PALEOCLIMATE INVESTIGATION AND INTERPRETATION OF LACUSTRINE
SEDIMENT FROM LAKE TELMEN AND LAKE UGIY, MONGOLIA
A Thesis
Presented to
The Graduate Faculty of The University of Akron
In Partial Fulfillment
of the Requirements of the Degree
Master of Science
Paul J. McDonald
December, 2008
PALEOCLIMATE INVESTIGATION AND INTERPRETATION OF LACUSTRINE
SEDIMENT FROM LAKE TELMEN AND LAKE UGIY, MONGOLIA
Paul J. McDonald
Thesis
Approved: Accepted:
Advisor Dean of the College Dr. John A. Peck Dr. Ronald F. Levant
Faculty Reader Dean of the Graduate School Dr. Lisa E. Park Dr. George R. Newkome
Faculty Reader Date Dr. Ira D. Sasowsky
Department Chair Dr. John P. Szabo
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ABSTRACT
Mongolia, located in Central Asia, experiences the most continental climate on
Earth. Although detailed paleoclimate data are abundant for selected areas throughout
Asia, datasets from within Mongolia are relatively scarce and demonstrate significant spatial and temporal variability. In older paleoclimatic reconstructions Mongolian climate was thought to be controlled by the East Asian monsoon system in a similar manner to China to the south. However in recent decades, additional paleoclimate records throughout central Asia have indicated a climate asynchronous with China, dominated by the Westerlies rather than the East Asian monsoon. The objective of this thesis study is to supplement existing paleoclimate proxy records in order to better understand Holocene climate variability in Mongolia and to assess the role of the
Westerlies in producing that variability.
This study produces new bulk-carbonate isotopic and mineralogic records for north-central Mongolia from a 7,110 year Lake Telmen and a 5,100 year Lake Ugiy sediment core. Lake Telmen is a saline (4 g/l), closed-basin lake, ideal for amplifying hydrologic variability into large sedimentological responses and is thus well-suited for paleoclimate study. The relatively heavy δ18O carbonate stable isotopes (averaging -0.5
‰) and abundant ankerite, quartz and phillipsite minerals suggest an arid climate dominated prior to approximately 4,500 yr B.P. Since 4,500 yr B.P., the Lake Telmen
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sediment data suggests an increase in humidity evidenced by lighter δ18O values
(averaging -1.2 ‰) with a corresponding mineralogical shift to abundant monohydrocalcite and calcite. These new records are in agreement with previous Lake
Telmen paleoclimate interpretations based upon pollen, diatoms and lithology, suggesting the East Asian monsoon does not control the Holocene climate in the Telmen region.
The Lake Ugiy sediment core mineralogy supports this interpretation, revealing abundant terrigenous minerals, a shallow lake, and more arid conditions prior to approximately
4,000 yr. B.P. A more humid climate since 4,000 yr B.P. is based on lacustrine mud with calcite and Mg calcite inferred to represent deeper water conditions. Brief arid intervals occur during the otherwise humid late Holocene as inferred from heavy isotope values and ankerite, quartz and phillipsite abundance in Lake Telmen, and abundant Mg calcite in Lake Ugiy at about 1,300-1,600, 2,000-2,200 and 2,800-3,100 yr B.P.
The records from this thesis study support published interpretations that suggest central Asian Holocene climate is dominated by the Westerlies and is asynchronous with
Chinese climate dominated by the East Asian monsoon. A North Atlantic high pressure system associated with cold sea surface temperature (SST) redirected the Westerly track causing the movement of dry air into Mongolia during the early Holocene. However, during the early Holocene increased boreal summer insolation produced a stronger East
Asian summer monsoon system and increased moisture in China. By the late Holocene the disappearance of the Laurentide ice sheet allowed for increased North Atlantic SST and the development of a low pressure system. The more zonal Westerlies now carried warm moist air across Europe and into Mongolia thereby increasing the moisture balance in the late Holocene. During the late Holocene, North Atlantic SST periodically cooled
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due to ice rafting. The cold North Atlantic and altered atmospheric pressure gradient may have diverted the path of the Westerlies so that cold dry air flowed into Mongolia.
These cold episodes are known as Bond cycles and included events dated at 1,400 and
2,800 yr B.P. These Bond cycles are similar in age to brief arid events within Mongolia and suggest hemispheric teleconnnection and a possible role for North Atlantic SST to influence Mongolian climate.
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ACKNOWLEDGEMENTS
First I would like to thank the National Science Foundation for providing the opportunity for the 1998 and 1999 Mongolian lake coring expeditions of which my advisor, Dr. John Peck, was a part. I would also like to thank Dr. Peck for providing me the opportunity to analyze the Lake Telmen and Lake Ugiy sediment cores, but more importantly for the continuing support throughout the duration of this thesis study. His dedication to the geoscience field has been both an inspiration and a motivation, not only making this study possible, but making its completion a reality. I would also like to thank my thesis committee members, Dr. Ira Sasowsky and Dr. Lisa Park for their time and support through the duration of this study. I owe a great deal of gratitude especially to Dr. Michael Rosenmeier for access to the Stable Isotope Laboratory at the University of Pittsburgh where the carbonate isotopes were measured. I would also like to express my appreciation for the administrative and technical support of Elaine Butcher and Tom
Quick. Their constant academic guidance and technical support with all equipment from electronics to mechanics and everything in between have been an integral part of the completion of my degree. Finally, I would like to thank the Department of Geology and
Environmental Science for the opportunity to enter the Master of Science degree program at the University of Akron and for the imparted experiences I will carry beyond degree completion.
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TABLE OF CONTENTS
Page
LIST OF TABLES ...... x
LIST OF FIGURES ...... xi
CHAPTER
I. INTRODUCTION ...... 1
II. GEOLOGIC SETTING ...... 3
2.1 Mongolia ...... 3
2.2 Lake Telmen ...... 13
2.3 Lake Ugiy...... 21
III. METHODS ...... 28
3.1 Carbonate Stable Isotope Analysis ...... 28
3.2 X-ray Diffraction ...... 32
3.3 Scanning Electron Microscopy ...... 33
3.4 AMS Radiocarbon Age ...... 37
IV. RESULTS ...... 38
4.1 Lake Telmen ...... 38
4.1.1 Core Lithology ...... 38
4.1.2 Carbonate Stable Isotope Analysis ...... 40
4.1.3 Mineralogy ...... 42
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4.1.4 SEM Data ...... 44
4.1.5 Age Model ...... 48
4.2 Lake Ugiy...... 48
4.2.1 Core Lithology ...... 48
4.2.2 Carbonate Stable Isotope Analysis ...... 53
4.2.3 Mineralogy ...... 53
4.2.4 Age Model ...... 55
V. DISCUSSION ...... 58
5.1 Carbonate Stable Isotope and Lacustrine Sediment Minerology as Paleoclimate Indicators ...... 58
5.2 Lake Telmen Paleoclimate Record ...... 62
5.2.1 Holocene Climate Variability ...... 63
5.2.2 Climate Forcing Mechanisms ...... 71
5.3 Lake Ugiy Pilot Study ...... 79
VI. SUMMARY ...... 82
REFERENCES ...... 85
APPENDICES ...... 93
APPENDIX A. LAKE TELMEN FINE-FRACTION (<63 μm) BULK CARBONATE STABLE ISOTOPE STANDARDS NBS-18 AND NBS-19 DATA ...... 94
APPENDIX B. LAKE TELMEN FINE-FRACTION (<63 μm) BULK CARBONATE STABLE ISOTOPE CORES C1 AND C4 DATA...... 96
APPENDIX C. LAKE TELMEN FINE-FRACTION (<63 μm) BULK CARBONATE STABLE ISOTOPE REPLICATE DATA ...... 99
APPENDIX D. LAKE TELMEN X-RAY POWDER DIFFRACTOMETER MINERALOGY DATA...... 101
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APPENDIX E. LAKE UGIY X-RAY POWDER DIFFRACTOMETER MINERALOGY DATA...... 106
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LIST OF TABLES
Table Page
1 Lake Telmen tie points used to correlate Core 4 to Core 1 ...... 22
2 Sediment samples containing undifferentiated adult ostracod valves ...... 30
3 Lake Telmen XRD mineralogical data and primary peak that was measured for its intensity ...... 35
4 Lake Ugiy XRD mineralogical data and primary peak that was measured for its intensity ...... 36
5 Lake Telmen AMS radiocarbon age converted to calendar year ...... 50
6 Lake Ugiy AMS radiocarbon age converted to calendar year ...... ………..56
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LIST OF FIGURES
Figure Page
1 Location of Mongolia in central Asia, a region of extreme continental climate. ....4
2 Mean monthly temperature (A) and precipitation (B) between 1966-1983 for Tumentsogt, Mongolia ...... 5
3 Summer (A) and winter (B) Asian air mass circulation (C-cyclone, A-anticyclone, H-high pressure, L-low pressure) ...... 7
4 Map of Asia indicating fluctuating Asian monsoon boundaries over the last 18,000 years for the eastern and southwestern monsoons with the modern monsoon climate region shaded ...... 8
5 Central Asian map indicating climate influence of the Westerlies (A), Indian summer monsoon (B), East Asian summer monsoon (C), and the current northern limit of the East Asian summer monsoon (D) ...... 9
6 The Holocene paleoclimate reconstruction for central Asia divided into four time windows ...... 11
7 Location of Lake Telmen and Lake Ugiy within north-central Mongolia ...... 14
8 Lake Telmen photo mosaic created from photos taken during different seasons ...... 15
9 Lake Telmen bathymetric map (depth in meters) with core and surface grab sample locations indicated ...... 16
10 Lake Telmen photograph, looking NW from the 99-S8 location (see Figure 9), taken during terrace measurement ...... 18
11 Lake Telmen July 1999 water column profile showing a well-developed thermocline at 10 m and low dissolved oxygen in the hypolimnion declining to hypoxic levels (<2 ppm) below 22 m depth...... 19
12 (A) Lake Telmen SEM backscatter image showing sediment varves comprised
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of white layers of monohydrocalcite deposited during the productive summer months (B) and dark layers of amorphous organic matter deposited during the remainder of the year (C) ...... 20
13 Lake Ugiy image showing both in and out flowing rivers (red arrows) to the west ...... 23
14 Lake Ugiy bathymetric map (depth in meters) with the core location marked (star) within the deep central basin near the 15.3 m water depth ...... 24
15 Photograph of Lake Ugiy looking south and showing steppe vegetation on hillslopes of low relief ...... 25
16 Lake Ugyi July 1999 water column profile showing low dissolved oxygen in bottom waters declining to hypoxic levels (<2 ppm) below 11 m depth ...... 26
17 Diagram showing carbon and oxygen isotope preference of various waters under differing climate and biomass conditions ...... 31
18 X-ray diffractogram with select mineral peaks labeled for a representative sample (TN99C1S1 60-61cm) ...... 34
19 Lake Telmen wet bulk density (WBD) with two tie lines shown and core lithology ...... 39
20 Lake Telmen Core 1 (red) and Core 4 (blue) bulk carbonate, fine-fraction stable isotope data compared to core lithology ...... 41
21 Semi-quantitative XRD mineralogy showing monohydrocalcite (MC), calcite (C), ankerite (A), quartz (Q), and phillipsite (P) ratios normalized by 25 weight percent corundom (CR) standard ...... 43
22 The % CaCO3 from the Telmen core is plotted against the monohydrocalcite, calcite and ankerite mineral peak counts per second (CPS) intensity ...... 45
23 SEM images from Lake Bosumtwi, Ghana ...... 46
24 SEM images taken from four different Lake Telmen core depths...... 47
25 EDX elemental scans (X-axis units are keV) from four different Lake Telmen core depths ...... 49
26 Lake Telmen age model derived from AMS radiocarbon dates indicating the 3.5 m core spans approximately 7000 years ...... 51
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27 Lake Ugiy Core 1 wet bulk density (WBD) plotted alongside % CaCO3 and core lithology on depth...... 52
28 Semi-quantitative XRD mineralogy showing calcite (C), Mg-calcite (MgC), albite (Alb), sodian anorthite (An) and quartz (Q) ratios normalized by 25 weight percent corundom (CR) standard ...... 54
29 Lake Ugiy age model derived from AMS radiocarbon dates indicating the 3.65 m core spans approximately 5100 years ...... 57
30 Crossplot showing the relationship between δ18O and δ13C by lithologic zone for all samples measured from cores C1 and C4 ...... 60
31 Carbonate stable isotopes, pollen-based aridity (Fowell et al., 2003), ankerite (A/CR) abundance, diatom-based salinity and lithology ...... 65
32 Carbonate stable isotopes, pollen-based aridity (Fowell et al., 2003), quartz (Q/CR) abundance, salinity and lithology ...... 66
33 Semi-quantitative XRD mineralogy on age showing monohydrocalcite (MHC), calcite (C), ankerite (A), quartz (Q), and phillipsite (P) ratios normalized by 25 wt % corundum (CR) standard ...... 69
34 Maps showing the influence of Arctic Oscillation (AO)/North Atlantic Oscillation (NAO) and North Atlantic sea surface temperature (SST) on the track of the northern latitude Westerly winds ...... 73
35 Holocene climate records from Lake Telmen compared to summary climate reconstructions from Asia ...... 75
36 Plot of select downcore Lake Telmen climate proxies and lithology are plotted on the calibrated radiocarbon age model ...... 78
37 Plot of semi-quantitative XRD mineralogy from Lake Ugiy plotted on age showing calcite (C), Mg-calcite (MgC), albite (Alb), sodian anorthite (An) and quartz (Q) ratios normalized by 25 wt % corundom (CR) standard ...... 80
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CHAPTER I
INTRODUCTION
Paleoclimate data collection from Mongolia is a relatively recent activity, largely
confined to studies during the last two decades (Jacoby et al., 2003; Nandintsetseg et al.,
2007). Although detailed paleoclimate data are abundant for selected areas throughout
Asia, datasets from Mongolia are scarce. Paleoclimatic information for Mongolia has
largely been extrapolated from Chinese or Russian sites because data collection and
regional synthesis often stop at the political boundaries (Velichko, 1984; Winkler and
Wang, 1993). With limited data from Mongolia, it was sometimes assumed that the
mechanisms driving the climate in Mongolia were an extension of the monsoon system in
China. Mongolia’s climate was thought to be controlled by the East Asian monsoon and the Siberian high pressure air mass (Winkler and Wang, 1993). However as data collection from within Mongolia and throughout the rest of central Asia increased, it became apparent that Mongolia’s climate varied from that of China (Peck et al., 2002;
Soninkhushig, et al., 2003; Feng et al., 2005; Prokopenko et al., 2005). Accompanying these new data were new ideas concerning the role of the Westerlies on climate variability throughout central Asia (Pederson et al., 2001; Chen et al., 2008).
Understanding regional climate variability is significant, both on spatial and temporal scales, and for human and economic development. A better assessment of regional climate variability in Mongolia can reveal the range of climatic conditions
1 experienced in the recent (Holocene) past. Such data can aid in resource management, as
well as contribute to a greater scientific understanding of such a climatologically unique area. Mongolia’s harsh climate and drastic temperature variation makes habitation
difficult. Instrumental meteorological records from 1940–1975, reveal a 3-5 year
summer drought cycle, and 11 spring droughts (Tuvdendorzh and Myagmarzhave, 1985,
cited in Peck et al., 2002). In 1999, Mongolia suffered a devastating summer drought
followed by intense winter snowfall. This climatic combination greatly decreased
vegetation and caused the starvation death of approximately 2 million livestock
(Pederson et al., 2001). Thus, greater understanding of both short-term and long-term
climate variability can benefit Mongolian society.
The purpose of my thesis research is to investigate Holocene climate variability
for north-central Mongolia using the sediments of Lakes Telmen and Ugiy.
Radiometrically-dated lake cores were analyzed for carbonate stable isotopes, X-ray
diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray
spectroscopy (EDX) in order to assess past hydrologic variability. This thesis research
has contributed new proxy records of past climatic variability that builds upon existing
data sets from these lakes (Peck et al., 2002, Fowell et al., 2003, Soninkhishig et al.,
2003). This improved multidisciplinary effort has led to a better understanding of central
Asian climate variability and the underlying forcing mechanism of this variability.
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CHAPTER II
GEOLOGIC AND CLIMATIC SETTING
2.1 Mongolia
Mongolia is a landlocked country located on the Asian continent (Figure 1). The country’s land area is slightly larger than 1.5 million km2, with nearly 3 million inhabitants (CIA, 2008). The land has little agricultural value because the terrain is dominated by mountains, forest steppe, grassland steppe, and desert in the south (CIA,
2008). Mongolians are known as a nomadic, pastoral people, having adapted to the region’s limited vegetation and large climate variability by herding livestock and moving seasonally with their herds. The nearly 30 million livestock consume large amounts of the limited steppe vegetation (Nandintsetseg et al., 2007). A pastoralist lifestyle coupled with the occurrence of extreme winter blizzards heavily impacts both the livestock and the people. Between 1999 and 2002, nearly 3 million livestock died both directly and indirectly from the result of these blizzards, leaving over 12,000 families with no livestock (Nandintsetseg et al., 2007).
The temperature at Tumentsogt, Mongolia fluctuates as much as 51°C annually, greater than anywhere else on Earth, with a mean summer high of 27.5°C and a mean winter low of -23.5°C (Figure 2A) (Togtohyn and Ojima, 1996). Instrumental records indicate temperature fluctuations as great as 30°C in one day (Jacoby et al., 1996).
3
Figure 1. Location of Mongolia in central Asia, a region of extreme continental climate. The lakes studied are located in north central Mongolia (CIA, 2008).
4
A
35 25 15 High 5 -5 Low
Temperature (°C) Temperature -15 -25 123456789101112 Month
B
90 80 70 60 50 40 30
Precipitation (mm) Precipitation 20 10 0 123456789101112 Month
Figure 2. Mean monthly temperature (A) and precipitation (B) between 1966-1983 for Tumentsogt, Mongolia. Mongolia has an extreme seasonal climate, having temperature shifts as great as 50° Celcius from winter to summer with the average high temperature in blue and the average low temperatures in red (A). Nearly all of the precipitation falls during summer months (Togtohyn and Ojima, 1996).
5 Northern Mongolia is a subarctic zone, transitioning to steppe in the central region, and to
desert in the south. As a landlocked country beyond the reach of the summer monsoonal
rains, northern Mongolia receives an average 300-400 mm/yr of precipitation, with 150-
250 mm/yr in the central Mongolian steppe, and 50-100 mm/yr falling in the Gobi Desert
in the southern region (Nandintsetseg et al., 2007). Nearly all of Mongolia’s yearly
precipitation falls during the summer months of June, July and August (Figure 2B). The large variation in seasonal temperature and precipitation is exaggerated by Mongolia’s location at the convergence of the Asian monsoon system and the mid-latitude
Westerlies.
Boreal summer heating of the land and latent heating in the troposphere create a low pressure, warm air mass over the Mongolian and Tibetan Plateaus (Figure 3A) (Hong
Kong Observatory, 2003). Moist, onshore winds from the Pacific Ocean bring precipitation to large parts of China. During the winter months, the high pressure
Siberian air mass is established over Mongolia (Figure 3B) and the country experiences
extremely cold temperatures with very little precipitation (Figure 2) (Nandintsetseg et al.,
2007). Although the strength of the East Asian monsoon has varied greatly throughout
the Holocene, at the present time the northern limit of the summer monsoon extends only
to northern China, thus the heavy summer monsoon precipitation does not reach
Mongolia (Figure 4) (Winkler and Wang, 1993). Figure 5 shows the complexity of Asian climate in the vicinity of Mongolia which lies at the convergence of the mid-latitude
Westerlies, the Indian monsoon and the East Asian monsoon (Herzschuh, 2006; Chen et al., 2008).
6
A.
B.
Figure 3. Summer (A) and winter (B) Asian air mass circulation (C-cyclone, A- anticyclone, H-high pressure, L-low pressure). Heating and onshore and offshore atmospheric pressure differences are the driving forces for the East Asian monsoon (Hong Kong Observatory, 2003).
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8
Figure 4. Map of Asia indicating fluctuating Asian monsoon boundaries over the last 18,000 years for the eastern and southwestern monsoons with the modern monsoon climate region shaded (modified from Winkler and Wang, 1993). Red circle indicates study area.
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Figure 5. Central Asian map indicating climate influence of the Westerlies (A), Indian summer monsoon (B), East Asian summer monsoon (C), and the current northern limit of the East Asian summer monsoon (D). Also shown are the locations of paleoclimatic records (1-12, a-i) used by Chen et al., (2008) for a regional climate synthesis. Lake Telmen (7) and Lake Ugyi (13) were analyzed in this thesis. Colors indicate relative elevation with red indicating high and green indicating low (Figure modified from Chen et al., 2008). Mongolian instrumental meteorological data rarely extend prior to the 1940’s, and
thus provide only a short record of climate change (Togtohyn and Ojima, 1996; Peck et
al., 2002). Longer time-scale trends are difficult to assess with short-term data such as
the instrumental record. Therefore, proxy data must be found to extend the instrumental
record further into the past. There are a variety of published central Asian proxy
paleoclimate records obtained from tree rings, lake sediment, loess sediment, and
speleothems. Lake level status analyses based on multiple geologic and biologic proxies
have shown a great deal of spatial and temporal variability throughout central Asia
(Figure 6) (Chen et al., 2008).
Tree rings have been analyzed from climate-sensitive trees, namely Siberian pine,
Siberian larch, and Scots pine in the few forested areas of northeastern Mongolia
(Pederson et al., 2001). Most Mongolian tree-ring records are 300-500 years old (Jacoby et al., 1996), although some tree-ring records extend as far back as nearly 2,000 years
(D’Arrigo et al., 2001). The fluctuations in tree-ring width have been interpreted to
indicate variability of relative temperature (D’Arrigo et al., 2000; D’Arrigo et al., 2001),
as well as local precipitation and streamflow (Pederson et al., 2001; Jacoby et al., 2003).
Aside from showing accurate seasonal and yearly trends, tree-ring analysis shows
periodicity in moisture cycles of 12 and 20-24 yrs that may be attributed to solar cycles
(Pederson et al., 2001). These cycles may account for the changes in aridity over the last
400 years as normal fluctuations, rather than the beginning of a long-term climatological shift towards arid conditions (Pederson et al., 2001). However, additional tree-ring temperature records agree with modern instrumental records and with the large-scale
Northern Hemisphere temperature reconstructions that show 20th century warming
10 13 11
Figure 6. The Holocene paleoclimate reconstruction for central Asia divided into four time windows (Chen et al., 2008). The data shows an “out of phase relationship” between paleoclimate reconstructions to the north (1-12) and to the south (a-i) of the current northern monsoon limit of the East Asian monsoon (dashed line) during the late and early Holocene to the present. Lake Telmen (7) and Lake Ugiy (13) are shown in the upper left window. The middle Holocene, however, shows humid conditions above and below the northern summer monsoon limit. Colors indicate relative elevation with red indicating high and green indicating low. (Jacoby et al., 2003). In addition to tree-ring width, stable isotope analysis of tree
cellulose has been used to infer the intensity of the Asian monsoon (Feng et al., 1999).
Loess and paleosol deposits also provide paleoclimatic information. Loess
formation and deposition occur during arid conditions, and soil formation and paleosol
development is enhanced when the climate is more humid (Bradley, 1999). The Northern
Mongolian Plateau contains varying sequences of loess, soil, and colluvium that provide
paleoclimatic records spanning the last 34,000 years B.P. (Feng, 2001). Within the
Holocene, paleosols have been dated and indicate wetter conditions at 8,300, and 4,070 yrs B.P., and loess accumulation indicates dry conditions between 8,300 and 4,070 yrs
B.P. (Feng, 2001). In addition, paleosols indicate overall wet conditions with intervals of increased aridity within the past 2000 years (Feng, 2001). These wet/dry periods generally correspond to proxy data (e.g., diatoms, palynology) collected from Lake
Telmen sediments (Peck et al., 2002; Fowell et, al., 2003; Soninkhishig et al., 2003).
Additional proxy records of past climate variability can be obtained from the
study of undisturbed lake sediments. Lake sediments can be analyzed for physical and
chemical sediment properties, as well as biological remains, to yield proxy records of
paleoclimate (Schnurrenburger et al., 2003). Mongolian lake sediments have been
analyzed using palynology (Tarasov et al., 1998; Fowell et al., 2003), diatoms
(Soninkhishig et al., 2003), and sediment composition (Peck et al., 2002; Prokopenko et
al., 2005). The sediments of Lake Hovsgol, Mongolia were analyzed for lithology,
magnetic susceptibility, biogenic silica, and pollen content and show warmer summer
temperatures after approximately 7,000 yr B.P. and a lake level low stand at 6,600 yr B.P.
(Prokopenko et al., 2007). Variations in calcium carbonate percentage have also been
12 used to show seasonal variations in sedimentation in Mongolian Lake Telmen (Peck et
al., 2002). Authigenic calcium carbonate formation occurs in the summer when algal
activity consumes carbon dioxide from within the lake, increasing pH, and inducing the
precipitation of calcite crystals. During winter months the lake is undersaturated with
respect to carbonate and amorphous organic matter settles to the lake floor (Peck et al.,
2002). Although the calcium carbonate content was determined, no analysis of the
carbonate stable isotopes was made from Lake Telmen sediment cores. Measuring the
stable isotopes can provide hydrological information to further the paleoclimate
investigation and was a focus of this thesis research.
Closed-basin Lake Telmen (Figure 5 site 7) and open-basin Lake Ugiy (Figure 5
site 13) located in north-central Mongolia have been previously cored using a modified
Kullenberg piston corer during a 1999 five lake coring expedition (Figure 7) (Peck et al.,
2000). These existing cores have already been studied using a variety of techniques
including lithology, diatom, pollen, and carbonate analyses (Peck et al., 2000; Peck et al.,
2002; Fowell et al., 2003; Soninkhishig et al., 2003). This thesis focuses primarily on
producing new proxy records from the existing Lake Telmen cores, however a pilot study
of select samples from the Lake Ugiy core were also analyzed.
2.2 Lake Telmen
Lake Telmen (Figure 8), Mongolia is located at 48°59’N, 97°20’E and lies 1789
m asl. It is currently a 194 km2 closed basin, saline lake containing anion concentrations of sulfate (1,486.1 mg/l), chloride (1,182.7 mg/l), nitrate (0.161 mg/l), and phosphate
(0.106 mg/l). The lake lies within a 4,180 km2 catchment showing pronounced lake level
13
Figure 7. Location of Lake Telmen and Lake Ugiy within north-central Mongolia (modified from Peck et al., 2000). Three other lakes cored during the 1999 coring expedition are also shown as well as topography indicated by shading.
14
4km
Figure 8. Lake Telmen photo mosaic created from photos taken during different seasons. The western portion of the image was captured during the warm summer months whereas the eastern portion images are from the winter months when the lake surface is frozen (Google Earth, 2007).
15
16
Figure 9. Lake Telmen bathymetric map (depth in meters) with core and surface grab sample locations indicated (Peck et al., 2002). The cores used in this study (99-C1 and 99-C4) were collected from the deepest part of the lake in order to recover a thick sediment sequence. changes and highstand terraces over the past 7,110 years (Peck et al., 2002). Water depth averages 13 m with a maximum depth of 27 m (Figure 9) and the lake has a salinity of 4 g/l (Peck et al., 2002). The Lake Telmen catchment contains igneous and siliciclastic sedimentary rocks and no carbonate sedimentary rocks (Figure 10). Therefore, the carbonates found in the lake are biogenic and authigenic, as confirmed by SEM and XRD analyses (Peck et al., 2002). During the summer months a well developed thermocline is present at approximately 11 m (Figure 11). The dissolved oxygen (DO) curve indicates hypoxic conditions exist at the bottom of the lake in summer and limit a benthic community. The bottom sediments remain undisturbed by bioturbation within the deep water basin. During summer months, algal blooms within the lake cause a CO2 drawdown, lowering the pH and allowing for the precipitation and accumulation of authigenic carbonates (Peck et al., 2002). However during winter months the algae dies and amorphous organic matter accumulates on top of the summer time carbonate layer.
Because the authigenic carbonates are mostly precipitated during the summer months, the carbonate isotopes will therefore represent summertime hydrologic conditions. Existing data for Lake Telmen includes elevation profiles of highstand terraces (Figure 10), and water-column profiles (Figure 11) of temperature, dissolved oxygen, turbidity, salinity and pH (Peck et al., 2002). In addition, both lake surface sediments and sediment cores have been measured for pollen and diatom assemblages, calcium carbonate content, water and organic content, sediment bulk density, SEM varve study (Figure 12) and radiocarbon dating (Peck et al., 2002; Fowell et al., 2003; Soninkhishig et al., 2003). The pollen data was used to create a semiquantitative aridity index by dividing the sum of
Artemisia (sage) plus Chenopodiaceae (sedge) pollen by Poaceae (grass) percentage
17
18
Figure 10. Lake Telmen photograph, looking NW from the 99-S8 location (see Figure 9), taken during terrace measurement. Note the limited forest and abundant steppe vegetation covering the slopes (Photograph from J. Peck).
Temperature (°C) Dissolved oxygen (ppm) Turbidity (NTU) Salinity (‰) 0 5 10 15 0510 0 50 100 150 44.4 0
5
10 19 Depth (m)
15
20
25
Figure 11. Lake Telmen July 1999 water column profile showing a well-developed thermocline at 10 m and low dissolved oxygen in the hypolimnion declining to hypoxic levels (<2 ppm) below 22 m depth. Plankton activity creates a turbidity peak at 11 m (modified from Peck et al., 2002).
Figure 12. (A) Lake Telmen SEM backscatter image showing sediment varves comprised of white layers of monohydrocalcite deposited during the productive summer months (B) and dark layers of amorphous organic matter deposited during the remainder of the year (C) (from Peck et al., 2002).
20 (Fowell et al., 2003). Diatoms were used to determine past salinity based on the salinity tolerance of the diatom taxa found at various core depths (Soninkhishig et al., 2003).
From Lake Telmen, core TN99-C1 (hereafter referred to as C1), measuring 186
cm long, and core TN99-C4 (hereafter referred to as C4), measuring 328 cm long, were
recovered from the deep part of the basin with 24.54 m water depth. The two cores were
previously correlated by Peck et al. (2002) in order to construct a composite sediment section. C1 and C4 were both collected from the deep central basin within close proximity to one another making correlation possible. C1 (0-186 cm) and C4 sub- sections (162-328 cm) were aligned using wet bulk density (WBD) lithologic parameters, shifting C4 down 15 cm and yielding a correlated core depth of 343 cm (Table 1). For this study, the cores were sampled at varying intervals ranging from 1 to 10 cm spacing.
Sample spacing was dependent both on availability, as the core had undergone previous sampling, and lithologic changes.
2.3 Lake Ugiy
Lake Ugiy, Mongolia (Figure 13), located at 47°45’N, 102°45’E, is a 25 km2, open basin, freshwater lake with a maximum depth of 15.3 meters (Figure 14). The lake has both inflowing and outflowing rivers; therefore it has a different hydrologic balance than a closed basin lake. The lake lies within a steppe region of low relief
(Figure 15). The bedrock geology of the large Lake Ugiy catchment contains diverse rock types including marble (Peck written communication, 2007). The presence of marble in the catchment may contribute detrital carbonate to the lake. Existing data for
Lake Ugiy includes water column profiles of temperature, dissolved oxygen, turbidity
21 Table 1. Lake Telmen tie points used to correlate Core 4 to Core 1 (Peck et al., 2002). TN99-C4 TN99-C1 Core depth (cm) Core depth (cm) 5.5 4.1 79 101.1 93 114.6 147.8 163.1 155.8 170.6 163.3 178.6 166.8 181.6
22
4km
Figure 13. Lake Ugiy image showing both in and out flowing rivers (red arrows) to the west (Google Earth, 2007).
23
24
4km
Figure 14. Lake Ugiy bathymetric map (depth in meters) with the core location marked (star) within the deep central basin near the 15.3 m water depth (Peck written communication, 2007).
Figure 15. Photograph of Lake Ugiy looking south and showing steppe vegetation on hillslopes of low relief (Photograph from J. Peck).
25 Temperature (°C) Dissolved oxygen (ppm) Turbidity (NTU) Salinity (‰) 0 5 10 15 20 25 05100255075 00.1 0
5 26 Depth (m)
10
15
Figure 16. Lake Ugyi July 1999 water column profile showing low dissolved oxygen in bottom waters declining to hypoxic levels (<2 ppm) below 11 m depth. As an open basin lake, it contains freshwater with a constant salinity of nearly zero (Peck et al., 2000). and salinity (Figure 16), as well as sedimentary water and organic content, sediment bulk density, magnetics and 14C age (Peck et al., 2000). Hypoxic bottom waters occur during the summer despite the lack of a well-defined thermocline. Water column turbidity increased with depth possibly related to biological activity or lake floor resuspension.
27
CHAPTER III
METHODS
3.1 Carbonate Stable Isotope Analysis
Carbonate stable isotope (δ13C and δ18O) variations within lacustrine sediments have often been successfully interpreted as paleoclimate indicators (Wei and Gasse,
1999; Wang et al., 2002; Lamb et al., 2005; Leng et al., 2005). Carbonate stable isotopes from different sediment types have also been used for paleoclimate analysis such as palustrine carbonates and calcretes (Alonso-Zarza, 2003, Sinha et al., 2006), loess deposits (Li et al., 1995), and ostracod valves (Von Grafenstein et al., 1999; Bright et al.,
2006).
Following the method outlined by the Limnological Research Center Core
Facility (LRC core facility, 2004) the carbonate stable isotopes from Lakes Telmen and
Ugiy were analyzed. The sediment sample is collected from the core, bleached to remove organic matter, rinsed at least three times to remove the bleach and then sieved at 63 microns to remove sand-sized particles from the mud. The mud is then freeze-dried and analyzed for oxygen and carbon stable isotopes of the carbonate fraction. The samples were measured on a GV Instruments, Ltd. Isoprime stable-isotope mass spectrometer at the University of Pittsburgh. The spectrometer separates the isotopes of carbon and oxygen by mass as they pass through a magnetic field. Ratios of 18O:16O and 13C:12C can
28 then be calculated relative to a standard reference material (Leng, 2005). Replicate tests
were carried out on 20 samples that yielded suspect 13C and 18O isotope values. Two
standards, NBS-18 and NBS-19, were also analyzed in each sample batch (Appendix A).
The NBS-18 and NBS-19 standards yielded consistent δ13C and δ18O values, indicating
properly functioning equipment. The standard deviation for the NBS-18 standard was
0.08 ‰ for 13C and 0.11 ‰ for 18O. The standard deviation for the NBS-19 standard was
0.07 ‰ for 13C and 0.08 ‰ for 18O.
As supporting data, ostracod valves were picked from the bulk sediment for future
species identification and carbonate stable isotope analysis (Table 2). Due to possible
vital effects displayed by juvenile valves as well as some adult species dependent
fractionation (Holmes, 1996; Von Grafenstein et al., 1999; Leng and Marshall, 2004),
only adult species were picked from the sediment coarse fraction.
This study focuses on the interpretation of changing δ18O and δ13C ratios
measured on authigenic carbonate sampled down the core. Carbonate in lake sediments
have been successfully analyzed for stable isotopes (Figure 17) to provide
paleohydrologic information (Rosenmeier et al., 2002; Leng, 2005). When water
evaporates, the lighter 16O isotope will evaporate more readily than the heavier isotope
18O and result in the remaining water being enriched in 18O (Leng, 2005). Conversely, the heavier 18O will precipitate at a higher fraction than 16O, leaving the remaining water
vapor in the atmosphere isotopically lighter. Authigenic calcite (CaCO3), precipitated
within the lake water, reflects lake water isotope ratios at the time of precipitation and
29 Table 2. Sediment samples containing undifferentiated adult ostracod valves. TN-Lake Telmen samples UN-Lake Ugiy samples. Lithologic zones: A-laminated, brown organic rich mud B-bedded black, brown, white mud C-brown silt D-black, gray, sandy mud with gastropods E-gray organic mud with organic clay Sample Corrected Lithologic Ostracod valve ID depth (cm) zone count TN-99 E G2 0-1 0 A 16 TN-99 E G9 0-1 0 A 33 TN-99 C4S2 104-105 230 A 9 TN-99 C4S3 44-45 282 B 70 TN-99 C4S3 51-52 288 B 16 TN-99 C4S3 85-86 321 C 20 TN-99 C4S3 89-90 326 C 7 TN-99 C4S3 95-96 331 C 16 TN-99 C4S3 99-100 336 C 7 UN-99 C1D1 0-1 0 D 26 UN-99 C1D1 20-21 19.4 D 31 UN-99 C1D3 24-25 225 E 17
30
Figure 17. Diagram showing carbon and oxygen isotope preference of various waters under differing climate and biomass conditions. Water molecules containing lighter oxygen isotopes will evaporate more readily than those containing heavier isotopes and therefore arid climates yield 18O enriched waters (plotting toward top of graph). Likewise organic matter utilizes lighter carbon isotopes more readily and therefore waters with a high biomass and organic sedimentation will be enriched in heavier carbon isotopes (plotting toward right of graph). The subsequent decay of this organic material releases the carbon and enriches the water in these lighter carbon isotopes (plotting toward left of graph) (Modified from Leng, 2005).
31 deposition (Leng, 2005). If a sediment layer from which the carbonate sample came can
be dated, then the isotopic composition of the lake water at that specific time can be
estimated. It is important to ensure the carbonate sediment is authigenic. If detrital carbonate is present, then the isotope chemistry will not accurately reflect the climatic conditions during lake sedimentation, but rather reflect the conditions relative to the pre- existing carbonate rock formation. Once the carbonate mineralogy is determined to be primarily authigenic, isotopic analysis will provide data regarding the environmental conditions present during the formation of the authigenic minerals. The stable isotopic composition of the authigenic carbonate, mainly monohydrocalcite, indicates paleoclimatic conditions based on the preferential evaporation of lighter isotopes
(Rosenmeier et al., 2002; Leng, 2005).
3.2 X-Ray Diffraction
X-Ray diffraction (XRD) has been successfully used to determine the mineralogy of lacustrine sediments. Sediment mineralogy can provide paleoclimatic information based upon understanding the conditions necessary for the deposition and preservation of certain minerals, particularly carbonates (Talbot and Kelts, 1986; Fillipi et al., 1998; Last,
2001; Li et al., 2008).
To better characterize the carbonate sediment measured for stable isotope ratios,
X-ray diffraction was used. For semi-quantitative XRD mineralogical analysis, the < 63
μm freeze dried sediment samples were ground to a powder with a spatula, weighed, and
25 weight percent of corundum standard was added (Chung and Smith, 2000; Last,
2001). The samples were placed on glass slides and analyzed using a Philips XRG 3100
32 Powder Diffractometer at the University of Akron. The samples were bombarded by copper K-alpha radiation at 40 kV and 35 mA and scanned between 2-60 2θ at a rate of
0.02 °/sec. The varying angles and intensities of the diffracted beams are recorded yielding physical, chemical and structural information. The peaks in the sample diffractogram were compared to mineral standard values in order to identify the minerals present in the sample (Figure 18) (Gavish and Friedman, 2006). The Lake Telmen diffractograms revealed the presence of 9 primary minerals (Table 3). The Lake Ugiy diffractograms were also examined for the same 9 primary minerals present in the samples (Table 4). Both Lake Telmen and Lake Ugiy diffractograms were examined for additional minerals to match remaining peaks. For each mineral, the counts per second
(CPS) values were recorded for both the peak and half peak, as were the 2θ and d-spacing values (Figure 18). The CPS values for each mineral were normalized by the CPS values for the 25 weight % corundum standard to determine the relative abundance variation of each mineral downcore.
3.3 Scanning Electron Microscopy
Sediment component identification through SEM imaging has been utilized successfully to characterize the types of carbonate minerals through variation in morphology and chemical composition (Talbot and Kelts, 1986; Uysal et al., 2000; Peck et al., 2002). Representative samples from different lithologic zones were imaged using an FEI Quanta 200 Environmental Scanning Electron Microscope at the University of
Akron. In addition, energy dispersive X-ray spectroscopy (EDX) was used for chemical characterization and elemental analysis by analyzing the X-rays emitted from the sample
33
PEAK CPS
MC CR
HALFPEAK CPS MC CR CR MC 2θ MC
MC
MC MC CR
34 CR MC MC Q C MC MC MC MC
Figure 18. X-ray diffractogram with select mineral peaks labeled for a representative sample (TN99C1S1 60-61cm). Red labels indicate mineral peaks that were measured for intensity. Blue labels identify secondary unmeasured peaks for these minerals. Inset indicates data recording method of the peak and half peak intensities. MC-monohydrocalcite, Q-quartz, C-calcite, A-ankerite, CR- corundum
Table 3. Lake Telmen XRD mineralogical data and primary peak that was measured for its intensity. XRD Mineral Mineral °2θ d-spacing Reference Number Corundum 43.360 2.085 100173 Monohydrocalcite 20.494 4.330 290306 Calcite 29.403 3.035 050586 Ankerite 30.766 2.904 410586 Mg-Calcite 29.712 3.004 430697 Dolomite 30.966 2.885 360426 Gypsum 31.123 2.871 210816 Phillipsite 27.804 3.206 391375 Quartz 26.638 3.344 461045
35
Table 4. Lake Ugiy XRD mineralogical data and primary peak that was measured for its intensity. XRD Mineral Mineral °2θ d-spacing Reference Number Corundum 43.360 2.085 100173 Monohydrocalcite 20.494 4.330 290306 Calcite 29.403 3.035 050586 Ankerite 30.766 2.904 410586 Mg-Calcite 29.712 3.004 430697 Dolomite 30.966 2.885 360426 Gypsum 31.123 2.871 210816 Phillipsite 27.804 3.206 391375 Quartz 26.638 3.344 461045 Albite 22.036 4.030 191184 Anorthite 27.886 3.197 200528
36 after bombardment with charged particles (Materials Evaluation and Engineering, Inc.,
2000).
3.4 AMS Radiocarbon Dating
Accelerator mass spectrometry (AMS) radiocarbon age was measured by Peck et al. (2002) from eight samples from Lake Telmen and four samples from Lake Ugiy. This sampling yielded millennial-scale resolution to the age control points. The humic acid fraction of the bulk sediment was dated and the Libby half-life of 5568 yr was used to calculate radiocarbon age. The CALIB4.3 program (Stuiver and Reimer, 1993) and
INTCAL98 calibration set (Stuiver et al., 1998) was used to convert radiocarbon ages to calendar years.
37
CHAPTER IV
RESULTS
4.1 Lake Telmen
The following subsections contain the lithologic, isotopic, mineralogic and radiocarbon age results from the Lake Telmen sediment cores C1 and C4.
4.1.1 Core Lithology
The Lake Telmen cores were divided into three main lithologic zones (Figure 19)
determined from cores C1, a two section core, and C4, a three section core. The lowest
zone consists of a very compact, light brown silty sediment (Peck et al., 2002). This zone
spans 308-343 cm correlated core depth and ends at the limit the corer was able to
penetrate the bottom sediment (Peck et al., 2002). In addition to color and bedding
differences, the wet bulk density (WBD) values for this zone are slightly lower than those
of the overlying zone.
The middle zone (232-308 cm) consists of thickly-laminated and bedded
alternating black to olive-brown and gray-white beds (Peck et al., 2002). The WBD of
this middle zone is higher than both the underlying and overlying zones. According to
Peck et al. (2002) the WBD and lithology vary at 105 and 210 year periods in the zone
and may reflect hydrologic variation related to solar forcing.
38 Core 1 Core 4 Composite Lithology WBD (g cm-3) WBD (g cm-3) WBD (g cm-3)
11.411.411.4 0
50
100
150
Depth (cm) 200
250
300
350
laminated, brown massive, brown bedded black, brown silt organic rich mud organic rich mud brown, white mud
Figure 19. Lake Telmen wet bulk density (WBD) with two tie lines shown and core lithology. The core can be divided into three zones. The lowest zone is a massive brown silt, the middle zone is bedded black, brown, white mud of variably high density, and the upper zone is laminated, brown organic rich mud with interbedded massive, brown organic rich mud and lower sediment density (Modified from Peck et al., 2002). Core photographs are shown to the right. The upper photo shows the transition from the laminated to massive sediment. The middle photo shows the bedded mud zone and the bottom photo shows the massive silt zone. The lower photo shows the an erosional contact in the silt unit
39 The upper zone (0-232 cm) consists predominantly of a thinly laminated (<1mm),
organic rich , olive-brown mud (Peck et al., 2002). Contained within this zone are three
major intervals of non-laminated, massive, organic-rich mud at 85-97, 127-130,
and 174-185 cm (Peck et al., 2002). The WBD of the upper zone is the lowest of the
three zones and steadily increases down core reflecting the effects of sediment
compaction.
4.1.2 Carbonate Stable Isotope Analysis
Fine-fraction (<63 μm) carbonate stable isotope analysis was carried out on 40
samples from C1 and 56 samples from C4 yielding both carbon and oxygen isotopic
ratios (Figure 20 and Appendix B) as well as 20 samples replicated due to suspect 13C
and 18O isotope values (Appendix C). The carbon isotopes display little overall change in
average value above (2.01 ‰) and below (1.92 ‰) the 241 cm core depth (Figure 20).
However, the average oxygen ratios values are heavier below 241 cm (δ18O -0.72‰) than
above 241 cm (δ18O -1.11‰). Though the δ13C values did not transition from heavier to lighter from lower to upper core, the δ18O values did, indicating arid conditions below
241 cm and relatively moister conditions above 241 cm. Lacustrine sediment δ13C ratios are a less accurate aridity indicator than δ18O ratios because of a greater number of
factors influencing the isotopic composition of carbon in lake water, such as high
carbonate alkalinity, CO2 concentrations and biological productivity (Wei and Gasse,
1999; Wang et al., 2002; Bright et al., 2006). Fluctuating lake levels can also affect the
δ13C and δ18O covariance (Leng et al., 2004). Conversely, the oxygen isotope averages
40 18 δ13C (‰) δ O (‰) Lithology
-3 0 3 -6 -3 -1 0 0
50 50
100 100
150 150
Depth (cm) 200 200 Depth (cm)
250 250
300 300
350 350
laminated, brown massive, brown bedded black, brown silt brown, white mud organic rich mud organic rich mud
Figure 20. Lake Telmen Core 1 (red) and Core 4 (blue) bulk carbonate, fine-fraction stable isotope data compared to core lithology
41 show a more significant shift to lighter isotopes above 241 cm. This is a more accurate
paleoclimate indicator as δ18O is primarily affected by precipitation/evaporation balance
in a closed-basin lake located in a non-carbonate watershed, such as Lake Telmen (Wei
and Gasse, 1999; Lamb et al., 2005; Leng et al., 2004). However, both isotope data
display a degree of covariance marked by isotope ratio fluctuations spacing 10’s of cm in
the downcore profile (Figure 20).
These isotopic fluctuations are most noticeable at the transition between of each
lithologic zones (Figure 20). The C1 isotope data correlate well with the data from C4,
verifying the reproducability of the isotope analysis. Slight isotope ratio differences
between the two cores are present at several locations, such as the heavier C1 δ18O values at approximately 128 cm (Figure 20). Despite these differences, both Core 1 and Core 4 display the same overall trends. The discrepancy may be related to differences in the sampling interval between the two cores.
4.1.3 Mineralogy
Core C1 and C4 mineralogy was determined using semi-quantitative XRD analysis. As was the case with the carbonate stable isotope analysis, the XRD analysis
also showed reproducibility between cores C1 and C4 (Figure 21 and Appendix D). C1
and C4 deviations are likely due to differences in sampling interval between the two
cores. The cores were found to contain monohydrocalcite, calcite, ankerite, quartz and phillipsite (Figure 21). Although the diffractograms were examined, no other carbonate
phases (e.g., dolomite and magnesium calcite) or evaporite minerals (e.g., gypsum) were
found to be present. Between 302-341 cm, monohydrocalcite and calcite are nearly
42 MC/CR C/CR A/CR Q/CR P/CR Lithology
01010101 01 0 0
50 50
100 100
150 150 Depth (cm) 200 200 Depth (cm)
250 250
300 300
350 350
laminated, brown massive, brown bedded black, brown silt organic rich mud organic rich mud brown, white mud Figure 21. Semi-quantitative XRD mineralogy showing monohydrocalcite (MC), calcite (C), ankerite (A), quartz (Q), and phillipsite (P) ratios normalized by 25 weight percent corundum (CR) standard. Core 1 (red) and Core 4 (blue) mineralogy (note the high degree of similarity for the downcore variations between cores 1 and 4) plotted alongside core lithology. Arrows indicate locations with accompanying SEM data.
43 absent whereas ankerite and quartz are abundant (Figure 21). Between 252-302 cm,
monohydrocalcite and especially calcite become more abundant as the presence of
ankerite and quartz declines. Following a sharp ankerite increase and monohydrocalcite
and calcite decrease at 246 cm, the uppermost 236 cm of sediment is marked by the
increased presence of monohydrocalcite with minor calcite. In the upper 236 cm,
ankerite, quartz and phillipsite remain low with notable fluctuations at 120 and 185 cm
and a marked increase occurring at 89 cm (Figure 21).
An attempt was made to see if there was a relationship between the CaCO3% determined by coulometry (Peck et al., 2002) and the abundance of carbonates minerals found through XRD analysis (Figure 22). The graphical results indicated no direct relationship between the data sets. The lack of a direct relationship could be explained by the differences in sediment size used for each analysis and the XRD mineral identification technique. The CaCO3% was determined using the entire bulk sediment
whereas the XRD analysis was only carried out on the fine fraction (< 63 μm) bulk
sediment (Appendix D). In addition, the XRD mineral quantities were determined from
the diffractogram curve peak CPS for each mineral and not the total area under the curve.
4.1.4 SEM Data
Talbot and Kelts (1986) used SEM images to assess the carbonate mineralogy of
lacustrine sediment from Lake Bosumtwi, Ghana. They were able to identify primary
and diagenetic minerals through the crystal structures visible in the SEM images (Figure
23). Four Lake Telmen sediment samples were studied by SEM. SEM images (Figure
24) taken at either 5,680 x or 11,361 x magnification failed to reveal any specific crystal
44 50
45
40
35
3 30
25
% CaCO 20 Monohydrocalcite 45 15 Calcite Ankerite 10
5
0 0.0 0.5 1.0 1.5 CPS
Figure 22. The % CaCO3 (determined by coulometry) from the Telmen core is plotted against the monohydrocalcite, calcite and ankerite mineral peak counts per second (CPS) intensity. No relationship is present between the two data sets possibly because the % CaCO3 was measured on the bulk sediment and the XRD mineralogy measured on the fine-fraction sediment. In addition, the mineralogy data is based upon the XRD peak CPS value rather than a measurement of the area below the curve, which may possibly affect the XRD estimate of carbonate present.
Figure 23. SEM images from Lake Bosumtwi, Ghana. Images show how SEM of lacustrine carbonates can be used to indicate specific mineralogy through crystal structure. Images show (a) primary aragonite (1 μm scale) (b) primary calcite (10 μm scale) (c) diagenetic calcite spherulite (100 μm scale) (d) dolomite (1 μm scale) (Talbot and Kelts, 1986).
46
A B
C D
Figure 24. SEM images taken from four different Lake Telmen core depths. SEM images were unable to show crystal structure, possibly due to minute crystal size, however EDX data was collected. (A) Sample taken from 30 cm core depth from the upper lithologic zone. (B) Sample taken from 88 cm core depth from the interbedded massive layers within the upper zone. (C) Sample taken from 247 cm core depth from the middle bedded lithologic zone. (D) Sample taken from 336 cm core depth taken from the brown silt. Image shows centric diatom valve.
47 structures characteristic of carbonate phases. However, diatoms were visible in some
images from the deepest core sample. The EDX elemental data was collected across the
entire SEM image rather than a focused location since specific crystal structures were not
visible. Although the mineral structure is not evident from the SEM images, the EDX
scan indicates the presence and relative abundance of elements contained within the XRD
minerals that can be used to infer specific mineral presence (Figure 25).
4.1.5 Age Model
Eight bulk sediment samples were dated from Lake Telmen sediment cores C1
and C4 by Peck et al. (2002). The dates revealed a millennium-scale sample resolution
over the core length. Two surface samples yielded modern ages indicating the surface
sediment was recovered and little hard water effect is present (Table 5). The age model
revealed the 343 cm correlated core length spans 7,110 calendar years (Figure 26).
4.2 Lake Ugiy
The following subsections contain the lithologic, isotopic, mineralogic and radiocarbon age results from the Lake Ugiy sediment core.
4.2.1 Core Lithology
The Lake Ugiy core is a composite of six separate drives collected during a 1999
field expedition in Mongolia (Peck written communication, 2007). The total core depth is 374.8 cm and was collected from the deep central basin. The core has been divided into four main lithologic zones (Figure 27). The bottom zone consists of alternating light
48 A B
C D
Figure 25. EDX elemental scans (X-axis units are keV) from four different Lake Telmen core depths. Samples A-D correspond to Figure 24 samples A-D. The following XRD minerals contain the indicated elements: calcite and monohydrocalcite (Ca, C, O), ankerite (Ca, Fe, Mg, C, O), quartz (Si, O), phillipsite (Ca, Na, K, Al, Si, O). A) Scan dominated by monohydrocalcite and calcite with quartz, phillipsite and ankerite present. B) Scan dominated by quartz with ankerite, phillipsite, calcite and monohydrocalcite. C) Scan dominated by calcite and monohydrocalcite with ankerite and quartz. D) Scan dominated by ankerite with quartz, phillipsite, monohydrocalcite and calcite.
49 Table 5. Lake Telmen AMS radiocarbon age converted to calendar year (from Peck et al., 2002). Core Sample Corrected Core Sediment Radiocarbon Error Calibrated Age Name Depth (cm) Type Age (yr) (±yr) Maximum (yr) Minimum TN-99 G5 0-5cm 1 sediment humic acid 0 - 0 TN-99 G5 0-1cm 0.05 pollen 0 - 0 TN-99 C1S1 37-40 38.5 sediment humic acid 640 35 670 (650) 540 TN-99 C1S1 77-80 78.5 sediment humic acid 1250 40 1280 (1180) 1070 TN-99 C1S2 52-55 138.5 sediment humic acid 2380 30 2470 (2360) 2340 TN-99 C1S2 96-98 182 sediment humic acid 2930 90 3350 (3070) 2850 TN-99 C4S3 1-3 239 sediment humic acid 4100 35 4810 (4570) 4450 TN-99 C4S3 98-100 336 sediment humic acid 6090 70 7190 (6940) 6740 50
Calendar year 0 2000 4000 6000 8000 0
50
100
150
200
250 Core depth (cm) 300
350
400
Figure 26. Lake Telmen age model derived from AMS radiocarbon dates indicating the 3.5 m core spans approximately 7000 years (modified from Peck et al., 2002).
51 -3 WBD (g cm ) % CaCO3 Lithology
11.50 5 10 15 0 0
50 50
100 100
150 150
200 200 Depth (cm) Depth (cm)
250 250
300 300
350 350
black, gray, sandy gray organic mud gray clay gray sand light to dark brown mud with with organic clay with silty clay with black gastropods layers clay organic clay
Figure 27. Lake Ugiy Core 1 wet bulk density (WBD) plotted alongside % CaCO3 and core lithology on depth. The core can be divided into four main zones based on lithological characteristics. Some WBD shifts correlate strongly with lithology changes while others correspond to minor variations within the lithologic zone.
52 to dark brown clay with black organic clays from 335.5-374.8 cm. This zone also contains a gray sand layer from 350.8-353.3 cm. Next, alternating gray clay and silty
clays are found between 254.3-335.5 cm. Gray sand layers are interbedded within this
zone at 302-304, 315.8-317.8 and 332-335.5 cm. From 38-254.3 cm, the next zone consists of gray organic mud with organic clay layers. The upper zone is a black and
gray sandy, mud with gastropods and mollusks and high calcium carbonate content down
to 38 cm.
Figure 27 also shows the lithology plotted alongside WBD and % CaCO3 data
(Peck written communication). Below 215 cm generally higher WBD and % CaCO3
values characterize the core whereas lower WBD and % CaCO3 characterize the core
above 220 cm.
4.2.2 Carbonate Stable Isotope Analysis
As part of the Lake Ugiy pilot study, 12 sediment samples were prepared and sent
to the University of Pittsburgh Stable Isotope Laboratory and currently await mass
spectrometry analysis for carbonate stable isotope determination.
4.2.3 Mineralogy
Lake Ugiy mineralogy was determined using semi-quantitative XRD analysis.
The core contains calcite, Mg-calcite, albite, sodian anorthite, and quartz (Appendix E)
(Figure 28). As was also the case with the Lake Telmen mineralogy, no orundum
minerals (e.g., gypsum) were found to be present after examination of the diffractogram
from each Lake Ugiy sample. However, contrary to Lake Telmen, Lake Ugiy contained
53 -3 C/CR MgC/CR Alb/CR An/CR Q/CR WBD (g cm ) % CaCO 3 Lithology
00.5 00.5 012 012 11.5 0 5 10 15 0 0 00.5
50 50
100 100
150 150 Depth (cm) Depth (cm) 54 200 200
250 250
300 300
350 350
black, gray, sandy gray organic mud gray clay gray sand light to dark brown mud with with organic clay with silty clay with black gastropods layers clay organic clay
Figure 28. Semi-quantitative XRD mineralogy showing calcite ©, Mg-calcite (MgC), albite (Alb), sodian anorthite (An) and quartz (Q) ratios normalized by 25 weight percent orundum (CR) standard. Lake Ugiy core mineralogy alongside WBD, % CaCO3 and core lithology plotted on core depth. Note the x-axis scale change for An and Q due to relative abundance, especially in the lower core. magnesium calcite. Though the low resolution sampling provides little detail for analysis, some general trends are evident. Corresponding loosely to the lower two lithologic zones and the high WBD and carbonate content below 215 cm, the XRD analysis indicates relatively high abundance of albite, anorthite and quartz with calcite present and no Mg-calcite. Between about 38-215 cm WBD decreases, % CaCO3
decreases and the lithology has already changed to finer-grained sediment. XRD shows
Mg-calcite is present and calcite is absent. Albite, anorthite and quartz remain relatively
abundant. The top lithologic unit represents the 0-38 cm segment. This interval has the
lowest WBD and a sharp increase in % CaCO3 that corresponds to a reappearance of
calcite, disappearance of Mg calcite, and a decrease in albite, anorthite and quartz (Figure
28).
4.2.4 Age Model
The humic acid fraction of four bulk sediment samples were dated from Lake
Ugiy sediment core C1 (Peck written communication, 2007). The surface sample yielded a modern age indicating the surface sediment was recovered and little hard water effect is present (Table 6). The age model revealed the 374.5 cm core spans approximately 5,100 calendar years (Figure 29). However the middle two samples show age reversal. Though this age reversal makes the age model suspect, a linear trendline was fitted to the data to obtain an approximate age estimate for the core. In the absence of additional radiometric age control, this age model should be viewed with caution.
55
Table 6. Lake Ugiy AMS radiocarbon age converted to calendar year (Peck written communication, 2007). Core Sample Corrected Core Sediment Radiocarbon Error Calibrated Age Name Depth (cm) Type Age (yr) (±yr) Maximum (yr) Minimum UN99G7 0-1 0.5 sediment humic acid 0 - (0) UN99C1D2 59-62 162.5 sediment humic acid 2880 50 2947 (3026) 3105 UN99C1D4 35-39 289 sediment humic acid 2550 35 2556 (2645) 2734 UN99C1D6 20-23 363.5 sediment humic acid 4450 35 4996 (5117) 5238 56
Calendar year 0 2000 4000 6000 0
50
100
150
200
250 Core depth (cm) 300
350
400
Figure 29. Lake Ugiy age model derived from AMS radiocarbon dates indicating the 3.65 m core spans approximately 5100 years (modified from Peck et al., 2002)
57
CHAPTER V
DISCUSSION
5.1 Carbonate Stable Isotopes and Lacustrine Sediment Minerology as Paleoclimate
Indicators
Lacustrine sediments have been successfully used for carbonate stable isotope
analysis in studies to provide paleohydrological data, verifying the potential success of
this method as a paleoclimate interpretive tool (Rosenmeier et al., 2002; Leng, 2005). As
a body of water undergoes evaporation, the lighter 16O isotope will evaporate more readily than the heavier 18O isotope, resulting in the remaining lake water enriched in 18O
(Leng, 2005). Conversely, the heavier 18O will precipitate more readily than 16O, leaving
the remaining water vapor in the atmosphere isotopically lighter. Authigenic calcite
(CaCO3) precipitated within the body of water will reflect water isotope ratios at the time
of mineral precipitation and deposition (Leng, 2005). If a sediment layer from which the
authigenic carbonate sample came can be dated, then the isotopic composition of the lake
water and hence lake paleohydrology can be estimated. It is important to ensure the
carbonate sediment is authigenic. If detrital carbonate is present, then the isotopic
chemistry will not accurately reflect the past hydrologic conditions of the lake, but
instead the isotopic signature of the detrital carbonate rock formation (Talbot and Kelts,
1986; Li et al., 1995; Russel et al., 2003).
58 Because the use of carbonates as a paleoclimate interpretive tool is most successful if they were formed within the water column, Filippi et al. (1998) compared carbonate isotopic ratios from lake sediments to those from inflowing river sediment by using sediment traps to collect both lacustrine and adjacent river sediment. Although only allochthonus sediment is accurate for analyzing paleoenvironment, small amounts of detrital carbonate within the lacustrine sediment do not preclude accurate isotopic data.
However, Filippi et al. (1998) showed that even excessive detrital carbonate influence on the isotopic composition can be corrected for by using the lacustrine and river carbonate
ratios, and hence accurate paleoenvironmental information can still be reavealed.
Not only are the stable carbonate isotope ratios used to determine relative
moisture balance, but the covariance of δ18O and δ 13C from authigenic lacustrine carbonates can also be used to make determine past hydrologic conditions. On time scales greater than 5,000 yrs it was shown by Li and Ku (1997) that covariance of δ 18O and δ 13C data as, “a function of hydrological change, vapor exchange, lake productivity, and total CO2 (or carbonate alkalinity) concentration” indicate a hydrologically closed-
basin lake. On time scales less than 5000 yrs, closed-basin lakes may still have δ 18O and
δ 13C covariance, however the lack of isotopic covariance does not necessarily indicate
the lake is hydrologically open. The Lake Telmen carbonate isotope data fits well into
these criteria. Lake Telmen, a closed-basin lake, yielded a sediment core spanning
greater than 7,000 yrs and the lacustrine carbonate shows moderate δ 18O and δ 13C covariance (Figure 30). Closed-basin lakes can amplify small climatic forcing of the hydrologic balance into a larger lake water and sediment response (Peck et al., 2002).
59 3.50 Laminate mud R2 = 0.3378 Massive mud R2 = 0.4103 Bedded mud R2 = 0.6627 2 2.50 Brown silt R = 0.5462
Laminated mud
1.50 Massive mud
Bedded mud δ 13C 0.50 (‰) Brown silt
60 -0.50
-1.50 Combined R2 = 0.5136
-2.50 -6.00 -5.00 -4.00 -3.00 -2.00 -1.00 0.00 1.00 2.00 δ 18O (‰)
Figure 30. Crossplot showing the relationship between δ18O and δ13C by lithologic zone for all samples measured from cores C1 and C4. Data show the linear relationship, indicating covariance between the δ18O and δ13C isotopes for closed-basin Lake Telmen. Lacustrine sediment mineralogy may also be used as a paleoclimate indicator
because it can reveal information regarding sediment origin, weathering rates, and
environmental conditions at the time of deposition (Last, 2001). Lacustrine sediment has
a broad range of confounding factors that can make the interpretation of the paleoenvironmental signal difficult. These complicating factors include watershed geology, soil composition, thermodynamic equilibrium and the possible presence and effect of allogenic, diagenetic and authigenic minerals (Last, 2001). Mineralogy can be
an effective paleoenvironmental data source, however great care must be taken when analyzing lacustrine deposits as they are mineralogically more diverse than other continental or marine deposits (Last, 2001).
Li et al. (2008) have shown that lacustrine sediment can be used successfully to interpret paleoclimate by using XRD and SEM to assess the depositional history of the
Tibetan lake, Nam Co through sediment mineralogy. Their analysis indicated the sediment consists of multiple forms of carbonate, including monohydroclacite. This mineralogy data was used to determine physical and chemical water parameters of the water as well as biological presence. They found the monohydrocalcite in the core was associated with high lake pH and biological productivity, such as algae and diatoms. The clay minerals and other rock-forming minerals found in the sediment were associated with physical weathering and erosional input.
In addition to monohydrocalcite, the presence of other carbonate minerals can also provide useful paleoclimate information. Once it is determined that the carbonate lacustine sediment was deposited from within the water column and is predominantly authigenic, the presence of other carbonate mineral phases may indicate an environmental
61 change either induced the precipitation of a different carbonate phase or caused
secondary mineral alteration (Von der Borch et al., 1975; Tucker et al., 1990; Li et al.,
2008). Ankerite is a form of calcium carbonate containing varying amounts of
magnesium, iron and manganese, when found within lacustrine sediments indicates that
monohydrocalcite was possibly originally deposited but secondarily altered to ankerite
(Klein, 2002). This diagenetic change could be caused by a decrease in lake level
creating more saline waters and allowing for the lacustrine sediments to be exposed at or
near the surface and subject to groundwater interaction (Von der Borch et al., 1975; Li et al., 2008).
Non-carbonate minerals also have useful paleoclimate applications. In a
lacustrine sediment core, the mineralogical shift from predominantly authigenic carbonates to increasing amounts of terrigenous minerals such as quartz, anorthite or albite can indicate decreasing lake levels, possibly due to a decline in the moisture
balance. As the lake level decreases the lake shoreline advances toward the lake center,
increasing the terrigenous sediment influx by overland flow or stream flow into the lake.
5.2 Lake Telmen Paleoclimate Record
In this section, a discussion of the paleoclimatic interpretation of the Lake Telmen proxy data is presented first. Second, a discussion of the climatic forcing mechanisms likely to produce central Asian climate change is presented.
62 5.2.1 Holocene Climate Variability
Region-wide studies indicate that the Asian climate has fluctuated significantly
throughout the Holocene. Paleoclimate models and proxy data indicate wetter-than-
present conditions in China throughout the early-mid Holocene from approximately
10,000 to 5,000 yr B.P., and drier-than-present conditions dominating the later half of the
Holocene (Kutzbach and Ruddiman, 1993; Winkler and Wang, 1993; Hodell et al., 1999;
Wei and Gasse, 1999; Peng et al., 2005; Chen et al., 2008). Higher precipitation and
temperatures, that exceeded present temperatures by over 3 °C, occurred in some areas of
China during the early Holocene (Winkler and Wang, 1993). Models suggest
temperatures began to cool by around 4,000 yrs B.P., and the cooling trend has continued
to the present with periodic expansion of deserts and loess deposits, indicating increased
aridity (Winkler and Wang, 1993). This regional synthesis, based largely on data from
China, does not correspond with the paleoclimate interpretation of arid conditions prior to
4,390 yrs B.P., and wetter conditions since 4,390 yrs B.P. in Mongolia based on Lake
Telmen sediments (Peck et al., 2002). However, increased data collection from both
Northern China and Mongolia are leading to a higher resolution, more complex
interpretation of regional variation in central Asian paleoclimate (Tarasov et al., 1998;
Feng, 2001; Prokopenko et al., 2005; Wünnemann et al., 2006; Chen et al., 2008). These
studies indicate the importance of quantifying regional variability across central Asia.
Due to the large size of Central Asia, atmospheric and physiographic influences vary
throughout the region.
As interdisciplinary data collection within Mongolia increased during the 1990’s, so too did the understanding of central Asian paleoclimate variability. For example, the
63 interdisciplinary study of Lake Telmen sediments indicate a dry climate preceding 4,390
yr B.P. followed by a predominantly wet climate (Peck et al., 2002). Hyperarid conditions were present between 7,110 and 6,260 years B.P., with a decrease in aridity
between 6,260 and 4,390 yr B.P. Generally wetter-than-present conditions occurred
between 4,390 and 1,600 yr B.P., with the exception of two abrupt arid events identified
at 2,940-3,150 and 2,130-2,190 yrs B.P. in the palynology and lithology data (Peck et al.,
2002; Fowell et al., 2003). Diatom analysis supports this interpretation with a saline (20
ppt) lake prior to 6,230 yrs B.P. and fresher conditions since 4,000 yr B.P. (Soninkhishig
et al., 2003). The last 680 yrs are characterized by higher-than-present moisture
availability with a recent decreasing moisture trend (Peck et al., 2002). Tree ring studies
reveal that extreme droughts also occur intermittently throughout the last 400 (Pederson
et al., 2001).
This thesis research provides new carbonate stable isotope and mineralogy data
that confirms the complexity of central Asian paleoclimate. Between 7,110-4,500 yrs
B.P. the δ 18O and δ 13C values are more positive indicating more arid conditions than
present, in agreement with the published Lake Telmen proxy records (Figure 31). Since
4,500 years B.P., the δ 18O isotope values become more negative and remain so
throughout the majority of the late Holocene indicating a climatic shift to more humid
conditions. However, the isotopes also suggest subtle shifts to more arid climates at
approximately 2,800-3,100, 2,000-2,200 and 1,300-1,600 yrs B.P.
Figure 32 also shows the agreement between the various climate proxy records
from Lake Telmen including carbonate isotopes, pollen-inferred aridity, core lithology,
diatom-inferred salinity, and semi-quatitative quartz abundance. The core divides into
64 δ13C (‰) δ18O (‰) Aridity Index A/CR Salinity (‰) Lithology
-3 0 3 -6 -3 -1 0510 0101020 0 0
1 1
2 2
3 3 Age (kyr) Age Age (kyr) Age 4 4
5 5
6 6
7 7
laminated, brown massive, brown bedded black, brown silt organic rich mud organic rich mud brown, white mud
Figure 31. Carbonate stable isotopes, pollen-based aridity (Fowell et al., 2003), ankerite (A/CR) abundance, diatom-based salinity and lithology (Peck et al., 2002) for the 7,100 yr long Lake Telmen sediment core. The A/CR curve highlights the early Holocene aridity. Core 1 data in red and Core 4 data in blue.
65 δ13C (‰) δ18O (‰) Aridity Index Q/CR Salinity (‰) Lithology
-3 0 3 -6 -3 -1 0510 00.5 01020 0 0
1 1
2 2
3 3 Age (kyr) Age (kyr) Age 4 4
5 5
6 6
7 7
laminated, brown massive, brown bedded black, brown silt organic rich mud organic rich mud brown, white mud
Figure 32. Carbonate stable isotopes, pollen-based aridity (Fowell et al., 2003), quartz (Q/CR) abundance, salinity and lithology (Peck et al., 2002) for the 7,100 yr long Lake Telmen sediment core. The Q/CR curve highlights the early Holocene aridity as well as the 1,400 yr B.P. arid interval in the late Holocene. Core 1 data in red and Core 4 data in blue.
66 three main lithologic zones. The lowest zone is a massive brown silt zone which corresponds to heavier isotope values, high salinity and high quartz abundance all of which indicate an arid climate. The top of this zone is marked by a very sharp drop in isotope values from heavier to lighter and back to heavier (relative to present day values), marking the transition to the bedded black, brown and white mud dated to about 6,200 yrs B.P. Salinity and quartz ratios both show sharp increases at the 6,200 yr B.P. lithology transition, followed by the disappearance of diatoms (salinity) and gradual decrease in quartz abundance. Successive pollen-inferred aridity intervals also correspond with heavier isotopic values in this middle lithology zone. At the transition between the bedded zone and the laminated upper zone a sharp decrease to light isotopes occurs. The upper lithology zone consists of a laminated, brown, organic-rich mud with three interbedded massive, brown, organic-rich mud layers. The laminated zone corresponds to a transition to lighter isotopic values since 4,500 yrs B.P. as well as lower pollen-based aridity, quartz abundance and salinity (Figure 32). These data indicate that a relatively humid climate dominated the Lake Telmen region since 4,500 yr B.P., with the exception of three short arid intervals marked by the three massively interbedded zones.
The three interbedded massive layers found in the upper zone at 2,940-3,150,
2,130-2,190 and 1,300-1,600 yrs B.P correspond to slightly more positive isotopes, increased pollen-inferred aridity, increased quartz abundance and increased salinity, all supporting short-term increases in aridity (Figure 32). In Lake Telmen, at water depths greater than 22 m, laminated sediments are preserved (Peck et al., 2002). A well- developed thermocline occurs at about 11 m during the summer months and the bottom
67 waters are hypoxic (Figure 11) (Peck et al., 2002). These hypoxic conditions limit bioturbation and thus allow for the preservation of laminated sediment varves.
Conversely, seasonal differences in sedimentation in the sediment accumulating in water shallower than 22 m deep, is mixed by both wave-induced resuspension and bioturbation
(Peck et al., 2002). For these reasons, the massive intervals have been interpreted as times of increased aridity and shallower water depth (Peck et al., 2002; Fowell et al.,
2003).
XRD mineralogy also provides new evidence supporting previous Lake Telmen proxy data interpretations. The Lake Telmen core mineralogy predominantly consisted of monohydrocalcite, calcite, ankerite, quartz and phillipsite. According to Li et al.
(2008) the presence of primary authigenic carbonate minerals indicate alkaline waters
(high pH) possibly due to biological productivity and the CO2 drawdown. Whereas the presence of ankerite, a transition mineral in the calcite-dolomite sequence, indicates a diagenetic mineral alteration of calcite (Boggs, 2001). This diagenetic alteration may occur during periods of low lake level and sediment exposure to increased groundwater interaction with elevated Mg and Fe concentrations from surrounding weathered materials (Li et al., 2008). Phillipsite is also a diagenetic mineral and has been found in saline, alkaline lakes, often forming from diagenesis of volcanic glass (Hay, 1966) or diatom silica (Talbot, 1986). As a common rock-forming mineral, detrital quartz has a source from its surrounding weathered rocks within the lake watershed (Li et al., 2008).
The down-core mineralogical variations reveal that prior to 6,200 yrs B.P. arid conditions prevailed as indicated by the very low abundance of monohydrocalcite and calcite and high abundance of diagenetic ankerite and detrital quartz (Figure 33). This
68 MHC/CR C/CR A/CR Q/CR P/CR Lithology
0101010101 0 0
1 1
2 2
3 3 Age (kyr) Age Age (kyr) 4 4
5 5
6 6
7 7
laminated, brown massive, brown bedded black, brown silt organic rich mud organic rich mud brown, white mud
Figure 33. Semi-quantitative XRD mineralogy on age showing monohydrocalcite (MHC), calcite (C), ankerite (A), quartz (Q), and phillipsite (P) ratios normalized by 25 wt % corundum (CR) standard. Core 1 (red) and Core 4 (blue) mineralogy display a high degree of downcore similarity and are plotted alongside core lithology. Arrows indicate core locations with accompanying SEM data.
69 mineralogical data corresponds to the massive brown silt lithological zone and saline
diatom interval. At this time, the ankerite is inferred to form diagenentically in a small,
saline lake basin and the quartz could be windblown to the lake as nearby dunes were likely to be active during these arid conditions (Filippi et al., 1998). Large increases in monohydrocalcite and calcite along with a corresponding decrease in ankerite and quartz suggest that the arid conditions begin to wane from 6,200 to 5,000 yrs B.P. A pronounced decline in monohydrocalcite and calcite abundance and a rise in ankerite from 5,000-4,500 yrs B.P. indicate a brief return to arid conditions. This mineralogic- inferred return to arid conditions occurs at the top of the bedded black, brown, and white mud lithologic zone (Figure 33). The most recent 4,500 yrs B.P. are dominated by high monohydrocalcite and low ankerite abundances, representing relatively humid conditions and corresponding to the laminated brown, organic-rich mud lithologic zone. This late
Holocene humid interval, however, is interrupted by three short arid intervals inferred from increases in ankerite, quartz and phillipsite abundances at 2,800-3,100 yr B.P. and
1,400-1,600 yr B.P. and ankerite at 2,000-2,200 yr B.P. (Figure 33). Ankerite, quartz and phillipsite presence have been shown to indicate arid climatic conditions in other lake studies (Hay, 1966; Talbot and Kelts, 1986; Grosjean et al., 1997; Grosjean et al., 2001;
Li et al., 2008). These intervals correspond with three interbedded massive brown, organic-rich layers within the upper laminated zone dated at 2,940-3,150, 2,130-2,190 and 1,300-1,600 yrs B.P. (Peck et al., 2002).
70 5.2.2 Climate Forcing Mechanisms
Variations in both solar output and Earth’s orbit induce complex earth system responses through positive and negative feedbacks which influence Earth’s climate
(Ruddiman, 2006). Driven by orbital, global, regional and local geographic influences,
Earth’s climate is in constant flux. Quantifying these climate forcing mechanisms is necessary in order to understand past and future climate change.
Solar output variations include Schwabe (11 yr) (Storini et al., 2006), Hale (22 yr)
(Maris and Maris, 2005), Gleissberg (88 yr) (Peristykh and Damon, 2003) , Suess (170-
260 yr) (Ogurtsov et al., 2004) and Hallstatt (2,300 yr) (Tobias et al., 2004) cycles.
Earth’s orbit also has three distinct variations known as the Milankovitch cycles; eccentricity, obliquity and precession (Ruddiman, 2006). Aside from climate variability controlled by solar and orbital variation, regional geographic factors can be a significant influence, such as topography, ice sheet presence or proximity to a major body of water.
Regional climate factors can create a lag in climate response to external forcing mechanisms, making paleoclimate data interpretation more difficult.
Mongolia currently lies at a climatic convergence zone at the southern edge of
Siberian high pressure air masses, the northern edge of the East Asian monsoon and the convergence of the Westerlies driven across Mongolia from the North Atlantic (Figure 5)
(Herzschuh, 2006; Chen et al., 2008). These systems, as with all atmospheric circulation, are largely driven by variations in solar and orbital parameters and the land-sea distribution. The variation within these converging systems proves largely responsible for Mongolian Holocene climate variability.
71 The mechanisms driving Mongolia’s climate have been the topic of recent debate.
As Mongolia’s climate has historically been extrapolated from Russian and Chinese proxy data, it was often assumed it behaved climatologically the same. It was previously thought that the East Asian summer monsoon extended northward into Monogolia, controlling the summer climate and the Siberian high pressure airmass controlled the winter climate (Winkler and Wang, 1993). However, as paleoclimate proxy data collection has increased within Mongolia’s borders, a more complex picture of climate variability is emerging. The northern limit of the rainy summer monsoon does not extend into Mongolia and the proxy data indicates a climate asynchronous with China throughout most of the Holocene (Chen et al., 2008). Central Asian paleoclimate data suggest the climate was instead dominated by the Westerlies (Yang et al., 2003;
Vandenberghe et al., 2006; Chen et al., 2008).
In the northern hemisphere, the path of the Westerlies is largely influeneced by the North Atlantic and Arctic Oscillations (NAO and AO), which are yearly to multi- decadal fluctuations of the Icelandic low pressure system and the Azores high pressure system (Figure 34) (Hoerling et al., 2001; Kim et al., 2004). The combined effects of these oscillations are divided into a positive warm and a negative cold phase. During the negative phase, the North Atlantic has weaker atmospheric pressure gradient which results in weaker Westerlies, displaced further south (Figure 34). Flowing over a cooler ocean the Westerlies carry less moisture into the Mediterranean region. Additional orographic effects in central Asia may further limit the moisture delivered to the
Mongolia region. During the positive warm phase the North Atlantic has a stronger
72
Figure 34. Maps showing the influence of Arctic Oscillation (AO)/North Atlantic Oscillation (NAO) and North Atlantic sea surface temperature (SST) on the track of the northern latitude Westerly winds. (Left) During the positive warm phase NAO, the Westerlies track across the warm moist ocean air, carrying that moisture across Europe and into Mongolia. (Right) During negative cold phase, the high pressure system in the North Atlantic displaces the Westerlies. The Westerly wind tracks across cold dry ocean air which is then carried across northern Africa before reaching central Asia. The air mass brings less moisture into Mongolia (D’Areo, 2008).
73 pressure gradient, allowing stronger Westerlies to track more directly into Europe carrying warm, moist ocean air onto the continent.
During the early Holocene, with increased boreal summer solar insolation (Figure
35) (Paillard et al., 1996), the East Asian summer monsoon strengthened and drove the northern limit of the summer monsoon into southern Mongolia (Winkler and Wang,
1993). The early Holocene was characterized by more humid conditions throughout monsoonal China, as indicated by paleoclimate proxy data (An et al., 2000; Chen et al.,
2008). The majority of Mongolia however, lying north of the Asian monsoon limit, was not receiving the moisture increase from the East Asia monsoon. Mongolia’s summer climate during the early Holocene was dominated by the Westerlies which come from over the North Atlantic Ocean, across Europe and into Mongolia (Wang et al., 2004).
During the early Holocene, the remnants of the Laurentide ice sheet maintained low
North Atlantic sea surface temperatures (SST), causing decreased evaporation off the cold ocean waters (Carlson et al., 2008). Figure 34 shows a representation of how the track of the Westerlies may have looked during the early Holocene (corresponding to the negative cold phase) when the North Atlantic SST was cold (D’Areo, 2008). At this time, the colder Westerlies held less moisture and tracked far to the south into the
Mediterranean before moving into Asia. The cold North Atlantic conditions may have resulted in the arrival of dry air in Mongolia. The track of the Westerlies, combined with the influence of the cold, dry Siberian high pressure air mass, led to Mongolia’s arid early
Holocene climate (Peck et al., 2002; Peng et al., 2005; Chen et al., 2008), despite the increased solar insolation, causing humid conditions throughout China (Winkler and
Wang, 1993; Wei et al., 1999; Wang et al., 2002). By the mid-Holocene, approximately
74 June Insolation 18 2 Aridity δ O (‰) Aridity Index Q/CR Salinity (‰) 65°N (W/m ) Lithology 520 505 490 475 -6 -3 -1 0510 00.5 01020 0 0
1 1
2 2
3 3
4 4 (kyr) Age
5 5 Age (kyr) Age
6 6
7 7 ACA
8
Monsoon bedded black, brown silt 9 Asia laminated, brown massive, brown organic rich mud organic rich mud brown, white mud
10
Figure 35. Holocene climate records from Lake Telmen compared to summary climate reconstructions from Asia. More arid conditions plot to the right. Left column, summary climate reconstructions showing the asynchronous Holocene moisture evolution between arid central Asia (ACA) and monsoonal Asia (China) (modified from Chen et al., 2008). Lake Telmen oxygen isotopes (this study) , aridity (Fowell, et al., 2003), quartz (Q) abundance (this study), salinity (Soninkhishig et al., 2003); boreal summer insolation (Paillard et al., 1996), and lithology (Peck et al., 2002). Prior to 4,500 yr B.P., the Lake Telmen record indicates arid conditions even though insolation is high. During this time the effects of the cold N. Atlantic led to a dry central Asia. Central Asian moisture increases after 4,500 yr B.P. as the N. Atlantic warms and alters Westerly air.
75 5,000-8,000 yr B.P., Asian climate was influenced by the Holocene optimum, a warming
period in the northern hemisphere (An et al., 2000; Peng et al., 2005). The East Asian summer monsoon was strong during this time (Figure 4), creating a humid climate throughout China (Figure 6). By the end of the mid-Holocene, the central Asian climate
became more humid as a result of the diminished effects of the Laurentide ice sheet on
North Atlantic temperatures (Berner et al., 2008; Chen et al., 2008). Behaving similar to
the positive warm phase (Figure 34), the increased North Atlantic SST and stronger
atmospheric pressure gradient allowed direct passage of the stronger Westerly winds onto
the Eurasian continent. The warmer SST increased moisture availability through
evaporation. This moist ocean air was carried along the Westerly track across Europe
and into Mongolia from the west/northwest, causing the increased humidity recorded in
Mongolia’s lake sediments during the mid to late Holocene (Figure 6) (Kim et al., 2004;
Magny, 2004; Chen et al., 2008; D’Areo, 2008). The wanning of the Laurentide ice sheet
explains why there was a lag in central Asian humidity as boreal summer solar insolation
increased in the early Holocene (Figure 6) (Chen et al., 2008). However, by the late
Holocene the decreased solar insolation caused a weakening of the Asian monsoon as well as decreased East Pacific Ocean evaporation (An et al., 2000; Peng et al., 2005).
The weakening monsoon did not drive as far north into China as during the early
Holocene (Winkler and Wang, 1997) and resulted in a shift to a more arid climate in
China (An et al., 2000; Peng et al., 2005; An et al., 2006; Chen et al., 2008).
During the late Holocene there are several short-term periods of increased aridity in the otherwise relatively humid conditions in the Lake Telmen region. The two most intense aridity periods are at about 1,300-1,600 and 2,800-3,100 yrs B.P. and a less
76 pronounced period at 2,000-2,200 yr B.P. as indicated by the lithology, mineralogy and isotopes (Figure 36).
Deep sea cores were used by Bond et al. (1997) to analyze North Atlantic
Holocene climate variability. Within these cores they discovered evidence of ice-rafted debris (IRD) supported by three IRD proxies; concentration of lithic grains, volcanic glass and hematite-stained quartz and feldspar. Bond et al. (1997) identified millennial- scale IRD episodes occurring at 1,400, 2,800, 4,200, 5,900, 8,100, 9,400, 10,300, and
11,100 yrs B.P., often referred to as Bond cycles (Figure 36). The presence of IRD indicates North Atlantic iceberg events and cooler sea surface temperatures. Kim et al.
(2004) used alkenone derived SST records to show North Atlantic millennial scale variability over the last 7,000 years. The data shows cooling periods at roughly 1,400,
2,800, 4,500, and 5,500 yrs B.P. Cold North Atlantic temperatures are also supported by the increased presence of multiple cold water foraminifera species (Bond et al., 1997).
European lake records show low lake levels (aridity) distinctly correlate to Bond cycles
(Magny, 2004). The similarity in timing between Bond cycles and aridity recorded Lake
Telmen at 1,300-1,600 and 2,800-3,100 yr B.P. suggesting a possible role for cold North
Atlantic SST on the Westerly track and moisture supply to central Asia. As previously discussed, cold North Atlantic SST decreased moisture availability to the Westerlies
(Figure 34) (Wang et al., 2004; Carlson et al., 2008; Chen et al., 2008). Therefore, during these late Holocene IRD episodes, Mongolia, climatologically influenced by these winds, could experience arid conditions.
77 18 Calibrated Age δ13 C (‰) δ O (‰) Aridity Index A/CR Salinity (‰) Lithology Bond events Error (kyr) -6 -3 -1 0510 01 01020 0 0
-3 0 3 1 1 1.4 1.4
2 2 2.8 2.7
3 3 Age (kyr)Age Age (kyr)
4.3 4.1 78 4 4
5 5 5.9 5.8
6 6
laminated, brown massive, brown bedded black, brown silt 7 organic rich mud organic rich mud brown, white mud 7
Figure 36. Plot of select downcore Lake Telmen climate proxies and lithology are plotted on the calibrated radiocarbon age model. Core 1 (red) and Core 4 (blue) bulk carbonate, fine-fraction stable isotope data, the aridity index based on Fowell et al. (2003) pollen data, A/CR showing ratio of ankerite normalized to 25 weight percent corundum, salinity derived from diatom species from Peck et al. (2002). Gaps in the diatom salinity record occur in intervals lacking preserved diatoms in the core. Calibrated radiocarbon age was used to date the core and the samples associated errors are plotted. Plotted to the right is the core lithology. The age of Bond events taken from Bond et al. (1997) are tabulated to the far right in two columns showing cycle timing variation and marked with dashed lines across the figure.
The proxy records from this study support the Chen et al. (2008) hypothesis that central Asian climate was “out-of-phase” with the climate of China lying to the south.
Chen et al. (2008) compiled 21 paleoclimate proxy records from throughout Asia; 12 from central Asia and 9 from monsoonal Asia, with one of the central Asian sites being
Lake Telmen (Figures 5 and 6, Site 7). This compilation indicated central Asia experienced an arid early Holocene, a slightly less arid mid-Holocene, and a moderately moist late Holocene. Though the isotope and mineralogical record from this study does not date to the early Holocene, it does indicate arid conditions into the mid-Holocene and increasing humidity throughout most of the late Holocene. This study adds further support to the Chen et al. (2008) climate interpretation and reveals possible far reaching teleconnection between the North Atlantic and central Asia via the Westerly winds.
5.3 Lake Ugiy Pilot Study
Because proxy records collected from open lakes can be more difficult to interpret than closed-basin lakes, the Lake Ugiy analysis was limited to a pilot study. Although the radiometric age model, and XRD mineralogy are based on limited samples, this pilot study can be used to guide future in-depth study.
Prior to about 4,200 yr B.P., the presence of cm-thick sandy layers and abundant rock forming minerals, albite, anorthite and quartz suggest a shallower lake, where coarse-grained detrital sediment could more readily reach the core site (Figure 37). No sandy beds are present after 4,200 yr B.P., possibly indicating that a deeper lake with a more distant shoreline was present. Five samples between about 1,200 and 2,500 yr B.P. show the presence of Mg calcite. This mineral has been used in other lake studies to infer
79 -3 C/CR MgC/CR Alb/CR An/CR Q/CR WBD (g cm ) % CaCO3 Lithology
00.5 00.5 00.5 012 012 11.5 0 5 10 15 0 0
1 1
2 2 Age (kyr) Age (kyr) 3 3 80
4 4
5 5
black, gray, sandy gray organic mud gray clay gray sand light to dark brown mud with with organic clay with silty clay with black gastropods layers clay organic clay
Figure 37. Plot of semi-quantitative XRD mineralogy from Lake Ugiy plotted on age showing calcite (C), Mg-calcite (MgC), albite (Alb), sodian anorthite (An) and quartz (Q) ratios normalized by 25 wt % corundum (CR) standard. Lake Ugiy core mineralogy alongside core lithology also plotted on age. Note the different x-axis scales for An and Q due to their high abundances, as compared to calcite, Mg calcite and albite. The core can be divided into four main zones based on lithological characteristics. Some WBD shifts correlate strongly with lithology and mineralogy changes while others correspond to minor variations within a lithologic zone.
increased arid conditions (Talbot and Kelts, 1986; Russell and Johnson, 2005; Li et al.,
2008) formed in more saline waters (Boggs, 2001). The salinity of open-basin Lake
Ugiy, could be increased by either an increase in the precipitation/evaporation ratio or by
the temporary closure of the in and out flowing rivers by climatic or non-climatic
processes. Given the large uncertainties in the Lake Ugiy age model, it is possible that the approximately 1,200-2,500 yr B.P. arid interval in Lake Ugiy is related to the arid
events in Lake Telmen occurring at approximately 1,300-1,600, 2,000-2,200, and 2,800-
3,100 yr B.P. (Figure 37). In addition to the Lake Telmen record, Lakes Wulun, Boston,
Bayan and Gun (Figure 5, Sites 4, 5, 6 and 10) also display low lake levels between about
1,200 to 2,500 yr B.P. (Chen et al., 2008). This pilot study of Lake Ugiy suggests that a
future detailed study may aid in providing a more complete regional understanding of late
Holocene climate change in central Asia.
81
CHAPTER VI
SUMMARY
A Lake Telmen, Mongolia sediment core spanning the last 7,110 yr B.P. was measured for fine-fraction bulk carbonate stable isotope mass spectrometry and semi- quantitative XRD mineralogy to generate new paleoclimate proxy records. These new records were compared to existing Lake Telmen proxy datasets to assess
Holocene climate change.
These new datasets agree with prior (Peck et al., 2002) paleoclimate interpretation
based on pollen, diatoms and lithology, suggesting early Holocene aridity in the
Lake Telmen region of central Asia. Heavy oxygen isotope averages (δ18O -0.5
‰) and abundant ankerite, quartz and phillipsite mineral phases provide evidence
for increased aridity prior to 4,500 yr B.P. Since 4,500 yr B.P. the mid to late
Holocene is marked by pollen, diatom and lithologic data indicating more humid
conditions (Peck et al., 2002). The new carbonate isotope and XRD mineralogy
records support this climatic interpretation with lighter oxygen isotope value
averages (δ18O -1.2 ‰) and abundant monohydrocalcite and calcite.
These new Lake Telmen data further support the following Arid Central Asia
(ACA) climate hypothesis proposed by Chen et al. (2008). During the early
82 Holocene when boreal summer solar insolation was high, the East Asian monsoon
was strong and brought moisture into China. However, the waning presence of
Laurentide ice sheet not only effected the Westerly track by driving it farther
south into northern Africa and across the Middle East before reaching Mongolia,
but the cold North Atlantic air was very dry. Therefore, the Westerly system was
provided very little moisture and produced an arid central Asia. However, by the
mid-Holocene the Laurentide ice had melted, creating higher North Atlantic SST
and allowing for a more zonal Westerly track. Warmer moist ocean air was
carried across Europe and into Mongolia by the Westerlies increasing the
humidity in central Asia. The decreasing solar insolation during this time
decreased the strength of the East Asian summer monsoon, so as Mongolia was
becoming more humid in the late Holocene the opposite was true for China. This
influence from the North Atlantic accounts for the asynchronous Holocene
climate records of China and Mongolia.
The mid to late Holocene is also marked by short arid intervals (~1,300-1,600,
2,000-2,200 and 2,800-3,100 yrs B.P.) inferred by the presence of ankerite, quartz
and phillipsite. Pollen and lithological proxies also support an increase in aridiy
at this time (Peck et al., 2002). Within dating uncertainty, the arid intervals are
approximately correlative with cold North Atlantic SST (Bond cycles) suggesting
a possible role for the North Atlantic on central Asian climate.
83 In addition to the Lake Telmen study, a pilot study of a Lake Ugiy sediment core spanning the last 5,100 yr B.P. was undertaken. XRD mineralogy was determined at low resolution and samples were prepared for future mass spectrometry analysis.
Although limited, the XRD mineralogy variations coincide with major lithologic
boundaries and suggest more arid conditions prior to approximately 4,000 yr B.P.
and more humid conditions since 4,000 yr B.P.
84
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92
APPENDICES
93
APPENDIX A
LAKE TELMEN FINE-FRACTION (<63 μm) BULK CARBONATE STABLE
ISOTOPE STANDARDS NBS-18 AND NBS-19 DATA
94
Standard δ13C δ18O Acquisition Standard δ13C δ18O Acquisition ID (‰) (‰) Date ID (‰) (‰) Date NBS-18 -5.04 -23.06 05/17/07 17:49 NBS-19 2.01 -2.08 12/15/06 00:00 NBS-18 -5.00 -22.92 05/17/07 18:24 NBS-19 2.00 -2.11 12/15/06 00:00 NBS-18 -4.96 -23.01 05/17/07 19:00 NBS-19 1.91 -2.20 12/15/06 00:00 NBS-18 -5.04 -23.00 05/18/07 05:04 NBS-19 1.93 -2.25 12/15/06 00:00 NBS-18 -5.09 -22.90 05/30/07 02:40 NBS-19 1.92 -2.27 12/15/06 00:00 NBS-18 -5.07 -22.97 05/30/07 03:16 NBS-19 1.93 -2.29 12/15/06 00:00 NBS-18 -5.04 -23.02 05/30/07 03:51 NBS-19 1.91 -2.19 05/17/07 16:05 NBS-18 -4.93 -23.12 05/30/07 14:33 NBS-19 2.03 -2.25 05/17/07 16:36 NBS-18 -4.91 -23.00 05/31/07 03:44 NBS-19 1.88 -2.15 05/17/07 17:12 NBS-18 -5.04 -23.18 09/03/07 19:53 NBS-19 1.96 -2.20 05/18/07 04:26 NBS-18 -5.05 -23.04 09/03/07 20:28 NBS-19 2.00 -1.98 05/30/07 00:55 NBS-18 -5.01 -22.96 09/03/07 21:04 NBS-19 1.87 -2.35 05/30/07 01:28 NBS-18 -4.80 -22.64 09/04/07 11:55 NBS-19 1.97 -2.27 05/30/07 02:04 NBS-18 -5.08 -23.09 09/05/07 04:33 NBS-19 2.10 -2.23 05/30/07 14:00 NBS-18 -5.07 -23.07 09/05/07 11:09 NBS-19 1.78 -2.19 05/31/07 03:10 NBS-18 -5.01 -22.96 09/05/07 12:45 NBS-19 1.86 -2.33 09/03/07 17:56 NBS-18 -4.97 -22.98 09/05/07 13:12 NBS-19 1.89 -2.23 09/03/07 18:44 NBS-18 -5.01 -23.05 09/05/07 13:49 NBS-19 2.07 -2.07 09/03/07 19:19 NBS-18 -5.04 -23.04 09/05/07 14:24 NBS-19 2.00 -2.19 09/04/07 11:19 NBS-18 -5.09 -23.05 09/07/07 16:31 NBS-19 1.93 -2.19 09/05/07 03:54 NBS-18 -5.02 -22.89 09/07/07 17:04 NBS-19 1.80 -2.18 09/07/07 13:31 NBS-18 -4.92 -22.72 09/07/07 17:39 NBS-19 2.01 -2.14 09/07/07 14:06 NBS-18 -5.04 -22.99 09/07/07 18:14 NBS-19 1.97 -2.14 09/07/07 14:42 NBS-18 -5.08 -23.12 09/07/07 18:50 NBS-19 2.01 -2.21 09/07/07 15:18 NBS-18 -4.95 -23.05 09/08/07 07:25 NBS-19 1.92 -2.30 09/07/07 15:53 NBS-18 -4.94 -23.16 09/09/07 00:06 NBS-19 1.93 -2.23 09/08/07 06:50 NBS-18 -5.06 -22.97 09/11/07 13:19 NBS-19 2.02 -2.21 09/08/07 23:32 NBS-18 -5.04 -23.07 09/11/07 13:51 NBS-19 1.92 -2.25 09/11/07 15:32 NBS-18 -5.08 -22.96 09/11/07 14:23 NBS-19 1.89 -2.22 09/11/07 16:09 NBS-18 -5.10 -22.97 09/11/07 14:58 NBS-19 2.02 -2.19 09/11/07 16:42 NBS-18 -4.78 -22.91 09/12/07 03:27 NBS-19 1.94 -2.20 09/11/07 17:17 NBS-18 -4.97 -23.11 09/12/07 19:44 NBS-19 1.97 -2.13 09/12/07 04:00 NBS-18 -5.06 -23.00 09/26/07 23:17 NBS-19 1.95 -2.22 09/12/07 20:16 NBS-18 -5.05 -22.99 09/26/07 23:51 NBS-19 1.91 -2.28 09/25/07 19:36 NBS-18 -4.91 -22.99 09/27/07 00:27 NBS-19 1.84 -2.23 09/25/07 20:10 NBS-18 -5.02 -23.02 09/27/07 01:01 NBS-19 1.99 -2.07 09/25/07 20:45 Average -5.01 -23.00 NBS-19 1.98 -2.24 09/26/07 12:28 Std. Dev. 0.08 0.11 NBS-19 2.03 -2.17 09/26/07 19:26 Average 1.95 -2.20 Std. Dev. 0.07 0.08
95
APPENDIX B
LAKE TELMEN FINE-FRACTION (<63 μm) BULK CARBONATE STABLE
ISOTOPE CORES C1 AND C4 DATA
96 Lake Sample Correlated Cal. Age δ13C δ18O Acquisition ID Core Section Interval (cm) Depth (cm) (kyr) (‰) (‰) Date TN99 C1 S1 0-1 0.0 0.000 1.95 -1.06 09/04/07 20:50 TN99 C1 S1 5-6 5.0 0.093 2.23 -0.77 09/04/07 21:25 TN99 C1 S1 10-11 10.0 0.177 2.29 -0.21 09/04/07 22:03 TN99 C1 S1 12-13 12.0 0.203 2.18 -0.93 12/15/06 00:00 TN99 C1 S1 15-16 15.0 0.262 2.04 -0.66 09/04/07 22:36 TN99 C1 S1 20-21 20.0 0.346 2.11 -0.62 N/A TN99 C1 S1 22-23 22.0 0.371 2.25 -0.94 05/30/07 10:32 TN99 C1 S1 25-26 25.0 0.431 2.61 -0.22 N/A TN99 C1 S1 30-31 30.0 0.515 2.25 -0.69 09/05/07 00:24 TN99 C1 S1 32-33 32.0 0.540 1.95 -1.22 N/A TN99 C1 S1 35-36 35.0 0.599 1.95 -1.04 09/05/07 01:02 TN99 C1 S1 40-41 40.0 0.677 2.52 -0.69 N/A TN99 C1 S1 42-43 42.0 0.696 2.40 -1.09 05/30/07 05:03 TN99 C1 S1 45-46 45.0 0.743 2.50 -0.71 09/05/07 02:11 TN99 C1 S1 50-51 50.0 0.809 2.54 -0.35 09/05/07 02:46 TN99 C1 S1 52-53 52.0 0.829 2.50 -1.08 05/17/07 23:09 TN99 C1 S1 55-56 55.0 0.875 2.39 -1.00 N/A TN99 C1 S1 60-61 60.0 0.942 2.37 -1.19 09/11/07 20:27 TN99 C1 S1 62-63 62.0 0.961 2.62 -0.47 05/30/07 11:32 TN99 C1 S1 65-66 65.0 1.008 2.35 -0.56 09/11/07 21:02 TN99 C1 S1 70-71 70.0 1.074 2.45 -1.21 09/11/07 21:36 TN99 C1 S1 72-73 72.0 1.094 2.45 -1.51 05/18/07 01:32 TN99 C1 S1 75-76 75.0 1.140 2.45 -1.21 09/07/07 19:25 TN99 C1 S1 80-81 80.0 1.219 2.66 -0.45 N/A TN99 C1 S1 82-83 82.0 1.249 2.67 -0.82 N/A TN99 C1 S2 0-1 83.0 1.268 2.47 -0.72 09/03/07 22:51 TN99 C1 S2 5-6 88.0 1.367 1.86 -1.03 09/03/07 23:27 TN99 C1 S2 9-10 92.0 1.445 0.88 -0.98 09/04/07 00:02 TN99 C1 S2 14.5-15 97.0 1.544 1.93 -1.57 09/04/07 00:37 TN99 C1 S2 19.5-20 102.0 1.642 2.31 -0.82 09/04/07 01:13 TN99 C1 S2 25-26 108.0 1.760 1.96 -1.38 N/A TN99 C1 S2 35-36 118.0 1.957 1.87 -0.71 09/04/07 02:24 TN99 C1 S2 45-46 128.0 2.153 2.58 0.01 09/04/07 03:00 TN99 C1 S2 55-56 138.0 2.350 2.36 -0.59 09/04/07 03:37 TN99 C1 S2 65-66 148.0 2.515 1.95 -1.23 09/04/07 04:12 TN99 C1 S2 75-76 158.0 2.678 1.59 -1.19 N/A TN99 C1 S2 85-86 168.0 2.841 1.45 -2.62 N/A TN99 C1 S2 90-91 173.0 2.923 2.02 -0.84 N/A TN99 C1 S2 95-96 178.0 3.005 1.94 -0.33 09/04/07 07:10 TN99 C1 S2 99-100 182.0 3.072 0.96 -1.82 09/26/07 17:37 TN99 C4 S1 0-1 0.0 0.000 1.72 -1.51 12/15/06 00:00 TN99 C4 S1 10-11 10.0 0.181 1.83 -1.88 05/30/07 04:27 TN99 C4 S1 20-21 23.2 0.403 2.40 -1.00 05/30/07 12:15 TN99 C4 S1 30-31 36.4 0.626 2.18 -1.40 12/15/06 00:00 TN99 C4 S1 39-40 48.3 0.789 1.10 -1.30 05/17/07 21:58 TN99 C4 S1 40-41 49.6 0.806 2.52 -1.18 05/18/07 03:51 TN99 C4 S1 50-51 62.8 0.981 2.47 -0.83 05/30/07 12:48 TN99 C4 S1 60-61 76.0 1.156 2.16 -1.73 12/15/06 00:00 TN99 C4 S1 70-71 89.2 1.404 2.35 -1.02 05/30/07 13:24 TN99 C4 S1 75-76 95.8 1.534 0.76 -2.45 05/17/07 20:11 TN99 C4 S1 80-81 102.1 1.653 1.96 -1.74 N/A
97 Lake Sample Correlated Cal. Age δ13C δ18O Acquisition ID Core Section Interval (cm) Depth (cm) (kyr) (‰) (‰) Date TN99 C4 S1 90-91 111.5 1.843 2.18 -1.23 12/15/06 00:00 TN99 C4 S1 100-101 120.8 2.012 1.72 -1.35 05/18/07 00:56 TN99 C4 S1 109-110 128.4 2.177 2.12 -1.84 12/15/06 00:00 TN99 C4 S2 9-10 138.5 2.367 2.04 -0.84 12/15/06 00:00 TN99 C4 S2 19-20 147.3 2.512 2.23 -0.64 12/15/06 00:00 TN99 C4 S2 29-30 156.2 2.656 1.79 -1.58 05/30/07 07:27 TN99 C4 S2 39-40 165.2 2.803 1.61 -1.05 05/18/07 02:37 TN99 C4 S2 49-50 175.1 2.966 2.24 -0.99 12/15/06 00:00 TN99 C4 S2 54-55 180.1 3.045 1.96 -0.91 05/30/07 06:18 TN99 C4 S2 59-60 185.0 3.162 1.26 -1.91 05/30/07 08:03 TN99 C4 S2 64-65 190.0 3.294 1.99 -0.70 09/04/07 17:16 TN99 C4 S2 69-70 195.0 3.425 1.94 -0.83 12/15/06 00:00 TN99 C4 S2 74-75 200.0 3.557 2.38 -1.07 N/A TN99 C4 S2 79-80 205.0 3.688 2.57 -0.73 05/30/07 05:39 TN99 C4 S2 84-85 210.0 3.820 2.77 -0.63 09/04/07 18:30 TN99 C4 S2 89-90 215.0 3.952 2.07 -0.64 12/15/06 00:00 TN99 C4 S2 94-95 220.0 4.083 1.75 -1.04 09/04/07 19:03 TN99 C4 S2 99-100 225.0 4.215 1.41 -1.14 05/17/07 20:46 TN99 C4 S2 104-105 230.0 4.346 1.54 -1.53 N/A TN99 C4 S2 109-110 235.0 4.478 1.13 -0.77 05/17/07 23:47 TN99 C4 S2 110-111 236.0 4.504 -2.26 -5.70 N/A TN99 C4 S3 4-5 241.0 4.631 2.30 -0.48 N/A TN99 C4 S3 9-10 246.0 4.753 1.46 1.24 12/15/06 00:00 TN99 C4 S3 10-11 247.0 4.778 2.80 1.34 09/04/07 09:00 TN99 C4 S3 15-16 252.0 4.900 2.44 -0.18 09/04/07 09:36 TN99 C4 S3 19-20 256.0 4.998 2.43 -0.58 05/30/07 11:05 TN99 C4 S3 25-26 262.0 5.144 2.60 -0.43 N/A TN99 C4 S3 29-30 266.0 5.242 1.86 -0.80 12/15/06 00:00 TN99 C4 S3 34-35 271.0 5.364 2.46 -0.63 09/04/07 10:46 TN99 C4 S3 38-39 275.0 5.462 1.94 -0.50 09/04/07 12:30 TN99 C4 S3 44-45 282.0 5.633 2.96 -1.34 09/04/07 13:09 TN99 C4 S3 48-49 285.0 5.706 2.30 0.12 N/A TN99 C4 S3 51-52 288.0 5.779 3.49 -0.88 N/A TN99 C4 S3 54-55 291.0 5.853 2.33 -0.51 09/04/07 14:20 TN99 C4 S3 59-60 296.0 5.975 1.21 -0.85 05/17/07 19:36 TN99 C4 S3 63-64 300.0 6.073 2.07 -0.31 12/15/06 00:00 TN99 C4 S3 65-66 302.0 6.121 0.49 -1.98 09/04/07 14:58 TN99 C4 S3 69-70 306.0 6.219 -0.79 -3.90 05/30/07 06:53 TN99 C4 S3 74-75 311.0 6.341 1.47 -0.92 09/04/07 15:31 TN99 C4 S3 79-80 316.0 6.463 1.37 -0.71 12/15/06 00:00 TN99 C4 S3 85-86 321.0 6.586 1.16 -1.86 09/04/07 16:07 TN99 C4 S3 89-90 326.0 6.708 1.18 -1.56 05/17/07 21:23 TN99 C4 S3 95-96 331.0 6.830 1.80 -1.88 N/A TN99 C4 S3 99-100 336.0 6.952 2.44 0.53 05/17/07 22:34 TN99 C4 S3 104-105 341.0 7.074 2.29 -0.47 12/15/06 00:00
98
APPENDIX C
LAKE TELMEN FINE-FRACTION (<63 μm) BULK CARBONATE STABLE
ISOTOPE REPLICATE DATA
99 Lake Sample Correlated Cal. Age δ13C δ18O Acquisition ID Core Section Interval (cm) Depth (cm) (kyr) (‰) (‰) Date TN99 C1 S1 20-21 20.0 0.346 2.45 2.09 09/04/07 23:12 TN99 C1 S1 20-21 20.0 0.346 1.82 -1.03 09/11/07 18:27 TN99 C1 S1 20-21 20.0 0.346 2.06 -0.21 09/26/07 13:40 TN99 C1 S1 25-26 25.0 0.431 3.30 4.30 09/04/07 23:50 TN99 C1 S1 25-26 25.0 0.431 2.24 -0.36 09/11/07 19:15 TN99 C1 S1 25-26 25.0 0.431 2.31 -0.08 09/26/07 14:16 TN99 C1 S1 32-33 32.0 0.540 1.91 -1.36 05/18/07 00:23 TN99 C1 S1 32-33 32.0 0.540 1.98 -1.07 05/30/07 09:17 TN99 C1 S1 40-41 40.0 0.677 2.87 1.65 09/05/07 01:35 TN99 C1 S1 40-41 40.0 0.677 2.32 -0.72 09/11/07 19:50 TN99 C1 S1 40-41 40.0 0.677 2.36 -0.66 09/26/07 14:51 TN99 C1 S1 55-56 55.0 0.875 2.30 -1.32 09/05/07 03:23 TN99 C1 S1 55-56 55.0 0.875 2.48 -0.68 09/26/07 15:27 TN99 C1 S1 80-81 80.0 1.219 2.87 2.12 09/03/07 21:39 TN99 C1 S1 80-81 80.0 1.219 2.54 -0.59 09/07/07 20:01 TN99 C1 S1 80-81 80.0 1.219 2.56 -0.30 09/26/07 15:51 TN99 C1 S1 82-83 82.0 1.249 2.94 0.84 09/03/07 22:18 TN99 C1 S1 82-83 82.0 1.249 2.50 -0.93 09/07/07 20:36 TN99 C1 S1 82-83 82.0 1.249 2.57 -0.71 09/26/07 16:28 TN99 C1 S2 25-26 108.0 1.760 1.93 -1.35 09/04/07 01:49 TN99 C1 S2 25-26 108.0 1.760 1.99 -1.40 09/07/07 22:24 TN99 C1 S2 75-76 158.0 2.678 1.66 -0.97 09/04/07 04:48 TN99 C1 S2 75-76 158.0 2.678 1.51 -1.41 09/07/07 23:00 TN99 C1 S2 85-86 168.0 2.841 1.48 -2.66 09/04/07 05:23 TN99 C1 S2 85-86 168.0 2.841 1.42 -2.58 09/11/07 22:09 TN99 C1 S2 90-91 173.0 2.923 2.09 0.29 09/04/07 06:02 TN99 C1 S2 90-91 173.0 2.923 2.06 -0.39 09/04/07 06:35 TN99 C1 S2 90-91 173.0 2.923 1.91 -1.29 09/26/07 17:04 TN99 C4 S1 80-81 102.1 1.653 1.96 -1.57 05/18/07 03:15 TN99 C4 S1 80-81 102.1 1.653 1.95 -1.90 05/30/07 08:42 TN99 C4 S2 74-75 200.0 3.557 2.36 -1.02 09/04/07 17:54 TN99 C4 S2 74-75 200.0 3.557 2.40 -1.12 09/07/07 21:12 TN99 C4 S2 104-105 230.0 4.346 1.64 -1.42 09/04/07 19:39 TN99 C4 S2 104-105 230.0 4.346 1.43 -1.64 09/07/07 21:47 TN99 C4 S2 110-111 236.0 4.504 -2.29 -5.65 09/04/07 20:14 TN99 C4 S2 110-111 236.0 4.504 -2.24 -5.75 09/11/07 22:49 TN99 C4 S3 4-5 241.0 4.631 2.34 -0.40 09/04/07 08:12 TN99 C4 S3 4-5 241.0 4.631 2.26 -0.55 09/26/07 18:15 TN99 C4 S3 25-26 262.0 5.144 2.53 -0.25 09/04/07 10:10 TN99 C4 S3 25-26 262.0 5.144 2.66 -0.61 09/07/07 23:36 TN99 C4 S3 48-49 285.0 5.706 2.38 0.39 05/18/07 02:07 TN99 C4 S3 48-49 285.0 5.706 2.22 -0.15 05/30/07 09:51 TN99 C4 S3 51-52 288.0 5.779 3.51 -0.91 09/04/07 13:44 TN99 C4 S3 51-52 288.0 5.779 3.46 -0.84 09/11/07 23:21 TN99 C4 S3 95-96 331.0 6.830 2.98 2.44 09/04/07 16:40 TN99 C4 S3 95-96 331.0 6.830 1.19 -1.96 09/11/07 23:56 TN99 C4 S3 95-96 331.0 6.830 1.24 -1.80 09/26/07 18:53
100
APPENDIX D
LAKE TELMEN X-RAY POWDER DIFFRACTOMETER MINERALOGY DATA
CPS-COUNTS PER SECOND
101 Sample Monohydro- CPS corrundum CPS corrundum CPS corrundum Lake Interval Correlated Age calcite half CPS peak Calcite half CPS peak Ankerite half CPS peak ID Core Section (cm) Depth (kyr) 2 theta d value peak peak ratio 2 theta d value peak peak ratio 2 theta d value peak peak ratio TN99 C1 S1 0-1 0 0.000 20.503 4.328 439 931 0.6717 29.399 3.036 215 389 0.2810 30.678 2.912 192 352 0.2540 TN99 C1 S1 5-6 5 0.093 20.505 4.328 584 1206 0.8758 29.405 3.035 221 369 0.2680 30.676 2.912 203 358 0.2600 TN99 C1 S1 10-11 10 0.177 20.524 4.324 514 997 0.8329 29.445 3.031 228 408 0.3409 30.718 2.908 221 393 0.3283 TN99 C1 S1 12-13 12 0.203 20.517 4.325 479 974 0.8192 29.430 3.032 214 370 0.3112 30.701 2.910 223 404 0.3398 TN99 C1 S1 15-16 15 0.262 20.499 4.329 494 1024 0.7829 29.397 3.036 236 421 0.3219 30.680 2.912 204 384 0.2936 TN99 C1 S1 20-21 20 0.346 20.507 4.327 453 899 0.6552 29.410 3.035 224 373 0.2719 30.746 2.906 213 342 0.2493 TN99 C1 S1 22-23 22 0.371 20.518 4.325 510 997 0.8172 29.447 3.031 215 345 0.2828 30.696 2.910 181 331 0.2713 TN99 C1 S1 25-26 25 0.431 20.499 4.329 442 873 0.7348 29.410 3.034 223 368 0.3098 30.649 2.915 225 327 0.2753 TN99 C1 S1 30-31 30 0.515 20.550 4.318 698 1304 1.2085 29.448 3.031 253 424 0.3930 30.691 2.911 175 264 0.2447 TN99 C1 S1 32-33 32 0.540 20.496 4.330 487 1016 0.8102 29.413 3.034 231 389 0.3102 30.365 2.915 170 273 0.2177 TN99 C1 S1 35-36 35 0.599 20.518 4.325 506 1005 0.7827 29.425 3.033 247 449 0.3497 30.680 2.912 151 246 0.1916 TN99 C1 S1 40-41 40 0.677 20.514 4.326 575 1210 1.1298 29.402 3.035 209 384 0.3585 30.660 2.914 151 272 0.2540 TN99 C1 S1 42-43 42 0.696 20.524 4.324 570 1197 0.9669 29.403 3.035 226 376 0.3037 30.680 2.912 152 263 0.2124 TN99 C1 S1 45-46 45 0.743 20.512 4.326 694 1482 1.0833 29.372 3.038 238 501 0.3662 30.672 2.912 125 237 0.1732 TN99 C1 S1 50-51 50 0.809 20.522 4.324 531 1109 0.8414 29.401 3.035 219 389 0.2951 30.679 2.912 169 275 0.2086 TN99 C1 S1 52-53 52 0.829 20.518 4.325 590 1269 1.0032 29.410 3.034 216 389 0.3075 30.670 0.913 148 270 0.2134 TN99 C1 S1 55-56 55 0.875 20.524 4.324 593 1242 0.9026 29.408 3.035 224 421 0.3060 30.652 2.914 140 234 0.1701
102 TN99 C1 S1 60-61 60 0.942 20.522 4.324 619 1279 0.9559 29.387 3.037 227 441 0.3296 30.665 2.913 124 210 0.1570 TN99 C1 S1 62-63 62 0.961 20.526 4.323 598 1238 0.9494 29.408 3.035 202 358 0.2745 30.652 2.914 140 244 0.1871 TN99 C1 S1 65-66 65 1.008 20.522 4.324 659 1338 1.1141 29.401 3.035 211 404 0.3364 30.655 2.914 129 201 0.1674 TN99 C1 S1 70-71 70 1.074 20.511 4.327 510 1044 0.8068 29.395 3.036 227 361 0.2790 30.646 2.915 125 172 0.1329 TN99 C1 S1 72-73 72 1.094 20.525 4.324 669 1344 1.0275 29.368 3.039 218 405 0.3096 30.683 2.911 110 178 0.1361 TN99 C1 S1 75-76 75 1.140 20.499 4.329 561 1151 0.8275 29.362 3.039 219 397 0.2854 30.683 2.911 118 182 0.1308 TN99 C1 S1 80-81 80 1.219 20.503 4.328 560 1126 0.8944 29.341 3.041 218 408 0.3241 30.645 2.915 116 174 0.1382 TN99 C1 S1 82-83 82 1.249 20.496 4.330 565 1126 0.8901 29.334 3.042 204 409 0.3233 30.641 2.915 120 174 0.1375 TN99 C1 S2 0-1 83 1.268 20.516 4.325 607 1159 0.9400 29.374 3.038 205 377 0.3058 30.673 2.912 104 159 0.1290 TN99 C1 S2 5-6 88 1.367 20.487 4.332 462 831 0.6437 29.384 3.037 310 471 0.3648 30.638 2.916 121 174 0.1348 TN99 C1 S2 9-10 92 1.445 20.539 4.321 303 510 0.3941 29.476 3.028 339 585 0.4521 0.000 0.000 0 0 0.0000 TN99 C1 S2 14.5-15 97 1.544 20.533 4.322 639 1348 1.0228 29.422 3.033 242 412 0.3126 30.680 2.912 106 161 0.1222 TN99 C1 S2 19.5-20 102 1.642 20.531 4.322 719 1500 1.3228 29.383 3.037 224 420 0.3704 30.651 2.914 105 156 0.1376 TN99 C1 S2 25-26 108 1.760 20.516 4.325 585 1304 0.9746 29.378 3.038 221 429 0.3206 30.668 2.913 112 169 0.1263 TN99 C1 S2 35-36 118 1.957 20.503 4.328 334 556 0.5356 29.473 3.028 252 380 0.3661 30.563 2.923 316 524 0.5048 TN99 C1 S2 45-46 128 2.153 20.527 4.323 541 1063 0.6450 29.440 3.031 252 397 0.2409 30.701 2.910 283 517 0.3137 TN99 C1 S2 55-56 138 2.350 20.470 4.335 411 797 0.7421 29.383 3.037 230 396 0.3687 30.592 2.920 147 210 0.1955 TN99 C1 S2 65-66 148 2.515 20.529 4.323 586 1168 0.8397 29.433 3.032 238 428 0.3077 30.637 2.916 110 152 0.1093 TN99 C1 S2 75-76 158 2.678 20.526 4.323 384 756 0.7383 29.476 3.028 266 376 0.3672 30.703 2.910 167 207 0.2021 TN99 C1 S2 85-86 168 2.841 20.538 4.321 634 1323 0.9297 29.428 3.033 269 472 0.3317 30.723 2.908 101 149 0.1047 TN99 C1 S2 90-91 173 2.923 20.527 4.323 527 1075 0.7858 29.405 3.035 255 466 0.3406 30.643 2.915 167 243 0.1776 TN99 C1 S2 95-96 178 3.005 20.515 4.326 570 1294 0.9923 29.384 3.037 248 442 0.3390 30.607 2.919 142 216 0.1656 TN99 C1 S2 99-100 182 3.072 20.545 4.319 448 912 0.6338 29.478 3.028 240 428 0.2974 30.657 2.914 140 210 0.1459 TN99 C4 S1 0-1 0 0.000 20.528 4.323 442 857 0.6845 29.408 3.035 260 420 0.3355 30.703 2.910 192 302 0.2412 TN99 C4 S1 10-11 10.04 0.181 20.518 4.325 518 1009 0.7116 29.450 3.030 255 453 0.3195 30.661 2.913 187 265 0.1869 TN99 C4 S1 20-21 23.2361 0.403 20.520 4.325 614 1274 0.9055 29.409 3.035 233 414 0.2942 30.690 2.911 184 246 0.1748 TN99 C4 S1 30-31 36.4333 0.626 20.297 4.372 483 993 0.7674 29.180 3.058 245 441 0.3408 30.430 2.935 145 223 0.1723 TN99 C4 S1 39-40 48.3109 0.789 20.537 4.321 566 1261 0.8340 29.422 3.033 494 986 0.6521 30.641 2.915 102 164 0.1085 TN99 C4 S1 40-41 49.6306 0.806 20.504 4.328 560 1143 0.9338 29.369 3.039 285 472 0.3856 30.630 2.916 174 244 0.1993 TN99 C4 S1 50-51 62.8279 0.981 20.521 4.324 614 1338 1.0152 29.378 3.038 236 400 0.3035 30.642 2.915 129 185 0.1404 TN99 C4 S1 60-61 76.0252 1.156 20.529 4.323 593 1252 0.9929 29.405 3.035 225 385 0.3053 30.665 2.913 122 172 0.1364 Sample Monohydro- CPS corrundum CPS corrundum CPS corrundum Lake Interval Correlated Age calcite half CPS peak Calcite half CPS peak Ankerite half CPS peak ID Core Section (cm) Depth (kyr) 2 theta d value peak peak ratio 2 theta d value peak peak ratio 2 theta d value peak peak ratio TN99 C4 S1 70-71 89.2224 1.404 20.526 4.323 458 854 1.0389 29.402 3.035 260 373 0.4538 30.684 2.911 195 253 0.3078 TN99 C4 S1 75-76 95.8211 1.534 20.451 4.339 254 426 0.4356 29.368 3.039 278 475 0.4857 0.000 0.000 0 0 0.0000 TN99 C4 S1 80-81 102.064 1.653 20.507 4.327 433 857 0.6872 29.405 3.035 232 397 0.3184 30.607 2.919 120 167 0.1339 TN99 C4 S1 90-91 111.466 1.843 20.503 4.328 548 1151 1.0186 29.267 3.039 227 421 0.3726 30.559 2.923 118 175 0.1549 TN99 C4 S1 100-101 120.795 2.012 20.499 4.329 449 924 0.7972 29.419 3.034 417 267 0.2304 30.568 2.922 242 406 0.3503 TN99 C4 S1 109-110 128.444 2.177 20.503 4.328 548 1151 1.0186 29.267 3.039 227 421 0.3726 30.559 2.923 118 175 0.1549 TN99 C4 S2 9-10 138.496 2.367 20.517 4.325 535 1088 0.7959 29.407 3.035 212 384 0.2809 30.667 2.913 150 241 0.1763 TN99 C4 S2 19-20 147.346 2.512 20.507 4.327 470 956 1.0269 29.396 3.036 249 357 0.3835 0.000 0.000 0 0 0.0000 TN99 C4 S2 29-30 156.197 2.656 20.516 4.325 531 1151 0.8635 29.419 3.034 264 421 0.3158 0.000 0.000 0 0 0.0000 TN99 C4 S2 39-40 165.163 2.803 20.534 4.322 649 1328 0.9582 29.426 3.033 230 437 0.3153 30.654 2.914 110 159 0.1147 TN99 C4 S2 49-50 175.08 2.966 20.537 4.321 612 1284 0.9231 29.414 3.034 236 412 0.2962 30.620 2.917 156 232 0.1668 TN99 C4 S2 54-55 180.057 3.045 20.530 4.322 548 1134 0.8475 29.399 3.036 242 408 0.3049 30.633 2.916 148 225 0.1682 TN99 C4 S2 59-60 185 3.162 20.530 4.322 409 783 0.9244 29.442 3.031 273 353 0.4168 30.662 2.913 210 262 0.3093 TN99 C4 S2 64-65 190 3.294 20.505 4.328 577 1159 0.8598 29.380 3.037 243 458 0.3398 30.616 2.918 139 188 0.1395 TN99 C4 S2 69-70 195 3.425 20.514 4.326 663 1568 1.2524 29.337 3.042 224 475 0.3794 30.675 2.912 116 166 0.1326 TN99 C4 S2 74-75 200 3.557 20.497 4.329 471 1013 0.8463 29.357 3.040 232 453 0.3784 30.669 2.913 127 228 0.1905 TN99 C4 S2 79-80 205 3.688 20.526 4.323 565 1168 0.9168 29.382 3.037 215 406 0.3187 30.667 2.913 146 216 0.1695
103 TN99 C4 S2 84-85 210 3.820 20.529 4.323 814 1806 1.2040 29.382 3.037 243 472 0.3147 30.654 2.914 106 159 0.1060 TN99 C4 S2 89-90 215 3.952 20.553 4.318 679 1439 1.1494 29.392 3.036 186 392 0.3131 30.702 2.910 118 175 0.1398 TN99 C4 S2 94-95 220 4.083 20.522 4.324 593 1265 0.9671 29.401 3.035 218 389 0.2974 0.000 0.000 0 0 0.0000 TN99 C4 S2 99-100 225 4.215 20.533 4.322 569 1151 0.8539 29.429 3.033 313 533 0.3954 30.644 2.915 131 179 0.1328 TN99 C4 S2 104-105 230 4.346 20.527 4.323 579 1302 0.9767 29.403 3.035 259 522 0.3916 30.712 2.909 111 167 0.1253 TN99 C4 S2 109-110 235 4.478 20.513 4.326 842 1716 1.0861 29.384 3.037 374 688 0.4354 0.000 0.000 0 0 0.0000 TN99 C4 S2 110-111 236 4.504 20.523 4.324 141 219 0.2114 29.494 3.026 310 562 0.5425 0.000 0.000 0 0 0.0000 TN99 C4 S3 4-5 241 4.631 20.499 4.329 213 433 0.2999 29.432 3.032 305 556 0.3850 30.597 2.919 566 1201 0.8317 TN99 C4 S3 9-10 246 4.753 0.000 0.000 0 0 0.0000 29.479 3.028 132 228 0.1459 30.688 2.911 1141 2275 1.4555 TN99 C4 S3 10-11 247 4.778 20.510 4.327 350 718 0.4928 29.384 3.037 411 868 0.5957 30.597 2.919 510 1075 0.7378 TN99 C4 S3 15-16 252 4.900 20.521 4.324 521 1082 0.7040 29.401 3.035 805 1617 1.0520 30.584 2.921 84 149 0.0969 TN99 C4 S3 19-20 256 4.998 20.516 4.325 629 1318 0.8787 29.299 3.036 1003 2190 1.4600 30.678 2.912 76 128 0.0853 TN99 C4 S3 25-26 262 5.144 20.533 4.322 580 1294 0.8803 29.414 3.034 685 1288 0.8762 30.682 2.912 103 185 0.1259 TN99 C4 S3 29-30 266 5.242 20.530 4.323 814 1869 1.2410 29.399 3.036 372 847 0.5624 30.679 2.912 78 139 0.0923 TN99 C4 S3 34-35 271 5.364 20.538 4.321 644 1363 0.9757 29.399 3.036 348 762 0.5455 30.704 2.910 79 149 0.1067 TN99 C4 S3 38-39 275 5.462 20.516 4.326 737 1599 1.1951 29.399 3.036 477 1038 0.7758 30.678 2.912 82 139 0.1039 TN99 C4 S3 44-45 282 5.633 20.510 4.327 514 1088 0.7646 29.410 3.034 334 708 0.4975 30.685 2.911 172 335 0.2354 TN99 C4 S3 48-49 285 5.706 20.530 4.322 811 1666 1.1667 29.409 3.035 414 871 0.6099 30.647 2.915 116 204 0.1429 TN99 C4 S3 51-52 288 5.779 20.526 4.323 485 970 0.8158 29.411 3.034 366 769 0.6468 30.709 2.909 138 245 0.2061 TN99 C4 S3 54-55 291 5.853 20.544 4.320 557 1261 0.8862 29.426 3.033 774 1642 1.1539 30.711 2.909 82 131 0.0921 TN99 C4 S3 59-60 296 5.975 20.516 4.326 548 1192 0.8533 29.408 3.035 436 892 0.6385 30.611 2.918 95 154 0.1102 TN99 C4 S3 63-64 300 6.073 20.521 4.324 570 1274 0.9451 29.406 3.035 627 1376 1.0208 30.719 2.908 80 147 0.1091 TN99 C4 S3 65-66 302 6.121 20.539 4.321 398 808 0.5698 29.459 3.030 382 677 0.4774 30.683 2.911 127 191 0.1347 TN99 C4 S3 69-70 306 6.219 20.494 4.330 223 368 0.2610 29.437 3.032 358 716 0.5078 30.732 2.907 156 259 0.1837 TN99 C4 S3 74-75 311 6.341 0.000 0.000 0 0 0.0000 29.453 3.030 262 486 0.3479 30.727 2.907 594 1136 0.8132 TN99 C4 S3 79-80 316 6.463 20.537 4.321 188 339 0.2019 29.454 3.030 275 458 0.2728 30.752 2.905 493 1274 0.7588 TN99 C4 S3 85-86 321 6.586 0.000 0.000 0 0 0.0000 29.476 3.028 360 660 0.3990 30.714 2.909 351 676 0.4087 TN99 C4 S3 89-90 326 6.708 0.000 0.000 0 0 0.0000 29.490 3.026 330 571 0.3884 30.722 2.908 411 714 0.4857 TN99 C4 S3 95-96 331 6.830 0.000 0.000 0 0 0.0000 29.507 3.025 288 521 0.3759 30.684 2.911 396 705 0.5087 TN99 C4 S3 99-100 336 6.952 20.439 4.342 139 223 0.2584 29.411 3.034 231 346 0.4009 30.663 2.913 395 822 0.9525 TN99 C4 S3 104-105 341 7.074 20.563 4.316 357 745 0.4733 29.452 3.030 240 380 0.2414 30.734 2.907 575 1220 0.7751 Sample CPS corrundum CPS corrundum CPS Lake Interval Correlated Age Quartz half CPS peak Phillipsite half CPS peak Corundum half CPS ID Core Section (cm) Depth (kyr) 2 theta d value peak peak ratio 2 theta d value peak peak ratio 2 theta d value peak peak TN99 C1 S1 0-1 0.0 0.000 26.637 3.344 333 625 0.4509 27.901 3.195 137 235 0.1696 43.357 2.085 616 1386 TN99 C1 S1 5-6 5.0 0.093 26.631 3.345 252 441 0.3203 27.874 3.198 127 196 0.1423 43.354 2.085 605 1377 TN99 C1 S1 10-11 10.0 0.177 26.652 3.342 303 516 0.4311 27.911 3.194 150 228 0.1905 43.365 2.085 575 1197 TN99 C1 S1 12-13 12.0 0.203 26.646 3.343 241 452 0.3802 27.925 3.192 148 210 0.1766 43.349 2.086 573 1189 TN99 C1 S1 15-16 15.0 0.262 26.612 3.347 244 433 0.3310 27.884 3.197 157 256 0.1957 43.340 2.086 595 1308 TN99 C1 S1 20-21 20.0 0.346 26.637 3.344 291 501 0.3652 27.811 3.205 174 342 0.2493 43.362 2.085 575 1372 TN99 C1 S1 22-23 22.0 0.371 26.659 3.341 256 420 0.3443 27.910 3.194 159 205 0.1680 43.376 2.084 593 1220 TN99 C1 S1 25-26 25.0 0.431 26.628 3.345 247 412 0.3468 27.878 3.198 161 207 0.1742 43.327 2.087 575 1188 TN99 C1 S1 30-31 30.0 0.515 26.680 3.338 319 555 0.5144 27.876 3.198 162 256 0.2373 43.380 2.084 480 1079 TN99 C1 S1 32-33 32.0 0.540 26.626 3.345 289 507 0.4043 27.893 3.196 166 225 0.1794 43.355 2.085 605 1254 TN99 C1 S1 35-36 35.0 0.599 26.638 3.344 318 588 0.4579 27.912 3.194 152 222 0.1729 43.359 2.085 595 1284 TN99 C1 S1 40-41 40.0 0.677 26.637 3.344 272 477 0.4454 27.883 3.197 139 213 0.1989 43.349 2.086 533 1071 TN99 C1 S1 42-43 42.0 0.696 26.642 3.343 259 464 0.3748 27.899 3.195 147 216 0.1745 43.363 2.085 598 1238 TN99 C1 S1 45-46 45.0 0.743 26.645 3.343 295 552 0.4035 27.905 3.195 142 237 0.1732 43.363 2.085 609 1368 TN99 C1 S1 50-51 50.0 0.809 26.638 3.344 236 396 0.3005 27.929 3.192 139 185 0.1404 43.354 2.085 629 1318 TN99 C1 S1 52-53 52.0 0.829 26.644 3.343 256 420 0.3320 27.864 3.199 138 191 0.1510 43.366 2.085 566 1265 TN99 C1 S1 55-56 55.0 0.875 26.641 3.343 249 447 0.3249 27.942 3.190 128 180 0.1308 43.370 2.085 616 1376
104 TN99 C1 S1 60-61 60.0 0.942 26.645 3.343 234 417 0.3117 27.900 3.195 127 196 0.1465 43.361 2.085 659 1338 TN99 C1 S1 62-63 62.0 0.961 26.647 3.343 202 354 0.2715 27.888 3.197 132 188 0.1442 43.371 2.085 595 1304 TN99 C1 S1 65-66 65.0 1.008 26.647 3.343 240 400 0.3331 27.920 3.193 126 196 0.1632 43.352 2.085 593 1201 TN99 C1 S1 70-71 70.0 1.074 26.240 3.343 219 385 0.2975 27.901 3.195 130 196 0.1515 43.359 2.085 659 1294 TN99 C1 S1 72-73 72.0 1.094 26.640 3.343 282 491 0.3754 27.924 3.193 128 205 0.1567 43.365 2.085 609 1308 TN99 C1 S1 75-76 75.0 1.140 26.631 3.345 275 518 0.3724 27.910 3.194 138 225 0.1618 43.347 2.086 674 1391 TN99 C1 S1 80-81 80.0 1.219 26.631 3.344 223 384 0.3050 27.861 3.200 125 185 0.1469 43.331 2.086 609 1259 TN99 C1 S1 82-83 82.0 1.249 26.626 3.345 226 386 0.3051 27.874 3.198 121 185 0.1462 43.321 2.087 634 1265 TN99 C1 S2 0-1 83.0 1.268 26.637 3.344 236 446 0.3617 27.884 3.197 114 187 0.1517 43.361 2.085 584 1233 TN99 C1 S2 5-6 88.0 1.367 26.621 3.346 442 758 0.5871 27.805 3.206 211 392 0.3036 43.327 2.087 701 1291 TN99 C1 S2 9-10 92.0 1.445 26.651 3.342 374 664 0.5131 27.891 3.196 185 244 0.1886 43.359 2.085 629 1294 TN99 C1 S2 14.5-15 97.0 1.544 26.653 3.342 362 739 0.5607 27.935 3.191 172 282 0.2140 43.395 2.084 614 1318 TN99 C1 S2 19.5-20 102.0 1.642 26.645 3.343 243 477 0.4206 27.928 3.192 121 187 0.1649 43.365 2.085 556 1134 TN99 C1 S2 25-26 108.0 1.760 26.639 3.344 305 530 0.3961 27.889 3.196 145 253 0.1891 43.362 2.085 634 1338 TN99 C1 S2 35-36 118.0 1.957 26.643 3.343 208 327 0.3150 27.873 3.198 168 202 0.1946 43.351 2.086 535 1038 TN99 C1 S2 45-46 128.0 2.153 26.651 3.342 222 366 0.2221 27.885 3.197 148 207 0.1256 43.370 2.085 731 1648 TN99 C1 S2 55-56 138.0 2.350 26.608 3.347 241 412 0.3836 27.800 3.206 177 295 0.2747 43.316 2.087 502 1074 TN99 C1 S2 65-66 148.0 2.515 26.647 3.343 297 601 0.4321 27.899 3.195 139 228 0.1639 43.367 2.085 590 1391 TN99 C1 S2 75-76 158.0 2.678 26.669 3.340 357 585 0.5713 27.876 3.198 175 228 0.2227 43.380 2.084 475 1024 TN99 C1 S2 85-86 168.0 2.841 26.671 3.340 328 635 0.4462 27.906 3.194 159 279 0.1961 43.386 2.084 653 1423 TN99 C1 S2 90-91 173.0 2.923 26.647 3.343 275 480 0.3509 27.897 3.196 172 259 0.1893 43.374 2.084 614 1368 TN99 C1 S2 95-96 178.0 3.005 26.645 3.343 230 400 0.3067 27.924 3.193 155 266 0.2040 43.366 2.085 590 1304 TN99 C1 S2 99-100 182.0 3.072 26.670 3.340 328 625 0.4343 27.942 3.191 161 237 0.1647 43.397 2.083 664 1439 TN99 C4 S1 0-1 0.0 0.000 26.647 3.343 303 516 0.4121 27.933 3.191 184 283 0.2260 43.391 2.084 548 1252 TN99 C4 S1 10-11 10.0 0.181 26.649 3.342 285 501 0.3533 27.876 3.198 180 254 0.1791 43.367 2.085 675 1418 TN99 C4 S1 20-21 23.2 0.403 26.639 3.344 240 441 0.3134 27.916 3.193 173 250 0.1777 43.365 2.085 685 1407 TN99 C4 S1 30-31 36.4 0.626 26.425 3.370 251 432 0.3338 27.648 3.224 133 196 0.1515 43.151 2.095 609 1294 TN99 C4 S1 39-40 48.3 0.789 26.663 3.341 401 876 0.5794 27.926 3.192 162 286 0.1892 43.392 2.084 725 1512 TN99 C4 S1 40-41 49.6 0.806 26.632 3.344 257 463 0.3783 27.900 3.195 157 222 0.1814 43.355 2.085 575 1224 TN99 C4 S1 50-51 62.8 0.981 26.639 3.344 222 385 0.2921 27.877 3.198 132 166 0.1259 43.347 2.086 619 1318 TN99 C4 S1 60-61 76.0 1.156 26.664 3.340 291 571 0.4528 27.923 3.193 138 191 0.1515 43.364 2.085 566 1261 Sample CPS corrundum CPS corrundum CPS Lake Interval Correlated Age Quartz half CPS peak Phillipsite half CPS peak Corundum half CPS ID Core Section (cm) Depth (kyr) 2 theta d value peak peak ratio 2 theta d value peak peak ratio 2 theta d value peak peak TN99 C4 S1 70-71 89.2 1.404 26.663 3.341 426 691 0.8406 27.929 3.192 305 486 0.5912 43.362 2.085 442 822 TN99 C4 S1 75-76 95.8 1.534 26.563 3.353 299 535 0.5470 27.797 3.207 175 243 0.2485 43.263 2.090 467 978 TN99 C4 S1 80-81 102.1 1.653 26.637 3.344 358 667 0.5349 27.966 3.188 218 395 0.3168 43.351 2.086 616 1247 TN99 C4 S1 90-91 111.5 1.843 26.626 3.345 251 441 0.3903 27.911 3.194 137 210 0.1858 43.353 2.085 586 1130 TN99 C4 S1 100-101 120.8 2.012 26.624 3.345 273 441 0.3805 27.925 3.192 169 231 0.1993 43.351 2.086 565 1159 TN99 C4 S1 109-110 128.4 2.177 26.626 3.345 251 441 0.3903 27.911 3.194 137 210 0.1858 43.353 2.085 586 1130 TN99 C4 S2 9-10 138.5 2.367 26.637 3.344 270 459 0.3358 27.909 3.194 155 231 0.1690 43.358 2.085 573 1367 TN99 C4 S2 19-20 147.3 2.512 26.646 3.343 286 441 0.4737 0.000 0.000 0 0 0.0000 43.362 2.085 485 931 TN99 C4 S2 29-30 156.2 2.656 26.636 3.344 326 600 0.4501 27.904 3.195 170 247 0.1853 43.360 2.085 619 1333 TN99 C4 S2 39-40 165.2 2.803 26.663 3.341 382 724 0.5224 27.913 3.194 153 244 0.1760 43.386 2.084 658 1386 TN99 C4 S2 49-50 175.1 2.966 26.669 3.340 251 428 0.3077 27.951 3.189 146 208 0.1495 43.386 2.084 642 1391 TN99 C4 S2 54-55 180.1 3.045 26.645 3.343 252 445 0.3326 27.913 3.194 135 182 0.1360 43.374 2.084 659 1338 TN99 C4 S2 59-60 185.0 3.162 26.663 3.341 289 420 0.4959 27.862 3.199 226 259 0.3058 43.392 2.084 455 847 TN99 C4 S2 64-65 190.0 3.294 26.616 3.346 255 489 0.3628 27.855 3.200 135 196 0.1454 43.345 2.086 629 1348 TN99 C4 S2 69-70 195.0 3.425 26.632 3.344 201 370 0.2955 27.890 3.196 111 169 0.1350 43.359 2.085 575 1252 TN99 C4 S2 74-75 200.0 3.557 26.639 3.344 182 340 0.2840 27.895 3.196 113 177 0.1479 43.357 2.085 552 1197 TN99 C4 S2 79-80 205.0 3.688 26.638 3.344 210 404 0.3171 27.895 3.916 121 182 0.1429 43.359 2.085 580 1274
105 TN99 C4 S2 84-85 210.0 3.820 26.654 3.342 404 819 0.5460 27.907 3.194 136 237 0.1580 43.383 2.084 633 1500 TN99 C4 S2 89-90 215.0 3.952 26.676 3.339 217 404 0.3227 27.937 3.191 124 182 0.1454 43.395 2.083 570 1252 TN99 C4 S2 94-95 220.0 4.083 26.661 3.341 330 615 0.4702 27.897 3.196 157 253 0.1934 43.376 2.084 605 1308 TN99 C4 S2 99-100 225.0 4.215 26.662 3.341 316 558 0.4139 27.932 3.192 177 266 0.1973 43.393 2.084 614 1348 TN99 C4 S2 104-105 230.0 4.346 26.645 3.343 235 444 0.3331 27.896 3.196 140 228 0.1710 43.362 2.085 600 1333 TN99 C4 S2 109-110 235.0 4.478 26.630 3.345 348 638 0.4038 0.000 0.000 0 0 0.0000 42.354 2.085 805 1580 TN99 C4 S2 110-111 236.0 4.504 26.652 3.342 322 559 0.5396 27.889 3.196 183 256 0.2471 43.375 2.084 502 1036 TN99 C4 S3 4-5 241.0 4.631 26.624 3.345 264 458 0.3172 27.880 3.197 113 180 0.1247 43.348 2.086 664 1444 TN99 C4 S3 9-10 246.0 4.753 26.632 3.344 226 372 0.2380 0.000 0.000 0 0 0.0000 43.360 2.085 705 1563 TN99 C4 S3 10-11 247.0 4.778 26.613 3.347 157 281 0.1929 0.000 0.000 0 0 0.0000 43.339 2.086 649 1457 TN99 C4 S3 15-16 252.0 4.900 26.644 3.343 259 569 0.3702 27.910 3.194 115 207 0.1347 43.359 2.085 663 1537 TN99 C4 S3 19-20 256.0 4.998 26.639 3.344 214 425 0.2833 27.888 3.197 99 164 0.1093 43.344 2.086 602 1500 TN99 C4 S3 25-26 262.0 5.144 26.655 3.342 270 533 0.3626 27.958 3.189 116 191 0.1299 43.363 2.085 700 1470 TN99 C4 S3 29-30 266.0 5.242 26.654 3.342 156 276 0.1833 27.908 3.194 95 169 0.1122 43.368 2.085 706 1506 TN99 C4 S3 34-35 271.0 5.364 26.651 3.342 232 478 0.3422 27.876 3.198 161 262 0.1875 43.366 2.085 632 1397 TN99 C4 S3 38-39 275.0 5.462 26.655 3.342 183 410 0.3064 27.902 3.195 87 137 0.1024 43.360 2.085 619 1338 TN99 C4 S3 44-45 282.0 5.633 26.632 3.344 209 405 0.2846 27.903 3.195 110 188 0.1321 43.359 2.085 674 1423 TN99 C4 S3 48-49 285.0 5.706 26.666 3.340 171 310 0.2171 27.962 3.188 96 144 0.1008 43.385 2.084 632 1428 TN99 C4 S3 51-52 288.0 5.779 26.670 3.340 239 446 0.3751 27.860 3.200 146 216 0.1817 43.371 2.085 590 1189 TN99 C4 S3 54-55 291.0 5.853 26.653 3.342 156 289 0.2031 28.022 3.182 189 328 0.2305 43.370 2.085 569 1423 TN99 C4 S3 59-60 296.0 5.975 26.651 3.342 319 635 0.4545 27.911 3.194 154 267 0.1911 43.358 2.085 664 1397 TN99 C4 S3 63-64 300.0 6.073 26.645 3.343 176 328 0.2433 27.918 3.193 83 135 0.1001 43.360 2.085 575 1348 TN99 C4 S3 65-66 302.0 6.121 26.674 3.339 446 882 0.6220 27.899 3.195 155 269 0.1897 43.382 2.084 642 1418 TN99 C4 S3 69-70 306.0 6.219 26.620 3.346 647 1223 0.8674 27.858 3.200 261 441 0.3128 43.345 2.086 629 1410 TN99 C4 S3 74-75 311.0 6.341 26.642 3.343 241 441 0.3157 27.895 3.196 161 234 0.1675 43.370 2.085 674 1397 TN99 C4 S3 79-80 316.0 6.463 26.660 3.341 325 677 0.4032 27.933 3.191 156 263 0.1566 43.392 2.084 713 1679 TN99 C4 S3 85-86 321.0 6.586 26.653 3.342 546 1077 0.6511 27.919 3.193 212 396 0.2394 43.389 2.084 762 1654 TN99 C4 S3 89-90 326.0 6.708 26.666 3.340 460 892 0.6068 27.931 3.192 224 358 0.2435 43.401 2.083 679 1470 TN99 C4 S3 95-96 331.0 6.830 26.633 3.344 371 656 0.4733 27.857 3.200 168 238 0.1717 43.349 2.086 690 1386 TN99 C4 S3 99-100 336.0 6.952 26.602 3.348 198 317 0.3673 27.858 3.200 158 222 0.2572 43.325 2.087 414 863 TN99 C4 S3 104-105 341.0 7.074 26.674 3.339 235 433 0.2751 27.940 3.191 102 174 0.1105 43.401 2.083 669 1574
APPENDIX E
LAKE UGIY X-RAY POWDER DIFFRACTOMETER MINERALOGY DATA
CPS-COUNTS PER SECOND
106 Sample CPS corrundum CPS corrundum Anorthite, CPS corrundum Lake Interval Correlated Age Quartz half CPS peak Albite half CPS peak sodian half CPS peak ID Core Section (cm) Depth (kyr) 2 theta d value peak peak ratio 2 theta d value peak peak ratio 2 theta d value peak peak ratio UN99 C1 D1 0-1 0.00 0.000 26.634 3.344 946 1697 1.3415 22.024 4.033 174 296 0.2340 27.889 3.196 401 689 0.5447 UN99 C1 D1 20-21 19.40 0.264 26.634 3.344 823 1697 1.3415 22.024 4.033 153 296 0.2340 27.892 3.196 416 685 0.5415 UN99 C1 D1 47-48 45.59 0.619 26.660 3.341 799 1512 1.9286 22.046 4.029 230 339 0.4324 27.908 3.194 395 656 0.8367 UN99 C1 D1 88-89 85.36 1.160 26.627 3.345 1161 2198 1.5285 22.015 4.034 200 349 0.2427 27.883 3.197 477 875 0.6085 UN99 C1 D2 8-9 109.68 1.490 26.656 3.341 780 1460 1.6553 22.042 4.029 223 327 0.3707 27.920 3.193 436 677 0.7676 UN99 C1 D2 40-41 140.40 1.908 26.633 3.344 873 1617 1.3916 22.007 4.036 175 320 0.2754 27.888 3.197 401 719 0.6188 UN99 C1 D2 72-73 171.12 2.325 26.640 3.343 864 1736 1.5135 22.029 4.032 229 336 0.2929 27.890 3.196 450 714 0.6225 UN99 C1 D2 88-89 186.48 2.534 26.670 3.340 493 879 1.4650 22.031 4.031 172 237 0.3950 27.887 3.197 315 472 0.7867 UN99 C1 D3 24-25 225.04 3.058 26.622 3.346 850 1848 1.1608 22.005 4.036 147 263 0.1652 27.850 3.201 346 678 0.4259 UN99 C1 D4 32-33 284.00 3.859 26.655 3.342 1098 2198 2.6642 22.031 4.031 206 318 0.3855 27.974 3.187 821 1743 2.1127 UN99 C1 D5 1-2 331.00 4.497 26.623 3.345 1027 2142 1.5021 22.010 4.035 151 263 0.1844 27.887 3.197 406 697 0.4888 UN99 C1 D6 17-18 359.00 4.878 26.629 3.345 885 1918 1.1995 22.013 4.035 156 253 0.1582 27.886 3.197 326 566 0.3540
107 Sample CPS corrundum CPS corrundum CPS Lake Interval Correlated Age Calcite half CPS peak Mg-calcite half CPS peak Corundum half CPS ID Core Section (cm) Depth (kyr) 2 theta d value peak peak ratio 2 theta d value peak peak ratio 2 theta d value peak peak UN99 C1 D1 0-1 0.00 0.000 29.517 3.024 382 640 0.5059 0.000 0 0 0 0.0000 43.354 2.085 548 1265 UN99 C1 D1 20-21 19.40 0.264 29.518 3.024 363 639 0.5051 0.000 0 0 0 0.0000 43.362 2.085 557 1265 UN99 C1 D1 47-48 45.59 0.619 0.000 0.000 0 0 0.0000 0.000 0 0 0 0.0000 43.377 2.084 367 784 UN99 C1 D1 88-89 85.36 1.160 0.000 0.000 0 0 0.0000 29.813 2.994 172 299 0.2079 43.340 2.086 631 1438 UN99 C1 D2 8-9 109.68 1.490 0.000 0.000 0 0 0.0000 29.888 2.987 222 296 0.3356 43.378 2.084 435 882 UN99 C1 D2 40-41 140.40 1.908 0.000 0.000 0 0 0.0000 29.804 2.995 188 266 0.2289 43.344 2.086 580 1162 UN99 C1 D2 72-73 171.12 2.325 0.000 0.000 0 0 0.0000 29.845 2.991 224 276 0.2406 43.361 2.085 548 1147 UN99 C1 D2 88-89 186.48 2.534 0.000 0.000 0 0 0.0000 29.843 2.991 188 235 0.3917 43.355 2.085 327 600 UN99 C1 D3 24-25 225.04 3.058 29.513 3.024 337 692 0.4347 0.000 0 0 0 0.0000 43.344 2.086 682 1592 UN99 C1 D4 32-33 284.00 3.859 29.480 3.027 281 392 0.4752 0.000 0 0 0 0.0000 43.366 2.085 420 825 UN99 C1 D5 1-2 331.00 4.497 29.492 3.026 266 472 0.3310 0.000 0 0 0 0.0000 43.348 2.086 657 1426 UN99 C1 D6 17-18 359.00 4.878 29.528 3.023 575 1249 0.7811 0.000 0 0 0 0.0000 43.351 2.085 700 1599