A Late Glacial-Early Holocene Paleoclimate Signal from the Ostracode

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A LATE GLACIAL-EARLY HOLOCENE PALEOCLIMATE SIGNAL FROM THE OSTRACODE

RECORD OF TWIN PONDS, VERMONT

A thesis submitted

To Kent State University in partial

Fulfillment of the requirements for the

Degree of Master of Arts

Kevin J. Engle

May 2015

Except for previously published materials

Thesis Written by

Kevin Engle

B.S. Shawnee State University, 2011

M.S. Kent State University, 2015

Approved by

Alison Smith Dr. Alison Smith, Professor, Ph.D., Geology, Masters Advisor

Daniel Holm Dr. Daniel Holm, Professor, Ph.D., Chair, Department of Geology

Dr. James Blank, Professor, Ph.D., Dean, College of Arts and Sciences

TABLE OF CONTENTS

TABLE OF CONTENTS ...... iii

LIST OF FIGURES ………………………………………………………………………………………………………… vii

LIST OF TABLES…………………………………………………………………………………………………………….. x

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

CHAPTERS

I. Introduction ………………………..………………..……………………………………………… 1

Regional Geologic Setting …………………...……….………………….…………………… 1

Bølling-Allerød Interstadial ……………………….……………..…………………………. 9

Younger Dryas ………………………………………………………………….…………………. 10

Post-Younger Dryas Climate Interval …………………………………………………… 19

9.2 kya Event ...………………………………………………………………………….………… 24

8.2 kya Event ………………………………………………………………………….…………… 27

II. Methods …………………………………………………………………………………………..... 31

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Ostracode Bleaching Procedure ……..………………………………………………..... 34

Running Samples on the Kiel ..……………………………………………..……………… 36

Reporting ……………………………………………………………………………………………. 37

Statistical Analysis ……………….……………………………………………..…..………..… 40

Cluster Analysis ………………………………………………………………….………….……. 41

Principal Components Analysis ……………………………………..…….……………… 41

II. Results ….…………..…………………………………………….…………………………….…… 43

Multi-Proxy Work…………………………………………………………………………..…… 43

Age Model.……………………………………………………………………………………………43

Bulk Carbonate δ18O ……….……………………………………………………………….…..47

Loss on Ignition …………………………………………………..……………………………... 50

Ostracode Abundances ………………………………………………..…………………..… 53

Candona ohioensis ……………………………………………..…………………… 53

Candona candida ……………………………………………..…………………….. 54

Candona paraohioensis …………………………………………………………... 55

Pseudocandona stagnalis ……………………………………..………………… 56

Cyclocypris ampla …………………………………………………………………… 57

Cypridopsis vidua ……………………………………………………….……..……. 58

Darwinula stevensoni ………………………………………………..……....….. 59

Cyclocypris globosa …………………………………………………………….…… 60

Cluster Analysis--Ostracode Zones ……………………………………..………….…… 65

P. stagnalis Zone ………………………………………………….……….………… 67

C. ampla Zone …………………………………………………………………………. 69

D. stevensoni Zone …………………………………………………………….……. 71

Nektic Zone ……………………………….………………………………..………..… 73

C. ohioensis Zone ……………………………………..……………………………… 75

Principal Components Analysis (PCA) ……………………..………………………..… 77

Isotopes ……………………………………………………………………………………………… 86

Benthic δ18O vs. ostracode abundances ……………..………………………………. 91

Benthic Ostracode δ18O vs. Bulk Carbonate δ18O ……………………….……….. 93

Post-Younger Dryas Interval ……………………………………………………………….. 95

IV. Discussion …………………………………………………………………………………………… 97

Conclusion ……………………..………………………………………………………………………………….…… 102

References .……..………………………………………………………………………………………………….…….104

Appendices

A. Isotope Input Data …………………………………………………………………………………...127

B. VPDB values ………………………………………………….………………………..…………….….133

C. VSMOW Values for a Range of Temperatures ………………………….…….………. 137

D. Ostracode Counts …………………………………………………………………………….….……140

LIST OF FIGURES

Figure 1. Generalized Geologic Map of Vermont ……………………………………………………..…. 2

Figure 2. Topographic Maps of Twin Ponds, Vermont ……………………………………………..…. 4

Figure 3. Google Earth View of Twin Ponds, Vermont ……………………………………………..…. 6

Figure 4. Climate events following the Last Glacial Maximum from a central European pollen record …………………………………………..………………………………………………………………... 10

Figure 5. Effects of the Younger Dryas seen in various records around the globe …..…. 16

Figure 6. Example of a strong Jet Stream ……………………………………………….…………………. 19

Figure 7. Post-Younger Dryas climate effects across North America ……………...…..……. 20

Figure 8. Example of a weak Jet Stream ……………………………………………………………………. 22

Figure 9. Routing of Lake Agassiz overflow to the oceans …………………………………………. 25

Figure 10. Age Model …………………………………….………………………………………....……………… 45

Figure 11. Time gap in core ……………………………………………………………………………..………..46

Figure 12. Bulk carbonate δ18O profile of Twin Ponds ……………………………...…….………… 49

Figure 13. Loss on Ignition profile of Twin Ponds ………………………………………….....………. 51

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Figure 14. Comparison of a typical core section with the Younger Dryas section of the core ………………………………………………………………………………………………………………….…..…… 52

Figure 15. Ostracodes found in the Twin Ponds core ………………………………………..….…...62

Figure 16. Ostracode abundance profile ………………………………….………..……………….……. 64

Figure 17. Dendrogram showing 5 zones identified in the core from the late Glacial to early Holocene ………………………………………………………………………..…………………….…...……. 66

Figure 18. PCA Scatterplot of Axis 1 vs. Axis 2 ………………………..……………………...... ……… 81

Figure 19. Scree Plot summarizing eigenvalues ………………………………………………….……..82

Figure 20. PCA Case Scores vs. Depth in Core…………………………………………………….……… 83

Figure 21. PCA Scatterplot of Axis 1 vs. Axis 3…………………………………………………..………. 84

Figure 22. PCA Scatterplot of Axis 2 vs. Axis 3…………………………………………………..…..….. 85

Figure 23. Twin Ponds benthic ostracodes δ18O compared with depth in the core..…... 87

Figure 24. Twin Ponds benthic ostracodes δ18O compared with radiocarbon dates of the core ………………………………………………………………………………………………………………..…..….… 88

Figure 25. Twin Ponds nektic ostracodes δ18O compared with depth in the core

……..……………………………………………………………………………….……………………………….…………..89

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Figure 26. Twin Ponds nektic ostracodes δ18O compared with age from radiocarbon dates of the core …………………………………………………………………………………………….….…….. 90

Figure 27. Ostracode abundance profile vs. benthic ostracode δ18O profile

…………………………………………………………………………………………………………………………....….… 92

Figure 28. Correlation of benthic ostracode δ18O with bulk carbonate δ18O and GRIP

δ18O ……………………………………………………………………………………………………………………….…. 94

Figure 29. Correlating the information from Figure 25 with the Post-Younger Dryas interval ……………………………………………………………………………………………………………………… 96

LIST OF TABLES

Table 1. The timing of the 9.2 kya event ………………………………….………………………..………27

Table 2. The recommended number of ostracode valves for isotope analysis ……………33

Table 3. The minimum and maximum temperatures for air, surface water and bottom water for the area in which each ostracode species was collected …………………...……….39

Table 4. Abundances of ostracodes in the P. stagnalis Zone ………………….………..……..…68

Table 5. Abundances of ostracodes in the C. ampla Zone ……………………………...………….70

Table 6. Abundances of ostracodes in the D. stevensoni Zone ……………….……...………….72

Table 7. Abundances of ostracodes in the Nektic Zone………………………………..….…….…..74

Table 8. Abundances of ostracodes in the C. ohioensis Zone …………………….……………….76

Table 9. Eigenvalues and variance explained by the first 4 axes and the PCA variable loadings from the PCA analysis of the Twin Ponds core ………………………….……..…………..80

Acknowledgements

Growing up in the country and working on a farm I had never really considered myself “college material.” I surprised myself while earning my undergraduate degree at

Shawnee State University when I realized how much I loved geology. Even after doing well while earning my Bachelor’s I still didn’t quite believe that I was cut out for school, so I decided to apply for jobs instead of furthering my education. The job search was not going very well, so I figured I would just apply to graduate school and see what happens. And to my surprise I received an amazing offer from Kent State, which I happily accepted. So I would like to thank the Kent State Geology Department for giving me a chance, helping me to believe in myself and opening up a whole new world for me.

I would like to thank my parents, Tim and Heidi Engle, who have been there for me every step of the way. I would not be where I am today without their love and support.

To my advisor, Dr. Alison Smith, you also showed me a whole new world under the microscope, which I will never forget. Thank you for everything, your attitude and passion for your work really inspired me and helped me to finish this even when it seemed impossible.

To my committee members Dr. Palmer and Dr. Ortiz, thank you both for giving me a chance to be in this program. Both of you have helped and challenged me to be a better student throughout my time at Kent State, and I thank you for it.

Lastly, thank you to the Katherine Moulton Scholarship and to the SGE

Scholarship Committee. The financial support I received was vital to completing my research and I would not have been able to do so without it.

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Introduction

North America was greatly affected by an abrupt global cooling event known as the Younger Dryas stadial, which occurred from about 12.9-11.5 kyr ago, based upon research done on Greenland ice cores (Rasmussen et al., 2006). Regions adjacent to the

North Atlantic were directly affected by the abrupt cooling while regions further inland were affected by changes in atmospheric circulation (Shuman et al., 2002). Areas such as Maine and Nova Scotia were directly affected by the cooling of the North Atlantic and showed a cool, dry climate during the Younger Dryas (Diffenbacher-Krall and Nurse,

2005; Stea and Mott, 1989). Also directly affected were sites in the Great Lakes area (Yu and Eicher, 1998). In this thesis, a sediment core from Twin Ponds, Vermont is studied as part of a multi-proxy study of the Younger Dryas. Ostracodes and stable isotopes are analyzed and show how this site in Vermont is similar to the regional records from

Maine and Nova Scotia, indicating a cool, dry response to the North Atlantic cooling.

Twin Ponds, Vermont provides a record not only of the Younger Dryas and early

Holocene environment in northern New England, but also provides new information on the Holocene biogeography of species of nonmarine ostracodes in North America.

Twin Ponds is located in east-central Vermont near the town of Brookfield

(Shown by the star in Figure 1). The coordinates of the lake are 49o3’41.69N, and

72o34’43.97W and it is at an elevation of 371.2 meters (1217.8 feet). The geology of

Vermont is complex, being shaped by Precambrian and Paleozoic orogenic events and Cenozoic glacial-interglacial cycles.

Regional Geologic Setting

Twin Ponds is located in physiographic province known as the Connecticut

Valley. This valley lies between the Green Mountains to the west and the Bronson Hill

Province to the east in New Hampshire (Doolan, 1996). The Connecticut Valley is characterized by thick deposits of calcareous rocks extending from Connecticut up to

Quebec (Doolan, 1996). Most of the Connecticut Valley lies in the Vermont Piedmont region. This region is located at the foothills east of the Green Mountains (Jacobs,

1950). Many of the sedimentary rocks in the Piedmont have been metamorphosed.

The bedrock of the Connecticut Valley is mostly Silurian to Devonian age muscovite/biotite phyllite interbedded with limestone/marble (Ratcliffe et al., 2011). In the northern part of the valley, igneous intrusions can be seen in outcrops. The southern part of the valley contains Precambrian to Cambrian age outcrops (Figure 1).

Figure 1: Generalized Geologic Map of Vermont (From Doll et al., 1970)

The Connecticut Valley/Piedmont region contains many lakes that were formed by glaciers. Evidence of glacial activity can be seen throughout the state in the form of eskers, moraines, outwash plains and kettle lakes (Van Diver, 1987). It is possible that glacial retreat played a role in shaping the Twin Ponds basins. The topographic map of the Twin Ponds region (Figure 2) shows a general increase in elevation from east to west and also shows many similarly sized lakes in the area. These lakes have been carved into the regional bedrock, known as the Waits River Formation which is the predominant bedrock at Twin Ponds (Waters, 2013).

Figure 2: Topographic Maps of the regions surrounding Twin Ponds (From National Geographic Society, 2009)

The Waits River Formation is one of the larger formations in the region and is

Devonian in age. It contains beds of limestone that in many places have been metamorphosed to a quartzose marble (Perkins, 1916). The Waits River also contains many varieties of phyllite schist found interbedded in the limestone. Additionally, the formation also contains some conglomerate, slate and quartzite beds (Ratcliffe et. al.,

2011). Twin Ponds is located in the carbonaceous phyllite and limestone member of the

Waits River Formation (Ratcliffe et. al., 2011). It contains “dark-bluish-gray micaceous quartz-rich limestone in beds from 10cm to 10ft thick and interbedded with a dark-gray to silver-gray, lustrous, carbonaceous muscovite-biotite-quartz phyllite” (Ratcliffe et. al.,

2011).

The name ‘Twin Ponds’ was given because of the two connected basins. The core was taken from the western basin, in a near shore environment on the edge of a wetland (Figure 3). The core was taken in November of 2012 by Dr. Bryan Shuman and his research team from the University of Wyoming. In late November of that same year, the core was imaged and sampled. The images were taken using a Geotek Multi-Sensor

Core Logger with a digital imaging system at the University of Wyoming.

Figure 3: Google Earth view of Twin Ponds. The red star shows the location of the core.

The core consists of predominantly of white marl which is typical of littoral environments in carbonate-rich settings. The marl in this core was formed primarily from macrophytic algae known as Chara. Chara was described as a major factor in marl production by Davis (1900). He noted that when Chara decays it leaves behind very brittle microscopic tubular encrustations, and marl accumulation occurs when these encrustations break apart. Murphy and Wilkinson (1980), noted similar results in a study of a marl lake in central Michigan in which carbonate formation in shallow water lacustrine deposits was largely due to biogenically driven precipitation associated with macrophytes. The tubules left behind from Chara are abundant in the Twin Ponds core, along with microfossils such as bivalves and gastropods, which are Characteristic of a littoral environment.

Ostracode fauna are found in marine, interstitial and nearly every terrestrial environment such as springs, wetlands, lakes and aquifers (Smith and Delorme, 2009).

Their abundance in the benthic and nektic communities of lacustrine settings makes them an ideal proxy for ecological, evolutionary and paleoclimate research (Martens et al., 2007). A cool, oxygen rich environment such as Twin Ponds is an ideal site for ostracode collection.

Most recent nonmarine ostracodes belong to 3 superfamilies within the order

Podocopida: Cypridoidea, Darwinuloidea and Cytheroidea (Smith and Delorme, 2009).

Of these three, most of the ostracodes found in the Twin Ponds core belong to

Cypridoidea. Cypridoidea is the largest group and consists of 4 families, of which

Candonidae may be the most recognizable (Martens et al., 2008)

Ostracodes form a bivalved shell around their soft parts which is composed of a low-magnesium calcite (Smith and Delorme, 2009). This bivalve carapace is what is preserved in sediment records and the chemistry of it reflects the environmental conditions of which it formed (Dettman et al., 1995). Most species of ostracodes molt between 7 and 9 times during their lifetime with each molt stage lasting from hours to days (Turpen and Angell, 1971). There can be a wide range of the lengths of molt periods and seasons of molting, therefore multiple ostracode species are gathered at a single location to accurately record the seasonal variations in temperature and precipitation (Dettman et al., 1995).

The calcium used in forming the carapace is taken directly from the water column at the time of molting (Turpen and Angell, 1971). Because ostracodes precipitate their shell in near equilibrium with the water around them, the isotopic composition and ratios of magnesium in an ostracode carapace can reflect changes in water chemistry, salinity, substrate Characteristics, temperature, oxygen and nutrient availability (Frenzel and Boomer, 2005). Isotopic analysis of ostracodes from Twin

Ponds was run for δ18O and δ13C. δ13C is an indicator of the productivity of the lake and

δ18O is an indicator of past temperatures. The δ18O of the shells reflects the δ18O of the water, provides valuable information regarding the temperature of the water it formed in and is the focus of the isotope analysis.

Bølling-Allerød Interstadial

Following the Last Glacial Maximum, climate frequently shifted back and forth between stadial and interstadial (Figure 4). The Bølling-Allerød interstadial was a warm episode that occurred from 14.6-12.9 kya ago (Obbink et al., 2010). It started at the end of the Oldest Dryas and ended abruptly at the start of the Younger Dryas. In some regions, such as Central Europe the pollen record shows an Older Dryas stadial which can be seen during the Bølling-Allerød, defining the order of these episodes as Oldest

Dryas, Bølling, Older Dryas, Allerød, Younger Dryas (Litt and Stebich, 1999). The transition phase from the Bølling-Allerød to the Younger Dryas can be seen in the Twin

Ponds core and is Characterized by a time of rapid climate change such as that seen at the Bølling-Allerød/Younger Dryas boundary. The name Bølling-Allerød comes from locations in Denmark where the warm period was first noticed in pollen and fossil records. The interstadial was originally noticed in Allerød and later expanded on in

Bølling a few decades later (Hoek, 2009).

Figure 4: Pollen record from central Europe showing various climate events following the Last Glacial Maximum (From Litt & Stebich, 1999, Figure 6, p. 12, shown with permission from Quaternary International).

The warming at the start of the Bølling-Allerød was accompanied by changes in the Atlantic Meridional Overturning Circulation (AMOC) which may suggest a connection between the two (Liu et al., 2009). Reductions in the AMOC are driven by increased freshwater discharge into the North Atlantic which usually causes cooler and drier conditions in the surrounding regions (Obbink et al., 2010). This hypothesis states that after the Oldest Dryas episode, freshwater discharge to the North Atlantic ended and thus the AMOC grew stronger. Also, orbital forcing during the Bølling-Allerød increased

11 the amount of CO2 in the atmosphere (Liu et al., 2009). Orbital cycles control the amount of insolation and times of high insolation leads to warming of the oceans.

When the oceans are warmed there is an increase in the amount of CO2 exchanged between the ocean and the atmosphere (Ruddiman, 2003). The combination of the strengthened AMOC and the increase in CO2 exchange created a warm period that persisted in most areas until the start of the Younger Dryas stadial.

Another hypothesis states that a meltwater pulse from an Antarctic ice sheet intensified the thermohaline circulation, increasing temperatures (Weaver et al., 2003).

This hypothesis involves meltwater pulse 1A (mwp-1A), which caused a rise in sea level of about 24 m in less than 1000 years (Fairbanks, 1989) and coincides with the Bølling-

Allerød interstadial. This meltwater pulse is usually thought to be associated with the

Laurentide Ice Sheet of North America. However, Weaver et al., 2003 propose that part of mwp-1A is from an Antarctic ice sheet. According to this hypothesis, melting of the

Antarctic ice sheet caused an Antarctic Cold Reversal in which warming took place in the north and cooling in the south.

The Younger Dryas

The Younger Dryas is the last in a series of Dryas stadials during the Late Glacial.

“Dryas” comes from a plant species Dryas octopetala which has abundant pollen found in records from the Oldest, Older and Younger Dryas (Hoek, 2009). A generally accepted

12 time period for the Younger Dryas is from 12.9-11.5 kya, which is based on the research done on Greenland ice cores (Rasmussen et al., 2006). The Younger Dryas was a global scale cooling event, resulting from a release into the North Atlantic of cold meltwater that altered the North Atlantic Deep Water production and a changed the thermohaline circulation (Fiedel, 2011). The timing of the Younger Dryas varies between locations around the world possibly because of the lag times associated with ocean water transport and also because of problems with radiocarbon dates during this time. The

14 Younger Dryas is linked to an increase in C from reduced sun strength or from less CO2 absorbed into the cold ocean waters, causing increased atmospheric CO2 buildup (Goslar et al., 1995). Increases in 14C are often seen during climate events, which lead to plateaus in the radiocarbon dates and can cause differences in dates for climate events.

These plateaus make it necessary to calibrate the ages in order to assign a calendar year date to the radiocarbon age. With more and more data being discovered every year, these calibration methods are becoming more accurate. The hypotheses for the increase in 14C during the Younger Dryas include a weakened carbon exchange in the ocean, reduced sun strength or a combination of these (Fiedel, 2011). During the

Younger Dryas, cold, fresh water slowed thermohaline circulation by staying on the surface as a lens. This lens of cold water prevented warm, salty water from reaching the surface and weakened the Atlantic Meridional Overturning Circulation (AMOC). With a weakened AMOC, less CO2 moved from the surface to the deeper waters. Another hypothesis states that during the Younger Dryas, there was an increase in cosmic

13 radiation reaching the top of the atmosphere, which increased the amount of atmospheric 14C (Goslar et al., 2000a).

The prevailing theory for the mechanism behind the Younger Dryas cooling is related to the collapse of the Laurentide ice sheet from the warming during the Bølling-

Allerød interstadial. The Laurentide ice sheet covered much of middle to eastern

Canada, and acted as an ice dam, holding in glacial Lake Agassiz to the west. During the

Bølling-Allerød warm period the ice sheet began to shrink until it eventually collapsed.

When the ice sheet collapsed, Lake Agassiz was no longer held in and water discharged in various directions as seen in Figure 9. The main pulse of freshwater was sent through the Hudson Strait into the North Atlantic. The North Atlantic is one of 2 areas in the modern oceans where deep water is formed, called the North Atlantic Deep Water

(NADW). The other is the Antarctic Bottom Water (AABW). As warm water flows north towards the North Atlantic, it gradually becomes colder and more saline. The decreased temperature and increased salinity cause the water mass to sink to the bottom and start to flow south, making the NADW a vital component in the thermohaline circulation. The northward movement of warm water in the Atlantic and the southward movement of cold, deep water comprise what it known as the Atlantic Meridional Overturning

Circulation (AMOC). When the cold, fresh water released from the ice sheet entered the North Atlantic, its effects were almost immediately noticed in areas surrounding the

North Atlantic. Younger Dryas effects were seen later in other areas around the globe.

This meltwater sat on the surface as a lens of freshwater, changing the density of the water, slowing the AMOC and in turn the thermohaline circulation.

Most hypotheses surrounding the Younger Dryas involve the release of meltwater to the North Atlantic. However, the mechanisms that cause this have been subject to debate. One such hypothesis is the Younger Dryas Impact hypothesis. The impact hypothesis states that the Laurentide ice sheet collapsed as a result of the impact of one or more extraterrestrial objects (Firestone et al., 2007). This hypothesis states that as a result of the impact of one or more extraterrestrial objects, the ice sheet destabilized and released meltwater into the North Atlantic. This hypothesis is also supported by the megafaunal extinction around the start of the Younger Dryas in which mammoths, sloths, horses and camels in North America all became extinct (Firestone et al., 2007). However, these findings have been subject to much speculation and criticism

(van Hoesel, 2014).

The Younger Dryas was a global scale event (effects seen in Figure 5). The AMOC plays such a major role in the transport of the world’s ocean water that slowing it down had worldwide impacts. Stalagmite oxygen isotope records from eastern China show a similar resemblance to records from the Greenland ice cores (Wang et al., 2001). This suggests that the cold, dry climate that was typical for sites surrounding the North

Atlantic was experienced as far away as China. 14C data from Venezuela shows a connection between a rise in 14C and the timing of the Younger Dryas (Hughen et al.,

2000). Indicators of the effects of the Younger Dryas were seen in South America as well. Because of their proximity to the North Atlantic, European lake records also show a strong Younger Dryas signal (Bjӧrk et al., 1996). In some areas, the Younger Dryas had opposite effects, and seemed to bring warm, wet conditions. One such place is

15 northeast China (Hong et al., 2010). Northeast China saw a sudden increase in precipitation during the Younger Dryas, which has been attributed to northern migration of the East Asian Monsoon. The migration of the East Asian Monsoon separated China into two climate regimes; wet in the north and dry in south (Hong et al., 2010).

Warmer, wetter Cooler, drier

Figure 5: Effects of the Younger Dryas seen in various records around the globe (From Bjӧrk et al., 1996, Diffenbacher-Krall and Nurse, 2005, Dorale et al., 2010, Gonzales and Grimm, 2009, Grimm et al., 2006, Hendy et al., 2002, Hong et al., 2010, Hughen et al., 2000, Nordt et al., 2002, Wang et al., 2001, Yu and Eicher, 1998).

North America was also greatly affected by the Younger Dryas climate event.

Regions adjacent to the North Atlantic were directly affected by the abrupt cooling while regions further inland were affected by changes in atmospheric circulation

(Shuman et al., 2002). Areas such as Maine and Nova Scotia were directly affected by the cooling of the North Atlantic and showed a cool, dry climate during the Younger

Dryas (Diffenbacher-Krall and Nurse, 2005; Stea and Mott, 1989). Also directly affected were sites in the Great Lakes area (Yu and Eicher, 1998). Twin Ponds, Vermont falls in line with these records and shows a cool, dry response to the North Atlantic cooling.

Other North American effects include warmer and wetter conditions in south Texas and central Florida (Nordt et al., 2002; Grimm et al., 2006). General warming in these regions is believed to be the result of a weakened Gulf Stream (Grimm et al., 2006). In which modeling experiments show that weakening of the Gulf Stream would lead to warming of the surrounding areas (Manabe and Stouffer, 1997). The southern Great

Plains were drier and possibly warmer during the Younger Dryas, with evidence for drought and dune activation in sediment records (Holiday et al., 2006).

Younger Dryas cooling can be seen in various parts of the North American continent as well. Southwestern Missouri shows an increase in C4 grasses indicating an expansion of grassland from the aridity of the Younger Dryas (Dorale et al., 2010). The

δ13C record from Dorale et al., 2010 shows slightly cooler and drier conditions in southwestern Missouri and attributes it to an eastern migration of the prairie-forest boundary. This prairie-forest boundary migration can also be seen in records from

Illinois where there is an increase in spruce and a decrease in ash, which indicates a

18 cooler, drier climate during the Younger Dryas (Gonzales and Grimm, 2009). Cooling from the Younger Dryas can even be seen in California, as a result of cooling of the

Pacific (Hendy et al., 2002). While the effects of the Younger Dryas can be considered cool and dry in most places, the mechanisms that produce this climate can be different.

Not only did the Younger Dryas cool the North Atlantic, but modeling experiments show a cooling of the North Pacific as well (Okumura et al., 2009). Additional modeling experiments show that a drop in temperature of the North Pacific has cooling and drying effects on parts of North America (Peteet et al., 1997). A cool North Pacific would lead to a reduction and temperature and moisture content of the Pacific air masses being advected over the United States (Dorale et al., 2010). The model from

Okumura et al. (2009) shows an increase in the westerly winds during the Younger Dryas which would mean an increase in the jet stream. The increase in the wind strength would move the cold, dry Pacific air mass further inland bringing drier conditions with it and moving the prairie-forest boundary further to the east (Dorale et a., 2010). An example of the jet stream location can be seen in Figure 6. As this strong jet stream traveled further east, it would pass over the Laurentide ice sheet, picking up cold, dry air and pushing it over sites in the Great Lakes or in the New England area. This in combination with its proximity to the cold North Atlantic made the New England area particularly sensitive to climate change.

Figure 6: showing example of a strong Jet Stream (NASA/Goddard Space Flight

Center Scientific Visualization Studio, 2011)

Post Younger Dryas Climate Interval

The Younger Dryas ended abruptly, on the order of decades (Alley et al., 1993).

Following the Younger Dryas climates around the world returned to their previous pre-

Younger Dryas forms. A renewed thermohaline circulation meant a strengthened Gulf

Stream, which cooled Florida (Grimm et al., 2006). The North Pacific returned to warmer conditions and caused California to warm (Hendy et al., 2001). The return to warmer conditions in the North Pacific also moved the prairie-forest boundary back to the west, and wetter and warmer conditions returned to Illinois (Gonzales and Grimm,

2009). However, New England and its surrounding areas remained cool and dry for a

20 long period of time following the Younger Dryas. Sites further north, such as Maine and eastern Canada, remained cool and dry as a result of higher solar radiation and proximity to the wind from remnants of the Laurentide ice sheet (Diffenbacher-Krall and

Nurse, 2005; Carcaillet and Richard, 2000). Sites in New England, Great Lakes and New

York remained cold as well but returned to slightly wetter conditions (climate conditions shown in Figure 7). Termed the “Post-Younger Dryas Climate Interval” by Kirby et al.,

(2002), this period stretched from 11.6 and 10.3 kya in a study of Fayetteville Green

Lake, New York. In this bulk carbonate study of the lake, the authors noted a cold interval linked to the position of the circumpolar vortex. These results have also been seen in eastern Lake Ontario (McFadden et al., 2004), repeated in central New York

(Mullins et al., 2011) and are seen at Twin Ponds, Vermont.

Post-Younger Dryas 11.6-10.3 kya

Warmer, wetter Cool, wetter Cooler, drier

Figure 7: Post-Younger Dryas climate effects from various sites across North America

Kirby et al. (2002) argue that the Post-Younger Dryas interval was a result of an expanded circumpolar vortex. The circumpolar vortex defines the position of the polar front jet stream which separates cool, dry air to the north from warm, moist air to the south (Diefendorf, et al., 2005). A meandering jet stream can be seen in the Figure 8. A weaker jet stream will have this meandering shape as opposed to a strong jet stream, seen in Figure 6, which is straighter. This shows that an expanded jet stream does not necessarily bring deep, cold conditions (Angell, 1992). Fixed within the circumpolar vortex are long waves, or Rossby waves, which determine the shape of the jet stream and vary with the seasons (strongest in the winter) and with climate variations on larger time scales (Burnett, 1993). These Rossby waves have extremely large wavelengths and can form troughs over certain parts of the globe, such as the trough over the northeastern United States (Figure 8). After the Younger Dryas, the thermohaline circulation was renewed, rapidly warming the North Atlantic, while the northeastern

United States remained cold. This created a thermal contrast between the interior

United States and the North Atlantic, increasing pressure gradients and forcing the trough pattern to stay in place as a stationary front (Kirby et al., 2002).

Figure 8: Showing an example of a weak Jet Stream (NASA/Goddard Space Flight Center Scientific Visualization Studio, 2011).

The trough in the jet stream here is the main factor contributing to a storm track along the East Coast, in which storms are moved from the northern Gulf of Mexico to

Florida and then up the East Coast (Knappenberger and Michaels, 1993). These storms carry large amounts of precipitation with high δ18O values because of their proximity to the Atlantic Ocean (Kirby et al., 2002). This can be thought of in terms of the ‘latitude effect’, which states that the lower latitude areas have heavier isotope values

(Dansgaard, 1964). The semi-permanent trough over the northeastern United States moving storms enriched in δ18O up the coast can be seen in post Younger Dryas records

23 for in the area. Because of the position of the trough, these records are only picked up in the northeastern United States (McFadden et al., 2004). The timing of the Post

Younger Dryas Interval varies between sites. Kirby et al., (2002) suggest the timing is from 11.6 to 10.3 kya while sites such as eastern Lake Ontario suggest it lasted until 9.4 kya (McFadden et al., 2004). The record from McFadden et al., (2004) matches up well with hypothesis proposed by Kirby et al., (2002) and shows an increase in δ18O values and an increase in precipitation. Additional records from central New York show increases in δ18O during the Post Younger Dryas Interval, and show the interval lasting until 9.2 kya (Mullins et al., 2011).

Kirby et al., (2002) test the hypothesis of a Post Younger Dryas Interval by examining other hemispheric effect resulting from the position of the jet stream. These

Rossby waves have continental size wavelengths and if there is a trough over the

Northeastern United States, then they claim there should be a ridge “downwind” of it.

A possible Post Younger Dryas signal can be seen in an ostracode oxygen isotope record from Germany, which may suggest a warm, high precipitation climate (von Grafenstein et al., 1999). This may indicate large quantities of precipitation being pushed southeast along the ridge. Another possible Post Younger Dryas signal may be noticeable in a

Greenland ice core (GISP2), in which snow accumulated at an extremely fast rate after the Younger Dryas had ended (Alley et al., 1993). This rapid accumulation in snow may have been the result of the increased precipitation being transferred north along the path of the jet stream.

9.2 kya event

The next major climate event noticeable in the core is the 9.2 kya event. The 9.2 event is a widespread climate anomaly that is seen in many Northern Hemisphere records around that time. The exact timing of the event varies from site to site but is generally around 9.2 kya. This event is often compared to the better known 8.2 kya event, because the effects of the events seem to be similar. The cause of the climate anomaly was believed to be the result of a meltwater pulse released from glacial Lake

Agassiz (Fleitmann et al., 2008). Lake Agassiz was the largest of all proglacial lakes. The size and morphology of the lake was always changing as a result of its position along western margin of the Laurentide Ice Sheet, the topography of the deglaciated surface, the elevation of the active outlet and the differential isostatic rebound (Teller and

Leverington, 2004). Overflow from the lake was carried to the oceans by 4 different outlet paths shown in Figure 9.

Figure 9: Routing of Lake Agassiz overflow to the oceans. Total area covered by Lakes Agassiz and Ojibway is shaded and an outline of the Laurentide Ice Sheet at 9 kya is shown by dashed line. Runoff routes are identified as: A=Northwest through the Clearwater-Athbasca-Mackenzie River Valleys to the Arctic Ocean, B=North and east through Hudson Bay and Hudson straight to the North Atlantic Ocean, C=East through channels that led to the Great Lakes and then to the St. Lawrence Valley and North Atlantic Ocean, and D=South from the Minnesota and Mississippi River Valleys to the Gulf of Mexico (From Teller et al., 2002, Figure 1, p. 880, shown with permission from Quaternary Science Reviews).

During the early Holocene the lake was believed to have released meltwater along one of these paths at 14 separate times (Teller and Leverington, 2004). The

26 amount of meltwater released varied and the largest releases seem to correlate with well known climate events such as the 8.2 kya event. The 9.2 kya event also seems to line up well with one of these releases (Fleitmann et al., 2008). Releases would occur as the lake filled and overflowed through one of these outlets, with the specific outlet used varying with each release. Whenever an outlet became available there was a rapid release of water followed by lake level drawdown. After this, the baseline outflow of the lake to the ocean would be through the newly opened outflow. The length of time of each outburst can only be estimated by paleobathymetry and depth of flow in the outflow channels. Drawdown of the lake was believed to have occurred over months to a few years and not lasting longer than a decade (Teller at al., 2002).

The meltwater pulse released around the time of the 9.2 kya event occurred through the Gulf of St. Lawrence (route C in Figure 9). This route sends the freshwater very close to the area of North Atlantic Deep Water production and is believed to have affected the production and impacted the thermohaline circulation (Teller and

Leverington, 2004). Although the pulse of water released was not as much as during other events such as the 8.2 kya event, certain factors, such as the route taken, may have played a role in its widespread influence. In the time leading up to the 9.2 kya event there was a series of pulses released, which may have preconditioned the thermohaline circulation and made it more susceptible to being impacted by a meltwater pulse (Fleitmann et al., 2008). These factors suggest that even a small amount of freshwater released into the North America may be enough to have an impact on the thermohaline circulation.

The effects of the 9.2 kya event are seen mainly in Northern Hemisphere but have been seen elsewhere across the globe as well. In addition to the Twin Ponds record, distinct cold episodes have been noticed the Greenland ice cores, Arolik lake in

Alaska (Hu et al., 2003), Lake Ammersee in central Europe (von Grafenstein et al., 1999),

Hoti, Defore and Qunf Caves in Oman (Fleitmann et al., 2007) and Dongge Cave in China

(Dykoski et al., 2005). The timing of these events varied with each location and can be seen in Table 1.

Table 1: Shows the timing of the 9.2 kya event. Also compares the climate anomalies between the 9.2 and 8.2 kya events (from Fleitmann et al., 2008, Table 1, pg. 4, shown with permission from Journal of Paleoceanography).

8.2 kya event

The last major climate event noticed in the Twin Ponds core and perhaps the largest of the Holocene is the 8.2 kya event. The most widely accepted hypothesis for

28 this event is that the mechanism is similar to that of the 9.2 kya event, with freshwater being released from glacial Lake Agassiz into the North Atlantic and interrupting the thermohaline circulation. The most common route for these meltwater pulses was route C (Figure 9) through the St. Lawrence Valley. However, the meltwater released prior to the 8.2 kya event was released through the Hudson Strait (route B-Figure 9)

(Kerwin, 1996). Prior to the 8.2 event there were still remnants of the Laurentide Ice

Sheet covering Hudson Bay which acted as a dam, holding in glacial Lake Agassiz and

Lake Objiway (Veillette, 1994). The collapse of the ice covering Hudson Bay prior to the

8.2 kya event marked the termination of the Laurentide Ice Sheet (Kerwin, 1996). When the ice sheet collapsed it blocked the southeastern passage through the St. Lawrence

Valley and sent the water through Hudson Strait into the Labrador Sea (Barber et al.,

1999). The presence of a ‘red bed’ in Hudson Strait is believed to be related to the large pulse of meltwater released after the collapse of the ice sheet. This layer of hematite rich silt and clay was deposited throughout Hudson Strait as a result of the collapsed ice sheet (Kewin, 1996). With this deposition occurring at a time that the strait was free of ice, it is believed that only a large transport mechanism such as a large outburst flood from Lake Agassiz and Lake Objiway could have provided the mechanism for deposition of the ‘red bed’ (Andrews et al., 1995; Barber et al., 1999).

One alternative hypothesis suggests the 8.2 event could have been caused by a minimum in solar activity. This study by Muscheler et al., (2004) uses 10Be and 14C to reconstruct past solar activity. Production of these cosmogenic radionuclides varies with changes in solar activity. Both 10Be and 14C methods have their advantages and

29 disadvantages. 10Be can provide a more direct measure of past solar activity because it is usually removed from the atmosphere within 1 to 2 years, making it a good proxy for past production rates. However, because it only stays in the atmosphere for a short period of time, it may be subject to some local component influence. 14C on the other hand, stays in the atmosphere for longer. However, because of the long residence time in the atmosphere and the mixing between the atmosphere, oceans and biosphere, the interactions can be complex and there are often delays in the record. By correlating the

10Be and 14C from the GRIP (Greenland Ice Core Project) core, Muscheler et al., (2004) were able to determine that the 8.2 kya event occurred during a time of low solar activity. This solar minimum may have forced the system to cross a threshold and possibly triggered the 8.2 kya event (Bond et al., 2001).

The cool, dry conditions associated with the 8.2 kya event were very widespread.

It has been documented in the Greenland ice cores where it was noted to be nearly half the magnitude of the Younger Dryas (Alley et al., 1997). Similar effects have been observed in Europe (Klitgaard-Kristensen et al., 1998; von Grafenstein et al., 1998) and

North America (Dean et al., 2002; Shuman et al., 2006). The 8.2 kya event also seemed to have an impact on the monsoon seasons of China, Oman and Brazil. During the 8.2

China and Oman experienced a weak summer monsoon, while the South American

Summer Monsoon seems to have gotten stronger over eastern Brazil. Cheng et al.,

(2009) relate these changes in monsoon strengths to changes in the Atlantic Meridional

Overturning Circulation from the meltwater input in the North Atlantic. The climate

30 over the North Atlantic changed and as a result so did the position of the Intertropical

Convergence Zone.

The exact timing of the 8.2 kya event is up for debate. Barber et al., dated the discharge of Lake Agassiz into the North Atlantic at 8,470 BP. However, it is may be possible that the discharge of Lake Agassiz may have taken decades to complete or may even have been split into multiple discharges (Smith et al., 2011). Also, once the glacial meltwater reached the North Atlantic, the climate effects would not be immediate and may have taken decades before significant climatic shifts were noticed. The 8.2 kya event was dated in Greenland ice cores to be 8186 ±47 BP (Rasmussen et al., 2006). The event has also been dated in Greenland ice cores over a period of 160.5 years by

Thomas et al., 2007 (between 8247-8297 BP and 8086-8136 BP). Although there is some disagreement between the dates, it is still widely accepted that the event occurred at around 8.2 kya, the differences in dates are possibly the result of radiocarbon calibration differences (Smith et al., 2011).

Methods

The core for this study was obtained by Dr. Bryan Shuman and his graduate student Jeremiah Marsicek from the University of Wyoming. They traveled to Twin

Ponds, Vermont in early November, 2012 and collected a 3-meter long core from the western basin on the edge of a wetland (core location shown in Figure 3). The core was split into 1-meter long drives and shipped back to the University of Wyoming.

I sampled the core in late November of 2012. The total depth of the core was

272cm and samples were taken every centimeter and placed into labeled Whirlpack® bags. Since this is a multi-proxy effort, separate samples were taken for ostracodes, pollen, LOI, charcoal and bulk carbonate isotope analysis. The samples designated for ostracode analysis were shipped to Kent State. Pollen samples were sent to Dr. Laurie

Grigg at Norwich University in Vermont. The remaining samples stayed at the University of Wyoming for analysis.

The process for acquiring the ostracodes from the samples was split into 3 parts: washing, freeze drying and picking. These procedures took place in the Paleolimnology

Lab at Kent State. The washing process involved using 8 inch diameter brass sieves with

32 openings of 850, 150, and 63 microns (20, 100 and 230 mesh). The 850 μm sieve collected all of the larger particles, such as wood fragments. The 150 μm sieve collected sand, ostracode carapaces, bivalve and gastropod shells, and Chara fragments. The 63

μm sieve collected the very fine sediment, mostly clay and silt, found in the samples. In some cases the sample was too compacted to be rinsed through the sieves, so the sample was treated with hot water, in which small amounts of baking soda and Calgon were added to help disarticulate it. This process was done by adding 800ml of near boiling water to the sample and immediately stirring in 1 tsp of baking soda. After allowing the water to cool to room temperature ½ tsp of Calgon was added and the water was covered with aluminum foil. After 24-48 hours of sitting in the mixture, the sample was washed through the sieves. The material in each sieve was rinsed into

Whirlpack® bags. The water in the bags was then decanted out so the freeze drying process was more effective.

The samples were then placed in the Virtis Freezemobile 12ES freeze dryer for about 48 hours. Even the smallest ostracode carapaces were collected in the 150 μm sieves, so ostracode picking was only done on these samples. The contents of the 150

μm sample bag were emptied onto a tray to be analyzed under a microscope. Using a very fine-tipped sable paint brush, ostracodes were picked out and placed on a 60-grid slide. Other material such as Chara fragments, gastropod shells and bivalve shells were picked out as well, when present. The ostracodes were then grouped into sections on the slide based on species and counted.

` After all of the ostracodes were counted, the data were analyzed to determine which samples were the best choices for isotope work. Choices were narrowed down to those which contained abundant benthic and nektic species. The benthic species chosen were Pseudocandona stagnalis, Candona candida and Candona ohioensis. The nektic species were Cyclocypris ampla and Cypridopsis vidua. The recommended number of valves for each species, provided by Dr. Emi Ito at the University of

Minnesota is given in Table 2. A total of 70 samples were chosen for isotope analysis. In most cases there were 2 samples per centimeter depth in the core, one benthic and one nektic.

Species Recommended number of valves

Pseudocandona stagnalis 3-5

Candona candida 3-5

Candona ohioensis 2-3

Cyclocypris ampla 15-30

Cypridopsis vidua 20-30

Table 2: Showing the recommended number of valves of each species to be analyzed.

Ostracode Bleaching Procedure

The ostracode preparation took place at the University of Minnesota’s Stable

Isotope Lab from December 3rd through December 7th, 2013. To start, a station was set up under a laminar flow hood for bleaching and rinsing ostracodes. Powder free gloves were worn throughout this entire process. The bleaching process was fairly quick but the rinsing process took about 20 minutes per sample. A select number of samples were bleached at once in order to ensure the ostracodes remained in the bleach for a consistent amount of time.

The first step was to transfer the ostracodes from the container they were transported in, to an acid-washed vial. First, the acid washed vial was labeled with a waterproof marker with the assigned C-number (lab identification number). The ostracodes were then emptied from the travel container into a black picking tray and from there transferred into the labeled acid-washed vial using a fine tipped paint brush.

Next, the vial was filled half full with 50% noncommercial bleach. Often times the ostracode shells floated on top of the bleach instead of sinking, although they need to be fully submerged. Tapping gently on the vial or carefully swirling the bleach around caused most of the shells to sink. However, when both ostracode valves were still articulated, they were difficult to submerge. In order for these to sink, the valves had to be separated, which was done by gently pushing the shell down into the bleach solution with a small glass stirring rod until the valves separated and sank. The shells were then

35 left in the solution for between 23 and 25 hours and the time the ostracodes were submerged was recorded in the ostracode cleaning journal.

After soaking in the bleach for close to 24 hours, the rinsing process was started.

In preparation for the rinsing process it was best to have a large empty beaker and a squirt bottle full of DDI water. It was helpful to have a new set of labeled acid-washed reaction vials on hand that helped keep the process going. These vials were slightly different than the ones used in the bleaching process and did not have a cap. Once the ostracodes were transferred into these vials they were then transferred into the Kiel device of the Finnigan MAT 252 mass spectrometer for analysis to begin. But first the shells needed to be rinsed. The first step was to empty the ostracodes onto a plexi-glass tube with a nylon mesh bottom which was placed on top of a Petri dish. The mesh collected the ostracodes and allowed for thorough rinsing. By squirting DDI water down the sides of the plexi-tube water did not directly hit the shells and they were less likely to break. When the plexi-tube was halfway filled with DDI water, it was lifted up to allow the water to drain out into the Petri dish. This process was repeated for 12-15 minutes. Once fully rinsed, the shells were positioned in the middle of the plexi-tube, and a couple drops of alcohol were dripped on them to help speed up the drying process. Because this process was time consuming, it was most efficient to perform this process with multiple samples at once. For example, while two samples are drying in plexi-tubes, another 2 samples were being rinsed. Once the shells have dried, it was time to transfer them into the labeled reaction vials. Using a sable paintbrush, the desired amount of carapaces was carefully transferred into the reaction vials and

36 recorded. If there were any remaining, they were transferred back into the original vials in which they were transported.

Running samples on the Kiel

The isotope analysis began on December 5th, 2013 and was concluded on

December 11th. The analysis was run using a Finnigan MAT252 Mass Spectrometer with a Kiel device. After the ostracode bleaching process was completed the reaction vials containing the samples were placed into a carousel. The C-numbers of the reaction vials were input into a computer based on the position of the vials in the carousel. The hand written list of C-numbers was then checked with the computer input to ensure no mistakes occurred. There are 48 positions on the carousel, 24 on an inner ring and 24 on an outer ring. The first position of each line is always occupied by a clean, empty vial in order to maintain a vacuum when the sample is not reacting. The 2nd, 13th and 24th position of each line contained a powder which was used as the standard leaving 40 open positions. As the samples were being loaded, the vials were checked to ensure that the ostracodes were on the bottom of the vial. Sometimes static would cause the ostracodes to stick to the sides of the vial. In these cases, tapping on the vial usually made them fall to the bottom. After the vials were all loaded into the carousel, the sealing surface on the reaction vial was cleaned using a Kimwipe and methanol. If the sealing surface was not clean, a vacuum would not be established and the analysis

37 would stop. The carousel was then loaded into the Kiel II. The Kiel II is a carbonate auto extraction unit for the Finnigan MAT252. The Kiel II measures 44, 45 and 46 CO2 by reacting the sample with 2 drops of phosphoric acid made in the lab. Once the temperature reaches 70oC inside the Kiel, analysis is ready to start. On average, each sample took about 30 minutes to run, so the machine would take about 20 hours to complete a run of 40 samples if it was uninterrupted.

Often times the machine would run into a problem and the analysis would stop.

For example, if there was some dust on the reaction vial and the vacuum did not seal properly, the analysis would stop until the problem was fixed. Or there would be a problem and the acid would not drop in time, which would also stop the analysis.

Reporting

The first samples run were trial runs for each of the ostracode species being used in the analysis. This was done to ensure that the correct number of valves was used in each sample. If the sample size was too large or too small the analysis would not be as reliable. Sample size was reported in volts (mass of 44 CO2) and samples in which volts were lower than 2 were too small and above 6 were too big. One sample in the analysis was slightly below 2 volts and the rest were between 2 and 6 volts. Of the 70 samples that were run, only 3 were classified as possibly having a poor analysis. One sample was

38 too small and the volts were less than 2. The other 2 were reacted with too much acid, which may have skewed the results. The δ13C and δ18O results were reported relative to the Vienna Pee Dee Belemnite (VPDB) standard. The input and output data can be seen in Appendix B. The VPDB values were then converted to Vienna Standard Mean Ocean

Water (VSMOW) using the following equation from Coplen et al., (1983):

The VSMOW δ18O values were also adjusted for temperature using the following formula from Kim and O’Neil (1997) which was later revised by Ito et al., (2003):

)

Temperature ranges were chosen from the North American Combined Ostracode

Database (NACODe) (Curry et al., 2013). From these ranges, the species associated with ecological preferences for the coldest temperatures in each isotope sample was chosen to be the basis for the temperature adjustment in the conversion from VPDB to

VSMOW. The three species with known ecological preferences for the coldest temperatures from the samples chosen for isotope analysis were Pseudocandona stagnalis, Candona candida and Cyclocypris ampla. Table 3 shows the air, surface water and bottom water temperature from NACODe for selected ostracode species.

Temperatures for Cyclocypris globosa were not used in the analysis because there were none found in the samples chosen for isotope analysis. For a complete list of the SMOW values see Appendix C.

Min Air Max Air Min Max Min Max

Species Temp Temp Surface Surface Bottom Bottom

Cyclocypris globosa 11 21 4 18 4 17.2

Candona ohioensis 7 35 9 28.1 6 28.1

Candona candida 3 34.6 7 24.6 5.5 28

Candona

paraohioensis 5 32.9 8.9 26.4 8.9 26.4

Pseudocandona

stagnalis 10 28.6 8 21 7.2 29.8

Cyclocypris ampla 3 37.2 6.5 30 3 30

Table 3: Showing the minimum and maximum temperatures for air, surface water and bottom water for the area in which each ostracode species was collected. The data used for determining this was from NACODe (Curry et al., 2013).

Statistical Analysis

For this study I used two types of multivariate statistical analysis to organize the ostracode data: cluster analysis and principal components analysis (PCA). Both of these methods are a type of ordination method, which is a statistical procedure in which the data are placed in a logical order based on similarities (Davis, 1986). Cluster analysis does this by creating cluster trees of the data in which groupings of related data are distinct from other groups. Cluster analysis draws the clusters from a similarity or dissimilarity matrix, using a variety of methods to build the cluster, such as Farthest

Neighbor, Nearest Neighbor, or Centroid (Davis, 1986). PCA is another ordination method and like clustering it seeks to group the data based on similarities. However, it does this by extracting multiple axes from a correlation matrix, and these axes are orthogonal and independent of each other. By plotting the axes against each other on scatter plots it is possible to observe which variables are driving each axis. Because the resolution of the core during the past 8000 years was variable, the statistical analysis focused on the time from 8000 cal. yr. BP to 13000 cal. yr. B.P. Additionally, juveniles of

Candona and Cyclocypris globosa were excluded from the analysis. Juveniles of

Candona could not be identified to the species level which would complicate the analysis and Cyclocypris globosa was not abundant enough to include. Lastly, the basal

16cm of the core was excluded from the statistical analysis as well because an accurate radiocarbon age could not be obtained.

Cluster Analysis

Cluster analysis of ostracodes from the Twin Ponds core focused on the time period from 7961.67 to 12969 cal. yr. BP which is from depths to 87.5 to 255.5cm in the core. The analysis was run using Multi-Variate Statistical Package (MVSP) Version 3.22

(Kovach, 1985-2014). A constrained cluster analysis was run using the Farthest

Neighbor clustering method and Squared Euclidean distance measure. Farthest

Neighbor and Squared Euclidean distance were chosen because they produced a dendrogram with more distinct clusters than any other clustering method/distance measure combination. Farthest Neighbor takes the distance between the two farthest points between two groups and the formula used by MVSP to perform the Squared

Euclidean distance measure is:

(Kovach, 1985-2014)

Principal Components Analysis (PCA)

Like the cluster analysis, PCA was performed using MVSP Version 3.22 (Kovach,

1985-2014). The same data used in the cluster analysis were also used in PCA (core

42 depths 87.5-255.5cm). Under the ‘PCA Analysis Options’ menu in MVSP, Centre data and Standardize data were selected and all axes were extracted to ensure all of the variance was explained. The program was also instructed to create a correlation matrix and also to leave Candona juveniles and Cyclocypris globosa out of the analysis. The first three axes explained the majority of the variance (65.92%), so scatter plots were created showing Axes 1 vs. 2 (Figure 18), Axes 1 vs. 3 (Figure 83) and Axes 2 vs. 3 (Figure

84). Results and interpretation of these plots can be seen starting on page 81.

Results

Multi-Proxy Work

This project was done with collaboration from researchers at the University of Wyoming and Norwich University. Dr. Laurie Grigg from Norwich University will be conducting the pollen research. Dr. Bryan Shuman and his Ph.D. student, Maximilian Mandl have completed the bulk carbonate oxygen isotope analysis, loss on ignition and the age model used for this research.

Age Model

The age model used as reference for this project was developed by Dr. Bryan Shuman at the University of Wyoming. The age model is displayed in Figure 11 which shows the calibrated dates plotted on a time vs. depth plot. The Late Glacial-Early Holocene time period is inferred from the calibrated dates (Note: the last 15 cm of the core were not able to be dated). The later part of the Holocene is not well defined in the core, which can also be seen by the lack of sediment accumulation shown in the age model. The time period that is not well defined is seen in the core as shown in Figure 12. This figure shows that the hiatus falls on a boundary between the two drives. One possible explanation for the hiatus may be related to the drive

44 boundary in the core, in which some sediment may be have fallen out or been mixed along the boundary. There is a sharp contrast in the color of the sediment present between the two drives, which may indicate a large amount of missing sediment. Another explanation for the hiatus may be the result of a lack of sedimentation. Since the core was taken on the edge of the lake, it is possible that at some point during the history of the lake, its boundaries have shifted. If this is the case, then there may not have been sedimentation during the time period.

The hiatus could also be a combination of these two hypotheses, with the core boundary and a lack in sedimentation contributing to the missing sediment.

100

Depth (cm) Depth 150

200

250

271 10 5 0 Bottom of Core k cal yrs BP

Figure 10: Age model for the Twin Ponds core. Developed by Dr. Bryan Shuman at the University of Wyoming.

Figure 11: Picture of the core at the sediment depositional hiatus interval from the Age Model. This figure shows a drive boundary occurring during this interval.

Bulk Carbonate δ18O

The bulk carbonate oxygen isotope analysis was conducted at the University of

Wyoming by Dr. Bryan Shuman and his graduate student, Maximilian Mandl. Based on observations of the samples throughout the core, the bulk carbonate analysis was drawn mainly from Chara and shell material from bivalves, gastropods and ostracodes.

The core consists predominantly of marl which is formed from Chara, meaning the bulk carbonate analysis is mainly reflecting δ18O of the Chara. This is seen in the results of the bulk carbonate analysis in Figure 12, in which the δ18O values are low. Chara precipitates its calcite coating onto the stems and leaves very fast, therefore it does not usually have a preference of the lighter or heavier isotope and will have an isotopic composition very near to that of the water (McConnaughey, 1998 and McConnaughey et al., 1994). Animals that require a shell such as a mollusk or ostracode tend to take longer to precipitate their shells. They accept higher amounts of the heavier isotope and therefore, will often have an isotopic composition that is heavier than the water.

Many of the climate events described in the introduction are visible here in the bulk carbonate isotope record. There is a very clear signal shown by the extremely low δ18O values between 13000 and 11500 cal. yrs. B.P, corresponding to the Younger Dryas.

There is also a large drop in δ18O values around 9.2 cal. yrs. B.P. which may be the result of the 9.2 kya event. Another drop in values is seen around the time of the 8.2 kya event. There is also a signal of slightly higher δ18O values immediately following the

Younger Dryas, sustained until about 10,500 cal. yrs. B.P. which could be related to the

Post-Younger Dryas interval.

Twin Ponds, VT 18 -9 Bulk Carbonate δ O VPDB

-9.5

-10

-10.5

O ‰ VPDB ‰ O 18

δ -11

-11.5

-12 8000 9000 10000 11000 12000 13000 Cal. Yrs

Figure 12: Bulk carbonate δ18O profile of Twin Ponds, from Dr. Bryan Shuman at the University of Wyoming.

Loss on Ignition

The Loss on Ignition (LOI) analysis was also conducted by Dr. Bryan Shuman and his graduate student Maximilian Mandl at the University of Wyoming. The results of the analysis can be seen in Figure 13 which shows the percent dry mass of organics, carbonate and clay in the core from 13000 to 8000 cal. yrs. B.P. As is expected in a marl lake such as Twin Ponds, the carbonate content is high (usually above 80%) from the large amounts of Chara produced at the lake. The Younger Dryas is the most noticeable of the climate events seen in the LOI results. There is a significant drop in carbonate content at Twin Ponds during the Younger Dryas along with an increase in clay content.

These same results can be seen when comparing the Younger Dryas section of the core to a typical section of the same core seen in Figure 14. A typical core section such as that seen from 10760-11080 cal. yrs. B.P. consists of carbonate rich marl bands, whereas the Younger Dryas consists of gray clay indicating increased erosion derived sediments and decreased carbonate content.

Twin Ponds, VT Loss on Ignition Data 100

60 % Organics 50 %

40 Carbonate % DryMass % 30

0 8000 9000 10000 11000 12000 13000 Cal. Yrs.

Figure 13: Loss on Ignition profile of Twin Ponds, from Dr. Bryan Shuman at the University of Wyoming.

Typical Core Section Younger Dryas

10760 Cal. yr 11500 Cal. yr.

12769 Cal. yr. 11080 Cal. yr.

Figure 14: Comparison of a typical core section with the Younger Dryas section of the core. Images taken by Dr. Bryan Shuman at the University of Wyoming

Ostracode Abundances

There were eight common species of ostracodes present throughout the core:

Candona ohioensis, Candona paraohioensis, Candona candida, Pseudocandona stagnalis, Cypridopsis vidua, Cyclocypris ampla, Cyclocypris globosa and Darwinula stevensoni (See Figure 15). Of these eight, isotope analysis was performed on five:

Candona ohioensis, Candona candida, Pseudocandona stagnalis, Cypridopsis vidua and

Cyclocypris ampla. The following pages will address each of these ostracode species.

Candona ohioensis Furtos, 1933

Candona ohioensis is the largest ostracodes found in the Twin Ponds core, commonly 1.65 to 2mm long (Delorme, 1970b). This benthic species of ostracode prefers permanent lake settings with warmer freshwater and summer temperatures above 20oC (Smith, 1997). C. ohioensis also prefers fresh waters with high bicarbonate concentrations and disappears from the record if the area is experiencing increases in total dissolved solids (TDS) (Smith, 1993; Smith et al., 1997). This makes C. ohioensis an indicator of freshwater lakes with low TDS values (Schwalb et al., 1995). See Figure 15 for photos of Candona ohioensis.

In the Twin Ponds core, C. ohioensis appears almost simultaneously with the 9.2 kya event. There may be a connection with the two, but it cannot be determined from the data. The appearance of C. ohioensis is more likely related to the condition of the lake. Since C. ohioensis prefers more permanent lake settings its appearance suggests that the condition of the lake before this time was much more variable. The appearance of C. ohioensis at Twin Ponds also marks one of the easternmost appearances of the species, which is usually found in the midcontinent (Forester et al., 2005).

Candona candida (O.F. Müller, 1776)

Candona candida is another large ostracode, ranging from 1.06-1.22mm in length

(Delorme, 1970b). This benthic species occurs in lakes, ponds, streams and springs and can tolerate a wide range of TDS values (Forester et al., 1987). C. candida prefers lakes with cold water and usually a cold groundwater input as well. This means C. candida is an indicator of cold, dry conditions that were typical during the late Glacial (Schwalb and

Dean, 1998). Adults of C. candida are abundant in early winter through the spring and usually disappear by the summer (Von Grafenstein et al., 1999). See Figure 15 for photos of Candona candida.

Candona candida is seen throughout nearly the entire core. Its first appearance in Twin Ponds coincides with the beginning of the Younger Dryas. When the Younger

Dryas began, the cool, dry conditions would have lowered the temperature of the water enough for C. candida to move into the lake. Once C. candida appeared in Twin Ponds, the cold groundwater supporting the lake probably allowed it to remain even after the

Younger Dryas had ended. The appearance of C. candida at Twin Ponds also marks one of the easternmost appearances of the species, which is usually found in the midcontinent (Forester et al., 2005).

Candona paraohioensis Staplin, 1963

Candona paraohioensis prefers shallow parts of slightly alkaline lakes and is commonly associated with C. ohioensis and other Candona species. C. paraohioensis is also associated with moderate vegetation: Chara in particular (Staplin, 1963). Males of this species are rare, possibly the result of a parasite which seems to be common among

Candona males (Delorme, 1970b). The length of the species ranges from 1.02 to

1.30mm (Delorme, 1970b). See Figure 15 for photos of Candona paraohioensis.

Candona paraohioensis is slightly variable in its appearance throughout the core, so using it to reconstruct climate conditions may not be accurate. However, there does seem to be a spike in the abundance of C. paraohioensis shortly after the Younger Dryas.

There may be an association between the abundance of C. paraohioensis and an increase in Chara production seen at the beginning of the Post-Younger Dryas interval

56 since the two are often found together (Staplin, 1963). The appearance of C. paraohioensis at Twin Ponds also marks one of the easternmost appearances of the species, which is usually found in the midcontinent (Forester et al., 2005).

Pseudocandona stagnalis (Sars, 1890) Meisch & Broodbakker, 1993

Pseudocandona stagnalis can often be seen in the older literature under the name Candona stagnalis. This species is commonly found in seasonal streams that usually occur during the summer months. Males of this species are rare and females of

P. stagnalis are smaller than most candonids and range in length from .71 to .89mm

(Delorme, 1970b). They also prefer slightly bicarbonate-depleted water (Forester et al.,

2005). See Figure 15 for photos of Pseudocandona stagnalis.

Pseudocandona stagnalis is seen at the very bottom of the core; just before, throughout and briefly after the Younger Dryas until it disappears at 256cm and does not appear again in the core (Figure 16). Its abundance during the Younger Dryas is possibly the result of the slightly bicarbonate-depleted waters as inferred from the LOI data (Figure 13). After the Younger Dryas had ended, Chara production began to return to higher values causing the carbonate concentration in the lake to rise. P. stagnalis was seen at Twin Ponds for a short time after the Younger Dryas but seemed to have abruptly disappeared at about 11,400 cal yrs ago.

Cyclocypris ampla Furtos, 1933

Cyclocypris ampla is a nektic species of ostracode and is most commonly found in springs. C. ampla is often found in lakes indicating they have been washed in or are most likely living in a groundwater discharge zone of the lake (Smith and Delorme,

2009). C. ampla is the most common Canadian ostracode and can tolerate a wide range of TDS values (Bunbury and Gajewski, 2005). Like most nektic ostracodes, they are smaller than the benthics, ranging from .60 to .76mm (Delorme, 1970a). See Figure 15 for photos of Cyclocypris ampla.

Cyclocypris ampla appears in Twin Ponds around the middle of the Younger

Dryas. The reason for the appearance of C. ampla during the Younger Dryas is most likely similar to that of C. candida. During the Younger Dryas, the polar front expanded south, and with it so did C. ampla. When it retreated back north after the Younger

Dryas, C. ampla remained in the lake because of the cold, groundwater source. The abundance of C. ampla may be related to the length of summer, which is discussed next along with Cypridopsis vidua.

Cypridopsis vidua (O.F. Müller, 1776)

Cypridopsis vidua is one of the most environmentally tolerant ostracodes and can be collected in a very wide range of salinities and climate conditions (Curry, 1999).

Another nektic ostracode, C. vidua is a good swimmer and likes to live close to the surface of the water or on a macrophyte (Von Grafenstein et al., 1999). C. vidua also prefers to live in interstitial habitats, living in between grains or within algae communities (Roca and Danielopol, 1991). C. vidua is slightly larger than C. ampla with a length of .73-.86mm (Delorme, 1970a). See Figure 15 for photos of Cypridopsis vidua.

Cypridopsis vidua is found in nearly every sample taken from the core. Because this ostracode has such a high tolerance for changing environmental conditions, its presence alone cannot be used to accurately determine past climate conditions.

However, it does prefer to live in within algal communities, and its presence does often seem to increase along with the other common nektic ostracode, C. ampla. The nektic ostracodes reach maturity during the summer, so a longer summer would mean increases in C. vidua and C. ampla. The longer summers would also mean longer growing seasons for Chara and more habitats for C. vidua. Large abundances for in the nektic species can be seen following the Post-Younger Dryas interval, which would have had longer, warmer summers.

Darwinula stevensoni (Brady & Robinson) 1890

Darwinula stevensoni is a very interesting ostracode species and has been the subject of much research. It is considered one of the oldest living asexual species, dating back 25 million years ago which allows for research into ancient asexuality (Von

Donick et al., 2003). D. stevensoni is another benthic ostracode, another indicator of groundwater discharge and has been collected in many different parts of the globe

(Ranta, 1979; Schwalb et al., 1995). D. stevensoni ranges in length from .66 to .83 mm and has a ‘wedge shaped’ appearance, with each end slightly rounded (Delorme, 1970c).

In addition to its very distinct appearance it also has a very little variability in size shape making it very easy to identify (Gandolfi et al., 2001). See Figure 15 for photos of

Darwinula stevensoni.

Darwinula stevensoni is another indicator of groundwater discharge but does not appear in Twin Ponds until after the Younger Dryas. The area could have possibly been too cold during that time. The appearance of D. stevensoni correlates with high abundances of C. paraohioensis which may have been the result of warmer temperatures towards the end of the Post-Younger Dryas interval.

Cyclocypris globosa (Sars, 1863)

Living specimens of Cyclocypris globosa are found today in the northern parts of the Northwest and Yukon territories in Canada. The presence of C. globosa is an indicator of an alpine tundra or subarctic forest (Delorme and Zoltai, 1984). C. globosa is another nektic ostracode but is also commonly found attached to amphibians or plants (Seidel, 1995). C. globosa is very similar in appearance to C. ampla, just larger.

Cyclocypris globosa was not very abundant in the core, in fact only 8 specimens were found in the entire core. However, the presence alone of C. globosa can provide some insight into the environmental conditions of Twin Ponds. As seen in Figure 12, C. globosa first appears in the core before the Younger Dryas. There is no radiocarbon age for this sample, but based on the preceding chronology and assuming a uniform sediment accumulation rate, it looks to be close to 14,000 cal. yr. B.P. (1,000 years before the Younger Dryas). This time frame is usually associated with the Bølling-

Allerød warm period, making the presence of C. globosa even more unusual, if the above chronology for the core is accurate. The reason for the presence of C. globosa is possibly the result of the influence of cold, groundwater supporting the lake. Another, explanation could be that the proximity of Twin Ponds to the Laurentide Ice Sheet southern boundary caused the site to experience colder conditions. It could also be a combination of these factors, with the ice sheet bringing about the cold conditions, which caused C. globosa to appear, and the cold groundwater supporting the species

61 throughout the late Pleistocene and early Holocene. C. globosa is seen until around

10,500 cal. yrs B.P., which coincides well with end of the Post-Younger Dryas interval.

After this interval ended, the seasonal temperatures were no longer cold enough to support C. globosa in the region.

Figure 15: Twin Ponds Ostracode Plate:

A) Cyclocypris ampla Furtos, 1933: 37-38 cm, drive 2 B) Cyclocypris globosa (Sars, 1863): right valve, 36-37 cm, drive 2 C) Pseudocandona stagnalis (Sars, 1890): left valve, 64-65 cm, drive 3 D) Candona paraohioensis Staplin, 1963: right valve, 30-31 cm, drive 2 E) Candona candida (O.F. Müller, 1776): left valve, 43-44 cm, drive 2 F) Paracandona euplectella (Robertson, 1889): left valve, 46-48 cm, drive 2 G) Darwinula stevensoni (Brady & Robertson, 1870): left valve, 37-38 cm, drive 2 H) Candona ohioensis Furtos, 1933: right valve, 47-48 cm, drive 2

8.2

9.2

10558 10844 11046 11416 YD

Figure 16: Profile showing the abundances of ostracodes at Twin Ponds, Vermont from a 280 cm long core. The blue box highlights the Younger Dryas cooling event as inferred from the radiocarbon chronology. The red and green lines highlight the 9.2 and 8.2 kya events, respectively. The interpolated dates for the appearance of Cyclocypris globosa are given as well. A full list of the ostracode counts can be seen in Appendix D.

Cluster Analysis--Ostracode Zones

Of the 272 samples taken from the core, 169 were chosen for the cluster analysis.

The most recent 8,000 years of the Holocene at Twin Ponds were poorly constrained by the radiocarbon record, and showed evidence of unconformities in the core. For this reason, this study focused on the late Pleistocene to early Holocene time period and therefore the cluster analysis focuses on this time range. The basal 16 cm of the core were not included in the cluster analysis, again because of poor temporal resolution. By correlating the cluster analysis with the ostracode abundance chart I was able to distinguish 5 distinct ostracode zones. These zones were chosen based on the abundance in terms of valves per gram as well as first appearances of some species

(Figure 16). The 5 zones were labeled as follows: P. stagnalis, C. ampla, D. stevensoni,

Nektic, and C. ohioensis.

Twin Ponds Core Dendrogram (87.5 to 255.5cm ) 8,000 C. ohioensis (87.5-111.5 cm) 9,000

(111.5-146.5 cm) Nektic

10,000 Cal. Cal. Yrs. B.P.

D. stevensoni

(146.5-203.5 cm) 11,000

(203.5-247.5 cm) C. Ampla and P. stagnalis

12,000 C. candida (247.5-255.5 cm)

60,000 50,000 40,000 30,000 20,000 10,000 0 Squared Euclidean

Figure 17: Dendrogram showing 5 zones identified in the core from the late Glacial to early Holocene.

C. candida Zone

It is important to note that the base of the cluster diagram is not the base of the core. This first zone in the core is named after Candona candida and is seen at the very bottom of the dendrogram in Figure 17. It is also the narrowest zone, consisting of only

8 samples. It is seen at depths 247.5-255.5cm in the core which translates to 12,969-

12,501 cal. yrs. B.P. or the start of the Younger Dryas. Table 4 shows the abundances in terms of valves per gram of the ostracode species present in this zone. Ostracodes are not very abundant during the early parts of the Younger Dryas and seem to be dominated by Candona candida and Pseudocandona stagnalis. The presence of C. candida during the Younger Dryas is no surprise as it is seen throughout the rest of the core as well and is an indicator of cold groundwater discharge. P. stagnalis is only seen at Twin Ponds during and briefly after the Younger Dryas. Its presence may be a result of the slightly bicarbonate depleted water during the Younger Dryas.

C. Candida Zone

Valves per

Species Total Gram

Cypridopsis vidua 63.00 1.17

Cyclocypris ampla 2.00 0.03

Candona ohioensis 0.00 0.00

Candona

paraohioensis 14.00 0.26

Darwinula stevensoni 0.00 0.00

Pseudocandona

stagnalis 19.00 0.33

Candona candida 30.00 0.55

Table 4: Showing the abundances of ostracodes in the P. stagnalis Zone in terms of valves per gram and total abundance.

C. ampla and P. stagnalis Zone

The next zone is the C. ampla and P. stagnalis Zone which is seen directly after the C. candida Zone and begins during the Younger Dryas. This zone consists of 44 samples and is based on the first appearance of Cyclocypris ampla at a depth of

247.5cm. The core spans from 247.5-203.5cm which correlates to 12,434-10,961 cal. yrs. B.P. Because C. vidua is so abundant throughout the core, most of the zones identified here are based on the next most abundant ostracode species. This zone begins with the first appearance of C. ampla which may be related to the summer position of the Polar Front, a possibility addressed later in the Discussion section. This zone ends about 500 years after the Younger Dryas, so it sees the disappearance of P. stagnalis from Twin Ponds which is why P. stagnalis is included in the name. Table 5 shows the abundances in terms of valves per gram of the ostracode species present in this zone.

C. ampla Zone

Valves per

Species Total Gram

Cypridopsis vidua 1268.00 3.69

Cyclocypris ampla 290.00 0.83

Candona ohioensis 0.00 0.00

Candona paraohioensis 129.00 0.35

Darwinula stevensoni 0.00 0.00

Pseudocandona

stagnalis 53.00 0.15

Candona candida 23.00 0.07

Table 5: Showing the abundances of ostracodes in the C. ampla Zone in terms of valves per gram and total abundance.

D. stevensoni Zone

This zone is based on the first appearance of Darwinula stevensoni in the core.

This is the largest zone identified in the cluster tree consisting of 57 samples and ranging from 203.5-146.5cm. This zone encompasses the majority of the ‘Post-Younger Dryas’ interval spanning from 10,945-10,002 cal. yrs. B.P. The environment at Twin Ponds during this time was very similar to the environment towards the end of the C. ampla

Zone and sees a similar abundance in C. ampla between the two. This zone was picked out of the cluster tree because it marks the first appearance of D. stevensoni which is very abundant during this time frame. D. stevensoni is another indicator of groundwater discharge but did not show up until after the Younger Dryas, possibly because temperatures were too cold. C. paraohioensis also increases during this time, which may be a result of increased vegetation. C. paraohioensis is commonly associated with the algae Chara (Staplin, 1963) which is very abundant at Twin Ponds and most likely increased in production after the Younger Dryas, which is evident by the increase in carbonate seen in the LOI data (Figure 13). Table 6 shows the abundances in terms of valves per gram of the ostracode species present in this zone.

D. stevensoni Zone

Valves per

Species Total Gram

Cypridopsis vidua 1682.00 3.69

Cyclocypris ampla 448.00 0.98

Candona paraohioensis 611.00 1.19

Candona ohioensis 0.00 0.00

Darwinula stevensoni 649.00 1.33

Pseudocandona

stagnalis 0.00 0.00

Candona candida 174.00 0.35

Table 6: Showing the abundances of ostracodes in the D. stevensoni Zone in terms of valves per gram and total abundance.

Nektic Zone

This zone is based on the high abundances of the nektic ostracodes Cyclocypris ampla and Cypridopsis vidua. It consists of 35 samples and ranges in depth from 146.5-

111.5cm. This correlates to 9,986 to 9,215 cal. yrs. B.P. The increase in abundances, particularly that of C. vidua may be attributed to a rise in Chara production. This zone marked the end of the ‘Post-Younger Dryas’ interval which meant that temperatures are generally higher during this time, than during the earlier part of the core. This would mean longer summers and a longer growing season for Chara, which is often associated with C. vidua. The nektic ostracodes also reach maturity during the summer, so a longer summer could mean more of the swimmers becoming adults. Table 7 shows the abundances in terms of valves per gram of the ostracode species present in this zone

Nektic Zone

Valves per

Species Total Gram

Cypridopsis vidua 1508.00 5.76

Cyclocypris ampla 1331.00 5.13

Candona paraohioensis 177.00 0.68

Candona ohioensis 0.00 0.00

Darwinula stevensoni 187.00 0.69

Pseudocandona

stagnalis 0.00 0.00

Candona candida 55.00 0.20

Table 7: Showing the abundances of ostracodes in the Nektic Zone in terms of valves per gram and total abundance.

C. ohioensis Zone

The last zone to be described in this study is the C. ohioensis Zone which began with the first appearance of Candona ohioensis. This zone consists of 25 samples and ranges in depth from 111.5-87.5cm. This correlates to 9,181 to 7,961 cal. yr. B.P. The abundances of C. vidua and C. ampla are still relatively high, indicating the warmer temperatures from the last zone have carried over to this one. The first appearance of

C. ohioensis is another indicator of warmer temperatures, as it prefers to live in warmer freshwater with summer temperatures above 20oC (Smith, 1997). Another feature of C. ohioensis is that it strongly prefers permanent lake settings, which in combination with its preference for warmer temperatures indicates that the condition of the lake before this zone was slightly cold and too variable for C. ohioensis to make its home. Table 8 shows the abundances in terms of valves per gram of the ostracode species present in this zone.

C. ohioensis Zone

Valves per

Species Total Gram

Cypridopsis vidua 768.00 3.88

Cyclocypris ampla 806.00 4.10

Candona

paraohioensis 56.00 0.26

Candona ohioensis 142.00 0.69

Darwinula stevensoni 64.00 0.31

Pseudocandona

stagnalis 0.00 0.00

Candona candida 24.00 0.12

Table 8: Showing the abundances of ostracodes in the C. ohioensis Zone in terms of valves per gram and total abundance.

Principal Components Analysis (PCA)

The PCA analysis of the ostracode data in the Twin Ponds core for the late

Pleistocene to early Holocene showed 65.92% of the variance explained by the first 3 axes and 77.64% explained by the first 4 axes (Table 9). The PCA variable loadings show

Axis 1 accounts for 29.06% of the variance and is dominated by the group of Candona paraohioensis, Darwinula stevensoni and Candona candida and the group of Candona ohioensis, Cypridopsis vidua and Cyclocypris ampla. Axis 2 accounts for 22.65% of the variance and is dominated by Cypridopsis vidua, Cyclocypris ampla and Pseudocandona stagnalis. Axis 3 accounts for 14.21% of the variance and is dominated by Candona ohioensis and Cypridopsis vidua. Finally, Axis 4 accounts for 11.72% of the variance and is dominated by Candona ohioensis, Cyclocypris ampla and Pseudocandona stagnalis.

In Figures 18, 21 and 22, Axes 1, Axis 2 and Axis 3 were plotted against each other on scatter plots. Based on these plots and the PCA variable loadings in Table 9,

Axis 1 and Axis 2 provided the most information about the dataset. Axis 1 is dominated by the group of Candona paraohioensis, Darwinula stevensoni and Candona candida and the group of Candona ohioensis, Cypridopsis vidua and Cyclocypris ampla. One end of the axis indicates a groundwater controlled spring complex by showing the cluster of C. paraohioensis, D. stevensoni and C. candida. The other indicates a more stable open lake environment by showing both littoral and benthic ostracode species in a group.

The position of Pseudocandona stagnalis in Figures 18, 21 and 22 may indicate that this

78 species prefers the lake margin or wetland area. Axis 2 is dominated by Cypridopsis vidua and Cyclocypris ampla, while Axis 3 is dominated by Candona ohioensis. These 2 axes seem to be independent with Axis 2 being dominated by nektic ostracodes and Axis

3 being dominated by C. ohioensis which prefers a permanent lake setting. These 2 axes appear to support Axis 1 by independently showing the range of species found in a permanent lake setting with littoral ostracodes dominating Axis 2 and benthic ostracodes dominating Axis 3. Figure 18 shows the comparison of Axis 1 and Axis 2.

Figures 21 and 22 compare Axis 1 and Axis 2 to Axis 3 in order to confirm the influence of the first 2 axes and better show the groupings discussed earlier.

Figure 20 reinforces what is seen in Figure 18 by plotting the PCA case scores from Axis 1 and 2 versus the depth in the core. There are two noticeable spikes in each of the axes which indicate the depth that each of the driving species was most dominant. The spike in Axis 1 is shown in red and indicates a time when Candona paraohioensis, Darwinula stevensoni and Candona candida were most dominant. This spike shows when the lake most established as a groundwater controlled environment and not a permanent lake setting. The spike in Axis 2 is shown in blue and indicates a time when Candona ohioensis, Cypridopsis vidua and Cyclocypris ampla were most dominant. This spike shows when the lake was well established as a permanent lake.

Figure 19 is a scree plot which summarizes the eigenvalue data shown in Table 9.

This plot shows confirms that the first 2 axes are of the most importance because they account for the majority of the variance.

Eigenvalues

Axis 1 Axis 2 Axis 3 Axis 4

Eigenvalues 2.034 1.586 0.995 0.82

Percentage of Variance 29.06 22.652 14.211 11.718

Cum. Percentage 29.06 51.711 65.922 77.64

PCA variable loadings

Axis 1 Axis 2 Axis 3 Axis 4

C. ohioensis 0.257 -0.176 0.843 -0.262

C. vidua 0.211 -0.576 -0.455 -0.012

C. paraohioensis -0.563 -0.14 0.086 0.102

C. ampla 0.226 -0.499 0.176 0.667

D. stevensoni -0.494 -0.152 0.206 0.352

P. stagnalis 0.141 0.581 0.035 0.578

C. candida -0.508 -0.086 0.029 -0.135

Table 9: Showing the eigenvalues and variance explained by the first 4 axes and the PCA variable loadings from the PCA analysis of the Twin Ponds core.

Groundwater Discharge Permanent Lake Lake Margin

Figure 18: Scatter plot of Axis 1 vs. Axis 2. Notice the groupings of Axis 1 showing the groundwater discharge species Candona paraohioensis, Candona candida and Darwinula stevensoni and the open lake species Candona ohioensis, Cyclocypris ampla and Cypridopsis vidua.

Figure 19: Scree plot showing the eigenvalues of each axis the PCA analysis by summarizing the data from Table 9.

PCA Case Scores vs Depth in Core 0.5

0.4 0.3 0.2 0.1 Series1Axis 1 0 Series2Axis 2 -0.1

PCA Case Scores PCA -0.2 -0.3 0 50 100 150 200 250 Depth in Core (cm)

Figure 20: Showing the PCA Case Scores vs Depth in Core. The positive red spike shows the dominance of groundwater discharge species in Axis 1. The blue spike shows the dominance of permanent lake species in Axis 2.

Groundwater Discharge Permanent Lake Lake Margin

Figure 21: Scatter plot of Axis 1 vs. Axis 3. Notice the groupings of Axis 1 showing the groundwater discharge species Candona paraohioensis, Candona candida and Darwinula stevensoni and the open lake species Candona ohioensis, Cyclocypris ampla and Cypridopsis vidua.

Figure 22: Scatter plot of Axis 2 vs. Axis 3.

Isotopes

The isotope values for ostracodes from Twin Ponds are reported here in VSMOW values. One benthic and one nektic species were taken from nearly every depth sampled for isotope analysis. This allowed for comparison between the isotope signatures of the benthic species with those of the nektic species. Benthic species molt and calcify new shells throughout the year, whereas nektic species are largely limited to the summer months. Benthic ostracodes will better reflect the changing environmental conditions. These results are evident in the benthic ostracode δ18O VSMOW graphs

(Figures 23 & 24) which show that the δ18O of the benthics picks up climate events such as the 9.2 kya event and the Younger Dryas. In comparison, the nektic ostracode δ18O data (Figures 25 & 26) does not identify any climate events, but instead appears to be quite noisy. For this reason, the remainder of the isotope results and discussion will focus on the response of the benthic ostracodes. The isotope input data can be seen in

Appendix A.

Benthics δ18O VSMOW vs Depth in Core *Based on Minimum 0 Temperature Values

-2 11499.8 kya 9215.03 kya

-4

-6

0 ‰VSMOW 0

18 δ -8

-10

-12 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 Depth in Core (cm)

Figure 23: Twin Ponds benthic ostracodes δ18O compared with depth in the core. Data used for this profile are based on minimum temperature values.

Benthics δ18O VSMOW vs. Age *Based on Minimum Temperature Values 0

-2

-4

-6

O ‰ VSMOWO

18 δ -8

-10

-12 8000 8500 9000 9500 10000 10500 11000 11500 12000 12500 13000 cal. yrs. B.P.

Figure 24: Twin Ponds benthic ostracodes δ18O compared with radiocarbon dates of the core. Data used for this profile are based on minimum temperature values.

Nektic δ18O VSMOW vs Depth in Core *Based on -4 Minimum Temperature Values -5

-6

11499.8

-7 9215.03 kya kya

-8

O ‰ OVSMOW 18

δ -9

-10

-11

-12 0 20 40 60 80 100 120 140 160 180 200 220 240 260 Depth in Core (cm)

Figure 25: Twin Ponds nektic ostracodes δ18O compared with depth in the core. Data used for this profile are based on minimum temperature values.

18 *Based on Nektic δ O VSMOW vs. Age Minimum -4 Temperature Values

-5

-6

-7

-8

O ‰ VSMOWO 18

δ -9

-10

-11

-12 8000 8500 9000 9500 10000 10500 11000 11500 12000 12500 13000 cal. yrs. B.P.

Figure 26: Twin Ponds nektic ostracodes δ18O compared with age from radiocarbon dates of the core. Data used for this profile are based on minimum temperature values.

Benthic δ18O vs. ostracode abundances

Figure 27 correlates the benthic δ18O profile with the ostracode abundance profile shown earlier. This figure shows the three cooling events highlighted across both charts. The Younger Dryas has a clear signal in the isotope analysis but also seems to show up in the abundance profile with the presence of Pseudocandona stagnalis and the appearances of Candona candida and Cyclocypris ampla. The 9.2 and 8.2 kya events are much smaller than the Younger Dryas and as the abundance profile shows, there are no significant changes to the ostracode species present during those times. The 9.2 kya event does show up in the isotope profile and Candona ohioensis appears at Twin Ponds around this time but it is unclear if the two events are related.

Benthic Ostracodes

8.2 9.2

-9 -8 -7 -6 -5 -4 -3 -2 18 δ O VSMOW Figure 27: Ostracode abundance profile compared with benthic ostracode δ18O profile. The blue box highlights the Younger Dryas cooling event. The red and green lines highlight the 9.2 and 8.2 kya events, respectively.

Benthic Ostracode δ18O vs. Bulk Carbonate δ18O

Figure 28 correlates the benthic ostracode isotope profile with the bulk carbonate profile constructed by Dr. Bryan Shuman. The two profiles from Twin Ponds were matched up with the GRIP data (Johnson et al., 1997; Dansgaard et al., 1993;

Anklin et al., 1993; Grootes et al., 1993; Dansgaard et al., 1989). The benthic ostracode isotope values are reported here as VPDB in order to better correlate with the VPDB in the bulk carbonate record. The Younger Dryas is marked by the green dashed arrow and is noticeable across all three plots. The start of the Younger Dryas is well correlated between the bulk carbonate and the benthic ostracode record. The onset of the

Younger Dryas also matches up well with the GRIP model, in which the Younger Dryas in

Greenland occurs slightly before the Younger Dryas at Twin Ponds. The termination of the Younger Dryas is visible on the bulk carbonate plot but not the benthic ostracode plot. There were no samples that fit the requirements for isotope analysis around the end of the Younger Dryas in the ostracode record. The end of the Younger Dryas in the bulk carbonate record correlates with the GRIP model. Also visible in all three records is the 9.2 kya event which is shown by the red dashed arrow. The 8.2 kya event is noticeable in the bulk carbonate and GRIP models but not in the benthic ostracode record because of lack of data.

GRIP Bulk Carbonate Benthic Ostracodes δ18O VSMOW δ18O VPDB δ18O VPDB -44 -39 -34 -12 -11 -10 -9 -11 -9 -7 -5 -3 8000

8500

9000

9500

10000

10500 Cal. Yrs. Cal. 11000

11500

12000

12500

13000

Figure 28: Correlation of benthic ostracode δ18O with bulk carbonate δ18O and GRIP δ18O. Green lines signify the Younger Dryas, red lines signify the 9.2 kya event and the yellow line signifies the 8.2 kya event.

Post-Younger Dryas Interval

Figure 29 combines Figure 28 with the bulk carbonate δ18O from Kirby et al.,

(2002). The timing of the Post-Younger Dryas from the Kirby et al., study of Fayetteville

Green Lake in New York was from 11.5-10.3 cal. yrs. B.P. This was a time of higher than expected isotope values. The GRIP profile shows the Post-Younger Dryas as a time of low but overall rising isotope values which compared with the Twin Ponds and Kirby et al., profiles makes the Post-Younger Dryas interval more noticeable. The higher isotope values are noticeable in both the benthic ostracode and bulk carbonate profiles. Other records from the northeastern United States show differences in when this event ended. Kirby et al., (2002) show this event ending at 10.3 cal yrs. B.P. The event at Twin

Ponds appears to end around a similar time however, the termination is not as clear as in the Kirby et al., study.

GRIP Bulk Carbonate Benthic *From Kirby 18 δ O VSMOW δ18O VPDB δ18O VPDB et al., 2002

-44 -39 -34 -12 -11 -10 -9 -11 -9 -7 -5 -3 8000

9000

10000

11000

12000

13000

Figure 29: Correlating the information from Figure 28 with the Post-Younger Dryas interval (From Kirby et al., 2002, Figure 3, p. 325, shown with permission from Climate Dynamics).

Discussion

Multiple proxies were used to reconstruct the paleoclimate record of Twin Ponds,

Vermont during the late Pleistocene and early Holocene. Evidence of the Younger Dryas cooling event is noticeable in the loss on ignition data, which show a decrease in carbonate and an increase in clays. This increase in clays relative to marl indicates a drop in Chara production and increased forest openings leading to an increase in detrital material deposited in the lake. High resolution photographic images of the core also show more clay relative to Chara in the Younger Dryas age core material. The bulk carbonate δ18O analysis of the core also seems to pick up the Younger Dryas signal, which is evident by the low isotope values during that time. The bulk carbonate δ18O analysis also picks up other cooling events such as the 9.2 and 8.2 kya events, which are also shown by lower isotope values. The Post-Younger Dryas interval is also noticeable in the bulk carbonate data with slightly increased isotope values until about 10.3 cal. yrs. B.P.

The ostracode δ18O analysis focused mainly on the early Holocene-late

Pleistocene time frame. Lack of data and low time resolution in the middle to late

Holocene prevented further analysis. The ostracode analysis focused on the response of the benthic ostracode species whose longer life spans provide more of a year round response. The nektic species do not typically survive past the summer. The isotope data from the shells reflect these seasonal differences with the benthic ostracode data showing various climate change events while the nektic data does not pick up these signals. The benthic ostracode δ18O record shows a clear Younger Dryas signal marked by very low isotope values which correlate in time with the low values seen in the bulk carbonate δ18O record. Both of the Twin Ponds δ18O records correlate with the GRIP

δ18O record during the Younger Dryas, with a delay at the onset Younger Dryas. There is often a delay associated with the appearance of the Younger Dryas in Greenland and

North Atlantic locations. There can be various reasons for the delay which may be related to the time it takes for the glacial meltwater to travel south and/or it may also be related to the time it takes for the biota to adjust to the changing climate conditions

(Rach et al., 2004). The 9.2 kya event also appears in the ostracode δ18O record as a spike in low δ18O values. The 8.2 kya event does not appear in the ostracode δ18O record because of a lack of data resulting from low sedimentation rates. The Post-

Younger Dryas interval is more evident in the ostracode record than in the bulk carbonate record because the ostracodes appear to respond more than the bulk carbonate. The ostracode δ18O record shows the Post-Younger Dryas interval as a time of high δ18O values, which correlate well with the δ18O during the Post-Younger Drays

99 interval from Kirby et al., 2002 (Figure 29). This interval may be a result of precipitation with high δ18O values being advected northwards along the east coast of North America from a trough in the jet stream (Figure 9).

The ostracode abundance profile can also provide insight into the behavior of the lake (Figure 16). The Younger Dryas is noticeable in the profile as indicated by the disappearance of Pseudocandona stagnalis and the appearances of Candona candida and Cyclocypris ampla. C. ampla seems to be correlated with the summer position of the Polar Front, and when the Polar Front moved south during the Younger Dryas, C. ampla moved with it. When the Polar Front moved back after north Younger Dryas, C. ampla stayed at Twin Ponds because of the cold groundwater discharge area in the lake.

The disappearance of P. stagnalis may be related to the increased bicarbonate concentrations seen in the LOI data following the Younger Dryas. This study was not compared to all Younger Dryas records, but was compared with other records from the region. One such study in Ontario conducted by Yu and Eicher (1998) saw the Younger

Dryas as a time of decreased carbonate content and increased erosion derived sediments. The cold, dry conditions of the Younger Dryas meant shorter summers and shorter growing seasons for Chara which meant less production. In addition to less

Chara production, there would have been a decrease in forest cover in the area surrounding the lake and an increase in shrub cover. The openings in the forest would have meant accelerated soil erosion and more windblown sediments being deposited in the lake. Cypridopsis vidua also seems to increase in abundance after the Younger

Dryas, which may indicate an environmental shift. Cyclocypris globosa also provides a

100 lot of information about the behavior of the lake because of its preference for tundra like conditions. Its presence predating the Younger Dryas may indicate that Twin Ponds was experiencing very cold and dry conditions as a result of its proximity to the

Laurentide Ice Sheet or as a result of the cold groundwater input into the lake. Its continued presence after the Younger Dryas is probably an indicator of the cold, groundwater input. Many of the ostracodes seen at Twin Ponds are associated with groundwater discharge zones. Darwinula stevensoni, Candona candida, Cyclocypris globosa and Cyclocypris ampla are all often seen in springs or groundwater discharge zones of lakes. Candona ohioensis also provides a lot of information about the condition of the lake. Its presence is often associated with permanent lake settings, so its absence in the most of the early Holocene-late Pleistocene may indicate that the condition of the lake was too variable for C. ohioensis.

The statistical analysis of the ostracode counts provided further insight into the condition of the lake. Interpretation of the cluster analysis led to determining the presence of 5 distinct zones. The cluster analysis added a new observation into the behavior of the lake by showing the presence of the nektic zone which may correlate to the end of the Post-Younger Dryas interval and increased water temperatures leading to increased productivity in the lake. These increased temperatures seem to persist throughout the remainder of the core based on the high abundances of Cypridopsis vidua and Cyclocypris ampla.

101

The PCA analysis of the ostracode abundance data shows the influence of the lake condition and ostracode abundance on the dataset (Figures 18, 21 & 22). Axis 1 which accounts for 29.06% of the variance is dominated by the groundwater discharge and permanent lake ostracode groupings. Axis 2 and 3 which account for 22.65% and

14.21% of the variance respectively are independent axes which show the range of ostracode species in a permanent lake setting from littoral (Axis 2) to benthic (Axis 3).

102

Conclusion

Multi-proxy studies such as this are very valuable to the scientific community because they allow each proxy to play off of the others so the authors can reach a more definitive conclusion. So far in this research the multi-proxy approach has allowed for better time resolution in the core, a detailed climate history from 2 δ18O records, an idea of the surrounding environment and understanding of the behavior of the lake.

With the pollen data still to be completed, we can expect that the understanding of the region during the Late Glacial – Early Holocene time period will only get better.

The main conclusions drawn from the ostracode data include 1) the detailed climate history of Twin Ponds during the Late Glacial – Early Holocene and 2) the behavior of the lake as seen in the statistical analysis of the ostracode abundance data.

The climate history of Twin Ponds reflects the sensitivity of the North Atlantic region to climate forcing, with well known events such as the Bølling-Allerød, Younger Dryas and the 9.2 kya event. Rather unexpectedly, a Post-Younger Dryas signal is also detected in this record. This interval has not been

103 the subject of much study and hopefully this research will lead to further analysis which may provide a better spatial and temporal resolution of this event. The cluster and PCA analysis have led to a better understanding of the behavior of this lake which was not previously known. These data show that there was a cold groundwater discharge area in the lake that predates the Younger Dryas. The presence of Candona ohioensis influenced the PCA analysis greatly by appearing alongside the littoral species

Cyclocypris ampla and Cypridopsis vidua. This indicated that the lake was becoming more stable because of the presence of nektic and benthic species and because C. ohioensis prefers permanent, open lake settings.

It is my hope that these results will be used by researchers in the future. The ostracode isotope profile presented here can provide more constraint on the timing of climate events in the New England area and possibly help explore new research hypotheses within the Post-Younger Dryas interval. This ostracode record is also the first New England Holocene ostracode record outside of Lake Champlain and shows the easternmost distribution of mid-continent species such as Candona ohioensis, Candona paraohioensis and Candona candida, as well as the southern extent of Cyclocypris globosa. When these data are uploaded into NANODe (North American Non-Marine

Ostracode Database Project), my research will be available to all wishing to study ostracodes and paleolimnology.

104

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Appendix A: Isotope Input Data

LabID # of # of # used valves Hrs vavles in (C-Number) Sample ID Species in in out analysis

TP3B-96.5cm sta- C-38580 5 stagnalis 5 24.25 5 5

TP3B-95.5cm sta- C-38581 5 stagnalis 5 24.25 5 5

TP2B-40.5cm C-38582 can-3 candida 3 23.88 3 3

TP3B-90.5cm sta- C-38583 5 stagnalis 5 24.17 4 4

TP3B-87.5cm sta- C-38584 4 stagnalis 4 24.22 4 4

TP3B-86.5cm sta- C-38585 5 stagnalis 5 24.45 2.5 2.5

TP3B-82.5cm C-38586 can-5 candida 5 24.53 5 3

TP3B-79.5cm sta- C-38587 5 stagnalis 5 24.68 4 4

TP3B-77.5cm C-38588 can-5 candida 4 24.78 4 4

TP3B-76.5cm C-38589 can-5 candida 4 25.1 4 3

TP3B-72.5cm sta- C-38590 5 stagnalis 4 25.13 3 3

TP3B-63.5cm sta- C-38591 4 stagnalis 4 23.87 3.5 3.5

128

LabID # of # of # used valves Hrs vavles in (C-Number) Sample ID Species in in out analysis

TP3B-38.5cm C-38592 amp-19 ampla 19 23.87 16 8

TP3B-37.5cm C-38593 amp-18 ampla 18 23.9 17 7

TP3B-33.5cm C-38594 can-4 candida 4 23.8 4 4

TP3B-24.5cm C-38595 can-5 candida 5 24.08 5 3

TP3B-23.5cm C-38596 can-5 candida 5 24.03 5 3

TP3B-20.5cm C-38597 can-4 candida 4 24.28 4 3

TP3B-17.5cm C-38598 can-5 candida 5 24.25 5 3

TP3B-15.5cm C-38599 can-4 candida 4 24.47 4 4

TP3B-14.5cm C-38600 can-5 candida 5 24.4 4 4

TP2B-96.5cm C-38601 can-4 candida 4 24 4 3

TP2B-92.5cm C-38602 can-4 candida 4 23.93 4 3

TP2B-86.5cm C-38603 can-5 candida 5 24.1 5 3

TP2B-80.5cm C-38604 can-5 candida 5 24.07 5 3

129

LabID # of # of # used valves Hrs vavles in (C-Number) Sample ID Species in in out analysis

TP2B-76.5cm C-38605 can-4 candida 5 24.28 5 3

TP2B-71.5cm C-38606 can-5 candida 4 24.18 4 3

TP2B-70.5cm C-38607 can-5 candida 5 24.1 5 3

TP2B-60.5cm C-38608 amp-25 ampla 25 23.96 25 7

TP2B-59.5cm C-38609 can-5 candida 5 24.2 5 3

TP2B-50.5cm C-38610 amp-21 ampla 21 24.05 20 7

TP2B-41.5cm C-38611 can-4 candida 4 23.53 4 3

TP2B-40.5cm C-38612 ohi-2 ohioensis 2 23.57 2 2

TP2B-39.5cm C-38613 can-4 candida 4 23.62 4 3

TP2B-36.5cm C-38614 ohi-4 ohioensis 4 23.55 4 2

TP2B-21.5cm C-38615 ohi-2 ohioensis 2 23.78 2 2

TP2B-19.5cm C-38616 ohi-3 ohioensis 3 23.77 3 2

TP2B-17.5cm C-38617 ohi-3 ohioensis 3 23.97 3 2

130

LabID # of # of # used valves Hrs vavles in (C-Number) Sample ID Species in in out analysis

TP2B-6.5cm ohi- C-38618 3 ohioensis 3 23.92 3 2

TP2B-77.5cm C-38619 ohi-2 ohioensis 2 24.12 2 2

TP3B-72.5cm C-38620 amp-15 ampla 15 24.08 14 7

TP3B-63.5cm C-38621 amp-18 ampla 18 24.2 16 7

TP3B-38.5cm C-38622 vid-24 vidua 24 24.13 21 8

TP3B-37.5cm C-38623 vid-21 vidua 21 24.35 21 8

TP3B-33.5cm C-38624 vid-24 vidua 24 24.27 21 9

TP3B-24.5cm C-38625 vid-18 vidua 18 24.9 14 8

TP3B-23.5cm C-38626 amp-13 ampla 13 24.82 13 7

TP3B-20.5cm C-38627 vid-19 vidua 19 24.95 16 9

TP3B-17.5cm C-38628 vid-20 vidua 20 24.87 18 8

TP3B-15.5cm C-38629 vid-20 vidua 20 25.15 17 8

TP3B-14.5cm C-38630 vid-25 vidua 25 24.07 23 8

131

LabID # of # of # used valves Hrs vavles in (C-Number) Sample ID Species in in out analysis

TP2B-96.5cm C-38631 vid-24 vidua 24 23.33 23 8

TP2B-92.5cm C-38632 vid-21 vidua 21 23.27 19 8

TP2B-86.5cm C-38633 vid-26 vidua 26 23.32 22 9

TP2B-80.5cm C-38634 amp-16 ampla 16 23.43 14 7

TP2B-76.5cm C-38635 vid-24 vidua 24 23.55 24 8

TP2B-71.5cm C-38636 amp-14 ampla 14 23.48 14 7

TP2B-70.5cm C-38637 amp-15 ampla 15 23.68 15 7

TP2B-60.5cm C-38638 vid-22 vidua 22 23.63 21 8

TP2B-59.5cm C-38639 amp-15 ampla 15 23.95 14 7

TP2B-50.5cm C-38640 vid-21 vidua 21 23.87 17 8

TP2B-41.5cm C-38641 amp-19 ampla 19 24.03 17 7

TP2B-40.5cm C-38642 amp-19 ampla 19 23.97 16 7

TP2B-39.5cm C-38643 amp-15 ampla 15 24.17 14 7

132

LabID # of # of # used valves Hrs vavles in (C-Number) Sample ID Species in in out analysis

TP2B-36.5cm C-38644 amp-18 ampla 18 24.12 17 7

TP2B-21.5cm C-38645 amp-20 ampla 20 23.85 19 7

TP2B-19.5cm C-38646 amp-16 ampla 16 23.73 15 7

TP2B-17.5cm C-38647 amp-21 ampla 21 23.87 14 7

TP2B-6.5cm vid- C-38648 25 vidua 25 23.82 24 7

TP2B-77.5cm C-38649 vid-27 vidua 27 23.97 21 9

133

Appendix B: VPDB values

LabID Delta 13C Delta 18O (C- VPDB VPDB number) Sample ID (permil) (permil) Comments

C-38580 TP3B-96.5cm sta-5 -2.05 -9.39

C-38581 TP3B-95.5cm sta-5 -3.3 -9.96

C-38582 TP2B-40.5cm can-3 -7.82 -5.26

C-38583 TP3B-90.5cm sta-5 -3.81 -9.21

C-38584 TP3B-87.5cm sta-4 -3.79 -9.85

Poor analysis. Sample was C-38585 TP3B-86.5cm sta-5 -6.09 -9.67 small. (1.9V)

C-38586 TP3B-82.5cm can-5 -4.55 -7.74

C-38587 TP3B-79.5cm sta-5 -6.26 -9.17

C-38588 TP3B-77.5cm can-5 -5.7 -6.12

C-38589 TP3B-76.5cm can-5 -6.7 -6.12

C-38590 TP3B-72.5cm sta-5 -10.07 -10.14

C-38591 TP3B-63.5cm sta-4 -9.14 -9.6

C-38592 TP3B-38.5cm amp-19 -3.9 -7.92

C-38593 TP3B-37.5cm amp-18 -4.07 -8.74

C-38594 TP3B-33.5cm can-4 -8.07 -5.71

C-38595 TP3B-24.5cm can-5 -7.25 -3.67

C-38596 TP3B-23.5cm can-5 -7.31 -5.65

C-38597 TP3B-20.5cm can-4 -7.34 -5.02

C-38598 TP3B-17.5cm can-5 -6.76 -5.43

134

LabID Delta 13C Delta 18O (C- VPDB VPDB number) Sample ID (permil) (permil) Comments

C-38599 TP3B-15.5cm can-4 -7.34 -5

C-38600 TP3B-14.5cm can-5 -7.24 -5.14

C-38601 TP2B-96.5cm can-4 -6.25 -5.97

C-38602 TP2B-92.5cm can-4 -7.19 -5.79

C-38603 TP2B-86.5cm can-5 -7.43 -3.85

C-38604 TP2B-80.5cm can-5 -7.37 -5.46

C-38605 TP2B-76.5cm can-4 -8.02 -5.85

C-38606 TP2B-71.5cm can-5 -7.25 -6.25

C-38607 TP2B-70.5cm can-5 -7.61 -5.57

C-38608 TP2B-60.5cm amp-25 -2.77 -7.44

C-38609 TP2B-59.5cm can-5 -7.28 -5.68

C-38610 TP2B-50.5cm amp-21 -2.62 -8.84

C-38611 TP2B-41.5cm can-4 -6.26 -5.09

C-38612 TP2B-40.5cm ohi-2 -5.49 -7.79

C-38613 TP2B-39.5cm can-4 -8.22 -6.42

Poor analysis. Too much acid for reaction.

C-38614 TP2B-36.5cm ohi-4 -8.78 -8.22

Poor analysis. Too much acid for reaction.

C-38615 TP2B-21.5cm ohi-2 -2.87 -7.51

135

LabID Delta 13C Delta 18O (C- VPDB VPDB number) Sample ID (permil) (permil) Comments

C-38616 TP2B-19.5cm ohi-3 -4.68 -7.26

C-38617 TP2B-17.5cm ohi-3 -7.12 -7.39

C-38618 TP2B-6.5cm ohi-3 -5.31 -7.22

C-38619 TP2B-77.5cm ohi-2 -4.9 -7.01

C-38620 TP3B-72.5cm amp-15 -3.45 -9.28

C-38621 TP3B-63.5cm amp-18 -3.38 -8.87

C-38622 TP3B-38.5cm vid-24 -6.23 -8.79

C-38623 TP3B-37.5cm vid-21 -5.8 -8.95

C-38624 TP3B-33.5cm vid-24 -5.99 -9.28

C-38625 TP3B-24.5cm vid-18 -4.96 -9.13

C-38626 TP3B-23.5cm amp-13 -3.78 -7.59

C-38627 TP3B-20.5cm vid-19 -4.24 -9.4

C-38628 TP3B-17.5cm vid-20 -5.61 -9.48

C-38629 TP3B-15.5cm vid-20 -5.35 -8.97

C-38630 TP3B-14.5cm vid-25 -5.18 -9.11

C-38631 TP2B-96.5cm vid-24 -4.9 -9.54

C-38632 TP2B-92.5cm vid-21 -4.78 -9.12

C-38633 TP2B-86.5cm vid-26 -4.91 -9.39

C-38634 TP2B-80.5cm amp-16 -3.74 -7.24

C-38635 TP2B-76.5cm vid-24 -6.07 -9.7

136

LabID Delta 13C Delta 18O (C- VPDB VPDB number) Sample ID (permil) (permil) Comments

C-38636 TP2B-71.5cm amp-14 -3.89 -9.2

C-38637 TP2B-70.5cm amp-15 -3.75 -8.39

C-38638 TP2B-60.5cm vid-22 -4.51 -8.42

C-38639 TP2B-59.5cm amp-15 -2.9 -7.54

C-38640 TP2B-50.5cm vid-21 -4.91 -9.37

C-38641 TP2B-41.5cm amp-19 -2.8 -7.64

C-38642 TP2B-40.5cm amp-19 -2.43 -7.71

C-38643 TP2B-39.5cm amp-15 -2.71 -8.09

C-38644 TP2B-36.5cm amp-18 -3.76 -6.76

C-38645 TP2B-21.5cm amp-20 -3.88 -7.97

C-38646 TP2B-19.5cm amp-16 -3.8 -9.21

C-38647 TP2B-17.5cm amp-21 -3.8 -7.9

C-38648 TP2B-6.5cm vid-25 -5.37 -8.48

C-38649 TP2B-77.5cm vid-27 -5.39 -7.48

137

Appendix C: VSMOW Values for a Range of Temperatures Age (Cal. Yrs. Coldest δ 18O Min Ave Max Depth B.P.) Species VPDB Temp C Temp C Temp C δ18O VSMOW Values Benthic Ostracodes Min Max Ave 269.5 stagnalis -9.39 7.2 18.5 29.8 -10.22 -5.42 -7.69 268.5 stagnalis -9.96 7.2 18.5 29.8 -10.79 -5.99 -8.26 263.5 stagnalis -9.21 7.2 18.5 29.8 -10.04 -5.24 -7.51 260.5 stagnalis -9.85 7.2 18.5 29.8 -10.68 -5.88 -8.15 259.5 stagnalis -9.67 7.2 18.5 29.8 -10.50 -5.70 -7.97 255.5 12969 candida -7.74 5.5 16.75 28 -8.98 -4.11 -6.41 252.5 12768.65217 stagnalis -9.17 7.2 18.5 29.8 -10.00 -5.20 -7.47 250.5 12635.08696 candida -6.12 5.5 16.75 28 -7.36 -2.48 -4.78 249.5 12568.30435 candida -6.12 5.5 16.75 28 -7.36 -2.48 -4.78 245.5 12301.17391 ampla -10.14 6.5 18.25 30 -11.13 -6.14 -8.49 236.5 11700.13043 candida -9.6 5.5 16.75 28 -10.83 -5.98 -8.27 206.5 10995.57407 candida -5.71 5.5 16.75 28 -6.95 -2.07 -4.37 197.5 10844.15741 candida -3.67 5.5 16.75 28 -4.91 -0.02 -2.33 196.5 10827.33333 candida -5.65 5.5 16.75 28 -6.89 -2.01 -4.31 193.5 10776.86111 candida -5.02 5.5 16.75 28 -6.26 -1.38 -3.68 190.5 10726.38889 candida -5.43 5.5 16.75 28 -6.67 -1.79 -4.09 188.5 10692.74074 candida -5 5.5 16.75 28 -6.24 -1.36 -3.66 187.5 10675.91667 candida -5.14 5.5 16.75 28 -6.38 -1.50 -3.80 166.5 10322.61111 candida -5.97 5.5 16.75 28 -7.21 -2.33 -4.63 162.5 10255.31481 candida -5.79 5.5 16.75 28 -7.03 -2.15 -4.45 156.5 10154.37037 candida -3.85 5.5 16.75 28 -5.09 -0.21 -2.51 150.5 10053.42593 candida -5.46 5.5 16.75 28 -6.70 -1.82 -4.12

138

Age (Cal. Yrs. Coldest δ 18O Min Ave Max Depth B.P.) Species VPDB Temp C Temp C Temp C δ18O VSMOW Values Min Max Ave 146.5 9986.12963 candida -5.85 5.5 16.75 28 -7.09 -2.21 -4.51 140.5 9885.185185 candida -5.57 5.5 16.75 28 -6.81 -1.93 -4.23 129.5 9700.12037 candida -5.68 5.5 16.75 28 -6.92 -2.04 -4.34 111.5 9181.62069 candida -5.09 5.5 16.75 28 -6.33 -1.45 -3.75 110.5 9148.206897 candida -7.79 5.5 16.75 28 -9.03 -4.16 -6.46 110.5 9148.206897 candida -5.26 5.5 16.75 28 -6.50 -1.62 -3.92 109.5 9114.793103 ampla -6.42 6.5 18.25 30 -7.42 -2.40 -4.76 106.5 9014.551724 ampla -8.22 6.5 18.25 30 -9.22 -4.21 -6.57 91.5 8304.333333 ampla -7.51 6.5 18.25 30 -8.51 -3.50 -5.86 89.5 8133 ampla -7.26 6.5 18.25 30 -8.26 -3.24 -5.60 87.5 7961.666667 ampla -7.39 6.5 18.25 30 -8.39 -3.38 -5.74 76.5 5004 ampla -7.22 6.5 18.25 30 -8.22 -3.20 -5.56 51.5 723.2857143 candida -7.01 6.5 17.25 28 -8.25 -3.38 -5.68 Nektic Ostracodes 245.5 12301.17391 ampla -9.28 6.5 18.25 30 -10.27 -5.27 -7.63 236.5 11700.13043 candida -8.87 5.5 16.75 28 -10.11 -5.24 -7.54 211.5 11079.69444 ampla -7.92 6.5 18.25 30 -8.92 -3.91 -6.27 211.5 11079.69444 ampla -8.79 6.5 18.25 30 -9.79 -4.78 -7.14 210.5 11062.87037 ampla -8.74 6.5 18.25 30 -9.74 -4.73 -7.09 210.5 11062.87037 ampla -8.95 6.5 18.25 30 -9.95 -4.94 -7.30 206.5 10995.57407 candida -9.28 5.5 16.75 28 -10.52 -5.66 -7.95 197.5 10844.15741 candida -9.13 5.5 16.75 28 -10.37 -5.50 -7.80 196.5 10827.33333 candida -7.59 5.5 16.75 28 -8.83 -3.96 -6.26

139

Age (Cal. Yrs. Coldest δ 18O Min Ave Max Depth B.P.) Species VPDB Temp C Temp C Temp C δ18O VSMOW Values Min Max Ave 193.5 10776.86111 candida -9.4 5.5 16.75 28 -10.63 -5.78 -8.07 188.5 10692.74074 candida -8.97 5.5 16.75 28 -10.21 -5.78 -8.07 187.5 10675.91667 candida -9.11 5.5 16.75 28 -10.35 -5.34 -7.64 166.5 10322.61111 candida -9.54 5.5 16.75 28 -10.77 -5.48 -7.78 162.5 10255.31481 candida -9.12 5.5 16.75 28 -10.36 -5.92 -8.21 156.5 10154.37037 candida -9.39 5.5 16.75 28 -10.62 -5.49 -7.79 150.5 10053.42593 candida -7.24 5.5 16.75 28 -8.48 -5.77 -8.06 146.5 9986.12963 candida -9.7 5.5 16.75 28 -10.93 -3.61 -5.91 141.5 9902.009259 candida -9.2 5.5 16.75 28 -10.44 -6.08 -8.37 140.5 9885.185185 candida -8.39 5.5 16.75 28 -9.63 -5.57 -7.87 130.5 9716.944444 ampla -7.44 6.5 18.25 30 -8.44 -4.76 -7.06 130.5 9716.944444 ampla -8.42 6.5 18.25 30 -9.42 -3.43 -5.79 129.5 9700.12037 candida -7.54 5.5 16.75 28 -8.78 -4.41 -6.77 120.5 9482.344828 candida -8.84 5.5 16.75 28 -10.08 -3.91 -6.21 120.5 9482.344828 candida -9.37 5.5 16.75 28 -10.60 -5.21 -7.51 111.5 9181.62069 candida -7.64 5.5 16.75 28 -8.88 -5.75 -8.04 110.5 9148.206897 candida -7.71 5.5 16.75 28 -8.95 -4.01 -6.31 109.5 9114.793103 ampla -8.09 6.5 18.25 30 -9.09 -4.08 -6.38 106.5 9014.551724 ampla -6.76 6.5 18.25 30 -7.76 -4.08 -6.44 91.5 8304.333333 ampla -7.97 6.5 18.25 30 -8.97 -2.74 -5.10 89.5 8133 ampla -9.21 6.5 18.25 30 -10.20 -3.96 -6.32 87.5 7961.666667 ampla -7.9 6.5 18.25 30 -8.90 -5.20 -7.56 76.5 5004 ampla -8.48 6.5 18.25 30 -9.48 -3.89 -6.25 51.5 723.2857143 candida -7.48 5.5 16.75 28 -8.72 -4.47 -6.83

140

Appendix D: Ostracode Counts

Age

Other

Depth (cm) Depth

Candona (juev)Candona

TotalOstracodes

Candonacandida

Candonastagnalis

Cyclocypris ampla Cyclocypris

Cyclocypris globosa Cyclocypris

Darwinula stevensoni Darwinula

Totalvidua Cypridopsis

Totalohioensis Candona Totalparaohioensis Candona 0.5 0 9 0 3 1 13 -55 1.5 0 14 0 2 2 18 -41 2.5 0 2 0 1 3 -26 3.5 0 5 1 1 7 -12 4.5 0 4 0 3 7 2 5.5 0 1 0 2 3 17 6.5 0 1 0 1 31 7.5 0 0 0 1 1 45 8.5 0 3 0 3 59 9.5 0 5 0 1 6 74 10.5 0 1 0 1 88 11.5 0 3 0 2 1 6 102 12.5 0 5 0 1 1 7 117 13.5 0 3 0 3 131 14.5 0 9 0 1 4 14 145 15.5 1 8 1 7 3 20 159 16.5 0 5 2 11 4 22 174 17.5 0 12 1 10 2 12 37 188 18.5 1 20 2 10 3 14 50 202 19.5 0 12 0 5 1 6 24 217 20.5 4 26 5 30 4 16 85 231 21.5 2 64 9 46 11 30 1 163 245 22.5 2 36 7 55 13 31 144 259 23.5 0 22 3 27 4 19 1 76 274 24.5 2 33 8 49 10 34 136 288 25.5 2 12 2 17 20 53 302

141

Age

Other

Depth (cm) Depth

Cypridopsis vidua Cypridopsis

Candona (juev)Candona

TotalOstracodes

Candonacandida

Candonastagnalis

Cyclocypris ampla Cyclocypris

Cyclocypris globosa Cyclocypris

Darwinula stevensoni Darwinula

Total

Totalohioensis Candona Totalparaohioensis Candona 26.5 10 16 1 33 4 37 101 316 27.5 0 9 3 17 10 39 331 28.5 2 10 5 18 15 50 345 29.5 0 1 0 6 2 9 359 30.5 0 1 2 3 1 7 374 31.5 0 0 1 3 1 5 388 32.5 0 0 0 7 1 8 402 33.5 0 0 0 2 1 3 416 34.5 0 0 0 0 431 35.5 0 0 0 1 1 445 36.5 0 0 0 1 1 459 37.5 0 0 0 1 1 2 474 38.5 0 0 0 1 1 488 39.5 0 0 0 1 1 502 40.5 0 0 0 0 516 41.5 0 0 2 1 3 531 42.5 0 0 2 3 1 6 545 43.5 0 1 2 4 2 9 559 44.5 0 0 4 2 3 9 574 45.5 0 0 0 4 4 588 46.5 3 7 4 4 18 602 47.5 4 8 11 12 5 1 41 616 48.5 7 9 11 12 5 44 631 49.5 5 29 2 14 1 1 52 645 50.5 2 45 0 11 3 5 4 70 684 51.5 5 50 0 9 16 25 4 109 723 52.5 2 62 3 28 2 11 108 762 53.5 4 32 0 1 37 802

142

Age

Other

Depth (cm) Depth

Candona (juev)Candona

TotalOstracodes

Candonacandida

Candonastagnalis

Cyclocypris ampla Cyclocypris

Cyclocypris globosa Cyclocypris

Darwinula stevensoni Darwinula

Totalvidua Cypridopsis

Totalohioensis Candona Totalparaohioensis Candona 54.5 4 41 0 25 1 6 77 841 55.5 0 17 1 9 1 1 29 880 56.5 0 43 0 26 1 3 73 919 57.5 0 53 0 13 2 5 73 958 58.5 2 17 1 3 1 7 31 997 59.5 3 16 1 1 5 2 28 1036 60.5 3 17 2 8 5 4 1 40 1076 61.5 2 29 0 13 4 13 61 1115 62.5 6 15 0 6 13 12 52 1154 63.5 4 29 1 4 11 18 1 68 1193 64.5 3 18 1 4 5 10 41 1232 65.5 11 17 3 3 5 14 53 1271 66.5 14 23 2 2 13 17 71 1310 67.5 2 30 1 8 8 49 1350 68.5 1 15 2 2 6 26 1389 69.5 9 15 2 3 13 42 1428 70.5 12 31 4 2 8 22 79 1467 71.5 4 18 2 5 16 45 2057 72.5 0 3 0 3 2 8 2646 73.5 6 26 2 10 3 7 54 3236 74.5 7 12 1 3 3 3 29 3825 75.5 7 49 2 18 4 23 103 4415 76.5 5 45 4 5 17 76 5004 77.5 1 64 0 3 1 8 77 5594 78.5 0 68 0 5 11 9 93 6183 79.5 3 31 2 7 10 53 6773 80.5 0 59 0 40 5 104 7362 81.5 4 108 2 30 4 10 1 159 7448

143

Age

Ostracodes

Other

Depth (cm) Depth

Candona (juev)Candona

Total

Candonacandida

Candonastagnalis

Cyclocypris ampla Cyclocypris

Cyclocypris globosa Cyclocypris

Darwinula stevensoni Darwinula

Totalvidua Cypridopsis

Totalohioensis Candona Totalparaohioensis Candona 82.5 14 92 0 8 9 25 3 151 7533 83.5 7 14 0 3 1 11 2 38 7619 84.5 9 4 1 5 21 1 41 7705 85.5 1 18 0 15 2 17 1 54 7790 86.5 9 28 5 21 13 76 7876 87.5 5 26 0 40 11 82 7962 88.5 0 18 0 68 2 88 8047 89.5 3 21 0 43 2 69 8133 90.5 0 46 1 24 1 72 8219 91.5 9 17 0 48 5 79 8304 92.5 5 35 0 21 3 8 72 8390 93.5 14 49 4 36 4 22 3 132 8476 94.5 13 28 1 28 29 99 8561 95.5 14 41 3 36 23 1 118 8647 96.5 4 33 5 41 16 99 8680 97.5 8 23 1 20 2 18 2 74 8714 98.5 12 31 1 28 2 27 101 8747 99.5 2 23 0 29 10 64 8781 100.5 3 33 4 40 2 18 100 8814 101.5 7 21 0 15 9 52 8847 102.5 6 23 3 17 13 62 8881 103.5 6 29 0 18 14 1 68 8914 104.5 4 51 0 47 4 12 1 119 8948 105.5 7 29 1 17 4 15 73 8981 106.5 12 16 0 42 18 88 9015 107.5 1 47 14 44 12 30 1 149 9048 108.5 2 17 7 11 7 1 2 47 9081 109.5 0 13 2 22 6 18 4 65 9115

144

Age

Ostracodes

Other

Depth (cm) Depth

Candona (juev)Candona

Total

Candonacandida

Candonastagnalis

Cyclocypris ampla Cyclocypris

Cyclocypris globosa Cyclocypris

Darwinula stevensoni Darwinula

Totalvidua Cypridopsis

Totalohioensis Candona Totalparaohioensis Candona 110.5 4 36 3 32 5 20 5 105 9148 111.5 1 62 6 39 13 24 4 149 9182 112.5 0 20 9 18 6 22 2 77 9215 113.5 0 22 5 27 8 25 3 90 9248 114.5 0 7 6 30 7 25 75 9282 115.5 0 19 6 17 17 29 88 9315 116.5 0 19 3 12 15 21 1 71 9349 117.5 0 27 9 45 6 26 1 114 9382 118.5 0 16 3 27 5 26 1 78 9416 119.5 0 4 9 4 13 22 52 9449 120.5 0 37 17 95 11 40 1 201 9482 121.5 0 4 9 10 2 10 35 9516 122.5 0 35 0 61 4 6 4 110 9549 123.5 0 22 7 52 1 82 9583 124.5 0 38 7 79 5 2 131 9616 125.5 0 43 9 72 5 18 3 150 9633 126.5 0 57 2 33 92 9650 127.5 0 25 11 26 2 20 84 9666 128.5 0 16 3 5 5 29 9683 129.5 0 60 5 54 11 11 5 146 9700 130.5 0 151 2 140 2 295 9717 131.5 0 71 2 83 4 160 9734 132.5 0 65 0 12 77 9751 133.5 0 53 3 35 1 1 93 9767 134.5 0 32 2 13 16 23 4 90 9784 135.5 0 41 1 20 2 14 78 9801 136.5 0 46 9 61 1 11 1 129 9818 137.5 0 52 2 49 2 9 2 116 9835

145

globosa

Age

Other

Depth (cm) Depth

Candona (juev)Candona

TotalOstracodes

Candonacandida

Candonastagnalis

Cyclocypris ampla Cyclocypris

Cyclocypris Cyclocypris

Darwinula stevensoni Darwinula

Totalvidua Cypridopsis

Totalohioensis Candona Totalparaohioensis Candona 138.5 0 27 6 29 3 8 2 75 9852 139.5 0 43 6 16 20 11 96 9868 140.5 0 17 12 25 11 38 6 109 9885 141.5 0 81 7 19 1 34 6 148 9902 142.5 0 87 0 27 13 2 129 9919 143.5 0 93 0 49 4 25 171 9936 144.5 0 47 1 17 2 14 1 82 9952 145.5 0 85 1 60 3 3 152 9969 146.5 0 46 3 9 2 11 6 77 9986 147.5 0 50 8 11 2 56 1 128 10003 148.5 0 23 10 28 46 1 108 10020 149.5 0 31 4 8 12 53 2 110 10037 150.5 0 30 11 23 28 67 7 166 10053 151.5 0 15 2 14 20 67 6 124 10070 152.5 0 39 11 23 32 53 5 163 10087 153.5 0 37 20 14 14 68 4 157 10104 154.5 0 62 1 24 22 31 1 141 10121 155.5 0 10 4 3 9 71 3 100 10138 156.5 0 39 22 16 9 80 9 175 10154 157.5 0 60 6 19 12 36 2 135 10171 158.5 0 44 1 36 8 89 10188 159.5 0 38 6 6 3 39 1 93 10205 160.5 0 30 4 6 2 30 4 76 10222 161.5 0 15 9 10 17 56 1 108 10238 162.5 0 44 5 17 24 115 5 210 10255 163.5 0 38 2 32 5 22 99 10272 164.5 0 2 19 1 11 99 8 140 10289 165.5 0 22 0 10 16 48 10306

146

Age

Other

Depth (cm) Depth

Candona (juev)Candona

TotalOstracodes

Candonacandida

Candonastagnalis

Cyclocypris ampla Cyclocypris

Cyclocypris globosa Cyclocypris

Darwinula stevensoni Darwinula

Totalvidua Cypridopsis

Totalohioensis Candona Totalparaohioensis Candona 166.5 0 40 0 18 6 64 10323 167.5 0 26 10 12 8 27 2 85 10339 168.5 0 8 4 5 28 56 3 104 10356 169.5 0 17 3 2 10 32 10373 170.5 0 44 11 12 76 2 145 10390 171.5 0 26 8 8 1 12 55 10407 172.5 0 18 24 1 18 68 3 132 10424 173.5 0 33 17 5 8 45 1 109 10440 174.5 0 24 10 6 38 78 10457 175.5 0 14 7 6 15 55 4 101 10474 176.5 0 18 3 3 1 64 3 92 10491 177.5 0 49 5 4 3 17 1 79 10508 178.5 0 28 13 2 12 33 2 90 10525 179.5 0 12 7 8 38 4 69 10541 180.5 0 14 5 34 3 1 57 10558 181.5 0 47 0 4 31 82 10575 182.5 0 28 2 2 2 34 10592 183.5 0 52 0 1 3 56 10609 184.5 0 95 0 1 96 10625 185.5 0 31 4 1 24 2 62 10642 186.5 0 16 7 4 75 6 108 10659 187.5 0 36 10 1 25 6 78 10676 188.5 0 26 23 10 66 6 131 10693 189.5 0 18 25 2 43 3 91 10710 190.5 0 38 18 22 7 85 10726 191.5 0 84 0 4 88 10743 192.5 0 28 6 2 22 58 10760 193.5 0 26 12 4 49 4 95 10777

147

Age

Other

Depth (cm) Depth

Candona (juev)Candona

TotalOstracodes

Candonacandida

Candonastagnalis

Cyclocypris ampla Cyclocypris

Cyclocypris globosa Cyclocypris

Darwinula stevensoni Darwinula

Totalvidua Cypridopsis

Totalohioensis Candona Totalparaohioensis Candona 194.5 0 19 10 19 23 1 3 75 10794 195.5 0 5 18 2 72 80 2 179 10811 196.5 0 15 24 18 64 68 5 194 10827 197.5 0 24 35 23 21 74 5 1 183 10844 198.5 0 20 17 13 3 98 6 157 10861 199.5 0 10 10 11 8 47 6 92 10878 200.5 0 21 17 11 22 63 8 142 10895 201.5 0 16 43 10 26 65 3 163 10911 202.5 0 7 12 18 21 72 2 132 10928 203.5 0 20 46 7 8 83 6 170 10945 204.5 0 29 4 3 12 2 50 10962 205.5 0 60 15 2 30 1 108 10979 206.5 0 36 11 59 5 111 10996 207.5 0 25 9 4 26 3 1 68 11012 208.5 0 31 23 2 31 1 88 11029 209.5 0 74 11 7 14 2 2 110 11046 210.5 0 73 0 24 97 11063 211.5 0 68 0 20 88 11080 212.5 0 40 2 7 49 11097 213.5 0 104 0 2 2 108 11113 214.5 0 85 3 7 95 11130 215.5 0 41 0 2 43 11147 216.5 0 54 3 23 80 11164 217.5 0 75 0 1 76 11181 218.5 0 24 1 6 31 11197 219.5 0 27 4 2 21 54 11214 220.5 0 39 0 3 1 43 11231 221.5 0 73 2 4 2 81 11248

148

Age

Other

Depth (cm) Depth

Cypridopsis vidua Cypridopsis

Candona (juev)Candona

TotalOstracodes

Candonacandida

Candonastagnalis

Cyclocypris ampla Cyclocypris

Cyclocypris globosa Cyclocypris

Darwinula stevensoni Darwinula

Total

Totalohioensis Candona Totalparaohioensis Candona 222.5 0 49 0 1 50 11265 223.5 0 16 0 16 11282 224.5 0 38 0 2 1 2 43 11298 225.5 0 5 8 2 16 31 11315 226.5 0 17 3 12 5 37 11332 227.5 0 29 8 3 8 2 50 11349 228.5 0 29 0 5 34 11366 229.5 0 0 0 0 11383 230.5 0 22 2 12 2 38 11399 231.5 0 13 0 7 6 1 1 28 11416 232.5 0 26 3 3 9 2 43 11433 233.5 0 26 0 10 16 3 55 11500 234.5 0 21 2 3 2 28 11567 235.5 0 4 4 9 12 29 11633 236.5 0 7 10 23 6 4 1 51 11700 237.5 0 0 0 6 2 8 11767 238.5 0 0 1 3 16 1 21 11834 239.5 0 0 0 13 13 2 28 11900 240.5 0 2 0 9 14 8 33 11967 241.5 0 1 0 17 12 7 37 12034 242.5 0 4 0 8 19 4 35 12101 243.5 0 0 0 11 3 5 19 12168 244.5 0 0 0 13 6 6 25 12234 245.5 0 0 0 19 13 5 37 12301 246.5 0 0 0 22 1 2 25 12368 247.5 0 1 0 2 2 3 2 10 12435 248.5 0 0 0 1 44 6 1 52 12502 249.5 0 3 0 1 84 8 96 12568

149

vidua

Age

Other

Depth (cm) Depth

Candona (juev)Candona

TotalOstracodes

Candonacandida

Candonastagnalis

Cyclocypris ampla Cyclocypris

Cyclocypris globosa Cyclocypris

Darwinula stevensoni Darwinula

Total Cypridopsis

Totalohioensis Candona Totalparaohioensis Candona 250.5 0 1 3 29 1 7 41 12635 251.5 0 9 5 42 4 60 12702 252.5 0 7 0 18 6 31 12769 253.5 0 28 0 13 41 12835 254.5 0 10 0 10 4 4 28 12902 255.5 0 5 6 25 2 6 44 12969 256.5 0 0 4 22 5 1 32 257.5 0 0 1 32 5 1 39 258.5 0 0 0 27 4 31 259.5 0 2 3 17 13 35 260.5 0 2 3 28 6 39 261.5 0 0 2 28 4 34 262.5 0 0 1 10 9 20 263.5 0 0 0 22 26 48 264.5 0 0 0 8 2 10 265.5 0 0 0 2 6 8 266.5 0 0 0 3 4 7 267.5 0 0 0 2 1 3 268.5 0 0 0 10 9 19 269.5 0 0 0 14 8 22 270.5 0 0 0 12 2 1 15 271.5 0 0 0 0 0 0 0

150

minus bag minus

Age

Valves per Gram per Valves

Depth (cm) Depth

weight

vidua Valves per Gram viduaper Valves

ampla Valves per Gram per amplaValves

globosa Valves per Gram globosaper Valves

candida Valves per Gram candidaper Valves

stagnalis Valves per Gram per stagnalisValves

ohioensis Valves per Gram ohioensisper Valves

stevensoni

paraohioensis Valves per Gram paraohioensisper Valves Candona (juev) Valves per Gram per (juev)Candona Valves -55 0.50 7.34 1.23 0.41 0.00 0.00 0.14 0.00 0.00 0.00 0.00 -41 1.50 4.34 3.23 0.46 0.00 0.00 0.46 0.00 0.00 0.00 0.00 -26 2.50 1.12 1.79 0.89 0.00 0.00 0.00 0.00 0.00 0.00 0.00 -12 3.50 1.88 2.66 0.00 0.00 0.00 0.53 0.00 0.00 0.00 0.53 2 4.50 2.12 1.89 1.42 0.00 0.00 0.00 0.00 0.00 0.00 0.00 17 5.50 3.11 0.32 0.64 0.00 0.00 0.00 0.00 0.00 0.00 0.00 31 6.50 3.80 0.26 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 45 7.50 1.63 0.00 0.00 0.00 0.00 0.61 0.00 0.00 0.00 0.00 59 8.50 3.50 0.86 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 74 9.50 3.68 1.36 0.00 0.00 0.00 0.27 0.00 0.00 0.00 0.00 88 10.50 1.24 0.81 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 102 11.50 3.35 0.90 0.60 0.00 0.30 0.00 0.00 0.00 0.00 0.00 117 12.50 3.45 1.45 0.29 0.00 0.00 0.29 0.00 0.00 0.00 0.00 131 13.50 2.89 1.04 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 145 14.50 2.28 3.95 0.44 0.00 0.00 1.75 0.00 0.00 0.00 0.00 159 15.50 2.40 3.33 2.92 0.42 0.00 1.25 0.00 0.00 0.00 0.42 174 16.50 4.17 1.20 2.64 0.00 0.00 0.96 0.00 0.00 0.00 0.48 188 17.50 1.77 6.78 5.65 0.00 1.13 6.78 0.00 0.00 0.00 0.56 202 18.50 2.94 6.80 3.40 0.34 1.02 4.76 0.00 0.00 0.00 0.68 217 19.50 4.09 2.93 1.22 0.00 0.24 1.47 0.00 0.00 0.00 0.00 231 20.50 4.28 6.07 7.01 0.93 0.93 3.74 0.00 0.00 0.00 1.17 245 21.50 5.62 11.39 8.19 0.36 1.96 5.34 0.18 0.00 0.00 1.60 259 22.50 5.79 6.22 9.50 0.35 2.25 5.35 0.00 0.00 0.00 1.21 274 23.50 4.79 4.59 5.64 0.00 0.84 3.97 0.21 0.00 0.00 0.63 288 24.50 4.53 7.28 10.82 0.44 2.21 7.51 0.00 0.00 0.00 1.77 302 25.50 3.80 3.16 4.47 0.53 0.00 5.26 0.00 0.00 0.00 0.53 316 26.50 5.31 3.01 6.21 1.88 0.75 6.97 0.00 0.00 0.00 0.19

151

(cm)

Age

Valves per Gram per Valves

Depth

weightbag minus

vidua Valves per Gram viduaper Valves

ampla Valves per Gram per amplaValves

globosa Valves per Gram globosaper Valves

candida Valves per Gram candidaper Valves

stagnalis Valves per Gram per stagnalisValves

ohioensis Valves per Gram ohioensisper Valves

stevensoni

paraohioensis Valves per Gram paraohioensisper Valves Candona (juev) Valves per Gram per (juev)Candona Valves 331 27.50 2.43 3.70 7.00 0.00 0.00 4.12 0.00 0.00 0.00 1.23 345 28.50 4.19 2.39 4.30 0.48 0.00 3.58 0.00 0.00 0.00 1.19 359 29.50 5.60 0.18 1.07 0.00 0.00 0.36 0.00 0.00 0.00 0.00 374 30.50 5.88 0.17 0.51 0.00 0.00 0.17 0.00 0.00 0.00 0.34 388 31.50 5.79 0.00 0.52 0.00 0.00 0.17 0.00 0.00 0.00 0.17 402 32.50 4.41 0.00 1.59 0.00 0.00 0.23 0.00 0.00 0.00 0.00 416 33.50 2.41 0.00 0.83 0.00 0.00 0.41 0.00 0.00 0.00 0.00 431 34.50 3.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 445 35.50 1.39 0.00 0.72 0.00 0.00 0.00 0.00 0.00 0.00 0.00 459 36.50 2.24 0.00 0.00 0.00 0.00 0.45 0.00 0.00 0.00 0.00 474 37.50 2.20 0.00 0.45 0.00 0.00 0.45 0.00 0.00 0.00 0.00 488 38.50 2.00 0.00 0.00 0.00 0.00 0.50 0.00 0.00 0.00 0.00 502 39.50 1.60 0.00 0.00 0.00 0.00 0.63 0.00 0.00 0.00 0.00 516 40.50 1.41 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 531 41.50 3.36 0.00 0.30 0.00 0.00 0.00 0.00 0.00 0.00 0.60 545 42.50 1.22 0.00 2.46 0.00 0.00 0.82 0.00 0.00 0.00 1.64 559 43.50 1.15 0.87 3.48 0.00 0.00 1.74 0.00 0.00 0.00 1.74 574 44.50 1.25 0.00 1.60 0.00 0.00 2.40 0.00 0.00 0.00 3.20 588 45.50 1.62 0.00 0.00 0.00 0.00 2.47 0.00 0.00 0.00 0.00 602 46.50 4.20 1.67 0.95 0.71 0.00 0.00 0.00 0.00 0.00 0.95 616 47.50 5.35 1.50 2.24 0.75 0.00 0.93 0.00 0.19 0.00 2.06 631 48.50 7.07 1.27 1.70 0.99 0.00 0.71 0.00 0.00 0.00 1.56 645 49.50 4.36 6.65 3.21 1.15 0.23 0.23 0.00 0.00 0.00 0.46 684 50.50 5.47 8.23 2.01 0.37 0.55 0.91 0.00 0.73 0.00 0.00 723 51.50 5.91 8.46 1.52 0.85 2.71 4.23 0.00 0.68 0.00 0.00 762 52.50 6.06 10.23 4.62 0.33 0.33 1.82 0.00 0.00 0.00 0.50 802 53.50 4.04 7.92 0.00 0.99 0.00 0.25 0.00 0.00 0.00 0.00

152

(cm)

Age

Valves per Gram per Valves

Depth

weightbag minus

vidua Valves per Gram viduaper Valves

ampla Valves per Gram per amplaValves

globosa Valves per Gram globosaper Valves

candida Valves per Gram candidaper Valves

stagnalis Valves per Gram per stagnalisValves

ohioensis Valves per Gram ohioensisper Valves

stevensoni

paraohioensis Valves per Gram paraohioensisper Valves Candona (juev) Valves per Gram per (juev)Candona Valves 841 54.50 5.28 7.77 4.73 0.76 0.19 1.14 0.00 0.00 0.00 0.00 880 55.50 5.22 3.26 1.72 0.00 0.19 0.19 0.00 0.00 0.00 0.19 919 56.50 5.15 8.35 5.05 0.00 0.19 0.58 0.00 0.00 0.00 0.00 958 57.50 4.21 12.59 3.09 0.00 0.48 1.19 0.00 0.00 0.00 0.00 997 58.50 5.91 2.88 0.51 0.34 0.17 1.18 0.00 0.00 0.00 0.17 1036 59.50 7.18 2.23 0.14 0.42 0.70 0.28 0.00 0.00 0.00 0.14 1076 60.50 5.29 3.21 1.51 0.57 0.95 0.76 0.00 0.19 0.00 0.38 1115 61.50 6.87 4.22 1.89 0.29 0.58 1.89 0.00 0.00 0.00 0.00 1154 62.50 7.53 1.99 0.80 0.80 1.73 1.59 0.00 0.00 0.00 0.00 1193 63.50 5.24 5.53 0.76 0.76 2.10 3.44 0.00 0.19 0.00 0.19 1232 64.50 3.99 4.51 1.00 0.75 1.25 2.51 0.00 0.00 0.00 0.25 1271 65.50 6.57 2.59 0.46 1.67 0.76 2.13 0.00 0.00 0.00 0.46 1310 66.50 5.76 3.99 0.35 2.43 2.26 2.95 0.00 0.00 0.00 0.35 1350 67.50 6.83 4.39 0.00 0.29 1.17 1.17 0.00 0.00 0.00 0.15 1389 68.50 5.90 2.54 0.00 0.17 0.34 1.02 0.00 0.00 0.00 0.34 1428 69.50 6.34 2.37 0.00 1.42 0.47 2.05 0.00 0.00 0.00 0.32 1467 70.50 6.02 5.15 0.33 1.99 1.33 3.65 0.00 0.00 0.00 0.66 2057 71.50 4.39 4.10 0.00 0.91 1.14 3.64 0.00 0.00 0.00 0.46 2646 72.50 1.42 2.11 2.11 0.00 0.00 1.41 0.00 0.00 0.00 0.00 3236 73.50 8.20 3.17 1.22 0.73 0.37 0.85 0.00 0.00 0.00 0.24 3825 74.50 5.27 2.28 0.57 1.33 0.57 0.57 0.00 0.00 0.00 0.19 4415 75.50 7.35 6.67 2.45 0.95 0.54 3.13 0.00 0.00 0.00 0.27 5004 76.50 7.41 6.07 0.67 0.67 0.00 2.29 0.00 0.00 0.00 0.54 5594 77.50 6.68 9.58 0.45 0.15 0.15 1.20 0.00 0.00 0.00 0.00 6183 78.50 9.64 7.05 0.52 0.00 1.14 0.93 0.00 0.00 0.00 0.00 6773 79.50 8.94 3.47 0.78 0.34 0.00 1.12 0.00 0.00 0.00 0.22 7362 80.50 7.32 8.06 5.46 0.00 0.00 0.68 0.00 0.00 0.00 0.00

153

(cm)

Age

Valves per Gram per Valves

Depth

weightbag minus

vidua Valves per Gram viduaper Valves

ampla Valves per Gram per amplaValves

globosa Valves per Gram globosaper Valves

candida Valves per Gram candidaper Valves

stagnalis Valves per Gram per stagnalisValves

ohioensis Valves per Gram ohioensisper Valves

stevensoni

paraohioensis Valves per Gram paraohioensisper Valves Candona (juev) Valves per Gram per (juev)Candona Valves 7448 81.50 8.84 12.22 3.39 0.45 0.45 1.13 0.00 0.11 0.00 0.23 7533 82.50 6.57 14.00 1.22 2.13 1.37 3.81 0.00 0.46 0.00 0.00 7619 83.50 10.79 1.30 0.28 0.65 0.09 1.02 0.00 0.19 0.00 0.00 7705 84.50 6.49 0.62 0.77 1.39 0.00 3.24 0.00 0.15 0.00 0.15 7790 85.50 8.96 2.01 1.67 0.11 0.22 1.90 0.00 0.11 0.00 0.00 7876 86.50 8.19 3.42 2.56 1.10 0.00 1.59 0.00 0.00 0.00 0.61 7962 87.50 6.08 4.28 6.58 0.82 0.00 1.81 0.00 0.00 0.00 0.00 8047 88.50 7.57 2.38 8.98 0.00 0.00 0.26 0.00 0.00 0.00 0.00 8133 89.50 7.70 2.73 5.58 0.39 0.00 0.26 0.00 0.00 0.00 0.00 8219 90.50 5.40 8.52 4.44 0.00 0.00 0.19 0.00 0.00 0.00 0.19 8304 91.50 7.00 2.43 6.86 1.29 0.00 0.71 0.00 0.00 0.00 0.00 8390 92.50 6.93 5.05 3.03 0.72 0.43 1.15 0.00 0.00 0.00 0.00 8476 93.50 8.79 5.57 4.10 1.59 0.46 2.50 0.00 0.34 0.00 0.46 8561 94.50 9.13 3.07 3.07 1.42 0.00 3.18 0.00 0.00 0.00 0.11 8647 95.50 9.07 4.52 3.97 1.54 0.00 2.54 0.00 0.11 0.00 0.33 8680 96.50 9.01 3.66 4.55 0.44 0.00 1.78 0.00 0.00 0.00 0.55 8714 97.50 8.00 2.88 2.50 1.00 0.25 2.25 0.00 0.25 0.00 0.13 8747 98.50 12.15 2.55 2.30 0.99 0.16 2.22 0.00 0.00 0.00 0.08 8781 99.50 8.67 2.65 3.34 0.23 0.00 1.15 0.00 0.00 0.00 0.00 8814 100.50 8.14 4.05 4.91 0.37 0.25 2.21 0.00 0.00 0.00 0.49 8847 101.50 8.70 2.41 1.72 0.80 0.00 1.03 0.00 0.00 0.00 0.00 8881 102.50 8.05 2.86 2.11 0.75 0.00 1.61 0.00 0.00 0.00 0.37 8914 103.50 7.41 3.91 2.43 0.81 0.00 1.89 0.00 0.13 0.00 0.00 8948 104.50 7.45 6.85 6.31 0.54 0.54 1.61 0.00 0.13 0.00 0.00 8981 105.50 8.14 3.56 2.09 0.86 0.49 1.84 0.00 0.00 0.00 0.12 9015 106.50 7.12 2.25 5.90 1.69 0.00 2.53 0.00 0.00 0.00 0.00 9048 107.50 10.33 4.55 4.26 0.10 1.16 2.90 0.00 0.10 0.00 1.36

154

(cm)

Age

Valves per Gram per Valves

Depth

weightbag minus

vidua Valves per Gram viduaper Valves

ampla Valves per Gram per amplaValves

globosa Valves per Gram globosaper Valves

candida Valves per Gram candidaper Valves

stagnalis Valves per Gram per stagnalisValves

ohioensis Valves per Gram ohioensisper Valves

Stevensoni

paraohioensis Valves per Gram paraohioensisper Valves Candona (juev) Valves per Gram per (juev)Candona Valves 9081 108.50 7.11 2.39 1.55 0.28 0.98 0.14 0.00 0.28 0.00 0.98 9115 109.50 6.99 1.86 3.15 0.00 0.86 2.58 0.00 0.57 0.00 0.29 9148 110.50 8.63 4.17 3.71 0.46 0.58 2.32 0.00 0.58 0.00 0.35 9182 111.50 7.88 7.87 4.95 0.13 1.65 3.05 0.00 0.51 0.00 0.76 9215 112.50 5.91 3.38 3.05 0.00 1.02 3.72 0.00 0.34 0.00 1.52 9248 113.50 8.78 2.51 3.08 0.00 0.91 2.85 0.00 0.34 0.00 0.57 9282 114.50 7.44 0.94 4.03 0.00 0.94 3.36 0.00 0.00 0.00 0.81 9315 115.50 6.99 2.72 2.43 0.00 2.43 4.15 0.00 0.00 0.00 0.86 9349 116.50 7.48 2.54 1.60 0.00 2.01 2.81 0.00 0.13 0.00 0.40 9382 117.50 9.07 2.98 4.96 0.00 0.66 2.87 0.00 0.11 0.00 0.99 9416 118.50 6.71 2.38 4.02 0.00 0.75 3.87 0.00 0.15 0.00 0.45 9449 119.50 9.50 0.42 0.42 0.00 1.37 2.32 0.00 0.00 0.00 0.95 9482 120.50 5.17 7.16 18.38 0.00 2.13 7.74 0.00 0.19 0.00 3.29 9516 121.50 10.13 0.39 0.99 0.00 0.20 0.99 0.00 0.00 0.00 0.89 9549 122.50 5.27 6.64 11.57 0.00 0.76 1.14 0.00 0.76 0.00 0.00 9583 123.50 6.46 3.41 8.05 0.00 0.15 0.00 0.00 0.00 0.00 1.08 9616 124.50 8.70 4.37 9.08 0.00 0.57 0.23 0.00 0.00 0.00 0.80 9633 125.50 8.79 4.89 8.19 0.00 0.57 2.05 0.00 0.34 0.00 1.02 9650 126.50 7.14 7.98 4.62 0.00 0.00 0.00 0.00 0.00 0.00 0.28 9666 127.50 10.20 2.45 2.55 0.00 0.20 1.96 0.00 0.00 0.00 1.08 9683 128.50 2.46 6.50 2.03 0.00 0.00 2.03 0.00 0.00 0.00 1.22 9700 129.50 6.75 8.89 8.00 0.00 1.63 1.63 0.00 0.74 0.00 0.74 9717 130.50 8.20 18.41 17.07 0.00 0.24 0.00 0.00 0.00 0.00 0.24 9734 131.50 8.02 8.85 10.35 0.00 0.00 0.50 0.00 0.00 0.00 0.25 9751 132.50 7.22 9.00 1.66 0.00 0.00 0.00 0.00 0.00 0.00 0.00 9767 133.50 6.00 8.83 5.83 0.00 0.00 0.17 0.00 0.17 0.00 0.50 9784 134.50 9.36 3.42 1.39 0.00 1.71 2.46 0.00 0.43 0.00 0.21

155

(cm)

Age

Valves per Gram per Valves

Depth

weightbag minus

vidua Valves per Gram viduaper Valves

ampla Valves per Gram per amplaValves

globosa Valves per Gram globosaper Valves

candida Valves per Gram candidaper Valves

stagnalis Valves per Gram per stagnalisValves

ohioensis Valves per Gram ohioensisper Valves

Stevensoni

paraohioensis Valves per Gram paraohioensisper Valves Candona (juev) Valves per Gram per (juev)Candona Valves 9801 135.50 5.87 6.98 3.41 0.00 0.34 2.39 0.00 0.00 0.00 0.17 9818 136.50 10.87 4.23 5.61 0.00 0.09 1.01 0.00 0.09 0.00 0.83 9835 137.50 7.96 6.53 6.16 0.00 0.25 1.13 0.00 0.25 0.00 0.25 9852 138.50 6.92 3.90 4.19 0.00 0.43 1.16 0.00 0.29 0.00 0.87 9868 139.50 8.83 4.87 1.81 0.00 2.27 1.25 0.00 0.00 0.00 0.68 9885 140.50 9.32 1.82 2.68 0.00 1.18 4.08 0.00 0.64 0.00 1.29 9902 141.50 8.24 9.83 2.31 0.00 0.12 4.13 0.00 0.73 0.00 0.85 9919 142.50 8.64 10.07 3.13 0.00 0.00 1.50 0.00 0.23 0.00 0.00 9936 143.50 7.90 11.77 6.20 0.00 0.51 3.16 0.00 0.00 0.00 0.00 9952 144.50 6.51 7.22 2.61 0.00 0.31 2.15 0.00 0.15 0.00 0.15 9969 145.50 8.44 10.07 7.11 0.00 0.36 0.00 0.00 0.36 0.00 0.12 9986 146.50 9.01 5.11 1.00 0.00 0.22 1.22 0.00 0.67 0.00 0.33 10003 147.50 8.42 5.94 1.31 0.00 0.24 6.65 0.00 0.12 0.00 0.95 10020 148.50 10.71 2.15 0.00 0.00 2.61 4.30 0.00 0.09 0.00 0.93 10037 149.50 7.31 4.24 1.09 0.00 1.64 7.25 0.00 0.27 0.00 0.55 10053 150.50 10.48 2.86 2.19 0.00 2.67 6.39 0.00 0.67 0.00 1.05 10070 151.50 7.32 2.05 1.91 0.00 2.73 9.15 0.00 0.82 0.00 0.27 10087 152.50 6.63 5.88 3.47 0.00 4.83 7.99 0.00 0.75 0.00 1.66 10104 153.50 8.96 4.13 1.56 0.00 1.56 7.59 0.00 0.45 0.00 2.23 10121 154.50 7.78 7.97 3.08 0.00 2.83 3.98 0.00 0.13 0.00 0.13 10138 155.50 6.80 1.47 0.44 0.00 1.32 10.44 0.00 0.44 0.00 0.59 10154 156.50 10.74 3.63 1.49 0.00 0.84 7.45 0.00 0.84 0.00 2.05 10171 157.50 7.88 7.61 2.41 0.00 1.52 4.57 0.00 0.25 0.00 0.76 10188 158.50 6.37 6.91 5.65 0.00 0.00 1.26 0.00 0.00 0.00 0.16 10205 159.50 9.62 3.95 0.62 0.00 0.31 4.05 0.00 0.10 0.00 0.62 10222 160.50 3.94 7.61 1.52 0.00 0.51 7.61 0.00 1.02 0.00 1.02 10238 161.50 10.33 1.45 0.97 0.00 1.65 5.42 0.00 0.10 0.00 0.87

156

Age

Valves per Gram per Valves

Depth (cm) Depth

weightbag minus

vidua Valves per Gram viduaper Valves

ampla Valves per Gram per amplaValves

globosa Valves per Gram globosaper Valves

candida Valves per Gram candidaper Valves

stagnalis Valves per Gram per stagnalisValves

ohioensis Valves per Gram ohioensisper Valves

Stevensoni

paraohioensis Valves per Gram paraohioensisper Valves Candona (juev) Valves per Gram per (juev)Candona Valves 10255 162.50 7.58 5.80 2.24 0.00 3.17 15.17 0.00 0.66 0.00 0.66 10272 163.50 8.90 4.27 3.60 0.00 0.56 2.47 0.00 0.00 0.00 0.22 10289 164.50 11.04 0.18 0.09 0.00 1.00 8.97 0.00 0.72 0.00 1.72 10306 165.50 6.34 3.47 1.58 0.00 0.00 2.52 0.00 0.00 0.00 0.00 10323 166.50 10.15 3.94 0.00 0.00 0.00 1.77 0.00 0.59 0.00 0.00 10339 167.50 9.04 2.88 1.33 0.00 0.88 2.99 0.00 0.22 0.00 1.11 10356 168.50 6.92 1.16 0.72 0.00 4.05 8.09 0.00 0.43 0.00 0.58 10373 169.50 3.77 4.51 0.00 0.00 0.53 2.65 0.00 0.00 0.00 0.80 10390 170.50 10.23 4.30 1.17 0.00 0.00 7.43 0.00 0.20 0.00 1.08 10407 171.50 5.05 5.15 1.58 0.00 0.20 2.38 0.00 0.00 0.00 1.58 10424 172.50 9.04 1.99 0.11 0.00 1.99 7.52 0.00 0.33 0.00 2.65 10440 173.50 10.94 3.02 0.46 0.00 0.73 4.11 0.00 0.09 0.00 1.55 10457 174.50 7.24 3.31 0.00 0.00 0.83 5.25 0.00 0.00 0.00 1.38 10474 175.50 10.35 1.35 0.58 0.00 1.45 5.31 0.00 0.39 0.00 0.68 10491 176.50 7.32 2.46 0.41 0.00 0.14 8.74 0.00 0.41 0.00 0.41 10508 177.50 7.54 6.50 0.53 0.00 0.40 2.25 0.00 0.13 0.00 0.66 10525 178.50 9.23 3.03 0.22 0.00 1.30 3.58 0.00 0.22 0.00 1.41 10541 179.50 8.62 1.39 0.00 0.00 0.93 4.41 0.00 0.46 0.00 0.81 10558 180.50 7.27 1.93 0.00 0.00 0.00 4.68 0.00 0.41 0.14 0.69 10575 181.50 6.89 6.82 0.58 0.00 0.00 4.50 0.00 0.00 0.00 0.00 10592 182.50 10.73 2.61 0.00 0.00 0.00 0.19 0.00 0.19 0.00 0.19 10609 183.50 8.03 6.48 0.00 0.00 0.12 0.37 0.00 0.00 0.00 0.00 10625 184.50 8.64 11.00 0.00 0.00 0.00 0.12 0.00 0.00 0.00 0.00 10642 185.50 8.93 3.47 0.00 0.00 0.11 2.69 0.00 0.22 0.00 0.45 10659 186.50 11.65 1.37 0.00 0.00 0.34 6.44 0.00 0.52 0.00 0.60 10676 187.50 7.91 4.55 0.00 0.00 0.13 3.16 0.00 0.76 0.00 1.26 10693 188.50 8.21 3.17 0.00 0.00 1.22 8.04 0.00 0.73 0.00 2.80

157

Age

Valves per Gram per Valves

Depth (cm) Depth

weightbag minus

vidua Valves per Gram viduaper Valves

ampla Valves per Gram per amplaValves

globosa Valves per Gram globosaper Valves

candida Valves per Gram candidaper Valves

stagnalis Valves per Gram per stagnalisValves

ohioensis Valves per Gram ohioensisper Valves

Stevensoni

paraohioensis Valves per Gram paraohioensisper Valves Candona (juev) Valves per Gram per (juev)Candona Valves 10710 189.50 10.04 1.79 0.00 0.00 0.20 4.28 0.00 0.30 0.00 2.49 10726 190.50 8.64 4.40 0.00 0.00 0.00 2.55 0.00 0.81 0.00 2.08 10743 191.50 6.63 12.67 0.00 0.00 0.00 0.60 0.00 0.00 0.00 0.00 10760 192.50 8.21 3.41 0.00 0.00 0.24 2.68 0.00 0.00 0.00 0.73 10777 193.50 10.44 2.49 0.00 0.00 0.38 4.69 0.00 0.38 0.00 1.15 10794 194.50 7.02 2.71 0.00 0.00 2.71 3.28 0.00 0.14 0.00 1.42 10811 195.50 9.82 0.51 0.20 0.00 7.33 8.15 0.00 0.20 0.00 1.83 10827 196.50 8.12 1.85 2.22 0.00 7.88 8.37 0.00 0.62 0.00 2.96 10844 197.50 8.58 2.80 2.68 0.00 2.45 8.62 0.00 0.58 0.12 4.08 10861 198.50 8.89 2.25 1.46 0.00 0.34 11.02 0.00 0.67 0.00 1.91 10878 199.50 8.93 1.12 1.23 0.00 0.90 5.26 0.00 0.67 0.00 1.12 10895 200.50 9.63 2.18 1.14 0.00 2.28 6.54 0.00 0.83 0.00 1.77 10911 201.50 12.07 1.33 0.83 0.00 2.15 5.39 0.00 0.25 0.00 3.56 10928 202.50 7.75 0.90 2.32 0.00 2.71 9.29 0.00 0.26 0.00 1.55 10945 203.50 11.48 1.74 0.61 0.00 0.70 7.23 0.00 0.52 0.00 4.01 10962 204.50 5.53 5.24 0.54 0.00 0.00 2.17 0.00 0.36 0.00 0.72 10979 205.50 8.84 6.79 0.23 0.00 0.00 3.39 0.00 0.11 0.00 1.70 10996 206.50 7.90 4.56 0.00 0.00 0.00 7.47 0.00 0.63 0.00 1.39 11012 207.50 7.51 3.33 0.53 0.00 0.00 3.46 0.00 0.40 0.13 1.20 11029 208.50 11.07 2.80 0.18 0.00 0.00 2.80 0.00 0.00 0.09 2.08 11046 209.50 9.86 7.51 0.71 0.00 0.00 1.42 0.00 0.20 0.20 1.12 11063 210.50 9.51 7.68 2.52 0.00 0.00 0.00 0.00 0.00 0.00 0.00 11080 211.50 8.61 7.90 2.32 0.00 0.00 0.00 0.00 0.00 0.00 0.00 11097 212.50 6.87 5.82 1.02 0.00 0.00 0.00 0.00 0.00 0.00 0.29 11113 213.50 7.79 13.35 0.26 0.00 0.00 0.26 0.00 0.00 0.00 0.00 11130 214.50 6.90 12.32 0.00 0.00 0.00 1.01 0.00 0.00 0.00 0.43 11147 215.50 8.47 4.84 0.00 0.00 0.00 0.24 0.00 0.00 0.00 0.00

158

(cm)

Age

Valves per Gram per Valves

Depth

weightbag minus

vidua Valves per Gram viduaper Valves

ampla Valves per Gram per amplaValves

globosa Valves per Gram globosaper Valves

candida Valves per Gram candidaper Valves

stagnalis Valves per Gram per stagnalisValves

ohioensis Valves per Gram ohioensisper Valves

Stevensoni

paraohioensis Valves per Gram paraohioensisper Valves Candona (juev) Valves per Gram per (juev)Candona Valves 11164 216.50 11.01 4.90 0.00 0.00 0.00 2.09 0.00 0.00 0.00 0.27 11181 217.50 7.28 10.30 0.00 0.00 0.00 0.14 0.00 0.00 0.00 0.00 11197 218.50 5.93 4.05 0.00 0.00 0.00 1.01 0.00 0.00 0.00 0.17 11214 219.50 7.73 3.49 0.26 0.00 0.00 2.72 0.00 0.00 0.00 0.52 11231 220.50 6.34 6.15 0.47 0.00 0.00 0.00 0.00 0.16 0.00 0.00 11248 221.50 6.26 11.66 0.00 0.00 0.00 0.64 0.00 0.32 0.00 0.32 11265 222.50 8.88 5.52 0.00 0.00 0.00 0.11 0.00 0.00 0.00 0.00 11282 223.50 5.70 2.81 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 11298 224.50 7.63 4.98 0.26 0.00 0.00 0.13 0.00 0.26 0.00 0.00 11315 225.50 7.89 0.63 0.25 0.00 0.00 2.03 0.00 0.00 0.00 1.01 11332 226.50 7.05 2.41 1.70 0.00 0.00 0.71 0.00 0.00 0.00 0.43 11349 227.50 9.69 2.99 0.31 0.00 0.00 0.83 0.00 0.21 0.00 0.83 11366 228.50 7.04 4.12 0.71 0.00 0.00 0.00 0.00 0.00 0.00 0.00 11383 229.50 -1.80 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 11399 230.50 7.82 2.81 1.53 0.00 0.00 0.26 0.00 0.00 0.00 0.26 11416 231.50 7.88 1.65 0.89 0.00 0.00 0.76 0.13 0.00 0.13 0.00 11433 232.50 6.49 4.01 0.46 0.00 0.00 1.39 0.31 0.00 0.00 0.46 11500 233.50 8.85 2.94 1.13 0.00 0.00 1.81 0.34 0.00 0.00 0.00 11567 234.50 8.75 2.40 0.34 0.00 0.00 0.23 0.00 0.00 0.00 0.23 11633 235.50 7.03 0.57 1.28 0.00 0.00 1.71 0.00 0.00 0.00 0.57 11700 236.50 7.79 0.90 2.95 0.00 0.00 0.77 0.51 0.13 0.00 1.28 11767 237.50 7.66 0.00 0.78 0.00 0.00 0.26 0.00 0.00 0.00 0.00 11834 238.50 9.56 0.00 0.31 0.00 0.00 1.67 0.10 0.00 0.00 0.10 11900 239.50 8.55 0.00 1.52 0.00 0.00 1.52 0.23 0.00 0.00 0.00 11967 240.50 9.32 0.21 0.97 0.00 0.00 1.50 0.86 0.00 0.00 0.00 12034 241.50 7.65 0.13 2.22 0.00 0.00 1.57 0.92 0.00 0.00 0.00 12101 242.50 6.91 0.58 1.16 0.00 0.00 2.75 0.58 0.00 0.00 0.00

159

(cm)

Age

Valves per Gram per Valves

Depth

weightbag minus

vidua Valves per Gram viduaper Valves

ampla Valves per Gram per amplaValves

globosa Valves per Gram globosaper Valves

candida Valves per Gram candidaper Valves

stagnalis Valves per Gram per stagnalisValves

ohioensis Valves per Gram ohioensisper Valves

Stevensoni

paraohioensis Valves per Gram paraohioensisper Valves Candona (juev) Valves per Gram per (juev)Candona Valves 12168 243.50 7.07 0.00 1.56 0.00 0.00 0.42 0.71 0.00 0.00 0.00 12234 244.50 8.37 0.00 1.55 0.00 0.00 0.72 0.72 0.00 0.00 0.00 12301 245.50 8.09 0.00 2.35 0.00 0.00 1.61 0.62 0.00 0.00 0.00 12368 246.50 7.21 0.00 3.05 0.00 0.00 0.14 0.28 0.00 0.00 0.00 12435 247.50 6.17 0.16 0.32 0.00 0.00 0.32 0.49 0.32 0.00 0.00 12502 248.50 8.21 0.00 0.12 0.00 0.00 5.36 0.73 0.12 0.00 0.00 12568 249.50 6.50 0.46 0.15 0.00 0.00 12.92 0.00 1.23 0.00 0.00 12635 250.50 7.63 0.13 0.00 0.00 0.00 3.80 0.13 0.92 0.00 0.39 12702 251.50 5.87 1.53 0.00 0.00 0.00 7.16 0.00 0.68 0.00 0.85 12769 252.50 6.82 1.03 0.00 0.00 0.00 2.64 0.88 0.00 0.00 0.00 12835 253.50 7.11 3.94 0.00 0.00 0.00 1.83 0.00 0.00 0.00 0.00 12902 254.50 6.46 1.55 0.00 0.00 0.00 1.55 0.62 0.62 0.00 0.00 12969 255.50 7.29 0.69 0.00 0.00 0.00 3.43 0.27 0.82 0.00 0.82 256.50 7.24 0.00 0.00 0.00 0.00 3.04 0.69 0.14 0.00 0.55 257.50 8.09 0.00 0.00 0.00 0.00 3.96 0.62 0.12 0.00 0.12 258.50 6.41 0.00 0.00 0.00 0.00 4.21 0.62 0.00 0.00 0.00 259.50 7.42 0.27 0.00 0.00 0.00 2.29 1.75 0.00 0.00 0.40 260.50 6.59 0.30 0.00 0.00 0.00 4.25 0.91 0.00 0.00 0.46 261.50 8.62 0.00 0.00 0.00 0.00 3.25 0.46 0.00 0.00 0.23 262.50 7.12 0.00 0.00 0.00 0.00 1.40 1.26 0.00 0.00 0.14 263.50 9.80 0.00 0.00 0.00 0.00 2.24 2.65 0.00 0.00 0.00 264.50 7.43 0.00 0.00 0.00 0.00 1.08 0.27 0.00 0.00 0.00 265.50 7.77 0.00 0.00 0.00 0.00 0.26 0.77 0.00 0.00 0.00 266.50 7.18 0.00 0.00 0.00 0.00 0.42 0.56 0.00 0.00 0.00 267.50 7.35 0.00 0.00 0.00 0.00 0.27 0.14 0.00 0.00 0.00 268.50 7.70 0.00 0.00 0.00 0.00 1.30 1.17 0.00 0.00 0.00 269.50 6.85 0.00 0.00 0.00 0.00 2.04 1.17 0.00 0.00 0.00

160

(cm)

Age

Valves per Gram per Valves

Depth

weightbag minus

vidua Valves per Gram viduaper Valves

ampla Valves per Gram per amplaValves

globosa Valves per Gram globosaper Valves

candida Valves per Gram candidaper Valves

stagnalis Valves per Gram per stagnalisValves

ohioensis Valves per Gram ohioensisper Valves

Stevensoni

paraohioensis Valves per Gram paraohioensisper Valves Candona (juev) Valves per Gram per (juev)Candona Valves 270.50 9.37 0.00 0.00 0.00 0.00 1.28 0.21 0.00 0.11 0.00 271.50 7.48 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 7.67 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 5.97 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 7.30 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

161