa stratigraphy with biostratigraphy from published work

SITE DESCRIPTION

Pilot Valley is a hydrologically closed basin situated in the eastern Great Basin of the

United States (Figure 1and Figure 2). It lies principally in the state of Utah with only the very southwestern portion in Nevada and is approximately 33 km in length and between 8 km and 15 km in width. It runs southwest by northeast and is bordered on the west by the Pilot Range and on the east by the Silver Island Mountains. The Pilot Range reaches an elevation of over 3200 masl at Pilot Peak and is composed principally of metamorphic quartzite, schist, and phyllite

(Miller, 1990b). The Silver Island Mountains are considerably lower in elevation with the highest point being Graham Peak at approximately 2300 masl and are composed primarily of

Paleozoic limestone, dolomite, and shale with lesser amounts of Mesozoic granitoid rocks

(Miller, 1990a). Both mountain ranges follow a north/south alignment, which typifies mountain

ranges in the Basin and Range province of the western United States.

In Pilot Valley both the Pilot Range and the Silver Island Mountains are flanked by extensive alluvial fans (Miller, 1990b, 1993). On the west the alluvial fan/playa boundary is quite abrupt with playa sediments juxtaposing onto the alluvial fans. On the east the transition from alluvial fans to playa sediments is more gradual. Alluvial covered mountain front surfaces transition from mountain front alluvial fan deposits to a thin alluvial covering on lacustrine pediment surfaces. Locally the fan deposits interfinger with the lacustrine deposits. Further down-gradient the Pilot Valley sub-basin is filled with thousands of meters of lacustrine and clastic sediment (Carling et al., 2012). The major Lake Bonneville shorelines (Stansbury,

Bonneville, Provo, and Gilbert) are conspicuous throughout the entire valley and can be seen as wave-cut terraces, especially along the Silver Island Mountains.

METHODS

Field methods

22 cores were collected from Pilot Valley playa in order to understand the spatial distribution of playa stratigraphy (Figure 3 and Table 1). Core locations were chosen based on providing locations in Pilot Valley along the playa margin and within the playa interior as well as

their adjacency to existing wells whose elevations had already been surveyed. Cores were

collected during the summer and fall of 2011 with a hand-driven percussion corer fitted with a 5

cm diameter thin-wall plastic liner. In preparation for each consecutive drive of the corer, and

due to the consistency of the material being cored, it was necessary to hand auger the core hole

to 7.5 cm to prevent slumped material from clogging the hole and plugging the corer. Cores were

collected in sections up to 60 cm in length, which represents the length accommodated by the

corer. Core retrieval averaged around 85% with the exception of dry or very sandy/coarse

grained material. In these instances it proved difficult to retrieve any usable core. Core sections

were capped and labeled in the field for transport back to the laboratory for preparation and

analysis.

Laboratory Methods

All cores were processed at the Brigham Young University (BYU) Hydrogeochemistry

Laboratory using the procedure outlined by Schnurrenberger et al. (2003). Cores were split in

half lengthwise with one half in cellophane, vacuum-sealed, and archived. The other half was

scraped clean for photographs and examination of stratigraphic features. Depth measurements

were taken from the upper left corner of the split core liner when it was laid in the measuring jig.

Cumulative depth for each core was calculated adding together the length of each core section

and by taking into account disturbed bedding, gaps, etc. and adjusting as necessary. All reported

depths, unless otherwise noted, were taken from core PVC 15 (Table 2). Core PVC 15 was chosen for detailed analysis of stratigraphy, ostracodes, mineralogy, chemistry, and stable isotopes because it contained the most complete section of sediments from pre-Lake Bonneville to post-Lake Bonneville. Other cores often lacked one or more stratigraphic layers. Use of PVC

15 also ensured consistency with laboratory analyses as well as providing a consistent method for reporting stratigraphic units and features, and making correlations with other cores.

60 samples were collected from core PVC 15 with an average interval of 5 cm. Each sample was approximately 2 cm thick and was analyzed for mineralogy, ostracodes, chemistry, total inorganic carbon (TIC), total organic carbon (TOC), and stable isotopes. In the few instances where the stratigraphy at a sample location appeared disturbed or otherwise compromised it was skipped and sample collection resumed at the next nearest 5 cm interval.

Samples for 14C analysis were collected from core PVC 22 as it displayed excellent preservation of the organic rich marl.

Ostracodes

Core PVC 15 ostracode samples were prepared and analyzed by Charles G. “Jack” Oviatt at Kansas State University.

Mineralogy

Mineralogy from core PVC 15 was determined using RockJock11 (Eberl, 2003) from powder X-ray diffraction (XRD) patterns. The RockJock11 user guide was followed for sample preparation. Power samples were analyzed on a Scintag XDS 2000 XRD instrument.

Samples were analyzed with RockJock11 following the advice given by Eberl (2003) to try and keep the full pattern degree of fit to <0.1. This was done by making multiple runs starting with only two or three mineral species and increasing the number of mineral species on

subsequent runs. In a few instances the degree of fit approached 0.12 with three samples having a

degree of fit around 0.15. However, the majority of samples had a degree of fit ≤0.1.

The minerals quartz, orthoclase, and oligoclase were considered representative of clastic

input from the surrounding mountains. Any silica precipitated from water would be amorphous

with measured two-theta peaks displaying as broad humps. Peaks for these silicate minerals were

narrow and typical crystalline material. Dolomite was also considered clastic material as it was likely secondary in origin having originated from the surrounding mountains. It was unlikely that any dolomite present in the analysis is due to diagenetic processes (Mueller & Foerstner, 1972).

Chemistry—Major and Trace Elements

Major and trace elements (Appendix A) for core PVC 15 were analyzed by X-ray fluorescence (XRF). Samples were prepared by drying overnight in an oven set to 55°C. After drying, each sample was crushed with a ceramic mortar and pestle. The resulting powder was screened in successive sieves to 320 mesh.

Samples were prepared for major element analysis by combining 1.23 grams of powered sample with 8.61 grams of flux. This mixture was placed in a platinum crucible and melted in a

Katanax fusion furnace to create a glass disc. For trace element analysis 8.3 grams of powdered sample was combined with a binder in a Spex 8000 mixer mill in a disposable plastic vial. The powder-binder mix was pressed at 20 tons in a Spex pellet die. The pellet was supported by an aluminum cap. The glass disc and pressed pellet were analyzed in a Rigaku Primus II ZSX XRF instrument using the mineral pack method for major and trace elements. Major element results are returned as oxides, eg. CaO for calcium, and are reported in weight percent (%). Trace elements are reported in parts per million (ppm).

Total Inorganic Carbon and Total Organic Carbon

Total Inorganic Carbon and Total Organic Carbon for core PVC 15 were determined

following the method outlined by Heiri et al. (2001). Approximately 2 grams of material from each sample was used in the analysis.

Stable Isotopes—δ13C and δ18O

Samples for stable isotope analysis from core PVC 15 were prepared following the sealed vessel method as outlined by Swart et al. (1991). Powdered sample was reacted with a 50% bleach solution overnight to remove organic matter, rinsed multiple times with deionized water

to remove all traces of bleach, and dried at 70 °C. Due to the large number of samples analyzed,

a sealed vessel was devised wherein the entire batch could be reacted simultaneously with

phosphoric acid and run from a gas bench on the mass spectrometer.

Sealed vessels consisted of Labco Exetainer 12 ml borosilicate glass tubes (part number

539W) with 0.25 dram vials glued to the interior. The vials were placed about half way down

from the top. Standard two-part epoxy was used to affix the vials to the interior of the tubes.

Approximately 1 mg of powdered sample was placed in the bottom of the tubes and a small amount of prepared 100% phosphoric acid was pipetted into each vial. The acid was warmed to

60 °C to help it flow more easily and each vial was filled to about 2/3 full. This step was done

quickly to avoid having the acid absorb excess water from the atmosphere. Immediately after

filling the vial, each tube was placed under a stream of nitrogen gas to expel as much atmosphere

as possible, capped, and placed in a vacuum glove box. The box was sealed and vacuum applied.

Each tube had its cap removed and the batch was allowed to sit under vacuum for 2 hours. After this, vacuum was disconnected and the box flooded with helium gas (helium is the carrier gas for the mass spectrometer). A manual valve on the back of the box allowed for precise control of the

pressure in the box. Pressure was kept as close to atmospheric as possible in order to avoid

overpressure in the tubes. The tubes were capped and placed in a water bath set to 35 °C. The tubes were allowed to equilibrate four hours at which point each tube was carefully tipped on its side to allow the acid to spill out of the vial and run down to the bottom of the tube to react with

the sample. The tubes were left to react overnight in the water bath.

Samples were analyzed on a Finnigan Deltaplus isotope ratio mass spectrometer utilizing a

CTC Analytics CombiPAL gas bench. Ratios are reported with respect to Vienna Standard Mean

Ocean Water (VSMOW) for oxygen and Pee Dee Belemnite (VPDB) for carbon using reference

gases calibrated to NBS-19.

A sample of UCLA Carrera and L-SVEC was run every seventh sample to monitor for

13 18 accuracy. Accepted values for δ CVPDB and δ OVSMOW for UCLA and L-SVEC are 2.49‰ and

28.8‰, and -46.5‰ and 3.45‰, respectively. Analyzed values for UCLA were 2.49 ± 0.314‰

for carbon and 28.81 ± 0.351‰ for oxygen (n = 5). Analyzed values for L-SVEC were -46.6 ±

0.22‰ for carbon and 3.45 ± 0.368‰ for oxygen (n = 5).

Dating

Dating was done using ostracode biostratigraphy, stratigraphic marker beds, and 14C

analysis. 14C samples were taken from core PVC 22 as it displayed excellent preservation of the

organic laminated marl. Four samples approximately 3 mm thick were collected from the organic laminated marl (Figure 21). One additional sample was retrieved from an augered hole a few miles north. This sample was from the same stratigraphic level as the deepest sample in core

PVC 22 and contained the same organic material.

Each sample was placed in a disposable plastic 50 mL centrifuge tube and treated with an

acid-base-acid wash of 10% hydrochloric acid (HCl) and 1.0 M sodium hydroxide (NaOH) to

remove reactive carbonate and organic acids. The first acid wash was allowed to react to completion, which was assumed to have been achieved when visible bubbling ceased. and took no longer than a few minutes. An additional small volume of acid was added to ensure that all carbonate had reacted. Samples were then rinsed once with deionized (DI) water to halt further reaction with the acid, spun for two minutes at 2500 RPM in a Damon IEC HN-S centrifuge, and the supernatant decanted. After this, enough 1.0 M NaOH was added to just cover the sample, the mixture stirred with a glass rod, and left to react for less than 1 minute. DI water was again added to stop the reaction, the sample spun at 2500 rpm, and the supernatant discarded. The final acid wash was done in the same manner as the first except it was allowed to react for less than one minute. This was followed by repeating the rinse step twice. Each sample was screened to isolate the organic material from residual sediment. The resulting organic residue was collected and dried in an oven at 60 °C.

Approximately 5 mg of dry sample was combusted to create CO2 gas. This was done by placing the sample in a quartz glass tube along with a small amount of copper (II) oxide (CuO) and native silver metal (Ag). The CuO is used to provide oxygen for the combustion process while the Ag reacts with any sulfur to form silver sulfide. The tube was evacuated, flame sealed, placed in a muffle furnace set to 900 C, and allowed to react overnight (~12 hours). The resulting

14 CO2 gas was collected and analyzed for C at the Center for Applied Isotope Studies at the

University of Georgia (CAIS-UG) while δ13C was analyzed at BYU.

RESULTS

Overview of Stratigraphy

Pilot Valley cores exhibit the full sequence typical of Lake Bonneville deep water marl

(Oviatt, Habiger, et al., 1994) in addition to a unit beneath the marl which is not typically

considered as part of the Lake Bonneville sequence. Five stratigraphic units have been identified

based on mineralogy, lithology, color, texture, organic content, and other factors (Figure 4).

From oldest to youngest the units are herein designated as units V – I.

Unit V is comprised of oolitic sand and is found in all cores with sufficient depth, typically about 3 meters. This unit displayed some variability in lithology with cores PVC 28 and

PVC 29 having alternating clay and oolitic sand with small of amounts of clastic sand and silt.

When present in other cores unit V is a thick bed of oolitic sand. The thickness of this unit is not well defined but a total thickness of about ~1.5 m has been found near core PVC22 which is located on the eastern margin of the playa. A total thickness of ~1 m has been found in cores in the southern portion of the valley.

Unit IV consists of dark brown, finely laminated organic rich marl. In some cores the unit is separated in the middle by several thin beds of olive gray marl. Unit IV is present in most cores though not all contain a complete section. The depth to this unit varies depending on the location of the core. In the north and west-central part of the playa Unit IV is found at about 2 m and about 3 m on the east-central and southern part of the plays. The thickness of this unit varies

from approximately 0.5 to 1 m depending on the core. The organic matter appears to be oxidized on the west side of the playa causing the color to be lighter gray to white.

Unit III is massive to mottled olive gray marl which can be separated into an upper (III-a) and a lower (III-b) sections in many locations. The boundary separating the sections is typically a discrete sandy layer (described below). Unit III is present playa wide with an average thickness of ~1.5 m. It is thicker to the south where nearly 2 m occurred in one core. White laminations are common in III-b. Disseminated silt along with the occasional pebbles occurs in this unit.

The discrete sandy layer separating units III-a and III-b varies in thickness from several

millimeters to several centimeters. In cores PVC 07 and PVC 29 it is only a few millimeters

thick while in cores PVC 22 and PVC 20 it is several centimeters thick. It is not found in all

cores. It is present in several cores in the eastern, central, southern, and southwestern portions of

the playa.

Unit II is massive to mottled yellow gray marl. Disseminated sand and/or silt are

common especially in the upper portion. Thickness is typically 0.3 – 0.5 m though it reaches

nearly 1 m in the center of the playa at core PVC 29. Depth varies considerably. In cores near the

playa margin it is from 0.5 – 1.5 m deep being deeper further south. Cores from the central

portions of the playa terminate at the surface with this unit.

Unit I is a tan silty to sandy sediments and is found in cores on the western and eastern margins of the playa as well as cores to the south. It is not present in cores from the central

portions of the playa. It varies in thickness from about 0.3 – 1.5 m being thicker on the east than

the west and is thickest in the south. Cores PVC 09, 16, 17, and 18 from the northwest central

portion of the playa were collected from a hardpan and contain abundant euhedral halite crystals

up 5 mm in size to a depth of ~1 m.

Based on five cores an east- west cross-section has been constructed (Figure 5). The

cross-section originated from the base of the Silver Island Mountains and ended near the base of the Pilot Range. From this group of five cores one representative core (PVC 15) was selected for

detailed analysis of the stratigraphy, ostracodes, mineralogy, chemistry, and stable isotopes. Core

PVC 15 was obtained from the east side of the playa at the base of an alluvial fan. Its location

played an important role in the decision to use it for detailed analysis as it was one of the few

cores containing the entire Lake Bonneville sedimentary sequence. The stratigraphic layers in

this core represent sediments from pre-Lake Bonneville, Lake Bonneville, and post-Lake

Bonneville deposition.

Detailed Stratigraphy of PVC 15 core

The basal unit, unit V, 313 cm to 324 cm is predominately white to light gray oolitic sand

with little to no clay except in its upper portion (Figure 6). The ooids are typically rod-shaped but

round ooids are present as well.

Unit IV, which occupies depths of 265 cm to 313 cm, consists of olive gray to dark

brown laminated marl and contains abundant algal filaments (Figure 7and Figure 8). These algal

filaments have been identified in other parts of the Bonneville basin as likely belonging to the

genus Cladophora (Oviatt et al., 1990). Laminations are fine to very fine being on the order of a

few millimeters to <1 millimeter in thickness. The laminations are split by several centimeters of

weakly laminated to bedded olive gray marl. The contact between units V and IV is slightly

gradational.

Unit III is characterized by massive light olive gray to yellow gray marl and occupies

depths from 138 cm to 265 cm (Figure 9). This unit may show weak to very weak laminations

and/or bedding. Mottling is common. Strong white laminations, which contain abundant

aragonite crystals, are present at depths of 237 cm, 240 cm, and 249 cm. Small amounts of

disseminated sand and/or silt occurs in this unit. In several locations are individual, small (<5

cm) stones. These are likely drop stones having been deposited from ice rafts. Unit III can be separated into an upper (III-a) and a lower (III-b) by a distinct sand bed (Figure 10) at a depth of

167 cm. The upper and lower contacts with this bed are sharp.

Unit II occupies depths of 99 cm to 138 cm and consists of yellowish gray massive marl

(Figure 11). Bedding and/or laminations, if present, are weak to moderate. Disseminated silt or

sand is common as is mottling. This unit exhibits a greater amount of silt and sand near the top.

The contact with unit IV is slightly gradational to sharp.

Unit I, from depths of 0 cm to 99 cm, consists of yellowish gray to moderate olive brown

silty to sandy sediments and tends to grade upward from unit II (Figure 12). The lowest portion

of this unit is laminated while the remainder is bedded to massive. At 94 cm depth a sand bed

appears to unconformably overlie laminated sediment. Rod-shaped ooids occur in the sand bed,

though only in minor amounts. Above the sand bed massive silty clay dominates.

Ostracodes

Ostracode fauna follows a typical Lake Bonneville sequence (Figure 13) (Forester,

1987a; Oviatt, 1991; Spencer et al., 1984; Thompson et al., 1990). Valve counts were not

performed. It was simply noted what species were present in each sample.

Unit V is devoid of ostracodes while unit IV is dominated by Limnocythere staplini with

a few Candona sp. Unit III-b contains L. staplini along with L. ceriotuberosa and C. sp. in the

lower portion. The upper portion contains L. ceriotuberosa, C. sp., and C. adunca. Unit III-a

contains L. ceriotuberosa and C sp. along with broken valves from C. sp. Unit II contains L.

sappaensis, Cytherissa lacustris, L. ceriotuberosa, Candona adunca, C. sp. and L. staplini. Unit

I contains C. sp., L. ceriotuberosa, and L. sappaensis at 97 cm depth. From 92 – 72 cm depth

ostracodes valves appear reworked and no ostracodes are seen above 72 cm.

Mineralogy

Mineralogy can be split into two main groups: non-clays and clays. Non-clays are

primarily made up of silicate minerals quartz, orthoclase, oligoclase, carbonate minerals calcite,

aragonite, and dolomite with minor amounts of halite and pyrite. Clay minerals are made up of

smectite and illite with ferruginous smectite and muscovite exhibiting the best fit to measured

patterns.

Quartz, orthoclase, and oligoclase (silicates) all showed a good fit to measured XRD patterns. They appear to generally vary directly with each other (Figure 14). Abundance in unit

V was very low for all three being from 0 to a few weight %. The beginning of unit IV showed a

large spike from ~0% to 29.5%, 23.8%, and 13.7% for all three silicates after which all three

dropped rapidly by almost one third. The remainder of units IV – III-b showed an increasing

trend in quartz from ~15% - 36% before stabilizing to ~29% through the remainder of unit III.

Both orthoclase and oligoclase tended to hover around 10% and 6%, respectively through units

IV and III. A decrease in the abundance of all three by one half to one third was observed at the beginning of unit II followed by an increase to abundances around 20%, 10%, and 7%, respectively, which continued through unit I. Their average abundances through the entire core were 21.4%, 10.9%, and 5.6%, respectively.

Calcite, aragonite, and dolomite (carbonates) have average abundances of 18.7%, 13.7%,

and 7.2%, respectively. The carbonate minerals were split into two separate groups: primary and

secondary (Mueller et al., 1972). Calcite and aragonite are primary carbonate minerals, which

precipitated out of the water column. Dolomite is secondary and likely originated from the

surrounding mountains as clastic material. It is unlikely that any dolomite present is due to

diagenetic processes.

Calcite abundance varied from 2.5% to ~5% in unit V. In unit IV it was 5.4% at 309 cm

increasing to 16.7% at 304 cm depth. Calcite rose to ~ 20% in the middle of unit IV before

dropping to ~13% near the top. In units III-b and III-a it showed a relatively stable average

abundance of ~20% with three exceptions. At 266, 165 and 139 cm depth the calcite abundance

was 13.9%, 26.2%, and 28.7% which correlate with the bottom of unit III-b, the sand bed, and the top of III-a, respectively. In unit II calcite was 13.1% at 134 cm after which it rises to ~18% followed by a gradual rise to ~21%. Unit I calcite abundance remains ~21% from 97 – 36 cm after which it decreases to ~16% (Figure 15).

Aragonite showed maximum abundance in unit V where it was >90% (Figure 15). In unit

IV it ranged from 4.5% at 309 cm depth after which it increased quickly to >30% at 304 cm with

considerable variability. Unit III-b showed greater abundance in the lower portion than the

middle and upper. At the sand bed separating units III-b and III-a aragonite jumped from 3% to

nearly 10% then dropped to ~1%. Unit II showed a sudden increase to >55% with a rapid

decrease to <15% just before unit I. Unit I showed a rise in aragonite from ~15% to 22% at 99 –

87 cm depth after which it fell quickly to ~4% where it remained through unit I. Figure 16 plots

normalized values for aragonite and calcite by summing the absolute values of each and dividing

the absolute value by the total.

Dolomite showed much lower overall abundance than either calcite or aragonite ranging

from 1.4% to 13.9%. It was moderately well correlated with quartz (R2 = 0.41). The lowest

abundance of dolomite was in unit V where it averaged 2%. It showed a large increase to 9.9% at

the bottom of unit IV (309 cm) then decreased to ~5% for the remainder of that unit. Unit III-b showed an average abundance of 8.5% with unit III-a being 6.1% while at 165 cm just above the sand bed dolomite was 10.4%. Dolomite in unit II started at ~4% but quickly increased to 10.9% at near the contact with unit I. Abundance in unit I from 97 – 72 cm averaged 10.8% while the portions above 72 cm decreased abruptly to ~5%.

Other non-clay minerals include halite and pyrite. A small amount of halite was found sporadically in four samples and was likely the result of these samples not having been rinsed

thoroughly during initial preparation. Pyrite was found in units IV and III-b with an average abundance of 1.1%.

Clay minerals were dominated by two phases, 2:1 and 1:1, representing smectite and illite. The best fit patterns to internal standards were ferruginous smectite with lesser amounts of muscovite. Clay mineral abundance typically mirrors that of silicates though the values differ. It

should be noted that RockJock11 does not analyze well for clay minerals since their maximum

two-theta peaks typically occur below the 20° two-theta lower limit of RockJock11 (Eberl,

2003). However, as a qualitative tool RockJock11 will allow the separation of the clay mineral

portion from the non-clay mineral portion.

Bulk Chemistry—Major and Trace elements

Silicon averages 42.7% for the whole core. In unit V it varied from a low of 7.5% to

18.8% before it increased to back the average value in units V and IV. There was a sudden drop

from ~ 44% to 29.9% at the boundary between units II and III and gradual rise to about 42% by

the end of unit II. In unit I at 92 cm depth it was 37.8%, gradually increased to 39.2% by 82 cm

and gradually decreased to 35% at a depth of 72 cm. It increased abruptly to ~49% above 72 cm.

Calcium increases at this same depth to 24.9 % from 16.4 % and gradually falls off to around

17% by the top of unit II. Magnesium levels remain relatively consistent hovering around 3%

though units II, IV, and V. The lowest values are in unit VI they range from <1% to 1.7%. Mg

begins to rise in unit II after a slight drop near the top of unit IV. In unit I it ranges from a low of

4.4 % to around 8% (Figure 17).

Strontium exhibits a large range of values varying from a low of 295 ppm to a high of

nearly 3000 ppm with an average of ~730 ppm. Strontium concentration in unit V was above

2100 ppm. This is not surprising as this unit contains oolitic sand which is composed of >90%

aragonite. Strontium averages 844 and 415 ppm, respectively, in units IV and III with greater

variability in unit IV than unit III. The highest strontium concentration occurs in unit II at a depth of 134 cm where it reaches nearly 3000 ppm before rapidly decreasing to 680 ppm by a depth of

102 cm. Unit I shows a slight rise from ~750 ppm to 946 ppm from 97 to 87 cm depth after which is falls to an average of 365 ppm for the remainder of the unit (Figure 17).

Total Inorganic Carbon and Total Organic Carbon

Total inorganic carbon (TIC) displays a fair amount of variability (Figure 18). At the base of the core TIC approaches 50% in unit V before rapidly decreasing to ~6.5% at a depth of 309 cm. TIC remains between 9% and 17% between 304 cm and 170 cm in units IV and III. Above

170 cm TIC starts to vary more with values ranging between 7.7% and 25% in units II and I.

Average TIC is around 15.6% for the entire core. However, neglecting the three samples from unit V, TIC averages 14.1%.

Total organic carbon (TOC) exhibits less variability than TIC (Figure 18). The lowest

TOC value was ~4% in unit V below 309 cm. From 304 cm to 266 cm (unit IV) TOC varied from 5.8% to 11.5% with an average of 8.6%. In unit III from 261 cm to 165 cm TIC was within a relatively narrow range of about 5% to 6%. In units II and I TIC varied from 3.8% to 11.3%.

Most variability appeared to occur between 149 cm and 41 cm. TOC varied little from 36 cm in unit I to the top of the core.

Stable Isotopes— δ18O and δ13C

Isotope δ18O varied from a high of 27.1‰ in unit V to a low of 15.3‰ near the top of

unit I. Units V and IV show a bit of oscillation. Unit IV shows a slight trend toward more depleted δ18O up through a depth of 221 cm where it became more enriched until a depth of 167

cm (unit III). At this point δ18O values decline by nearly 3‰ to a value of 18 ‰ before showing

an increase to 25.5‰ just after passing into unit II. Unit II shows a general decline in δ18O values

as does unit I. At the boundary between units II and I δ18O increases from 20.6‰ to 24.0‰. δ13C

varies from a high of 3.2‰ to a low of -3.4‰. It also displays the same general trends as δ18O through each stratigraphic unit. Stable isotopes were highly correlated (R2 of 0.66) (Figure 19).

Dating

Biostratigraphy is a useful tool for correlating similar age deposits. No formal time series

has been made for ostracodes in the Bonneville basin but they are still useful in understanding

changes in water chemistry which can be correlated to changes in lake level through time. The

ostracodes in core PVC 15 fall in line with published work on Lake Bonneville marl (Forester,

1987b; Oviatt, 1991; Oviatt, McCoy, et al., 1994; Spencer et al., 1984; Thompson et al., 1990).

Four14C ages were determined form unit IV in core PVC 22 at depths are 293, 307, 312

and 320 cm (Figure 21). These represent the top, two intermediate, and bottom locations within

unit V in this core. These ages were obtained to better understand the timing of deposition of this

unit. Ages for these samples from oldest to youngest, in 14C years BP, are 22433 ± 61, 20972 ±

55, 19320 ± 50, and 15835 ± 40. An additional sample, obtained from an augered hole a few

miles north from near the bottom of unit IV was obtained as well. Its age was 22923 ± 53 which

agrees well with the oldest reported age from PVC 22.

DISCUSSION

Unit V

The mineralogy of oolitic sand, >90% aragonite, suggests formation in shallow, saline

water. Absences of ostracodes also indicate elevated salinity. The δ18O composition of carbonate, averaging of 26.6‰, is among the most enriched found and is attributed to elevated evaporation due to a high surface area to volume ratio. The conditions surrounding how and why these ooids

formed in Pilot Valley are problematic. The thickness of ooids in this unit varied considerably from a bed nearly 2 m thick on the east-central margin of the playa to alternating laminated to bedded ooids and clay in the central and west-central portions of the playa. Beds of recent ooids have been documented and studied in Great Salt Lake by Pedone and Norgauer (2002). Great

Salt Lake is the most recent remnant of Lake Bonneville, is highly saline, and quite shallow

(Arnow & Stephens, 1990; Langbein, 1961). Using modern-day Great Salt Lake as an analog for conditions under which ooids formed in Pilot Valley unit V represents deposition in a shallow, saline lake, which pre-dates Lake Bonneville. The Pilot Valley lake was no more than a few meters deep.

Unit IV

Unit IV contains the algal laminated marl and occurs with a thickness of several 10’s of centimeters. It was present in all cores with sufficient depth and was continuous across the entire playa. In some cores it appeared the organic material had been oxidized. However, each core that contained this unit had algal laminations to some degree while most displayed excellent preservation.

The base of this unit, at a depth of 309 cm, showed a large increase in clastic material represented by silicates and dolomite from XRD analysis. It is much higher than the sample immediately above at a depth of 304 cm and stands in stark contrast to the mineralogy of the sediments immediately below where little to no silicates or dolomite are present. The reason for this is not well understood. Oviatt et al. (1990) correlated this unit with the transgressive phase of

Lake Bonneville known as Stansbury which contains the Stansbury Oscillation. This was a time in which temperatures were cooler with less precipitation than at later stages (Madsen et al.,

2001; Nelson et al., 2005). One possible explanation is that precipitation that did fall may have

rapidly eroded weathered material from the surrounding mountains to the rising lake. This would

manifest itself as an increase in clastic material. The immediate drop is explained in a similar

manner. If there was insufficient erosive force to transport weathered material to the lake it

would have stayed essentially in place until such time that erosion could transport it to the lake

near the end of unit V. It may also be this material was engulfed in rising water levels associated

with this period of the lake’s history.

Pilot Valley shoreline tufa enriched in δ18O have been correlated with increased

evaporation while more depleted δ18O has been correlated with decreased evaporation (Nelson et

al., 2005). The manner in which δ18O oscillated through unit IV (Figure 20) shows that temperature, and most likely precipitation, was fluctuating to some degree. During this time water level was also fluctuating through the Stansbury Oscillation (Oviatt et al., 1990; Oviatt et al., 1992) in response to changing climate. δ13C oscillated as well through unit IV and may be the result of changes in the amount of organic productivity with periods of greater productivity leading to more enriched values and less productivity leading to more depleted values

(McKenzie, 1985). In this case changes in δ13C can be correlated to an increase in the apparent

abundance of organic material in the cores at the correlated lake level.

Oviatt et al. (1990) inferred that algae from unit IV were mats floating near shore. They

stated that these mats floated around on the surface and eventually settled to the bottom of the

lake where they mixed with lake-bottom sediment. This is based on investigations of outcrops in

the vicinity of Bear River City, UT, which is located in the northeastern part of the Bonneville

basin as well as data from cores obtained by Spencer et al. (1984). Oviatt et al. (1990) also provide an alternate hypothesis that these were benthic algae which lived in the photic zone on the bottom of the lake during the low stand of the Stansbury oscillation. They dismiss this,

however, citing the algal laminated marl in core C of Spencer et al. (1984) would have been

under nearly 100 m of water at the lowest point in the oscillation and may have been below the

photic zone. Given the elevation of unit IV in core C (~1267 masl) of Spencer et al. (1984) this is not an unreasonable conclusion. However, given the extent of this unit, as seen in Pilot Valley cores, it seems unlikely these were floating mats. For that to be the case the mats would have had to cover the entire aerial extent of the lake in Pilot Valley at some time or they would have had to

been so extensive and prolific that individual mats would eventually cover the entire lake bottom

in Pilot Valley. Both these scenarios seem highly unlikely. The hypothesis that these were not

floating mats but benthic algae living on the lake bottom is much more likely.

The elevation of Pilot Valley averages 1295 masl while Bear River City sits at ~1290 masl. The algal laminated marl in Pilot Valley is about three meters beneath the surface placing it around 1292 masl. Using an elevation of 1360 masl for the average level of the lake during the

Stansbury interval, the depth of the lake in Pilot Valley at the time the algal laminated marl was

deposited would have been about 70 m. This indicates that the lake bottom was in the photic

zone. This also means that the algal marl near Bear River City described by Oviatt et al. (1990)

likely was benthic as well. It is probable that other areas of the Bonneville basin at similar

elevation have the same algal laminated marl, which originated as benthic algae.

The principal ostracode seen in unit V is Limnocythere staplini which matches up well

with the interpretations of Oviatt (1991), Spencer et al. (1984), and Thompson et al. (1990). L.

staplini is generally more tolerant of saline water, which may indicate a relatively shallow lake.

However, the lake was likely deeper than during the time interval when unit V was deposited. In

the upper portions of this unit Candona sp. is present. This species of ostracode is less tolerant of

high salinity levels generally preferring low TDS water. This indicates that lake level had risen

and become less saline.

14C ages of samples taken from unit IV in core PVC 22 bracket the timing of this unit as being from 22433 ± 61 14C years BP to15835 ± 40 14C years BP. These ages place unit IV well within the radiocarbon chronology of Oviatt et al. (1992) and the chronologies of Benson et al.

(2011) and Spencer et al. (1984) representing the Stansbury Oscillation. Unit IV is interpreted as equivalent to the Stansbury level, which would contain the Stansbury oscillation.

Unit III

Unit III is comprised of massive to weakly bedded and mottled olive gray marl.

Ostracode fauna consisted of benthic varieties, which were intolerant of high salinity levels while the relative lack of laminations and bedding are indicative of bioturbation (Spencer et al., 1984).

TOC is relatively stable through this unit with an average of 6.17% indicating relatively stable productivity in the lake.

Carbonate mineralogy of the sediments show that water chemistry was relatively stable.

An exception to this can be found at depths between 237 cm and 249 cm. Several distinct white laminations are seen between these depths. Smear slides prepared from this section contain

abundant aragonite crystals. XRD analysis shows greater amounts of aragonite as well where it

rises abruptly from levels around 8% to more than 20% and falling just as quickly back to around

5%. Strontium shows an abrupt rise in this same interval from ~450 ppm to a high of ~780 ppm

and back to ~360 ppm. Calcium exhibits the same general trend as strontium while magnesium

displays remarkably consistent levels of around 3%. The exact cause of these white laminations

is not known but it is possible that lake level, and by extension volume, declined causing the

magnesium to calcium ratio to increase due to increased input from the Sevier arm of the lake

where Sevier river water has a higher Mg/Ca ratio (Oviatt, Habiger, et al., 1994). Stable isotopes tended to oscillate over a relatively narrow range in unit III showing a slight trend from relatively enriched to depleted to enriched values (Figure 20).

The sandy bed in unit III is problematic. It could have been caused by a storm, which

washed coarse grained material into the lake. Mineralogy showed a slight rise in both calcite and

aragonite at the depth of the sandy bed and may indicate a freshening of lake water. A decrease

in the amount of oscillation of stable isotopes also indicates water chemistry changed in some

manner. The thickness of the sand bed tended to increase closer to the playa margin. It may also

be the sand bed correlates to the Bonneville flood which lowered lake level by ~100 m over the

course of several weeks to a year (O'Connor, 1993; Oviatt, 1987, 1991; Oviatt, McCoy, et al.,

1994) and represents the change from the Bonneville to the Provo level. During this period

massive quantities of groundwater would likely have been discharged into the lake and could

have transported and deposited clastic material into the lake, especially in the littoral zone. If this

is the case smaller sub-basin, such as Pilot Valley, may have recorded this event. Oviatt et al.

(1992) place the age of this event at 14.5 14C years BP.

Unit IV represents open water conditions of a deep lake. This includes the latest

transgressive phase up to the Bonneville level. The sand bed may also record evidence of the

Bonneville flood marking a change to the regressive phase of the Lake Bonneville associated

with the Provo level. However, it is unclear just what the sand bed represents.

Unit II

Unit II marks a distinct transition in core PVC 15 which is expressed as a change in color

from light olive gray marl to yellowish gray marl. The data indicates a major shift in water

chemistry, and by extension, water balance. The mineralogy at this transition shows a dramatic

change in carbonates, silicates, and clay. Just prior to this transition calcite is 28.7% and

aragonite is 0.9%. After the transition calcite drops to 13.1% and aragonite increases to 55.6%.

Silicates show a dramatic drop as does clay. Strontium exhibits a rise from 532 ppm to nearly

3000 ppm while magnesium, which had been relatively stable at around 2.7%, drops to 1.9%.

The rise in strontium helps explain why aragonite increases so dramatically as it preferentially

will replace calcium in high-magnesium calcite, causing aragonite to form (Mueller et al., 1972).

Isotopes of carbon and oxygen both exhibited enrichment of several per mil followed by a trend

toward more depleted values (Figure 20).

Ostracode fauna change as well. Cytherissa lacustris, not seen to this point in deeper

portions of the core, appears just after the transition and prefers cold, deep, freshwater bodies. C.

lacustris has been correlated with the Provo level of Lake Bonneville in other parts of the

Bonneville basin (Charles G. Oviatt, personal communication, 2012).

The changes recorded in unit II, coupled with the sand bed from unit III, presents a

problem with assigning the advent of the Provo level in these cores. On one hand is the sandy

bed in unit III, which may represent the Bonneville flood. The drop in water level after the flood,

and after the lake stabilized, is the Provo level. There would be an expected change in water

chemistry with such a large loss of lake water volume and the increase in carbonate at the level of the sandy bed appears to show this. However, mineralogy also changes dramatically with the

transition from unit III to unit II. Additionally, C. lacustris has been correlated with the Provo level and doesn’t appear in the Bonneville basin until unit II. So the question becomes is the sandy bed or is the boundary between units III and II representative of the change from

Bonneville to Provo levels? The answer is elusive in these cores and may be somewhere between the sandy bed and the start of unit II. Given the location and restricted nature of the Pilot Valley

sub-basin, one possibility is that changes in water chemistry may have lagged behind changes in water level. However, additional work would need to be done to prove whether this is the case.

Obtaining 14C ages from bulk organic or inorganic carbon at the transition would prove helpful in determining the timing of events around this transition.

Unit I

Unit I exhibits a change in lithology from principally clay to silty/sandy clay to silt and sand. Unit I was slightly laminated to bedded at its contact with unit II indicating water level was deep enough to deposit laminated sediments. At of 94 cm depth was an apparent unconformity.

The bedding below this depth appeared slightly inclined and is juxtaposed below a 14 cm thick sand bed. It is possible the inclined bedding is an artifact of coring, however, the placement of the bedding against the sand indicates an erosional surface. Rod shaped ooids are contained in the sand bed, though not in large amounts, and continue to be seen to a depth of 85 cm at which point the sediment changes to silty clay.

Mineralogy doesn’t change dramatically at this transition though silicates do rise a few weight percent with drops of a couple weight percent in calcite and aragonite. Dolomite rises about 1.5%. Clays show a marked decrease from 18.5% to 11.5%. Strontium exhibits a rise which continues to the middle portion of the unit. Salinity resistant ostracodes Limnocythere cerituberosa and L. sappaensis are present only at the very base of the unit with reworked valves being observed above 92 cm depth. Ostracode valves disappear entirely by 72 cm depth.

The above data indicate the lake continued to regress from Provo level and possibly receded entirely from Pilot Valley followed by a small transgression. Lower water levels will decrease the elevation at which the shorezone is found. Within the shorezone energy levels are higher which would more easily move coarser material and deposit it as sand beds. The presence

of salinity tolerant ostracodes and rod-shaped ooids also suggests lower water level and increased salinity though it is unlikely the lake stabilized at this level for long given the decreased amount of ooids in unit I compared to unit V. The upper portion of unit I at a depth of about 41 cm was comprised principally of silt and sand and was devoid of any ostracodes. It also appears to lack any stratigraphic features indicating deposition in water. It is likely all observed sediments from this depth upward are past the last regressive phase of Lake Bonneville as recorded in Pilot Valley.

Unit I is interpreted at representing the latest regressive phase of Lake Bonneville on though modern Holocene time, including the Gilbert level with possible evidence showing the lake regressing, transgressing, and regressing again in Pilot Valley. The elevation of the Gilbert level was ~1300 masl which would make the lake about 5 m deep in Pilot Valley.

CONCLUSIONS

1. The bulk of the shallow stratigraphy of Pilot Valley playa is comprised sediments

deposited during the open water phase of Lake Bonneville. In addition, pre-Lake

Bonneville sediments are present in the deepest portions of cores taken from Pilot Valley.

Five major units have been identified. They are as follows from deepest to most shallow:

a. Unit V represents deposition in a shallow, saline lake, which pre-dates Lake

Bonneville. The Pilot Valley lake was no more than a few meters deep. It is

comprised principally of oolitic sand..

b. Unit IV: comprised of highly organic algal laminated marl and represents the

transgressive phase of Lake Bonneville associated with the Stansbury oscillation.

Dates obtained from algae in this unit range from 22433 ± 61 14C years BP

to15835 ± 40 14C years BP. In Pilot Valley the algae occurred at benthic mats

covering the lake bottom.

c. Unit III: comprised of massive to weakly bedded and mottled marl. It represents

open water conditions of a deep lake. The discrete sandy bed is problematic. It

may represent a storm event or possibly the Bonneville flood.

d. Unit II: a transition from olive gray marl to yellow gray marl accompanied by

abrupt changes in mineralogy, chemistry and stable isotopes. The exact timing is

problematic but it may represent a change from Bonneville to Provo levels

causing it to fall within the regressive phase of the Lake Bonneville.

e. Unit I: a transition from clayey marl to silty and sandy sediments represents the

latest regressive phase of Lake Bonneville on through modern time and the

deposition of Holocene sediments. This unit incorporates the Gilbert level on

through a shallow, somewhat saline lake, as indicated by the presence of ooids as

well as laminations in the lower portions of this unit. The presence of a probable

unconformity indicates the lake may have dried up completely before filling to the

Gilbert level. This unit also preserves the transition to a playa environment as

illustrated by the presence of euhedral halite from the hardpan.

2. Four 14C ages constrain the timing of deposition of the algal laminated marl (unit V) from

22433 ± 61 14C years BP to15835 ± 40 14C years BP. This is in addition to one 14C age,

obtained at the base of unit V from an augered hole a few miles north, of 22923 ± 53 14C

yrs. BP.

3. The mineralogy and chemistry of core PVC 15 record changes in water which may be

correlated different lake levels.

4. Ostracode analysis from Pilot Valley is consistent with published data and shows good

correlation with other published work on the Bonneville basin.

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FIGURES

Figure 1. Map showing major Lake Bonneville levels and study area.

Figure 2. Pilot valley and surrounding area.

Figure 3. Core locations in Pilot Valley. Cross-section is represented by bold black line.

Figure 4. Schematic stratigraphic column illustrating generalized marl section of sediments from Pilot Valley playa. Column and sections are not to scale.

Figure 5. Stratigraphic cross-section across Pilot Valley. Depth is in centimeters Cores PVC 15, 22, and 28 each contain the full sequence of units I – V. Core PVC 29 does not contain unit I while core PVC 20 does not contain units IV and V. Core locations are shown on Figure 3.

Figure 6. Unit V: PVC 15 oolitic sand.

Figure 7. Unit IV: PVC 15 algal laminated marl.

25 μm

Figure 8. Photo micrograph of algae filaments from algal laminated marl of unit IV.

Figure 9. Unit III: PVC 15 olive gray massive marl with white aragonitic laminations.

Figure 10. Sand bed in PVC 20 separating units III-a and III-b.

Figure 11. Unit II: PVC 15 yellow gray massive marl. Yellow gray marl on the left is unit II while olive gray marl on the right is unit III.

Figure 12. Unit I: PVC 15 laminated silt and sand bed. Laminated silty clay is on the right. Ooids appear in sand bed at 42 cm which is 94 cm cumulative depth.

Figure 13. Bar graph of ostracodes first and last appearance vs. depth in core PVC 15. Valve counts were not made. It was simply noted whether valves were present.

Carbonate Dolomite Silicates Clays 0 0 0 0

50 50 50 50

100 100 100 100

150 150 150 150

Depth (cm) 200 200 200 200

250 250 250 250

300 300 300 300

0.0 100.0 200.0 0.0 10.0 20.0 0.0 50.0 100.0 0.0 50.0 Weight % Weight % Weight % Weight %

Figure 14. PVC 15 core depth vs. mineralogy. Carbonate is combined calcite and aragonite. Silicates is combined quartz, orthoclase and oligoclase.

Calcite Aragonite 0 0

50 50

100 100

150 150

Depth (cm) 200 200

250 250

300 300

0.0 20.0 40.0 0.0 50.0 100.0 Weight % Weight %

Figure 15. PVC 15 depth vs. calcite and aragonite.

Figure 16. Normalized calcite and aragonitevs. depth in core PVC 15. Normalized values are calculated by summing the values of all carbonate minerals and dividing the values of calcite and aragonite by that total.

Calcium Silicon Strontium Magnesium 0 0 0 0

50 50 50 50

100 100 100 100

150 150 150 150 Depth (cm) 200 200 200 200

250 250 250 250

300 300 300 300

0.0 20.0 40.0 0.0 50.0 100.0 0 2000 4000 0.0 5.0 10.0 Weight % Weight % Weight % Weight %

Figure 17. Plots of XRF results for calcium, silicon, strontium, and magnesium in PVC 15. Plots are depth vs. weight percent (%).

III-a

III-b

Figure 18. PVC 15 TIC and TOC as a function of depth. Black dots are TIC and red squares are TOC. TIC and TOC are given in weight %, depth is in centimeters. Dashed lines are approximate boundaries between stratigraphic units. Bold dotted line is sand bed which represents the Bonneville flood. TIC exhibits a fair amount of variability while TOC exhibits less overall variability.

4.0

3.0

2.0

1.0

VPDB 0.0

δ13C -1.0

-2.0 R² = 0.6613

-3.0

-4.0 15 17 19 21 23 25 27 29

δ18OVSMOW

13 18 Figure 19. Scatter plot of δ CVPDB vs. δ OVSMOWfrom PVC 15.

0 0

50 50

100 100 II

150 III-a 150

Depth (cm) 200 200 III-b

250 250

IV 300 300

350 350 12.0 16.0 20.0 24.0 28.0 -4.0 -2.0 0.0 2.0 4.0

δ18OVSMOW ‰ δ13CVPDB ‰

18 13 Figure 20. Depth vs. δ OVSMOW and δ CVPDB in PVC 15. Dashed lines are approximate boundaries between stratigraphic units I – V. Bold dotted line is sand bed separating units III-a and III-b.

Figure 21. 14C sample locations from core PVC 22.

TABLES

UTM* Core ID Zone Easting Northing PVC 01 12 T 263946 4557459 PVC 02 12 T 252796 4556754 PVC 04 12 T 247111 4537769 PVC 05 11 T 244537 4531911 PVC 06 12 T 253808 4534994 PVC 08 12 T 263881 4549798 PVC 09 12 T 258396 4552267 PVC 11 12 T 250813 4536102 PVC 12 12 T 257918 4560010 PVC 13 12 T 251412 4551228 PVC 14 12 T 265555 4553648 PVC 15 12 T 264930 4545077 PVC 16 12 T 257483 4547932 PVC 17 12 T 259999 4553841 PVC 18 12 T 255288 4551677 PVC 19 12 T 244242 4533806 PVC 20 12 T 241242 4533605 PVC 21 12 T 244873 4535453 PVC 22 12 T 258842 4541197 PVC 25 12 T 253847 4532270 PVC 28 12 T 251063 4544106 PVC 29 12 T 254080 4543172 * WGS 84 datum

Table 1. UTM coordinates of core locations in Pilot Valley.

Unit Distinguishing feature Other features Depth (cm) I tan silt to sand may exhibit weak laminations 0 - 99 II massive, yellowish gray marl weakly laminated; silt/sand 99 - 138 III-a massive, olive gray marl sand bed at bottom 138 - 167 several white laminations, sand bed III-b massive, olive gray marl at top 167 - 265 olive gray bedded marl in middle of IV dark brown laminated marl unit 265 - 313 V white to gray oolitic sand little to no clay 313 - 324

Table 2. Table of stratigraphic units from Pilot Valley playa with distinguishing features as well as other minor features. Depth intervals are for core PVC 15.

Sample Cumulative Sample Cumulative Sample Cumulative Sample Cumulative Section Section ID top depth depth ID top depth depth 1 0-2 0 15 6 31 6-8 150 25 175 2 0-2 0 20 11 32 6-8 150 30 180 3 0-2 0 25 16 33 6-8 150 35 185 4 0-2 0 30 21 34 6-8 150 40 190 5 0-2 0 35 26 35 6-8 150 45 195 6 0-2 0 40 31 36 6-8 150 50 200 7 0-2 0 45 36 37 6-8 150 55 205 8 0-2 0 50 41 38 6-8 150 60 210 9 2-4 52 20 72 39 8-10 206 5 211 10 2-4 52 25 77 40 8-10 206 15 221 11 2-4 52 30 82 41 8-10 206 20 226 12 2-4 52 35 87 42 8-10 206 25 231 13 2-4 52 40 92 43 8-10 206 30 236 14 2-4 52 45 97 44 8-10 206 35 241 15 2-4 52 50 102 45 8-10 206 40 246 16 2-4 52 55 107 46 8-10 206 45 251 17 2-4 52 60 112 47 8-10 206 50 256 18 4-6 99 15 114 48 8-10 206 55 261 19 4-6 99 20 119 49 8-10 206 60 266 20 4-6 99 25 124 50 10-12 264 5 269 21 4-6 99 30 129 51 10-12 264 10 274 22 4-6 99 35 134 52 10-12 264 20 284 23 4-6 99 40 139 53 10-12 264 25 289 24 4-6 99 45 144 54 10-12 264 30 294 25 4-6 99 50 149 55 10-12 264 35 299 26 4-6 99 55 154 56 10-12 264 40 304 27 4-6 99 60 159 57 10-12 264 45 309 28 6-8 150 10 160 58 10-12 264 50 314 29 6-8 150 15 165 59 10-12 264 55 319 30 6-8 150 20 170 60 10-12 264 60 324

Table 3. Sample depths from core PVC 15. Depth at which each sample was collected within each section of the core is labeled “Sample depth” while total depth is labeled “Cumulative depth”. Alternating colors represent different stratigraphic units. Double line is sand bed separating units III-a and III-b.

Depth in Wt. % Wt. % Depth in Wt. % Wt. % Wt. % Wt. % core organic inorganic core organic inorganic total C total C (cm) C LOI550 C LOI950 (cm) C LOI550 C LOI950 6 6.49 10.05 16.54 175 5.77 13.22 18.98 11 6.98 8.76 15.74 180 6.52 14.67 21.19 16 5.62 11.51 17.13 185 6.21 11.99 18.20 21 5.95 12.37 18.32 190 6.51 12.84 19.34 26 6.39 8.72 15.11 195 6.64 12.18 18.82 31 6.04 7.72 13.76 200 5.61 12.26 17.87 36 6.17 12.84 19.01 205 6.15 12.48 18.63 41 6.44 12.16 18.60 210 6.08 11.13 17.22 72 4.62 24.56 29.18 211 6.70 11.44 18.13 77 10.84 15.99 26.83 221 5.98 9.18 15.16 82 11.31 13.34 24.65 226 6.84 11.32 18.16 87 3.83 25.16 28.98 231 4.08 11.31 15.40 92 4.73 22.40 27.13 236 5.99 16.53 22.52 97 4.13 19.84 23.97 241 6.21 14.03 20.24 102 6.58 17.61 24.19 246 6.30 15.68 21.98 107 7.39 15.93 23.32 251 6.07 14.47 20.53 112 6.67 16.29 22.96 256 7.09 10.69 17.78 114 10.09 16.07 26.15 261 6.19 9.42 15.61 119 8.34 20.89 29.23 266 11.53 12.95 24.48 124 10.53 20.43 30.95 269 8.50 15.99 24.50 129 9.65 22.21 31.85 274 7.63 14.57 22.20 134 9.01 24.28 33.29 284 5.89 13.89 19.78 139 7.66 14.48 22.14 289 7.27 17.05 24.32 144 8.96 10.21 19.18 294 9.63 9.98 19.61 149 7.40 12.92 20.32 299 9.54 16.85 26.39 154 7.13 10.30 17.43 304 9.58 14.88 24.47 159 7.20 9.49 16.70 309 4.52 6.54 11.05 160 7.19 11.36 18.55 314 4.66 36.22 40.88 165 5.80 19.13 24.93 319 4.05 46.30 50.35 170 6.36 13.75 20.11 324 3.96 47.21 51.17

Table 4. Table of TIC and TOCvalues in weight % . LOI550 represents TOC and LOI950 represents TIC. Different stratigraphic units are shown by alternating shaded areas. Double line is sand bed separating units III-a and III-b.

APPENDIX A XRF results from PVC 15

Sample Depth Major elements (oxides) ID (cm) SiO2 TiO2 Al2O3 Fe2O3 MnO MgO CaO Na2O K2O P2O5 1 6 48.91 0.44 9.57 2.95 0.06 7.94 9.63 1.46 2.17 0.21 2 11 50.11 0.44 9.86 3.02 0.06 7.58 8.98 1.67 2.23 0.21 3 16 49.23 0.42 9.25 2.67 0.06 6.32 11.03 1.41 2.15 0.20 4 21 48.01 0.39 9.37 2.85 0.06 6.21 10.86 1.41 2.20 0.20 5 26 51.25 0.46 10.08 2.94 0.06 7.31 8.60 1.59 2.28 0.20 6 31 52.78 0.42 10.47 2.94 0.07 5.99 8.73 2.16 2.36 0.20 7 36 45.76 0.42 8.85 2.80 0.06 7.06 12.24 1.34 2.13 0.21 8 41 46.17 0.40 9.07 2.96 0.06 7.13 11.82 1.25 2.21 0.22 9 72 34.98 0.23 5.31 1.25 0.03 5.65 20.66 1.10 1.26 0.15 10 77 36.10 0.29 5.84 1.69 0.04 8.23 17.74 1.61 1.31 0.17 11 82 39.16 0.32 6.57 1.98 0.04 6.91 16.39 2.17 1.49 0.17 12 87 35.70 0.28 4.96 1.16 0.03 4.62 21.62 1.04 1.22 0.18 13 92 37.67 0.29 5.61 1.53 0.04 4.73 20.09 1.20 1.37 0.17 14 97 42.48 0.33 6.48 1.70 0.04 4.38 17.53 1.17 1.59 0.16 15 102 41.15 0.32 7.16 2.24 0.05 4.32 17.26 1.34 1.67 0.17 16 107 42.56 0.35 7.36 2.36 0.05 3.77 16.79 1.42 1.73 0.17 17 112 43.43 0.34 7.03 2.18 0.04 3.87 16.82 1.36 1.65 0.17 18 114 37.55 0.31 6.86 2.54 0.05 2.81 20.16 1.66 1.55 0.19 19 119 34.19 0.29 6.29 2.25 0.04 2.52 21.94 1.45 1.42 0.19 20 124 32.55 0.22 5.49 2.19 0.04 2.23 22.77 1.94 1.24 0.17 21 129 31.55 0.22 4.95 2.23 0.05 1.96 24.24 1.40 1.13 0.16 22 134 29.87 0.22 4.83 1.94 0.11 1.89 24.89 1.36 1.11 0.13 23 139 43.96 0.31 8.14 2.42 0.10 2.40 16.39 1.81 1.95 0.16 24 144 48.18 0.41 9.24 2.98 0.05 2.68 12.72 2.10 2.11 0.19 25 149 46.72 0.41 9.13 2.67 0.05 2.67 13.89 1.72 2.09 0.19 26 154 50.51 0.40 9.74 3.24 0.04 2.71 11.24 1.92 2.25 0.20 27 159 51.34 0.45 10.17 3.21 0.04 2.77 10.81 1.83 2.29 0.21 28 160 49.09 0.40 9.36 2.81 0.04 2.70 12.71 1.71 2.10 0.20 29 165 41.14 0.29 7.06 1.78 0.04 3.04 17.51 1.25 1.71 0.15 30 170 47.56 0.42 8.85 2.34 0.04 2.87 13.73 1.57 2.11 0.18 31 175 48.26 0.42 8.99 2.61 0.06 2.98 13.43 1.70 2.13 0.18 32 180 45.33 0.40 8.57 2.36 0.06 3.26 14.90 1.53 2.10 0.19 33 185 48.45 0.41 9.07 2.88 0.06 3.23 13.64 1.50 2.19 0.19 34 190 46.52 0.37 8.77 2.98 0.07 3.34 14.59 1.56 2.10 0.19 35 195 47.46 0.42 8.87 2.93 0.06 3.44 14.02 1.54 2.10 0.20 36 200 49.36 0.43 9.22 2.85 0.07 3.18 13.05 1.50 2.15 0.20 37 205 48.52 0.39 9.06 2.67 0.07 3.25 13.43 1.53 2.12 0.20 38 210 50.07 0.41 9.39 2.75 0.06 3.21 12.86 1.51 2.18 0.20 39 211 48.49 0.40 9.09 2.88 0.07 3.48 13.48 1.51 2.15 0.20 40 221 52.44 0.44 9.84 3.42 0.07 3.08 11.19 1.76 2.27 0.20 41 226 49.03 0.40 9.28 2.66 0.06 3.15 13.10 1.67 2.14 0.20 42 231 50.70 0.43 9.61 2.87 0.07 3.21 13.42 1.73 2.22 0.20 43 236 42.16 0.34 8.19 3.11 0.07 2.97 17.07 1.33 1.89 0.19 44 241 44.15 0.41 8.51 2.70 0.06 2.85 17.17 1.60 1.94 0.19 45 246 42.15 0.41 8.25 2.67 0.06 2.72 18.00 1.50 1.89 0.20 46 251 44.74 0.42 8.76 2.66 0.06 2.70 16.05 1.71 2.00 0.19 47 256 47.76 0.47 9.87 3.03 0.06 3.01 13.47 1.98 2.23 0.20 48 261 50.45 0.48 10.44 3.24 0.06 3.21 11.94 1.86 2.37 0.20 49 266 40.27 0.44 8.52 3.02 0.05 2.38 16.89 1.60 1.97 0.19 50 269 39.72 0.40 8.19 2.61 0.05 2.47 18.34 1.52 1.85 0.18 51 274 42.58 0.42 8.71 2.70 0.05 2.60 16.90 1.51 1.97 0.19 52 284 44.87 0.43 9.38 2.99 0.06 3.13 15.46 1.39 2.14 0.20 53 289 38.67 0.39 8.23 2.72 0.06 3.14 18.81 1.38 1.91 0.19 54 294 44.87 0.41 8.94 2.91 0.07 3.15 15.70 1.91 2.07 0.20 55 299 36.49 0.34 7.76 2.54 0.07 2.79 19.94 1.50 1.80 0.18 56 304 37.86 0.40 7.97 2.62 0.07 2.85 19.98 1.55 1.87 0.18 57 309 58.23 0.49 10.97 2.50 0.06 3.54 7.62 2.20 2.92 0.22 58 314 18.82 0.16 3.50 0.84 0.02 1.65 31.98 0.92 0.88 0.10 59 319 8.37 0.08 1.68 0.34 0.01 0.93 36.94 0.58 0.41 0.06 60 324 7.48 0.04 1.51 0.30 0.02 0.90 37.35 0.56 0.36 0.05

Sample Depth Trace elements ID (cm) Nb Zr Y Sr U Rb Th Pb Ga Zn Cu Ni Cr V Ba Sc 1 6 13 159 23.9 370 5.6 126 10.9 17.1 14.7 88.3 23.1 23.3 49.9 77 573 16.8 2 11 13 166 24.2 333 4.7 120 10.8 15.6 14.5 86.1 23.3 24 47.9 81.3 548 14.2 3 16 13 174 23.7 379 4.6 117 12.1 16.4 14.7 80.6 20.9 24.9 47.2 75.7 608 18.6 4 21 13 165 24.3 387 4.8 120 11.2 15.6 14.6 87.5 22.7 23.7 47.6 77.7 563 19.1 5 26 13 175 24.4 331 5.8 120 12.5 17.7 14.9 89.7 22.5 22.2 46.6 73.8 593 16.3 6 31 12.3 184 24.4 349 4.5 112 10.8 16.7 15.2 85.3 22 21.8 43.8 69.9 624 15.1 7 36 13.2 153 23.6 403 6.2 127 13 15.7 15 88.6 22.7 23.9 51.8 82.2 567 20.3 8 41 14 154 24.4 372 2.9 135 12.5 16 14.9 93.6 24.9 24.3 54.6 85.7 568 18.4 9 72 11 171 17.3 838 1.4 57.7 10.9 10.9 12.1 43.3 12.8 13.2 33.8 51.6 622 11.4 10 77 10.2 145 18 705 6.9 65 10.6 11 12.3 57.7 16.9 17.7 37.7 69.9 558 19.2 11 82 11.3 158 20.3 667 5 73.2 12.2 11 12.9 63.8 17.4 18.9 44.3 66.3 538 18.6 12 87 11.8 248 18.1 946 4.2 53.8 15.3 11.9 12.2 41.2 12.3 12.3 32.6 49.7 720 9.6 13 92 11.8 212 18.8 852 4.3 63.5 13 11.1 13.1 51.1 15.4 14.8 34.6 56.7 691 13 14 97 11.4 219 20.3 755 5.6 71 13.6 11.9 13.1 54.7 15.4 15.1 40.1 55.9 674 13.4 15 102 11.3 182 22 680 5 82.8 13 13 13.9 69 19.4 18.9 51.1 66.8 534 20.2 16 107 11.6 162 21.3 649 6 86.1 14.3 14.1 14.4 71.1 19.6 21.1 53.3 72.8 524 20.1 17 112 11.5 186 20.7 688 3.8 82.8 13.1 13.3 14 71.1 22.6 21.4 49.1 75.8 558 19.1 18 114 10 144 21.6 1103 1.6 83.2 14.9 15.8 14.5 71.4 20.5 20.3 47 69.4 553 23.3 19 119 10 149 21.7 1229 3.6 76.4 14.3 12.1 14.6 70 19.9 19.5 41.9 69.2 589 21 20 124 9.3 133 20 1305 2.5 66.9 13.2 11.1 14.3 64.5 18.3 17.9 38.3 62.1 551 19.9 21 129 8.1 130 20.1 1604 5.9 61.1 15.7 12.8 13.5 59.8 20.8 18.4 34 60.7 748 20.6 22 134 6.6 156 24.1 2997 2.5 61.4 19.4 16 14 59.5 24.4 20.9 32.7 62.5 843 21.4 23 139 13.4 155 24.2 533 4 101 14 17.2 15.4 86.1 24.5 24.5 49.7 96.1 634 21.2 24 144 13.8 175 24.8 377 5.1 105 14.6 14.7 15.2 86.9 25.1 24.9 63 87.2 640 20.5 25 149 13.7 175 24.9 359 4.9 99.3 12.3 12.5 15.1 77.6 24.1 22 53.6 79.5 641 20.1 26 154 14.7 181 26.9 295 5.9 103 14 15.4 14.9 86.1 23.4 21.8 59 87.4 588 18.8 27 159 15.3 189 27.2 295 4.9 108 13.8 20.4 15.6 91 26.9 22 62 86.3 670 17.4 28 160 14.5 196 27.2 431 6.4 102 14.4 16.8 15.4 87.7 24.8 27.6 58.1 81.7 668 19.8 29 165 12.4 175 23 533 8 83.1 10.1 15.9 14.2 76.8 23.5 23.4 60.2 82.7 994 19.9 30 170 13.7 185 24.9 354 5.1 95.2 13.3 20 15 80.1 22.6 26.3 59.4 72.5 632 17.6 31 175 13.4 192 23.5 354 5.4 95.2 13.9 19.3 15 79.4 23.2 26.7 59.4 74.4 638 19 32 180 13.4 174 24.4 288 3.9 96 11.8 17.5 14.7 92.7 22.7 30.5 68.8 72.4 651 22.5 33 185 12.7 174 23.9 284 4.7 94.8 12.6 17.8 14.3 85.2 22.9 29.2 67 70.5 638 19.4 34 190 13 172 23.2 306 3.9 93 11.6 17.1 14.2 82.7 23.2 26.9 77 75.1 671 20.8 35 195 13 179 23.7 298 2.5 93.3 12.3 17.8 14.5 83.5 22.2 27.8 62.9 72.2 639 17.4 36 200 13.7 192 24.3 325 4.2 94.6 12.4 17.5 14.5 81.5 22.4 26.4 63 71.3 658 16.5 37 205 13 183 23.6 284 5.9 92.3 12.4 16.8 14.7 81.9 21.2 26.3 62.2 70.7 620 19.9 38 210 13.8 194 24.6 317 3.7 96.6 12.6 18.8 14.7 84.6 22.2 26.4 62.4 77.3 714 17.9 39 211 13.8 194 24.6 317 3.7 96.6 12.6 18.8 14.7 84.6 22.2 26.4 62.4 77.3 714 17.9 40 221 14.3 204 24.6 277 5.2 99.1 13.5 19.3 14.9 83.6 22.3 26 60.5 77.4 661 16.8 41 226 13.7 192 24.4 389 2 98.1 12.9 19.8 15.5 83.6 22.7 26.5 62.4 73.1 671 20.9 42 231 14 194 24.9 363 5.5 97 13.4 18.8 14.8 83 23.6 26.9 59.7 75.5 658 21.8 43 236 11.3 168 23.5 697 3.9 87.5 13.8 17.8 14.7 76.1 21.2 26.4 53.7 60.8 794 23.8 44 241 11.7 181 23.5 730 5.8 87.2 14.4 16.4 15.2 73.2 20.9 22.6 50.6 68.8 776 21.4 45 246 12.1 186 23.9 779 4.6 87.3 14.4 14.6 15.4 72.8 21.2 22.5 51.5 66.1 793 21.2 46 251 12.1 195 23.3 702 3.7 92.4 14.2 15.4 15.2 73.6 19.1 21.1 53.8 71.2 789 19.8 47 256 13.4 186 24.1 474 3.9 105 13.1 16.4 15.4 84.9 22.7 26.5 57.3 82.7 751 20 48 261 13.4 191 24.3 425 5.7 108 12.6 16.7 15.5 85.7 22.6 26.7 55.7 82.9 761 19.3 49 266 12.3 168 24.4 911 5.6 98.5 14.5 15.5 14.7 86.2 24.7 25.7 51.7 104 705 22.7 50 269 11.4 165 24.6 1006 5.7 95.2 14.9 15.4 15.5 83.1 23.7 23.6 51.5 84.7 695 22.1 51 274 12 174 24.3 874 5.6 99.4 13.8 16.1 15.4 85.5 24 23.5 51.6 89.4 705 20 52 284 14.8 183 24.6 603 3.4 108 13.3 17.2 15.8 89 23.3 24 59.5 93.8 819 21.7 53 289 13.5 168 24 859 5.1 105 16.3 13.9 15.5 84.1 26.3 24.6 52 84 779 21.8 54 294 13.3 165 24.4 703 5.8 112 15.5 18.5 15.4 89.3 25.1 23.3 53.8 86.6 635 21.4 55 299 12.7 165 24 1098 3.4 99.5 17.9 16 14.7 75.8 20.3 19.8 43.9 73.3 678 21.6 56 304 13.4 168 24 1057 2.4 103 16.5 15.8 15 76.3 20.9 20 49.2 70.8 647 23.9 57 309 21.2 262 21.9 491 4.1 127 21 18.9 14.7 64 17.7 17.8 47.3 69.8 941 12.6 58 314 8.9 118 16.6 2165 0 52.5 19.1 9 12.7 29.7 10.7 4.9 13.7 43.1 614 2.6 59 319 3.9 78.7 13.2 2581 0 27.1 20.1 7.9 11.8 15.3 9.7 0.5 1.2 25.8 425 0 60 324 3.7 76.1 13.2 2703 0 25 19.4 6.7 11.9 12.1 7.7 0 3 24 388 0