1
THE LATE MIOCENE THROUGH MODERN EVOLUTION OF THE ZHADA BASIN, SOUTH-WESTERN TIBET
by
Joel Edward Saylor
A Dissertation Submitted to the Faculty of the
DEPARTMENT OF GEOSCIENCES
In Partial Fulfillment of the Requirements for the Degree of
DOCTOR OF PHILOSOPHY
In the Graduate College
THE UNIVERSITY OF ARIZONA
2 0 0 8 2
THE UNIVERSITY OF ARIZONA
GRADUATE COLLEGE
As members of the Dissertation Committee, we certify that we have read the dissertation prepared by: Joel E. Saylor entitled: The Late Miocene Through Modern Evolution of the Zhada Basin, South-western Tibet and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of: Doctor of Philosophy
______Date: Peter DeCelles
______Date: Jay Quade
______Date: Paul Kapp
______Date: George Gehrels
______Date: Mihai Ducea
Final approval and acceptance of this dissertation is contingent upon the candidate’s submission of the final copies of the dissertation to the Graduate College.
I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement.
______Date: Dissertation Director: Peter DeCelles
______Date: Dissertation Director: Jay Quade 3
STATEMENT BY THE AUTHOR
This dissertation has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.
Brief quotations from this dissertation are allowable without special permission, provided that accurate acknowledgement of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department of the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author.
Signed: Joel Saylor
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ACKOWLEDGEMENTS This dissertation would not have been possible without the help of many people. Foremost, my family: Jeannette, and Eirena for putting up with an absent (or busy) husband and father; Gary, Lita, and Nathaniel for their support and raising me. I owe a lifetime debt to my advisors: Drs. Pete DeCelles and Jay Quade for their patience, tutelage, and unending support. I also owe thanks to Dr. Paul Kapp for reading chapters (many times over) and many good comments and discussions; Dr. George Gehrels for his help with detrital zircon analyses and Dr. Mihai Ducea. Likewise, this work would not have happened without my field assistants: Jeannette Saylor, Scott McBride, Cai Fulong and our Tibetan crew. A special thanks to Facundo Fuentes, John Volkmer, Ross Waldrip, Lynn Peyton, Jerome Guynn, Andrew Leier, Aaron Martin, Matt Fabijanic, Adam and Amy Baker, Ari and Jane Heinze, Ryan and Janine Wilkinson, Jon Dyhr, Lise Johnson, Carrie Coykendall, Meghan Field, Sam Jayakanthan and many others from the Dept. of Geosciences, Graduate Christian Fellowship, and Northwest Community Friends Church for laughs, commiseration, and generally making life enjoyable. To others who have helped me work through ideas, given me pointers or hung out: thank you. Finally, I would like to thank those who I have worked with in the course of this project and hope to work with again: Dick Heermance for help with cosmogenic nuclide work; Mike Murphy and Ran Zhang for ideas and research help; Tank Ojha for assistance in the paleomagnetism lab; David Dettman for advice and assistance with stable isotope analyses; Majie Fan for assistance with organic material analyses and useful discussions; Victor Valencia for help with U-Pb analyses; and E. Lindsay and X. Wang for identification of mammal fossils and biostratigraphy. This research was supported by grants from the Geological Society of America, the American Association of Petroleum Geologists, ExxonMobil, Chevron-Texaco, The Galileo Circle of the U of A and National Science Foundation (grants EAR-0443387 and 0732436) and the National Science Foundation Tectonics Program. 5
DEDICATION
Pro Veritas 6
TABLE OF CONTENTS
LIST OF FIGURES………………………………...... ………………...9
LIST OF TABLES……………………………...... ……………………...11
ABSTRACT…………………………………...... …………………..12
CHAPTER 1: INTRODUCTION……………………...... ……...13
CHAPTER 2: THE LATE MIOCENE THROUGH PRESENT PALEOELEVATION HISTORY OF SOUTHWESTERN TIBET...... 17 ABSTRACT………………………………………...... …………………17 INTRODUCTION……..…..……………………...... ………....….19 Previous Paleoelevation Work…………………..……...... …....…..20 OXYGEN ISOTOPE PALEOALTIMETRY……………...... ……..23 REGIONAL SETTING OF ZHADA BASIN……………...... …………..27 METHODS AND MATERIALS…………………...... …………....…..30 Age Control………………………...... ……………………...30 Modern Water…………………………...... ………………..32 Gastropods………………………………………...... ……………33 Zhada Formation Plant Material…………………...... ……………...34 RESULTS……………………………………...... …………...36 Age……………………………………...... ………………….36 Modern Water………………………...... ……………………..38 Gastropods……………………………………...... ……………39 Zhada Formation Plant Material…………………...... …...... ……...40 APPLICATION TO PALEOALTIMETRY………………...... …...41 18 Calculation of Miocene δ Osw and Related Constraints and Corrections.....41 Source, pathway and amount effect constraints...... 41 Shell preservation...... 43 18 Calculation of Miocene δ Opsw...... 43 Comparison with Models...... 44 Effect of paleotemperature...... 44 Modelling changes in lapse rate...... 45 Evaporation vs. Outflow...... 46 Temperature of Modern Gastropod Shell Precipitation...... 48 Paleoelevation models...... 49 DISCUSSION AND CONCLUSIONS...... 55 Oxygen Isotopes from Zhada Basin...... 55 Oxygen Isotopes from Zhongba...... 58 Carbon Isotopes...... 59 Application to Tectonic Models...... 60 CONCLUSIONS...... 62 7
TABLE OF CONTENTS – Continued
CHAPTER 3: BASIN FORMATION DUE TO ARC-PARALLEL EXTENSION AND TECTONIC DAMMING: ZHADA BASIN, SW TIBET...... 95 ABSTRACT………………………………………...... 95 INTRODUCTION…………………………………...... 96 GEOLOGIC SETTING…………………………………...... 98 SEDIMENTOLOGY OF THE ZHADA FORMATION...... 100 Fluvial Association…………………………………………...... 100 Lithofacies Association F1: Gcmi, Gch, Gt, Gcf...... 100 Lithofacies Association F2: St, Sp, Sh, Sc...... 101 Lithofacies Association F3: Sm, Sc, Mm, Mc, Ml, Mh...... 101 Interpretation...... 102 Supra-littoral (Lake Margin) Association...... 103 Lithofacies Association S1: Gct, Gcmi, Sp, St, Sh, Sm, Sr...... 103 Lithofacies Association S2: Sh...... 104 Lithofacies Association S3: Sf...... 104 Interpretation...... 104 Littoral Association...... 105 Lithofacies Association L1: Ml...... 105 Lithofacies Association L2: Mr, Sr, Srw, Sp, Sh, Sm...... 105 Interpretation...... 106 Profundal Association...... 106 Lithofacies Association P1: Mh, Mm...... 106 Lithofacies Association P2: Sh, Sm, Mh...... 107 Interpretation...... 107 Alluvial Fan Association...... 108 Lithofacies Association A1: Gcm, Gch, Gcmi...... 108 Lithofacies Association A2: Gmm, Gcm...... 108 Lithofacies Association A3: Gcmi, Gch, Gcf...... 108 Lithofacies Association A4: Gx...... 109 Interpretation...... 109 Zhada Formation members...... 110 PALEOCURRENT MEASUREMENTS...... 112 PROVENANCE ANALYSIS...... 113 Methods...... 113 Sandstone petrography and conglomerate clast counts...... 113 U-Pb geochronologic analyses of detrital zircons...... 113 Results...... 115 Sandstone and conglomerate modal compositions...... 115 U-Pb geochronologic analyses of detrital zircons...... 117 Summary of detrital zircon U-Pb analyses...... 120 Interpretation...... 120 Sandstone and conglomerate provenance...... 120 8
TABLE OF CONTENTS – Continued
U-Pb geochronologic analyses of detrital zircons...... 123 SUBSIDENCE CURVE...... 125 DISCUSSION...... 126 Zhada Basin Evolution...... 126 Tectonic Origins of the Zhada Basin...... 128 SYNTHESIS...... 133 CONCLUSIONS...... 135
CHAPTER 4: CLIMATE-DRIVEN ENVIRONMENTAL CHANGE IN THE SOUTHERN TIBETAN PLATEAU...... 201 ABSTRACT...... 201 INTRODUCTION...... 202 REGIONAL GEOLOGICAL SETTING...... 205 METHODS...... 207 Sedimentology...... 207 Correlations...... 207 Frequency analysis of Zhada Formation cycles...... 207 Stable Isotopes...... 209 RESULTS...... 211 Sedimentology...... 211 Depositional Cycles in the Zhada Formation...... 211 Correlations...... 212 Frequency analysis of Zhada Formation cycles...... 214 Stable Isotopes...... 215 INTERPRETATION OF ZHADA FORMATION CYCLES...... 216 DISCUSSION...... 218 Sequence Stratigraphic and Lithostratigraphic Correlations...... 218 Frequency analysis...... 221 Isotopes in Zhada Formation cycles...... 222 Basin history...... 224 Global climate change and its impact on the southern Tibetan Plateau...... 225 CONCLUSIONS...... 230
WORKS CITED...... 277
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LIST OF FIGURES
Figure 2.1: Location map…………………………………………………...... 63 Figure 2.2: Vector component diagrams for the South Zhada Section...... 64 Figure 2.3: Site and section mean vectors for South Zhada and Southeast Zhada...... 65 Figure 2.4: Modern water and gastropod sample locations from the Zhongba area...... 66 Figure 2.5: δ13C of vascular organic material versus stratigraphic level for the South Zhada and East Zhada measured sections...... 67 Figure 2.6: Measured sections and magnetostratigraphic results……………...... 68 Figure 2.7: Stable isotope composition of modern water from the Zhada Basin and Zhongba area plotted against the Global Meteoric Water Line…………...... 70 Figure 2.8: X-Ray diffraction data……………………………………………...... 71 Figure 2.9: Oxygen and carbon isotope covariance for gastropods………...... 72 Figure 2.10: δ18O vs. stratigraphic height for Miocene – Pleistocene gastropods...... 74 Figure 2.11: δ18O vs. mm growth from seasonally sampled Miocene – Pleistocene gastropods………………………………………………………...... 76 18 Figure 2.12: Calculated δ Opw values from gastropods...... 77 Figure 2.13: Modelled enrichment values...... 79 Figure 2.14: Temperature of aragonite precipitation...... 80 Figure 2.15: Modelled percent of modern aragonite in equilibrium with monsoon wetland waters……………………………………………………………...... 81 Figure 2.16: Δδ18O of modern water vs. mean and maximum catchment elevation...... 82 Figure 2.17: Δδ18O values for the most negative modern Zhada water samples and most negative reconstructed Miocene – Pleistocene water vs. modelled elevation...... 83 Figure 2.18: Comparison of the range of Δδ18O values for reconstructed Miocene fluvial water and modern water from the Zhada Basin verses elevation...... 84
Figure 3.1: Location map………………………………………………...... 136 Figure 3.2: Topographic profile along the Himalayan arc……………...... 138 Figure 3.3: Geologic map of the Zhada region...... 140 Figure 3.4: Photos of stratigraphic relationships between the Zhada Formation and basement…………………………………………………………...... 141 Figure 3.5: Correlation of the composite magnetostratigraphic section with the GPTS of Lourens et al. (2004)...... 143 Figure 3.6: Measured sections……………………………………………...... 145 Figure 3.7: Photos of Fluvial association lithofacies……………………...... 151 Figure 3.8: Photos of Supra-littoral association lithofacies………………...... 153 Figure 3.9: Photos of Littoral association lithofacies……………………...... 154 Figure 3.10: Photos of Profundal association lithofacies………………...... 155 Figure 3.11: Photos of Alluvial fan association lithofacies……………...... 156 Figure 3.12: Zhada Formation members……………………………...... 158 Figure 3.13: Paleocurrent data for the lower members and the upper members of the Zhada formation………………………………………………...... 160 Figure 3.14: Photomicrographs of Zhada Formation sandstones…………...... 162 10
LIST OF FIGURES - Continued
Figure 3.15: QFL diagrams for samples from this study…………………...... 164 Figure 3.16: U/Pb concordia plots for detrital zircons samples from this study...... 166 Figure 3.17: U/Pb relative age-probability density diagrams for detrital zircons and possible source terranes...... 168 Figure 3.18: Subsidence curves...... 170 Figure 3.19: Growth structure in Zhada Formation...... 172 Figure 3.20: Photos of windgap...... 174 Figure 3.21: Perspective diagram of basin evolution...... 176 Figure 3.22: Paleogeographic maps...... 178
Figure 4.1: Location map...... 232 Figure 4.2: South Zhada lithologic section and magnetostratigraphic section and correlation to the global polarity timescale (GPTS) of Lourens et al. (2004).....233 Figure 4.3: The synthetic wave form constructed for spectral analysis…...... 234 Figure 4.4: Idealized forms of parasequence types A and B and interpreted depositional environments...... 236 Figure 4.5: Photos of parasequence types A and B...... 237 Figure 4.6: Detailed parasequence correlation...... 238 Figure 4.7: Basin-wide lithostratigraphic and sequence stratigraphic correlations...... 240 Figure 4.8: Photo of second order transgressive surface...... 243 Figure 4.9: Frequency analysis...... 244 Figure 4.10: South Zhada lithologic section and associated δ18O values of aquatic gastropods...... 246 Figure 4.11: The trajectory of Zhada basin evolution in accommodation and sediment- and water-supply space...... 248 Figure 4.12: δ18O and δ13C values of aquatic gastropods plotted against their normalized height above the flooding surface...... 249 11
LIST OF TABLES
Table 2.1: Stable isotope and elevation data for modern water from the Zhada Basin and Zhongba area………………………………………………...... 85 Table 2.2: Oxygen and carbon isotope data (VPDB) from Miocene – Pleistocene gastropods from Zhada Basin…………...... ……...... 87 Table 2.3: δ13C (VPDB ‰) for plant material from the South Zhada and East Zhada sections……………………………………………………………...... 93
Table 3.1: Lithofacies codes and interpretation………………………...... 180 Table 3.2: Paleocurrent data……………………………………………...... 182 Table 3.3: Pointcount parameters………………...... ……...... 183 Table 3.4: Recalculated petrographic pointcount data……………………...... 184 Table 3.5:. Detrital zircon U-Pb data table…………………………………...... 185
Table 4.1: Data used in frequency analysis………...... …………...... 251 Table 4.2: Lithofacies association codes, descriptions, and interpretations...... 273 Table 4.3: Stable isotope data………………………………………………...... 275
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ABSTRACT
The uplift history of the Tibetan Plateau is poorly constrained in part due to its complex and extended tectonic history. This study uses basin analysis, stable isotope analysis, magnetostratigraphy, detrital zircon U-Pb dating, and paleoaltimetry, and frequency analysis to reconstruct the tectonic, spatial, and environmental evolution of the
Zhada basin in southwestern Tibet since the late Miocene. The Zhada Formation, which occupies the Zhada basin and consists of ~ 850 m of fluvial, alluvial fan, eolian, and lacustrine sediments, is undeformed and lies in angular unconformity above Tethyan
18 sedimentary sequence strata. The most negative Miocene δ Opsw (paleo-surface water) values reconstructed from aquatic gastropods are significantly more negative than the
18 most negative modern δ Osw (surface water) values. In the absence of any known climate change which would have produced this difference, we interpret it as indicating a decrease in elevation in the catchment between the late Miocene and the present. Basin analysis indicates that the decrease in elevation was accomplished by two low-angle detachment faults which root beneath the Zhada basin and exhume mid-crustal rocks.
This exhumation results from ongoing arc-parallel extension and provides accommodation for Zhada basin fill. Sequence stratigraphy shows that the basin evolved from an overfilled to an underfilled basin but that further evolution was truncated by an abrupt return to overfilled, incising conditions. This evolution is linked to progressive damming of the paleo-Sutlej River. During the underfilled portion of basin evolution, depositional environments were strongly influenced by Milancovitch cyclicity: particularly at the precession and eccentricity frequencies. 13
CHAPTER 1: INTRODUCTION
The Tibetan Plateau is the largest high-elevation, low-relief plateau on earth.
Average elevations across the plateau are ~5,000 m (Fielding et al., 1994) and the area of the plateau is > 5,000,000 km2 (Fielding, 1996). The plateau was formed by the early
Paleozoic – Tertiary collision of multiple continental fragments into the southern margin of Eurasia and subduction of intervening oceans (Allegre et al., 1984; e.g., Dewey et al.,
1988; Leier et al., 2007; Murphy et al., 1997; Sengor and Natal'in, 1996; Yin and
Harrison, 2000). Models developed in the Himlayan/Tibetan orogen drive thinking about orogens worldwide (e.g., Beaumont et al., 2004; Gerbault et al., 2005; Royden et al.,
1997) and uplift of the Tibetan Plateau is often linked to regional or global climate change (e.g., Abe et al., 2005; An et al., 2001; France-Lanord and Derry, 1994; Molnar,
2005; Molnar et al., 1993; Raymo and Ruddiman, 1992; Ruddiman et al., 1997).
The temporal and spatial uplift of the Tibetan Plateau is essential to both tectonic and climatic models. Yet the uplift history is poorly constrained. Paleoenvironmental proxies from as late as the Pleistocene indicate that conditions on the Tibetan Plateau were warmer and wetter than today (e.g., Axelrod, 1981; Cao et al., 1981; Li and Li,
1990; Li and Zhou, 2001a, b; Meng et al., 2004; Molnar, 2005; Wang et al., 2006; Wang et al., 2008c; Xu, 1981; Zhang et al., 1981), indicative of lower elevations. Recent quantitative paleoelevation studies suggest high elevations extending back at least to the
Eocene – Oligocene (Currie et al., 2005; Cyr et al., 2005; DeCelles et al., 2007; Garzione et al., 2000a; Graham et al., 2005; Rowley and Currie, 2006; Rowley et al., 2001; Spicer et al., 2003). This dichotomy and the underlying need to establish a comprehensive 14 paleoelevation record for the Tibetan Plateau was the first motivating factor in this dissertation.
The second motivating factor is that the Zhada basin, being a large, late Cenozoic basin surrounded by normal faults at anomalously low elevations on the southern Tibetan
Plateau, represents an unparalleled opportunity to study east-west extension in the
Himalayan-Tibetan orogen. Ongoing deformation in the southern Tibetan Plateau is dominated by east-west extension, despite continuing northward movement of India (e.g.,
Armijo et al., 1986; Hurtado et al., 2001; Kapp and Guynn, 2004; Molnar et al., 1993;
Molnar and Tapponnier, 1978; Ni and York, 1978; Ratschbacher et al., 1994; Taylor et al., 2003). East-west extension has variably been attributed to oroclinal bending
(Klootwijk et al., 1985; Ratschbacher et al., 1994), oblique convergence (McCaffrey and
Nabelek, 1998; Seeber and Pecher, 1998), outward radial expansion of the Himalayan thrust front (Molnar and Lyon-Caen, 1988; Murphy and Copeland, 2005; Seeber and
Armbruster, 1984). East-west extension is best expressed in basins bounded by approximately north-south trending normal faults. Basin fill in the internally drained portion of the Tibetan Plateau is largely covered in Quaternary alluvium. Basins on the southern, externally drained Tibetan Plateau present the best opportunity to study the ongoing process of east-west extension. However, these basins remain largely unstudied
(e.g., Garzione et al., 2003).
The final motivating factor is that the Zhada basin has been poorly studied. The
Zhada basin contains an abundance of invertebrate, vertebrate and plant fossils (Li and
Li, 1990; Li and Zhou, 2001a, b; Meng et al., 2004; Yu et al., 2007; Zhang et al., 1981). 15
Despite the importance of the basin there is little agreement about even the most basic aspects of it. Reports of the age, lithologies, paleoenvironment, paleoelevation, originating cause, and basin history vary widely (e.g., Li and Zhou, 2001b; Meng et al.,
2008; Wang et al., 2008a; Wang et al., 2008b; Wang et al., 2004; Zhou et al., 2000; Zhu et al., 2004).
The goal of this investigation is to provide a coherent paleoelevation history, originating cause, basin evolution and paleoenvironmental reconstruction of the Zhada basin. This data is used to test the proposed models for east-west extension in southwestern Tibet. The data used in this study include, but are not limited to, >300 stable isotope analyses of carbonate and water, >730 paleomagnetic analyses from 184 sites, >800 paleocurrent measurements at ~ 80 sites, >4.8 km of lithologic section from
14 measured sections, 35 point counted petrographic thin sections and >750 U-Pb analyses of detrital zircons.
The following chapters represent three manuscripts that are in various stages of publication. Chapter 2, The late Miocene through present paleoelevation history of southwestern Tibet, presents stable isotope evidence for high elevations in southwestern
Tibet extending back at least to the late Miocene. It also provides the first stable isotope evidence for a loss of elevation in southwestern Tibet and tentatively links that loss of elevation with crustal thinning associated with east-west extension. This manuscript has been accepted for publication in the American Journal of Science.
Chapter 3, Basin formation due to arc-parallel extension and tectonic damming:
Zhada basin, SW Tibet tracks the evolution of the Zhada basin from a through-flowing 16 river to a closed-basin lake and to its final stage as a deeply exhumed open basin. Basin evolution is described in terms of sedimentology, sediment provenance and sediment dispersal patterns. This data set is used to propose that the originating cause for the basin was subsidence and behind an uplifting sill due to arc-parallel extension. This manuscript will be submitted to Tectonics (or GSAB).
Chapter 4, Climate-driven environmental change in the southern Tibetan Plateau, decouples environmental change on the southwestern Tibetan Plateau from uplift of the plateau through sequence stratigraphic analysis of the Zhada basin fill. Faunal and floral changes in the basin are shown to be synchronous with changes in basins surrounding the
Tibetan Plateau and likely due to regional or global climate change. Stable isotopes reveal distinct drying episodes which are linked to Milankovitch cycles. This manuscript will be submitted to Sedimentology.
17
CHAPTER 2: THE LATE MIOCENE THROUGH PRESENT
PALEOELEVATION HISTORY OF SOUTHWESTERN TIBET
ABSTRACT.
Recent research using stable isotopes of carbon and oxygen from carbonates and fossil teeth seems to support both a pre- and post-mid-Miocene uplift of the southern
Tibetan Plateau. We examined this issue by analysis of well-preserved fossil mollusks and plant remains from the Zhada Basin in southwestern Tibet, which ranges in age from
18 ~ 9.2 - <1 Ma. Based on δ Occ values from shell aragonite, we estimate that oxygen
18 isotope ratios of Miocene – Pleistocene paleo-surface water (δ Opsw) in Zhada Basin ranged from –24.5 to –2.2‰ (VSMOW). The lowest of these calculated values are lower
18 than δ Osw values (–17.9 to –11.9‰ (VSMOW)) of modern water in the basin. The
18 18 extremely low δ Opsw values from fluvial mollusks and evaporatively elevated δ Opsw values from lacustrine mollusks, show that the peaks surrounding the Zhada Basin were at elevations at least as high as, and possibly up to 1.5 km higher than today, and that conditions have been arid since at least 9 Ma. A decrease in elevation since the Miocene is not specifically predicted by any existing mechanical models for the development of the Tibetan Plateau.
Paleoenvironmental modelling and physical evidence shows that the climate in
13 Zhada Basin was cold and arid, indistinguishable from the modern. The δ Cpm values of well-preserved vascular plant material increase from -23.4 to -26.8‰ at the base of the
Zhada Formation to as high as -8.4‰ above 250 – 300 m. This shift denotes the 18
expansion of C4 biomass in this high, arid watershed at ~ 7 Ma, and thus corresponds to the C3 – C4 transition observed in Neogene deposits of the northern Indian sub-continent. 19
INTRODUCTION
The Tibetan Plateau occupies the centre of the largest continent – continent collision on Earth and yet is actively undergoing extension (for example, Armijo et al.,
1986; Molnar and Tapponnier, 1978; Taylor et al., 2003). Models invoked to explain the development of the Tibetan Plateau drive our thinking about convergent orogens worldwide. These models make predictions about the elevation history of the plateau (for example, Armijo et al., 1986; Beaumont et al., 2004; DeCelles et al., 2002; Guynn et al.,
2006; Kapp and Guynn, 2004; McCaffrey and Nabelek, 1998; Molnar et al., 1993;
Murphy et al., 1997; Ratschbacher et al., 1994; Rowley and Currie, 2006; Seeber and
Pecher, 1998; Tapponnier et al., 2001). In addition, numerous studies have linked elevation changes on the Tibetan Plateau to changes in precipitation, aridity, and large- scale oceanic and atmospheric circulation patterns (for example, Dettman et al., 2001;
Kroon et al., 1991; Molnar, 2005; Molnar et al., 1993; Quade et al., 1995; Raymo and
Ruddiman, 1992; Ruddiman et al., 1997; Zhisheng et al., 2001). Understanding what drove the Tibetan Plateau to high elevations, and whether those elevations are long lived and stable, is fundamental to understanding the interaction between asthenospheric, lithospheric and climatic processes.
In this paper we present a Miocene – Pleistocene sedimentary record in the Zhada
Basin in southwestern Tibet, representing the first paleoelevation study in western Tibet.
The sediments are rich in well-preserved gastropod shells and plant organic matter. From these archives, we have produced a detailed paleoelevation and paleoenvironmental record. The oxygen isotopic composition of the shells allows us to reconstruct mean 20 watershed elevation through time, after accounting for the major variables that affect the oxygen isotopic system in both the modern and ancient record. The oxygen record shows that Zhada Basin was arid since the late Miocene, and that this part of the Tibetan Plateau stood as high as today, and possibly higher. The carbon record from plant remains shows that C4 plants expanded across at least parts of this high watershed during the late
Miocene. The C4 plant expansion at this time agrees with observations from the Gyirong
Basin and Thakkhola graben in south-central Tibet and Miocene deposits in northern
Pakistan and Nepal (France-Lanord and Derry, 1994; Garzione et al., 2000a; Quade et al.,
1995; Wang et al., 2006).
Previous Paleoelevation Work
There is still not unanimity within the scientific community regarding how to interpret the many complex proxies for Tibetan Plateau paleoelevation (for example,
Molnar, 2005) despite more than two decades of research on the topic. The earliest work on Tibetan paleoelevation indicated a late Miocene or more recent uplift based on fossil, sedimentological, and structural data (for example, Li and Zhou, 2001a; Li et al., 1986;
Liu, 1981; Zhang et al., 1981; Zheng et al., 2000). Quade et al. (1995) used a change from C3 to C4 dominated vegetation in the Himalayan foreland to argue for initiation or strengthening of the Asian monsoon at about 7 Ma. They linked the change in vegetation to Himalayan or Tibetan Plateau uplift, insofar as summertime heating of the air above the high Tibetan Plateau drives current monsoon circulation. This hypothesis was strengthened by the work of Kroon et al. (1991), Prell and Kutzbach (1992) and Prell et 21 al. (1992), which linked increased upwelling in the Arabian Sea at 7.4 – 8 Ma to onset or strengthening of the Asian monsoon.
Evidence developed more recently both supports and contradicts the idea of relatively recent (late Miocene or later) uplift of the Tibetan Plateau. Early in the debate,
Turner et al. (1993) reported late-Miocene, potassium-rich lavas in northern Tibet. Turner et al. (1993) and Molnar et al. (1993) used this to argue for gravitational removal of thickened lithosphere and, by inference, uplift of the Tibetan Plateau. However, subsequent documentation of widely distributed volcanism of Eocene – Miocene age across the plateau (Chung et al., 1998; Ding et al., 2003; Wang et al., 2001) rendered the previous line of evidence more ambiguous. Dettman et al. (2001) argued for an onset of the Asian monsoon by 10.7 Ma by showing that bivalves from the Himalayan foreland show evidence for seasonal oscillations between wet and very arid conditions, implying that strong monsoonal circulation was in place between 10.7 and 3 Ma. Even the occurrence of normal faulting on the Tibetan Plateau, once thought to mark attainment of high elevations at around 8 Ma (for example, Harrison et al., 1992), has been shown to extend to at least the mid-Miocene (for example, Blisniuk et al., 2001).
Recent paleobotanical and stable isotope studies, focused primarily on south- central Tibet, generally point to high elevations in this region since the Eocene –
Oligocene. The earliest quantitative paleoelevation studies on paleosol carbonate,
18 lacustrine micrite and fossil shells obtained very low δ Occ values, indicating high elevations since 10 – 11 Ma in Thakkhola graben (Garzione et al., 2000a; Rowley et al.,
2001), since ~ 8 Ma in Gyirong Basin (Rowley et al., 2001) and since 15 Ma in the Oiyug 22
Basin (Currie et al., 2005). The latter was confirmation of an earlier leaf physiognomy study in the Namling Basin which also indicated high elevations (Spicer et al., 2003).
Stable isotope studies in the Lunpola Basin (Rowley and Currie, 2006), Nima Basin
(DeCelles et al., 2007), and the Tarim and Qaidam Basins (Graham et al., 2005) argued for high elevations on the Tibetan Plateau back to at least the Oligocene.
Wang et al. (2006) recently reinvigorated the argument for a post-mid-Miocene uplift of the southern Tibetan Plateau by presenting carbon isotope data from 7 Ma mammal fossils in the Gyirong Basin (present elevation: 4,200 m, ~600 km east of the
Zhada Basin) demonstrating that C4 plants composed a significant fraction of their diet.
As C4 grasses today are apparently rare above 3,000 m (Lu et al., 2004; Wang, 2003),
Wang et al. (2006) concluded that the southern Tibetan Plateau attained its current elevation within the last 7 million years. However, there is some evidence that C4 plants are present at high elevations on the Tibetan Plateau (Garzione et al., 2000a; Wang et al.,
2008c). The results of paleoelevation studies to date constitute an important beginning to a still spatially and temporally limited picture of Tibetan uplift. In this paper, we present the first paleoaltimetry study from western Tibet and address the conflicting conclusions from stable isotope and paleoenvironmental studies. 23
OXYGEN ISOTOPE PALEOALTIMETRY
Oxygen isotope analysis has emerged as a powerful tool for reconstructing paleoelevations (for example, Blisniuk and Stern, 2005; Chamberlain and Poage, 2000;
Currie et al., 2005; Cyr et al., 2005; Dettman and Lohmann, 2000; Garzione et al., 2000a;
Garzione et al., 2000b; Poage and Chamberlain, 2001; Rowley and Currie, 2006; Rowley and Garzione, 2007; Siegenthaler and Oeschger, 1980). The underlying principle of these reconstructions is that oxygen or deuterium isotopic compositions of meteoric water
18 (expressed as δ Omw or δDmw, respectively, in units ‰) vary as a function of elevation, decreasing by global average values of about –2.8 ‰/km (Poage and Chamberlain,
18 18 2001). In the ideal case, the δ Osw of surface water reflects the average δ Omw of rainfall in the catchment. Carbonates, phosphates, and silicates ultimately derive their O
18 and H from surface water and so record these δ Osw and δDsw values. After correcting for temperature of formation and other factors, paleoelevation can be reconstructed.
18 The δ Omw value of precipitation varies as a function of multiple factors (for example Dansgaard, 1954; Dansgaard, 1964; Drever, 1997; Poage and Chamberlain,
2001; Rowley et al., 2001; Rozanski et al., 1993) resulting in spatial and temporal departures from the modern global average lapse rate. These local variations can potentially be redressed by direct measurement and modelling of local lapse rates. For southern Tibet, this critical information is available (Garzione and others, 2000a; Rowley and others, 2001).
Rayleigh fractionation models describe moist, adiabatically-rising, thermally- isolated packets of air from which any condensation is immediately removed as 24 precipitation. The effect is an open-system distillation process whereby the water vapour
18 content of the air is progressively depleted in H2 O (Rowley and others, 2001;
Siegenthaler and Oeschger, 1980). These models apply to moisture that is orographically lifted up the south side of the Himalaya during the summer monsoon. However, because
Rayleigh fractionation models are one dimensional, they must be calibrated for the many spatial variables that affect air masses and precipitation. By implication, paleoelevation reconstruction requires knowledge of the source of the water vapour in order to rule out recycling from continental water sources or variations in oceanic source regions
(Araguas-Araguas et al., 1998). Continental recycling results in precipitation with
18 anomalous δ Omw values (Dansgaard, 1964; Drummond et al., 1993), as is the case in north-central Tibet. Paleoelevation reconstruction also requires knowledge of moisture pathways, since vapor experiencing a long overland path prior to precipitation (high
18 continentality) will have the same δ Omw value as precipitation at high elevations
(Rozanski et al., 1993). The fractionation factor between liquid and vapour is temperature sensitive and Rayleigh fractionation models are most sensitive to the source region temperature (Rowley and others, 2001; Rowley and Garzione, 2007); therefore it is necessary to be able to constrain paleotemperature. Of the other variables, the amount
18 effect exerts the strongest influence on δ Omw, especially at lower latitudes and in
18 monsoon climates such as in the Himalaya today. In north India today, seasonal δ Omw values vary by up to 10 ‰ (Rozanski and others, 1993; Dettman and others, 2001) owing primarily to the amount effect. 25
18 Additional factors influence the δ Osw values of surface or ground water. The
18 δ Osw value is the result of integrating the precipitation that fell at all elevations in the catchment above the sampling elevation. Thus, the sample represents the precipitation amount-weighted hypsometric mean elevation of the catchment. In small, high-elevation catchments, such as those sampled in Zhada Basin, this value varies little from the area- weighted mean elevation of the catchment (Rowley and Garzione, 2007). Post-
18 precipitation evaporation also increases δ Osw values (Dansgaard, 1964) particularly in areas with long water-residence times (e.g., lakes, marshes). In Tibet, the combination of
18 an arid climate and long water-residence times in lakes can sharply increase δ Osw values of lake water (1.7 to -7.1 ‰, VVSMOW, Quade, unpublished data (Fontes et al.,
1996; Gasse et al., 1991).
18 In order to reconstruct the δ Osw value of water in which minerals formed, we must also know or be able to estimate the temperature at the time of mineral formation and be able to constrain the effects of subsequent diagenesis. Diagenesis can change the
δ18O value of oxygen bearing minerals (Garzione et al., 2004), a potential complication that must be carefully evaluated.
Therefore, before drawing conclusions about paleoelevation and paleoclimate from stable isotope data, the following factors must be accounted for: (1) comparison with modern water to establish the modern lapse rate, (2) proof against diagenesis, and
(3) correction for climate change. The third factor includes identifying and assessing changes in the source region, the amount effect, temperature, and the pathway that the 26 relevant air masses took. Reliable age control must also be established before drawing tectonic implications from paleoelevation reconstructions. 27
REGIONAL SETTING OF ZHADA BASIN
The Zhada Basin is a late-Cenozoic sedimentary basin located just north of the high Himalayan ridge crest in the west-central part of the orogen (~32° N, 82° E, Figure
2.1A). The axis of the basin is parallel to the general arc of the Himalaya which, in this location, is approximately northwest-southeast. The current outcrop extent of the basin fill is approximately 9,000 km2. The basin fill is undisturbed and lies in angular or buttress unconformity with underlying deformed Tethyan Sedimentary Sequence (TSS) strata that were previously shortened in the fold-thrust belt. After deposition, the Sutlej
River incised through to the basement, exposing the entire basin fill in a spectacular series of canyons and cliffs. The presence of a basin above the TSS in this location is in contrast to much of the Himalaya where the TSS caps some of the highest mountains in the world, including Mount Everest.
The Zhada Basin is bounded by the South Tibetan Detachment System (STDS) to the southwest, the Indus Suture to the northeast, and the Leo Pargil/Qusum and Gurla
Mandhata gneiss domes to the northwest and southeast, respectively (Figure 2.1B). The
STDS is a series of north-dipping, low-angle, top-to-the-north normal faults which place low-grade Paleozoic – Mesozoic metasedimentary rocks on high-grade gneisses and granites of the Greater Himalayan sequence. No ages for movement on the STDS in this area have been published, but elsewhere in the orogen ages range from 21 – 12 Ma
(Murphy and Yin, 2003). Although rocks of Indian affinity are separated from those of
Asian affinity by the Indus Suture, the region north of the STDS is considered the southern edge of the Tibetan plateau for this study because it is hydrologically integrated 28 with areas north of the Indus Suture. In the Zhada Basin region the Oligo-Miocene Great
Counter Thrust, a south-dipping, top-to-the-north thrust system, modifies the Indus
Suture (for example Ganser, 1964; Yin et al., 1999). Exhumation of the Leo
Pargil/Qusum and Gurla Mandhata gneiss domes (Figure 2.1B) by normal faulting initiated at ~ 16 Ma and 9 Ma, respectively (Murphy et al., 2002; Thiede et al., 2006) and is ongoing today. The unique setting of Zhada Basin makes it an ideal place to test hypotheses about climate, tectonics and paleoelevation in the Himalaya and southwestern
Tibet.
We measured 14 stratigraphic sections covering the basin extent from the Zhada county seat in the southeast to the Leo Pargil/Qusum rangefront in the northwest (Figure
2.1B). The basin fill consists of approximately 800 m of fluvial, lacustrine, eolian and alluvial fan deposits and is divided broadly into 3 intervals.
1) The lower part of the section consists of ~ 200 m of trough cross-bedded sandstone and well-organized, imbricated pebble to cobble conglomerate. Broadly lenticular bodies of sandstone and conglomerate are interpreted as channel fills. The presence of 3-4 m thick cross-stratified bedsets in these channel fills suggests the presence of deep channels and large mid-channel macroforms. We interpret these as fluvial deposits laid down by large-scale rivers ancestral to the Sutlej or Indus based on provenance and paleocurrent orientation data. Interbedded with these lithofacies are fine- grained, laminated sandstone and siltstone layers showing extensive soft-sediment deformation. These units contain abundant mammal, gastropod and plant fossils. We 29 interpret these fine-grained intervals as marshy bog or overbank deposits within a low- gradient fluvial setting.
2) The approximately 250 m thick middle unit consists of an upward coarsening succession of cycles. Individual cycles are up to 17 m thick, coarsen upward, and contain profundal lacustrine claystone in their lower part and deltaic and wave-worked sandstone and conglomerate in their upper part. The claystone is devoid of macrofossils but the sandstone often has well-preserved, robust gastropod shells. Evidence of desiccation episodes, including gypsum layers and mudcracked mud-flat facies, is also present in the middle unit interval. Upward coarsening cycles are interpreted as progradational lacustrine sequences.
3) The upper 350 m of the Zhada Formation continues the upward coarsening progression displayed in the middle unit but becomes much coarser. The profundal claystone facies is replaced by deltaic or lake margin deposits. Individual parasequences contain lake-margin and alluvial-fan and fan-delta conglomerates.
30
METHODS AND MATERIALS
Age Control
We sampled the entire thickness of two measured sections and a portion of a third for magnetostratigraphic analysis, for a total sampling thickness of ~ 1400 m. We collected 4-5 samples from 184 sites (102 from the South Zhada section, 5 from the East
Zhada section, and 77 from the Southeast Zhada section) using a cordless, hollow-bit drill using standard paleomagnetic sampling techniques (Butler, 1992). Samples were stored in a magnetically shielded room (~300 nT background field) housing the cryogenic magnetometer and demagnetization equipment, for at least 72 hours prior to measurement of natural remnant magnetization (NRM) and throughout the analysis process. We measured NRM using a 2G Model 755R three-axis cryogenic magnetometer with in-line degaussing system and automated sample handler. All cores were analyzed prior to any heating to isolate NRM. Using furnaces with programmable temperature controllers and ten thermocouple temperature sensors on each sample rack, we thermally demagnetized one sample from each site with temperature steps as follows: 50 degree steps from 100-
300ºC, 20 degree steps from 300-400ºC and 20 degree steps from 500-700ºC. We based temperature steps for subsequent batches on these initial results. Temperature steps within 100 degrees of the Curie temperature were 20 degrees for all batches (see Figure
2.2 for representative vector diagrams). Characteristic Curie temperatures were between
580 ºC and 700ºC, indicating that magnetite and hematite were the primary carriers of characteristic remnant magnetization (ChRM). However, magnetic intensity in a 31 minority of the samples decreased markedly by 300ºC, indicating the possible presence of goethite.
The principle component analysis was done using the origin as a separate data point (―origin‖ line fit of Butler (1992)) and using at least 4 temperature steps. We discarded samples with line fits yielding a maximum angular deviation of >15º from further analyses. We then plotted site averages for sites with samples that passed the maximum angular deviation test on an equal area stereonet and calculated mean vectors for normal and reversed sites. The mean vectors for both the South Zhada and Southeast
Zhada measured sections were antiparallel and thus passed the reversals test (Figure 2.3;
Butler, 1992).
Most samples show essentially univectoral decay of NRM toward the origin of the vector endpoint diagram. In order to eliminate potentially inaccurate results, we divided the sample set into quality sets A, B, C, and D (Figure 2.2). Sites with > 3 samples which passed the maximum angular deviation test and with a site-mean clustering of ChRM which yielded a 95% confidence limit (α95) ≤ 15º and K ≥ 30 were then designated class
A sites. Sites with ≥ 3 samples and with a site-mean clustering of ChRM which yielded a
95% confidence limit (α95) > 15º were designated class B sites. Sites with 2 samples which yielded consistent inclinations and declinations were designated class C sites.
Sites with only 1 sample which passed the maximum angular deviation test or with 2 samples which yielded inconsistent inclinations or declinations were not included in the magnetostratigraphic column (D sites). We constructed the resultant magnetostratigraphic columns from 87 class A sites, 60 class B sites and 7 class C sites. 32
Magnetic reversals were placed mid-way between adjacent data points with opposite polarities. The placement of some reversals based on a single site is warranted given our caution in processing multiple samples from each site and discarding sites where data were suspect.
Modern Water
We collected 28 water samples at 20 locations throughout Zhada Basin (Figure
2.1B, Table 2.1), providing the densest sampling coverage for any area in Tibet outside of
Lhasa. Several sites were resampled during consecutive years. Samples were collected from a number of different settings ranging from the Sutlej main stem to small seep springs at the base of the Zhada Formation. Virtually no local rain fell during the sampling campaigns, meaning we were sampling higher elevation run-off. ArcGIS was used to delineate watersheds for each of our samples. This allowed calculation of the average elevation at which precipitation feeding these streams and springs fell by obtaining hypsometric mean watershed elevations for each sample. This approach is consistent with the work of Garzione et al. (2000b), Rowley et al. (2001), Rowley and
Garzione (2007), Blisniuk and Stern (2005) and oxygen isotope paleoaltimetry theory
(see section OXYGEN ISOTOPE PALEOALTIMETRY).
We also collected modern water samples from modern wetlands and a Tsangpo
River tributary near Zhongba ((N29 ° 39.754’, E84° 10.056’, 4 569 m, Figure 2.4, Table
2.1). Water was collected from ponds, from which we collected modern gastropod samples (see section below), on the 18th of May and on the 26th of July, 2006. Water 33 sample 180506-4 was collected with gastropod sample TSP16 and sample 180506-5 was collected with TSP18. Wetland ponds are < 100 m in diameter and < 0.5 m deep and are inset into both exhumed paleowetlands and modern dune fields. On the 26th of July we also collected water from the Tsangpo tributary. The river water collection location was within 10 km of the wetland water and gastropod collection sites for samples 260706-3,
180506-4 and TSP16 and, in the absence of alternative sources, is inferred to be the source water for the wetlands.
Waters were analyzed for δDsw values using a dual inlet mass spectrometer
(Delta-S, Thermo Finnegan, Bremen, Germany) equipped with an automated chromium reduction device (H-Device, Thermo Finnegan) for the generation of hydrogen gas using
18 metallic chromium at 750°C. Water δ Osw values were measured on the same mass spectrometer using an automated CO2-H2O equilibration unit. Standardization is based on internal standards referenced to VVSMOW and VSLAP. Precision is better than ±
0.08‰ for δ18O and ±1‰ for δD.
Gastropods
We sampled fossil gastropods in two measured sections spanning the lower ~ 650 m of the Zhada Formation. No gastropod samples were found above ~ 650 m. Shell fragments and intact shells were collected from fluvial, marshy, and lacustrine intervals.
We analyzed both homogenized gastropod shell material and micro-drilled gastropod shells to obtain seasonal information. To check for preservation of biogenic aragonite, 12 representative gastropod samples from fluvial, lacustrine and marshy intervals were 34 powdered and analyzed using the University of Arizona’s D8 Advance Bruker X-ray powder diffractometer.
We also collected gastropod shells from modern wetlands near Zhongba on the
Tsangpo River (N29 ° 39.754’, E84° 10.056’, 4 569 m, Figure 2.4). Gastropod shells were collected from the shore of wetland ponds on the 18th of May, 2006. Gastropods were recently living and appeared to have died as the water table dropped. We analyzed one homogenized shell sample and microdrilled another at 0.3 mm increments.
18 13 We measured δ Occ and δ Ccc values of shell material using an automated carbonate preparation device (KIEL-III) coupled to a gas-ratio mass spectrometer
(Finnigan MAT 252). Powdered samples were reacted with dehydrated phosphoric acid under vacuum at 70°C. The isotope ratio measurement is calibrated based on repeated measurements of NBS-19 and NBS-18 and precision is ± 0.1 ‰ for δ18O and ±0.06‰ for
δ13C (1 ).
Zhada Formation Plant Material
We analyzed 36 samples of organic matter from 29 stratigraphic intervals in two measured sections. Fossil plant material obtained from our sections is both fragmentary and locally carbonized, but often preserves primary epidermal cell tissue. Much of this fossil plant material appears to be grass bladelets rather than leaves or twigs. Organic material was reacted with sulfurous acid in silver foil boats at least twice to remove
13 carbonate material prior to drying at 60°C. We measured the δ Cpm values of plant material on a continuous-flow gas-ratio mass spectrometer (Finnigan Delta PlusXL). 35
Samples were combusted using an elemental analyzer (Costech) coupled to the mass spectrometer. Standardization is based on NBS-22 and USGS-24 for δ13C. Precision is better than ± 0.06 for δ13C (1 ), based on repeated internal standards. 36
RESULTS
Age
We used several temporal anchors independent of magnetostratigraphy to constrain the magnetostratigraphic correlations. The first was the occurrence of
Hipparion fossils at 310 m in our East Zhada measured section and at 240 m in our South
Zhada measured section. Pilbeam et al. (1996) placed the first appearance of Hipparion
(the Hipparion datum) at 10.7 – 10.8 Ma in northern Pakistan. Hipparion radiated quickly (Woodburne et al., 1996; E. Lindsay, pers. comm.), thus the onset of sedimentation in Zhada Basin must be no earlier than 10.7-10.8 Ma. Additional Zhada fauna include Hipparion zandaense, Nyctereutes, and Paleotragus microdon (Li and Li,
1990; Zhang et al., 1981; X. Wang, pers. comm.). This biostratigraphic evidence constrains basin filling at Zhada to the late Miocene – Pliocene.
13 A shift in δ Cpm values was observed in two of our sections (Figure 2.5). The
13 δ Cpm values of plant organic matter are determined by the metabolic pathway that the plant used. C3 plants, mostly trees, shrubs and cool-growing-season grasses respire CO2
13 with δ C values which average -27 ± 6 ‰ globally. C4 plants, including some shrubs,
13 but primarily warm-growing-season grasses respire CO2 with δ C which average -13 ± 3
‰ globally (Ehleringer et al., 1991). Quade et al. (1995; 1989) and France-Lanord and
13 Derry (1994) showed a marked shift in δ Cpm values in paleosol carbonate and plant material in the Indian subcontinent at ~ 7 ± 1 Ma. They attributed this shift to a change from C3 to C4 dominated plants. In far western Nepal, ~300 km SSE of Zhada Basin,
Ojha et al. (2000) place the C3 – C4 transition at 7 Ma. Garzione et al. (2000a) used this 37 same shift in the Thakkhola graben in the southern Tibetan Plateau (500 km SE of Zhada
Basin) as an anchor for their magnetostratigraphic correlation. Finally, the presence of
C4 plants in the diet of fossil herbivores was used as independent confirmation of the post
7 – 8 Ma age of the fossils in Gyirong Basin (Wang et al., 2006).
We first correlated our South Zhada (SZ) and Southeast Zhada (SEZ) magnetostratigraphic sections using the capping geomorphic surface as a datum (Figure
2.6A). This surface is correlative across the basin and marks the maximum extent of sedimentation prior to incision and exhumation by the Sutlej River. This approach assumes that the geomorphic surface is isochron. The validity of this assumption is based on the interpretation of the geomorphic surface as a depositional surface that extended across the basin just prior to incision and abandonment. The assumption is also based on the gross similarities between the upper portions of the South Zhada and Southeast Zhada magnetostratigraphic (and lithologic) sections. Working downward from the datum, the longest normal and reversed polarity intervals were correlated between the two sections.
A composite magnetostratigraphic column was then created that incorporated both long polarity intervals and also the shorter polarity intervals from both sections (Figure 2.6B).
This approach assumes that whereas the shorter polarity intervals may have been missed in one or the other section, the longer polarity intervals were not. Combining data from both magnetostratigraphic sections produces a composite magnetostratigraphic section that is more detailed than either of the individual sections (Figure 2.6B).
The mammal megafaunal fossil anchor described above and the number of polarity chrons in the composite section indicate that sedimentation extended from the 38 late Miocene to the Pliocene or Pleistocene. Within these constraints we correlated the composite section with the Global Polarity Time Scale (GPTS) of Cande and Kent
(1995). Intervals P+ through T+ likely correlate with either chron 2An or 3n (Figure
2.6C, E, G). We favour the correlation in figure 2E for several reasons. This correlation
(1) accounts for all of the normal and reversed intervals, (2) places the C3 – C4 transition at ~ 7 Ma, which is consistent with its age elsewhere, and (3) yields relatively constant and reasonable sedimentation rates. The alternative correlations have several drawbacks.
The correlation in figure 2.6C means that the upper geomorphic surface is ~ 3 Myr old and yet shows no evidence for significant erosion. The correlation of chrons 3r – 4n is equally problematic in correlation G as evidenced by the large excursions in the sediment accumulation rates (Figure 2.6H). With those considerations, the base of the composite section most reasonably correlates to chron 4Ar.1 and the top of the section to chron 1n
(Figure 2.6E). This corresponds to an absolute age interval of < 1 – 9.2 Ma (Cande and
Kent, 1995). While the correlation in figure 2.6E is favoured, both E and C place the onset of sedimentation at ~ 9.2 Ma. The onset of sedimentation in both correlations E and C is consistent with an independent magnetostratigraphy study conducted by Wang et al. (2008b). They differ significantly only in the upper portion, which is not the focus of this paper.
Modern Water
18 Modern δ Osw (surface water) values range from -17.9 to -11.9 ‰, and δDsw values from -137 to -86 ‰ (VSMOW, Figure 2.7, Table 2.1) for water from the Zhada 39
Basin. The lowest values coincide with small springs draining catchments in the
18 Himalaya to the south of Zhada Basin. The average δ Osw value of the water coming from the Ayi Shan, to the north of Zhada Basin (Figure 2.1B), is slightly higher than for
18 water coming from the Himalaya (-14.1 and -15.3 ‰, respectively). The average δ Osw value of water from the Sutlej River main stem (-15.1 ‰) reflects input from both of
18 these sources. The modern δ Osw values for water from the Zhongba area range from -
18.9 to -3.9 ‰ and δDsw values range from -140 to -86 ‰ (VSMOW, Figure 2.7, Table
2.1).
Gastropods
XRD analysis from 11 of 12 samples yielded only aragonite peaks (Figure 2.8).
One sample was too small to yield results and was removed from further consideration.
18 The δ Occ values of samples that we analyzed using X-ray diffraction ranged from -20.3 to 0.2 ‰ (VPDB).
13 δ Ccc (carbonate) values of gastropods range from -13.8 to 7.5‰ (Table 2.2).
13 18 Consideration of the data as a whole shows clear covariance between δ Ccc and δ Occ values (R2 value of 0.61 for the South Zhada section and 0.62 for the East Zhada section;
Figure 2.9). Dividing the data by lithofacies reveals a more complex pattern (Figure 2.9).
13 δ Ccc values of samples from fluvial intervals range from -13.8 to -2.6‰ and show almost no covariance (R2=0.03 for South Zhada section and R2 = 0.06 for the East Zhada
13 section). δ Ccc values of samples from supralittoral/marshy intervals range from -13.8 to
+7.5‰ and display significantly more covariance (South Zhada R2=0.36 and East Zhada 40
2 13 R = 0.19). Samples from littoral intervals yield δ Ccc values of -3.8 to +3.0‰ and
R2=0.30 for South Zhada and 0.08 for East Zhada. Finally, samples from profundal
13 lacustrine intervals, which only occur in the South Zhada section, yield δ Ccc values of -
3.0 to +1.9‰ with R2=0.00.
18 δ Occ values of gastropods from fluvial intervals range from -21.4 to -9.9‰
(VPDB); from supralittoral/marshy intervals between -21.6 to -1.8‰; from littoral intervals, -9.3 to +0.7‰ and from profundal intervals, -3.2 to +0.3‰ (Table 2.2, Figure
18 2.10). Finally, microdrilled samples show a range of δ Occ values, typically ~ 3‰ but up to 10.9‰, from a single sample (Figure 2.11). All the snails are aquatic.
18 δ Occ values of modern gastropods from Zhongba range from -12.0 to -14.7 ‰
13 (VPDB) and δ Ccc values range from -3.6 to -11.2 ‰ (VPDB). The two samples do not show an obvious covariant trend, though sample TSP18 may show internal covariance
(Figure 2.9).
Zhada Formation Plant Material
13 δ Cpm values range from -23.4 to -26.8‰ (VPDB) in the lower 250-300 m of both sampled sections, and increase to as high as -8.4‰ (VPDB, Table 2.3, Figure 2.5) above 300 m. 41
APPLICATION TO PALEOALTIMETRY
18 Calculation of Miocene δ Osw and Related Constraints and Corrections
Source, pathway and amount effect constraints
Applying the modern δ18O versus elevation lapse rates to the Miocene requires accounting for potential climate change in the intervening time. Currently, the Indian subcontinent’s summer monsoon derives its water vapour from the Arabian Sea and
Indian Ocean. Source region temperatures effect the δ18O values of high-elevation carbonates in two ways: 1) sea surface temperatures effect the δ18O value of source region water vapour (Blisniuk and Stern, 2005; Jouzel et al., 1997), and 2) low-elevation temperatures effect the δ18O versus elevation lapse rate (Rowley and Garzione, 2007;
Rowley et al., 2001). Modern mean annual temperature (MAT) for the low-elevation
Himalayan foreland is 25 ºC or 27 – 28 ºC for coastal IAEA/WMO GNIP stations
(Mumbai and Calicut; IAEA/WMO, 2007). Current MAT is close to the MAT of 26.5 ºC calculated from Miocene soil carbonate nodules in western Nepal (Quade et. al., 1995), as well as MAT estimates based on fossil flora assemblages (for example, Awashi and
Prasad, 1989; Sarkar, 1989). Lower low-elevation temperatures would elevate the δ18O versus elevation lapse rate hence reconstructed paleoelevations would overestimate paleoelevation. As noted above, neither regional nor global late temperature estimates indicate an increase in temperature between the late Miocene and the modern (Zachos et al., 2001). Miocene sea surface temperatures have typically been thought to be ~ 10° C cooler than the modern (Kennett, 1985; Savin et al., 1985; Williams et al., 2005). Lower
Miocene sea surface temperatures would result in low-elevation water vapour with higher 42
δ18O values hence reconstructed paleoelevations would underestimate the actual paleoelevation. However, there is debate whether measured δ18O values represent sea surface temperatures or the bottom temperature during early diagenesis (for a brief summary see Pearson et al., 2002; Zachos et al., 2002). This raises the possibility that
Miocene Indian Ocean sea surface temperatures were comparable to the modern (Stewart
18 et al., 2004; Williams et al., 2005). Additionally, average paleosol δ Occ values from
Neogene deposits at low elevation in the northern Indian sub-continent show no change post-8 Ma (Quade et al., 1995). Araguas-Araguas et al. (1993, Figure 1) indicate that moisture up to and just north of the crest of the Himalaya is dominated by moisture from the Indian summer monsoon. The Zhada basin is located just north of the crest of the
Himalaya and all drainages on the southern side of the basin are sourced by glaciers that originate at the foot of high Himalayan peaks to the south. The implication is that at least half the water in the basin is coming from the Himalaya. According to Tian et al. (2001), rainfall with high deuterium-excess (d-excess) values in the Himalaya and just north of the Himalaya is derived from the Indian summer monsoon. Water from the Zhada basin has d-excess values of between 3 and 15 (mean: 10) which is consistent with derivation from the Indian summer monsoon. Finally, the Zhada basin is located far to the west of the range of penetration of Pacific moisture onto the Tibetan Plateau (Araguas-Araguas et al., 1993, Figure 1).
Paleosols from northern India would have experienced the same climate changes and changes in source water δ18O values as the Zhada samples, since northern India is dominated by the same monsoon climate system (Araguas-Araguas et al., 1998; Dettman 43
18 et al., 2001; Tian et al., 2001). As no significant change in MAT or δ Occ values is evident from the low-elevation late Miocene records, we apply current climatic
18 conditions in reconstructing δ Opsw (paleo-surface water) values. Since the monsoon seems to have been established by at least 10.7 Ma (Dettman and others, 2001), the same source and pathway applies for Miocene Zhada meteoric water as for modern Zhada meteoric water. This suggests that we can use the modern δ18O versus elevation relationships, as measured by Garzione and others (2000b) and modelled by Rowley and others (2001), to understand the ancient record.
Shell preservation
We are confident that gastropod samples are unaffected by diagenesis and retain
18 their original δ Occ values for the following three reasons: (1) all of the samples which returned usable X-ray diffraction results (11 of 12) were aragonite (Figure 2.8), and none showed evidence of recrystallization; (2) the samples are visually pristine, retaining a pearly luster in the interior and obvious growth bands; (3) samples which we microdrilled showed seasonal variation (Figure 2.11). Such internal variation would not be expected
18 if the samples were overprinted by a regional δ Osw value during diagenesis. The results from this representative sampling can be confidently applied across the basin because the sediments were never buried below ~ 800 m and so are not subject to regional metamorphism or hydrothermal alteration.
18 Calculation of Miocene δ Opsw
18 18 δ Opsw values were reconstructed from δ Oar values using: 44
18 18 6 -2 δ Opsw (VSMOW) = [(1000 + δ Occ (VSMOW)) / [exp [(2.559 * 10 * T +
0.715] / 1000)]]] – 1000
(1)
(Dettman et al., 1999; modified from Grossman and Ku (1986)) where T (in K) is the temperature of CO3 precipitation. We used the modern temperature to constrain the temperature of aragonite precipitation (see section Source, pathway and amount effect constraints). The nearest weather station for which there are long term records is at
Shiquanhe (32.5ºN, 80.083ºE, 4280 m) (NCDC, 2007). MAT at Shiquanhe for the period between 1969 and 1990 is 0°C. Assuming that gastropods grow dominantly during the warmer months, we calculated the average temperature for the months of April – October
(months when Taverage > 0°C) and set T = 7°C. Warmer temperatures produce higher
18 δ Opsw values, thus minimizing paleoelevation estimates. Intrashell variation of ± 1.5 ‰ corresponds to a seasonal variation of ± 7°C and that uncertainty is applied to all samples
(Figure 2.12).
Comparison with Models
Effect of paleotemperature
18 One possible explanation for the extremely low δ Occ value of gastropod aragonite (Figure 2.12) is that it was precipitated in warm water. If we assume no change
18 18 in δ Osw values of water in the Zhada region (i.e., that the most negative δ Osw value of modern Zhada water (-17.9 ‰ VSMOW) is representative of the water in which Miocene
– Pleistocene gastropods lived), we can use the fractionation factor between that water 45
18 and the gastropod aragonite δ Occ value (-21.6 ‰ VPDB) to calculate the temperature of precipitation. However, this exercise yields an unrealistic temperature of aragonite precipitation of 41° C. Thus, the temperature of aragonite precipitation alone cannot
18 explain the extremely negative δ Occ values.
Modelling changes in lapse rate
18 By changing input parameters for the thermodynamically based δ Osw versus elevation models (Rowley and Garzione, 2007; Rowley et al., 2001) we can evaluate the effect of 1) changes in monsoon intensity on the δ18O versus elevation lapse rate and 2) changes in low-elevation temperature. We first looked at the effect of increasing monsoon intensity on the δ18O versus elevation lapse rate. We calibrated the model by finding the low-elevation temperature that produces a lapse rate that is consistent with the most negative modern Zhada water (-17.9 ‰ VSMOW with a mean catchment elevation of 5,419 m). This yielded a low elevation temperature of 297.5 K. While maintaining the low elevation temperature at 297.5 K, we artificially decreased the saturation vapor pressure of the system to find a model lapse rate that places the reconstructed Miocene water value at 5,419 m. Decreasing the saturation vapor pressure artificially forces
18 increased precipitation, and thus decreased δ Osw values, at lower elevations. The best fit was found when the saturation vapor pressure was decreased by 30%. However, there is
18 18 no evidence from lowland δ Occ records of changes in δ Osw values consistent with a saturation vapor pressure shift of this magnitude (Dettman et al., 2001; Quade et al.,
1995). 46
We also considered changes in low elevation temperature. Assuming that the δ18O value of the reconstructed Miocene – Pleistocene water from Zhada Basin (-24.5 ‰
VSMOW, Figure 2.12) is accurate, we changed the low elevation temperature to find a model lapse rate which places that δ18O value at 5,419 m. A match was found at a low elevation temperature of 293 K, a decrease of 4.5 ° C from the modern. This decrease in
18 temperature should show up in the low-elevation δ Occ and paleobotanical records and in
18 the climate record in Zhada Basin. However, as noted above, the low-elevation δ Occ and paleobotanical records post-8 Ma are consistent with the modern. Moreover, global climate is thought to have cooled between the Miocene and the present, not warmed as would be required by this scenario (for example Zachos et al., 2001).
Evaporation vs. Outflow
18 Comparing δ Occ values from fluvial and lacustrine gastropods allows reconstruction of local climate conditions if we can estimate outflow from the basin. All
18 δ Occ values are given referenced to VPDB and, as we are interested in the difference between two δ18O values, there was no need to change them to values referenced to
18 VSMOW. We used -21.6 ‰ (VPDB) as our inflow value, based on the δ Occ values of
18 the fluvial fossil mollusks. The range of δ Occ values of -3.3 ‰ and -0.4 ‰ (VPDB) for
18 lacustrine mollusks corresponds to δ Osw values of -6.2 and -3.3 (VSMOW), respectively, (assuming a temperature of precipitation of 7 ºC). These paleo-lake water
δ18O values are within the range of -7.1 to +1.7 ‰ (VVSMOW) observed in modern lakes on the Tibetan Plateau (Fontes et al., 1996; Gasse et al., 1991)(Quade, unpublished 47
data). The range of total isotopic enrichment values (εw-v = 18.7 – 21.7) was calculated
18 18 based on our inflow δ Occ value and the range of lacustrine δ Occ values.
We compared the calculated Miocene isotopic enrichment values to modelled modern isotopic enrichment values for relative humidity values between 0 and 70 % and temperatures between 0 and 10 °C. The modern average relative humidity is 30%, reaching a maximum of 50% during the monsoon. The modern MAT is 0 °C, average temperature between April and October is 7 °C, maximum monthly temperature is 14 °C and the maximum temperature between 1961 and 1990 is 21 °C.
The toal isotopic enrichment, εw-v, is a function of both the equilibrium water – boundary layer enrichment (εw-bl) and a kinematic enrichment (εbl-v). We calculated the kinetic enrichment during evaporation using the equation:
εbl-v=14.2 (1-rh),
(2) where εbl-v is the enrichment in ‰ between a saturated boundary layer above the water surface and a well-mixed vapor column and rh is the relative humidity fraction
(Gonfiantini, 1986). The δ18O value of evaporation was calculated using a simple mixing equation such that
18 18 18 δ Oevap = (δ Oinflow – f * δ Olake)/(1 – f))
(3) where f is the outflow fraction. We assume that f = 0.
The equilibrium enrichment was calculated using:
18 6 2 3 1000lnα(δ Ow-bl) = 1.137(10 /T ) – 0.4156(10 /T) – 2.0667 48
(4)
(Majoube, 1971) where T is temperature in Celsius.
One source of uncertainty is whether or not the basin was closed. Increasing the outflow fraction would result in increasing the total (outflow + evaporative) isotopic
18 enrichment. The δ Occ record in closed-basin gastropod shells could easily be identical
18 to δ Occ values for open-lake gastropod shells if conditions were cooler or drier. Hence,
18 we are unable to determine whether or not outflow has occurred from the δ Occ values.
However, the occurrence of mudcracks and bedded gypsum in the sedimentary sections,
18 13 in addition to the covariance between δ Occ and δ Ccc values, suggests that Zhada Basin was at least periodically, if not continually, closed during lacustrine sedimentation.
The results of modelling the relative humidity, isotopic enrichment, and temperature confirm that there is a limited range of reasonable values for all of these variables and that range is consistent with the modern climate in the area (Figure 2.13).
Temperature of Modern Gastropod Shell Precipitation
18 The δ Occ values of modern gastropods from near Zhongba, coupled with the
18 δ Osw values of water in which those gastropods lived, allows calculation of a fractionation factor and hence a temperature of aragonite precipitation. In the following
18 discussion ―pre-monsoon wetland water‖ refers to water with δ Osw values of between -
18 3.9 and -6.3 ‰ (VSMOW) and ―monsoon wetland water‖ refers to water with δ Osw values of -16.6‰ (VSMOW). We first assumed that the gastropods precipitated their shells in equilibrium with the pre-monsoon wetland water they were near on the date of collection (18th May, 2006). However, this results in unreasonably high temperatures of 49 aragonite precipitation (Figure 2.14). Alternatively, assuming that the gastropods precipitated their shells in equilibrium with monsoon wetland water (sample 260706-3) results in temperatures between ~ 0 – 12 °C (Figure 2.14). These temperatures are between MAT and the maximum average monthly temperature for the period 1961 –
1990 as recorded by the Shiquanhe weather station.
We can calculate the relative contribution of oxygen from pre-monsoon and monsoon wetland water to shell aragonite if we assume a range of temperature of aragonite precipitation of 0 – 12 °C. We used a simple mixing ratio between aragonite precipitated in equilibrium with monsoon and pre-monsoon wetland waters at 0 and 12
18 °C. Applying this calculation to sample 180506-4 shows that shell δ Occ values of -12
‰ (VPDB) require that the shells are 100 % aragonite precipitated in equilibrium with monsoon wetland water at 0 °C or ~ 70 % aragonite precipitated in equilibrium with monsoon wetland water at 12 ° (Figure 2.15). A similar calculation for sample 180506-5
18 (average δ Occ value ~ -14 ‰ VPDB) shows that if the average temperature was 0 °C the
18 shell must have been precipitated in water with δ Osw values more negative than observed monsoon wetland water, or, if the average temperature was 12 °C, the aragonite was precipitated in equilibrium with 100 % observed monsoon wetland water at (Figure
2.15).
Paleoelevation models
18 18 We compared the most negative δ Osw and reconstructed δ Opsw values to
18 Δδ Osw versus elevation relationships based on both a simple Rayleigh fractionation model (Rowley and Garzione, 2007; Rowley et al., 2001) and an empirical data set 50
18 (Garzione et al., 2000b). In calculating Δδ Osw, we used the modern, low-elevation
18 δ Omw value for New Delhi of -5.8 ‰ (VSMOW, Rozanski et al., 1993) and a Miocene
18 low-elevation δ Occ value of -6.0 ‰ (VSMOW) from paleosols from the Siwalik Group of Pakistan and Nepal (Quade et al., 1995; Dettman et al., 2001). Uncertainties in our
18 Δδ Opsw value derive from a ± 0.5 ‰ uncertainty due to variation in the most negative
18 values of δ Occ in Miocene low-elevation paleosol carbonates between western Nepal and Pakistan (Quade and others, 1995), and ± 1.5 ‰ uncertainty due to seasonal changes
18 in the temperature of aragonite precipitation (see section Calculation of Miocene δ Opsw).
Additional uncertainty in paleoelevation estimates potentially arises from variability in the low-elevation temperature or humidity (Rowley and others, 2001;
Rowley and Garzione, 2007). Modern surface water sampled in this study integrates multiple glacial sources and groundwater. Hence these samples do not represent a single precipitation event but rather a temporal average. Variability in modern samples that are derived from the same sources and are collected at the same elevation (see for example
Figure 2.16), interpreted in terms of low-elevation temperature or humidity would lead to the conclusion that temporally averaged low-elevation temperature or humidity had varied dramatically. As this degree of variability in low-elevation parameters is not observed currently, we conclude that this approach incorrectly attributes variability causation. Hence, in our calculation of paleoelevation we use only the variability inherent in the reconstructed water Δδ18O.
18 The modern water samples fall above the Δδ Osw versus elevation curves based on both Rayleigh fractionation (with an initial, low-elevation temperature (Ti) = 295 K, 51 and initial relative humidity (rh) = 0.8) and empirical data from Nepal (Figure 2.16). The implication is that a calculated paleoelevation based on either of these curves will be a
18 minimum. Δδ Osw values of modern water samples fall between a variation of the
Rayleigh fractionation model with Ti = 303 K and rh = 0.8, and the models described above. A low elevation Ti = 300 K and rh = 0.8 is consistent with modern, coastal MAT in the region. The modified Rayleigh fractionation model yields a best-fit polynomial of
z = -0.0014 (Δδ18O)4-0.488(Δδ18O)3-30.88(Δδ18O)2-814.19(Δδ18O),
(5) where z is elevation in meters. A low-elevation temperature Ti = 303K and rh = 0.8 most
18 closely matches the Δδ Osw versus elevation relationship defined by the maximum catchment elevation of the Zhada water samples. This relationship yields a best-fit polynomial of
z = 0.011(Δδ18O)4+0.041(Δδ18O)3-29.22(Δδ18O)2-927(Δδ18O).
(6)
We applied the Rayleigh fractionation models with Ti = 295 K and Ti = 300 K and the empirically based model to our data in order to compare the elevations predicted by
18 18 Δδ Osw values of modern water with those predicted by the Δδ Opsw values of our reconstructed Miocene – Pleistocene water. Whereas the absolute elevations of our modern water samples do not match those predicted by several of the models (Figure
2.16), we are interested – at this point – in the difference in elevation predicted by the models. 52
In all three of the models there is a difference in predicted elevations between our
18 18 most negative δ Opsw value and our most negative δ Osw values that is greater than the uncertainty associated with those data points (Figure 2.17). The Rayleigh fractionation
18 model with Ti = 295 K yields a minimum predicted elevation from Δδ Opsw values
(mean elevation – uncertainty) of 5.6 km and a predicted elevation for the modern water sample of 4.8 km. This adds up to an elevation decrease of at least 0.8 km since the late
Miocene. Doing the same calculation for either the Rayleigh fractionation model with Ti
= 300 K or the empirically based curve results in a minimum elevation decrease of at least 1 km or 1.2 km, respectively. More realistically, comparing the mean values for
18 each of the Δδ Osw versus elevation curves yields elevation decreases of 1.0 ± 0.2 km,
1.2 ± 0.2 km and 1.5 + 0.3 - 0.4 km for the Rayleigh fractionation models with Ti = 295
K and Ti = 300 K and the empirically based curve, respectively. Although the models are inconsistent with regards to absolute elevation, yielding an inter-model range of elevations (z) of 1.4 km for modern water and 1.6 km for reconstructed water, they are relatively consistent with regards to differences in elevation (Δz), yielding an inter-model range of only 0.5 km.
The calculations above suggest that paleoelevations during the late Miocene were higher than those today, but they do not consider the effects of 20th century climate
18 change. The Siwalik paleosol record does not display any change in average δ Omw values over the past ~ 8 Ma. However, the record does not cover the last ~ 100 years, a
18 time of apparently major changes in δ Omw water values in this region. Thompson et al.
(2000) noted a 3‰ increase in δ18O values from the Dasuopu glacier in the Himalaya 53 starting in the 20th century. This is consistent with, though larger than, increases observed at Dunde, Guliya and the Far East Rongbuk glaciers (Kang et al., 2001;
Thompson et al., 1997; Thompson et al., 2000) in the northeastern and northwestern
Tibetan plateau and north-central Himalaya, respectively. As all applicable models have been developed with reference to the modern system, we add 3‰ to our reconstructed
Miocene water values in order to compare them to modern water δ18O values (Figure
2.17). Even with this correction the models still yield a minimum elevation decrease
(mean elevation – uncertainty) between the Miocene and modern of at least 0.3, 0.4 and
0.5 km for the Rayleigh fractionation models with Ti = 295 K and Ti = 300 K and the empirically based curve, respectively. Again, comparing mean Miocene model elevations to modern model elevations predicts decreases of 0.6 + 0.2 – 0.3, 0.8 ± 0.3 and 0.8 + 0.3 -
0.4 km for the Rayleigh fractionation models with Ti = 295 K and Ti = 300 K and the empirically based curve respectively. We caution that the addition of 3‰ to our Miocene
18 Δδ Opsw may not be warranted, as interpretation of the glacial record remains unclear
18 and the inferred increase in δ Omw values may be due to a short-term, transitory change.
18 However, as noted above, without the correction for changes in δ Omw values of modern water, our estimates of paleoelevation would increase by ~ 0.5 – 0.7 km.
The approach above results in a minimum estimation of paleoelevation uncertainty and deviates significantly from the approach to uncertainty estimation in previous paleoelevation studies. In order to facilitate comparison with previous
18 paleoelevation studies, we compared the range of modern fluvial Δδ Osw and Miocene
18 fluvial Δδ Opsw values, uncertainties associated with those values, and typically cited 54 model 2ζ uncertainties (Figure 2.18). There is considerable overlap in Δδ18O values.
18 Elevated Δδ Opsw likely reflect evaporative enrichment and emphasize that the Miocene
18 Δδ Opsw values are minimum estimates. Comparison of the most negative Miocene and modern Δδ18O values indicates that there is ~ 2.5 km of overlap in the possible paleoelevation estimates. However, the comparison also admits the previously inferred elevation loss of up to 1.2 km.
55
DISCUSSION AND CONCLUSIONS
Oxygen Isotopes from Zhada Basin
A key strength of this data set is substantial spatial and some temporal averaging
18 of δ Occ values in the shell samples. There is considerable noise in some oxygen isotope archives from the Tibetan Plateau, such as decadally resolved glacial ice, which would lead to a very large range in elevation estimates (e.g., Thompson et. al., 2000). However, water in which the fossil gastropods lived reflects the temporal and geographic average of multiple glaciers and precipitation events on many mountains surrounding the basin.
Fine-scale temporal and spatial variations would be averaged in this process, accounting
18 for the very consistent range of δ Occ values we observe when sorted by
18 paleoenvironment (Figures 2.9 and 2.10). The δ Occ record is consistent both across the basin and through millions of years, indicating that large scale processes are the primary drivers.
18 We need to distinguish a precipitation δ Omw signal from within the range of
18 δ Occ values, some of which have been influenced by post-precipitation evaporation, in
18 18 order to interpret the δ O variability in the ancient record. δ Osw values of water with
18 low residence times (rivers or streams) are closest to δ Omw values of rainfall, since there
18 18 is the least opportunity for enrichment of H2 O due to evaporation. δ Occ values of
18 gastropods from fluvial units therefore provide the most reliable record of the δ Omw
18 18 values of precipitation. The extremely low δ Occ values imply low δ Omw values and are due to the extreme elevation of mountains surrounding (and especially south of)
18 Zhada Basin (Garzione et al., 2000b; Rowley et al., 2001). δ Opsw values (-12.8 to – 56
18 24.3‰, VSMOW) are at least as low as δ Osw values (-11.9 to -17.9‰), indicating that mountains surrounding the Zhada Basin were at elevations at least as high as today
(>6,000m) during the late Miocene. Our paleoenvironmental modelling indicates that climate conditions similar to today prevailed in Zhada Basin during the late Miocene, suggesting an elevation decrease of ~0.6 - 0.8 km in the last 9 million years.
18 Extremely negative δ Occ values of gastropods from fluvial intervals establish a baseline against which we can compare values from other intervals. The higher values, of between +0.7 and -8.2‰ (VPDB), of gastropods from lacustrine intervals are probably due to evaporative enrichment due to a longer residence time of average lake water (figs.
18 11 and 14). Calculated δ Opsw values from lacustrine intervals of between –2.2 and –
11.7 ‰ (VSMOW) are at least as positive as results obtained from modern Tibetan lakes
(+1.7 to -7.1‰, VSMOW, Quade, unpublished data)(Fontes et al., 1996; Gasse et al.,
1991), implying conditions at least as arid as today. The presence of gypsum and mudcracked layers within the lacustrine interval at Zhada, as well as Miocene dune fields support the conclusion that Zhada was arid in the Miocene. The arid conditions implied by both the isotopic and physical evidence provides additional support for an elevated
Himalayan massif south of the Zhada Basin, insofar as orographic blockage of moisture in the region today makes it arid.
18 13 The shifts in gastropod δ Occ and δ Ccc values correlate well with sediment accommodation creation, which also has a primary control on lithofacies and residence
18 time of water. Gastropods from fluvial facies show the most negative δ Occ values
18 13 (Figure 2.10) and little covariance between δ Occ and δ Ccc values (Figure 2.9), due to 57 low water-residence times (Li and Ku, 1997; Talbot, 1990) in the basin. Although the discussion of δ18O and δ13C co-variance in closed basin lakes is usually based on trends in micrites, aquatic gastropods would also be expected to show similar co-variance
18 13 18 because the controls on shell δ Occ and δ Ccc are similar, the temperature: δ Osw and
δ13C of DIC (and secondarily algae) in the lake system (Aucour et al., 2003; Shanahan et al., 2005). Residence times were low because accommodation creation was low and
18 water moved through the system quickly resulting in δ Opsw values, which, like the modern, reflect the elevation of precipitation. Values from gastropods from supralittoral/marshy intervals fall between and overlap values from both fluvial and lacustrine intervals (Figure 2.10), indicating water residence times between that of fluvial and lacustrine facies. This increasing residence time is also reflected in the covariance
18 13 between δ Occ and δ Ccc values from samples from these intervals (Figure 2.9).
Although the system was open at this point, the gradient was low, as suggested by
18 marshy intervals. The increase in residence time is evidenced by higher δ Occ values
18 13 and δ Occ and δ Ccc covariance. Samples from intermediate water-residence-time
18 13 intervals continue the trend towards increasingly evolved δ Occ and δ Ccc values. The
18 13 samples still display covariance, but both the δ Occ and δ Ccc values are systematically higher (Figures 2.9 and 2.10). As the rate of accommodation creation increased, the basin closed, increasing the residence time of water as it began to pond and resulting in an increased evaporative effect. Gastropods from profundal lacustrine facies show
18 13 uniformly high δ Occ and δ Ccc values (Figures 2.9 and 2.10), due to water residence times which were long enough that the system was able to evolve to nearly a steady state 58
(Li and Ku, 1997). Towards the top of the lacustrine interval the return to more negative
18 δ Occ values owes to the fact that the rate of accommodation creation was decreasing as the basin began to fill in (Figure 2.10).
Oxygen Isotopes from Zhongba
The water sampled from wetlands near Zhongba in May is enriched by between
10.3 and 15 ‰ with respect to that sampled in July. Samples 180506-4 and -5 have high
18 δ Osw and δDsw values and fall off of the global meteoric water line, implying extensive evaporation. Only one sample, 260706-2 from the Tsangpo River, falls on the global meteoric water line. The rest of the samples fall on a mixing line defined by
δD = 4.035 δ18O – 67.88
(7) between sample 270706-2 and samples 180506-4 and -5. The implication is that water in the wetlands is replenished during the summer monsoons and subsequently undergoes evaporation during the remainder of the year so that water sampled in May, just before the onset of the monsoon, is highly evaporatively enriched in 18O. Water sampled from the wetlands after the start of the monsoon (sample 260706-3) reflects replenishing and
18 mixing between fresh fluvial water with low δ Osw values and evaporated wetland water
18 with high δ Osw values.
Modelling shows that gastropod shell material in these open basin wetlands were most likely precipitated in equilibrium with monsoon wetland water at temperatures above MAT but no higher than the maximum average monthly temperature. Several 59 conclusions that can be drawn from these results. The first simply reiterates that summer
18 monsoon water dominates the gastropod δ Occ record from southern Tibet. This vastly simplifies the system because we can rule out significant contributions from alternative
18 sources with unknown δ Omw values and we can constrain the temperature of aragonite
18 precipitation. Secondly, it means that the gastropod δ Occ record is dominated by water that has been orographically lifted and thus models based on that assumption (for
18 example Rowley et al., 2001) are valid. Finally, it means that high δ Occ values imply closed basins. A basin that is even intermittently open, such as near Zhongba, will result
18 in low δ Occ values.
Carbon Isotopes
13 The increase in δ Cpm values appears in two measured sections and can be confidently dated to the late Miocene, a time of global C4 plant expansion (figs. 2 and 6).
13 13 This large shift in δ C values (Figure 2.5) denotes a major increase in C4 plants. δ C values of organic matter from these results are also consistent with those seen in Neogene sections across the northern Indian sub-continent (France-Lanord and Derry, 1994; Ojha et al., 2000; Quade et al., 1995; Quade et al., 1989) and from the southern Tibetan Plateau
(Garzione et al., 2000a; Wang et al., 2006). It is premature to use the presence or absence of C4 biomass on the plateau to reconstruct paleoelevation as our knowledge of the modern distribution of C4 plants on the plateau is incomplete. Though CAM plants have been reported on the Tibetan Plateau (for example, Lu et. al., 2004), the plant remains from Zhada confirm that C4 grasses, not CAM plants, are the cause of the late Miocene 60
13 increase in δ Cpm values in Zhada Basin. Moreover, several lines of evidence hint that
C4 plants are present at high elevations. Wang (2003), Garzione and others (2000a), and
Wang and others (2008) found C4 plants, particularly Chenopodiaceae and Gramineae, in the elevation range 3,000 – 4,800 m. These are the same families that dominate the pollen record of the Zhada Formation (Li and Zhou, 2001). The limited ecosystem data published by Wang (2003) suggests that C4 plants at high elevation prefer some sub- ecosystems, such as river valleys. More importantly, the fossil plants that we sampled in the Zhada Formation likely grew in or on the margins of the lake or along marshy watercourses leading to it, given their abundance and associated lithofacies. This suggests that the global expansion of C4 grasses in the late Miocene was not limited to well-drained grasslands but also included semi-aquatic grasses in lakes and wetlands.
Semi-aquatic C4 grasses are well known in other riparian or wetland settings (for example
Jones, 1988; Martinelli et al., 1991), but, as far as we know, they remain unstudied in modern Tibet.
Application to Tectonic Models
This study suggests that the Zhada region of southwestern Tibet underwent a measurable decrease in elevation during the past 9 Myr, a result that is not specifically predicted in any existing tectonic model for the development of the Tibetan Plateau. The late Cenozoic structural setting of the Zhada region motivates us to invoke crustal thinning in response to mid- to upper-crustal extension (Murphy and Copeland, 2005;
Murphy et al., 2002; Thiede et al., 2006; Zhang et al., 2000) as a mechanism that has 61 contributed to elevation loss. However, future studies are needed to determine whether elevation loss was restricted to the Zhada region or affected a larger area of the plateau. 62
CONCLUUSIONS
We have accounted for all the major controls of δ18O change and still the lowest
18 18 calculated δ Opsw is ~3.5 ‰ less than the most negative δ Osw value of modern water.
At this point, our ability to interpret the record in deep time based on the modern is better for oxygen than carbon isotopes, and we therefore favor the case for high elevations in southwestern Tibet at 9 Ma based on the oxygen isotope record. Future research in the region should focus on better understanding the controls and distribution of C4 plants in all ecosystems in Tibet. Twentieth century climate changes can account for part, but not
18 all of the difference between reconstructed and modern δ Osw values, raising the intriguing possibility that mean catchment elevation in southwestern Tibet has decreased by 1 – 1.5 km since ~9 Ma. The decrease in elevation is indicated by an approach that assumes a minimum paleoelevation uncertainty estimate. While a solely climatically
18 driven change in δ Osw values cannot be completely ruled out, the proxies cited show no evidence of climate change which would result in the observed change. On the other hand, there is evidence of crustal thinning through detachment faulting in the Zhada area that could explain an elevation loss. This decrease in elevation is consistent with tectonic models that invoke collapse of an over-thickened Tibetan crust due to a change in internal or boundary conditions. 63
Figure 2.1. A: Elevation, shaded relief and generalized tectonic map of the Himalayan – Tibetan orogenic system showing the location of the Zhada Basin relative to other sources of paleoelevation data on the plateau. Sources for paleoelevation data are as follows; Thakkhola graben: Garzione et. al. (2000b), Oiyug basin: Currie et. al. (2005) and Spicer et. al. (2003), Lunpola basin: Rowley and Currie (2006), Nima basin: DeCelles et. al. (2007), locations in the Tarim and Qaidam basins: Graham et. al. (2005), Hoh Xil basin: Cyr et. al. (2005) and Gyirong basin: Rowley et. al. (2001) and Wang et. al. (2006). B: Generalized geologic map of the Zhada region. Gastropod samples for this study come from measured sections whose location is indicated by solid black lines. Modified from published mapping by Chen and Xu (1987), Murphy et. al. (2000, 2002) and unpublished mapping by M. Murphy. 64
Figure 2.2. Vector component diagrams for the South Zhada Sections. Site qualities A, B, C and D are presented by sites S322, S0313, LC6 and S0305 respectively. 65
Figure 2.3. Site mean and section mean vectors for the South Zhada and Southeast Zhada Sections. The mean vectors for normal and reversed polarity sites are anti-parallel and thus pass the ―Reversals Test‖ (Butler, 1992). 66
Figure 2.4. Modern water and gastropod sample locations from the Zhongba area. Image from Google Earth. 67
Figure 2.5. δ13C of vascular organic material versus stratigraphic level for the South Zhada and East Zhada measured sections. In both sections we see the introduction of C4 plants (δ13C values > -16 ‰) at 250 - 300 m. The shift in δ13C values, from uniformly negative to a mixture of more and less negative values at 250 – 300 m, is seen in the northern Indian sub-continent and southern Tibetan Plateau and is associated with a change in biomass from C3 dominated to a mix of C3 and C4 or C4 dominated biomass at ~ 7 Ma. 68
69
Figure 2.6. Measured sections and magnetostratigraphic results for the South Zhada and Southeast Zhada sections. Sections were correlated using the top surface as a datum (A) to produce a composite magnetostratigraphic column (B). Which was then correlated with the GPTS of Cande and Kent (1995) (C-H). Our favoured correlation is E. See text for details. 91 sites were used to construct the South Zhada section and 60 sites were used to construct the Southeast Zhada section. 70
Figure 2.7. Stable isotope composition of modern water from the Zhada Basin and Zhongba area plotted against the Global Meteoric Water Line. The thin black line is a mixing line between evaporated wetland samples and an unevaporated fluvial sample from Zhongba. 71
Figure 2.8. X-Ray diffraction data for (A) aragonite standard, (B) calcite standard and (C) a representative sample from the South Zhada section. The sample matches peaks at 26- 27º, 33º, 36-38º, 46º, 48.5º, 50º and 53º and lacks the prominent peak in calcite at 29.5º. Spectra from all samples that returned usable results (11 of 12) match the 0.1SZ4.5 spectrum. 72
73
Figure 2.9. Oxygen and carbon isotope covariance for gastropods from the Zhada formation showing covariance patterns for lithofacies assemblages. Correlation coefficients for the entire data sets are 0.65 and 0.62 for South Zhada and East Zhada 18 13 respectively. Also shown are δ Occ and δ Ccc values for modern gastropods from the Zhongba wetlands. 74
75
Figure 2.10. δ18O (VPDB ‰) and stratigraphic height for Miocene – Pleistocene gastropods from (A) South Zhada and (B) East Zhada subdivided by lithofacies assemblages. 76
Figure 2.11. δ18O (VPDB ‰) and mm growth from seasonally sampled Miocene – Pleistocene gastropods from Zhada Basin. Typical seasonal variations are between 2 - 3 ‰. Sample 2EZ16A is from a marshy interval and shows evidence of a drying episode. Sample 5EZ27 is from a deltaic sequence and shows evidence of a freshening episode. 77
78
18 Figure 2.12. A) Calculated δ Opw values from gastropods from the South Zhada measured section. Error bars represent an uncertainty of ± 7°C due to possible seasonal variation in the temperature of carbonate precipitation. The range of modern fluvial or stream water (-17.9 to –11.9 ‰: light grey box) and mean value for modern water (-14.8 ‰: dashed vertical line) as well as the range of values obtained from modern Tibetan 18 lakes (+1.7 to -7.1 ‰: dark grey box) are shown for comparison. δ Opsw values from gastropods from fluvial intervals are at least as negative as the corrected modern, 18 reflecting elevations at least as high as the modern. δ Opsw values from gastropods from lacustrine intervals are at least as positive as those from modern lakes, reflecting an environment that, like the modern, was arid. B) South Zhada measured stratigraphic section. C) Site-mean virtual geomagnetic pole (VGP) latitude for the South Zhada section plotted against stratigraphic level and correlated with the global polarity timescale of Cande and Kent (1995). Positive VGP latitudes indicate normal polarity shown by black intervals and negative VGP latitudes indicate reversed polarity shown by white intervals. 79
Figure 2.13. Modelled enrichment values (horizontal grey box) for the modern relative humidity range (vertical grey box) and temperatures between 0 and 10 ºC compared with Miocene enrichment (diagonally ruled box). Miocene enrichment (21.7 to 18.7 ‰) is based on the difference in δ18O between fluvial and lacustrine gastropods. Also shown are the mean annual temperature (0 ºC), average temperature from April – October (7 ºC), maximum mean month temperature (14 ºC) and absolute maximum temperature (21 ºC) for 1961 – 1990 at Shiquanhe weather station. Calculated Miocene enrichment values overlap modelled modern enrichment values, indicating that the climate in the Miocene was cold and arid, very similar to the modern. 80
Figure 2.14. Temperature of aragonite precipitation reconstructed based on modern 18 18 gastropod shell δ Occ and associated water δ Osw values. 81
Figure 2.15. Modeled percent of modern aragonite in equilibrium with monsoon wetland 18 waters given various temperature and pre-monsoon wetland water δ Osw values. The 18 range of δ Occ values of gastropods from modern wetlands along the Tsangpo River are shown in the horizontal grey shaded box. 82
Figure 2.16. Δδ18O (VSMOW ‰) of modern water from the Zhada Basin and the mean and maximum catchment elevation for water samples. Δδ18O is calculated assuming a low-elevation δ18O value for New Delhi of -5.8 ‰. Also shown are thermodynamically based lapse rate models (based on work by Rowley et. al. (2001) and Rowley and Garzione (2007)) with low-elevation temperature of 303 K (dashed line), 300 K (thick black line), 295 K (thin black line) and an empirical lapse rate (from Garzione et. al., 2000b, light grey line). 83
Figure 2.17. Δδ18O (VSMOW ‰) values for the most negative modern Zhada water samples and most negative reconstructed Miocene – Pleistocene water and modelled elevation for thermodynamically based lapse rate models with low-elevation temperature of 300 K (black line) and 295 K (dark grey line) and an empirical lapse rate (light grey line). Δδ18O values were calculated using the modern low-elevation δ18O value of -5.8‰ from New Delhi and a Miocene low-elevation δ18O value of – 6‰ from Siwalik group paleosol carbonates. Uncorrected Miocene – Pleistocene water samples are indicated by diamonds and those that have been corrected for an ~ 3 ‰ post-industrial revolution increase are indicated by squares. In both cases the difference between Miocene – Pleistocene water and modern water δ18O values is greater than the uncertainty associated with them indicating that the modelled loss in elevation is reliable. 84
Figure 2.18. Comparison of the range of Δδ18O values for reconstructed Miocene fluvial water and modern water from the Zhada Basin verses elevation. Also shown is the 2ζ uncertainty envelope around a mean Δδ18O versus elevation lapse rate. The low elevation Ti for the mean Δδ18O versus elevation lapse rate is 295K and low elevation relative humidity is 80%. Unlike figure 11, which presents a minimum uncertainty estimation, this figure presents the typically cited 2ζ uncertainty. This results in considerable overlap in reconstructed elevation. However, it also admits the previously inferred elevation loss. 85
Table 2.1. Stable isotope and elevation data for modern water from the Zhada Basin and Zhongba area.
Sample Sample Maximum Mean δ18O (‰ δD (‰ Lat. (N) Long. (E) Notes Name Elevation Watershed Watershed VSMOW) VSMOW) (m) Elevation Elevation (m) (m) Zhada water JQ-38 4325 5943.47 5188.63 -14.3 -106 31.53415 79.975603 Ai Shan JQ-39 3613 6842.24 5419.08 -17.9 -130 31.46889 79.784636 Himalaya, Same Catchment as JQ-42 and w2571 JQ-40 3523 6856.46 4855.59 -14.3 -100 31.47474 79.74296 Sutlej River JQ-37 4524 5843.2 5136.76 -16.1 -117 31.45092 80.12007 Ai Shan JQ-41 3535 6856.46 4855.59 -16.5 -123 30.75320 79.77028 Sutlej River JQ-42 3851 6842.24 5419.08 -16.4 -116 31.33770 79.790041 Himalaya, Same Catchment as JQ-39 and w2571 JQ-76 3988 5632 4547 -15.4 -117 31.3343 79.901867 Himalaya JQ-77 3790 6856.46 4855.59 -14.4 -104 31.4005 79.921533 Sutlej River JQ-80 4074 6253 4881 -13.4 -94 31.16668 80.0719 Himalaya JQ-81 4101 5764 4844 -7.3 -75 31.12047 80.117783 Himalaya JQ-82 4287 6179 5079 -15.7 -112 30.97107 80.3501 Himalaya w0281 5184 6603.87 5768.95 -16.9 -125 31.13423 79.450681 Himalaya w0381 3718 6856.46 4855.59 -15 -110 29.05971 88.000349 Sutlej River w1771 4409 6043.34 5055.83 -16 -118 31.99252 79.642386 Ai Shan, Same location as 230706-3 w1772 4410 6257.3 5143.86 -15 -107 32.99252 80.642384 Ai Shan, Same location as 230706-4 w2371 4724 6069 5325 -13.2 -98 32.22481 79.57032 Ai Shan, Same location as 230706-2 w2571 3762 6842.24 5419.08 -17.6 -137 31.45323 79.657603 Himlaya, Same Catchment as JQ-39 and -42 110706-1 4678 5028 4760 -12.6 -90 31.30662 79.57273 Himalaya 160706-3 5026 6048.77 5454.95 -15 -112 31.19732 79.5518 Himalaya 160706-4 5042 5806.18 5304.09 -11.9 -86 31.20925 79.546983 Himalaya 200706-1 4341 6202.7 4998.89 -13.4 -99 31.88190 79.7102 Ai Shan 200706-2 4693 5352.13 4904.31 -13.5 -99 31.96550 79.755167 Ai Shan 200706-6 4431 6023 5063.87 -13.8 -100 32.20142 79.423383 Ai Shan 210706-1 4960 6081.74 5569.38 -12.7 -93 32.32415 79.0589 Ai Shan 32.23063 79.57265 Ai Shan, Same location as 230706-2 4738 6069 5325 -13.8 -101 w2371 86
230706-3 4368 6043.34 5055.83 -13.4 -102 31.99842 79.64865 Ai Shan, Same location as w1771 230706-4 4368 6257.3 5143.86 -13.2 -102 31.99842 79.64865 Ai Shan, Same location as w1772 240706-1 4863 6255 5680 -14.3 -112 31.82573 79.03238 Ai Shan 240706-2 4534 6255 5510 -15.2 -108 31.91108 80.10542 Ai Shan Zhongba water 180506-4 4569 -6.3 -90 29.66257 84.16760 180605-5 4591 -3.9 -86 29.08736 83.73856 260706-2 4574 -18.9 -140 29.71140 84.07028 260706-3 4571 -16.6 -140 29.68233 84.15037
87
Table 2.2. Oxygen and carbon isotope data (VPDB) from Miocene – Pleistocene gastropods from Zhada Basin. Also included are the calculated Miocene – Pleistocene water values that the aragonite was precipitated in assuming a temperature of precipitation of 7 C and the stratigraphic height of the gastropod samples.
Sample name δ18O δ 18O δ 13C Stratigraphic (VPDB ‰) (VSMOW (VPDB height (m) ‰)* ‰) South Zhada Section 0.1SZ22A -16.1 -19.0 -7.8 102.75 0.1SZ22B -11.8 -14.7 -6.0 102.75 0.1SZ22C -9.9 -12.8 -10.3 102.75 0.1SZ22D -11.3 -14.2 -6.6 102.75 0.1SZ23.25 -20.9 -23.7 -7.7 104 0.1SZ24.5 -18.9 -21.8 -6.4 105.25 0.1SZ25 -10.5 -13.4 -6.2 105.75 0.1SZ25A -10.2 -13.1 -5.7 105.75 0.1SZ26.2A -20.2 -23.1 -7.6 106.95 0.1SZ26.2B -21.0 -23.9 -5.4 106.95 0.1SZ26.2C -21.4 -24.3 -7.0 106.95 0.1SZ29.7 -9.9 -12.8 -3.3 110.45 0.1SZ31A -14.6 -17.4 -9.0 111.75 0.1SZ31B -17.6 -20.5 -7.3 111.75 0.1SZ38.5 -14.2 -17.1 -8.5 119.25 0.1SZ4.5 -1.7 -4.6 -0.3 85.25 0.1SZ4.5AD1 -2.4 -5.4 0.7 85.25 0.1SZ4.5AD10 -2.2 -5.1 2.2 85.25 0.1SZ4.5AD10.1 -2.4 -5.3 1.9 85.25 0.1SZ4.5AD10.2 -3.5 -6.4 1.1 85.25 0.1SZ4.5AD11 -4.1 -7.0 0.4 85.25 0.1SZ4.5AD11.1 -3.9 -6.8 1.1 85.25 0.1SZ4.5AD12 -3.3 -6.2 1.9 85.25 0.1SZ4.5AD13 -3.5 -6.4 0.6 85.25 0.1SZ4.5AD14 -3.6 -6.5 1.7 85.25 0.1SZ4.5AD14.1 -3.1 -6.0 1.4 85.25 0.1SZ4.5AD14.2 -2.0 -4.9 1.4 85.25 0.1SZ4.5AD14.3 -4.7 -7.6 2.1 85.25 0.1SZ4.5AD15 -5.2 -8.1 2.6 85.25 0.1SZ4.5AD2 -3.4 -6.3 2.5 85.25 0.1SZ4.5AD4 -4.5 -7.4 2.1 85.25 0.1SZ4.5AD5 -3.1 -6.0 1.9 85.25 0.1SZ4.5AD6 -2.1 -5.0 1.9 85.25 0.1SZ4.5AD7 -1.8 -4.8 1.9 85.25 0.1SZ4.5AD8 -1.5 -4.4 3.0 85.25 0.1SZ4.5AD9 -1.8 -4.8 1.9 85.25 0.1SZ48.7 -13.6 -16.5 -5.1 129.45 88
0.1SZ52 -13.0 -15.9 -4.4 132.75 0.1SZ53.25 -17.3 -20.1 -3.2 134 0.1SZ53.25A -20.3 -23.2 -6.5 134 0.1SZ53.25B -21.6 -24.5 -7.3 134 0.1SZ53.25C -5.2 -8.1 -5.7 134 0.1SZ53.25D -18.3 -21.2 -7.1 134 0.2SZ10 -10.1 -12.9 0.7 160.7 0.2SZ11.5 -14.2 -17.0 -11.0 162.2 0.2SZ11.5A -18.3 -21.2 -6.0 162.2 0.2SZ11.5B -7.6 -10.5 -8.9 162.2 0.2SZ15.5 -9.1 -12.0 -11.2 166.2 0.2SZ20 -15.3 -18.2 -10.0 170.7 0.2SZ25 -11.7 -14.5 -4.1 175.7 0.2SZ36A -17.7 -20.6 -10.6 186.7 0.2SZ36B -17.0 -19.9 -7.8 186.7 0.3SZ15.15 -20.6 -23.5 -7.7 217.15 0.3SZ22 -8.1 -11.0 -2.5 224 0.3SZ32.5 -0.7 -3.6 -0.9 234.5 0.3SZ38.25 -5.6 -8.5 1.6 240.25 0.3SZ38.25D1 -8.3 -11.2 -2.8 240.25 0.3SZ38.25D2 -7.9 -10.8 -3.4 240.25 0.3SZ38.25D3 -7.0 -9.9 -3.7 240.25 0.3SZ38.25D4 -7.1 -10.0 -3.8 240.25 0.3SZ38.25D5 -6.8 -9.7 -2.9 240.25 0.3SZ38.25D6 -6.2 -9.1 -2.3 240.25 0.3SZ38.25D7 -7.1 -10.0 -2.6 240.25 0.3SZ38.25D8 -8.1 -11.0 -3.1 240.25 0.3SZ38.25D9 -8.8 -11.7 -3.3 240.25 0.3SZ42 -2.5 -5.4 -0.5 244 0.3SZ6.8AD2 -11.3 -14.2 -8.9 208.8 0.3SZ6.8ADA -9.7 -12.6 -9.3 208.8 0.4SZ14.9 -20.3 -23.1 -9.4 278.25 0.4SZ24.65 -3.9 -6.8 -0.6 288 0.4SZ24.8 -4.5 -7.4 1.9 288.15 0.4SZ25 -0.9 -3.8 0.6 288.35 0.4SZ25.35 -1.8 -4.8 -3.0 288.7 0.4SZ4.8 0.2 -2.7 -1.3 268.15 1SZ12 -3.9 -6.8 -0.9 309.65 1SZ13 -12.5 -15.4 -3.0 310.65 1SZ13.8 -3.2 -6.1 -1.3 311.45 1SZ18 -1.8 -4.7 2.1 315.65 1SZ2.5 -2.4 -5.3 0.6 300.15 1SZ24 -5.4 -8.3 -0.2 321.65 1SZ24.1 -4.6 -7.5 -0.5 321.75 1SZ27.9 -2.8 -5.7 0.0 325.55 1SZ32 -1.5 -4.4 0.5 329.65 2SZ16.4 -12.1 -14.9 -5.1 349.5 89
2SZ3.25 -1.6 -4.5 0.8 336.35 2SZ34.5 -14.6 -17.4 -7.4 367.6 2SZ35.5 -11.6 -14.5 -5.3 368.6 2SZ41A -13.9 -16.7 -2.6 374.1 2SZ41B -17.4 -20.3 -5.1 374.1 2SZ41C -14.6 -17.5 -5.5 374.1 2SZ43 -1.8 -4.8 0.9 376.1 2SZ43.1 -6.8 -9.7 -0.4 376.2 2SZ47 -1.9 -4.8 -0.6 380.1 2SZ51.5 -2.4 -5.3 -0.2 384.6 2SZ51.5AD0.5 -0.6 -3.5 -0.6 384.6 2SZ51.5AD10 -1.2 -4.1 0.2 384.6 2SZ51.5AD11 -2.1 -5.0 0.2 384.6 2SZ51.5AD12 -2.2 -5.1 0.1 384.6 2SZ51.5AD13 -2.1 -5.1 0.3 384.6 2SZ51.5AD14 -2.5 -5.4 0.2 384.6 2SZ51.5AD15 -0.8 -3.7 0.8 384.6 2SZ51.5AD3 -2.2 -5.1 -0.4 384.6 2SZ51.5AD4 -2.1 -5.0 -0.1 384.6 2SZ51.5AD5 -1.6 -4.5 0.3 384.6 2SZ51.5AD6 -0.8 -3.7 0.9 384.6 2SZ51.5AD7 -0.3 -3.2 0.0 384.6 2SZ51.5AD8 -0.3 -3.2 0.0 384.6 2SZ51.5AD9 -0.4 -3.3 -0.1 384.6 2SZ55 -2.3 -5.2 -0.7 388.1 2SZ7.5 -2.0 -4.9 1.0 340.6 3SZ0.15 -1.7 -4.6 0.9 389.25 3SZ14.45 -2.9 -5.8 1.9 403.55 3SZ14.5 -2.0 -4.9 1.2 403.6 3SZ18.5 -3.1 -6.0 -0.8 407.6 3SZ24 -2.2 -5.1 -0.3 413.1 3SZ24.1A -2.8 -5.7 1.6 413.2 3SZ24.25A -1.4 -4.4 0.8 413.35 3SZ24.25B -1.8 -4.8 -1.1 413.35 3SZ24.25C -1.6 -4.5 0.6 413.35 3SZ24.3 -2.0 -4.9 0.9 413.4 3SZ27 0.7 -2.2 -2.1 416.1 3SZ3.9 -2.0 -4.9 -0.4 393 3SZ32.5 -15.5 -18.3 -5.0 421.6 3SZ4 -3.3 -6.2 -0.8 393.1 3SZ41.5 -4.6 -7.5 0.4 430.6 3SZ49 -13.7 -16.6 -3.3 438.1 3SZ5 -1.4 -4.4 1.4 394.1 3SZ50.5 -1.0 -3.9 -1.2 439.6 3SZ55 -2.5 -5.4 1.2 444.1 3SZ61.8AD1 -0.8 -3.7 0.2 450.9 3SZ61.8AD2 -0.9 -3.8 0.1 450.9 90
3SZ62 -1.3 -4.2 0.0 451.1 3SZ67.5 -2.4 -5.3 0.9 456.6 3SZ74A -3.0 -5.9 0.3 463.1 3SZ74B -1.8 -4.7 0.1 463.1 3SZ75.6A -5.0 -7.9 -0.5 464.7 3SZ75.6B -4.6 -7.5 0.0 464.7 4SZ5 -9.9 -12.8 7.5 534.7 5SZ4.6A -9.9 -12.8 1.3 642.9 5SZ4.6B -7.7 -10.6 1.4 642.9 East Zhada Section 1EZ10 -11.8 -13.6 -5.0 10 1EZ11 -18.3 -20.0 -8.9 11 1EZ12 -16.8 -18.6 -8.2 12 1EZ25.5 -12.7 -14.5 -4.4 25.5 1EZ25.5A -16.1 -17.8 -4.1 25.5 1EZ25.5BD1 -9.7 -11.5 -5.4 25.5 1EZ25.5BD2 -9.3 -11.1 -5.6 25.5 1EZ25.5C -7.9 -9.7 -5.3 25.5 1EZ25.5D -15.6 -17.3 -5.8 25.5 1EZ27 -17.6 -19.3 -5.8 27 1EZ35.5 -15.1 -16.8 -8.0 35.5 1EZ42 -14.1 -15.8 -6.5 42 1EZ44.75 -16.9 -18.7 -10.8 44.75 1EZ46 -19.0 -20.8 -7.9 46 1EZ5.55 -14.4 -16.1 -6.8 5.55 1EZ5.55AD1 -17.8 -19.5 -9.1 5.55 1EZ5.55AD2 -18.7 -20.4 -9.1 5.55 1EZ5.55AD3 -19.2 -21.0 -9.6 5.55 1EZ5.55BD1 -13.5 -15.2 -6.9 5.55 1EZ5.55CD1 -11.6 -13.3 -5.2 5.55 1EZ5.55CD2 -11.2 -13.0 -5.6 5.55 1EZ52.2 -16.0 -17.8 -7.7 52.2 1EZ63 -10.7 -12.5 -4.0 63 1EZ8.9A -15.8 -17.6 -12.8 8.9 1EZ8.9AD1 -16.7 -18.5 -6.8 8.9 1EZ8.9AD2 -17.1 -18.9 -12.8 8.9 1EZ8.9AD3 -17.2 -18.9 -12.4 8.9 1EZ8.9AD4 -17.6 -19.4 -12.7 8.9 1EZ8.9AD5 -18.2 -20.0 -11.8 8.9 1EZ8.9BD1 -19.0 -20.7 -12.9 8.9 1EZ8.9BD2 -18.9 -20.7 -12.0 8.9 1EZ8.9BD3 -16.1 -17.9 -13.4 8.9 1EZ8.9C -17.5 -19.2 -13.6 8.9 2EZ111.5 -18.3 -20.1 -7.7 167 2EZ115.5 -17.1 -18.9 -5.5 171 2EZ16.2A -13.5 -15.3 -12.4 71.7 91
2EZ16AD1 -15.6 -17.4 -7.5 71.5 2EZ16AD2 -13.3 -15.0 -3.8 71.5 2EZ16AD3 -4.9 -6.7 -1.8 71.5 2EZ16AD4 -15.8 -17.5 -3.0 71.5 2EZ16B -16.5 -18.2 -11.1 71.5 2EZ22 -16.0 -17.8 -13.8 77.5 2EZ39 -19.1 -20.8 -8.1 94.5 2EZ60.7 -12.6 -14.3 -3.4 116.2 2EZ60.7A -17.8 -19.6 -5.5 116.2 2EZ60.7B -15.7 -17.4 -3.6 116.2 2EZ60.7C -16.2 -18.0 -0.7 116.2 2EZ63 -11.7 -13.5 -0.3 118.5 2EZ63AD1 -10.9 -12.7 -5.0 118.5 2EZ63AD2 -11.1 -12.8 -5.4 118.5 2EZ63AD3 -11.9 -13.7 -6.5 118.5 2EZ63AD4 -11.5 -13.2 -6.7 118.5 2EZ63B -6.9 -8.7 -2.7 118.5 2EZ63C -11.6 -13.4 -3.5 118.5 2EZ63D -8.8 -10.6 -3.2 118.5 2EZ63E -12.2 -14.0 -8.7 118.5 2EZ89.45 -9.8 -11.6 -2.8 144.95 2EZ9.5 -14.3 -16.0 -4.6 65 3EZ100 -15.3 -17.1 -3.6 100 3EZ102 -16.5 -18.3 -3.5 276.35 3EZ119.5 -4.7 -6.5 -3.6 293.85 3EZ131.3A -3.8 -5.6 0.0 305.65 3EZ131.3B -2.5 -4.3 -0.2 305.65 3EZ136 -13.8 -15.6 -0.6 310.35 3EZ146 0.1 -1.7 -1.1 320.35 3EZ152.3A -4.3 -6.0 -3.5 326.65 3EZ152.3B -3.1 -4.9 -1.7 326.65 3EZ158 -2.8 -4.6 0.3 332.35 3EZ173 -3.7 -5.5 -0.2 347.35 3EZ180 -4.1 -5.9 0.1 354.35 3EZ180.5 -2.5 -4.3 0.4 354.85 3EZ183 -2.8 -4.6 -0.3 357.35 3EZ187.5 -9.3 -11.0 -2.2 361.85 3EZ46 -10.0 -11.8 -4.4 220.35 3EZ63.5 -15.7 -17.5 -5.0 237.85 3EZ69.2 -17.4 -19.1 -7.2 243.55 3EZ69.2A -16.7 -18.5 -3.4 243.55 3EZ69.2BD1 -17.2 -18.9 -5.2 243.55 3EZ69.2BD2 -15.6 -17.3 -3.9 243.55 3EZ69.2C -18.0 -19.7 -5.2 243.55 3EZ69.5 -16.0 -17.7 -5.9 243.85 3EZ7 -13.9 -15.7 -4.7 181.35 3EZ98 -14.1 -15.9 -3.8 272.35 92
3EZ99 -12.6 -14.3 -7.3 273.35 4EZ1 -3.0 -4.7 -2.7 414.45 4EZ23.9 -3.9 -5.7 0.3 437.35 4EZ23.9 -3.9 -5.7 1.3 437.35 4EZ23.9 -4.4 -6.2 1.0 437.35 4EZ23.9 -3.1 -4.9 0.5 437.35 4EZ23.9 -2.2 -4.0 1.3 437.35 4EZ23.9 -1.9 -3.7 1.7 437.35 4EZ23.9 -3.3 -5.1 1.0 437.35 4EZ23.9A -4.2 -5.9 -0.2 437.35 EDGE 4EZ23.9A APEX -5.0 -6.8 -0.5 437.35 4EZ23.9B -3.6 -5.4 -0.9 437.35 EDGE 4EZ23.9B APEX -5.3 -7.1 1.1 437.35 4EZ23.9C -5.0 -6.8 0.7 437.35 4EZ23.9D -2.0 -3.7 1.3 437.35 4EZ23.9E -3.5 -5.3 -0.1 437.35 4EZ23.9 EDGE -3.8 -5.6 1.1 437.35 4EZ23.9 APEX -3.0 -4.8 1.3 437.35 4EZ23.9F -2.5 -4.3 1.3 437.35 4EZ3 -3.6 -5.3 -1.8 416.45 4EZ30 -15.3 -17.0 -0.6 443.45 4EZ35.3 -10.8 -12.6 0.4 448.75 4EZ4 -3.1 -4.9 0.0 417.45 5EZ1.5A -3.1 -4.9 -0.2 488.35 5EZ1.5B -2.2 -4.0 -2.4 488.35 5EZ27.75 -3.2 -5.0 -0.2 514.6 5EZ3 -1.5 -3.3 -0.1 489.85 5EZ32 -4.8 -6.6 0.2 518.85 5EZ6.45 -4.4 -6.2 -1.1 493.3
93
Table 2.3. δ13C (VPDB ‰) for plant material from the South Zhada and East Zhada sections.
Sample C Stratigraphic Name (VPDB height (m) ‰) East Zhada Section
1EZ5.55 -24.49 5.55 1EZ13 -23.93 13 1EZ34.1 -24.52 34.1 2EZ49.1 -24.80 104.65 2EZ68.5 -25.03 124.05 3EZ12.8 -23.41 150.25 3EZ139 -21.38 295.05 3EZ139 -24.07 295.05 3EZ147 -11.54 303.05 3EZ147 -18.53 303.05 3EZ90.8 -23.64 246.85 4EZ20 -23.39 371.55 4EZ3 -8.39 354.55 4EZ3 -23.24 354.55 4EZ6.4 -24.36 357.95 5EZ21.1 -14.24 421.05 5EZ35.6 -14.78 435.55 5EZ35.6 -11.97 435.55 5EZ39.9 -22.55 439.85 South Zhada Section
0.1SZ25 -25.49 105.75 0.4SZ25 -14.80 288.36 0.4SZ25 -16.84 288.36 2SZ 50.35 -18.59 383.46 2SZ35.3 -24.16 368.41 2SZ7.7 -25.24 340.81 2SZ7.7 -24.8 340.81 2SZ5.85 -25.96 338.96 0.3SZ43.35 -18.68 245.36 0.3SZ32.6 -21.10 234.61 0.3SZ32 -22.97 234.01 0.3SZ32 -22.83 234.01 0.3SZ26 -24.24 228.01 0.1SZ52.35 -26.78 133.1 0.1SZ52.35 -26.08 133.1 94
0.1SZ25 -25.40 105.75 4SZ100.2 -24.05 629.9
95
CHAPTER 3: BASIN FORMATION DUE TO ARC-PARALLEL EXTENSION
AND TECTONIC DAMMING: ZHADA BASIN, SW TIBET
ABSTRACT
The late Miocene – Pleistocene Zhada basin in southwestern Tibet provides a record of elevation loss and basin formation via arc-parallel extension within an active collisional thrust belt. The > 800 m-thick basin fill is undeformed and was deposited along an angular unconformity on top of Tethyan strata that were previously shortened in the Himalayan fold- thrust belt. Modal sandstone petrographic data, conglomerate clast- count data, and detrital zircon U-Pb age spectra indicate a transition from detritus dominated by a distal, northern source to a local, southern source. This transition was accompanied by a change in paleocurrent directions from uniformly northwestward to basin-centric. At the same time the depositional environment in the Zhada basin changed from a large, braided river to a closed-basin lake. Sedimentation in the Zhada basin was synchronous with displacement on faults surrounding the basin, particularly the Qusum and Gurla Mandhata detachment faults, which root beneath the basin and exhume mid- crustal rocks along the northwestern and southeastern flanks of the basin, respectively.
These observations indicate that accommodation for Zhada basin fill was produced by a combination of tectonic subsidence and damming, as mid-crustal rocks were evacuated from beneath the Zhada basin and uplifted along its northwestern and southeastern margins in response to arc-parallel slip on the Qusum and Gurla Mandhata detachment faults. 96
INTRODUCTION
Since they were first recognized (Molnar and Tapponnier, 1978; Ni and York,
1978), normal fault-bounded basins in the high Himalaya have fueled speculation on their origins and have been used as fundamental arguments in various tectonic models (Armijo et al., 1986; Beaumont et al., 2004; Garzione et al., 2003; Hurtado et al., 2001; Kapp and
Guynn, 2004; e.g., McCaffrey and Nabelek, 1998; Molnar et al., 1993; Ratschbacher et al., 1994; Seeber and Pecher, 1998; Tapponnier et al., 2001). These sedimentary basins provide a record of tectonic and climatic processes essential for discriminating between competing hypotheses about the evolution of the Himalayan-Tibetan orogenic system.
The Mio-Pleistocene Zhada basin in the western portion of the Himalayan arc
(Figure 3.1) provides an opportunity to study the causes of basin formation in the
Himalayan hinterland (Meng et al., 2008; Saylor et al., in press; Wang et al., 2008a;
Wang et al., 2008b; Zhang et al., 1981; Zhu et al., 2007; Zhu et al., 2004). The Zhada basin sits at unusually low elevations. Here, elevation averaged over a 100 km interval is
> 1,000 m lower than anywhere else along strike (Figure 3.2). Ganser (1964) noted that the Zhada basin dwarfs other late Cenozoic sedimentary basins in southern Tibet and the northern Himalaya. Finally, stable isotope data indicate that the Zhada region has probably lost up to 1.5 km of elevation since the late Miocene (Saylor et al., in press).
There is little information, and less consensus, regarding the age and tectonic significance of the Zhada basin despite its abundance of vertebrate, invertebrate and plant fossils, and location within the tectonically active hinterland of the Himalaya (Murphy et al., 2002; Ni and Barazangi, 1985; Thiede et al., 2006; Valli et al., 2007; Wang et al., 97
2008a; Zhang et al., 2000). Basic aspects of the basin geology, such as its stratigraphy and sedimentology, are thinly documented and variably interpreted. For example, the
Zhada Formation is reported as both an upward-fining fluvio-lacustrine sequence (Li and
Zhou, 2001; Zhang et al., 1981; Zhou et al., 2000) or, alternatively, as being capped by boulder conglomerates (Zhu et al., 2007; Zhu et al., 2004). Wang et al. (2004) proposed that the Zhada basin is a supradetachment basin developed above the South Tibetan
Detachment system. This conflicts with the conclusion that the Zhada basin developed in response to arc-perpendicular compression (Zhou et al., 2000). In contrast to both of these scenarios, Wang et al. (2008a) concluded that the Zhada basin developed due to arc-perpendicular rifting and Zhu et al. (2004) suggested that rifting was followed by recent uplift.
In this paper we examine the development of the Zhada basin and its relationship to basin-bounding faults as informed by new sedimentologic, provenance, and sediment dispersal pattern data. Our results show that the basin evolved from a through-going fluvial system to an internally drained depocenter concomitant with exhumation of mid- crustal rocks to the northwest and southeast in the footwalls of major arc-parallel extensional systems. We present a tectonic model that links development of the Zhada basin directly to these extensional systems, and which explains basin development through a combination of sill uplift and basin subsidence due to arc-parallel extension on crustal-scale detachment faults. 98
GEOLOGIC SETTING
The NW-SE-trending Zhada basin is located just north of the high Himalayan ridge crest in the western part of the orogen (~32° N, 82° E, Figure 3.1A). The basin is >
150 km long and > 60 km wide and has an outcrop extent of > 9,000 km2.
Major structural features near the margins of the Zhada basin are the South
Tibetan Detachment system (STDS) to the southwest, the Oligo-Miocene Great Counter thrust and right-slip Karakoram fault to the northeast, and the Leo Pargil and Gurla
Mandhata gneiss domes to the northwest and southeast, respectively (Figure 3.1B). The
STDS is a series of north-dipping, low-angle, top-to-the-north normal faults that place
Paleozoic – Mesozoic low-grade metasedimentary rocks of the Tethyan sequence on high-grade gneisses and granitoids of the Greater Himalayan sequence (Hodges et al.,
1992). No ages for movement on the STDS in this area have been published, but along strike displacement is bracketed between 21 and 12 Ma (Cottle et al., 2007; Hodges,
2000; Hodges et al., 1996; Hodges et al., 1992; Murphy and Yin, 2003; Murphy and
Harrison, 1999; Searle et al., 1997; Searle et al., 2003; Yin, 2006). Although rocks of
Indian affinity are separated from those of Asian affinity by the Indus suture, the region north of the STDS is considered the southern edge of the Tibetan plateau because of the uniformly high elevations (Fielding et al., 1994). In the Zhada region the south-dipping, top-to-the-north Oligo-Miocene Great Counter thrust system cuts the Indus suture (e.g.,
Ganser, 1964; Murphy and Yin, 2003; Yin et al., 1999). Exhumation of the Leo Pargil gneiss dome by normal faulting initiated at either 15 Ma or 9 Ma, as indicated by
40Ar/39Ar and AFT cooling ages, respectively (Thiede et al., 2006; Zhang et al., 2000). 99
Exhumation of the Gurla Mandhata gneiss dome began at 9 Ma (Murphy et al., 2002).
Faulted Quaternary basin fill indicates that gneiss dome development continues today
(Murphy et al., 2002).
The Zhada Formation occupies the Zhada basin and consists of > 800 m of fluvial, lacustrine, eolian and alluvial fan deposits (Figure 3.3). The basin fill is structurally undisturbed and sits above shortened Tethyan sequence strata along an angular or buttress unconformity (Figures 3.4A, C). The Zhada Formation is capped by a geomorphic surface that is correlative across the basin (Figures 3.4B, D). The geomorphic surface is interpreted as a paleo-depositional plain that marks the maximum extent of sedimentation prior to integration of the modern Sutlej River drainage network.
After deposition, the basin was incised to basement by the Sutlej River, exposing the entire basin fill in spectacular canyons and cliffs. The best estimate for the age of the
Zhada Formation is 9.2 – < 1 Ma based on magnetostratigraphy (Figure 3.5)(Saylor et al., in press; Wang et al., 2008b). Correlations to the geomagnetic polarity timescale
(Lourens et al., 2004) were constrained by Mio-Pliocene mammal fossils and by an observed shift from pure C3 to mixed C3 and C4 vegetation in the Zhada basin. The correlation presented in Figure 5 accounts for all of our normal and reversed intervals; places the C3 – C4 transition at ~ 7 Ma, which is consistent with its age elsewhere in the
Himalaya; and yields relatively constant and reasonable sedimentation rates. For an in- depth discussion of alternative correlations see Saylor et al. (in press). 100
SEDIMENTOLOGY OF THE ZHADA FORMATION
We measured 14 stratigraphic sections spanning the basin from the Zhada county seat in the southeast to the Leo Pargil/Qusum Range front in the northwest (Figures 3.1B and 3.3B). Sections were measured at centimeter scale and correlated by tracing the prominent paleo-depositional surface that caps most sections and major stratigraphic units (Figures 3.4B, D and 3.6). The 14 lithofacies associations below are defined on the basis of lithology, texture and sedimentary structures, and are grouped into five depositional-environment associations. Lithofacies codes following the lithofacies associations below are modified from Miall (1978) and DeCelles et al. (1991) and described in Table 3.1. Unless otherwise indicated, all deposits are laterally continuous for 100’s of meters to several kilometers.
Fluvial Association
Lithofacies Association F1: Gcmi, Gch, Gt, Gcf.
F1 deposits are interbedded tabular and amalgamated lenticular pebble conglomerate bodies. Individual lenticular bodies are gravel- and pebble-filled and up to
3 m thick. Deposits are 2 – 10 m thick and typically have erosive bases (Figure 3.7E).
Deposits are moderately sorted and clast-supported. Clasts are rounded to subrounded and imbricated (long-axis-transverse). Some units display an upward-coarsening textural trend. Sedimentary structures include horizontal, trough and planar cross-stratification.
Tabular deposits are massive or contain horizontal stratification, large-scale (up to 4 m) 101 epsilon cross-stratification, and trough cross-stratified coarse-grained sandstone to pebble conglomerate lenses (Figure 3.7A).
Lithofacies Association F2: St, Sp, Sh, Sc.
F2 sandstone beds are tabular and range in thickness from less than 0.1 m to 5 m
(Figures 3.7C, D). Basal bounding surfaces are erosional and upper bounding surfaces are either erosional or gradational. Top bounding surfaces frequently display load casts, convoluted bedding, and ball-and-pillow structures and are often overlain by lithofacies association F3 (Figure 3.7G). Channel forms up to 3 m thick are common, but occur as isolated bodies rather than as amalgamated channel bodies. Grain-size varies from fine to very coarse and floating granules and granule lenses are common. Sorting is poor and grain size trends are absent. Sedimentary structures include horizontal, planar, and trough cross-stratification (Figures 3.7C, G). Horizontal stratification is common near the base of units and planar or trough cross-stratification is more common in the upper parts of units. Root traces, fragmentary plant material, and shell fragments are common, though less abundant than in lithofacies F3.
Lithofacies Association F3: Sm, Sc, Mm, Mc, Ml, Mh.
Deposits of dark, organic-rich, massive or horizontally laminated, calcareous siltstone or sandstone are < 0.1 – 4 m thick (Figures 3.7B, F). Basal surfaces are either gradational or feature load casts and ball-and-pillow structures. Upper surfaces are either gradational or erosional. These deposits are often upward-fining. Original sedimentary structures are in most places not discernible. The grain size is variable and can be up to medium-grained sandstone, though siltstone or very fine-grained sandstone is most 102 common. Shell fragments, including ostracods and small planorbid gastropods (Gyraulus sp?), plant material, and root traces are abundant in these deposits and are concentrated in the fine-grained upper portion of upward-fining beds (Figure 3.7B). No clearly developed soil nodules or soil horizons were observed. The δ18O values of shells systematically increase upward within individual units of F3 (Saylor et al., in press).
Lithofacies F3 primarily occurs interbedded with lithofacies F2.
Interpretation.
We interpret lenticular morphologies and tabular, cross-stratified deposits of interbedded clast-supported conglomerate and sandstone (F1) as the deposits of migrating or avulsing channels and migrating bars of a braided river system within a low-gradient, low aggradation rate, fluvial setting (Bristow and Best, 1993; Cant and Walker, 1978;
Collinson, 1996). Horizontally stratified units are interpreted as the product of migrating bedload sheets (Lunt et al., 2004). Tabular, cross-stratified units are interpreted as the deposits of gravel dunes (Heinz et al., 2003).
Tabular deposits in lithofacies F2 could be interpreted either as the result of sheetfloods (terminal splays or lobes) on medial to distal fluvial fans on a marshy floodplain or marginal lacustrine setting (Hampton and Horton, 2007; Saez et al., 2007) or as levee and crevasse splay deposits (Bridge, 2003). We favor the sheetflood origin based on the absence of wedge-shaped sandstone bodies; lateral continuity of deposits; absence of prograding, steeply-inclined slipfaces; and abundance of convoluted bedding in lithofacies F2 (Bristow et al., 1999). The abundance of convoluted bedding indicates 103 rapid sedimentation into a water-saturated environment, rather than periodic sedimentation followed by long periods of stability as implied by crevasse splays.
Further, sequence stratigraphic analysis indicates that lithofacies F2 occurs primarily updip of open lacustrine intervals (Saylor et al., in preparation). The presence of isolated channel forms associated with these deposits indicates that the flow was not completely unconfined, but rather occurred within and overwhelmed a distributary network.
Lithofacies association F3 is interpreted as marshy floodplain or lake-margin wetland deposits (Allen and Collinson, 1986). The upsection increase in δ18O values of shell from these lithofacies probably resulted from evaporative enrichment of standing water in paleo-marshes (Saylor et al., in press). Modern analogs to these are widespread along rivers on the Tibetan Plateau such as the Yarlung/Tsangpo in the vicinity of
Zhongba (Figure 3.1, N26°, E84°).
Supra-littoral (Lake Margin) Association
Lithofacies Association S1: Gct, Gcmi, Sp, St, Sh, Sm, Sr.
This lithofacies association consists of 0.25 – 6 m thick units of medium-grained sandstone to pebble conglomerate (Figure 3.8B). Deposits consist of sheets or amalgamated channel forms of upward-coarsening sandstone. Basal surfaces are erosional, and top surfaces are commonly a sharp transition to lithofacies association L1 and contain reworked shells and shell fragments. Sedimentary structures include horizontal, planar, and trough cross-stratification (Figure 3.8C). Thin lenses of fine- grained sandstone to granule conglomerate are common. Channelized deposits up to 0.5 104 m thick are locally present. This lithofacies association contains abundant, well- preserved, robust gastropod shells (Figure 3.8A), plant and shell fragments, and root traces. Lithofacies association S1 is often interbedded with F3.
Lithofacies Association S2: Sh.
Lithofacies association S2 is composed of low-angle climbing translatent strata without internal structure developed in well-sorted, fine-grained sandstone. Stacked deposits of sandstone laminae are < 0.5 – 5 m thick. This lithofacies can also be massive or disrupted by soft sediment deformation. Individual laminae range from less than 0.5 to
3 cm thick. Root traces and armored mud balls are common (Figure 3.8E).
Lithofacies Association S3: Sf.
Stacked deposits of sandstone foresets of lithofacies association S3 range from less than 0.5 m to 1.5 m thick. This lithofacies is characterized by steeply inclined laminations developed in well-sorted, fine-grained sandstone (Figure 3.8D). Laminations coarsen upward perpendicular to stratification. As with lithofacies S2, these deposits also can be massive or contain post-depositional soft-sediment deformation and abundant root traces. S3 is usually associated with S2.
Interpretation.
Root traces and preferential oxidation and cementation within lithofacies S1 and its close association with lithofacies F3 indicate deposition in extremely shallow water associated with lake-margin marshes or just above the shoreline (Ayers, 1986).
Sedimentary structures in lithofacies S1 indicate unidirectional flow. Therefore, 105 lithofacies association S1 is interpreted as delta plain and distributary channel deposits
(Dam and Surlyk, 1993; Saez et al., 2007).
Lithofacies S2 is interpreted as vegetated sand-flat deposits on the basis of root traces, the low angle of the laminations, and lack of internal structure in the laminations which is consistent with formation be migrating wind ripples (Hunter, 1977). S3 is interpreted as vegetated eolian dune deposits on the basis of the horizontal and vertical dimensions of the high angle cross-stratification. Interbedded units of F3 were deposited in interdune ponds and marshes. Modern analogs to environments proposed for lithofacies association S1 occur at Kungyu Co (Fig. 1, N30° 36’, E82° 11’) and modern analogs for environments proposed for lithofacies S2 and S3 occur both at Kungyu Co and to the west of Zhongba (Fig. 1, N26°, E84°).
Littoral Association
Lithofacies Association L1: Ml.
Lithofacies association L1 consists of papery laminated siltstone with abundant fossil grasses, fragmentary shell material, and occasional fish fossils (Figure 3.9).
Deposits are < 0.5 m thick and usually cap a coarser-grained deposit. Locally, bedded gypsum and mudcracks occur in these deposits.
Lithofacies Association L2: Mr, Sr, Srw, Sp, Sh, Sm.
Rippled sandstone deposits are ~ 0.5 – 3 m thick and coarsen upward. Lithofacies association L2 typically overlies lithofacies association P1 in gradational contact. The upper surfaces of L2 units are erosional and commonly overlain by either S1 or L1. This 106 lithofacies association is massive or contains climbing-ripples, horizontal, wave-ripple, planar cross-strata, and horizontal laminations. Grain size ranges from siltstone to medium-grained sandstone. Mud drapes are common.
Interpretation.
Based on modern analogs seen at Kungyu Co (Figure 3.1, N30° 36’, E82° 11’),
L1 represents a grass-rich, shallowly submerged, low-gradient, lake-margin environment
(Allen and Collinson, 1986; Talbot and Allen, 1996). L2 is interpreted as the deposits of a terminal lobe on a prograding delta front on the basis of consistency in thickness, sedimentary structures, and grading with modern analogs at Kungyu Co (Allen and
Collinson, 1986; Dam and Surlyk, 1993; Saez et al., 2007; Talbot and Allen, 1996).
Cross-stratification is consistent with both unidirectional and oscillatory currents. The presence of massive or climbing-ripple cross-stratified beds indicates that flow velocity was decreasing rapidly (Jopling, 1965; Miall, 1996; Mulder et al., 2003; Mutti et al.,
2003). The presence of wave-ripple cross-stratification in L2 points to a subaqueous depositional environment above fair-weather wave base. Thus, L2 is possibly the basinward lateral equivalent of lithofacies association S1.
Profundal Association
Lithofacies Association P1: Mh, Mm.
The P1 siltstone lithofacies association is composed of upward-coarsening, massive or horizontally laminated silty claystone (Figures 3.10A, B). Deposits are < 1 up 107 to 10 m thick. There is no evidence of flow associated with this lithofacies. Dispersed plant, ostracod, and fish fossils are present in this lithofacies.
Lithofacies Association P2: Sh, Sm, Mh.
This lithofacies association is composed of stacks of very thin, tabular, upward- fining beds of fine-grained sandstone to siltstone (Figure 3.10C). Beds are up 3 centimeters thick and are stacked up to 2 m thick. Individual beds are massive in their lower part but grade upward into horizontally laminated siltstone in their upper parts.
Basal contacts of individual beds are abrupt.
Interpretation.
The lack of traction sedimentary structures, fine-grain size, and presence of fish fossils indicate that P1 was deposited below fair-weather wave base in a profundal setting. P1 mudstones are often massive owing to extensive bioturbation, suggesting that the lake was not well stratified and hence probably shallow. The sharp bases, massive lower portions, horizontally stratified upper portions, and upward-fining beds of lithofacies association P2 represent stacked deposits of dilute turbidity current deposits
(primarily Bouma A and B) (Bouma, 1962; Giovanoli, 1990). The interbedding of lithofacies P1 and P2 suggests an environment in which stagnant water was occasionally disrupted by turbid flow, bringing anomalously coarse-grained sediment into the profundal lake bottom (Lowe, 1982; Mutti et al., 2003).
108
Alluvial Fan Association
Lithofacies Association A1: Gcm, Gch, Gcmi.
Deposits of clast-supported, very angular to subrounded, pebble to boulder conglomerate range from 0.5 – 20 m thick and typically have erosive bases (Figure
3.11A). Clast a-axes are up to 0.5 m long. Deposits are massive and locally horizontally stratified. They are poorly sorted and contain long-axis-transverse imbrication. Cross- stratification and channel forms are extremely rare. However, interbedded medium- grained sandstone to granule conglomerate lenses are common. In the central part of the
Zhada basin this lithofacies is distinguishable from F1 by its coarser grain-size, poorer sorting, and abundance of white quartzite clasts.
Lithofacies Association A2: Gmm, Gcm.
Deposits of matrix-supported boulder conglomerate are between 0.5 and 3 m thick and do not have erosive bases. Grain-size, angularity and sorting are similar to lithofacies A1. These deposits are massive and highly disorganized (Figure 3.11B).
Lithofacies Association A3: Gcmi, Gch, Gcf.
This lithofacies association is composed of very angular to subrounded, pebble to boulder conglomerate in beds that range from 0.5 to 3 m thick and typically have erosive bases. Sedimentary structures include horizontal- and cross-stratification. Lenticular beds are common. Lithofacies association A3 is poorly sorted, clast-supported and contains long-axis-transverse imbrication and interbedded medium-grained sandstone to pebble conglomerate lenses.
Lithofacies Association A4: Gx. 109
A4 is characterized by chaotic beds of clast- or matrix-supported, very poorly sorted boulder conglomerate. Indvidual deposits are < 0.5 m – 5 m thick and often fine upwards. Clasts are subrounded to angular. Deposits often have a winnowed, matrix- poor, cap < 0.5 m thick. These deposits have abundant load casts and ball and pillow structures, with up to 2 m of relief on some structures (Figure 3.11C). Lithofacies A4 is closely associated with lithofacies F3 as well as P1 and P2.
Interpretation.
The presence of imbricated clasts in A1 indicates transport by traction flows.
However, the lateral continuity of these deposits and paucity of channel forms imply unconfined flow. We interpret lithofacies A1 as high-concentration, sheetflood deposits
(Blair, 2000; Blair and McPherson, 1994b). Traction, dispersive pressures and buoyancy probably all contributed in varying degrees to transport the sediment (e.g., DeCelles et al., 1991; Nemec and Steel, 1984; Pierson, 1980, 1981). Alternatively, A1 may represent the deposits of shear-modified grain flows ("traction carpet" of Heinz and Aigner, 2003;
Sohn, 1997; Todd, 1989), in which dispersive forces combined with traction to produce the unstratified, but imbricated deposits. Shear- and buoyancy-modified grain flows commonly develop beneath high-concentration floods (Todd, 1989).
We interpret lithofacies A2 as debris-flow deposits due to the lack of erosion at the base and matrix-support, which indicates a high viscosity, laminar flow (Pierson,
1980). Massive, disorganized, clast-supported cobble to boulder conglomerate deposits 110 are interpreted as non-cohesive debris flows (Blair and McPherson, 1994a; Nemec and
Steel, 1984).
Given the combination of clast imbrication, abundant channel forms and coarse grain-size, we interpret lithofacies A3 as stream deposits in a stream-dominated alluvial fan setting (DeCelles et al., 1991).
Following Nemec and Steel (1984) and on the basis of similar deposits seen on the margins of Kungyu Co, we interpret lithofacies A4 as high-concentration flood or debris flow deposits that accumulated in a water saturated environment (Miall, 2000;
Postma, 1983), associated with both supra-littoral (F3) and profundal (P1 and P2) settings. Winnowed cobble intervals capping some A4 deposits are interpreted as the result of post-depositional wave reworking during subsequent lacustrine transgression
(Blair, 2000; Pivnik, 1990).
Zhada Formation members
We identified five members of the Zhada Formation based on lithofacies assemblages (Figures 3.3 and 3.12). The lower conglomerate member (Nlc) consists of lithofacies associations F1, F2, and rare F3. Where present, it extends from the base of the section to the top of the last F1 interval >1 m thick. Above this, the lower fluvial member (Nlf) consists of lithofacies associations F2, F3, S2 and S3 and extends from the top of the lower conglomerate member to the base of the lacustrine claystone. The lacustrine member (Nl) includes primarily lithofacies associations P1, P2, L1, L2, S1 and minor S2, S3 and F2. The lacustrine member extends from the first occurrence of 111 lacustrine claystone to the first thick (>1 m) interval displaying soft-sediment deformation. The upper fluvial member (Nuf) is similar to the lower fluvial member with the exception that it tends to be coarser and contain more abundant soft-sediment deformation. This member is composed primarily of sand – boulder-sized material in contrast to the lower fluvial member which is dominantly silt – sand-sized material. The upper fluvial member extends from the lacustrine member to the first significant (>10 m thick) conglomeratic interval. The upper alluvial fan member (Nal) includes lithofaces associations A1-A4, F3, P1 and P2. It extends from the first significant conglomeratic interval above the lacustrine member to the top of the section, which is defined by a regional geomorphic surface that caps the Zhada Formation.
112
PALEOCURRENT MEASUREMENTS
Paleocurrent data consist of measurements of 298 limbs of trough cross-strata
(method I of DeCelles et al., 1983) at 29 sites and measurements of 568 long-axis- transverse imbricated clasts at 47 sites in measured sections throughout Zhada basin
(Figure 3.6).
Paleocurrent measurements fall into two general groups: those that show a northwestward paleoflow direction and those directed toward the basin-center. The first group comes from the lower two members of the Zhada Formation (Nlc and Nlf). The average paleocurrent azimuth from 8 measured sections in the lower members ranges between 270° and 349° (Figure 3.13A, Table 3.2). The second group of measurements come from the two upper members (Nuf and Nal) or anomalously coarse-grained tongues
(cobble – boulder) within lower members. These paleocurrent indicators are less uniform but generally indicate flow towards the center of the basin in seven of the nine measured sections (Figure 3.13B, Table 3.2). In the northwest end of the basin there is a trend from uniformly northwestward directed paleo-flow (Qusum section, Figure 3.13A) to a more complex, but average northwestward directed paleo-flow (1NWZ and 2NWZ sections) and finally a complete reversal to an eastward average paleo-flow direction (3NWZ section, Figure 3.13B).
113
PROVENANCE ANALYSIS
Methods
Sandstone petrography and conglomerate clast counts
Modal sandstone composition data come from 35 standard petrographic thin sections from 9 measured sections across the basin. Thin sections were stained for potassium and calcium feldspar and point-counted (403 - 744 counts per slide) using a modified Gazzi-Dickinson method (Ingersoll et al., 1984); the modifications involve the identification of monocrystalline quartz grains that are part of sedimentary lithic fragments and counting carbonate grains. The petrographic counting parameters are shown in Table 3.3, and recalculated modal data are given in Table 3.4.
Conglomerate composition data consist of identification of 3447 clasts from 32 sites from measured sections throughout Zhada basin, and bedloads of several modern streams and rivers. Conglomerate-clast counts involved identification of clast lithology of ~ 100 clasts at regular intervals from within individual beds. Bedload counts involved identification of ~100 gravel-sized or larger clasts that were dredged from the streambed.
U-Pb geochronologic analyses of detrital zircons
U-Pb geochronology was conducted on zircons separated from nine sandstone samples and one paragneiss sample from the Zhada basin and the footwall of the Qusum
Detachment, respectively, and were processed for detrital zircon analysis using standard procedures described by Gehrels (2000) and Gehrels et al. (2008). Analysis was conducted using the laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICPMS) at the Arizona LaserChron Center. Approximately 100 114 individual zircon grains were analyzed from each sample (with the exception of samples
2EZ88 and 2EZ60.7A). These were selected randomly from all sizes and shapes, although grains with obvious cracks or inclusions were avoided. In-run analysis of fragments of a large zircon crystal (generally every fifth measurement) with known age of 564 ± 4 Ma (2-sigma error) was used to correct for inter- and intra-element fractionation. The uncertainty resulting from the calibration correction is generally 1-2%
(2-sigma) for both 206Pb/207Pb and 206Pb/238U ages. Common Pb was corrected by using the measured 204Pb and assuming an initial Pb composition from Stacey and Kramers
(1975) (with uncertainties of 1.0 for 206Pb/204Pb and 0.3 for 207Pb/204Pb).The analytical data are reported in Table S5. Details of the operating conditions and analytical procedures can be found in Gehrels et al., (2008).
For each analysis, the errors in determining 206Pb/238U and 206Pb/204Pb result in a measurement error of ~1-2% (at 2-sigma level) in the 206Pb/238U age. The errors in measurement of 206Pb/207Pb and 206Pb/204Pb also result in ~1-2% (at 2-sigma level) uncertainty in age for grains that are >1.0 Ga, but are substantially larger for younger grains due to low intensity of the 207Pb signal. For most analyses, the cross-over in precision of 206Pb/238U and 206Pb/207Pb ages occurs at 0.8-1.0 Ga. Interpreted ages are based on 206Pb/238U for < ~300 Ma grains and on 206Pb/207Pb for > ~300 Ma grains.
Though 206Pb/238U ages are more precise below 1 Ga, the occurrence of numerous zircon grains with lead loss due to Cenozoic metamorphism necessitated a younger cutoff.
Analyses with > 20% uncertainty, that are >30% discordant (by comparison of 206Pb/238U and 206Pb/207Pb ages) or >5% reverse discordant are omitted from interpretation. 115
Results
Sandstone and conglomerate modal compositions
Quartz is present in monocrystalline (Qm), polycrystalline (Qp), and foliated polycrystalline (Qpt) grains, and also monocrystalline grains within sandstone or quartzite grains (Qms)(Figure 3.14). Qp commonly occurs within granitoid lithic grains.
Qpt commonly occurs within mylonitic lithic grains. Other lithic grains include phyllite
(Lph), schist (Lsm), carbonate (Lc), chert (C), and mudstone (Lsh). Volcanic grains are common, particularly at the base of the Zhada Formation. The most abundant are felsic volcanic grains (Lvf). This group includes porphyritic, highly altered quartzofeldspathic grains, quartz rich grains with disseminated plagioclase, and volcanic grains that include exotic lithic fragments. The latter are interpreted as volcaniclastic. Mafic volcanic grains
(Lvm) are likewise highly altered; often serpentenized or chloritized. Lath-work volcanic grains (Lvl) contain lath-shaped plagioclase crystals and are typically felsic in composition. Vitric volcanic grains (Lvv) are those with pseudo-isotropic textures.
These commonly resemble chert, but, where stained, have taken a pink plagioclase stain.
In most thin sections plagioclase (P) is slightly more abundant than potassium (K) feldspar. Both biotite and muscovite are present in most samples with muscovite typically being more common. Accessory minerals include zircon, tourmaline, garnet, olivine, serpentine, chlorite, and cordierite. The most abundant cement is carbonate with secondary occurrences of gypsum cementation.
Sandstones from the lower conglomeratic and fluvial members (Nlc and Nlf) of 116 the Zhada Formation consist of poorly lithified carbonate or gypsum cemented litharenites. Subrounded to subangular lithic grains, including polycrystalline quartz, are the dominant constituents with lesser amounts of monocrystalline quartz grains (Figures
3.15B, E, H). The lithic fraction is dominated by felsic and vitric volcanic grains (Lvv and Lvf) (Figures 3.15C, I). Feldspar comprises 10 – 20 % of the total compositions with plagioclase being slightly more abundant. Whereas volcanic grains are the most abundant lithic grains in lower member sandstones, in some samples up to 66% of the lithic portion is composed of either metamorphic (such as Qpt) or sedimentary (such as limestone, phyllite or mudstone) lithic grains (Figure 3.15C samples 0SZ1 and 0.2SZ30).
As in the lower members, sandstones from the upper members consist of poorly lithified carbonate or gypsum cemented litharenites. However, starting in the middle of the lower fluvial member (Nlf) the composition of sandstones changes abruptly. This is particularly evident in the lithic fraction, which changes from being dominated by volcanic grains to sub-equal amounts of sedimentary and metamorphic grains (Figures
3.15C, I) or entirely metamorphic grains (Figure 3.15F). Feldspar constitutes a larger component of upper-member sandstones (10 – 55% of the total), with the proportion of feldspar increasing upsection. Plagioclase dominates over alkali feldspars. In contrast to lower member sandstones, volcanic lithic grains are a minor constituent of upper member sandstones.
Conglomerate clast count data are consistent with modal sandstone analyses.
Sedimentary and volcanic clasts dominate the lower members of the Zhada Formation and metamorphic and plutonic clasts are a minor component (see clast count pie charts in 117
Figure 3.6). Upsection, metamorphic clasts become more abundant and volcanic clasts less so (Fig. 6).
U-Pb geochronologic analyses of detrital zircons
A total of 840 new zircon ages from ten samples are reported here (Figure 3.16).
The preferred ages are shown on relative age-probability diagrams (from Ludwig, 2003).
These diagrams show each age and its uncertainty (for measurement error only) as a normal distribution, and sum all ages from a sample into a single curve (Figure 3.17).
Sample LC58.15 yielded 102 usable ages (Figures 3.16 and 3.17). Zircons ranged from euhedral to well rounded. The largest population is between 45 and 50 Ma (peak at
48 Ma). Additional populations occurred at 20 – 25 Ma (peak at 23 Ma), 50 – 65 Ma
(peaks at 56 and 61 Ma), 550 – 650 (peak at 620 Ma), 1100 – 1200 Ma (peak at 960 Ma) and 2450 – 2500 Ma (peak at 2500 Ma).
Sample 2EZ60.7A yielded only 23 usable ages (Figures 3.16 and 3.17) due to a paucity of zircons in the sample. Zircons were largely euhedral or angular (broken). The largest age population occurred between 45 and 55 Ma (peaks at 48 and 54 Ma). The only other reliable age population is between 1150 and 1200 Ma (peak at 1170 Ma).
However, a broad group of ages cluster at 450 – 700 (peak at 500 Ma) and a few (n<3) occur at 20 – 25 Ma (peak at 20 Ma).
Sample 2EZ66.5 yielded 92 usable ages (Figures 3.16 and 3.17). Zircons were sub-angular to well rounded. The largest age population is between 55 and 60 Ma (peak at 58 Ma). Additional populations occur between 45 and 50 Ma (peak at 48 Ma), between 85 and 95 Ma (peak at 92 Ma), at 520 Ma, between 900 and 1100 Ma (peak at 118
930 Ma) and between 2500 and 2700 Ma (peak at 2640 Ma). There are also a number of ages at 15 – 25 Ma (dual peaks at 17 and 22 Ma), 1250 – 1400 Ma and 1750 – 1850 Ma.
Sample 2EZ88 yielded 52 usable ages (Figures 3.16 and 3.17). Zircons from this sample were euhedral to well rounded. The largest age population is between 45 and 60
Ma (peak at 48 Ma). There is a small cluster (n<3) with peaks at 17 and 21 Ma. Older populations have peaks at 480 Ma and 940 Ma. Additional scattered ages from 15 – 25
Ma (peaks at 17 and 21 Ma) and 2400 – 2700 Ma have too few zircons to compose reliable age populations.
Sample 4SZ14 yielded 105 usable ages (Figures 3.16 and 3.17). Zircons ranged from euhedral to well rounded. The largest and youngest age population has a peak at
480 Ma. Additional populations occur in the range of 850 – 1150 Ma (peak at 910 Ma) and at 2500 Ma. Scattered ages occur between 1300 and 1700 Ma and again around 2000
Ma. However, too few zircons occur in these last groups to consider them reliable populations.
Sample 2NWZ2.5 yielded 91 usable ages (Figures 3.16 and 3.17). Zircons ranged from sub-angular to well-rounded, though most were sub-rounded to rounded. The largest population was at 30 - 40 Ma (peak at 36 Ma). Secondary populations occurred at
40 - 50 Ma (peaks at 44 and 46 Ma), 500 – 650 Ma (broad peak at 590 Ma), 800 – 900
Ma (peak at 860 Ma) and between 1050 and 1150 Ma (peak at 1090 Ma). Two additional clusters have peaks centered at 1660 Ma and 1890 Ma but each cluster is composed of <
3 zircon ages.
Sample 2NWZ58.2 yielded 92 usable ages (Figures 3.16 and 3.17). Zircons 119 ranged from euhedral or angular to well rounded, though most were sub-rounded to rounded. The largest age population was from 30 – 50 Ma (peaks at 35, 37, 43 and 48
Ma). Secondary populations occurred at 650 – 700 Ma (peak at 660 Ma) and 900 – 1050
Ma (peak at 960 Ma). One additional cluster occurs between 2450 and 2600 Ma but is represented by too few zircons to be a reliable age population.
Sample 3NWZ45.9 yielded 85 usable ages (Figures 3.16 and 3.17). Zircons were sub-rounded to well rounded. Discrete age populations were difficult to identify due to lead loss during Cenozoic metamorphism. The largest age population was between 750 and 1150 Ma. Additional populations occurred from 450-500 (peak at 480 Ma), 550-650
Ma (peak at 600 Ma) and 2050-2100 (peak at 2080 Ma). As with 2NWZ58.2 another cluster occurs between 2400 and 2550 Ma but is has too few zircon ages to be a considered a population.
Sample 3NWZ77 yielded 92 usable ages (Figures 3.16 and 3.17). Zircons were sub-rounded to well rounded. The largest age population was between 800 and 1100 Ma
(peaks at 830, 950, 1000 and 1080 Ma). Additional populations occurred at 40 – 50 ma
(peaks at 41 and 45 Ma), 550 – 600 Ma (peak at 570 Ma), 650 – 700 Ma (dual peaks at
660 and 690 Ma), 1150 – 1200 Ma (peak at 1170 Ma) and 2050 – 2100 Ma (peak at 2090
Ma).
Sample SMZ 35 yielded 106 usable ages (Figures 3.16 and 3.17). Zircons were sub-angular to well rounded. The largest age population was between 900 and 1150 Ma
(peak at 1050 Ma) with secondary populations at 450 – 500 Ma (peak at 480 Ma), 550 –
650 Ma (minor peak at 580 Ma), 1300 – 1350 Ma and 1400 – 1450 Ma (peak at 1430 120
Ma).
Summary of detrital zircon U-Pb analyses
Samples fall broadly into two groups: those with significant detrital-zircon ages >
100 Ma and those with almost exclusively < 100 Ma detrital-zircon ages (Figure 3.17).
Analyzed zircons were euhedral to well rounded. There was no correlation between the degree of rounding and zircon age. The youngest zircon age population is 23 Ma (n=8,
LwrCgm58.15) though a small cluster (n=2) are as young as 17 Ma (2EZ66.5, Figure
3.17, Table 3.5). The youngest detrital zircon ages are well above the oldest depositional age. The > 100 Ma age population has prominent peaks at 450-550, 800-1200, and 2500
Ma and minor peaks at 550-650, 1300-1450 and 2100 Ma. The < 100 Ma population has major peaks at ~35, 45-50, and ~55 Ma and minor peaks at 17-23, 60-65 and 90-100 Ma.
Interpretation
Sandstone and conglomerate provenance
Detrital modes of sandstones show an upsection shift from an arc-orogen source to a recycled-orogen source. The lowermost samples are from sandstones within the fluvial Nlc and Nlf members. Their lithic fractions fall largely within the arc-orogen- source field in Qp-Lv-Ls ternary diagrams and straddle the border between the arc- orogen and recycled-orogen fields in Qm-F-Lt and Qt-F-L diagrams (Figure
3.15)(Dickinson, 1985). Sandstone compositions from the top of the Nlf member are more scattered but trend towards the quartzose, recycled-orogen fields in all ternary diagrams (Figure 3.15). Samples from the upper members of the Zhada Formation (Nl, 121
Nuf, Nal) continue the trend towards more compositionally mature, recycled-orogen sources, even extending into the continental block field in Qm-F-Lt and Qt-F-L diagrams
(Figures 3.15G, H). These trends are also present in samples from the northwestern part of Zhada basin (Figure 3.15E, F). Increasing input of detritus from recycled-orogen terranes is most evident in the Qp-Lv-Ls diagram for the northwest Zhada section, but lacks the volcanic rich endmember (Figure 3.15F).
The primary source of volcanic detritus for samples from the fluvial interval of the lower member of the Zhada Formation is interpreted to be the Mt. Kailas region to the northeast of Zhada basin (north of the Karakoram fault, Figures 3.1 and 3.13). The region south of the Zhada basin is dominated by high-grade metamorphic rocks and the only local sources of volcanic detritus are relatively small zones of ophiolitic rocks in the
Tethyan Himalaya. However, ophiolitic rocks are a minor source given the paucity of mafic volcanic fragments in the Zhada Formation. In contrast, the Mt. Kailas region is dominated by both volcanic and plutonic rocks associated with the Cretaceous - Tertiary
Gangdese magmatic arc and younger clastic rocks derived from these igneous rocks
(Aitchison et al., 2002; Murphy and Yin, 2003; Murphy et al., 2002; Yin et al., 1999).
This area is also the headwaters of the modern Sutlej River (Figure 3.13B). Probable sources of the recycled-orogen detritus which dominates the upper members of the Zhada
Formation include rocks in the Ayi Shan mountains northeast of the basin, the Tethyan sequence strata which underlie the basin, and the Greater Himalayan and Tethyan sequence rocks southwest of the basin. Greater Himalayan rocks are also exposed in the core of the Gurla Mandhata metamorphic core complex to the southeast of Zhada basin 122
(Murphy, 2007). The modal petrography points to an upsection shift from a northeasterly source to source located southwest of the Karakoram fault. The enrichment in recycled- orogen detritus is also evident in the northwestern Zhada basin. However, being farther from the inferred source of volcanic detritus, the initial volcanic fraction is reduced and so the evolution from an arc-orogen dominated source to a more quartzose source is not as dramatic as in central Zhada basin.
Data from conglomerate clast counts increase the resolution of the provenance interpretation. Like the petrographic and detrital zircon data, the clast counts show an upsection decrease in the abundance of volcanic detritus and an increase in the relative abundance of high-grade metamorphic and plutonic clasts. Particularly on the southern margin of the basin, where paleocurrent indicators from the upper members of the Zhada
Formation show northward paleoflow directions, the only source of high-grade metamorphic and plutonic clasts is the Greater Himalayan sequence to the south of Zhada basin. However, low-grade metasedimentary clasts dominate the clast counts throughout the basin, indicating that the local Tethyan basement was a significant source of detritus.
In the northern and northwestern parts of the basin, paleocurrent data indicate that high- grade metamorphic and plutonic rocks were derived from the footwall of the Qusum detachment. Consistent with greater distance from the source of volcanic rocks (the
Kailas Range), the ratio of volcanic clasts to other clasts is lower in the northwestern
Zhada basin than in the central Zhada basin. The conglomerate clast count data indicate that the source of sediments in the Zhada basin changed from a distal, northeastern source, with local input, to a predominantly proximal southwestern source. 123
An unexpected result of the conglomerate clast counts is the dominance of low- grade metamorphic rocks over volcanic rocks in the lower members of the Zhada
Formation. There is an apparent disconnect between the relative abundance of detritus derived from northeast of Zhada basin indicated by the detrital zircon data and the conglomerate clast count data. One possible reason for this is downstream grain-size sorting; this explanation is consistent with a more distal northeastern source and a more proximal local or southwestern source.
U-Pb geochronologic analyses of detrital zircons
Samples with significant detrital-zircon ages < 100 Ma and those with almost exclusively > 100 Ma ages (Figure 3.17) come from the bottom and top of the Zhada
Formation, respectively. Possible sources for detrital zircons include the Cretaceous –
Tertiary volcanic and intrusive igneous rocks related to Gangdese (Kailas) arc magmatism, Paleozoic – Mesozoic metasedimentary rocks of the Tethyan Sedimentary sequence or late Proterozoic – early Paleozoic rocks of the Greater Himalayan seqeuence.
There is good correlation between most of the < 100 Ma peaks with igneous or detrital zircon age spectra from regions north of Zhada basin (Mt. Kailas or Ayi Shan regions, Figure 3.17). Specifically, peaks at 17 – 23 Ma, ~ 55 Ma and 78 – 80 Ma correlate to peaks in the igneous or detrital zircon age spectra from the Mt. Kailas area
(Figure 3.17 ―Source Regions‖). However, there are no good correlations from this region for peaks between 35 and 50 Ma. A better match for these peaks can be found in detrital zircons from the Ayi Shan. Ayi Shan zircons also may contribute to the 78 – 80
Ma peak in the Zhada basin (Figure 3.17 ―Source Regions‖). The only documented 124 source for ~ 55 Ma zircons is from the Gangdese arc (Figure 3.17).
Ages of detrital zircons from samples from the top of the Zhada Formation (e.g.,
4SZ14, 3NWZ45.9 and 3NWZ77) are dominantly Paleozoic – Proterozoic and those zircons cannot have been derived from the Mt. Kailas region. The Neogene Kailas
Formation has a greater proportion of < 100 Ma zircons than do the samples mentioned above (Figure 3.17, ―Kailas‖). Hence, the Kailas Formation may be a minor source, but the major source of detritus must lie elsewhere. Likely sources include inherited zircons from Ayi Shan paragneisses or leucogranites which have Tethyan sequence protoliths, the
Tethyan sequence basement, or Greater Himalayan sequence rocks (DeCelles et al., 2004;
DeCelles et al., 2000; Gehrels et al., 2006a, b; Gehrels et al., 2008; Martin et al., 2005).
Consistent with the petrographic data, the detrital zircon data shows a significant upsection shift from a source in the Mt. Kailas area to a local basement or southernwestern source.
125
SUBSIDENCE CURVE
A tectonic subsidence curve for the Zhada basin was produced from the South
Zhada section by decompacting the sediments using standard basckstripping techniques
(Figure 3.18A "Decompacted subsidence curve") (Allen and Allen, 1990; Dickinson et al., 1987; Vanhinte, 1978) and then removing the load of the sediment assuming Airy isostacy (Figure 3.18A ―Tectonic subsidence curve‖). Age control is based on magnetostratigraphic tie points (Figure 3.5)(Saylor et al., in press). Bathymetry is not expected to be a major contributor to the accommodation because the lake was never more than a few tens of meters deep based on the thickest observed upward-coarsening parasequence within the Zhada Formation. The essentially linear Zhada basin curve best matches typical subsidence curves from strike-slip or rift basins (Figure 3.18B).
However, the subsidence rates are very low: 0.09 mm/yr and 0.06 mm/yr for the decompacted and tectonic subsidence curves, respectively. In addition, compared to classic examples of rift or strike-slip basins, the Zhada basin has a remarkably thin basin fill. Closer examination of the tectonic subsidence curve indicates that it can be divided into three linear segments: 9.23 – 5.23, 5.23 – 2.581, and 2.581 – 0.08 Ma. These segments have subsidence rates of 0.05, 0.1, and 0.03 mm/yr, respectively. The thin basin fill and the subsidence rate between 5.23 and 2.581 Ma are characteristic of supradetachment basins (Friedmann and Burbank, 1995).
126
DISCUSSION
Zhada Basin Evolution
Sedimentology and paleocurrent data indicate that a large, northwestward- flowing, low-gradient river deposited the lower members (Nlc, Nlf) of the Zhada
Formation. Whereas this may seem to contradict the argument for a northern source for the volcanic detritus based on petrography, clast composition, and detrital zircon analyses, we note that the modern Sutlej River has its headwaters in the Mt. Kailas region, flows southward into, and then northwestward across the Zhada basin and currently exits the basin to the southwest (Figure 3.13B). The paleo-Sutlej River also may have followed a similar path into the Zhada basin and northwestward from there.
Paleocurrent indicators at the base of the Zhada Formation are oriented northwestward even within 10 km of the modern Qusum range-front, indicating that, at the time that the sediments were deposited, the Leo Pargil/Qusum Range presented no obstacle to northwestward flow.
Upsection, paleocurrent indicators, provenance data, and sedimentology indicate that the Zhada basin became closed and that detritus was derived from local highlands surrounding the basin. The change from a through-going, northwestward flowing river to a closed basin demands explanation. Northwestward paleo-flow suggests that the cause of ponding within Zhada basin is to be found to the northwest. Deformation and growth structures (Figure 3.19) in the Zhada Formation in the northwest of the basin, near the
Leo Pargil/Qusum Range, indicate that movement on the Qusum detachment and exhumation of the range were synchronous with deposition of the Zhada Formation. It is 127 unlikely that the Zhada basin was entirely hydrologically closed because a large river, such as the Sutlej, would have quickly filled and overflowed a closed basin. Some outflow probably continued either via a small outlet in the southwest of the basin or groundwater flow which would have been missed by paleocurrent data. However, paleocurrent indicators and provenance data show that major surface flow during the
Pliocene-Pleistocene was basin-centric and stable isotope data indicate that the lake underwent significant evaporation (Saylor et al., in press).
Some of the complexity in the paleocurrent directions results from diversion around pre-existing topography and sediments being shed from pre-existing topography.
The presence of Zhada basin sediments in buttress unconformity on top of deformed
Tethyan sequence strata indicates that there was some paleo-topography on the basement prior to deposition of the Zhada Formation. In measured sections located near Tethyan basement rocks, alluvial fan facies interfinger with fluvial facies. Paleocurrent indicators from alluvial fan facies are commonly at high angles to those from axial fluvial facies.
This was observed particularly in the northwestern end of the basin and near the Guga section and is the cause of the anomalous northward oriented petals on the 2NWZ,
3NWZ and 1NZ rose diagrams and east or southward oriented petals on the Guga rose diagrams (Figure 3.13). These data add detail to environmental reconstructions, but do not change the overall basin evolution picture.
128
Tectonic Origins of the Zhada Basin
Any model for Zhada basin must explain (1) why there was a transition from non- deposition to deposition at ~ 9.2 Ma, (2) the relationship of the Zhada Formation to pre- existing topography in the Tethyan fold-thrust belt, (3) the variety and stacking patterns of depositional environments in the Zhada Formation, (4) the lack of widespread deformation in the Zhada Formation, (5) the lack of cyclic incision and infilling or significant hiatuses in sedimentation in the Zhada Formation, and (6) the transition from deposition to non-deposition and incision at < 1 Ma.
All evidence indicates that closure of the Zhada basin was the result of uplift of the Gurla Mandhata and Leo Pargil domes. The only basement-involved deformation observed in the Zhada Formation is a growth structure at the northwestern end of the basin, ~ 10 km from the Qusum detachment fault (Figure 3.19). The growth-stratal geometry is best explained by progressive sedimentation and rotation of basin sediments in the proximal hanging wall above a blind, upward-propagating normal fault (Gawthorpe and Hardy, 2002; Gupta et al., 1999; Sharp et al., 2000). The elongate shape of the
Zhada basin and its proximity to the Karakoram dextral fault also points to a pull-apart origin as a possibility. If the Zhada basin is a transtensional pull-apart basin, the Gurla
Mandhata and Leo Pargil/Qusum detachments act as step-over structures. Thus, the
Zhada basin could be a hybrid supradetachment/strike-slip basin. If this is the case, the lack of widespread deformation in the Zhada Formation implies strain localization on the detachment faults. These structures can also accommodate arc-parallel extension and be 129 the primary controls on Zhada basin evolution in the absence of a large strike-slip fault on the southwestern margin of the basin (see Synthesis below).
The onset of sedimentation in Zhada basin at ~ 9.2 Ma is within error of the oldest
AFT ages determined by Thiede et al. (2006) from the west side of the Leo Pargil Dome.
The presence of ~15 Ma 40Ar/39Ar cooling ages, from both the west side of the Leo Pargil
Dome and the east side of the Leo Pargil/Qusum Range, has been used to argue for a mid-Miocene onset of exhumation (Thiede et al., 2006; Zhang et al., 2000). Those ages, however, may reflect cooling during slip on the Main Central thrust (MCT) (Robinson et al., 2006; Robinson et al., 2003). This is borne out by the occurrence of abundant early to mid-Miocene 40Ar/39Ar cooling ages from the Greater Himalayan and Tethyan sequences on the south flank of the Himalaya (Metcalfe, 1993; Robinson et al., 2006; Thiede et al.,
2005; Vannay et al., 2004). Thus, the mid-Miocene cooling ages obtained from the Leo
Pargil/Qusum Range may be inherited from tectonic events related to arc-normal thrusting rather than arc-parallel extension. The synchroneity of movement on the
Karakoram fault in the Zhada region (10 Ma; Murphy et al., 2000; Yin et al., 1999) and exhumation of Gurla Mandhata (9 Ma; Murphy et al., 2002) with the 9-10 Ma AFT ages from Leo Pargil and the 9.2 Ma onset of sedimentation in Zhada basin points to the late
Miocene as the time of major structural reorganization in the area. The increase in tectonic subsidence rate at 5.23 – 2.581 Ma was synchronous with the onset of lacustrine sedimentation in the Zhada basin and also with an increase in exhumation rate indicated by AFT ages from the west side of the Leo Pargil dome (Thiede et al., 2006). This further implicates exhumation of the Qusum/Leo Pargil range as a controlling factor in 130
Zhada basin development.
The occurrence of an anomalous valley striking orthogonally across the Leo
Pargil/Qusum Range which may be a windgap (32.33°N, 79°E, Figure 3.20) further supports this explanation. This is the only significant valley in an otherwise unbroken mountain range. The valley extends through the entire width of the range and yet is currently occupied by an underfit stream < 1 m deep and < 5 m wide. This stream originates at a glacier mid-way through the valley and thus cannot account for a valley transecting the entire range. The valley is mantled by terrace deposits that have recently been incised (Figure 3.20B). We tentatively interpret this valley as the course of the paleo-Sutlej River prior to exhumation of the Leo Pargil/Qusum Range. If this is the case, the paleo-Sutlej may have been the headwaters of either the Indus or the Chennab
Rivers as suggested by Brookfield (1998).
Several explanations for the existence of the Zhada basin can be ruled out based on the variety and stacking patterns of lithofacies assemblages in the Zhada Formation.
The basin has none of the lithologic, stratigraphic or structural features of flexural or rift basins. Whereas the subsidence curve superficially matches that of other rift basins, the
Zhada Formation is much thinner than typical rift basin fill (Friedmann and Burbank,
1995) and mapping of the northeastern and southwestern margins of the basin revealed no geometric relationships other than onlap of basin sediments onto the basin bounding highlands. In no place along these margins is the basin fill faulted. Further, the tectonic subsidence curve does not match the classic upward convex foreland basin subsidence 131 curve; this is consistent with the absence of either a flexural load or the asymmetric cross-sectional shape typical of a flexural basin (Figures 3.12 and 3.18).
The duration of the basin and the lack of incision or hiatuses in sedimentation indicate that climate change was not the direct cause of sedimentation. It is difficult to envision a scenario in which climate change, acting alone, would initiate sediment accumulation and basin development, produce the variety of sedimentary environments archived in the Zhada Formation, drive continuous sedimentation for ~ 9 Myr, and then abruptly terminate deposition and return to an erosional, incising state. The basin could also be the result of damming by landslides, glaciers or tectonic activity. However, the duration of the basin and the lack of glacial deposits argue against the first two causes, leaving only structural damming as a viable possibility.
Likewise, the South Tibetan detachment system (STDS) is not the primary controlling structure for the Zhada basin. The Zhada Formation on the southwestern margin of the basin is undeformed and onlaps preexisting topography on the southwestern margin of the basin. There is no evidence of active faulting or basin deformation where mapped on the southern margin of the basin as far southward as the trace of the STDS. Where documented elsewhere in the Himalayan orogen, the youngest slip on the STDS predates the onset of sedimentation in Zhada basin (Cottle et al., 2007;
Hodges, 2000; Hodges et al., 1996; Hodges et al., 1992; Murphy and Yin, 2003; Murphy and Harrison, 1999; Searle et al., 1997; Searle et al., 2003; Yin, 2006). On the other hand, kinematic analyses of the Gurla Mandhata and Qusum detachments indicate that these faults accommodate arc-parallel extension and are actively exhuming mid-crustal 132 rocks from beneath the Zhada basin (Murphy et al., 2002; Zhang et al., 2000). Structural and isotopic analysis also indicates that the Gurla Mandhata detachment cuts the STDS, indicating that slip on the STDS had ceased prior to 9 Ma (Murphy, 2007; Murphy and
Copeland, 2005; Murphy et al., 2002).
133
SYNTHESIS
We divide the evolution of the Zhada basin into 5 stages (Figure 3.21). At ages >
9.2 Ma the Zhada basin was occupied by a large, northwestward flowing, braided river which had its headwaters in the Mt. Kailas region (Figure 3.21A). Exhumation of the
Leo Pargil/Qusum Range along a system of northeast striking detachment faults beginning at ~ 9.2 – 10 Ma decreased the fluvial gradient and caused ponding and upstream sediment accumulation. Before being completely defeated, the paleo-Sutlej
River cut and flowed through the valley identified above as a windgap (Figure 3.21B).
The combination of sill uplift and basin subsidence (owing to simultaneous footwall uplift and hanging wall subsidence during slip on the Qusum detachment) resulted in basin closure and lacustrine and alluvial fan sedimentation upstream of the dam between
~ 5.6 Ma and < 1 Ma. The Zhada basin became the sink for detritus derived from local highlands (Figure 3.21C). This situation continued until headward erosion breached a new sill at the current outlet in the southwestern corner of the basin at < 1 Ma (Figure
3.21D). Following breach of the sill the modern Sutlej River system began to re- equilibrate to the new base level resulting in upstream migration of a nickpoint and incision of the Zhada Formation (Figure 3.21E).
Arc-parallel extension is clearly accommodated by extension across the Leo
Pargil/Qusum Range and Gurla Mandhata, and dextral slip on the Karakoram fault
(Murphy et al., 2002; Thiede et al., 2006; Zhang et al., 2000). It is unclear which structures accommodate extension on the southwestern side of Zhada basin. No large- scale structure comparable to the Karakoram fault is present on this side of the basin. It 134 is possible that extension is taken up by distributed faulting directly south of the basin
(Figure 3.22). Another possibility is that slip on the Leo Pargil and Qusum detachments is transferred westward or northwestward, a process similar to that described by Murphy and Copeland (2005) for the Gurla Mandhata detachment (Figure 3.22).
The arc-parallel extension process provides a mechanism to explain the loss of elevation suggested by Saylor et al. (in press). They inferred a 0.8 - 1.5 km loss of elevation based on oxygen isotope paleoaltimetry. Assuming Airy isostacy, that loss of elevation would require between 4.5 and 8 km of crustal thinning. This could be achieved by two interacting detachment fault systems below the Zhada basin (Figure
3.22). Crustal thinning and the associated elevation loss also explain the anomalously low elevations in the Zhada region (Figure 3.2).
135
CONCLUSIONS
1) Zhada basin evolved from a northwestward-draining river valley to a broad depositional plain and finally to a largely closed basin. Closure of the basin resulted in lacustrine and lake-margin alluvial fan sedimentation until a new sill was breached in the southwest corner of the basin. The change in sedimentation style was accompanied by a change in sediment provenance, from a volcanic-rich source to the northeast in the Mt.
Kailas region, to more local metamorphic/clastic sources, mainly in the Tethyan and
Greater Himalayan sequence rocks.
2) Depositional environments included braided fluvial, marshy wetland, lacustrine, dune-field, sand-flat, lacustrine fan-delta, and alluvial fan systems.
Throughout Zhada basin history the climate was sufficiently arid to produce dune fields, evaporative marshes, evaporative sand flats, and bedded gypsum. These environmental conclusions are consistent with high δ18O values from lacustrine gastropods (Saylor et al., in press).
3) Zhada basin is the result of arc-parallel extension which was accommodated on crustal-scale detachment faults at the northwest and southeast extremities of the basin
(Figure 3.22). Sedimentation in the basin was due to a combination of sill uplift and tectonic subsidence which dammed a previously northwestward flowing river.
4) Excavation (vertical thinning and exhumation) of the mid-crust by detachment faulting likely provided the subsidence mechanism and resulted in the loss of elevation indicated by oxygen isotope studies in the basin and by the current, anomalously low elevation of the basin (Figure 3.2 and 3.22). 136
137
Figure 3.1. A: Elevation, shaded relief and generalized tectonic map of the Himalayan – Tibetan orogenic system showing the location of the Zhada Basin relative to several other normal fault bounded basins. Image from the UNAVCO Jules Verne Voyager and the Generic Mapping Tools (GMT). B: Generalized geologic map of the Zhada region. The location of measured sections presented in Figure 6 are indicated by solid black lines. Modified from published mapping by Chen and Xu (1987), Murphy and others (2000; 2002) and unpublished mapping by M. Murphy. 138
139
Figure 3.2. Topographic profile along an arc with a pole similar to that of Bendick and Bilham (2001) but with a shorter radius, such that it passes through the highest peaks of the Himalaya. The Zhada basin stands out as the largest region of low elevation in the Himalaya. 140
Figure 3.3. Geologic map of the Zhada region showing the traces of measured sections and the relationship between the Zhada Formation and basin-bounding faults. 141
142
Figure 3.4. The Zhada Formation is undeformed and lays in buttress unconformity with deformed Tethyan sequence strata. (A.) The unconformity relationship in the basin center. (B.) The unconformity relationship at the basin margins. (C.) Deformation in the central Zhada basin is limited to small-offset faults. The minor offset, lack of basement involvement and the fact that deformation is limited to a thin stratigraphic interval indicates that this deformation is related to syn-depositional slumping rather than significant tectonic activity. (D.) The geomorphic surface which caps the Zhada Formation 143
144
Figure 3.5. Correlation of the composite magnetostratigraphic section with the GPTS of Lourens et al. (2004). The composite magnetostratigraphic section was constructed from two magnetostratigraphic sections, each of which spanned the entire thickness of the Zhada Formation. The stratigraphic location of the C3 – C4 transition is indicated by the grey box (between 170 and 250 m in the South Zhada measured section. The location of the first Hipparion fossils is at ~ 240 m in the South Zhada measured section.
145
146
147
148
149
150
Figure 3.6. Measured sections, paleocurrent measurements, and clast compositions from the Zhada basin. See Figure 3.2 for locations. 151
Figure 3.7. (A.) Gravel foresets of lithofacies F1. Foresets are 3-4 m tall. (B.) Marshy wetland deposits of lithofacies F3. White flecks in the center of the picture are gastropod shells and shell fragments. (C.) Large-scale trough cross-stratification in F2 sandstones. (D.) F2 sandstones form laterally continuous, tabular deposits. (E.) Moderately sorted, imbricated pebble conglomerate of lithofacies F1 featuring scoured and filled channel 152 forms. Staff is 1.5 m long. (F.) Massive, organic-rich siltstone of lithofacies F3. (G.) F2 (now contorted) overlying marshy wetland deposits (F3). Staff is ~ 50 cm long. 153
Figure 3.8. (A.) Robust gastropod shell distinctive of lithofacies S1. (B.) Tabular deposits and channel forms in lithofacies S1. (C.) Horizontally stratified and planar, and gently climbing ripple cross-stratification of lithofacies S1. (D.) Dune foreset deposits of lithofacies S3. (E.) Mudball from lithofacies S2. 154
Figure 3.9. Laminated siltstone of lithofacies L1 featuring fossil grasses and fragmentary shell material. 155
Figure 3.10. (A.) Horizontally laminated claystone of lithofacies P1. (B.) Massive claystone of lithofacies P1. (C.) Upward-fining lamina of lithofacies P2 that are interpreted as turbidites. 156
157
Figure 3.11. (A.) High-concentration flood deposits or modified grain-flow deposits of lithofacies A1. (B.) Disorganize, matrix-supported boulder conglomerate of lithofacies A2 that is interpreted as cohesive debris flow deposits. (C.) Convoluted pebble conglomerate of lithofacies A4. (D.) Coarse progradational sequences at the top of the Zhada Formation. Visible in this image is an organic-poor example of lithofacies P1 and lithofacies A4 and A1. Abbreviations; TS: transgressive surface; P: progradation. 158
159
Figure 3.12. Stratigraphic cross-section across the Zhada basin showing the relationship between Zhada Formation members. Cross-section line is indicated in figure 3. Vertical exaggeration: 10X 160
Figure 3.13. Paleocurrent data for (A) the lower members of the Zhada Formation and (B) the upper members of the Zhada formation superimposed on topography. Paleocurrent data show an upsection evolution from uniformly northwestward directed to basin-centric directed paleocurrent indicators. Numbers in rose diagrams identify which measured section the data comes from (see Table S2). The outline of Zhada basin sediments is shown in A. For comparison, the modern drainage network is shown in B. 161
The modern Sutlej River rises in the region of Rakkas tal and Manasarovar (near Mt. Kailas) and exits the Zhada basin near the Leo Pargil Dome. 162
163
Figure 3.14. Photomicrographs of Zhada Formation sandstones. 164
165
Figure 3.15. QFL diagrams for samples from this study. Samples show an upsection trend from a arc-orogen dominated source to a recycled-orogen dominated source. The change in source terrane coincides with the reorientation of paleocurrent indicators (Fig. 13). Fields are from Dickinson (1985). 166
167
Figure 3.16. U/Pb concordia plots for detrital zircons samples from this study. Error ellipses are shown for 1-sigma level of uncertainty. See the text for a full discussion.
168
169
Figure 3.17. U/Pb relative age-probability density diagrams for detrital zircons from this study and possible source terranes for Zhada basin sediment. Samples are plotted stratigraphically upsection from bottom to top. Samples show an upsection change from a Kailas or Ayi Shan source to a local (Tethyan sequence) or southerly (Greater Himalyan sequence) source that is coincident with the reorientation of paleocurrent indicators (Fig. 13). Bin sizes for histograms associated with relative age-probability diagrams are 5 Myr for ages between 0 and 100 Ma and 50 Myr for ages between 100 Ma and 3500 Ma. Source region data from Gehrels et al. (2008). 170
171
Figure 3.18. A. Decompacted and tectonic subsidence curves for the Zhada basin. B. Tectonic subsidence curve for the Zhada basin compared to tectonic subsidence curves for a variety of tectonic settings (from Allen and Allen, 1990; Angevine et al., 1990). 172
173
Figure 3.19. Growth structure in Zhada Formation in the proximal hanging wall of the Qusum detachment fault. This is the only significant deformation observed in the Zhada basin. Telephone poles are 8 m tall. View is toward the northeast. The normal fault shown is antithetic to the top-to-the-east master Qusum detachment fault (not visible, to the west). See text for additional discussion of the growth-strata geometry. 174
175
Figure 3.20. (A.) LandSat image of the northwestern corner of the Zhada basin showing a windgap, possibly representing the course of the paleo-Sutlej River. Inset ―b‖ is enlarged in B. (B.) A view to the southeast from within the valley in (A). Note the relict surface that has been abandoned and incised by the modern river which occupies this valley. The cliff face indicated by ―a‖ is ~ 20 m tall. 176
177
Figure 3.21. Perspective diagram showing the interpreted basin evolution of the Zhada basin from a through-going river to a closed-basin lake before final breaching of a new sill resulting in integration of the modern Sutlej River. 178
179
Figure 3.22. Paleogeographic maps showing the influence of arc-parallel extension on the Sutlej River and Zhada basin. (A.) Prior to 9.2 Ma the paleo-Sutlej River drained regions north of the Indus suture and flowed to the northwest. (B.) With the onset of arc-parallel extension and exhumation of the Gurla Mandhata and Leo Pargil/Qusum core complexes the Sutlej River begins to pond, eventually forming the large Zhada paleo-lake. Arc- parallel extension is accommodated on the southwestern side of the basin either by distributed shortening, shown schematically at (a) or by transferring extension to the west or northwest (b). (C.) In the Pleistocene a new sill is breached in the west of the basin, resulting in the integration of the modern Sutlej River system. (D.) NW-SE cross-section showing the relationship between extension on the Qusum and Gurla Mandhata detachment faults and sedimentation in the Zhada and Pulan basins. The cross-section line is indicated in panel C. 180
Table 3.1. Lithofacies codes and interpretation.
Lithofacies Description Interpretation code Gcm Conglomerate, clast-supported, Deposition by traction currents poorly – moderately sorted, angular – modified by shear forces, sub-rounded, unstratified, poorly dispersive pressure or bouyancy organized
Gcmi Conglomerate, clast-supported, Deposition by traction currents poorly – moderately sorted, angular – sub-rounded, unstratified, imbricated
Gch Conglomerate, clast-supported, Deposition by traction currents in poorly – moderately sorted, angular – relative unconfined sheets sub-rounded, horizontally stratified
Gt Gravel – pebble conglomerate, clast- Deposition by traction currents in supported, moderately – well sorted, sub-aqueous, migrating, three- rounded - sub-rounded, trough cross- dimensional gravel – pebble stratified dunes
Gcf Pebble conglomerate, clast- Deposition by lateral or terminal supported, moderately sorted, sub- accretion on bars angular – sub-rounded, planar or epsilon cross-stratified
Gmm Conglomerate, matrix-supported, Deposition by cohesive mud- or poorly sorted, angular – sub- sand-matrix debris flows rounded, disorganized, unstratified
Gx Conglomerate, matrix- or clast- Deposition into a water saturated supported, poorly sorted, angular - environment; post-depositional sub-rounded, disorganized, dewatering due to sediment unstratified, with soft-sediment compaction or due to bioturbation deformation
St Medium – very coarse sandstone Deposition by migrating three- with trough cross-stratification dimensional sand dunes
Sp Very fine – medium sandstone with Deposition by migrating two- planar cross-stratification dimensional ripples
Sr Very fine – medium sandstone with Deposition under waning flow climbing ripple cross-stratification; conditions; interbedding with occasionally interbedded with mudstone indicates surging and mudstone waning flow conditions
Srw Very fine – medium sandstone with Deposition under oscillatory symmetrical ripple laminations current conditions
Sh Very fine – medium sandstone with Deposition under unidirectional 181
horizontal laminations upper-flow regime conditions
Sm Very fine – medium sandstone, Deposition under conditions of unstratified extremely rapid sediment accumulation; alternatively bioturbation may have destroyed sedimentary structures
Sf Very fine – fine sandstone with large Deposition on the foresets of planar foreset laminations migrating sub-aerial dunes.
Sc Very fine – very coarse sandstone Deposition into a water saturated with soft-sediment deformation, pre- environment; post-depositional existing sedimentary structures are dewatering due to sediment usually obliterated compaction or due to bioturbation
Mr Siltstone with climbing ripple cross- Deposition under waning flow stratification conditions
Ml Claystone – siltstone with horizontal Suspension settling in shallow laminations standing water; laminations are often the result of layers of plant material
Mh Claystone – siltstone with horizontal Suspension settling in deep stratification water
Mm Claystone – siltstone, unstratified Post-depositional bioturbation
Mc Claystone – siltstone with soft- Post-depositional dewatering due sediment deformation to sediment compaction or bioturbation
182
Table 3.2 Paleocurrent data
Table 2. Paleocurrent data presented in Figure 3.13 Lower Members (Fig. 13 A) Average flow Angular Largest Number direction Deviation N N frequency Section Name (Fig. 13) (deg.) (deg.) (measurements) (sites) (%) Qusum 1 291 3 23 2 100 1 Northwest Zhada 2 349 47 47 4 25 2 Northwest Zhada 3 270 43 36 3 67 3 Northwest Zhada 4 No data - - - - Namru road west 5 No data - - - - Namru road east 6 308 - 11 1 100 Guga 7 331 28 98 7 29 1 Noth Zhada 8 No data 2 North Zhada 9 No data - - - - 3 North Zhada 10 No data - - - - South Zhada 11 321 39 87 7 29 East Zhada 12 317 10 61 3 67 Southeast Zhada 13 292 13 53 3 33 Upper Members (Fig. 13 B) Qusum 1 No data - - - - 1 Northwest Zhada 2 No data - - - - 2 Northwest Zhada 3 No data - - - - 3 Northwest Zhada 4 92 40 30 3 33 Namru road west 5 241 42 42 4 25 Namru road east 6 No data - - - - Guga 7 268 37 55 4 25 1 Noth Zhada 8 8 51 30 3 33 2 North Zhada 9 234 27 30 3 33 3 North Zhada 10 22 14 20 2 50 South Zhada 11 38 20 98 6 50 East Zhada 12 188 - 15 1 100 Southeast Zhada 13 29 2 37 3 100
183
Table 3.3. Pointcount parameters.
Table 3. Modal petrographic point-count parameters Symbol Description Qm Monocrystaline quartz Qp Polycrystaline quartz Qpt Foliated polycrystalline quartz Qms Monocrystaline quartz grain within sandstone or quartzite lithic grain C Chert S Siltstone Qt Total Quartz (Qm+Qp+Qpt+Qms) K Potassium feldspar P Plagioclase feldspar F Total feldspar (P+K) Lvm Mafic volcanic grains Lvf Felsic volcanic grains Lvv Vitric volcanic grains Lvl Lathwork volcanic grains Lv Total volcanic grains(Lvm+Lvf+Lvv+Lvx+Lvl) Lsh Mudstone/shale Lph Phyllite Lsm Schist Lc Carbonate Ls Total sedimentary/low grade metasedimentary lithic grains (Lsh+Lc+C+S+Qms+Lph) Lt Total lithic grains (Lv+Ls+Qp+Qpt) L Total non-quartzose lithic grains (Lv+Ls+Lc) Qx Total polycrystalline quartz (Qp+Qpt) Accessory minerals include zircon, muscovite, biotite, garnet, serpentine, chlorite, tourmaline, cordierite, and olivine.
184
Table 3.4 Recalculated petrographic pointcount data
Table 4. Recalculated modal petrographic data SAMPLE %Qt %F %L %Q %F %Lt %Q %Lv %Ls %Q %P %K 1EZ3.25 50.9 11.4 37.6 33.4m 11.4 55.1 18.3p 29.8 51.8 74.5m 17.9 7.46 1EZ29 55.38 11.72 32.90 41.86 11.72 46.42 24.45 37.26 38.30 78.16 10.48 11.4 2EZ26A 46.16 16.53 37.31 31.54 16.53 51.93 18.54 28.22 53.23 65.60 21.38 12.93 2EZ66.5 43.37 13.21 43.32 32.68 13.21 54.01 17.22 33.04 49.64 71.17 14.89 13.94 2EZ117. 69.59 13.13 17.39 48.98 13.13 37.99 51.57 7.559 40.84 78.89 11.73 9.438 43EZ1.5 50.86 12.71 36.33 32.65 12.71 54.64 28.37 27.6 44.08 71.87 15.50 12.5 3EZ152 69.08 12.07 18.95 55.51 12.07 32.32 37.96 4.384 57.60 82.16 12.58 5.245 3EZ180. 58.73 9.026 32.21 40.16 9.026 50.89 31.66 8.40 59.96 81.67 9.779 8.59 84EZ24 66.93 12.6 20.45 47.42 12.6 39.96 39.38 3.79 56.82 78.94 7.64 13.3 5EZ47.5 73.12 10.62 16.26 56.12 10.62 33.26 52.84 1.60 45.67 84.08 13.9 1.998 1NZ3 68.94 22.94 8.132 52.22 22.94 24.84 63.00 6.00 31.00 69.56 26.24 4.26 1NZ16 53.17 37.71 9.11 45.52 37.71 16.68 43.00 5.81 51.10 54.61 24.43 20.9 1NZ35.5 42.30 55.19 2.55 35.44 55.19 9.447 64.82 8.11 27.06 39.15 36.62 24.23 2NZ29.5 53.65 37.60 8.65 46.76 37.60 15.5 46.96 4.94 48.13 55.35 36.22 8.433 3NZ20 62.05 24.59 13.3 40.43 24.59 35.08 57.81 2.81 39.35 62.25 22.92 14.8 1LC1 34.69 17.96 47.45 28.43 17.96 53.71 13.37 52.3 34.33 61.30 12.32 26.28 1LC24 37.51 13.40 49.09 30.50 13.40 56.00 13.79 47.10 39.01 69.44 19.17 11.49 1LC58.1 38.50 19.56 41.94 26.73 19.56 53.61 23.09 31.53 45.48 57.70 23.13 19.18 50SZ1 57.80 11.99 30.11 30.75 11.99 57.36 45.63 38.55 15.73 71.92 22.36 5.702 0.1SZ13. 63.07 12.09 24.95 39.51 12.09 48.40 61.84 3.729 34.47 76.63 10.37 13.0 60.1SZ28 56.84 15.16 28.00 30.53 15.16 54.22 66.96 7.55 25.42 66.83 18.54 14.63 0.2SZ30 65.21 9.327 25.42 50.69 9.327 40.04 23.08 18.0 59.07 84.45 6.804 8.741 0.3SZ52. 56.84 15.3 27.74 23.48 15.3 61.10 60.90 1.120 37.90 60.47 32.5 6.98 82SZ42.5 55.38 17.55 27.17 35.78 17.55 46.67 57.97 3.10 38.92 67.17 17.36 15.5 3SZ36.2 56.95 17.43 25.62 44.19 17.43 38.48 41.56 14.3 44.14 71.73 13.30 14.97 4SZ14 54.68 17.50 27.72 42.17 17.50 40.23 44.24 6.256 49.50 70.54 29.05 0.391 4SZ27 62.43 15.89 21.78 39.63 15.89 44.58 49.03 2.17 48.72 71.44 14.67 13.9 5SZ8.4 63.75 13.42 22.83 45.21 13.42 41.37 51.67 0.72 47.66 77.06 10.74 12.10 1NWZ37 52.13 8.175 39.63 25.74 8.175 66.12 56.91 20.1 22.97 75.89 16.44 7.657 .41NWZ96 47.59 6.25 46.24 23.10 6.25 70.64 38.87 8.432 52.71 78.78 14.17 7.09 2NWZ2. 47.40 43.1 9.415 34.73 43.1 22.13 61.96 15.2 22.81 44.52 26.78 28.7 52NWZ58 68.05 13.04 18.8 37.41 13.04 49.56 69.50 12.34 18.16 74.18 11.90 13.92 .23NWZ45 54.59 2.797 42.64 14.24 2.797 82.90 86.92 0.000 13.08 83.53 14.94 1.493 .93NWZ77 64.87 17.2 17.84 26.31 17.2 56.49 96.62 0.00 3.398 60.48 26.63 12.9 9 4 7 3 4 3 1 3 2 5
185
Table 3.5. Detrital zircon U-Pb data table.
T a b l e S5. U - Pb ( z i r c o n ) geochronologic a n a l y s e s by L a s e r - A b l a t i o n Multicollector ICP M a s s Isotopic Spectrometery ratios Apparent ages (Ma)
Analysis U 206Pb U/Th 207Pb* ± 206Pb* ± error206Pb* ± 207Pb*± 206Pb* ± Best ±
(ppm) 204Pb 235U (%) 238U (%) corr.238U (Ma) 235U (Ma) 207Pb* (Ma) (Ma)age (Ma)
2EZ881-1 330 17766 1.6 0.61063 4.7 0.077243.7 0.79 479.6 17.2 484.0 18.2 504.4 64.3 479.6 17.2 2EZ881-2 377 12680 1.5 1.26719 6.3 0.133976.2 0.98 810.5 47.0 831.1 35.7 886.7 25.3 886.7 25.3 2EZ881-3 198 3744 1.4 0.66263 10.9 0.076862.0 0.18 477.4 9.2 516.2 44.2 692.1 229.7 477.4 9.2 2EZ881-4 416 2156 5.0 0.76704 15.8 0.0798415.6 0.99 495.2 74.3 578.1 69.6 918.8 47.9 918.8 47.9 2EZ881-5 1020 54545 1.5 0.60280 6.8 0.079306.6 0.97 491.9 31.1 479.0 25.9 417.5 37.8 491.9 31.1 2EZ881-6 531 58630 1.8 2.78532 6.7 0.221296.5 0.98 1288.7 76.1 1351.6 49.8 1452.6 26.3 1452.6 26.3 2EZ881-7 255 43013 1.5 4.16810 3.7 0.286973.0 0.80 1626.4 42.9 1667.8 30.6 1720.2 41.4 1720.2 41.4 2EZ881-8 1927 280928 8.2 8.07293 4.1 0.380713.7 0.90 2079.6 65.6 2239.2 37.2 2388.5 31.0 2388.5 31.0 2EZ881-9 868 7178 2.0 0.81214 13.7 0.076028.4 0.62 472.3 38.4 603.7 62.2 1133.7 214.7 1133.7 214. 2EZ881-10 610 1268 1.5 0.02241 12.5 0.003214.5 0.36 20.7 0.9 22.5 2.8 220.7 270.0 20.7 0.97 2EZ881-12 759 2124 1.2 0.02298 7.2 0.003293.2 0.45 21.2 0.7 23.1 1.6 224.6 148.9 21.2 0.7 2EZ881-13 195 1916 0.8 0.05223 11.3 0.007403.8 0.34 47.5 1.8 51.7 5.7 249.5 245.4 47.5 1.8 2EZ881-14 649 68623 2.7 1.12754 3.7 0.120633.4 0.93 734.2 23.8 766.6 19.8 862.1 27.4 862.1 27.4 2ez882-1 513 13539 1.2 1.27879 16.2 0.1290916.0 0.99 782.7 118.1 836.3 92.4 981.6 44.7 981.6 44.7 2ez882-2 165 1196 0.9 0.07837 32.4 0.009968.6 0.27 63.9 5.5 76.6 23.9 495.1 703.7 63.9 5.5 2ez882-3 1183 81711 1.2 10.145553.4 0.437602.8 0.82 2339.9 54.5 2448.1 31.4 2539.3 32.7 2539.3 32.7 2ez882-4 464 2320 0.9 0.05665 9.7 0.007714.8 0.49 49.5 2.4 56.0 5.3 340.3 191.5 49.5 2.4 2ez882-5 582 2085 0.7 0.05781 13.9 0.007745.7 0.41 49.7 2.8 57.1 7.7 377.5 287.2 49.7 2.8 2ez882-6 175 9882 0.6 1.67426 4.2 0.168232.7 0.64 1002.3 24.9 998.8 26.6 991.1 65.2 991.1 65.2 2ez882-7 355 14960 1.6 0.51027 3.1 0.067372.6 0.84 420.3 10.6 418.6 10.7 409.6 37.9 420.3 10.6 2ez882-8 653 4411 0.8 0.05628 7.6 0.007483.2 0.41 48.1 1.5 55.6 4.1 393.8 155.9 48.1 1.5 2ez882-9 2062 2843 1.8 0.01790 8.3 0.002664.7 0.56 17.1 0.8 18.0 1.5 135.4 162.4 17.1 0.8 2ez882-10 370 51539 1.6 1.51792 2.4 0.156941.3 0.57 939.7 11.7 937.6 14.4 932.7 39.6 932.7 39.6 2ez882-11 979 5193 0.8 0.05925 5.6 0.008922.3 0.42 57.3 1.3 58.5 3.2 107.7 120.9 57.3 1.3 2ez882-12 401 12300 0.9 0.60937 4.6 0.077282.0 0.44 479.8 9.3 483.2 17.8 498.9 92.0 479.8 9.3 2ez882-13 347 24726 3.7 1.54427 3.6 0.154922.5 0.69 928.5 21.6 948.2 22.3 994.2 53.2 994.2 53.2 2ez882-14 573 39281 1.6 7.14936 5.7 0.375832.9 0.51 2056.8 51.5 2130.2 50.8 2201.8 85.0 2201.8 85.0 2ez882-15 289 1882 0.8 0.05348 13.2 0.007405.7 0.44 47.6 2.7 52.9 6.8 302.0 270.9 47.6 2.7 2ez882-16 396 2067 0.6 0.05839 8.9 0.007463.3 0.37 47.9 1.6 57.6 5.0 482.0 183.7 47.9 1.6 2ez882-17 82 33432 1.1 12.695811.7 0.495961.1 0.67 2596.4 24.1 2657.3 15.8 2704.1 20.5 2704.1 20.5 2ez882-18 394 4159 1.2 0.06370 11.1 0.008755.3 0.48 56.2 3.0 62.7 6.7 319.8 221.6 56.2 3.0 2ez882-19 266 2435 0.8 0.05197 15.2 0.007485.2 0.34 48.0 2.5 51.4 7.6 213.7 332.7 48.0 2.5 2ez882-20 248 2073 0.6 0.10033 19.1 0.011554.6 0.24 74.1 3.4 97.1 17.7 707.5 397.2 74.1 3.4 2ez882-21 301 2410 0.7 0.04999 14.2 0.007504.7 0.33 48.2 2.2 49.5 6.9 116.6 317.7 48.2 2.2 2ez882-22 119 7562 0.4 0.68718 4.4 0.081052.1 0.49 502.4 10.4 531.1 18.2 656.4 82.1 502.4 10.4 2ez882-23 243 94967 1.3 10.815582.3 0.465311.2 0.51 2463.0 24.0 2507.4 21.5 2543.6 33.4 2543.6 33.4 2ez882-25 381 44590 1.4 1.69005 3.0 0.166641.6 0.53 993.5 14.9 1004.8 19.4 1029.3 52.2 1029.3 52.2 2ez882-26 623 5642 0.8 0.05053 7.9 0.007313.3 0.42 47.0 1.6 50.1 3.9 201.2 166.1 47.0 1.6 2ez882-27 779 3608 0.5 0.05301 8.2 0.007516.4 0.78 48.2 3.1 52.4 4.2 249.0 118.0 48.2 3.1 2ez882-28 148 4555 0.8 1.67951 6.1 0.155284.8 0.79 930.5 41.9 1000.8 39.1 1158.1 75.3 1158.1 75.3 2ez882-30 306 31046 1.6 2.19280 8.2 0.199707.9 0.97 1173.7 85.1 1178.8 57.3 1188.0 41.5 1188.0 41.5 2ez882-29 602 82602 20.8 2.60620 3.7 0.216613.2 0.87 1263.9 37.2 1302.4 27.5 1366.3 36.0 1366.3 36.0 2ez882-31 223 26955 1.0 1.63548 4.3 0.164073.9 0.91 979.3 35.3 984.0 26.9 994.3 35.7 994.3 35.7 186
2ez882-32 2490 4583 2.8 0.47646 8.9 0.053454.8 0.54 335.7 15.6 395.6 29.3 763.0 159.3 335.7 15.6 2ez882-33 638 1620 1.3 0.06511 11.2 0.008556.3 0.56 54.9 3.4 64.0 7.0 422.1 207.8 54.9 3.4 2ez882-34 317 1344 0.8 0.05730 26.5 0.007855.6 0.21 50.4 2.8 56.6 14.6 324.8 596.9 50.4 2.8 2ez882-35 518 141931 0.8 5.29898 2.2 0.337781.8 0.83 1876.0 29.5 1868.7 18.6 1860.6 21.7 1860.6 21.7 2ez882-36 724 19423 1.4 0.61664 4.0 0.077293.0 0.77 479.9 14.1 487.7 15.3 524.6 55.5 479.9 14.1 2ez882-37 384 44586 3.7 2.04600 3.1 0.191951.9 0.61 1131.9 20.0 1131.0 21.5 1129.1 49.6 1129.1 49.6 2ez882-38 545 1997 0.9 0.05244 6.1 0.007763.8 0.61 49.8 1.9 51.9 3.1 148.8 114.0 49.8 1.9 2ez882-39 119 2964 0.5 0.71327 5.9 0.081302.4 0.40 503.9 11.5 546.7 25.0 729.2 114.8 729.2 114. 2ez882-40 273 30843 1.3 1.55290 2.6 0.156322.2 0.86 936.3 19.4 951.6 15.9 987.3 26.5 987.3 26.58 2EZ607A1-2 605 4384 1.1 0.06000 3.2 0.008471.1 0.34 54.3 0.6 59.2 1.9 259.0 69.6 54.3 0.6 2EZ607A1-3 243 1206 0.7 0.04517 11.7 0.007481.9 0.16 48.1 0.9 44.9 5.1 -123.0 285.5 48.1 0.9 2EZ607A1-4 540 27415 1.4 0.57079 2.1 0.072601.6 0.74 451.8 6.9 458.5 7.9 492.2 32.0 492.2 32.0 2EZ607A1-5 605 3062 0.7 0.05011 6.5 0.007314.5 0.68 46.9 2.1 49.7 3.2 183.4 111.5 46.9 2.1 2EZ607A1-7 805 2808 1.3 0.39078 12.5 0.0445212.3 0.98 280.8 33.8 334.9 35.7 730.5 47.6 730.5 47.6 2EZ607A1-8 313 2889 1.9 0.08715 5.5 0.013663.0 0.55 87.5 2.6 84.8 4.5 12.0 111.5 87.5 2.6 2EZ607A1-9 402 2131 1.1 0.05288 6.1 0.008342.5 0.41 53.5 1.3 52.3 3.1 -2.0 135.4 53.5 1.3 2EZ607A1-10 149 12394 6.3 1.59636 7.9 0.144527.3 0.93 870.2 59.6 968.8 49.2 1199.8 57.5 1199.8 57.5 2EZ607A1-11 315 330 0.7 0.03367 22.4 0.003116.0 0.27 20.0 1.2 33.6 7.4 1160.1 432.8 1160.1 432. 2EZ607A1-12 538 1159 0.7 0.02200 13.1 0.003199.6 0.73 20.5 2.0 22.1 2.9 195.2 206.7 20.5 2.08 2ez607A2-2 851 2719 1.2 0.07140 6.8 0.008841.3 0.18 56.7 0.7 70.0 4.6 552.2 145.2 552.2 145. 2ez607A2-4 376 14553 1.3 0.62895 2.4 0.079131.0 0.42 490.9 4.8 495.4 9.4 516.3 47.6 516.3 47.62 2ez607A2-5 277 20597 1.3 1.61894 1.7 0.164711.2 0.69 982.9 10.9 977.6 10.8 965.6 25.4 965.6 25.4 2ez607A2-7 189 16593 0.8 3.56647 6.6 0.258156.5 0.98 1480.4 85.9 1542.1 52.6 1627.7 24.0 1627.7 24.0 2ez607A2-9 586 1216 0.9 0.06756 8.1 0.008184.0 0.50 52.5 2.1 66.4 5.2 601.1 151.8 601.1 151. 2ez607A2-10 217 38622 1.4 3.90991 2.1 0.284781.4 0.68 1615.4 20.6 1615.7 17.1 1616.1 28.9 1616.1 28.98 2ez607A2-11 290 2159 0.5 0.06735 13.3 0.008805.6 0.42 56.5 3.1 66.2 8.5 432.6 269.2 56.5 3.1 2ez607A2-12 436 1789 0.7 0.06012 23.4 0.007677.3 0.31 49.3 3.6 59.3 13.5 484.4 495.7 49.3 3.6 2ez607A2-15 1187 925 0.4 0.07935 17.3 0.007388.4 0.49 47.4 4.0 77.5 12.9 1147.0 301.3 1147.0 301. 2ez607A2-16 190 38862 1.4 2.09102 1.6 0.192281.0 0.63 1133.7 10.7 1145.9 11.2 1168.9 25.2 1168.9 25.23 2ez607A2-18 565 25216 2.3 0.60786 9.0 0.072438.6 0.96 450.8 37.6 482.2 34.7 634.6 56.6 634.6 56.6 2ez607A2-19 203 1069 0.6 0.09759 14.0 0.012186.1 0.43 78.1 4.7 94.5 12.6 533.1 276.6 533.1 276. 2EZ665-1 186 25795 1.8 2.67730 4.0 0.221991.4 0.35 1292.4 16.3 1322.2 29.6 1370.9 72.2 1370.9 72.26 2EZ665-2 247 18644 0.7 1.53859 3.4 0.158722.4 0.70 949.7 21.2 945.9 21.2 937.3 50.5 937.3 50.5 2EZ665-3 238 1712 0.7 0.02437 21.0 0.008056.9 0.33 51.7 3.6 24.4 5.1 -2244.8797.7 51.7 3.6 2EZ665-4 884 6696 2.1 0.06380 5.2 0.009703.1 0.61 62.2 1.9 62.8 3.1 85.4 97.3 62.2 1.9 2EZ665-5 247 1893 1.0 0.08595 10.9 0.012364.7 0.43 79.2 3.7 83.7 8.7 214.0 227.4 79.2 3.7 2EZ665-6 295 1522 0.8 0.10756 10.7 0.014602.1 0.19 93.4 1.9 103.7 10.5 347.3 237.7 93.4 1.9 2EZ665-7 518 54914 2.9 2.00685 3.2 0.175902.8 0.87 1044.6 26.6 1117.8 21.6 1263.2 31.3 1263.2 31.3 2EZ665-8 857 5602 1.0 0.05345 6.7 0.007673.5 0.52 49.2 1.7 52.9 3.5 220.7 132.6 49.2 1.7 2EZ665-9 167 1056 1.1 0.02999 19.0 0.007836.1 0.32 50.3 3.1 30.0 5.6 -1402.5588.1 50.3 3.1 2EZ665-11 661 2831 1.8 0.06275 5.2 0.008972.5 0.49 57.6 1.5 61.8 3.1 229.4 103.9 57.6 1.5 2EZ665-12 237 51392 2.3 11.190924.1 0.467793.3 0.80 2473.8 68.0 2539.2 38.4 2591.7 40.9 2591.7 40.9 2EZ665-13 1402 25081 1.3 1.17057 2.6 0.128311.4 0.55 778.2 10.3 786.9 14.0 811.6 44.7 811.6 44.7 2EZ665-15 561 33567 2.8 10.737964.0 0.437573.3 0.83 2339.8 64.2 2500.7 36.7 2634.1 36.9 2634.1 36.9 2EZ665-16 546 2115 1.5 0.05634 11.9 0.008862.6 0.22 56.8 1.5 55.7 6.4 5.2 280.0 56.8 1.5 2EZ665-17 873 807 1.3 0.07815 8.6 0.009083.4 0.40 58.2 2.0 76.4 6.3 689.6 169.0 58.2 2.0 2EZ665-19 690 1301 2.5 0.07460 19.7 0.010266.5 0.33 65.8 4.3 73.1 13.9 318.2 424.6 65.8 4.3 2EZ665-20 148 797 0.9 0.04605 33.5 0.011244.5 0.13 72.1 3.2 45.7 15.0 -1188.81049.4 72.1 3.2 2EZ665-21 460 2630 0.9 0.05128 8.3 0.007603.6 0.43 48.8 1.7 50.8 4.1 143.5 175.3 48.8 1.7 2EZ665-22 390 17994 1.7 1.81819 2.2 0.175581.0 0.47 1042.8 10.1 1052.0 14.6 1071.3 39.5 1071.3 39.5 2EZ665-23 296 700 0.7 0.03247 15.4 0.006694.2 0.28 43.0 1.8 32.4 4.9 -691.4 411.3 43.0 1.8 2EZ665-24 1519 1433 1.9 0.02796 13.9 0.003726.2 0.45 24.0 1.5 28.0 3.8 389.4 280.3 24.0 1.5 2EZ665-25 392 955 1.0 0.05556 33.1 0.008305.9 0.18 53.3 3.1 54.9 17.7 126.6 785.7 53.3 3.1 187
2EZ665-27 265 2486 1.1 0.08948 8.7 0.014262.1 0.25 91.3 1.9 87.0 7.2 -28.7 203.5 91.3 1.9 2EZ665-28 2467 160343 37.5 5.52247 17.5 0.2856316.6 0.95 1619.6 237.5 1904.1 151.2 2230.0 95.1 2230.0 95.1 2EZ665-29 1117 8189 2.5 0.06121 2.7 0.009201.8 0.67 59.1 1.1 60.3 1.6 110.7 48.0 59.1 1.1 2EZ665-30 252 6802 1.4 1.68072 1.8 0.165601.4 0.78 987.8 13.0 1001.3 11.6 1030.7 23.1 1030.7 23.1 2EZ665-31 194 702 1.7 0.05957 11.9 0.009334.1 0.35 59.8 2.5 58.8 6.8 14.5 269.1 59.8 2.5 2EZ665-32 158 8994 1.9 1.41621 3.8 0.147123.0 0.80 884.8 25.2 895.8 22.7 922.9 47.2 922.9 47.2 2EZ665-33 2308 9687 1.5 0.04973 4.9 0.007612.6 0.52 48.9 1.2 49.3 2.4 68.8 100.1 48.9 1.2 2EZ665-34 375 2975 0.5 0.10760 6.5 0.016682.7 0.41 106.6 2.8 103.8 6.4 38.6 142.7 106.6 2.8 2EZ665-35 469 34549 6.1 1.32877 7.9 0.138647.5 0.96 837.0 59.2 858.3 45.6 914.0 45.8 914.0 45.8 2EZ665-36 716 149677 3.7 29.927056.0 0.724405.0 0.82 3512.5 134.5 3484.4 59.5 3468.3 53.5 3468.3 53.5 2EZ665-37 662 25792 3.7 1.38776 5.0 0.147433.6 0.71 886.5 29.5 883.7 29.6 876.8 73.2 876.8 73.2 2EZ665-38 310 4401 1.0 0.61289 5.4 0.077963.1 0.58 483.9 14.6 485.4 20.6 492.2 95.8 483.9 14.6 2EZ665-39 1955 2664 2.3 0.05307 9.3 0.006863.7 0.40 44.1 1.6 52.5 4.8 456.6 189.2 44.1 1.6 2EZ665-40 525 2562 1.4 0.06013 14.8 0.0089010.8 0.73 57.1 6.1 59.3 8.5 148.1 238.5 57.1 6.1 2EZ665-41 439 2268 1.6 0.05926 7.2 0.009524.2 0.58 61.1 2.6 58.5 4.1 -46.8 143.7 61.1 2.6 2EZ665-42 667 52648 0.9 9.66538 5.3 0.424505.0 0.95 2280.9 96.6 2403.4 48.9 2508.9 28.8 2508.9 28.8 2EZ665-43 1468 8892 2.7 1.17399 6.4 0.120995.6 0.88 736.3 39.1 788.5 34.9 939.2 61.4 939.2 61.4 2EZ665-44 334 17846 2.0 1.92471 3.4 0.184112.0 0.59 1089.4 19.8 1089.7 22.5 1090.3 54.5 1090.3 54.5 2EZ665-45 543 12046 2.1 0.66143 3.2 0.080922.5 0.77 501.6 11.9 515.5 12.9 577.5 44.2 501.6 11.9 2EZ665-46 294 1518 1.0 0.07300 8.0 0.012162.9 0.37 77.9 2.3 71.5 5.5 -136.4 183.8 77.9 2.3 2EZ665-47 866 30043 2.4 10.729264.1 0.445613.1 0.76 2375.7 62.0 2500.0 38.4 2602.5 45.0 2602.5 45.0 2EZ665-48 398 29052 0.8 1.88865 3.8 0.180583.4 0.89 1070.2 33.7 1077.1 25.5 1091.2 34.7 1091.2 34.7 2EZ665-49 2512 8012 2.2 0.04531 2.3 0.007501.7 0.74 48.2 0.8 45.0 1.0 -120.7 38.1 48.2 0.8 2EZ665-50 255 1665 1.2 0.68162 3.6 0.080361.4 0.38 498.3 6.6 527.8 15.0 657.4 72.5 498.3 6.6 2EZ665-51 195 6169 1.2 0.68666 2.5 0.087981.6 0.62 543.6 8.1 530.8 10.4 476.1 44.0 543.6 8.1 2EZ665-53 565 1339 1.6 0.12695 40.3 0.015388.5 0.21 98.4 8.3 121.4 46.1 598.7 885.3 98.4 8.3 2EZ665-55 1300 3089 1.1 0.05830 6.5 0.008182.9 0.44 52.5 1.5 57.5 3.7 271.5 134.3 52.5 1.5 2EZ665-56 1309 3044 1.5 0.02078 8.6 0.003413.5 0.41 22.0 0.8 20.9 1.8 -102.5 193.3 22.0 0.8 2EZ665-57 502 29171 0.4 2.34005 7.0 0.199646.4 0.92 1173.4 68.7 1224.5 49.7 1315.8 54.0 1315.8 54.0 2EZ665-58 1290 34071 2.9 0.92020 3.6 0.106231.2 0.33 650.8 7.3 662.5 17.6 702.3 72.8 650.8 7.3 2EZ665-59 223 4652 2.7 0.69681 4.3 0.085452.2 0.50 528.6 11.0 536.9 18.0 572.3 81.2 528.6 11.0 2EZ665-60 2066 46953 1.5 0.62816 3.1 0.080432.0 0.65 498.7 9.6 494.9 12.0 477.8 51.1 498.7 9.6 2EZ665-61 349 3042 1.7 0.09541 4.7 0.015022.4 0.50 96.1 2.2 92.5 4.2 1.3 98.5 96.1 2.2 2EZ665-62 1503 1690 2.5 0.01730 8.6 0.002844.6 0.54 18.3 0.8 17.4 1.5 -103.5 179.7 18.3 0.8 2EZ665-63 1128 674 0.9 0.06170 18.8 0.007405.4 0.29 47.6 2.6 60.8 11.1 619.2 392.3 47.6 2.6 2EZ665-64 434 1009 2.0 0.06531 8.8 0.008852.9 0.33 56.8 1.6 64.2 5.5 351.5 187.6 56.8 1.6 2EZ665-65 309 29875 5.0 1.46055 1.8 0.152181.1 0.59 913.2 9.0 914.2 10.8 916.7 30.0 916.7 30.0 2EZ665-66 578 4185 1.0 0.06052 4.5 0.008763.1 0.69 56.2 1.7 59.7 2.6 198.9 75.5 56.2 1.7 2EZ665-67 676 16450 3.1 0.72437 6.6 0.085454.7 0.70 528.6 23.6 553.2 28.2 656.1 100.6 528.6 23.6 2EZ665-68 305 18833 8.0 0.85210 2.0 0.101491.6 0.82 623.1 9.5 625.8 9.1 635.4 24.1 623.1 9.5 2EZ665-69 166 82521 1.4 11.410633.2 0.464463.0 0.95 2459.2 61.5 2557.3 29.6 2636.0 16.6 2636.0 16.6 2EZ665-70 350 915 0.9 0.05610 22.2 0.007513.8 0.17 48.2 1.8 55.4 12.0 378.3 497.6 48.2 1.8 2EZ665-71 1360 3235 1.8 0.78869 6.5 0.083805.5 0.85 518.8 27.2 590.4 28.9 876.4 71.0 518.8 27.2 2EZ665-72 152 45494 2.0 4.66693 2.2 0.311461.7 0.77 1747.9 25.3 1761.3 18.0 1777.3 25.2 1777.3 25.2 2EZ665-73 281 75813 3.0 1.67555 2.4 0.166581.6 0.67 993.2 14.6 999.3 15.0 1012.6 35.5 1012.6 35.5 2EZ665-74 511 87397 3.8 11.151903.3 0.443582.9 0.87 2366.6 57.7 2535.9 31.2 2674.2 27.3 2674.2 27.3 2EZ665-75 205 19194 1.9 6.17826 2.0 0.298501.5 0.78 1683.9 22.7 2001.4 17.2 2347.2 21.1 2347.2 21.1 2EZ665-76 241 14410 1.8 0.84946 1.9 0.102661.0 0.54 630.0 6.0 624.4 8.7 603.9 34.0 630.0 6.0 2EZ665-77 376 10755 1.0 1.33954 3.4 0.141012.8 0.82 850.4 22.1 863.0 19.7 895.7 40.1 895.7 40.1 2EZ665-78 619 46379 2.6 2.04809 16.2 0.1740015.9 0.98 1034.1 152.3 1131.7 110.9 1324.0 55.2 1324.0 55.2 2EZ665-79 98 746 1.2 0.02585 42.7 0.008804.6 0.11 56.5 2.6 25.9 10.9 -2365.01809.8 56 .5 2.6 2EZ665-80 4889 9198 66.3 0.07206 12.0 0.0099911.8 0.99 64.1 7.5 70.7 8.2 298.4 43.5 64.1 7.5 2EZ665-81 201 13598 1.0 1.53759 1.8 0.157451.0 0.56 942.6 8.8 945.5 11.0 952.4 30.3 952.4 30.3 188
2EZ665-83 552 13772 1.9 13.923506.3 0.458035.8 0.92 2430.8 118.3 2744.5 60.0 2984.1 39.3 2984.1 39.3 2EZ665-84 190 17058 0.7 1.97749 2.9 0.188361.0 0.35 1112.5 10.2 1107.9 19.4 1098.7 54.1 1098.7 54.1 2EZ665-85 384 59607 1.8 4.88673 2.2 0.321461.4 0.64 1796.9 22.0 1800.0 18.4 1803.5 30.4 1803.5 30.4 2EZ665-86 362 21764 1.1 3.25697 3.8 0.247113.3 0.86 1423.6 42.0 1470.8 29.7 1539.8 36.8 1539.8 36.8 2EZ665-87 241 2885 1.4 0.07518 6.7 0.013963.0 0.44 89.4 2.6 73.6 4.8 -412.8 157.5 89.4 2.6 2EZ665-88 541 3913 3.4 8.02088 3.7 0.346252.0 0.53 1916.7 32.6 2233.4 33.4 2537.9 52.5 2537.9 52.5 2EZ665-89 2244 2954 1.7 0.01696 4.3 0.002622.9 0.68 16.8 0.5 17.1 0.7 50.2 75.4 16.8 0.5 2EZ665-90 630 5532 1.4 0.06183 5.3 0.009672.5 0.48 62.0 1.6 60.9 3.1 17.3 111.4 62.0 1.6 2EZ665-92 183 1754 0.8 0.54342 10.0 0.068829.0 0.90 429.1 37.2 440.7 35.7 501.8 96.8 429.1 37.2 2EZ665-93 532 10765 0.7 4.04459 4.3 0.285853.8 0.88 1620.7 54.2 1643.2 34.9 1672.1 37.4 1672.1 37.4 2EZ665-94 1070 122060 3.2 1.46260 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88.8 6.8 54.8 183.4 90.1 1.9 4SZ14-1 261 3522 1.0 0.6012 3.4 0.0764 1.9 0.5 474.7 8.8 478.0 13.1 493.9 62.6 474.7 8.8 4SZ14-2 645 17245 2.1 1.8606 2.0 0.1792 1.0 0.56 1062. 9.8 1067. 13.3 1076. 35.0 1062.9 9.8 4SZ14-3 195 9624 1.2 4.2553 1.9 0.2970 1.1 0.50 1676.9 16.4 1684.2 15.4 1694.0 27.7 1676.6 16.4 4SZ14-4 92 2888 1.6 1.7303 2.4 0.1710 1.5 0.69 1017.6 14.5 1019.8 15.4 1025.9 37.2 1017.4 14.5 4SZ14-5 3583 10682 6.2 3.7433 1.4 0.2776 1.0 0.74 1579.4 14.0 1580.9 11.3 1582.0 18.7 1579.1 14.0 4SZ14-6 887 137726 3.0 0.6852 33. 0.0775 1.2 0.01 481.41 5.6 529.97 137. 744.59 716. 481.4 5.6 4SZ14-7 478 2286 0.4 0.5849 19.0 0.0603 7.4 0.34 377.2 27.0 467.6 72.12 940.0 366.3 377.2 27.0 4SZ14-8 162 5035 1.5 1.6017 1.72 0.1616 1.0 0.58 965.5 9.0 970.9 10.7 982.9 28.23 965.5 9.0 4SZ14-9 321 5786 2.6 0.6892 7.0 0.0836 6.7 0.99 517.8 33.5 532.3 29.1 594.9 43.1 517.8 33.5 4SZ14-10 546 4350 0.9 0.6147 5.3 0.0763 1.4 0.26 473.9 6.3 486.5 20.3 546.6 110. 473.9 6.3 4SZ14-11 1037 17073 4.2 0.6842 2.0 0.0830 1.0 0.56 513.7 4.9 529.3 8.1 597.0 36.49 513.7 4.9 4SZ14-12 231 4420 1.8 0.6278 4.0 0.0778 1.0 0.21 483.1 4.7 494.7 15.5 548.6 83.8 483.1 4.7 4SZ14-13 1786 22013 5.3 0.5336 7.6 0.0722 3.6 0.45 449.4 15.5 434.2 27.0 354.2 152. 449.4 15.5 4SZ14-14 1826 22565 2.4 0.6064 3.8 0.0800 3.3 0.87 496.3 15.8 481.3 14.6 410.5 42.16 496.3 15.8 4SZ14-15 304 10070 0.9 1.5817 2.0 0.1603 1.2 0.67 958.7 11.0 963.0 12.7 973.0 33.0 958.7 11.0 4SZ14-16 327 6720 1.2 0.6431 3.1 0.0811 1.0 0.31 502.4 4.8 504.2 12.4 512.5 65.0 502.4 4.8 4SZ14-17 1801 38699 2.4 0.6381 1.6 0.0817 1.0 0.62 506.4 4.9 501.1 6.3 476.9 27.5 506.4 4.9 4SZ14-18 640 10133 1.3 0.6364 6.1 0.0810 1.0 0.13 502.1 4.9 500.1 24.2 490.6 133. 502.1 4.9 4SZ14-19 179 17844 1.0 5.3935 1.4 0.3374 1.0 0.77 1874. 16.3 1883. 12.2 1894. 18.46 1874.3 16.3 4SZ14-20 178 4585 0.6 0.8615 2.2 0.1025 1.2 0.50 629.33 7.3 631.08 10.6 636.93 40.7 629.3 7.3 4SZ14-21 390 11217 2.5 1.3243 1.9 0.1418 1.0 0.54 854.7 8.0 856.4 10.8 860.8 32.7 854.7 8.0 4SZ14-22 178 9227 1.1 3.1623 1.8 0.2482 1.0 0.54 1429. 13.2 1448. 13.7 1476. 27.6 1429.0 13.2 4SZ14-23 376 2538 0.9 1.6149 2.1 0.1553 1.0 0.48 930.60 8.7 976.00 13.4 1079.0 37.8 930.6 8.7 4SZ14-24 319 4407 1.4 0.6322 4.0 0.0792 1.8 0.47 491.4 8.4 497.5 15.7 525.26 78.5 491.4 8.4 4SZ14-25 116 7128 1.2 2.1077 2.8 0.1891 2.3 0.84 1116. 23.4 1151. 19.4 1217. 32.3 1116.4 23.4 4SZ14-26 285 6015 2.1 0.5904 2.3 0.0754 1.2 0.51 468.34 5.3 471.13 8.8 484.87 44.4 468.3 5.3 4SZ14-27 1260 20533 3.0 0.5691 3.4 0.0729 3.2 0.91 453.8 13.9 457.4 12.6 475.6 27.2 453.8 13.9 4SZ14-28 298 4156 1.5 0.6058 4.9 0.0754 1.0 03.2 468.3 4.5 480.9 18.9 541.4 105. 468.3 4.5 4SZ14-29 175 5926 1.8 1.6613 3.2 0.1613 1.7 0.50 963.9 15.0 993.9 20.5 1060. 55.99 963.9 15.0 4SZ14-30 360 25766 3.4 4.3326 3.1 0.2653 2.3 0.72 1516. 31.1 1699. 25.9 1933.5 38.3 1516.7 31.1 4SZ14-31 108 2330 1.7 0.6718 7.6 0.0800 2.0 0.23 496.27 9.3 521.86 31.1 635.61 158. 496.2 9.3 4SZ14-32 120 5442 2.2 1.9087 2.2 0.1790 1.0 0.46 1061. 9.8 1084. 14.3 1130. 37.98 1061.4 9.8 6 4 1 1 189
4SZ14-33 266 13147 2.1 1.7691 1.5 0.1739 1.0 0.6 1033. 9.6 1034. 9.6 1035. 22.2 1033.7 9.6 4SZ14-34 440 9677 3.5 0.6155 5.1 0.0775 4.8 0.97 481.37 22.4 487.02 19.8 514.12 37.4 481.3 22.4 4SZ14-35 460 22840 2.4 1.9691 1.7 0.1883 1.2 0.64 1112. 12.3 1105. 11.7 1091. 25.3 1112.1 12.3 4SZ14-36 253 5829 1.9 0.9564 4.4 0.0955 3.9 0.89 587.91 21.7 681.40 21.9 1004.0 43.5 587.9 21.7 4SZ14-37 305 28261 1.8 3.7097 2.3 0.2759 2.1 0.97 1570. 28.7 1573. 18.3 1577.1 18.7 1570.5 28.7 4SZ14-38 432 22225 5.7 2.7238 1.8 0.2291 1.4 0.80 1329.5 17.1 1335.5 13.2 1343.5 20.5 1329.7 17.1 4SZ14-39 1220 33114 1.9 0.6000 2.6 0.0762 1.8 0.60 473.27 8.2 477.20 9.9 496.54 41.9 473.2 8.2 4SZ14-40 450 8429 1.4 0.5828 3.3 0.0743 1.9 0.59 461.9 8.5 466.3 12.3 487.7 59.1 461.9 8.5 4SZ14-41 197 8219 6.6 1.7426 2.3 0.1646 1.0 0.48 982.3 9.1 1024. 15.1 1115. 42.3 982.3 9.1 4SZ14-42 806 12170 3.3 0.8323 9.3 0.0762 1.3 0.13 473.6 5.8 614.94 43.0 1176.5 183. 473.6 5.8 4SZ14-43 104 14122 1.8 16.7804 1.9 0.5877 1.0 0.54 2980. 23.9 2922. 17.9 2882.7 25.70 2980.3 23.9 4SZ14-44 220 3810 1.9 0.6516 1.6 0.0820 1.0 0.63 507.83 4.9 509.44 6.6 516.97 28.7 507.8 4.9 4SZ14-45 348 12265 3.2 1.7435 3.1 0.1695 2.0 0.61 1009. 18.8 1024. 19.9 1058. 47.0 1009.1 18.8 4SZ14-46 1763 33951 34.3 0.6042 2.1 0.0804 1.0 0.45 498.51 4.8 479.98 8.0 391.83 41.3 498.5 4.8 4SZ14-48 775 9526 4.5 0.6226 1.5 0.0777 1.0 0.78 482.5 4.8 491.4 5.7 533.1 22.2 482.5 4.8 4SZ14-49 537 16645 0.7 2.1933 2.0 0.1977 1.6 0.72 1163. 17.0 1178. 14.2 1208. 24.7 1163.0 17.0 4SZ14-50 159 6345 1.6 1.4914 1.6 0.1527 1.0 0.69 916.20 8.7 926.99 10.0 952.51 26.4 916.2 8.7 4SZ14-51 315 6216 2.2 0.6276 3.0 0.0781 1.4 0.42 484.7 6.6 494.6 11.7 540.4 57.4 484.7 6.6 4SZ14-52 372 11798 2.0 1.8931 2.1 0.1830 1.3 0.67 1083. 13.1 1078. 14.2 1069. 34.1 1083.1 13.1 4SZ14-53 1075 10896 2.0 1.4429 5.2 0.1357 5.1 0.91 820.31 38.9 906.97 31.5 1124.8 28.2 820.3 38.9 4SZ14-54 187 4134 2.5 0.6219 3.5 0.0776 1.6 0.46 481.9 7.3 491.0 13.6 534.02 68.2 481.9 7.3 4SZ14-55 241 9546 1.8 2.6433 5.4 0.2265 4.6 0.85 1316. 54.4 1312. 40.0 1307. 56.6 1316.3 54.4 4SZ14-56 118 1857 0.4 0.6991 7.1 0.0832 2.4 0.34 515.43 11.8 538.38 29.7 636.50 144. 515.4 11.8 4SZ14-57 356 36428 1.8 6.4849 1.5 0.3683 1.1 0.74 2021. 19.4 2043. 13.2 2066. 17.72 2021.2 19.4 4SZ14-58 119 4712 1.8 1.4529 1.7 0.1523 1.3 0.75 914.02 11.1 911.18 10.2 904.07 22.7 914.0 11.1 4SZ14-59 245 38092 1.3 9.4897 1.6 0.4484 1.1 0.66 2388. 22.0 2386. 15.0 2385. 20.5 2388.2 22.0 4SZ14-60 792 14312 1.4 0.5965 1.4 0.0764 1.0 0.78 474.42 4.6 475.06 5.4 477.81 22.2 474.4 4.6 4SZ14-62 155 4242 1.1 0.5973 3.4 0.0751 1.7 0.40 467.0 7.5 475.5 12.9 516.6 65.1 467.0 7.5 4SZ14-63 234 33433 1.3 10.3910 1.6 0.4744 1.0 0.69 2502. 20.7 2470. 14.6 2443. 20.7 2502.8 20.7 4SZ14-64 182 11484 1.8 1.7565 2.0 0.1687 1.5 0.73 1004.8 14.0 1029.2 13.1 1082.5 27.1 1004.9 14.0 4SZ14-65 687 11750 1.4 0.5767 6.1 0.0781 1.0 0.14 485.09 4.7 462.46 22.7 351.22 136. 485.0 4.7 4SZ14-66 132 13497 1.2 7.5963 3.1 0.3731 2.6 0.86 2043. 44.7 2184. 28.2 2319. 31.42 2043.8 44.7 4SZ14-67 325 9678 3.3 0.8963 1.5 0.1037 1.0 0.61 635.98 6.1 649.84 7.2 698.12 23.6 635.9 6.1 4SZ14-68 176 5261 1.1 1.4909 2.5 0.1495 1.5 0.67 898.4 12.7 926.7 15.0 994.6 39.6 898.4 12.7 4SZ14-69 153 5499 0.6 1.6293 1.8 0.1567 1.4 0.71 938.4 12.1 981.6 11.4 1079. 23.3 938.4 12.1 4SZ14-70 443 14615 1.3 0.7907 1.8 0.0944 1.3 0.76 581.4 7.1 591.5 7.9 630.66 26.1 581.4 7.1 4SZ14-71 142 2448 1.5 0.6312 4.4 0.0778 1.0 0.22 483.0 4.7 496.9 17.4 561.4 94.0 483.0 4.7 4SZ14-72 114 2823 1.1 0.6125 3.3 0.0770 1.1 0.33 478.1 5.1 485.2 12.7 518.7 67.9 478.1 5.1 4SZ14-73 690 12570 0.9 0.5894 2.0 0.0763 1.1 04.5 474.2 5.1 470.5 7.7 452.2 37.8 474.2 5.1 4SZ14-74 1082 20795 3.7 0.6201 1.8 0.0792 1.4 0.75 491.2 6.4 489.9 7.0 483.7 26.4 491.2 6.4 4SZ14-75 92 1992 0.5 0.6627 4.3 0.0816 2.5 0.55 505.4 12.3 516.3 17.4 564.7 76.0 505.4 12.3 4SZ14-76 78 3621 4.1 1.5146 2.9 0.1552 1.9 0.69 929.8 16.2 936.3 17.7 951.6 45.1 929.8 16.2 4SZ14-77 166 2400 1.2 0.5090 3.5 0.0664 2.9 0.85 414.5 11.5 417.8 12.1 436.2 45.8 414.5 11.5 4SZ14-78 555 60804 57.7 8.5548 4.2 0.4151 3.2 0.71 2238. 59.9 2291. 37.8 2339. 46.0 2238.1 59.9 4SZ14-79 202 3836 1.6 0.6204 2.7 0.0777 1.0 0.36 482.31 4.6 490.18 10.6 526.49 55.9 482.3 4.6 4SZ14-81 49 1850 2.7 1.9720 3.6 0.1840 1.1 0.27 1088. 10.6 1106. 24.3 1139. 68.4 1088.8 10.6 4SZ14-82 718 63534 4.4 10.2171 3.6 0.4682 2.2 0.69 2475.8 45.2 2454.0 33.8 2437.9 49.3 2475.6 45.2 4SZ14-83 338 22535 0.7 9.3813 2.2 0.4439 1.8 0.80 2368.6 35.5 2376.6 20.2 2382.3 22.0 2368.2 35.5 4SZ14-84 647 41408 3.3 2.2052 3.3 0.1964 1.9 0.51 1156.2 20.2 1182.0 22.8 1231.7 51.8 1156.1 20.2 4SZ14-85 332 29708 3.6 5.1674 2.4 0.3314 2.2 0.89 1845.1 34.5 1847.7 20.6 1849.6 20.3 1845.2 34.5 4SZ14-86 335 8808 0.8 0.6074 1.7 0.0786 1.0 0.69 487.62 4.7 481.93 6.4 454.65 29.7 487.6 4.7 4SZ14-87 221 4248 1.0 0.6222 4.2 0.0785 3.8 0.90 487.4 17.8 491.3 16.5 509.3 41.4 487.4 17.8 4SZ14-88 168 15714 0.9 2.8815 1.8 0.2322 1.3 0.70 1346. 15.5 1377. 13.5 1425. 23.8 1346.0 15.5 2 0 1 6 190
4SZ14-89 160 8624 1.4 1.5252 2.9 0.1512 1.8 0.6 907.9 15.2 940.6 17.5 1017. 45.0 907.9 15.2 4SZ14-90 653 22784 10.7 1.4934 3.0 0.1513 1.0 0.33 908.3 8.5 927.7 18.0 974.08 56.7 908.3 8.5 4SZ14-91 229 4050 1.3 0.5859 2.0 0.0752 1.2 0.54 467.5 5.4 468.2 7.6 471.7 36.3 467.5 5.4 4SZ14-92 170 792 1.1 0.6419 10. 0.0752 1.0 0.09 467.6 4.5 503.5 43.2 669.9 232. 467.6 4.5 4SZ14-93 400 11228 1.5 0.5944 3.59 0.0750 3.0 0.89 466.4 13.6 473.7 13.2 509.0 37.52 466.4 13.6 4SZ14-94 272 18243 0.3 13.6532 3.6 0.4867 2.9 0.87 2556. 61.8 2726. 33.6 2854. 32.7 2556.4 61.8 4SZ14-95 339 16013 0.6 1.5969 2.5 0.1616 2.1 0.82 965.74 18.7 969.00 15.5 976.41 27.4 965.7 18.7 4SZ14-96 350 5383 1.8 0.5843 2.0 0.0760 1.0 0.54 472.4 4.6 467.2 7.5 441.9 38.7 472.4 4.6 4SZ14-97 1451 23699 1.6 0.5837 3.0 0.0735 2.8 0.90 457.0 12.2 466.9 11.2 515.6 25.1 457.0 12.2 4SZ14-98 60 3099 1.0 1.5473 3.5 0.1569 2.2 0.62 939.4 19.1 949.4 21.4 972.7 55.2 939.4 19.1 4SZ14-99 2301 21649 3.0 0.3523 9.7 0.0465 9.7 0.93 292.8 27.7 306.4 25.7 411.5 24.5 292.8 27.7 4SZ14-100 401 39517 1.5 10.1380 2.3 0.4673 1.9 0.89 2471. 38.6 2447. 21.7 2427. 23.8 2471.6 38.6 4SZ14-101 412 8562 1.4 0.6966 5.8 0.0824 1.2 0.20 510.46 5.9 536.74 24.0 650.34 120. 510.4 5.9 4SZ14-102 114 2149 0.5 0.6369 2.2 0.0802 1.3 0.51 497.4 6.2 500.4 8.8 514.1 40.09 497.4 6.2 4SZ14-103 173 8778 2.4 1.3405 3.4 0.1390 3.2 0.98 838.9 25.3 863.5 19.7 927.0 22.7 838.9 25.3 4SZ14-104 384 14693 2.7 0.9779 5.5 0.1021 5.2 0.95 626.7 31.2 692.5 27.7 912.5 36.4 626.7 31.2 4SZ14-105 546 35979 1.2 2.6139 1.8 0.2189 1.5 0.85 1276. 16.8 1304. 12.9 1351. 19.3 1276.2 16.8 4SZ14-106 425 8695 2.4 0.6196 2.6 0.0778 1.0 0.32 483.22 4.7 489.65 10.3 519.64 53.8 483.2 4.7 4SZ14-107 432 17578 1.7 1.5472 1.7 0.1578 1.2 0.68 944.7 10.4 949.4 10.7 960.1 25.8 944.7 10.4 4SZ14-109 315 6656 1.2 0.6185 9.5 0.0747 1.3 0.18 464.4 5.7 488.9 37.0 605.6 204. 464.4 5.7 4SZ14-110 595 10906 3.5 0.5921 2.4 0.0755 1.9 0.83 469.3 8.7 472.2 8.9 486.5 30.18 469.3 8.7 LWRCGM5815- 311 28963 1.6 1.55812 4.4 0.1614 4.1 0.92 964.7 37.1 953.7 27.4 928.5 31.7 928.5 31.7 LWRCGM58151 - 434 760 1.2 0.14765 17. 0.01482 5.9 0.34 94.7 5.5 139.8 22.9 996.5 337. 996.5 337. L2 WRCGM5815- 288 2296 1.1 0.10274 10.5 0.01500 3.8 0.34 96.1 3.6 99.3 10.1 176.0 234.9 96.1 3.69 LWRCGM58153 - 1006 3189 1.6 0.02365 8.37 0.00352 4.5 0.55 22.7 1.0 23.7 1.9 133.8 163.2 22.7 1.0 LWRCGM58154 - 945 17235 1.1 1.69715 8.1 0.16432 7.8 0.94 980.8 70.8 1007. 51.6 1065. 43.68 1065.8 43.6 LWRCGM58155 - 813 4323 0.9 0.06305 6.2 0.00853 5.1 0.86 54.8 2.8 62.15 3.7 353.68 78.5 54.8 2.8 LWRCGM58156 - 1098 12432 1.2 10.7257 5.3 0.46603 4.8 0.93 2466. 98.4 2499. 49.2 2527. 37.3 2527.0 37.3 LWRCGM58157 - 388 121724 3.9 13.98980 4.7 0.51863 4.4 0.91 2693.1 97.5 2749.7 44.6 2790.0 25.7 2790.1 25.7 LWRCGM58158 - 186 104387 0.8 0.788262 5.0 0.09653 4.5 0.94 594.14 25.7 590.20 22.5 575.21 47.3 575.2 47.3 LWRCGM58159 - 503 2770 0.7 0.05172 10. 0.00784 4.8 0.40 50.5 2.4 51.2 5.2 85.5 220. 50.5 2.4 LWRCGM581511 - 559 2794 0.8 0.04806 5.45 0.00726 2.0 0.36 46.8 0.9 47.7 2.5 92.3 120.7 46.8 0.9 LWRCGM581514 - 657 3885 1.2 0.05725 5.3 0.00848 2.6 0.46 54.4 1.4 56.5 2.9 145.4 108.1 54.4 1.4 LWRCGM581515 - 2499 7338 1.8 0.04839 5.8 0.00758 3.9 0.69 48.2 1.9 48.0 2.7 35.5 102.3 48.2 1.9 LWRCGM581516 - 308 2811 1.1 0.04642 8.9 0.00751 3.4 0.38 48.6 1.7 46.1 4.0 -84.5 200.8 48.6 1.7 LWRCGM581517 - 85 21643 1.1 8.14814 3.6 0.38047 3.1 0.89 2078. 55.0 2247. 32.8 2405. 32.26 2405.5 32.2 LWRCGM581518 - 429 2389 1.9 0.06318 8.6 0.00945 2.7 0.35 60.64 1.6 62.26 5.2 125.15 191. 60.6 1.6 LWRCGM581520 - 3056 2847 0.6 0.02544 5.7 0.00364 3.7 0.62 23.2 0.8 25.5 1.4 247.5 100.7 23.2 0.8 LWRCGM581521 - 191 26389 2.0 2.56256 3.9 0.21921 2.7 04.6 1277. 30.9 1290. 28.8 1310. 56.30 1310.6 56.3 LWRCGM581522 - 257 2224 1.0 0.08992 8.5 0.01321 3.0 0.38 85.17 2.5 87.40 7.1 151.36 186. 85.1 2.5 LWRCGM581523 - 654 30078 1.0 0.80448 1.7 0.09659 1.4 0.85 594.3 7.9 599.4 7.8 618.6 21.85 618.6 21.8 LWRCGM524 815- 883 78339 2.4 4.43353 3.2 0.30797 2.8 0.81 1730. 42.6 1718. 26.7 1703. 29.3 1703.9 29.3 LWRCGM581525 - 827 12534 4.3 3.63601 6.6 0.25068 6.2 0.97 1442.8 80.5 1557.6 52.9 1717.9 42.3 1717.7 42.3 LWRCGM5815S6 - 460 409830 1.5 1.12678 1.7 0.12439 1.0 0.64 755.50 7.1 766.24 8.9 797.67 27.6 797.6 27.6 LWRCGM581527 - 1352 10014 8.5 2.66482 2.1 0.22944 1.4 0.61 1331. 16.4 1318. 15.3 1297. 30.5 1297.9 30.5 LWRCGM581528 - 660 15153 4.7 0.01935 9.4 0.00366 3.4 0.36 23.26 0.8 19.58 1.8 -9425.0 231. 23.2 0.8 L29WRCGM5815 - 524 4359 1.1 0.10844 3.6 0.01531 2.2 0.66 98.0 2.1 104.5 3.6 255.2 66.87 98.0 2.1 LWRCGM581530 - 229 26313 1.4 1.60652 2.5 0.16083 2.1 0.80 961.7 18.7 972.8 15.8 997.8 28.7 997.8 28.7 LWRCGM581531 - 101 10233 0.8 2.16061 2.0 0.20139 1.4 0.63 1182. 15.0 1168. 13.9 1142. 28.8 1142.9 28.8 LWRCGM581532 - 597 302 0.4 0.04066 40. 0.00390 8.8 0.29 25.23 2.2 40.55 15.9 1074.9 814. 1074.7 814. LWRCGM581533 - 813 3904 0.9 0.05047 6.60 0.00722 4.3 0.62 46.7 2.0 50.0 3.2 211.27 117.1 46.7 2.01 LWRCGM581534 - 1330 3608 0.8 0.02500 5.5 0.00367 3.4 0.64 23.5 0.8 25.1 1.4 180.4 99.91 23.5 0.8 LWRCGM581535 - 2701 64570 2.3 0.57435 8.4 0.07395 8.0 0.93 460.0 35.5 460.8 31.2 465.1 58.7 465.1 58.7 36 6 5 191
LWRCGM5815- 584 85658 1.7 10.1738 3.8 0.4544 3.3 0.8 2414. 66.6 2450. 35.1 2480. 31.5 2480.6 31.5 LWRCGM581537 - 788 14086 1.2 6.982057 9.4 0.34610 9.1 0.97 1916.8 150. 2109.7 83.7 2303.6 42.1 2303.1 42.1 LWRCGM581538 - 354 11331 1.1 0.70326 2.6 0.08824 2.1 0.77 545.01 10.95 540.71 11.0 522.81 35.4 522.8 35.4 LWRCGM5840 15- 1021 23699 3.6 0.31343 7.4 0.04052 7.0 0.99 256.0 17.5 276.8 17.8 457.1 52.8 457.1 52.8 LWRCGM581539 - 343 1736 1.1 0.04905 10. 0.00751 3.0 0.25 48.3 1.4 48.6 5.2 65.1 249. 48.3 1.4 LWRCGM581541 - 79 270 1.1 0.03560 30.9 0.00782 6.9 0.27 50.6 3.5 35.5 10.5 -895.3 861.7 50.6 3.5 LWRCGM581542 - 1265 3541 1.3 0.06088 6.50 0.00878 2.3 0.33 56.0 1.3 60.0 3.8 223.0 139.4 56.0 1.3 LWRCGM581543 - 368 1467 0.6 0.03389 11. 0.00623 3.1 0.26 40.1 1.2 33.8 3.7 -388.7 276.5 40.1 1.2 LWRCGM581544 - 312 1825 1.3 0.04940 9.00 0.00784 4.3 0.48 50.2 2.1 49.0 4.3 -12.9 192.0 50.2 2.1 LWRCGM581545 - 1322 1557 1.1 0.04719 8.1 0.00642 4.3 0.57 41.5 1.8 46.8 3.7 330.2 157.6 41.5 1.8 LWRCGM581546 - 1929 4539 3.4 0.03842 8.6 0.00575 7.7 0.82 36.8 2.8 38.3 3.2 130.5 90.93 36.8 2.8 LWRCGM581548 - 892 4037 0.9 0.04873 3.8 0.00753 1.5 0.39 48.5 0.7 48.3 1.8 41.1 82.6 48.5 0.7 LWRCGM581549 - 297 29621 2.6 1.83189 7.3 0.17354 6.9 0.99 1031. 65.9 1057. 47.8 1109. 45.2 1109.8 45.2 LWRCGM581550 - 601 1472 1.8 0.01971 16. 0.00374 6.5 0.35 24.06 1.6 19.80 3.3 -8457.9 409. 24.0 1.6 LWRCGM581551 - 632 3145 0.9 0.04504 4.37 0.00702 3.0 0.79 45.0 1.4 44.7 1.9 28.3 72.00 45.0 1.4 LWRCGM581553 - 303 59125 0.8 10.3110 2.4 0.45551 1.9 0.71 2420. 37.9 2463. 22.4 2498. 25.8 2498.9 25.8 LWRCGM58154 5- 1314 4437 1.4 0.051697 4.0 0.00748 1.3 0.38 47.80 0.6 51.21 2.0 210.29 87.6 47.8 0.6 LWRCGM581555 - 756 32573 2.5 1.50131 4.9 0.15725 3.6 0.73 941.3 31.5 930.9 30.1 906.5 69.7 906.5 69.7 LWRCGM581556 - 545 33254 1.8 2.64163 4.6 0.22511 2.7 0.53 1308. 31.7 1312. 33.6 1317. 71.8 1317.9 71.8 LWRCGM581557 - 421 25273 1.3 1.37457 2.6 0.14333 2.2 0.89 863.59 17.9 878.13 15.2 915.19 27.2 915.1 27.2 LWRCGM581558 - 244 39003 0.7 10.4239 2.3 0.44964 1.3 0.56 2393. 25.7 2473. 21.5 2539. 32.4 2539.0 32.4 LWRCGM5859 15- 327 1947 1.5 0.061046 9.0 0.00948 2.7 0.25 60.68 1.6 60.22 5.3 43.80 205. 60.6 1.6 LWRCGM581560 - 423 34024 0.9 1.61579 2.3 0.15974 1.3 0.59 955.2 11.8 976.4 14.7 1024. 38.99 1024.2 38.9 LWRCGM581561 - 187 361 1.6 0.07345 19. 0.00892 10. 0.57 57.6 5.8 72.0 13.3 580.82 354. 580.8 354. LWRCGM581562 - 911 73115 1.7 2.60225 3.61 0.22557 2.02 0.53 1310. 24.1 1301. 26.7 1285. 58.82 1285.4 58.82 LWRCGM581563 - 246 692 0.9 0.02026 25. 0.00371 6.3 0.26 23.99 1.5 20.43 5.2 -4377.5 652. 23.9 1.5 LWRCGM581564 - 379 915 0.9 0.05541 8.86 0.00751 4.4 0.55 48.7 2.2 54.8 4.7 327.7 171.5 48.7 2.2 LWRCGM581566 - 971 42556 2.1 0.83573 2.1 0.09959 1.4 0.61 611.9 8.1 616.8 9.6 634.7 33.09 634.7 33.0 LWRCGM581570 - 827 2706 1.5 0.05486 7.0 0.00858 2.9 0.47 54.9 1.6 54.2 3.7 25.7 151. 54.9 1.6 LWRCGM581572 - 2815 3248 4.4 0.02440 3.2 0.00365 2.0 0.62 23.1 0.5 24.5 0.8 158.2 58.55 23.1 0.5 LWRCGM581574 - 488 2472 0.8 0.04369 10. 0.00720 2.6 0.22 46.5 1.2 43.4 4.5 -121.9 253. 46.5 1.2 LWRCGM581575 - 205 2091 1.5 0.03874 25.6 0.0083 2 6.0 0.25 53.2 3.2 38.6 9.7 -798.0 718.1 53.2 3.2 LWRCGM581576 - 306 1538 1.4 0.06186 11.7 0.00879 4.3 0.33 56.0 2.4 60.9 6.7 260.1 243.3 56.0 2.4 LWRCGM581577 - 220 1252 0.7 0.04271 13.4 0.00842 5.4 0.47 54.1 2.9 42.5 5.6 -574.5 337.1 54.1 2.9 LWRCGM5878 15- 613 1533 3.5 0.02774 13.6 0.00413 4.9 0.30 26.4 1.3 27.8 3.7 153.5 292.8 26.4 1.3 LWRCGM581579 - 305 2084 0.9 0.05074 7.84 0.00880 4.4 0.57 56.8 2.5 50.3 3.8 -253.8 164.9 56.8 2.5 LWRCGM581580 - 512 41419 3.4 2.19791 2.0 0.20226 1.0 0.46 1187. 10.8 1180. 14.1 1167. 34.96 1167.5 34.9 LWRCGM581581 - 801 33148 1.6 0.83968 3.0 0.10135 1.9 0.69 622.04 11.5 619.04 13.9 607.75 49.1 607.7 49.1 LWRCGM581582 - 432 1741 1.2 0.04817 9.3 0.00840 3.3 0.35 54.0 1.8 47.8 4.3 -252.9 220. 54.0 1.8 LWRCGM581583 - 646 3539 1.0 0.05068 5.7 0.00740 3.5 0.65 47.9 1.7 50.2 2.8 160.7 105.0 47.9 1.7 LWRCGM581585 - 127 1033 0.5 0.04692 22. 0.01236 8.5 0.32 79.3 6.7 46.6 10.2 - 681.7 79.3 6.7 LWRCGM581586 - 131 1260 1.0 0.07385 10.3 0.01298 5.6 0.58 82.9 4.6 72.3 7.5 -1436.264.3 232.2 82.9 4.6 1 LWRCGM581587 - 129 21559 1.9 3.97715 3.97 0.29204 2.8 0.72 1651. 40.6 1629. 31.3 1600. 49.96 1600.8 49.9 LWRCGM581588 - 405 38613 1.2 1.77575 4.1 0.17457 3.2 0.72 1037.9 30.8 1036.5 26.7 1035.8 51.6 1035.4 51.6 LWRCGM581589 - 145 720 0.4 0.04569 19. 0.01126 8.0 0.48 72.12 5.7 45.46 8.7 -4 558. 72.1 5.7 LWRCGM581592 - 1485 2289 1.2 0.04488 8.75 0.00615 2.2 0.21 39.4 0.8 44.6 3.8 333.41215. 190.0 39.4 0.8 9 LWRCGM581593 - 157 29899 1.7 9.62528 1.9 0.42573 1.4 0.75 2286. 27.3 2399. 17.6 2496. 21.66 2496.9 21.6 LWRCGM581594 - 434 2576 0.8 0.08124 5.1 0.01208 3.5 0.64 77.27 2.7 79.36 3.9 142.59 88.7 77.2 2.7 LWRCGM581595 - 1424 8068 23.6 0.05193 3.6 0.00745 2.2 0.68 47.6 1.1 51.4 1.8 235.0 64.0 47.6 1.1 LWRCGM581597 - 579 1612 1.1 0.03535 8.1 0.00620 2.6 0.33 40.2 1.1 35.3 2.8 -287.4 196. 40.2 1.1 LWRCGM581598 - 4265 5313 2.3 0.02387 6.0 0.00355 4.8 0.82 22.7 1.1 23.9 1.4 146.2 84.58 22.7 1.1 LWRCGM581599 - 965 4185 1.4 0.05679 3.6 0.00873 1.5 0.40 55.9 0.8 56.1 2.0 62.9 77.8 55.9 0.8 LWRCGM5815100 - 373 1276 1.4 0.04331 12. 0.00761 1.8 0.11 49.0 0.9 43.0 5.4 -278.2 321. 49.0 0.9 101 7 3 4 3 192
LWRCGM5815- 465 30448 2.3 2.77752 1.6 0.2291 1.0 0.6 1329. 12.0 1349. 12.0 1380. 24.3 1380.7 24.3 LWRCGM5815102 - 1470 494 3.0 0.08162 14. 0.00953 3.4 0.22 61.59 2.1 79.75 11.1 665.17 303. 665.1 303. LWRCGM5815103 - 661 669 0.8 0.06963 16.5 0.00859 2.9 0.13 54.7 1.6 68.3 11.2 575.3 364.9 575.3 364.9 LWRCGM5815104 - 458 63843 3.4 9.64149 2.39 0.43533 2.1 0.87 2329. 40.2 2401. 21.4 2462. 18.67 2462.4 18.67 LWRCGM5815105 - 107 1302 0.1 1.27056 20. 0.12360 20. 0.98 751.56 145. 832.61 118. 1055.4 65.1 1055.7 65.1 LWRCGM5815106 - 1126 79075 8.5 1.55394 1.48 0.15875 1.05 0.79 949.9 8.86 952.1 8.76 957.17 20.5 957.1 20.5 LWRCGM5815108 - 247 48276 0.9 10.5791 6.3 0.48066 5.9 0.1 9 2530. 124. 2486. 58.9 2451. 37.1 2451.8 37.1 LWRCGM5815109 - 166 783 0.8 0.044132 18. 0.01135 4.9 0.24 72.41 3.55 43.89 7.9 -8 572. 72.4 3.5 LWRCGM5815110 - 602 2744 0.7 0.04750 5.34 0.00730 3.2 0.57 47.1 1.5 47.1 2.4 45.61338. 102.4 47.1 1.5 8 LWRCGM58111 15- 379 986 0.8 0.05382 12. 0.00854 4.2 0.39 54.6 2.3 53.2 6.6 -6.1 289.3 54.6 2.3 LWRCGM5815112 - 1955 1034 2.3 0.03154 14.7 0.00390 1.9 0.13 25.1 0.5 31.5 4.4 553.0 308.6 25.1 0.5 LWRCGM5815113 - 105 6553 1.7 0.85098 2.32 0.09670 1.5 0.63 595.5 8.4 625.2 10.7 734.1 37.42 734.1 37.4 LWRCGM5815114 - 274 24522 1.4 1.42484 3.3 0.15118 2.1 0.64 907.5 17.7 899.4 19.4 879.4 51.7 879.4 51.7 2NWZ25115 -1 3365 4543 1.9 0.03813 3.2 0.00597 2.6 0.84 38.4 1.0 38.0 1.2 10.5 45.7 38.4 1.0 2NWZ25-2 226 14183 0.9 1.70502 3.2 0.16908 2.5 0.70 1006. 23.3 1010. 20.3 1018. 39.5 1018.3 39.5 2NWZ25-4 6147 7224 2.7 0.03262 4.7 0.00533 2.8 0.59 34.68 1.0 32.64 1.5 -3115.3 94.0 34.6 1.0 2NWZ25-5 887 27021 0.9 1.23186 4.2 0.13099 3.9 0.99 793.1 29.1 815.2 23.4 875.9 30.7 875.9 30.7 2NWZ25-6 562 13561 0.7 1.66254 17. 0.15532 15. 0.93 930.9 133. 994.3 109. 1137. 152. 1137.1 152. 2NWZ25-8 4719 10124 2.4 0.05619 2.82 0.00885 2.14 0.70 57.1 1.27 55.5 1.56 -111.8 45.86 57.1 1.26 2NWZ25-9 958 38567 9.5 1.49378 3.2 0.14989 3.0 0.94 900.3 25.6 927.9 19.7 993.9 22.2 993.9 22.2 2NWZ25-10 3765 1250 0.8 0.03809 8.1 0.00538 2.0 0.24 34.4 0.7 38.0 3.0 272.4 181. 34.4 0.7 2NWZ25-11 5187 36439 1.3 1.08255 3.6 0.12114 3.0 0.84 737.1 21.1 744.9 19.2 768.3 42.32 768.3 42.3 2NWZ25-12 7029 4372 1.7 0.04857 7.6 0.00734 3.1 0.43 47.2 1.5 48.2 3.6 97.7 165. 47.2 1.5 2NWZ25-13 2769 3962 1.5 0.03875 5.1 0.00564 2.0 0.31 36.4 0.7 38.6 1.9 175.1 109.0 36.4 0.7 2NWZ25-14 3275 8414 6.8 0.36742 4.5 0.03987 4.4 0.99 251.8 10.8 317.7 12.3 834.7 24.33 834.7 24.3 2NWZ25-15 2179 4168 1.5 0.05072 13. 0.00683 3.8 0.27 44.1 1.6 50.2 6.8 355.4 301. 44.1 1.6 2NWZ25-16 5481 6087 0.8 0.04683 2.08 0.00726 1.3 0.67 46.6 0.6 46.5 0.9 39.2 37.17 46.6 0.6 2NWZ25-18 966 49142 2.8 4.87589 10. 0.30856 9.8 0.94 1733. 149. 1798. 84.3 1873. 32.5 1873.6 32.5 2NWZ25-21 4978 4237 2.3 0.03663 3.60 0.00578 2.2 0.68 36.77 0.83 36.51 1.3 23.66 69.0 36.7 0.8 2NWZ25-22 4697 39155 12.4 0.99097 5.5 0.10721 4.5 0.81 656.8 27.9 699.2 28.0 837.9 68.4 837.9 68.4 2NWZ25-24 637 18853 0.8 1.90525 1.8 0.18336 1.5 0.81 1085. 14.9 1082. 12.1 1078. 20.6 1078.8 20.6 2NWZ25-25 250 8742 1.9 1.32126 14. 0.14250 14. 0.92 858.80 118. 855.19 86.4 845.38 44.3 845.3 44.3 2NWZ25-26 4498 10916 1.1 0.04574 3.49 0.00741 1.28 0.39 48.1 0.66 45.4 1.5 -94.8 77.1 48.1 0.6 2NWZ25-27 1712 59299 1.3 4.48507 6.4 0.29639 5.6 0.86 1673. 83.0 1728. 52.8 1795. 53.4 1795.3 53.4 2NWZ25-28 569 41942 2.0 1.33520 5.2 0.14298 5.0 0.99 861.14 40.3 861.12 30.3 861.33 30.7 861.3 30.7 2NWZ25-29 144 3108 1.4 1.18470 6.3 0.13061 5.7 0.96 791.3 42.7 793.5 35.0 799.7 56.9 799.7 56.9 2NWZ25-30 2215 10628 1.8 0.78327 2.6 0.09010 2.3 0.80 556.4 12.1 587.3 11.6 708.8 26.8 708.8 26.8 2NWZ25-31 2327 3772 0.6 0.03402 4.3 0.00535 3.2 0.77 34.6 1.1 34.0 1.4 -13.3 70.2 34.6 1.1 2NWZ25-32 4121 7422 2.2 0.03804 3.2 0.00569 2.1 0.64 36.6 0.8 37.9 1.2 123.6 56.7 36.6 0.8 2NWZ25-33 1332 55293 3.3 0.60504 2.9 0.07539 2.1 0.76 468.4 9.7 480.4 10.9 538.4 41.4 538.4 41.4 2NWZ25-34 869 70306 1.5 1.81166 2.3 0.17456 1.0 0.45 1037. 9.6 1049. 14.8 1075. 40.6 1075.9 40.6 2NWZ25-35 5716 3447 1.6 0.03660 11. 0.00545 1.6 0.14 35.11 0.6 36.57 4.2 131.99 270. 35.1 0.6 2NWZ25-36 1198 28650 1.9 0.59594 2.76 0.07545 2.0 0.74 468.6 9.1 474.7 10.2 504.0 39.86 504.0 39.8 2NWZ25-37 872 9038 1.1 0.72181 3.0 0.08690 2.3 0.74 537.5 12.0 551.7 12.6 610.8 39.9 610.8 39.9 2NWZ25-39 373 55274 4.4 1.24285 4.2 0.13326 3.7 0.88 806.4 27.9 820.2 23.5 857.7 41.3 857.7 41.3 2NWZ25-40 633 92035 4.1 4.52589 2.0 0.28395 1.7 0.88 1611. 23.9 1735. 16.3 1889. 18.0 1889.1 18.0 2NWZ25-41 3606 4555 0.5 0.04865 4.9 0.00707 3.5 0.76 45.43 1.6 48.27 2.3 190.21 81.1 45.4 1.6 2NWZ25-42 616 25558 2.3 0.79847 2.6 0.09417 2.0 0.71 579.8 10.9 596.0 11.7 657.8 36.0 657.8 36.0 2NWZ25-43 3105 61610 17.7 1.55631 4.1 0.15602 3.5 0.86 935.0 30.2 953.0 25.6 994.8 46.2 994.8 46.2 2NWZ25-44 170 5987 0.9 2.76407 4.1 0.23389 2.5 0.64 1354. 30.9 1345. 30.7 1331. 62.8 1331.7 62.8 2NWZ25-45 1503 3402 2.4 0.04462 5.0 0.00629 2.8 0.51 40.59 1.1 44.39 2.2 259.17 95.0 40.5 1.1 2NWZ25-46 1008 36861 0.8 1.27320 2.2 0.13589 1.8 0.86 821.1 14.2 833.8 12.4 867.8 24.4 867.8 24.4 2NWZ25-48 2232 39305 3.3 0.58033 2.5 0.07355 2.0 0.74 457.6 8.7 464.7 9.3 500.0 33.6 500.0 33.6 6 9 193
2NWZ25-49 2922 10317 8.8 0.56105 10. 0.0680 10. 0.9 424.7 43.6 452.2 39.5 594.8 47.7 594.8 47.7 2NWZ25-51 561 15194 1.4 1.41584 5.78 0.13579 5.56 0.98 820.5 42.5 895.6 33.6 1086. 24.0 1086.0 24.0 2NWZ25-50 6054 4627 1.3 0.03505 2.7 0.00553 2.1 0.78 35.5 0.8 35.0 0.9 -02.1 41.5 35.5 0.8 2NWZ25-52 6541 17776 4.7 0.04576 2.9 0.00723 2.6 0.88 46.4 1.2 45.4 1.3 -8.1 30.9 46.4 1.2 2NWZ25-53 1796 28080 3.2 0.91995 4.0 0.10933 3.2 0.79 668.9 20.3 662.3 19.6 639.9 53.0 639.9 53.0 2NWZ25-55 784 20761 1.9 0.59540 3.2 0.07384 2.5 0.79 459.1 11.1 474.3 12.3 548.5 44.7 548.5 44.7 2NWZ25-57 1335 29964 2.0 1.07370 6.2 0.11352 6.0 0.97 693.1 39.4 740.6 32.6 886.8 32.3 886.8 32.3 2NWZ25-58 5365 2975 1.3 0.04836 9.1 0.00721 8.0 0.87 46.6 3.7 48.0 4.3 116.7 105. 46.6 3.7 2NWZ25-59 2220 4820 1.0 0.04545 4.3 0.00685 1.3 0.37 43.7 0.6 45.1 1.9 120.3 96.23 43.7 0.6 2NWZ25-60 1381 1960 0.4 0.03405 8.9 0.00531 2.2 0.20 34.1 0.7 34.0 3.0 25.8 208. 34.1 0.7 2NWZ25-61 610 34507 1.3 1.96983 2.5 0.18651 1.4 0.54 1102. 14.2 1105. 16.9 1110. 41.46 1110.2 41.4 2NWZ25-62 674 49022 1.3 4.92328 4.5 0.29786 3.6 0.86 17680. 53.3 1806.2 38.1 1954.2 48.6 1954.3 48.6 2NWZ25-63 1026 68183 1.1 1.94227 5.2 0.18428 5.1 0.90 1090.8 51.2 1095.3 34.9 1106.3 20.1 1106.6 20.1 2NWZ25-64 1135 1403 0.7 0.03224 18. 0.00549 3.3 0.18 35.24 1.2 32.28 5.8 -6186.8 448. 35.2 1.2 2NWZ25-65 1344 1776 1.0 0.03475 7.91 0.00548 3.9 0.48 34.9 1.4 34.7 2.7 16.5 165.6 34.9 1.4 2NWZ25-66 132 5435 2.2 1.48515 2.4 0.15384 1.6 0.69 922.7 13.9 924.3 14.5 928.2 36.27 928.2 36.2 2NWZ25-67 600 13660 1.5 3.93033 1.5 0.27999 1.0 0.68 1591. 14.1 1619. 12.1 1657. 20.6 1657.7 20.6 2NWZ25-68 986 42776 1.9 1.05891 5.3 0.11514 5.0 0.97 702.81 33.1 733.39 27.6 827.67 37.1 827.6 37.1 2NWZ25-69 4226 10954 3.6 0.04017 2.6 0.00578 2.2 0.84 37.1 0.8 40.0 1.0 216.2 33.0 37.1 0.8 2NWZ25-70 8293 29747 2.1 0.03760 3.3 0.07 057 2.0 0.63 37.0 0.7 37.5 1.2 71.6 62.1 37.0 0.7 2NWZ25-72 2558 1343 39.2 0.02759 6.8 0.00375 2.8 0.41 23.8 0.7 27.6 1.9 371.6 139. 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0.19071 1.8 0.70 1125. 19.1 1147. 16.5 1187. 30.46 1187.7 30.4 2NWZ25-88 3368 5000 0.4 0.03744 3.0 0.00556 1.3 0.47 35.85 0.5 37.30 1.1 138.07 64.2 35.8 0.5 2NWZ25-89 822 33513 3.4 2.44024 1.4 0.21126 1.0 0.74 1235. 11.4 1254. 10.3 1287. 19.6 1287.5 19.6 2NWZ25-90 4542 9253 2.4 0.03898 3.2 0.00574 2.4 0.71 36.74 0.9 38.85 1.2 171.75 48.5 36.7 0.9 2NWZ25-91 2364 3250 0.5 0.56907 3.2 0.1 0704 2.2 0.76 438.7 9.4 457.4 11.7 552.6 50.0 552.6 50.0 2NWZ25-92 8265 13456 1.8 0.03509 3.1 0.00562 2.2 0.70 36.2 0.8 35.0 1.1 -44.0 51.9 36.2 0.8 2NWZ25-93 8699 9381 2.5 0.03318 2.1 0.00523 1.0 0.42 33.7 0.3 33.1 0.7 -9.1 45.1 33.7 0.3 2NWZ25-95 3680 2234 0.8 0.03675 4.8 0.00525 3.0 0.67 33.5 1.0 36.6 1.7 249.9 85.3 33.5 1.0 2NWZ25-96 965 1320 1.0 0.02458 11. 0.00541 2.9 0.23 35.2 1.0 24.7 2.7 -910.8 310. 35.2 1.0 2NWZ25-97 7516 894 0.8 0.04271 17.0 0.00547 7.1 0.46 35.1 2.5 42.5 7.4 479.5 362.5 35.1 2.5 2NWZ25-98 1121 90467 3.5 1.14041 2.08 0.12316 1.4 0.70 748.8 10.2 772.7 10.8 842.5 28.73 842.5 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0.1847 1.3 09.5 1092. 13.0 1092. 15.3 1092. 37.9 1092.9 37.9 SMZ35-2 1094 32976 4.1 0.5568 3.1 0.0718 2.9 0.96 447.15 12.6 449.57 11.3 461.29 24.5 461.2 24.5 SMZ35-3 132 11877 0.9 1.7570 2.3 0.1715 1.1 0.54 1020. 10.8 1029. 14.6 1049. 39.2 1049.5 39.2 SMZ35-4 79 4698 0.9 1.0968 2.4 0.1136 1.1 0.41 693.65 7.4 751.87 12.9 929.25 44.1 929.2 44.1 SMZ35-5 239 21171 2.2 1.9244 4.2 0.1816 4.0 0.97 1075. 39.4 1089. 28.3 1117. 29.1 1117.3 29.1 SMZ35-6 3236 10556 14.5 0.6370 2.3 0.0815 1.3 0.54 505.07 6.2 500.46 9.2 479.53 43.3 479.5 43.3 SMZ35-7 420 61951 6.8 0.5773 3.0 0.0544 2.2 0.75 341.3 7.2 462.7 11.1 1121. 41.3 1121.4 41.3 SMZ35-9 68 13401 0.5 10.0358 3.3 0.4187 2.4 0.72 2254. 46.0 2438. 30.8 2595.4 38.4 2595.0 38.4 SMZ35-10 347 31293 1.9 1.5560 1.8 0.1593 1.2 02.6 953.15 10.9 952.91 11.4 952.40 28.0 952.4 28.0 SMZ35-11 68 5949 2.3 1.6836 3.5 0.1521 1.3 0.37 912.8 11.4 1002. 22.1 1203. 63.2 1203.5 63.2 SMZ35-12 207 14025 2.0 1.3468 3.0 0.1339 2.7 0.99 810.1 20.8 866.23 17.7 1012.5 27.1 1012.4 27.1 SMZ35-13 134 9186 2.6 1.6507 2.5 0.1633 1.4 0.50 975.1 13.0 989.8 16.0 1022.4 42.2 1022.5 42.2 7 5 199
SMZ35-14 219 13629 1.1 1.1915 2.2 0.1285 1.8 0.8 779.3 12.9 796.7 12.1 845.5 26.9 845.5 26.9 SMZ35-15 109 7056 1.3 1.1275 2.9 0.1182 1.0 0.31 720.2 6.8 766.5 15.5 904.1 55.6 904.1 55.6 SMZ35-16 140 24558 2.5 9.6267 1.4 0.4376 1.0 0.75 2339. 19.6 2399. 13.0 2450. 16.9 2450.9 16.9 SMZ35-17 363 33252 2.9 2.0623 9.5 0.1903 2.1 0.21 1123.8 21.3 1136.7 65.1 1161.9 184. 1161.9 184. SMZ35-18 1910 60366 3.4 0.5747 2.9 0.0754 1.8 0.62 468.51 8.0 461.04 10.7 423.79 50.94 423.7 50.94 SMZ35-19 139 10437 1.5 1.7928 2.0 0.1739 1.0 0.51 1033. 9.5 1042. 13.1 1062. 35.2 1062.6 35.2 SMZ35-20 391 19623 1.5 1.4202 5.0 0.1413 2.5 0.50 852.05 19.7 897.59 29.5 1011.6 87.0 1011.2 87.0 SMZ35-21 141 8121 1.7 1.0975 4.1 0.1176 1.4 0.30 716.5 9.4 752.1 21.9 859.52 80.5 859.5 80.5 SMZ35-23 984 53502 5.9 1.1742 1.7 0.1259 1.0 0.54 764.6 7.2 788.6 9.3 857.1 28.5 857.1 28.5 SMZ35-24 428 11247 1.9 0.6318 7.3 0.0748 1.0 0.19 465.0 4.5 497.2 28.7 648.7 155. 648.7 155. SMZ35-25 31 2544 2.0 1.9723 3.6 0.1693 1.9 0.54 1008. 17.7 1106. 24.2 1303. 59.37 1303.9 59.37 SMZ35-26 332 17103 2.4 0.8061 4.1 0.0933 2.8 0.63 575.02 15.6 600.21 18.7 696.89 63.9 696.8 63.9 SMZ35-27 1916 14030 22.6 1.6436 2.1 0.1655 1.5 0.79 987.3 13.5 987.1 13.0 986.8 29.1 986.8 29.1 SMZ35-28 752 273001 1.9 0.6212 3.3 0.0644 1.5 0.42 402.4 5.8 490.6 12.8 926.7 60.4 926.7 60.4 SMZ35-29 661 37611 4.0 0.8146 3.4 0.0976 1.3 0.35 600.3 7.2 605.1 15.5 622.9 68.0 622.9 68.0 SMZ35-30 1168 58761 3.0 0.7738 4.0 0.0957 1.0 0.27 589.4 5.7 581.9 17.5 552.9 83.6 552.9 83.6 SMZ35-32 272 16137 3.0 1.0050 5.4 0.1052 1.5 0.25 644.8 9.0 706.4 27.3 907.2 106. 907.2 106. SMZ35-33 94 7701 1.4 1.7457 2.3 0.1670 1.4 0.67 995.6 12.8 1025. 14.7 1090. 36.3 1 1090.2 36.13 SMZ35-34 204 15933 2.4 1.6129 2.1 0.1541 1.0 0.41 924.1 8.6 975.26 13.4 1092.2 37.7 1092.3 37.7 SMZ35-35 643 58947 4.3 1.9406 2.2 0.1859 1.0 0.47 1099. 10.1 1095. 15.0 1087.3 40.1 1087.4 40.1 SMZ35-36 756 12588 8.1 0.5975 2.5 0.0738 1.0 05.3 458.81 4.4 475.62 9.6 557.54 50.9 557.5 50.9 SMZ35-37 325 24849 0.7 1.8242 4.3 0.1795 1.2 0.29 1064. 11.4 1054. 28.3 1033. 84.1 1033.4 84.1 SMZ35-38 787 22437 1.1 0.6006 2.0 0.0771 1.0 0.57 478.53 4.6 477.62 7.6 473.14 38.4 473.1 38.4 SMZ35-39 1085 44835 1.0 1.3823 6.3 0.1407 5.7 0.90 848.9 45.5 881.4 37.1 964.1 53.9 964.1 53.9 SMZ35-40 203 11301 0.6 1.5493 2.0 0.1558 1.0 0.51 933.5 8.7 950.2 12.1 989.0 34.3 989.0 34.3 SMZ35-41 128 6696 1.2 1.8907 3.2 0.1776 2.9 0.81 1054. 27.7 1077. 21.3 1126. 29.2 1126.3 29.2 SMZ35-42 1385 74766 18.6 1.4422 3.4 0.1476 1.1 0.39 887.80 9.1 906.78 20.3 952.93 65.7 952.9 65.7 SMZ35-43 231 11328 2.6 1.3503 2.1 0.1374 1.2 0.52 829.9 9.3 867.7 12.1 965.4 34.5 965.4 34.5 SMZ35-44 157 11664 1.2 1.6084 2.4 0.1599 1.0 0.48 956.2 8.9 973.5 15.1 1012. 44.6 1012.8 44.6 SMZ35-45 431 33882 2.1 1.6936 4.0 0.1660 1.0 0.21 989.8 9.2 1006. 25.5 1041.8 77.9 1041.8 77.9 SMZ35-46 396 29127 2.3 2.3295 4.6 0.1995 4.1 0.85 1172. 43.7 1221.1 32.7 1308.8 41.2 1308.3 41.2 SMZ35-47 90 5496 0.9 1.5578 3.5 0.1515 1.2 0.39 909.67 10.5 953.63 21.6 1056.3 65.8 1056.6 65.8 SMZ35-48 323 21516 1.4 1.9698 1.7 0.1838 1.0 0.55 1087. 10.0 1105. 11.4 1139.6 27.1 1139.5 27.1 SMZ35-49 58 3012 0.8 4.0173 7.1 0.2675 1.3 0.19 1528.9 17.0 1637.2 57.6 1781.5 127. 1781.1 127. SMZ35-50 193 2364 4.8 0.4556 5.2 0.0385 1.5 0.28 243.73 3.5 381.27 16.6 1332.1 97.02 1332.9 97.02 SMZ35-51 263 41181 2.2 8.9268 2.0 0.4039 1.7 0.88 2187. 31.7 2330. 18.1 2458.9 16.9 2458.7 16.9 SMZ35-52 238 9699 1.4 1.8342 2.4 0.1774 1.5 0.66 1052.0 14.9 1057.6 15.6 1068.7 36.4 1068.0 36.4 SMZ35-53 492 92751 7.6 6.9436 1.4 0.3843 1.0 0.74 2096.8 17.9 2104.8 12.6 2112.0 17.5 2112.1 17.5 SMZ35-54 1501 11831 12.1 1.9580 1.7 0.1829 1.0 0.51 1083.2 10.0 1101.2 11.3 1137.1 27.1 1137.3 27.1 SMZ35-55 369 198154 2.0 1.6490 2.1 0.1627 1.0 0.49 971.60 9.0 989.22 13.2 1028.3 37.1 1028.2 37.1 SMZ35-56 141 9372 2.4 1.5232 2.4 0.1537 1.8 0.78 921.4 15.1 939.8 14.5 983.02 32.0 983.0 32.0 SMZ35-57 78 5388 1.7 1.4811 2.7 0.1475 2.0 0.75 887.1 16.7 922.7 16.2 1008. 35.6 1008.8 35.6 SMZ35-58 399 31194 8.8 1.7655 2.3 0.1724 1.7 0.75 1025. 16.3 1032. 15.0 1049.8 31.3 1049.2 31.3 SMZ35-59 383 10437 1.8 0.6497 4.0 0.0799 1.0 0.24 495.62 4.8 508.39 15.9 566.22 83.5 566.2 83.5 SMZ35-60 436 40314 0.5 2.8835 2.2 0.2315 1.0 0.45 1342. 12.1 1377. 16.9 1433. 38.4 1433.0 38.4 SMZ35-61 341 22728 0.9 1.8239 1.8 0.1785 1.3 0.75 1059.1 12.4 1054.6 11.5 1043.0 24.5 1043.8 24.5 SMZ35-63 256 18033 2.1 1.5177 1.8 0.1536 1.0 0.52 921.10 8.6 937.61 10.9 976.48 30.0 976.4 30.0 SMZ35-64 19 2244 2.2 3.4575 3.8 0.2401 1.9 0.56 1387. 23.8 1517. 29.6 1704. 59.5 1704.5 59.5 SMZ35-65 465 25626 1.2 1.4915 3.6 0.1487 3.1 0.81 893.62 25.4 926.96 22.2 1007.5 40.6 1007.1 40.6 SMZ35-66 1211 91206 2.3 1.8409 1.6 0.1790 1.0 0.64 1061. 9.8 1060. 10.4 1057.1 24.6 1057.7 24.6 SMZ35-67 116 5928 1.9 1.8142 3.2 0.1690 1.0 0.33 1006.4 9.3 1050.2 21.3 1143.7 61.4 1143.8 61.4 SMZ35-68 201 5925 1.6 2.2126 11. 0.1803 2.3 0.21 1068.4 22.2 1185.6 80.8 1403.8 217. 1403.8 217. SMZ35-69 64 11298 1.0 5.2914 3.05 0.3307 1.0 0.30 1841.8 16.0 1867.0 25.7 1896.8 51.13 1896.3 51.13 3 7 5 3 200
SMZ35-70 125 12411 1.0 3.1526 1.6 0.2486 1.0 0.6 1431. 12.8 1445. 12.5 1466. 24.2 1466.4 24.2 SMZ35-71 471 14409 1.0 0.7705 3.3 0.0919 2.5 0.72 566.95 13.4 580.16 14.7 6314 .9 47.6 631.9 47.6 SMZ35-72 404 44697 2.3 4.4225 2.7 0.2912 1.0 0.35 1647. 14.5 1716. 22.5 1801. 45.8 1801.8 45.8 SMZ35-73 206 18972 1.3 2.7883 1.5 0.2245 1.0 0.67 1305.5 11.8 1352.6 11.0 1427.8 20.6 1427.1 20.6 SMZ35-74 174 12078 2.0 1.7978 2.5 0.1707 1.4 0.58 1016.6 13.3 1044.4 16.4 1104.1 41.6 1104.8 41.6 SMZ35-75 1164 39027 4.3 1.1849 6.9 0.1204 6.5 0.96 733.11 45.3 793.66 38.1 967.68 45.9 967.6 45.9 SMZ35-76 1438 40986 2.3 0.5826 1.6 0.0753 1.0 0.65 468.0 4.5 466.1 6.0 456.8 27.5 456.8 27.5 SMZ35-77 623 9591 4.1 0.5125 6.3 0.0512 6.2 0.93 322.1 19.3 420.1 21.7 1001. 27.2 1001.5 27.2 SMZ35-78 1503 61512 7.1 0.7851 2.0 0.0962 1.1 0.58 592.2 5.9 588.4 8.9 573.65 36.8 573.6 36.8 SMZ35-79 502 35904 2.3 1.7732 2.2 0.1750 1.0 0.43 1039. 9.6 1035. 14.2 1027. 39.2 1027.9 39.2 SMZ35-80 210 15747 1.3 1.5476 1.9 0.1576 1.5 0.76 943.34 13.0 949.57 11.8 963.99 24.8 963.9 24.8 SMZ35-81 153 29223 0.8 8.2361 1.9 0.4216 1.1 0.57 2267. 20.1 2257. 16.9 2247. 26.6 2247.7 26.6 SMZ35-82 744 28626 4.7 0.5989 3.0 0.0772 1.9 0.66 479.29 8.7 476.63 11.4 464.07 51.6 464.0 51.6 SMZ35-83 131 13119 1.6 1.9962 2.1 0.1899 1.0 0.43 1121. 10.3 1114. 13.9 1100. 35.8 1100.9 35.8 SMZ35-84 200 45159 3.0 6.2898 2.7 0.3545 2.5 0.99 1955.0 42.2 2017.2 23.7 2080.9 18.1 2080.2 18.1 SMZ35-86 225 26802 2.3 4.1448 1.7 0.2798 1.0 0.62 1590.9 14.1 1663.0 13.7 1756.2 24.5 1756.3 24.5 SMZ35-87 142 6612 1.4 0.9051 2.9 0.1023 1.1 0.30 628.04 6.3 654.52 14.0 746.63 57.2 746.6 57.2 SMZ35-88 383 18972 1.6 1.5356 3.4 0.1525 1.5 0.46 914.8 12.6 944.7 21.1 1015. 62.8 1015.2 62.8 SMZ35-89 476 5982 6.6 0.6114 11. 0.0565 9.2 0.83 354.2 31.7 484.5 42.4 1159.2 119. 1159.5 119. SMZ35-90 483 39861 1.5 1.9647 2.70 0.1880 1.0 0.34 1110. 10.2 1103. 18.2 1090.5 50.51 1090.0 50.51 SMZ35-91 381 38235 2.0 2.3472 3.2 0.2128 1.9 0.67 1243.3 21.5 1226.5 22.6 1196.0 50.3 1196.8 50.3 SMZ35-92 204 20307 1.8 2.0576 2.1 0.1947 1.0 0.40 1146.8 10.5 1134.7 14.3 1112.8 36.6 1112.3 36.6 SMZ35-94 148 10605 1.4 1.7773 2.9 0.1662 2.7 0.98 991.16 24.3 1037.8 18.6 1135.3 21.5 1135.6 21.5 SMZ35-95 168 16815 3.0 1.9197 2.6 0.1839 1.9 0.73 1088. 19.4 1088.2 17.6 1087.6 35.7 1087.6 35.7 SMZ35-96 280 37740 2.9 3.0456 3.1 0.2353 1.6 0.54 1362.1 20.0 1419.0 23.7 1505.6 49.7 1505.8 49.7 SMZ35-97 334 24546 8.1 1.0391 10. 0.1127 8.8 0.83 688.51 57.7 723.41 52.3 833.48 101. 833.4 101. SMZ35-98 107 11115 2.0 1.7581 3.21 0.1689 1.0 0.38 1006. 9.3 1030. 20.6 1081. 60.68 1081.4 60.68 SMZ35-99 164 7452 1.8 0.7496 2.7 0.0829 1.0 0.31 513.32 4.9 568.02 11.8 793.44 53.1 793.4 53.1 SMZ35-101 227 20322 1.9 1.6498 2.7 0.1660 1.0 0.37 990.2 9.2 989.5 17.3 987.9 51.7 987.9 51.7 SMZ35-102 501 36885 1.2 1.9555 2.6 0.1857 1.1 0.47 1098. 10.6 1100. 17.7 1104. 48.2 1104.5 48.2 SMZ35-103 1476 10913 7.2 1.4440 1.6 0.1482 1.0 0.60 891.02 8.3 907.43 9.4 947.45 24.8 947.4 24.8 SMZ35-105 855 490744 2.8 1.8512 1.9 0.1744 1.0 0.54 1036. 9.6 1063. 12.4 1120. 31.7 1120.5 31.7 SMZ35-106 309 18417 0.8 1.1828 1.8 0.1281 1.1 0.63 776.95 8.0 792.69 10.0 837.15 30.2 837.1 30.2 SMZ35-107 1011 34551 1.9 0.5832 1.7 0.0744 1.2 0.70 462.6 5.4 466.5 6.2 486.1 25.2 486.1 25.2 SMZ35-108 246 19890 1.7 1.6658 1.5 0.1645 1.0 0.63 981.7 9.1 995.6 9.6 1026. 23.0 1026.4 23.0 SMZ35-109 338 14526 1.7 1.5768 2.0 0.1556 1.0 0.56 932.0 8.7 961.1 12.4 1028.4 34.8 1028.3 34.8 SMZ35-110 361 14427 9.7 0.7705 7.7 0.0755 7.6 0.90 469.0 34.4 580.0 33.9 1042.3 20.4 1042.6 20.4 SMZ35-111 599 29667 3.0 1.3832 2.7 0.1350 2.6 0.99 816.5 19.6 881.8 16.1 1049.6 20.2 1049.5 20.2 SMZ35-113 515 45750 2.7 2.3738 4.9 0.1931 1.9 0.33 1138. 20.1 1234. 35.1 1407.5 86.6 1407.6 86.6 SMZ35-114 470 41310 2.1 2.4451 2.2 0.2159 1.0 0.49 1260.1 11.8 1256.8 15.6 1248.6 37.2 1248.7 37.2 SMZ35-115 481 44379 6.2 2.6114 1.8 0.2131 1.0 0.58 1245.2 11.6 1303.0 13.4 1401.7 29.1 1401.2 29.1 6 5 9 2 201
CHAPTER 4: CLIMATE-DRIVEN ENVIRONMENTAL CHANGE IN THE
SOUTHERN TIBETAN PLATEAU
ABSTRACT
Zhada basin is a large Neogene extensional sag basin in the Tethyan Himalaya of southwestern Tibet. In this paper we examine environmental changes in Zhada basin using sequence-, isotope- and litho-stratigraphy. Sequence stratigraphy reveals a long- term tectonic signal in the formation and filling of Zhada basin, as well as higher frequency cycles which we attribute to Milankovitch forcing. The record of
Milankovitch cycles in Zhada basin implies that global climate drove lake and wetland expansion and contraction in the southern Tibetan Plateau from the late Miocene to the
Pleistocene. Sequence stratigraphy shows that the Zhada basin evolved from an overfilled to underfilled basin but continued evolution was truncated by an abrupt return to fluvial conditions. Isotope stratigraphy shows distinct drying cycles; particularly during times when the basin was underfilled.
A long-term environmental change observed in Zhada basin involves a decrease in abundance of arboreal pollen in favor of non-arboreal pollen. The similarity between the long-term environmental changes in Zhada basin and those observed elsewhere on and around the Tibetan Plateau suggests that those changes are due to global or regional climate change rather than solely the result of uplift of the Tibetan Plateau. 202
INTRODUCTION
Uplift of the Tibetan Plateau, has long been viewed as a major forcing factor in regional and global climate change (e.g., Abe et al., 2005; An et al., 2001; France-Lanord and Derry, 1994; Molnar, 2005; Molnar et al., 1993; Raymo and Ruddiman, 1992;
Ruddiman et al., 1997). Uplift is also thought to have directly driven environmental change on the Tibetan Plateau (e.g., Liu, 1980; Wang et al., 2006; Zhang et al., 1981; Zhu et al., 2004). However, recent work suggests that global climate change drives climate and environmental change on the Tibetan Plateau (e.g., Dupont-Nivet et al., 2007).
These new studies call into question the direct link between uplift and environmental change on the Tibetan Plateau. Moreover, uplift histories of the Tibetan Plateau based on faunal or floral associations differ significantly from those based on stable isotope and other quantitative paleoelevation studies. Paleo-floral assemblages from Pleistocene deposits on the Tibetan Plateau are consistent with modern floral assemblages at low elevations (e.g., Axelrod, 1981; Li and Zhou, 2001a, b; Meng et al., 2004; Molnar, 2005;
Wang et al., 2006; Xu, 1981; Zhang et al., 1981) and are used to argue for recent uplift of the Tibetan Plateau. A similar argument is based on the abundance of mammal mega- fauna on the Tibetan Plateau in the late Miocene – Pliocene and their relative paucity now (e.g., Cao et al., 1981; Li and Li, 1990; Meng et al., 2004; Wang et al., 2008c; Zhang et al., 1981). In contrast, other lines of evidence indicate that the southern Tibetan
Plateau has been at high elevations since at least the mid-Miocene (Currie et al., 2005;
Garzione et al., 2000a; Rowley et al., 2001; Spicer et al., 2003) and central Tibetan 203
Plateau since at least the Oligocene (Cyr et al., 2005; DeCelles et al., 2007; Dupont-Nivet et al., in press; Graham et al., 2005; Rowley and Currie, 2006).
The environmental effects of tectonics and climate change can best be addressed in basins that contain all of the proxies mentioned above: pollen, leaf fossils, mammal fossils, and carbonates used in stable isotope studies. A case in point is the Zhada basin in southwestern Tibet. However, a lack of coherent, comprehensive basin analysis integrating all the paleoenvironmental proxies has hampered efforts to untangle the climatic and tectonic signals in the Zhada record. The Zhada Formation is described as both upward-fining (Li and Zhou, 2001b; Zhang et al., 1981; Zhou et al., 2000) and capped by boulder conglomerates (Zhu et al., 2007; Zhu et al., 2004). There is similarly little consensus regarding the basin’s tectonic origin. The Zhada basin is presented as having developed as a supradetachment basin above the South Tibetan Detachment system (Wang et al., 2004), as a flexural basin responding to arc-perpendicular compression (Zhou et al., 2000), or as a half-graben produced by arc-perpendicular rifting (Wang et al., 2008a) which was followed by uplift (Zhu et al., 2004). Until recently, the Zhada basin was understood to have been at low elevations until as late as the Pleistocene (e.g., Li and Zhou, 2001a; Zhang et al., 1981; Zhou et al., 2000; Zhu et al., 2004).
In several recent papers (Saylor et al., in review; Saylor et al., in press) we have documented the chronostratigraphy and geodynamic mechanism of formation of Zhada basin. Here we provide basin-wide lithologic and sequence stratigraphic correlations, frequency analysis of the record of environmental change, and a detailed isotope 204 stratigraphy. Our results suggest that global climate change, possibly in conjunction with regional climate change, controlled environmental variability in the southwestern Tibetan
Plateau during the late Miocene - Pleistocene. The data also point to the possibility of establishing a high-resolution climate record for this high-elevation basin extending from the Pleistocene to the Miocene. Finally, paleo-environmental data are used to address the sharply differing uplift histories proposed for the southern Tibetan Plateau.
205
REGIONAL GEOLOGICAL SETTING
The Zhada basin is the largest late Cenozoic sedimentary basin in the Himalaya.
It is located just north of the high Himalayan ridge crest in the western part of the orogen
(~32° N, 82° E, Figure 4.1A). The basin measures at least 150 km long and 60 km wide and the current outcrop extent of the basin fill is at least 9,000 km2 (Figure 4.1B).
The Zhada basin is located in a zone of active arc-parallel extension (Murphy et al., 2002; Ni and Barazangi, 1985; Thiede et al., 2006; Valli et al., 2007; Zhang et al.,
2000). It is bounded by the South Tibetan Detachment system (STDS) to the southwest, the Indus suture to the northeast, and the Leo Pargil and Gurla Mandhata gneiss domes to the northwest and southeast, respectively (Figure 4.1B). The STDS is a series of north- dipping, low-angle, top-to-the-north normal faults that place low-grade metasedimentary rocks of the Tethyan sequence on high-grade gneisses and granites of the Greater
Himalayan sequence. Along strike, ages for movement on the STDS range from 21 – 12
Ma (Cottle et al., 2007; Hodges et al., 1996; Hodges et al., 1992; Murphy and Yin, 2003;
Murphy and Harrison, 1999; Searle and Godin, 2003; Searle et al., 1997). To the northeast of the Zhada basin the Oligo-Miocene Great Counter Thrust, a south-dipping, top-to-the-north thrust system, cuts the Indus Suture (e.g., Ganser, 1964; Murphy and
Yin, 2003; Yin et al., 1999). Exhumation of the Leo Pargil and Gurla Mandhata gneiss domes (Figure 4.1B) by normal faulting began 9-10 Ma (Murphy et al., 2002; Saylor et al., in review; Thiede et al., 2006; Zhang et al., 2000) and continues today.
The Zhada Formation fills the Zhada basin and consists of > 800 m of fluvial, lacustrine, eolian and alluvial fan deposits. The sedimentary basin fill is undisturbed and 206 forms an angular or buttress unconformity with underlying Tethyan sequence strata that were previously shortened in the Himalayan fold-thrust belt (Saylor et al., in review).
The Zhada Formation is capped by a geomorphic surface that is extends across the basin and is interpreted as a paleo-depositional plain that marks the maximum extent of sedimentation prior to integration of the modern Sutlej River drainage network. After deposition, the basin was incised to basement by the Sutlej River, exposing the entire basin fill. The best estimate for the age of the Zhada Formation is between ~ 9.2 and < 1
Ma based on vertebrate fossils and magnetostratigraphy (Figure 4.2)(Lourens et al., 2004;
Saylor et al., in press; Wang et al., 2008b).
207
METHODS
Sedimentology
We measured 14 stratigraphic sections spanning the basin extent from the Zhada county seat in the southeast to the Leo Pargil Range front in the northwest (Figure 4.1B).
Sections were measured at centimeter scale.
Correlations
The geomorphic surface which caps the Zhada Formation, being correlative across the basin, provides the datum for sequence stratigraphic and lithologic correlation.
Correlations are based on major stratigraphic members that can be physically traced
(Saylor et al., in review). Magnetostratigraphy linking the South Zhada, Southeast
Zhada and East Zhada sections provides additional constraints. A final independent constraint is the switch from exclusively C3 to mixed C3 and C4 vegetation which is observed between 130 and 230 m in the South Zhada section and at ~ 300 m in the East
Zhada section (Saylor et al., in press). The expansion of C4 vegetation is observed across the Indian subcontinent and southern Tibet at ~ 7 Ma (France-Lanord and Derry, 1994;
Garzione et al., 2000a; Ojha et al., 2000; Quade et al., 1995; Quade et al., 1989; Wang et al., 2006).
Frequency analysis of Zhada Formation cycles
The sedimentological record of the Zhada Formation archives the cyclical expansion and contraction of a large paleolake. Frequency analysis was conducted by 208 spectral analysis and also by calculation of the average duration of cycles. In order to apply spectral analysis to this record, a waveform was created by assigning numerical values to each of the depositional environments as follows: fluvial and alluvial fan associations, 5; supra-littoral associations, 4; littoral associations, 3; profundal associations, 2 or 1 based on the presence or absence of terrestrial clastic or plant material, respectively. Depositional environments in the South Zhada measured section were identified at 0.5 m increments or where the depositional environment changed. The series was converted from the depth domain to the time domain by linear interpolation between magnetostratgraphic tie points, justified by the generally linear subsidence/sediment accumulation rates (Saylor et al., in review). The result is a clipped waveform with uneven sample spacing and temporal resolution better than 4,000 yrs
(Figure 4.3, Table 4.1). Progradation of basin margin depositional environments leads to waveform saturation and loss of resolution at ages < 3.3 Ma. In order to evaluate the effect of this saturation on spectral analysis, both the 5.23 – 2.581 Ma and the 5.23 – 3.3
Ma intervals were analyzed (labeled ―Entire Series‖ and ―Short Series‖ in Figure 4.3, respectively).
The Lomb-Scargle Fourier transform method was applied using the SPECTRUM program which allows analysis of unevenly spaced time series without interpolation
(Schulz and Stattegger, 1997). We conducted univariate spectral analysis (Welch method), and harmonic analysis to determine the dominant frequencies in the record.
Cross-spectral analysis was used to determine the coherence between the Zhada record and the record of summer insolation for 65°N (Laskar et al., 2004). 209
Stable Isotopes
Stable isotopes of oxygen and carbon (expressed as δ18O and δ13C in units ‰, respectively, and referenced to Vienna PeeDee Belemnite (VPDB) or Vienna Standard
Mean Ocean Water (VSMOW)) are a sensitive indicator of hydrologic conditions. The
18 18 principal controls on surface water δ O (δ Osw) values in southern Tibet are increasing
18 18 elevation (which decreases δ Osw values) and evaporation (which increases δ Osw values) (Dansgaard, 1954; Dansgaard, 1964; Garzione et al., 2000b; Poage and
Chamberlain, 2001; Rowley and Garzione, 2007; Rowley et al., 2001; Rozanski et al.,
18 1993). Freshwater gastropods precipitate shells with oxygen-isotopic ratios (δ Occ) in equilibrium with ambient water, dependent on the temperature-dependent fractionation factor (Fritz and Poplawski, 1974; Leng et al., 1999) between aragonite and water. The
13 13 13 δ C values of gastropod shells (δ Ccc) are controlled by the δ C value of dissolved
13 inorganic carbon (δ CDIC) in the ambient water (Bonadonna et al., 1999; Lemeille et al.,
13 1983; Leng et al., 1999). The δ CDIC value is controlled primarily by the residence time of water and secondarily by factors including the local vegetation and substrate. The
13 δ CDIC value of surface water is increased by photosynthesis or equilibration with the atmosphere (Li and Ku, 1997; Talbot, 1990). Particularly in productive lakes, increased
13 13 18 water residence time increases the δ CDIC value. Thus, both δ Ccc and δ Occ values of gastropod shells are useful in reconstructing paleo-hydrologic and paleo-environmental conditions (e.g., Abell and Williams, 1989; Hailemichael et al., 2002; Purton and Brasier,
1997; Smith et al., 2004). 210
Fossil gastropod shell fragments and intact shells were collected from fluvial, marshy, and lacustrine intervals from the lower ~ 650 m in two measured sections.
Shells were powdered and homogenized prior to analysis. To check for preservation of biogenic aragonite, 12 representative gastropod samples from fluvial, lacustrine and marshy intervals were powdered and analyzed using the University of Arizona’s D8
Advance Bruker X-ray powder diffractometer (Saylor et al., in press).
18 13 We measured δ Occ and δ Ccc values using an automated carbonate preparation device (KIEL-III) coupled to a gas-ratio mass spectrometer (Finnigan MAT 252).
Powdered samples were reacted with dehydrated phosphoric acid under vacuum at 70°C.
The isotope ratio measurement is calibrated based on repeated measurements of NBS-19 and NBS-18 and precision is ± 0.1 ‰ for δ18O and ±0.06‰ for δ13C (1 ).
211
RESULTS
Sedimentology
We identify 14 lithofacies associations and five depositional-environment associations based on lithology, texture and sedimentary structures (Table 4.2). Unless otherwise indicated, all deposits are laterally continuous for 100’s of meters to several kilometers. Only abbreviated descriptions and interpretations are presented here; for details see chapter 2.
Depositional Cycles in the Zhada Formation
Deposits in the Zhada Formation occur in two types of cycles that mark periods of lake or wetland expansion and contraction. The bulk of a typical Type-A cycle (Figures
4.4A and 4.5A) consists of a 1 – 10 m thick unit of fluvial or alluvial fan sandstone or conglomerate unit (lithofacies association F1 or rarely A1-A4) with an erosional base, no grain-size trend and a capping, upward-fining sandstone bed (lithofacies association F2 or occasionally S1). This is overlain by an organic-rich, fine-grained unit that contains convoluted bedding (lithofacies association F3).
An idealized Type-B cycle (Figures 4.4B and 4.5B, C) is characterized by an upward coarsening succession of, in ascending order, fossil-rich siltstone (lithofacies association L1), laminated or massive siltstone or sandy turbidites (lithofacies association
P1-P2), rippled and cross-stratified sandstone (lithofacies association L2), sandstone containing planar, trough or climbing-ripple cross-stratification (lithofacies association
F2 or S1-S3) and conglomerate beds (lithofacies associations A1-A4 or F1). The 212 uppermost sandstone beds have both erosional and gradational basal surfaces. The basal surface of the capping conglomeratic unit is either erosional or marked by soft-sediment deformation. Organic-rich convoluted siltstone (lithofacies association F3) can occur at any point within the capping sandstone or conglomerate succession. In all cases, the boundary between the fluvial or alluvial fan association and littoral or profundal association is abrupt while the transition from the profundal association to the fluvial or alluvial fan association is gradational, indicating a rapid transgression followed by gradual progradation. Parts of both Type-A and -B cycles may be missing from the idealized version depicted in Figure 4.4.
Correlations
Type-A and -B cycles stack in predictable patterns within a larger sequence stratigraphic hierarchy (Figure 4.6). Because of the difficulty of establishing a hierarchy of continental sequences based on sequence duration as determined in marine sequences
(e.g., Vail et al., 1991), we follow Catuneanu (2006) and establish a unique hierarchy for
Zhada basin. The Zhada Formation does not have significant intraformational unconformities which might represent extended periods of non-deposition or extensive sub-aerial exposure and erosion. However, it does have unconformities that represent rapid progradation of basin margin facies and occasionally non-deposition of a lithofacies association. It is on the basis of these minor unconformities and associated shifts in depositional environments that we define sequences of all orders. 213
At the finest scale, 56 Type-A and –B cycles are present in the Zhada Formation
(Figure 4.7). Four second order sequences are evident above the cycles described above.
Nomenclature used identifies sequence order, systems tract or bounding surface, and stratigraphic position from lowest to highest (hence 2HST2 is the second order highstand systems tract second from the base of the Zhada Formation). Second order lowstand systems tracts (2LST-) are characterized by Type-A cycles arranged in a retrogradational stacking pattern (Figure 4.6). They are fluvially dominated and become increasingly marshy upsection. Second order transgressive surfaces (2TS-) are identified by an abrupt transition to thick, profundal claystone (Figure 4.8). Modern Tibetan lakes are typically broad, shallow, and occur on low-relief plains. The lateral continuity of depositional units implies that these conditions also existed during deposition of the Zhada Formation.
When transgression occurred, it would have quickly flooded the depositional plain resulting in rapid retrogradation. As a result, second order transgressive systems tracts
(2TST-) are thin. They are characterized by Type-B cycles arranged in a retrogradational stacking pattern and are capped by widespread profundal lacustrine sedimentation.
Second order highstand systems tracts (2HST-) are characterized by Type-B cycles arranged in prograding or aggrading stacking patterns. At the coarsest scale, the entire
Zhada Formation can be seen as a first-order sequence (~ third order sequence of Vail et al., 1977). 1LST is below the first major lacustrine transgression and is composed of
2LST1 and 2TST1. 1TST occurs between the first major lacustrine transgression and the most widespread profundal lacustrine sedimentation (maximum flooding surface) and is composed of 2HST1, 2LST2, and 2TST2. 1HST occurs between the most widespread 214 maximum flooding surface and the top of the Zhada Formation and is composed of
2HST2, 2LST3 - 2HST3, and 2LST4 – 2HST4.
Type-A and –B cycles can be correlated from stratigraphic sections spanning the entire thickness of the Zhada Formation (South Zhada and Guga sections) toward the basin margins. Sediment accumulation was greatest in the region of the South Zhada and
Guga sections. However, the maximum thicknesses of fine-grained material were deposited to the northwest of there, in the region of the Namru Road West section. The implication is that, though subsidence was greatest in the region of the South Zhada and
Guga sections, these were also close to the source of coarse-grained material (identified by Saylor et al. (in review) as both the Kailash region to the north of the basin and also the mountain ranges immediately surrounding the basin).
Frequency analysis of Zhada Formation cycles
The best time control based on magnetostratigraphy in the Zhada basin is between chrons 2An (2.581 Ma) and 3n (5.23 Ma)(Lourens et al., 2004). Twenty-eight Type-B cycles occur within this interval, each with an average duration of 95 kyr. Spectral analysis of both the entire series and the 5.23 - 3.3 interval indicates statistically significant peaks at 91.7 kyr at the 95% confidence level and at 22.4 kyr at the 85% confidence level (Figure 4.9A). Harmonic analysis of the entire series reveals peaks at
91.7 ± 2, 126 ± 4, 140 ± 4, 221 ± 12, 379 ± 40, 662 ± 287, and 1330 ± 2000 kyr at the 99
% confidence level (Figure 4.9B). However, in the analysis of the 5.23 – 3.3 Ma interval all of these peaks except for the 379 and 91.7 kyr peaks are suppressed (Figure 4.9C). 215
This indicates that the suppressed peaks are likely the result of red noise due to waveform saturation at ages < 3.3 Ma. Coherence analysis of the shorter interval also reveals peaks at 80 ± 13, 26 ± 1, and 18.9 ± 0.6 kyr (Figure 4.9D).
Stable Isotopes
X-ray diffraction analysis from 11 of 12 samples yielded only aragonite peaks
18 (Saylor et al., in press). The twelfth sample was too small to yield results. The δ Occ values of samples that we analyzed using X-ray diffraction ranged from -20.3 to +0.2 ‰
(VPDB)
Clearly identifiable trends in multiple cycles were found only in the densely sampled South Zhada section, particularly in the 250 – 470 m interval of the South Zhada section where we focus our discussion. For analysis of the entire data set see Saylor et al.
13 (in press). δ Ccc values of gastropods in this interval range from –3.3 to +2.1‰ (VPDB)
18 and δ Occ values from -13.7 to +0.7‰ (VPDB, Table 4.3).
Seventeen Type-B cycles occur within the 250 – 470 m interval of the South
Zhada Section (Figure 4.10). Of those, eight had sufficient sampling densities that trends
18 18 in δ Occ values should be evident. Five cycles show a clear trend of increasing δ Occ values with stratigraphic height above the cycle boundary (Figure 4.10). One additional cycle shows a similar, but muted, trend (Figure 4.10). The final two cycles do not show
18 any trend in δ Occ values (Figure 4.10). 216
INTERPRETATION OF ZHADA FORMATION CYCLES
Zhada Formation Type-A and –B cycles are best interpreted as parasequences.
Parasequences are typically thin (<20 m) and correspondingly short lived (~100 kyr). We conclude that facies are controlled primarily by lake or wetland expansion and contraction which are related by the interplay of sedimentation and base-level change at the shoreline. This is most evident in Type-B parasequences where flooding surfaces are easily identifiable as the sharp basal contact of the fine-grained, fossil-rich, often papery interval capping a coarser grained unit (Figure 4.4B). In Type-A parasequences flooding is probably recorded by the transition from the fluvial association to marshy deposits of the supra-littoral association rather than by an abrupt surface as in Type-B parasequences
(Figure 4.4A). However, Type-A parasequences have clearly identifiable erosive surfaces which can be correlated to sub-aerial exposure surfaces in Type-B parasequences (Figures 4.4, 4.5, 4.6). Thus, the maximum regressive surface in both
Type-A and -B parasequences is defined as the erosional surface at the base of the coarsest grained interval, if an erosional surface is present, or at the base of the lowest sandy interval showing signs of unidirectional traction transport if no erosional surface is present.
Type-A parasequences occur at the base of Zhada Formation sequences (Figure 4.
6). Marshy deposits become more prominent components of Type-A parasequences higher in the sequences consistent with the general retrogradational stacking pattern. The upward-fining textural trend, retrogradational stacking pattern and location at the base of the Zhada Formation sequences suggest that Type-A parasequences represent onset of 217 lacustrine transgression. The associated rise in the water table resulted in increased marshy conditions, although the system was still dominated by fluvial processes (e.g.,
Bohacs et al., 2000).
Type-B parasequences occur in the middle to upper Zhada Formation (Figure 4.6) and coarsen upward from a profundal lacustrine lithofacies association to a supra-littoral or fluvial lithofacies association. Thus, they represent progradational parasequences in a lacustrine setting. The persistence of these cycles to the top of the Zhada Formation indicates that lacustrine conditions prevailed until the onset of incision by the modern
Sutlej River despite progradation causing replacement of the fine-grained littoral or supra-littoral deposits by basin-margin alluvial fans.
Zhada Formation cycles obey Walther’s Law. Within individual cycles, facies that are superposed occurred side-by-side spatially (e.g. Middleton, 1973; Posamentier and Allen, 1999). This is consistent with sequence stratigraphy theory (Van Wagoner et al., 1988) but contrasts with reports of non-Waltherian cycles from the Green River
Formation and underfilled lacustrine basins in the Qaidam basin and Death Valley
(Lowenstein et al., 1998; Pietras and Carroll, 2006; Yang et al., 1995).
218
DISCUSSION
Sequence Stratigraphic and Lithostratigraphic Correlations
The overfilled, balanced-fill and underfilled intervals of the Zhada basin were delineated using definitions modified from Bohacs et al. (2000). In contrast to the evaporative facies association presented by Bohacs et al. (2000) as typical of underfilled lake basins, evaporites are present, though not dominant within the Zhada sections. It may be argued that no sections were measured in the basin center and so the possibility exists that that is the locus of evaporite deposition. However, that is unlikely given the lateral facies continuity in the Zhada Formation and the number of measured sections close to the basin center. A more plausible explanation is that discharge by the paleo-
Sutlej River was consistently large relative to basin volume and that the lake rarely desiccated (e.g.: Lake Naivasha, Barton et al., 1987; Duhnforth et al., 2006).
The overfilled interval was determined based on the prevalence of fluvial input, indistinctly expressed parasequences (Bohacs et al., 2000), and the dominance of sedimentary structures indicating traction transport. The overfilled interval extends from
18 the base of the section to 1TS (which is the same surface as 2TS1, Figure 4.7). δ Occ values from this interval are extremely negative due to the low water-residence times associated with river throughflow (Saylor et al., in press).
The balanced-fill interval is identified by a dominantly retrogradational parasequence stacking pattern. The balanced-fill interval is characterized primarily by the rising water table inferred from the increased prevalence of marshy intervals. Though the basin was intermittently open, fluvial influx was greater than efflux via outflow and 219 evaporation and so the basin was being slowly drowned. The balanced fill interval
18 extends from 1TS to 2MFS1 (Figure 4.7). The trend towards more positive δ Occ values in this interval and the inferred increase in water residence times (Saylor et al., in press) are consistent with this interpretation.
The underfilled interval is well represented in the Zhada Formation and was identified based on the occurrence of well-expressed flooding surfaces that separate distinct lithologies. Parasequences are well developed and record a combination of progradational and aggradational stacking patterns. Depositional geometries (flooding surfaces) are generally parallel or sub-parallel and well-expressed parasequences converge and become indistinct towards the basin center. Within parasequences, transgressive deposits are thin (< 0.5 m) or absent, whereas progradational deposits are thick, well-developed, and dominated by traction transport (oscillatory current ripples, climbing ripples). The underfilled interval extends from 2MFS1 to the paleo-depositional surface.
Type-B parasequences occur primarily in the underfilled portion of the Zhada basin. However, they differ from previous descriptions of underfilled basin lithofacies
(e.g., Bohacs et al., 2000; Carroll, 1998). The primary difference is that coarse-grained facies are presented as the result of transgression by Bohacs et al. (2000) and Carroll
(1998), whereas in Zhada basin they typically constitute the regressive portion of the parasequnce. There are several reasons for interpreting coarse-grained facies as the regressive part of the cycle in Zhada basin. Unlike the cycles presented by Bohacs et al.
(2000) and Carroll (1998), fine-grained, sub-aerial exposure surfaces do not directly 220 underlie the coarse-grained facies. Rather, the profundal lacustrine facies coarsen upwards gradually and shows evidence of traction transport, including oscillatory-current ripples, throughout regression. The coarse-grained facies exhibit evidence of sub-aerial exposure including preferential weathering and cementation, and root traces.
Additionally, the coarse-grained facies are often interbedded with organic-rich siltstone and sandstone facies (lithofacies association F3) indicative of marshy wetlands such as might occur on lake margins or between fluvial channels. We therefore interpret the coarse-grained facies as the maximum progradation of lake-margin depositional environments (Figures 4.4C and D, panel I). One possible explanation for the difference between Type-B cycles and those in the basins studied by Bohacs et al. (2000) and
Carroll (1998) is that fluctuations in influx were not as great in Zhada basin as and that the Zhada basin rarely desiccated. If water, and thus sediment, influx were relatively stable, regression would be marked by progradation and during maximum regression, which marks the time when the lake has the smallest volume and is the most restricted, the relative influence of fluvial input would be greatest.
The evolution of Zhada basin followed a typical pattern from a fluvial system to an underfilled lacustrine basin (Figure 4.11)(Bohacs et al., 2000). However, the top of the Zhada formation is dominated by coarse-grained, basin-margin equivalents of Type-B sequences. There is no change in large-scale sedimentary environment indicated prior to an abrupt truncation of the Zhada Formation by a paleo-depositional plain. By implication, there was no return to a balanced-fill or overfilled basin type. The return to 221 fluvial conditions often observed was discontinuous in that it bypassed the balanced-fill and overfilled intervals (Figure 4.11).
Frequency analysis
The two independent time-series analyses above indicate that ~ 100 kyr cycles are present in the Zhada Formation. In addition to a peak at 91.7 kyr, spectral analysis reveals a peak at 22 kyr. These are within 1/2 bandwidth (6 dB bandwidth = 2.4) of the eccentricity and precession frequencies. It is possible that the 100 kyr signal is the result of clipping of a 20 kyr precession signal (Figure 4.3)(e.g., Weedon, 2003 and references therein). However, in either case climate change related to orbital cyclicity has been recorded in environmental change on the Tibetan Plateau.
Harmonic analysis does not reveal the 22 kyr peak indicated by univariate analysis but does show peaks at 91.7 and 379 kyr, both of which are consistent with the eccentricity cycle (Figures 4.9B and C). Finally, coherence analysis shows both eccentricity and precession frequencies (Figure 4.9D).
Second-order sequences in the Zhada Formation are of ambiguous origin, but parasequences are consistent in duration with insolation-driven climate changes (fourth order sequences of Vail et al., 1977) due to changes in the orbital characteristics of the earth (i.e., Milankovitch cycles). If parasequences are representative of Milankovitch cycles, the driving process behind environmental cyclicity in the Zhada basin was not tectonics. Rather, lacustrine expansion and contraction was caused by a change in the precipitation to evaporation ratio linked to strengthening or weakening of the monsoon 222 due to (respectively) increases or decreases in insolation (Gupta et al., 2001; Shi et al.,
2001; Thompson et al., 2006). It is not surprising that climatically driven sequences are most distinctly expressed in the underfilled interval of the Zhada Formation because during this interval the lake would be most susceptible to changes in hydrology (Bohacs et al., 2000; Kelly, 1993).
Isotopes in Zhada Formation cycles
Lakes respond to changes in hydrology on much shorter time-scales than do oceans because they have much smaller water and sediment volumes (see Bohacs et al.,
2000; Kelts, 1988; Sladen, 1994). Additionally, in lacustrine settings the relative proportion of water influx and efflux (usually climatically driven) and movement on faults (tectonically driven) are both primary controllers of systems tracts. Finally, sediment supply is linked to water influx. This creates the paradoxical situation where the influx of water and lake volume can be high, and yet lake volume can be decreasing
(net evaporation > net influx, Figures 4.4C and D).
Water and sediment influx are thus decoupled from base-level changes but are a primary control of shoreline trajectory and therefore on parasequence evolution. As mentioned above, lithofacies distribution and thus lithologic stacking patterns appear to be controlled primarily by the location of the shoreline and so are also decoupled from base-level. This means that parasequence flooding surfaces correspond to lake expansion
18 due to a drop in Evaporation/Precipitation. Thus, the lowest δ Occ values of aquatic gastropods and, implicitly, of the lake water, are found at the flooding surface even 223 though the coarsest material is associated with maximum regression (Figure 4.12).
Particularly when the basin was underfilled, the highest values occur at the time of maximum regression (Figures 4.4D and 4.10). This apparent discrepancy can be accounted for by understanding that though water and sediment influx were both relatively high and stable, climatically driven Evaporation/Precipitation controlled lake
18 level and thus the δ Osw value of lake water. When efflux was greater than influx, the
18 δ Osw value increased, the lake shrank, and the coarse grained material was carried further into the basin (Figures 4.4C, panel I). Conversely, when influx was greater than
18 efflux, the δ Osw value decreased, the lake grew, and the coarse grained material was trapped at the basin margins (Figures 4.4C, panel II).
13 18 The foregoing discussion indicates that the primary control of δ Csw and δ Osw values was volume-weighted average water residence time. Just prior to flooding, when
13 18 lake volume was small, the average water residence time, and hence δ Csw and δ Osw values, was significantly altered by addition of a small volume of water. On the other hand, after significant flooding, the lake was sufficiently large and the water sufficiently evolved that the continued input of water during flooding had only a minor effect on average water residence time. Though the discussion above refers primarily to individual parasequences, the effect may span several parasequences and point to climatic control at multiple frequencies (Figure 4.10).
18 The correlation between low δ Osw values and flooding described above is confirmed in the modern analog of Kungyu Co. Water samples collected on 25 July,
2006 from the lake and from the sole river flowing into the lake had δ18O values of -14.8 224 and -15.6 ‰ (VSMOW), respectively. Stranded shorelines with aquatic grasses and evaporites on the lake margins showed that the lake was recently at higher levels. The samples were collected at the start of the monsoon season and the interpretation is that the lake level had fallen to extremely low levels and was now in the process of refilling
(Figure 4.4D: black star denotes the interpreted location of Kungyu Co within the filling/emptying cycle at the time of sampling).
Basin history
Combining the observations made above with previous studies (Saylor et al., in review; Saylor et al., in press) points to the following basin history. Through arc-parallel extension a sill was created which caused ponding of the river, leading to deposition of the lowest strata of the Zhada Formation. The accumulating sediment onlapped the pre- existing Tethyan Sequence topography, forming the observed buttress or angular unconformities. The ancestral Sutlej River continued to flow from its source, increasing the sediment pile. The exhumation rate of the Leo Pargil/Qusum range to the northwest of the Zhada basin between 10 and 5.6 Ma is the same as the sediment accumulation rate in the Zhada basin (Saylor et al., in review; Thiede et al., 2006), indicating that the uplifting range may have acted as a sill. After 5.6 Ma both the exhumation rate and the sediment accumulation rate increased, the basin became closed, and lacustrine sedimentation commenced. These conditions continued, despite progradation of basin- margin alluvial fans, until a new sill was eventually breached at < 1 Ma. At this point, the system abruptly returned to fluvial conditions and began incising through the Zhada 225
Formation. The sudden return to fluvial conditions via the integration of the modern
Sutlej River system truncated the typical basin evolution pattern described by Bohacs et al. (2000).
Global climate change and its impact on the southern Tibetan Plateau
Numerous authors have reported 100 and 400 kyr cycles in the Miocene (Di
Celma and Cantalamessa, 2007; Holbourn et al., 2007; Kashiwaya et al., 2001; Van
Wagoner et al., 1988; Zachos et al., 2001), although none from high elevations such as the Tibetan Plateau. The Zhada Basin therefore presents an excellent opportunity to study high-frequency climatically driven environmental change at high-elevations in the
Miocene - Pleistocene. Expansion and contraction of lakes and wetlands has been linked to variability in the strength of the Asian monsoon (Shi et al., 2001). The Quaternary
Asian monsoon is thought to be modulated by orbital cyclicity (Clemens et al., 1991; Jian et al., 2001; Nie et al., 2008; Prell and Kutzbach, 1992; Wang et al., 2005; Wang et al.,
2008d) though there is disagreement about which frequencies are dominant (Clemens and
Prell, 2003; Nakagawa et al., 2008). Data from this study support previous work indicating that the monsoon has long varied at precessional frequencies (Bloemendal and
Demenocal, 1989). Our data also show enivronmental variation at eccentricity frequencies (Dupont-Nivet et al., 2007).
We turn next to another challenge presented by the Zhada basin: the explanation of the floral and faunal changes observed within the Zhada Formation and between the late Miocene and the present. The Zhada basin contained a host of plants that are 226 typically thought of as native to warm, humid, and, by implication, low-elevation climates (Li and Zhou, 2001a, b; Zhu et al., 2007; Zhu et al., 2004). Additionally, a broad cross-section of mammal mega-fauna lived in Zhada including Hipparion zandaense, Nyctereutes, Palaeotragus microdon and rhinoceri that have variously been identified as Hyracodon or Dicerorhinus (Li and Li, 1990; Liu, 1981; Meng et al., 2004;
Zhang et al., 1981; X. Wang, pers. comm.; E. Lindsay, pers. comm.). This is in striking contrast to the basin today, in which the only large mammalian fauna are the kiang
(Tibetan wild asses) and extremely rare chiru (small, long-horned antelope). However, oxygen isotope analysis points to high elevations and a climate which was cold and arid; very similar to the modern (Saylor et al., in press).
We compiled published pollen data from several measured sections around the
Zhada basin and correlated them with the South Zhada measured section. In the following discussion, stratigraphic heights and ages are based on the South Zhada section. The three lowermost sections come from the region of the Guga and South
Zhada sections (Yu et al., 2007; Zhu et al., 2007). Two additional sections are from the region of the Namru Road West section and span the uppermost ~250 m of the Zhada
Formation (Zhang et al., 1981; Zhu et al., 2006). Due to differences in data presentation, a precise correlation of the stratigraphy presented by Zhang et al. (1981) to the Namru
Road West section is not possible. Zhang et al. (1981), Zhu et al. (2006, 2007), and Yu et al. (2007) note an increase in grass and shrub pollen and a decrease in arboreal pollen which begins at ~ 170 – 230 m and culminates at ~ 630 m (Zhu et al., 2007). The culmination is marked by the replacement of spruce and fir pollen with shrub between 227
~500 – 630m. This places the onset of the transition at ~ 7.2 – 6 Ma and its end at 3.6 -
2.6 Ma based on magnetostratigraphy (Figure 4.2) (Saylor et al., in press).
The transition from arboreal to non-arboreal dominated pollen associations in the
Zhada Formation has long been interpreted as indicating substantial cooling and drying due to recent, rapid uplift of the southwestern Tibetan Plateau (Li and Zhou, 2001a, b;
Meng et al., 2004; Zhang et al., 1981). However, this same floral turnover was observed in the low-elevation Gangetic foreland deposits of Nepal and northern India (the Siwalik group, e.g., Awashi and Prasad, 1989; Hoorn et al., 2000; Mathur, 1984; Prasad, 1993;
Sarkar, 1989). Quade et al. (1995) and Hoorn et al. (2000) concluded that the decline in arboreal species and increased prominence of grasses was part of the regional shift from
13 C3 to C4 dominated floral populations recorded by a regional increase in the δ Ccc values
13 of paleosol carbonates in northern India and Pakistan. The increase in δ Ccc values has been observed across the northern Indian subcontinent (Cerling et al., 1997; Freeman and
Collarusso, 2001; Quade et al., 1995; Quade et al., 1989), in the Bengal fan (France-
Lanord and Derry, 1994), in the southern Tibetan Plateau (Garzione et al., 2000a; Wang et al., 2006; Yoshida et al., 1984), and in the northern Tibetan Plateau (Ma et al., 1998).
Significantly, it has also been observed in Zhada basin (Saylor et al., in press) and occurs synchronously, within the sampling resolution, with the onset of the transition to non- arboreally dominated pollen assemblages. The expansion of C4 plants in the Zhada basin thus appears to be related to a global phenomenon and points to a global climate change, rather than local or even regional uplift (Cerling et al., 1997; Fox and Koch, 2003;
Freeman and Collarusso, 2001; Latorre et al., 1997; Pagani et al., 1999). In the low- 228 elevation Siwalik group, the change in habitat from forest to open grasslands and savannas was accompanied by a major mega-faunal turnover (Barry et al., 1990; Barry et al., 1995; Barry et al., 1991; Flynn et al., 1995; Flynn et al., 1998; Patnaik, 2003; Pilbeam et al., 1996).
The recognition of Milankovitch cycles in the Zhada Formation indicates that insolation driven global or regional climate change drove environmental changes in basins at high elevations on the southern Tibetan Plateau. Thus, we can reasonably expect that floral and faunal communities on the Tibetan Plateau would have responded to global climate change. The shift from forest to grassland observed in the Zhada basin was not the result of basin uplift, because an identical change is observed in low- elevation deposits in nearby northern India. Further, analysis of oxygen isotopes from aquatic gastropod shells from the Zhada Formation indicates a probable decrease in elevation of the basin since the late Miocene (Saylor et al., in press). A more likely scenario is that a regional or global climatic change affected both low- and high-elevation environments and favored a shift from C3-dominated forests to mixed C3 and C4 or C4- dominated grasslands. However, it appears that the transition from forest to grassland may have taken as long as 3.5 Myr in Zhada basin.
A possible scenario, then, is that the vegetation shift began at high elevations due to a global or regional climate change. Suggested factors include the onset of rapidly decreasing global temperatures in the latest Miocene – Pliocene (Zachos et al., 2001) or increased monsoon intensity (Kroon et al., 1991) and associated increased aridity and seasonality of precipitation (Garzione et al., 2003; Guo et al., 2002; Molnar, 2005). 229
Increased warm-season precipitation and increased aridity favor C4 grasses (An et al.,
2005). This situation continued, with variability due to strengthening or weakening of the monsoon, until the onset of a rapid and sustained increase in monsoon intensity and increased aridity between 3.6 - 2.6 Ma (An et al., 2005; An et al., 2001; Guo et al., 2002;
Wan et al., 2007; Zhu et al., 2007). Summer monsoon strength after 2.6 Ma is highly variable (An et al., 2005; An et al., 2001; Kroon et al., 1991). The final transition to open grassland may have been driven directly by this variability, increased aridity, or the continuing decline in global temperatures. As is thought to be the case in the foreland, the floral shift was accompanied by faunal change at high elevations. The possibility remains that these climate changes were driven by expansion of the region of high elevations, particularly on the northern and eastern margins of the Tibetan Plateau (e.g.,
An et al., 2001). However, any such models must take into consideration long-lived high elevations in the southern and central Tibetan Plateau (Currie et al., 2005; Cyr et al.,
2005; DeCelles et al., 2007; Dupont-Nivet et al., in press; Garzione et al., 2000a; Rowley and Currie, 2006; Rowley et al., 2001) and local or regional loss of elevation in the southwestern Tibetan Plateau since the late Miocene (Saylor et al., in press). In proposing this scenario, we suggest that continuing global cooling since the late Miocene may account for the apparent paucity of C4 vegetation on the Tibetan Plateau currently
(Wang et al., 2008c).
230
CONCLUSIONS
1) Lithologic cycles (Types-A and –B) in the Zhada basin are Waltherian parasequences.
2) Sedimentology and sequence stratigraphic analysis indicates that the Zhada basin evolved from a fluvial system to an overfilled basin. The overfilled basin was marked by a broad depositional plain dominated by wetlands bordering a large braided river. From there, the basin evolved sequentially to a balanced-fill basin and an underfilled basin. The final stage was marked by open lacustrine conditions which give way to prograding basin-margin alluvial fans. The typical regression through the basin-type sequence was bypassed by an abrupt return to fluvial conditions. This agrees with overtopping of a basin sill and integration of the modern Sutlej drainage network (Brookfield, 1998;
Saylor et al., in review).
3) Two orders of sequences are recognized in Zhada basin in addition to the parasequences mentioned above. The first order sequence is the result of tectonically created accommodation and infilling. The second order sequences are of ambiguous origin but may be linked to continued fault movement.
4) Where best expressed and dated parasequences have and average duration of ~92 kyr and are likely the result of climatic changes associated with Milankovitch cycles.
This is the first time that 100 kyr cycles have been reported for late Miocene – Pliocene deposits on the Tibetan Plateau and presents an unparalleled opportunity to study high- frequency climate change at high elevations. 231
18 5) Within parasequences, the lowest δ Occ values and, by implication, of Zhada paleo-lake water, are associated with flooding. From the flooding surface through
18 maximum regression δ Occ values increase. This trend is the result of low
Evaporation/Precipitation during flooding and the associated increase in lake volume and decrease in volume weighted average water residence time.
6) The data presented in this paper are consistent with a tectonic origin of the Zhada
Basin. Possible tectonic originating causes include crustal thinning or tectonic damming due to arc-parallel extension.
7) It is likely that regional or global climate change, rather than basin uplift, was the cause of the observed floral and faunal turnover in Zhada basin. The turnover, marked by decreased arboreal pollen in favor of shrub and grass pollen and a decline in the mega- faunal populations, is similar in age and character to that observed in other basins on and surrounding the Tibetan Plateau. In the Himalayan foreland and elsewhere the turnover is attributed to regional or global climate change. Though the introduction of C4 vegetation had previously been documented on the southern Tibetan Plateau, the large- scale change from forest to grassland and the accompanying change in fauna observed in the low-elevation Siwalik group had not been extrapolated to high elevations. 232
Figure 4.1. A. Elevation, shaded relief and generalized tectonic map of the Himalayan – Tibetan orogenic system showing the location of the Zhada basin relative to major structures. B. Generalized geologic map of the Zhada region. Modified from published mapping by Cheng and Xu (1987), Murphy et al. (2002; 2000) and unpublished mapping by M. Murphy. 233
Figure 4.2. (A) South Zhada lithologic section and associated magnetostratigraphic section and correlation to the global polarity timescale (GPTS) of Lourens et al. (2004). 234
235
Figure 4.3. The synthetic wave form constructed for spectral analysis. Depo-codes relate to lithofacies associations (alluvial fan and fluvial associations were assigned a value of 5; supra-littoral associations, 4; littoral associations, 3; and profundal associations, 2 or 1 based on the presence or absence of terrigenous clastic or biologic material). At ages < 3.3 Ma the waveform saturates at values of 5 due to the infilling of Zhada paleo-lake and the progradation of lake-margin depositional environments. Similarly, the inability to distinguish fluctuations in water level during times of profundal or alluvial fan/fluvial sedimentation results in clipping of the waveform. The record of insolation variation (Laskar et al., 2004) is provided for comparison. 236
Figure 4.4. (A and B) Idealized forms of sequence types A and B and interpreted depositional environments (C). (D) Simplified representation of the relationship between lake level, water and sediment flux and lake δ18O values. The simplifications involve the assumption that endmember influx and efflux δ18O values are invariant and that efflux via evaporation is proportional to lake area. Vertical grey boxes indicate the time of retrogradation (sediment influx Figure 4.5. A: Type-A cycles. Cliff is ~15 m. B. Photomosaic of typical progradational sequences in the lacustrine portion of the Zhada Formation (Nl). C. Type-B cycles. Lowermost cycle is ~ 9 m. Lower slope-forming interval represents upward-coarsening profundal to littoral mudstones and siltstones (P1, L1, L2) which are capped by cliff- forming littoral or supra-littoral sandstones (L2 or S1). 238 239 Figure 4.6. Portion of Figure 4.7 showing detailed parasequence scale correlations. See Figures 4.7 and 4.10 for legend. 240 241 242 Figure 4.7. basin-wide lithostratigraphic and sequence stratigraphic correlations for (a) a north – south transect and (B) a southeast – northwest transect. See Figure 4.1B for locations of transects. 243 Figure 4.8. Second order transgressive surface showing the abrupt transition from lithofacies association S1 and F2 sandstone to lithofacies P1 profundal claystone. 244 Figure 4.9. (A.) Power spectrum of the entire interval (5.23 – 2.581 Ma). The spectrum has peaks at ~100 kyr at the 95% confidence level and ~ 23 kyr at the 85% confidence 245 level. (B.) Harmonic analysis of the entire interval reveals dominant peaks at 379 and 91.7 kyr but also has significant red noise. (C.) Harmonic analysis of the interval from 5.23 – 3.3 Ma reveals the same dominant peaks but red noise peaks are significantly suppressed. (D.) Coherence analysis reveals peaks at 80 ± 13, 26 ± 1, and 18.9 ± 0.6 kyr. Vertical error bars indicate the 95% confidence interval. 246 Figure 4.10. South Zhada lithologic section and associated δ18O values of aquatic gastropods. Horizontal black lines represent parasequence boundaries. Thick vertical green boxes indicate the sequences that were used to construct Figure 12. Within all five 18 sequences where a trend is evident, δ Occ values increase from the flooding surface to 247 the maximum regression surface. Vertical orange boxes indicate sequences which show a possible, though not clear, trend. Vertical red boxes indicate sequences with sufficient 18 sampling density that trends in δ Occ values may be expected but where no trends are observed. 248 Figure 4.11. The trajectory of Zhada basin evolution in accommodation and sediment- and water-supply space. Also shown are fields which are occupied by overfilled, balanced-fill and underfilled basins. The Zhada basin followed a typical evolutionary pattern from fluvial to underfilled basin due to an increase in accommodation (Solid black arrow A) until a new sill was breached (B). At this point the basin underwent a discontinuous return to fluvial conditions, bypassing the usual progression back through the balanced-fill and overfilled fields (Dashed black arrow C). Modified from Bohacs et al. (2000). 249 250 Figure 4.12. δ18O and δ13C values (VPDB) of aquatic gastropods from five sequences (indicated in Figure 10) are plotted against their normalized height above the flooding surface. The lowest values occur just above the flooding surface and represent lake expansion associated with a decrease in Evaporation/Precipitation. However, continued 18 13 evaporative enrichment and isotopic evolution means that δ Occ and δ Ccc values increase through most of the regressive sequence. 251 Table 4.1. Data used in frequency analysis Depositional Stratigraphic Abs. Age environment level (m) (Ma) code 251.41 5.23 2 251.91 5.226433 2 252.21 5.224292 3 252.41 5.222865 3 252.91 5.219298 3 253.06 5.218228 4 253.41 5.215731 4 253.91 5.212163 4 254.41 5.208596 4 254.51 5.207882 2 254.91 5.205029 2 255.41 5.201461 2 255.91 5.197894 2 256.41 5.194326 2 256.91 5.190759 3 257.41 5.187192 3 257.91 5.183624 3 258.41 5.180057 3 258.91 5.17649 3 259.41 5.172922 3 259.91 5.169355 3 260.06 5.168285 2 260.41 5.165788 2 260.91 5.16222 2 261.41 5.158653 2 261.91 5.155086 2 262.41 5.151518 2 262.76 5.149021 2 262.91 5.147951 4 263.41 5.144384 4 263.91 5.140816 4 264.41 5.137249 4 264.91 5.133682 4 265.41 5.130114 4 252 265.91 5.126547 4 266.21 5.124406 3 266.41 5.122979 3 266.91 5.119412 3 267.41 5.115845 3 267.51 5.115131 4 267.91 5.112277 4 268.41 5.10871 4 268.56 5.10764 3 268.91 5.105143 3 269.01 5.104429 1 269.41 5.101575 1 269.91 5.098008 1 270.41 5.094441 1 270.91 5.090873 1 271.41 5.087306 1 271.91 5.083739 1 272.41 5.080171 1 272.91 5.076604 1 273.41 5.073037 1 273.91 5.069469 1 274.41 5.065902 1 274.56 5.064832 2 274.91 5.062334 2 275.41 5.058767 2 275.91 5.0552 2 276.41 5.051632 2 276.91 5.048065 2 277.16 5.046281 3 277.41 5.044498 3 277.91 5.04093 3 278.41 5.037363 3 278.91 5.033796 3 279.41 5.030228 3 279.91 5.026661 3 280.41 5.023094 3 280.56 5.022023 2 280.91 5.019526 2 281.41 5.015959 2 281.91 5.012392 2 253 282.41 5.008824 2 282.76 5.006327 3 282.91 5.005257 3 283.41 5.001689 3 283.91 4.998122 3 284.41 4.994555 3 284.91 4.990987 3 285.41 4.98742 3 285.91 4.983853 3 286.31 4.980999 4 286.41 4.980285 4 286.91 4.976718 4 287.21 4.974578 3 287.41 4.973151 3 287.91 4.969583 3 288.01 4.96887 1 288.41 4.966016 1 288.91 4.962449 1 289.41 4.958881 1 289.91 4.955314 1 290.41 4.951747 1 290.91 4.948179 1 291.41 4.944612 3 291.91 4.941045 5 292.41 4.937477 5 292.91 4.93391 5 293.41 4.930342 5 293.91 4.926775 5 294.41 4.923208 5 294.91 4.91964 5 295.41 4.916073 5 295.91 4.912506 5 296.41 4.908938 5 296.91 4.905371 3 297.06 4.904301 3 297.41 4.901804 1 297.91 4.898236 1 298.41 4.894669 1 298.91 4.891102 1 299.41 4.887534 1 254 299.91 4.883967 1 300.41 4.8804 1 300.91 4.876832 1 301.41 4.873265 1 301.81 4.870411 3 301.91 4.869697 3 302.41 4.86613 3 302.56 4.86506 4 302.91 4.862563 4 303.41 4.858995 4 303.91 4.855428 4 304.41 4.851861 4 304.91 4.848293 4 305.41 4.844726 4 305.66 4.842942 3 305.91 4.841159 3 306.41 4.837591 3 306.66 4.835808 4 306.91 4.834024 4 307.21 4.831884 1 307.41 4.830457 1 307.91 4.826889 1 308.41 4.823322 1 308.91 4.819755 1 309.41 4.816187 1 309.91 4.81262 1 310.41 4.809053 1 310.91 4.805485 1 311.41 4.801918 1 311.91 4.79835 1 312.16 4.796567 3 312.41 4.794783 3 312.91 4.791216 3 313.41 4.787648 3 313.91 4.784081 3 314.41 4.780514 3 314.91 4.776946 3 314.96 4.77659 4 315.41 4.773379 4 315.91 4.769812 4 255 316.41 4.766244 4 316.91 4.762677 4 317.41 4.75911 4 317.81 4.756256 5 317.91 4.755542 5 318.41 4.751975 5 318.91 4.748408 5 319.41 4.74484 5 319.91 4.741273 5 320.41 4.737705 5 320.91 4.734138 5 321.16 4.732354 4 321.41 4.730571 4 321.91 4.727003 4 322.06 4.725933 3 322.36 4.723793 1 322.41 4.723436 1 322.91 4.719869 1 323.41 4.716301 1 323.91 4.712734 1 324.41 4.709167 1 324.91 4.705599 1 325.41 4.702032 1 325.91 4.698465 1 326.41 4.694897 1 326.91 4.69133 1 327.41 4.687763 1 327.91 4.684195 1 328.41 4.680628 1 328.76 4.678131 4 328.91 4.677061 4 329.41 4.673493 4 329.76 4.670996 5 329.91 4.669926 5 330.41 4.666358 5 330.91 4.662791 5 331.01 4.662078 3 331.41 4.659224 3 331.91 4.655656 3 332.41 4.652089 3 256 332.91 4.648522 3 333.21 4.646381 1 333.41 4.644954 1 333.91 4.641387 1 334.41 4.63782 1 334.91 4.634252 1 335.41 4.630685 1 335.91 4.627118 1 336.41 4.62355 1 336.91 4.619983 1 337.41 4.616416 1 337.51 4.615702 3 337.91 4.612848 3 338.41 4.609281 3 338.91 4.605713 3 339.41 4.602146 3 339.91 4.598579 3 340.41 4.595011 3 340.91 4.591444 3 341.06 4.590374 5 341.41 4.587877 5 341.91 4.584309 5 342.41 4.580742 5 342.91 4.577175 5 343.41 4.573607 5 343.91 4.57004 5 344.41 4.566473 5 344.91 4.562905 5 345.41 4.559338 5 345.91 4.555771 5 346.41 4.552203 5 346.91 4.548636 5 347.41 4.545068 5 347.91 4.541501 5 348.41 4.537934 5 348.91 4.534366 5 349.16 4.532583 4 349.41 4.530799 4 349.91 4.527232 4 350.01 4.526518 5 257 350.41 4.523664 5 350.91 4.520097 5 351.41 4.51653 5 351.91 4.512962 5 352.41 4.509395 5 352.91 4.505828 5 353.41 4.50226 5 353.86 4.49905 3 353.91 4.498693 3 354.41 4.495126 3 354.76 4.492628 5 354.91 4.491558 5 355.41 4.487991 5 355.91 4.484424 5 356.41 4.480856 5 356.91 4.477289 5 357.41 4.473721 5 357.91 4.470154 5 357.96 4.469797 4 358.41 4.466587 4 358.91 4.463019 4 359.41 4.459452 4 359.76 4.456955 3 359.91 4.455885 3 360.41 4.452317 3 360.91 4.44875 3 361.41 4.445183 3 361.91 4.441615 3 362.41 4.438048 3 362.91 4.434481 3 363.41 4.430913 3 363.56 4.429843 5 363.91 4.427346 5 364.41 4.423779 5 364.91 4.420211 5 365.41 4.416644 5 365.91 4.413076 5 366.41 4.409509 5 366.91 4.405942 5 367.41 4.402374 5 258 367.91 4.398807 5 368.41 4.39524 5 368.91 4.391672 5 369.41 4.388105 5 369.91 4.384538 5 370.41 4.38097 5 370.91 4.377403 5 371.41 4.373836 5 371.91 4.370268 5 372.41 4.366701 5 372.76 4.364204 3 372.91 4.363134 1 373.41 4.359566 1 373.91 4.355999 1 374.41 4.352432 1 374.91 4.348864 1 375.41 4.345297 1 375.91 4.341729 1 376.41 4.338162 1 376.91 4.334595 1 377.41 4.331027 1 377.91 4.32746 1 378.11 4.326033 3 378.41 4.323893 3 378.91 4.320325 3 379.41 4.316758 3 379.91 4.313191 3 380.41 4.309623 3 380.91 4.306056 3 381.16 4.304272 4 381.41 4.302489 4 381.91 4.298921 4 382.41 4.295354 4 382.91 4.291787 4 383.41 4.288219 4 383.91 4.284652 4 384.41 4.281084 4 384.91 4.277517 4 385.41 4.27395 4 385.76 4.271453 1 259 385.91 4.270382 1 386.11 4.268955 4 386.41 4.266815 4 386.61 4.265388 1 386.91 4.263248 1 387.41 4.25968 2 387.91 4.256113 2 388.06 4.255043 3 388.41 4.252546 3 388.51 4.251832 4 388.91 4.248978 4 389.41 4.245411 4 389.51 4.244697 3 389.91 4.241844 3 390.01 4.24113 1 390.41 4.238276 1 390.91 4.234709 1 391.41 4.231142 1 391.91 4.227574 1 392.41 4.224007 1 392.91 4.220439 1 393.41 4.216872 1 393.76 4.214375 2 393.91 4.213305 2 394.41 4.209737 2 394.51 4.209024 4 394.91 4.20617 4 395.41 4.202603 4 395.91 4.199035 4 396.41 4.195468 4 396.91 4.191901 4 397.41 4.188333 4 397.91 4.184766 4 398.41 4.181199 4 398.46 4.180842 1 398.71 4.179058 2 398.91 4.177631 2 399.41 4.174064 2 399.71 4.171924 3 399.91 4.170497 3 260 400.41 4.166929 3 400.91 4.163362 3 400.96 4.163005 5 401.41 4.159795 5 401.91 4.156227 5 402.41 4.15266 5 402.91 4.149092 5 403.41 4.145525 5 403.91 4.141958 5 404.41 4.13839 5 404.91 4.134823 5 405.41 4.131256 5 405.91 4.127688 5 406.41 4.124121 5 406.46 4.123764 3 406.91 4.120554 3 407.36 4.117343 3 407.41 4.116986 5 407.91 4.113419 5 408.21 4.111279 2 408.41 4.109852 2 408.91 4.106284 2 409.41 4.102717 5 409.76 4.10022 3 409.91 4.09915 2 410.41 4.095582 2 410.91 4.092015 2 411.11 4.090588 3 411.41 4.088447 3 411.91 4.08488 3 412.41 4.081313 3 412.91 4.077745 3 413.41 4.074178 5 413.91 4.070611 5 414.41 4.067043 5 414.91 4.063476 5 415.41 4.059909 5 415.91 4.056341 5 416.41 4.052774 5 416.91 4.049207 5 261 417.41 4.045639 5 417.91 4.042072 5 418.41 4.038505 5 418.91 4.034937 5 419.41 4.03137 5 419.91 4.027803 5 420.41 4.024235 5 420.91 4.020668 5 421.41 4.0171 5 421.91 4.013533 5 422.41 4.009966 5 422.91 4.006398 5 423.41 4.002831 5 423.91 3.999264 5 424.41 3.995696 5 424.91 3.992129 5 425.26 3.989632 3 425.41 3.988562 3 425.91 3.984994 3 426.36 3.981784 4 426.41 3.981427 4 426.91 3.97786 4 427.11 3.976433 3 427.41 3.974292 3 427.91 3.970725 3 428.01 3.970011 1 428.41 3.967158 1 428.91 3.96359 1 429.41 3.960023 1 429.91 3.956455 1 430.41 3.952888 1 430.91 3.949321 1 431.41 3.945753 1 431.91 3.942186 1 432.41 3.938619 1 432.76 3.936122 2 432.91 3.935051 2 433.41 3.931484 2 433.91 3.927917 2 434.21 3.925776 4 262 434.41 3.924349 3 434.86 3.921139 1 434.91 3.920782 1 435.41 3.917215 1 435.91 3.913647 1 436.41 3.91008 1 436.91 3.906513 1 437.41 3.902945 1 437.91 3.899378 1 438.16 3.897594 3 438.41 3.895811 3 438.91 3.892243 3 439.41 3.888676 3 439.91 3.885108 3 440.16 3.883325 5 440.41 3.881541 5 440.91 3.877974 5 441.41 3.874406 5 441.91 3.870839 5 442.41 3.867272 5 442.91 3.863704 5 443.41 3.860137 5 443.91 3.85657 5 444.41 3.853002 5 444.91 3.849435 5 445.41 3.845868 5 445.91 3.8423 5 446.41 3.838733 5 446.91 3.835166 5 447.26 3.832668 3 447.36 3.831955 2 447.41 3.831598 2 447.91 3.828031 2 448.41 3.824463 2 448.91 3.820896 2 449.41 3.817329 5 449.91 3.813761 5 450.41 3.810194 5 450.91 3.806627 5 451.41 3.803059 5 263 451.91 3.799492 5 452.41 3.795925 5 452.91 3.792357 5 453.41 3.78879 5 453.91 3.785223 5 454.41 3.781655 5 454.91 3.778088 5 455.41 3.774521 5 455.91 3.770953 5 456.41 3.767386 5 456.76 3.764889 4 456.91 3.763818 4 457.41 3.760251 4 457.91 3.756684 4 458.41 3.753116 4 458.66 3.751333 5 458.91 3.749549 5 459.41 3.745982 5 459.91 3.742414 5 460.41 3.738847 5 460.91 3.73528 5 461.26 3.732783 3 461.41 3.731712 3 461.91 3.728145 3 462.36 3.724934 1 462.41 3.724578 1 462.91 3.72101 1 463.41 3.717443 1 463.91 3.713876 1 464.16 3.712092 4 464.41 3.710308 4 470.56 3.66643 5 470.91 3.663933 5 471.41 3.660365 5 471.91 3.656798 5 472.06 3.655728 3 472.41 3.653231 3 472.81 3.650377 1 472.91 3.649663 1 473.41 3.646096 1 264 473.91 3.642529 1 474.36 3.639318 3 474.41 3.638961 3 474.91 3.635394 3 475.41 3.631826 3 475.91 3.628259 3 476.11 3.626832 2 476.41 3.624692 2 476.91 3.621124 2 477.41 3.617557 2 477.91 3.61399 2 478.41 3.610422 2 478.91 3.606855 2 479.16 3.605071 4 479.41 3.603288 4 479.91 3.59972 4 479.96 3.599364 3 480.41 3.596153 3 480.56 3.595083 2 480.91 3.592586 2 481.41 3.589018 2 481.91 3.585451 2 482.41 3.581884 2 482.91 3.578316 2 483.41 3.574749 2 483.56 3.573679 4 483.91 3.571182 4 484.41 3.567614 4 484.91 3.564047 4 485.41 3.560479 4 485.91 3.556912 4 485.96 3.556555 3 486.41 3.553345 3 486.91 3.549777 3 487.41 3.54621 3 487.91 3.542643 3 488.41 3.539075 3 488.91 3.535508 2 489.41 3.531941 2 489.91 3.528373 2 265 490.41 3.524806 2 490.86 3.521595 1 490.91 3.521239 1 491.41 3.517671 1 491.91 3.514104 1 492.41 3.510537 1 492.91 3.506969 1 493.41 3.503402 1 493.91 3.499834 1 494.41 3.496267 1 494.91 3.4927 1 495.26 3.490203 2 495.41 3.489132 2 495.91 3.485565 2 496.41 3.481998 2 496.91 3.47843 2 497.41 3.474863 2 497.91 3.471296 2 498.41 3.467728 2 498.91 3.464161 2 498.96 3.463804 3 499.41 3.460594 3 499.91 3.457026 3 500.41 3.453459 3 500.91 3.449892 3 501.41 3.446324 3 501.91 3.442757 3 502.41 3.439189 3 502.91 3.435622 3 503.41 3.432055 3 503.91 3.428487 3 504.41 3.42492 3 504.56 3.42385 2 504.91 3.421353 2 505.31 3.418499 5 505.41 3.417785 5 505.91 3.414218 5 506.41 3.410651 5 506.91 3.407083 5 507.41 3.403516 5 266 507.91 3.399949 5 508.41 3.396381 5 508.91 3.392814 5 509.41 3.389247 5 509.91 3.385679 5 510.41 3.382112 5 510.51 3.381398 3 510.91 3.378545 3 511.01 3.377831 5 511.41 3.374977 5 511.91 3.37141 5 512.41 3.367842 5 512.91 3.364275 5 513.01 3.363562 4 513.41 3.360708 4 513.66 3.358924 1 513.91 3.35714 1 514.41 3.353573 1 514.91 3.350006 1 515.16 3.348222 4 515.41 3.346438 4 515.91 3.342871 4 516.26 3.340374 3 516.41 3.339304 3 516.91 3.335736 3 517.41 3.332169 3 517.91 3.328602 3 518.41 3.325034 3 518.91 3.321467 3 519.41 3.3179 3 519.91 3.314332 3 520.41 3.310765 3 520.76 3.308268 5 520.91 3.307197 5 521.41 3.30363 5 521.91 3.300063 5 522.41 3.296495 5 522.91 3.292928 5 523.41 3.289361 5 523.91 3.285793 5 267 524.41 3.282226 5 524.91 3.278659 5 525.41 3.275091 5 525.91 3.271524 5 526.36 3.268313 5 526.41 3.267957 5 526.91 3.264389 5 527.41 3.260822 5 527.91 3.257255 5 528.41 3.253687 5 528.91 3.25012 5 529.41 3.246553 5 529.91 3.242985 5 530.41 3.239418 5 530.91 3.23585 5 531.16 3.234067 3 531.41 3.232283 3 531.91 3.228716 3 532.36 3.225505 5 532.41 3.225148 5 532.91 3.221581 5 533.41 3.218014 5 533.91 3.214446 5 534.41 3.210879 5 534.91 3.207312 5 535.41 3.203744 5 535.91 3.200177 5 536.41 3.19661 5 536.91 3.193042 5 537.41 3.189475 5 537.91 3.185908 5 538.41 3.18234 5 538.91 3.178773 5 539.41 3.175205 5 539.91 3.171638 5 540.41 3.168071 5 540.66 3.166287 3 540.91 3.164503 3 541.41 3.160936 3 541.91 3.157369 3 268 542.41 3.153801 3 542.66 3.152018 5 542.91 3.150234 5 543.41 3.146667 5 543.91 3.143099 5 544.41 3.139532 5 544.91 3.135965 5 545.41 3.132397 5 545.91 3.12883 5 546.41 3.125263 5 546.91 3.121695 5 547.41 3.118128 5 547.91 3.114561 5 548.41 3.110993 5 548.91 3.107426 5 549.41 3.103858 5 549.91 3.100291 5 550.41 3.096724 5 550.91 3.093156 5 551.41 3.089589 5 551.91 3.086022 5 552.41 3.082454 5 552.91 3.078887 5 553.41 3.07532 5 553.91 3.071752 5 554.41 3.068185 5 554.91 3.064618 5 555.41 3.06105 5 555.91 3.057483 5 556.41 3.053916 5 556.91 3.050348 5 557.41 3.046781 5 557.91 3.043213 5 558.41 3.039646 5 558.91 3.036079 5 559.41 3.032511 5 559.91 3.028944 5 560.41 3.025377 5 560.91 3.021809 5 561.41 3.018242 5 269 561.91 3.014675 5 562.41 3.011107 5 562.91 3.00754 5 563.41 3.003973 5 563.91 3.000405 5 564.41 2.996838 5 564.91 2.993271 5 565.41 2.989703 5 565.91 2.986136 5 566.41 2.982568 5 566.51 2.981855 4 566.91 2.979001 4 567.41 2.975434 5 567.91 2.971866 5 568.41 2.968299 5 568.91 2.964732 5 569.41 2.961164 5 569.91 2.957597 5 570.41 2.95403 5 570.91 2.950462 5 571.41 2.946895 5 571.91 2.943328 5 572.41 2.93976 5 572.91 2.936193 5 573.41 2.932626 5 573.91 2.929058 5 574.41 2.925491 5 574.91 2.921924 5 575.41 2.918356 5 575.91 2.914789 5 576.41 2.911221 5 576.91 2.907654 5 577.26 2.905157 4 577.41 2.904087 4 577.91 2.900519 4 578.41 2.896952 4 578.91 2.893385 4 579.06 2.892314 3 579.41 2.889817 3 579.91 2.88625 3 270 580.41 2.882683 3 580.76 2.880186 5 580.91 2.879115 5 581.41 2.875548 5 581.91 2.871981 5 582.41 2.868413 5 582.91 2.864846 5 583.41 2.861279 5 583.91 2.857711 5 584.41 2.854144 5 584.91 2.850576 5 585.31 2.847723 3 585.41 2.847009 3 585.91 2.843442 3 586.41 2.839874 3 586.76 2.837377 4 586.91 2.836307 4 587.41 2.83274 4 587.91 2.829172 4 588.01 2.828459 3 588.41 2.825605 3 588.91 2.822038 3 589.41 2.81847 3 589.81 2.815616 4 589.91 2.814903 4 590.41 2.811336 4 590.91 2.807768 4 591.21 2.805628 3 591.41 2.804201 3 591.91 2.800634 3 592.31 2.79778 5 592.41 2.797066 5 592.91 2.793499 5 593.41 2.789932 5 593.91 2.786364 5 594.31 2.78351 4 594.41 2.782797 4 594.91 2.779229 4 595.41 2.775662 4 595.91 2.772095 5 271 596.41 2.768527 5 596.91 2.76496 5 597.41 2.761393 5 597.91 2.757825 5 598.41 2.754258 5 598.91 2.750691 5 599.41 2.747123 5 599.91 2.743556 5 600.41 2.739989 5 600.91 2.736421 5 601.41 2.732854 5 601.91 2.729287 5 602.21 2.727146 4 602.41 2.725719 4 602.91 2.722152 4 603.21 2.720011 5 603.41 2.718584 5 603.91 2.715017 5 604.41 2.71145 5 604.91 2.707882 5 605.41 2.704315 5 605.91 2.700748 5 606.41 2.69718 5 606.71 2.69504 1 606.91 2.693613 1 607.41 2.690046 1 607.91 2.686478 1 608.41 2.682911 1 608.91 2.679344 1 609.41 2.675776 1 609.91 2.672209 1 610.41 2.668642 1 610.91 2.665074 1 611.41 2.661507 1 611.91 2.657939 1 612.41 2.654372 1 612.71 2.652232 4 612.91 2.650805 4 613.41 2.647237 4 613.91 2.64367 4 272 614.41 2.640103 4 614.46 2.639746 5 614.91 2.636535 5 615.41 2.632968 5 615.91 2.629401 5 616.41 2.625833 5 616.91 2.622266 5 617.41 2.618699 5 617.91 2.615131 5 618.41 2.611564 5 618.91 2.607997 5 619.41 2.604429 5 619.91 2.600862 5 620.41 2.597295 5 620.91 2.593727 5 621.41 2.59016 5 621.91 2.586592 5 622.41 2.583025 5 622.71 2.580885 5 273 Table 4.2: Lithofacies association codes, descriptions, and interpretations. We identify 14 lithofacies associations and five depositional environments. Depositional environments are as follows: F-: Fluvial, S-: Supra-littoral, L-: Littoral, P-: Profundal, and A-: Alluvial fan. Lithofacies Description Interpretation association F1: Gcmi, - Amalgamated channel forms and tabular units of - Deposits of migrating channels, bars, bedload Gch, Gt, Gcf moderately sorted, clast-supported pebble sheets, and gravel dunes of a braided river within conglomerate featuring abundant traction sedimentary a low-gradient fluvial setting (Bristow and Best, structures 1993; Cant and Walker, 1978; Collinson, 1996; - Deposits are 2 – 10 m thick Heinz et al., 2003; Lunt et al., 2004) - Erosive bases. F2: St, Sp, - Tabular units 0.1 – 5 m thick of horizontally or cross- - Sheet flood deposits on medial to distal fluvial Sh, Sc stratified sandstone fans in a marshy floodplain or marginal lacustrine - Abundant load casts and ball-and-pillow structures setting (Hampton and Horton, 2007; Saez et al., and rare channel forms 2007) F3: Sm, Sc, - Massive, organic-rich, strongly calcareous siltstones - Marshy floodplain or lake-margin wetland Mm, Mc, Ml, and sandstones 0.1 – 4 m thick featuring soft- deposits (Allen and Collinson, 1986) Mh sediment deformation but no pedogenesis - Contains ostracods, root traces, and small planorbid gastropods (Gyraulus sp?) S1: Gct, - Tabular, upward coarsening sandstone to pebble - Product of sedimentation within a delta complex Gcmi, Sp, St, conglomerate 0.25 to 6 m thick (Allen and Collinson, 1986; Saez et al., 2007) Sh, Sm, Sr - Erosional bases and abrupt tops - Horizontal stratification, climbing-, trough-, and planar cross-stratification - Channelized deposits up to 0.5 m thick are locally present - Abundant, well-preserved, robust gastropod shells S2: Sh - Low-angle laminae up to 3 cm thick without internal - Vegetated eolian sand-flat (Hunter, 1977) structure - Developed in well-sorted, fine-grained sand -Root traces and soft-sediment deformation are common S3: Sf - Stacked units (0.5-1.5 m thick) of steeply-inclined, - Lacustrine coastal plain dune deposits upward-coarsening laminations - Developed in well-sorted, fine-grained sandstone - Root traces and soft-sediment deformation are common L1: Ml - Papery, laminated siltstone - Deposition with a grass-rich, shallowly - Abundant fossil grasses, fragmentary shell material submerged, low-gradient, lake-margin and occasional fish fossils environment (Allen and Collinson, 1986; Talbot and Allen, 1996) L2: Mr, Sr, - Upward coarsening sandstone deposits 0.5 – 3 m - Deposits of a terminal lobe on a prograding Srw, Sp, Sh, thick delta front (Allen and Collinson, 1986; Dam and Sm - Gradational bases and erosional tops Surlyk, 1993; Jopling, 1965; Saez et al., 2007; - Climbing-ripple and wave-ripple cross-stratification Talbot and Allen, 1996) and mud drapes P1: Mh, Mm - Upward coarsening massive or horizontally - Profundal lacustrine deposition (below fair- laminated silty claystone weather wave base) - Up to 10 m thick, includes dispersed, plant, ostracod, and fish fossils P2: Sh, Sm, - 2 m-thick stacks of upward-fining laminae up to 3 cm - Stacked deposits of turbidity currents (primarily Mh thick Bouma A and B) (Bouma, 1962; Giovanoli, 1990; - Basal surfaces of individual laminae are abrupt and Lowe, 1982; Mutti et al., 2003) the upward transition to siltstone is gradational, lower portion is massive and grades upward to horizontally laminated A1: Gcm, - Poorly sorted, very angular to subrounded, pebble to - High-concentration, unconfined sheet-flood Gch, Gcmi boulder conglomerate deposits (Blair, 2000; Blair and McPherson, 274 - 0.5 – 20 m thick 1994b; DeCelles et al., 1991; Nemec and Steel, - Erosive bases, horizontal stratification and long-axis 1984; e.g., Pierson, 1980; Pierson, 1981) transverse imbrication A2: Gmm, - Massive, unorganized, matrix-supported boulder - Debris flow deposits (Blair and McPherson, Gcm conglomerate 0.5 – 3 m thick 1994a; Pierson, 1980) - No erosive bases A3:Gcmi,Gch, - Imbricated, lenticular, clast-supported, pebble – - Deposited by streams in alluvial fan channels Gcf, Gt boulder conglomerate bodies (DeCelles et al., 1991) - Erosive bases and horizontal- and cross-stratification A4: Gx - Chaotic matrix- and clast supported boulder - High-concentration flood or debris flow deposits conglomerate deposits into a water-saturated environment (Blair, 2000; - Abundant load casts and ball and pillow structures Miall, 2000; Nemec and Steel, 1984; Pivnik, (up to 2 m of relief on some structures) 1990; Postma, 1983) 275 Table 4.3. Stable isotope data δ13C δ 18O Stratigraphic height (‰, (‰, Sample Name (m) VPDB) VPDB) 1SZ12 309.65 -0.9 -3.9 1SZ13 310.65 -3.0 -12.5 1SZ13.8 311.45 -1.3 -3.2 1SZ18 315.65 2.1 -1.8 1SZ24 321.65 -0.2 -5.4 1SZ24.1 321.75 -0.5 -4.6 1SZ27.9 325.55 0.0 -2.8 1SZ32 329.65 0.5 -1.5 2SZ43 376.1 0.9 -1.8 2SZ43.1 376.2 -0.4 -6.8 2SZ47 380.1 -0.6 -1.9 2SZ51.5 384.6 -0.2 -2.4 2SZ51.5AD0.5 384.6 -0.6 -0.6 2SZ51.5AD10 384.6 0.2 -1.2 2SZ51.5AD11 384.6 0.2 -2.1 2SZ51.5AD12 384.6 0.1 -2.2 2SZ51.5AD13 384.6 0.3 -2.1 2SZ51.5AD14 384.6 0.2 -2.5 2SZ51.5AD15 384.6 0.8 -0.8 2SZ51.5AD3 384.6 -0.4 -2.2 2SZ51.5AD4 384.6 -0.1 -2.1 2SZ51.5AD5 384.6 0.3 -1.6 2SZ51.5AD6 384.6 0.9 -0.8 2SZ51.5AD7 384.6 0.0 -0.3 2SZ51.5AD8 384.6 0.0 -0.3 2SZ51.5AD9 384.6 -0.1 -0.4 2SZ55 388.1 -0.7 -2.3 3SZ0.15 389.25 0.9 -1.7 3SZ24 413.1 -0.3 -2.2 3SZ24.1A 413.2 1.6 -2.8 3SZ24.25A 413.35 0.8 -1.4 3SZ24.25B 413.35 -1.1 -1.8 3SZ24.25C 413.35 0.6 -1.6 3SZ24.3 413.4 0.9 -2.0 3SZ27 416.1 -2.1 0.7 276 3SZ49 438.1 -3.3 -13.7 3SZ50.5 439.6 -1.2 -1.0 3SZ55 444.1 1.2 -2.5 277 Works Cited Abe, M., Yasunari, T., and Kitoh, A., 2005, Sensitivity of the Central Asian climate to uplift of the Tibetan Plateau in the coupled climate model (MRI-CGCM1): The Island Arc, v. 14, p. 378–388. Abell, P.I., and Williams, M.A.J., 1989, Oxygen and carbon isotope ratios in gastropod shells as indicators of paleoenvironments in the Afar region of Ethiopia: Palaeogeography Palaeoclimatology Palaeoecology, v. 74, p. 265-278. Aitchison, J.C., Davis, A.M., Badengzhu, B., and Luo, H., 2002, New constraints on the India-Asia collision: the Lower Miocene Gangrinboche conglomerates, Yarlung Tsangpo suture zone, SE Tibet: Journal of Asian Earth Sciences, v. 21, p. 251- 263. Allegre, C.J., Courtillot, V., Tapponnier, P., Hirn, A., Mattauer, M., Coulon, C., Jaeger, J.J., Achache, J., Scharer, U., Marcoux, J., Burg, J.P., Girardeau, J., Armijo, R., Gariepy, C., Gopel, C., Li, T.D., Xiao, X.C., Chang, C.F., Li, G.Q., Lin, B.Y., Teng, J.W., Wang, N.W., Chen, G.M., Han, T.L., Wang, X.B., Den, W.M., Sheng, H.B., Cao, Y.G., Zhou, J., Qiu, H.R., Bao, P.S., Wang, S.C., Wang, B.X., Zhou, Y.X., and Ronghua, X., 1984, Structure and evolution of the Himalaya- Tibet orogenic belt: Nature, v. 307, p. 17-22. Allen, P., and Allen, J., 1990, Basin Analysis: Principles and applications: Oxford, Blackwell Scientific Publications, 451 p. Allen, P., and Collinson, J., 1986, Lakes, in Reading, H., ed., Sedimentary Environments and Facies: Oxford, Blackwell Scientific Publications, p. 63-94. An, Z., Huang, Y., Liu, W., Guo, Z., Clemens, S., Li, L., Prell, W., Ning, Y., Cai, Y., Zhou, W., Lin, B., Zhang, Q., Cao, Y., Qiang, X., Chang, H., and Wu, Z., 2005, Multiple expansions of C-4 plant biomass in East Asia since 7 Ma coupled with strengthened monsoon circulation: Geology, v. 33, p. 705-708. An, Z.-s., Kutzbach, J.E., Prell, W.L., and Porter, S.C., 2001, Evolution of Asian monsoons and phased uplift of the Himalaya-Tibetan plateau since late Miocene times: Nature, v. 311, p. 62-66. 278 Angevine, C., Heller, P., and Paola, C., 1990, Quantitative sedimentary basin modeling, Volume Continuing education course note series 32: Tulsa, American Association of Petroleum Geologists. Araguas-Araguas, L., Froehlich, K., and Rozanski, K., 1998, Stable isotope composition of precipitation over southeast Asia: Journal of Geophysical Research- Atmospheres, v. 103, p. 28721-28742. Armijo, R., Tapponnier, P., Mercier, J.L., and Han, T.L., 1986, Quanternary extension in southern Tibet - Field observations and tectonic implications: Journal of Geophysical Research-Solid Earth and Planets, v. 91, p. 13803-13872. Aucour, A.M., Sheppard, S.M.F., and Savoye, R., 2003, delta C-13 of fluvial mollusk shells (Rhone River): A proxy for dissolved inorganic carbon?: Limnology and Oceanography, v. 48, p. 2186-2193. Awashi, N., and Prasad, M., 1989, Siwalik plant fossils from Surai Khola area, western Nepal: Paleobotanist, v. 38, p. 298-318. Axelrod, D., 1981, Altitudes of Tertiary forests estimated from paleotemperature, in Liu, D., ed., Geological and ecological studies of Qinghai – Xizang Plateau, Volume 1: Beijing, Science Press, p. 131-137. Ayers, W.B., 1986, Lacustrine and fluvial-deltaic depositional systems, Fort Union Formation (Paleocene), Powder River Basin, Wyoming and Montana: Aapg Bulletin-American Association of Petroleum Geologists, v. 70, p. 1651-1673. Barry, J., Flynn, L., and Pilbeam, D., 1990, Faunal diversity and turnover in a Miocene terrestrial sequence, in Ross, R., and Allmon, W., eds., Causes of evolution: A paleontological perspective: Chicago, University of Chicago Press, p. 381-421. Barry, J., Morgan, M., Flynn, L., Pilbeam, D., Jacobs, L., Lindsay, E., Raza, S., and Solounias, N., 1995, Patterns of faunal turnover and diversity in the Neogene Siwaliks of northern Pakistan: Palaeogeography Palaeoclimatology Palaeoecology, v. 115, p. 209-226. 279 Barry, J.C., Morgan, M.E., Winkler, A.J., Flynn, L.J., Lindsay, E.H., Jacobs, L.L., and Pilbeam, D., 1991, Faunal interchange and Miocene terrestrial vertebrates of southern Asia: Paleobiology, v. 17, p. 231-245. Barton, C.E., Solomon, D.K., Bowman, J.R., Cerling, T.E., and Sayer, M.D., 1987, Chloride budgets in transient lakes - Lakes Baringo, Naivasha, and Turkana: Limnology and Oceanography, v. 32, p. 745-751. Beaumont, C., Jamieson, R.A., Nguyen, M.H., and Medvedev, S., 2004, Crustal channel flows: 1. Numerical models with applications to the tectonics of the Himalayan- Tibetan orogen: Journal of Geophysical Research-Solid Earth, v. 109, p. 29. Blair, T.C., 2000, Sedimentology and progressive tectonic unconformities of the sheetflood-dominated Hell's Gate alluvial fan, Death Valley, California: Sedimentary Geology, v. 132, p. 233-262. Blair, T.C., and McPherson, J.G., 1994a, Alluvial fan processes and forms, in Abrahams, A., and Parsons, A., eds., Geomorphology of Desert Environments: London, Chapman & Hall, p. 354-402. —, 1994b, Alluvial fans and their natrual distinction from rivers based on morphology, hydraulic processes, sedimentary processes, and facies assemblages: Journal of Sedimentary Research Section a-Sedimentary Petrology and Processes, v. 64, p. 450-489. Blisniuk, P.M., and Stern, L.A., 2005, Stable isotope paleoaltimetry: A critical review: American Journal of Science, v. 305, p. 1033-1074. Bloemendal, J., and Demenocal, P., 1989, Evidence for a change in the periodicity of tropical climate cycles at 2.4 Myr from whole-core magnetic-susceptibility measurements: Nature, v. 342, p. 897-900. Bohacs, K., Carroll, A., Neal, J., and Mankiewicz, P., 2000, Lake-basin type, source potential, and hydrocarbon character: An integrated sequence-stratigraphic- geochemical framework, in Gierlowski-Kordesch, E., and Kelts, K., eds., Lake basins through space and time, Volume 46, AAPG Studies in Geology, p. 3-34. 280 Bonadonna, F.P., Leone, G., and Zanchetta, G., 1999, Stable isotope analyses on the last 30 ka molluscan fauna from Pampa grassland, Bonaerense region, Argentina: Palaeogeography Palaeoclimatology Palaeoecology, v. 153, p. 289-308. Bouma, A., 1962, Sedimentology of Some Flysch Deposits; A Graphic Approach to Facies Interpretation: Amsterdam, Elsevier Publishing Co. Bridge, J., 2003, Rivers and Floodplains: Oxford, Blackwell Science Inc., 491 p. Bristow, C., and Best, J., 1993, Braided Rivers: perspectives and problems, in Best, J., and Bristow, C., eds., Braided Rivers, Volume Geological Society Special Publication 75: London, The Geological Society, p. 1-11. Bristow, C.S., Skelly, R.L., and Ethridge, F.G., 1999, Crevasse splays from the rapidly aggrading, sand-bed, braided Niobrara River, Nebraska: effect of base-level rise: Sedimentology, v. 46, p. 1029-1047. Brookfield, M., 1998, The evolution of the great river systems of southern Asia during the Cenozoic India-Asia collision: rivers draining southwards: Geomorphology, v. 22, p. 285-312. Butler, R., 1992, Paleomagnetism: magnetic domains to geologic terranes: Cambridge, Blackwell. Cande, S., and Kent, D., 1995, Revised calibration of the geomagnetic polarity timescale for the Late Cretaceous and Cenozoic: Journal of Geophysical Research-Solid Earth and Planets, v. 100, p. 6093-6095. Cant, D., and Walker, R., 1978, Fluvial processes and facies sequences in sandy braided South Saskatchewan River, Canada: Sedimentology, v. 25, p. 625-648. Cao, W., Chen, Y., Yu, Y., and Zhu, S., 1981, Origin and evolution of Schizothoracine fishes in relation to the upheaval of the Qinghai-Xizang Plateau, in Sciences, T.C.S.E.t.t.Q.-X.P.b.C.A.o., ed., Studies on the Period, Amplitude, and Type of the Uplift of the Qinghai-Xizang Plateau: Beijing, Science Press, p. 118-130. 281 Carroll, A., 1998, Upper Permian lacustrine organic facies evolution, southern Junggar basin, NW China: Organic Geochemistry, v. 28, p. 649-667. Catuneanu, O., 2006, Principles of Sequence Stratigraphy: Amsterdam, Elsevier, 374 p. Cerling, T., Harris, J., MacFadden, B., Leakey, M., Quade, J., Eisenmann, V., and Ehleringer, J., 1997, Global vegetation change through the Miocene/Pliocene boundary: Nature, v. 389, p. 153-158. Chamberlain, C., and Poage, M., 2000, Reconstructing the paleotopography of mountain belts from the isotopic composition of authigenic minerals: Geology, v. 28, p. 115-118. Cheng, J., and Xu, G., 1987, Geologic map of the Gerdake regionat a scale of 1:1000000 and geologic report: Lhasa, Xizang Bureau of Geology and Mineral Resources. Chung, S., Lo, C., Lee, T., Zhang, Y., Xie, Y., Li, X., Wang, K., and Wang, P., 1998, Diachronous uplift of the Tibetan plateau starting 40 Myr ago: Nature, v. 394, p. 769-773. Clemens, S., Prell, W., Murray, D., Shimmield, G., and Weedon, G., 1991, Forcing mechanisms of the Indian-Ocean monsoon: Nature, v. 353, p. 720-725. Clemens, S.C., and Prell, W.L., 2003, A 350,000 year summer-monsoon multi-proxy stack from the Owen ridge, Northern Arabian sea: Marine Geology, v. 201, p. 35- 51. Collinson, J., 1996, Alluvial sediments, in Reading, H., ed., Sedimentary Environments: Processes, Facies and Stratigraphy: Oxford, Blackwell Science Inc. Cottle, J.M., Jessup, M.J., Newell, D.L., Searle, M.P., Law, R.D., and Horstwood, M.S.A., 2007, Structural insights into the early stages of exhumation along an orogen-scale detachment: The South Tibetan Detachment system, Dzakaa Chu section, eastern Himalaya: Journal of Structural Geology, v. 29, p. 1781-1797. 282 Currie, B., Rowley, D., and Tabor, N., 2005, Middle Miocene paleoaltimetry of southern Tibet: Implications for the role of mantle thickening and delamination in the Himalayan orogen: Geology, v. 33, p. 181-184. Cyr, A., Currie, B., and Rowley, D., 2005, Geochemical evaluation of Fenghuoshan Group lacustrine carbonates, North-Central Tibet: Implications for the paleoaltimetry of the Eocene Tibetan Plateau: Journal of Geology, v. 113, p. 517- 533. Dam, G., and Surlyk, F., 1993, Cyclic sedimentationin a large wave- and storm- dominated anoxic lake; Kapp Sterwart Formation (Rhaetian-Sinemurian), Jameson Land, East Greenland, in Posamentier, H., Summerhayes, C., Haq, B., and GP, A., eds., Sequence Stratigraphy and Facies Associations, Volume Special Publication of the International Association of Sedimentologists 18, International Association of Sedimentologists, p. 419-448. Dansgaard, W., 1954, Oxygen-18 abundance in fresh water: Nature, v. 174, p. 234-235. —, 1964, Stable isotopes in precipitation: Tellus, v. 16, p. 436-468. DeCelles, P., Gehrels, G., Najman, Y., Martin, A., Carter, A., and Garzanti, E., 2004, Detrital geochronology and geochemistry of Cretaceous-Early Miocene strata of Nepal: implications for timing and diachroneity of initial Himalayan orogenesis: Earth and Planetary Science Letters, v. 227, p. 313-330. DeCelles, P., Gray, M., Ridgway, K., Cole, R., Pivnik, D., Pequera, N., and Srivastava, P., 1991, Controls on synorogenic alluvial-fan architecture, Beartooth Conglomerate (Paleocene), Wyoming and Montana: Sedimentology, v. 38, p. 567-590. DeCelles, P., Langford, R., and Schwartz, R., 1983, 2 new methods of paleocurrent determination from trough cross-stratification: Journal of Sedimentary Petrology, v. 53, p. 629-642. DeCelles, P.G., Gehrels, G.E., Quade, J., LaReau, B., and Spurlin, M., 2000, Tectonic implications of U-PL zircon ages of the Himalayan orogenic belt in Nepal: Science, v. 288, p. 497-499. 283 DeCelles, P., Quade, J., Kapp, P., Fan, M., Dettman, D., and Ding, L., 2007, High and dry in central Tibet during the Late Oligocene: Earth and Planetary Science Letters, v. 253, p. 389-401. DeCelles, P., Robinson, D., and Zandt, G., 2002, Implications of shortening in the Himalayan fold-thrust belt for uplift of the Tibetan Plateau: Tectonics, v. 21, p. -. Dettman, D., Kohn, M., Quade, J., Ryerson, F., Ojha, T., and Hamidullah, S., 2001, Seasonal stable isotope evidence for a strong Asian monsoon throughout the past 10.7 m.y.: Geology, v. 29, p. 31-34. Dettman, D., Reische, A., and Lohmann, K., 1999, Controls on the stable isotope composition of seasonal growth bands in aragonitic fresh-water bivalves (unionidae): Geochimica et Cosmochimica Acta, v. 63, p. 1049-1057. Dettman, D.L., and Lohmann, K.C., 2000, Oxygen isotope evidence for high-altitude snow in the Laramide Rocky Mountains of North America during the Late Cretaceous and Paleogene: Geology, v. 28, p. 243-246. Dewey, J.F., Shackleton, R.M., Chang, C.F., and Sun, Y.Y., 1988, The Tectonic Evolution of the Tibetan Plateau: Philosophical Transactions of the Royal Society of London Series a-Mathematical Physical and Engineering Sciences, v. 327, p. 379-413. Di Celma, C., and Cantalamessa, G., 2007, Sedimentology and high-frequency sequence stratigraphy of a forearc extensional basin: The Miocene Caleta Herradura Formation, Mejillones Peninsula, northern Chile: Sedimentary Geology, v. 198, p. 29-52. Dickinson, W., 1985, Provenance relations from detrital modes of sandstones, in Zuffa, G., ed., Provenace of Arenites: Dordrecht, D. Reidel Publishing Co., p. 333-361. Dickinson, W., Armin, R., Beckvar, N., Goodlin, T., Janecke, S., Mark, R., Norris, R., Radel, G., and Wortman, A., 1987, Geohistory Analysis of Rates of Sediment Accumulation and Subsidence for Selected California Basins, in Ingersoll, R., and Ernst, W., eds., Cenozoic Basin Development of Coastal California: Englewood Cliffs, Prentice Hall, p. 1-23. 284 Ding, L., Kapp, P., Zhong, D., and Deng, W., 2003, Cenozoic volcanism in Tibet: Evidence for a transition from oceanic to continental subduction: Journal of Petrology, v. 44, p. 1833-1865. Drever, J., 1997, The geochemistry of natural waters: surface and groundwater environments: Upper Saddle River, Prentive-Hall Inc. Drummond, C.N., Wilkinson, B.H., Lohmann, K.C., and Smith, G.R., 1993, Effect of regional topography and hydrology on the lacustrine isotopic record of Miocene paleoclimate in the Rocky Mountains: Palaeogeography Palaeoclimatology Palaeoecology, v. 101, p. 67-79. Dupont-Nivet, G., Hoorn, C., and Konert, M., in press, Tibetan uplift prior to the Eocene- Oligocene climate transition: Evidence from pollen analysis of the Zining Basin. Dupont-Nivet, G., Krijgsman, W., Langereis, C.G., Abels, H.A., Dai, S., and Fang, X.M., 2007, Tibetan plateau aridification linked to global cooling at the Eocene- Oligocene transition: Nature, v. 445, p. 635-638. Ehleringer, J., Sage, R., Flanagan, L., and Pearcy, R., 1991, Climate change and the evolution of C4 photosynthesis: Trends in ecology and evolution, v. 6, p. 95-99. Fielding, E., Isacks, B., Barazangi, M., and Duncan, C., 1994, How flat is Tibet: Geology, v. 22, p. 163-167. Fielding, E.J., 1996, Tibet uplift and erosion: Tectonophysics, v. 260, p. 55-84. Flynn, L.J., Barry, J.C., Morgan, M.E., Pilbeam, D., Jacobs, L.L., and Lindsay, E.H., 1995, Neogene Siwalik mammalian lineages: species longevities, rates of change, and modes of speciation: Palaeogeography Palaeoclimatology Palaeoecology, v. 115, p. 249-264. Flynn, L.J., Downs, W.R., Morgan, M.E., Barry, J.C., and Pilbeam, D., 1998, High Miocene species richness in the Siwaliks of Pakistan, in Tomida, Y., Flynn, L.J., and Jacobs, L.L., eds., Advances in Vertebrate Paleontology and Geochronology, Volume 14: National Science Museum Monographs: Tokyo, National Science Museum, p. 167-180. 285 Fontes, J.C., Gasse, F., and Gibert, E., 1996, Holocene environmental changes in Lake Bangong basin (western Tibet) .1. Chronology and stable isotopes of carbonates of a Holocene lacustrine core: Palaeogeography Palaeoclimatology Palaeoecology, v. 120, p. 25-47. Fox, D., and Koch, P., 2003, Tertiary history of C-4 biomass in the Great Plains, USA: Geology, v. 31, p. 809-812. France-Lanord, C., and Derry, L., 1994, Delta-C-13 of organice carbon in the Bengal Fan - source evolution and transport of C3 and C4 plant carbon to marine sediments: Geochimica et Cosmochimica Acta, v. 58, p. 4809-4814. Freeman, K., and Collarusso, L., 2001, Molecular and isotopic records of C-4 grassland expansion in the late Miocene: Geochimica et Cosmochimica Acta, v. 65, p. 1439-1454. Friedmann, S., and Burbank, D., 1995, Rift basins and supradetchment basins - Intracontinental extensional end-members: Basin Research, v. 7, p. 109-127. Fritz, P., and Poplawski, S., 1974, 0-18 and C-13 in shells of freshwater molluscks and their environments: Earth and Planetary Science Letters, v. 24, p. 91-98. Ganser, A., 1964, Geology of the Himalayas: London, Wiley InterScience, 289 p. Garzione, C., DeCelles, P., Hodkinson, D., Ojha, T., and Upreti, B., 2003, East-west extension and Miocene environmental change in the southern Tibetan plateau: Thakkhola graben, central Nepal: Geological Society of America Bulletin, v. 115, p. 3-20. Garzione, C., Dettman, D., and Horton, B., 2004, Carbonate oxygen isotope paleoaltimetry: evaluating the effect of diagenesis on paleoelevation estimates for the Tibetan plateau: Palaeogeography Palaeoclimatology Palaeoecology, v. 212, p. 119-140. Garzione, C., Dettman, D., Quade, J., DeCelles, P., and Butler, R., 2000a, High times on the Tibetan Plateau: Paleoelevation of the Thakkhola graben, Nepal: Geology, v. 28, p. 339-342. 286 Garzione, C., Quade, J., DeCelles, P., and English, N., 2000b, Predicting paleoelevation of Tibet and the Himalaya from delta O-18 vs. altitude gradients in meteoric water across the Nepal Himalaya: Earth and Planetary Science Letters, v. 183, p. 215- 229. Gasse, F., Arnold, M., Fontes, J.C., Fort, M., Gibert, E., Huc, A., Li, B.Y., Li, Y.F., Lju, Q., Melieres, F., Vancampo, E., Wang, F.B., and Zhang, Q.S., 1991, A 13,000- year climate record from western Tibet: Nature, v. 353, p. 742-745. Gawthorpe, R., and Hardy, S., 2002, Extensional fault-propagation folding and base-level change as controls on growth-strata geometries: Sedimentary Geology, v. 146, p. 47-56. Gehrels, G., 2000, Introduction to detrital zircons studies of Paleozoic and Triassic strata in western Nevada and northern California, in Soreghan, M., and Gehrels, G., eds., Paleozoic and Triassic paleogeography and tectonics of western Nevada and northern California, Volume Geological Society of America Special Paper 347, p. 1-17. Gehrels, G.E., DeCelles, P.G., Ojha, T.P., and Upreti, B.N., 2006a, Geologic and U-Pb geochronologic evidence for early Paleozoic tectonism in the Dadeldhura thrust sheet, far-west Nepal Himalaya: Journal of Asian Earth Sciences, v. 28, p. 385- 408. —, 2006b, Geologic and U-Th-Pb geochronologic evidence for early Paleozoic tectonism in the Kathmandu thrust sheet, central Nepal Himalaya: Geological Society of America Bulletin, v. 118, p. 185-198. Gehrels, G.E., Valencia, V.A., and Ruiz, J., 2008, Enhanced precision, accuracy, efficiency, and spatial resolution of U-Pb ages by laser ablation-multicollector- inductively coupled plasma-mass spectrometry: Geochemistry Geophysics Geosystems, v. 9. Gerbault, M., Martinod, J., and Herail, G., 2005, Possible orogeny-parallel lower crustal flow and thickening in the Central Andes: Tectonophysics, v. 399, p. 59-72. 287 Giovanoli, F., 1990, Horizontal transpot and sedimentationn by interflows and turbidity currents in Lake Geneva, in Tilzer, M., and Serruya, C., eds., Large Lakes: Ecological Structure and Function: Berlin, Springer-Verlag, p. 175-195. Gonfiantini, R., 1986, Environmental isotopes in lake studies, in Fritz, P., and Fontes, J., eds., The terrestrial environment: Amsterdam, Elsevier, p. 113-168. Graham, S., Chamberlain, C., Yue, Y., Ritts, B., Hanson, A., Horton, T., Waldbauer, J., Poage, M., and Feng, X., 2005, Stable isotope records of Cenozoic climate and topography, Tibetan plateau and Tarim basin: American Journal of Science, v. 305, p. 101-118. Grossman, E., and Ku, T., 1986, Oxygen and carbon isotope fractionation in biogenic aragonite: temperature effects: Chemical Geology, v. 59, p. 59-74. Guo, Z.T., Ruddiman, W.F., Hao, Q.Z., Wu, H.B., Qiao, Y.S., Zhu, R.X., Peng, S.Z., Wei, J.J., Yuan, B.Y., and Liu, T.S., 2002, Onset of Asian desertification by 22 Myr ago inferred from loess deposits in China: Nature, v. 416, p. 159-163. Gupta, A.K., Dhingra, H., Melice, J.L., and Anderson, D.M., 2001, Earth's Eccentricity Cycles and Indian Summer Monsoon variability over the past 2 million years: Evidence from deep-sea Benthic Foraminifer: Geophysical Research Letters, v. 28, p. 4131-4134. Gupta, S., Underhill, J.R., Sharp, I.R., and Gawthorpe, R.L., 1999, Role of fault interactions in controlling synrift sediment dispersal patterns: Miocene, Abu Alaqa Group, Suez Rift, Sinai, Egypt: Basin Research, v. 11, p. 167-189. Guynn, J.H., Kapp, P., Pullen, A., Heizier, M., Gehrels, G., and Ding, L., 2006, Tibetan basement rocks near Amdo reveal "missing" Mesozoic tectonism along the Bangong suture, central Tibet: Geology, v. 34, p. 505-508. Hailemichael, M., Aronson, J.L., Savin, S., Tevesz, M.J.S., and Carter, J.G., 2002, delta O-18 in mollusk shells from Pliocene Lake Hadar and modern Ethiopian lakes: implications for history of the Ethiopian monsoon: Palaeogeography Palaeoclimatology Palaeoecology, v. 186, p. 81-99. 288 Hampton, B.A., and Horton, B.K., 2007, Sheetflow fluvial processes in a rapidly subsiding basin, Altiplano plateau, Bolivia: Sedimentology, v. 54, p. 1121-1147. Harrison, T., Copeland, P., Kidd, W., and Yin, A., 1992, Raising Tibet: Science, v. 255, p. 1663-1670. Heinz, J., and Aigner, T., 2003, Hierarchical dynamic stratigraphy in various Quaternary gravel deposits, Rhine glacier area (SW Germany): implications for hydrostratigraphy: International Journal of Earth Sciences, v. 92, p. 923-938. Heinz, J., Kleineidam, S., Teutsch, G., and Aigner, T., 2003, Heterogeneity patterns of Quaternary glaciofluvial gravel bodies (SW-Germany): application to hydrogeology: Sedimentary Geology, v. 158, p. 1-23. Hodges, K., 2000, Tectonics of the Himalaya and southern Tibet from two perspectives: Geological Society of America Bulletin, v. 112, p. 324-350. Hodges, K., Parrish, R., and Searle, M., 1996, Tectonic evolution of the central Annapurna Range, Nepalese Himalayas: Tectonics, v. 15, p. 1264-1291. Hodges, K.V., Parrish, R.R., Housh, T.B., Lux, D.R., Burchfiel, B.C., Royden, L.H., and Chen, Z., 1992, Simultaneous Miocene extension and shortening in the Himalayan orogen: Science, v. 258, p. 1466-1470. Holbourn, A., Kuhnt, W., Schulz, M., Flores, J.A., and Andersen, N., 2007, Orbitally- paced climate evolution during the middle Miocene "Monterey" carbon-isotope excursion: Earth and Planetary Science Letters, v. 261, p. 534-550. Hoorn, C., Ohja, T., and Quade, J., 2000, Palynological evidence for vegetation development and climatic change in the Sub-Himalayan Zone (Neogene, Central Nepal): Palaeogeography Palaeoclimatology Palaeoecology, v. 163, p. 133-161. Hunter, R.E., 1977, Basic types of stratification in small eolian dunes: Sedimentology, v. 24, p. 361-387. 289 Hurtado, J.M., Hodges, K.V., and Whipple, K.X., 2001, Neotectonics of the Thakkhola graben and implications for recent activity on the South Tibetan fault system in the central Nepal Himalaya: Geological Society of America Bulletin, v. 113, p. 222-240. Ingersoll, R.V., Bullard, T.F., Ford, R.L., Grimm, J.P., Pickle, J.D., and Sares, S.W., 1984, The effect of grain size on detrital modes: A test of the Gazi-Dickinson point-counting method: Journal of Sedimentary Petrology, v. 54, p. 103-116. Jones, M., 1988, Photosynthetic responses of C3 and C4 wetland species in a tropical swamp: Journal of Ecology, v. 76, p. 253-262. Jian, Z., Huang, B., Kuhnt, W., and Lin, H.L., 2001, Late quaternary upwelling intensity and east Asian monsoon forcing in the South China Sea: Quaternary Research, v. 55, p. 363-370. Jopling, A.V., 1965, Hydraulic factors controlling shape of laminae in laboratory deltas: Journal of Sedimentary Petrology, v. 35, p. 777-&. Jouzel, J., Alley, R.B., Cuffey, K.M., Dansgaard, W., Grootes, P., Hoffmann, G., Johnsen, S.J., Koster, R.D., Peel, D., Shuman, C.A., Stievenard, M., Stuiver, M., and White, J., 1997, Validity of the temperature reconstruction from water isotopes in ice cores: Journal of Geophysical Research-Oceans, v. 102, p. 26471- 26487. Kang, S.C., Qin, D.H., Mayewski, P.A., Wake, C.P., and Ren, J.W., 2001, Climatic and environmental records from the Far East Rongbuk ice core, Mt. Qomolangma (Mt. Everest): Episodes, v. 24, p. 176-181. Kapp, P., and Guynn, J.H., 2004, Indian punch rifts Tibet: Geology, v. 32, p. 993-996. Kashiwaya, K., Ochiai, S., Sakai, H., and Kawai, T., 2001, Orbit-related long-term climate cycles revealed in a 12-Myr continental record from Lake Baikal: Nature, v. 410, p. 71-74. Kelly, S., 1993, Cyclical discharge variations recorded in alluvial sediments: an example from the Devonian of southwest Ireland, in North, C., and Prosser, D., eds., 290 Characterization of fluvial and aeolian reservoirs, Volume Special Publication vol. 73: London, eological Society of London, p. 157-166. Kelts, K., 1988, Environments of deposition of lacustrine petroleum source rocks: an introduction, in Fleet, A., Kelts, K., and Talbot, M., eds., Lacustrine Petroleum Source Rocks: Oxford, Geological Society Special Paper 40, p. 3-26. Kennett, J.P., 1985, The Miocene Ocean: paleoceanography and biogeography: Geological Society of America Memoir, p. i-vi, 1-337. Klootwijk, C.T., Conaghan, P.J., and Powell, C.M., 1985, The Himalayan arc - Large- scale continental subduction, oroclinal bending and back-arc spreading: Earth and Planetary Science Letters, v. 75, p. 167-183. Kroon, D., Steens, T., and Troelstra, S., 1991, Onset of monsoonal related upwelling in the western Arabian Sea as revealed by planktonic foraminifers. Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A.C.M., and Levrard, B., 2004, A long-term numerical solution for the insolation quantities of the Earth: Astronomy & Astrophysics, v. 428, p. 261-285. Latorre, C., Quade, J., and McIntosh, W., 1997, The expansion of C-4 grasses and global change in the late Miocene: Stable isotope evidence from the Americas: Earth and Planetary Science Letters, v. 146, p. 83-96. Leier, A., DeCelles, P., Kapp, P., and Ding, L., 2007, The takena formation of the Lhasa terrane, southern Tibet: The record of a Late Cretaceous retroarc foreland basin: Geological Society of America Bulletin, v. 119, p. 31-48. Lemeille, E., Letolle, R., Meliere, F., and Olive, P., 1983, Isotope and other physio- chemical parameters of palaeolake carbonates: tools for climatic reconstruction, Palaeoclimates and palaeowaters: a collection of environmental isotope studies: Vienna, International Atomic Energy Agency, p. 135-150. Leng, M.J., Lamb, A.L., Lamb, H.F., and Telford, R.J., 1999, Palaeoclimatic implications of isotopic data from modern and early Holocene shells of the freshwater snail 291 Melanoides tuberculata, from lakes in the Ethiopian Rift Valley: Journal of Paleolimnology, v. 21, p. 97-106. Li, F., and Li, D., 1990, Latest Miocene Hipparion (Plesiohipparion) of Zanda Basin, in Yang, Z., Nie, Z., and et. al., eds., Paleontology of the Ngari Area, Tibet (Xizang): Wuhan, China Geological University Press, p. 186-193. Li, H., and Ku, T., 1997, Delta C-13-delta O-18 covariance as a paleohydrological indicator for closed-basin lakes: Palaeogeography Palaeoclimatology Palaeoecology, v. 133, p. 69-80. Li, J., and Zhou, Y., 2001a, Palaeovegetation type analysis of the late Pliocene in Zanda basin of Tibet: Journal of Palaeogeography, v. 14, p. 52-58. —, 2001b, Pliocene palynoflora from the Zanda Basin west Xizang (Tibet), and the palaeoenvironment: Acta Micropalaeontologica Sinica, v. 18, p. 89-96. Li, T., Xiao, X., Li, G., Gao, Y., and Zhou, W., 1986, The crustal evolution and uplift mechanism of the Qinghai-Tibet plateau: Tectonophysics, v. 127, p. 279-289. Liu, D., 1981, Geological and ecological studies of Qinghai – Xizang Plateau: Beijing, Science Press. Liu, D.e., 1980, Geological and ecological studies of Qinghai – Xizang Plateau, in Liu, D., ed., Symposium on Qinghai-Xizang (Tibet) Plateau, Volume 2: Beijing, Science Press. Lourens, L., Hilgen, F., Shackleton, N., Laskar, J., and Wilson, D., 2004, The Neogene Period, in Gradstein, F., Ogg, J., and Smith, A., eds., A Geologic Time Scale: Cambridge, Cambridge University Press. Lowe, D., 1982, Sediment gravity flows .2. Depositional models with special reference to the deposits of high-density turbidity currents: Journal of Sedimentary Petrology, v. 52, p. 279-298. 292 Lowenstein, T., Li, J., and Brown, C., 1998, Paleotemperatures from fluid inclusions in halite: method verification and a 100,000 year paleotemperature record, Death Valley, CA: Chemical Geology, v. 150, p. 223-245. Lu, H.Y., Wu, N.Q., Gu, Z.Y., Guo, Z.T., Wang, L., Wu, H.B., Wang, G., Zhou, L.P., Han, J.M., and Liu, T.S., 2004, Distribution of carbon isotope composition of modern soils on the Qinghai-Tibetan Plateau: Biogeochemistry, v. 70, p. 273-297. Ludwig, K., 2003, Isoplot 3.0, Volume Special Publication No. 4: Berkeley, Berkeley Geochronology Center, p. 70. Lunt, I.A., Bridge, J.S., and Tye, R.S., 2004, A quantitative, three-dimensional depositional model of gravelly braided rivers: Sedimentology, v. 51, p. 377-414. Ma, Y., Li, J., and Fang, X., 1998, Pollen assemblage in 30.6 - 5.0 Ma redbeds in Linxia region and climate evolution: Chinese Science Bulletin, v. 43, p. 301-304. Majoube, M., 1971, Oxygen-18 and deuterium fractionation between water and steam: Journal de Chimie Physique et de Physico-Chimie Biologique, v. 68, p. 1423-&. Martin, A.J., DeCelles, P.G., Gehrels, G.E., Patchett, P.J., and Isachsen, C., 2005, Isotopic and structural constraints on the location of the Main Central thrust in the Annapurna Range, central Nepal Himalaya: Geological Society of America Bulletin, v. 117, p. 926-944. Martinelli, L., Devol, A., Victoria, R., and Richey, J., 1991, Stable isotope variation in C3 and C4 plants along the Amazon River: Nature, v. 353, p. 57-59. Mathur, Y., 1984, Cenozoic palynofossils, vegetation, ecology, and climate of the north and northwestern Subhimalayan region, in White, R., ed., The evolution of the east Asian environment, volume 2: Hong Kong, Centre for Asian Studies, University of Hong Kong, p. 504-551. McCaffrey, R., and Nabelek, J., 1998, Role of oblique convergence in the active deformation of the Himalayas and southern Tibet plateau: Geology, v. 26, p. 691- 694. 293 Meng, X., Zhu, D., Shao, Z., Yang, C., Sun, L., Wang, J., Han, T., Du, J., Han, J., and Yu, J., 2004, Discovery of rhinoceros fossils in the Pliocene in the Zanda basin, Ngari, Tibet: Geological Bulletin of China, v. 23, p. 609-612. Meng, X.G., Zhu, D.G., Shao, Z.G., Yang, C.B., Han, J.N., Yu, J., Meng, Q.W., and Lu, R.P., 2008, Late cenozoic stratigraphy and paleomagnetic chronology of the Zanda basin, Tibet, and records of the uplift of the Qinghai-Tibet Plateau: Acta Geologica Sinica-English Edition, v. 82, p. 63-72. Metcalfe, R., 1993, Pressure, temperature, and time constraints on metamorphism across the Main Central Thrust zone and high Himalayan slab in the Garhwal Himalaya, in treloar, P., and Searle, M., eds., Himalayan Tectonics, Volume 74, Geological Society Special Publication, p. 485-509. Miall, A., 1978, Lithofacies types and vertical profile models in braided river deposits: A Summary, in Miall, A., ed., Fluvial sedimentology, Volume 5, Memoirs of the Canadian Society of Petroleum Geologists, p. 597-604. —, 1996, The Geology of Fluvial Deposits: New York, Springer-Verlag, 581 p. —, 2000, Principles of Sedimentary Basin Analysis, Springer, 616 p. Molnar, P., 2005, Mio-pliocene growth of the Tibetan Plateau and evolution of East Asian climate: Palaeontologia Electronica, v. 8, p. -. Molnar, P., England, P., and Martinod, J., 1993, Mantle dynamics, uplift of the Tibetan plateau and the Indian monsoon: Reviews of Geophysics, v. 31, p. 357-396. Molnar, P., and Lyon-Caen, H., 1988, Some simples physical aspects of the support, structure, and evolution of mountain belts, in Clark, S.J., Burchfiel, B., and Suppe, J., eds., Processes in continental lithospheric deformation, Volume Special Paper 218, Geological Society of America, p. 179-207. Molnar, P., and Tapponnier, P., 1978, Active Tectonics of Tibet: Journal of Geophysical Research-Solid Earth and Planets, v. 83, p. 5361-&. 294 Mulder, T., Syvitski, J.P.M., Migeon, S., Faugeres, J.C., and Savoye, B., 2003, Marine hyperpycnal flows: initiation, behavior and related deposits. A review: Marine and Petroleum Geology, v. 20, p. 861-882. Murphy, M., 2007, Isotopic characteristics of the Gurla Mandhata metamorphic core complex: Implications for the architecture of the Himalayan orogen: Geology, v. 35, p. 983-986. Murphy, M., and Copeland, P., 2005, Transtensional deformation in the central Himalaya and its role in accommodating growth of the Himalayan orogen: Tectonics, v. 24, p. -. Murphy, M., and Yin, A., 2003, Structural evolution and sequence of thrusting in the Tethyan fold-thrust belt and Indus-Yalu suture zone, southwest Tibet: Geological Society of America Bulletin, v. 115, p. 21-34. Murphy, M., Yin, A., Harrison, T., Durr, S., Chen, Z., Ryerson, F., Kidd, W., Wang, X., and Zhou, X., 1997, Did the Indo-Asian collision alone create the Tibetan plateau?: Geology, v. 25, p. 719-722. Murphy, M., Yin, A., Kapp, P., Harrison, T., Manning, C., Ryerson, F., Ding, L., and Guo, J., 2002, Structural evolution of the Gurla Mandhata detachment system, southwest Tibet: Implications for the eastward extent of the Karakoram fault system: Geological Society of America Bulletin, v. 114, p. 428-+. Murphy, M.A., and Harrison, T.M., 1999, Relationship between leucogranites and the Qomolangma detachment in the Rongbuk Valley, south Tibet: Geology, v. 27, p. 831-834. Murphy, M.A., Yin, A., Kapp, P., Harrison, T.M., Lin, D., and Guo, J.H., 2000, Southward propagation of the Karakoram fault system, southwest Tibet: Timing and magnitude of slip: Geology, v. 28, p. 451-454. Mutti, E., Tinterri, R., Benevelli, G., di Biase, D., and Cavanna, G., 2003, Deltaic, mixed and turbidite sedimentation of ancient foreland basins: Marine and Petroleum Geology, v. 20, p. 733-755. 295 Nakagawa, T., Okuda, M., Yonenobu, H., Miyoshi, N., Fujiki, T., Gotanda, K., Tarasov, P.E., Morita, Y., Takemura, K., and Horie, S., 2008, Regulation of the monsoon climate by two different orbital rhythms and forcing mechanisms: Geology, v. 36, p. 491-494. NCDC, 2007, National Climatic Data Center, Volume 2007, National Climatic Data Center. Nemec, W., and Steel, R., 1984, Alluvial and coastal conglomerates: Their significant features and some comments on gravelly mass-flow deposits, in Kloster, E., and Steel, R., eds., Sedimentology of gravels and conglomerates, Volume Memoir 10, Canadian Society of Petroleum Geologists, p. 1-31. Ni, J., and Barazangi, M., 1985, Active tectonics of the western Tethyan Himalaya above the underthrusting Indian plate - The Upper Sutlej River Basin as a pull-apart structure: Tectonophysics, v. 112, p. 277-295. Ni, J., and York, J.E., 1978, Late Cenozoic tectonics of Tibetan Plateau: Journal of Geophysical Research, v. 83, p. 5377-5384. Nie, J.S., King, J.W., and Fang, X.M., 2008, Tibetan uplift intensified the 400 k.y. signal in paleoclimate records at 4 Ma: Geological Society of America Bulletin, v. 120, p. 1338-1344. Ojha, T., Butler, R., Quade, J., DeCelles, P., Richards, D., and Upreti, B., 2000, Magnetic polarity stratigraphy of the Neogene Siwalik Group at Khutia Khola, far western Nepal: Geological Society of America Bulletin, v. 112, p. 424-434. Pagani, M., Freeman, K., and Arthur, M., 1999, Late Miocene atmospheric CO2 concentrations and the expansion of C-4 grasses: Science, v. 285, p. 876-879. Patnaik, R., 2003, Reconstruction of Upper Siwalik palaeoecology and palaeoclimatology using microfossil palaeocommunities: Palaeogeography Palaeoclimatology Palaeoecology, v. 197, p. 133-150. Pearson, P.N., Ditchfield, P., and Shackleton, N.J., 2002, Palaeoclimatology - Tropical temperatures in greenhouse episodes - Reply: Nature, v. 419, p. 898-898. 296 Pierson, T., 1980, Erosion and deposition by debris flows at Mt Thomas, North- Canterbury, New-Zealand: Earth Surface Processes and Landforms, v. 5, p. 227- 247. —, 1981, Dominant particle support mechanisms in debris flows at Mt Thomas, New- Zealand, and implications for flow mobility: Sedimentology, v. 28, p. 49-60. Pietras, J., and Carroll, A., 2006, High-resolution stratigraphy of an underfilled lake basin: Wilkins Peak Member, Eocene Green River Formation, Wyoming, USA: Journal of Sedimentary Research, v. 76, p. 1197-1214. Pilbeam, D., Morgan, M., Barry, J., and Flynn, L., 1996, European MN units and the Siwalik faunal sequence of Pakistan, in Bernor, R., Fahlbusch, V., and Mittmann, H., eds., The evolution of western Eurasian Neogene mammal faunas: New York, Columbia University Press, p. 96-105. Pivnik, D.A., 1990, Thrust-generated fan-delta deposition - Little Muddy Creek Conglomerate, SW Wyoming: Journal of Sedimentary Petrology, v. 60, p. 489- 503. Poage, M., and Chamberlain, C., 2001, Empirical relationships between elevation and the stable isotope composition of precipitation and surface waters: Considerations for studies of paleoelevation change: American Journal of Science, v. 301, p. 1-15. Posamentier, H., and Allen, G., 1999, Siliciclastic sequence stratigraphy: concepts and applications, Volume Concepts in Sedimentology and Paleontology, SEPM, p. 210. Postma, G., 1983, Water escape structures in the context of a depositional model of a mass-flow dominated conglomeratic fan-delta (Abrioka Formation, Pliocene, Almeria Basin, SE Spain): Sedimentology, v. 30, p. 91-103. Prell, W., and Kutzbach, J., 1992, Sensitivity of the Indian monsoon to forcing parameters and implications for its evolution: Nature, v. 360, p. 647-652. 297 Prasad, M., 1993, Siwalik (middle Miocene) woods from the Kalagarh area in the Himalayan foot hills and their bearing on paleoclimate and phytogeography: Review of Palaeobotany and Palynology, v. 76, p. 49-82. Prell, W., Murray, D., Clemens, S., and Anderson, D., 1992, Evolution and variability of the Indian Ocean summer monsoon: evidence from the western Arabian Sea drilling program, in Duncan, R., ed., Synthesis of Results from the Scientific Drilling of the Indian Ocean: Washington, DC, AGU, p. 447-469. Purton, L., and Brasier, M., 1997, Gastropod carbonate delta O-18 and delta C-13 values record strong seasonal productivity and stratification shifts during the late Eocene in England: Geology, v. 25, p. 871-874. Quade, J., Cater, J., Ojha, T., Adam, J., and Harrison, T., 1995, Late Miocene environmental change and in Nepal and the northern Indian subcontinent; stable isotopic evidence from paleosols: Geological Society of America Bulletin, v. 107, p. 1381-1397. Quade, J., Cerling, T., and Bowman, J., 1989, Development of Asian monsoon revealed by marked ecological shift during the latest Miocene in northern Pakistan: Nature, v. 342, p. 163-166. Ratschbacher, L., Frisch, W., Liu, G., and Chen, C., 1994, Distributed deformation in southern and western Tibet during and after the India-Asian collision: Journal of Geophysical Research-Solid Earth and Planets, v. 99, p. 19917-19945. Raymo, M.E., and Ruddiman, W.F., 1992, Tectonic forcing of Late Cenozoic climate: Nature, v. 359, p. 117-122. Robinson, D., DeCelles, P., and Copeland, P., 2006, Tectonic evolution of the Himalayan thrust belt in western Nepal: Implications for channel flow models: Geological Society of America Bulletin, v. 118, p. 865-885. Robinson, D., DeCelles, P., Garzione, C., Pearson, O., Harrison, T., and Catlos, E., 2003, Kinematic model for the Main Central thrust in Nepal: Geology, v. 31, p. 359- 362. 298 Rowley, D., and Currie, B., 2006, Palaeo-altimetry of the late Eocene to Miocene Lunpola basin, central Tibet: Nature, v. 439, p. 677-681. Rowley, D., and Garzione, C., 2007, Stable isotope-based paleoaltimetry: Annual Review of Earth and Planetary Sciences, v. 35, p. 463-508. Rowley, D., Pierrehumbert, R., and Currie, B., 2001, A new approach to stable isotope- based paleoaltimetry: implications for paleoaltimetry and paleohypsometry of the High Himalaya since the Late Miocene: Earth and Planetary Science Letters, v. 188, p. 253-268. Royden, L.H., Burchfiel, B.C., King, R.W., Wang, E., Chen, Z.L., Shen, F., and Liu, Y.P., 1997, Surface deformation and lower crustal flow in eastern Tibet: Science, v. 276, p. 788-790. Rozanski, K., Araguas-Araguas, L., and Gonfiantini, R., 1993, Isotopic patterns in modem global precipitation, in Swart, P., Lohman, K., McKenzie, J., and Savin, S., eds., Climate Change in Continental Isotopic Records - Geophysical Monograph 78: Washington, D.C., American Geophysical Union, p. 1-36. Ruddiman, W., Raymo, M., Prell, W., and Kutzback, J., 1997, The uplift-climate connection: a synthesis, in Ruddiman, W., ed., Tectonic Uplift and climate change: New York, Plenum Press, p. 471-515. Saez, A., Anadon, P., Herrero, M.J., and Moscariello, A., 2007, Variable style of transition between Palaeogene fluvial fan and lacustrine systems, southern Pyrenean foreland, NE Spain: Sedimentology, v. 54, p. 367-390. Sarkar, S., 1989, Siwalik pollen succession from Surai Khola of western Nepal and its reflection on paleoecology: Paleobotanist, v. 38, p. 319-324. Savin, S.M., Abel, L., Barrera, E., Hodell, D., Keller, G., Kennett, J.P., Killingley, J., Murphy, M., and Vincent, E., 1985, The evolution of Miocene surface and near- surface marine temperatures: oxygen isotopic evidence: Geological Society of America Memoir, p. 49-82. 299 Saylor, J., DeCelles, P., Gehrels, G., Murphy, M., Zhang, R., and Kapp, P., in review, Basin formation due to arc-parallel extension and tectonic damming: Zhada basin, SW Tibet. Saylor, J., Quade, J., Dettman, D., DeCelles, P., Kapp, P., and Ding, L., in press, The late Miocene through present paleoelevation history of southwestern Tibet: American Journal of Science. Schulz, M., and Stattegger, K., 1997, SPECTRUM: Spectral analysis of unevenly spaced paleoclimatic time series: Computers & Geosciences, v. 23, p. 929-945. Searle, M.P., Parrish, R.R., Hodges, K.V., Hurford, A., Ayres, M.W., and Whitehouse, M.J., 1997, Shisha Pangma leucogranite, south Tibetan Himalaya: Field relations, geochemistry, age, origin, and emplacement: Journal of Geology, v. 105, p. 295- 317. Searle, M.P., Simpson, R.L., Law, R.D., Parrish, R.R., and Waters, D.J., 2003, The structural geometry, metamorphic and magmatic evolution of the Everest massif, High Himalaya of Nepal-South Tibet: Journal of the Geological Society, v. 160, p. 345-366. Seeber, L., and Armbruster, J.G., 1984, Some elements of continental subduction along the Himalayan front: Tectonophysics, v. 105, p. 263-278. Seeber, L., and Pecher, A., 1998, Strain partitioning along the Himalayan arc and the Nanga Parbat antiform: Geology, v. 26, p. 791-794. Sengor, A., and Natal'in, B., 1996, Paleotectonics of Asia: Fragments of a synthesis, in Yin, A., and Harrison, T., eds., The Tectonics of Asia: Cambridge, Cambridge University Press, p. 486-640. Shanahan, T.M., Pigati, J.S., Dettman, D.L., and Quade, J., 2005, Isotopic variability in the aragonite shells of freshwater gastropods living in springs with nearly constant temperature and isotopic composition: Geochimica Et Cosmochimica Acta, v. 69, p. 3949-3966. 300 Sharp, I.R., Gawthorpe, R.L., Underhill, J.R., and Gupta, S., 2000, Fault-propagation folding in extensional settings: Examples of structural style and synrift sedimentary response from the Suez rift, Sinai, Egypt: Geological Society of America Bulletin, v. 112, p. 1877-1899. Shi, Y.F., Yu, G., Liu, X.D., Li, B.Y., and Yao, T.D., 2001, Reconstruction of the 30-40 ka BP enhanced Indian monsoon climate based on geological records from the Tibetan Plateau: Palaeogeography Palaeoclimatology Palaeoecology, v. 169, p. 69-83. Siegenthaler, U., and Oeschger, H., 1980, Correlation of 18O in precipitation with temperature and altitude: Nature, v. 285, p. 314-317. Sladen, C., 1994, Key elements during the search for hydrocarbons in lake systems, in Gierlowski-Kordesch, E., and Kelts, K., eds., Global Geological Record of Lake Basins Vol. 1: Cambridge, Cambridge University Press, p. 3-17. Smith, J.R., Giegengack, R., and Schwarcz, H.P., 2004, Constraints on Pleistocene pluvial climates through stable-isotope analysis of fossil-spring tufas and associated gastropods, Kharga Oasis, Egypt: Palaeogeography Palaeoclimatology Palaeoecology, v. 206, p. 157-175. Sohn, Y., 1997, On traction-carpet sedimentation: Journal of Sedimentary Research, v. 67, p. 502-509. Spicer, R., Harris, N., Widdowson, M., Herman, A., Guo, S., Valdes, P., Wolfe, J., and Kelley, S., 2003, Constant elevation of southern Tibet over the past 15 million years: Nature, v. 421, p. 622-624. Stacey, J.S., and Kramers, J.D., 1975, Approximation of terrestrial lead isotope evolution by a two-stage model: Earth and Planetary Science Letters, v. 26, p. 207-221. Stewart, D.R.M., Pearson, P.N., Ditchfield, P.W., and Singano, J.M., 2004, Miocene tropical Indian Ocean temperatures: evidence from three exceptionally preserved foraminiferal assemblages from Tanzania: Journal of African Earth Sciences, v. 40, p. 173-190. 301 Talbot, M.R., 1990, A review of the paleohydrological interpretation of carbon and oxygen isotopic-ratios in primary lacustrine carbonates: Chemical Geology, v. 80, p. 261-279. Talbot, M., and Allen, P., 1996, Lakes, in Reading, H., ed., Sedimentary Environments: Processes, Facies and Stratigraphy: Oxford, Blackwell Science Inc., p. 83-124. Tapponnier, P., Xu, Z.Q., Roger, F., Meyer, B., Arnaud, N., Wittlinger, G., and Yang, J.S., 2001, Geology - Oblique stepwise rise and growth of the Tibet plateau: Science, v. 294, p. 1671-1677. Taylor, M., Yin, A., Ryerson, F., Kapp, P., and Ding, L., 2003, Conjugate strike-slip faulting along the Bangong-Nujiang suture zone accommodates coeval east-west extension and north-south shortening in the interior of the Tibetan Plateau: Tectonics, v. 22, p. -. Thiede, R., Arrowsmith, J., Bookhagen, B., McWilliams, M., Sobel, E., and Strecker, M., 2005, From tectonically to erosionally controlled development of the Himalayan orogen: Geology, v. 33, p. 689-692. —, 2006, Dome formation and extension in the Tethyan Himalaya, Leo Pargil, northwest India: Geological Society of America Bulletin, v. 118, p. 635-650. Thompson, L.G., Yao, T., Davis, M.E., Henderson, K.A., MosleyThompson, E., Lin, P.N., Beer, J., Synal, H.A., ColeDai, J., and Bolzan, J.F., 1997, Tropical climate instability: The last glacial cycle from a Qinghai-Tibetan ice core: Science, v. 276, p. 1821-1825. Thompson, L.G., Yao, T., Mosley-Thompson, E., Davis, M.E., Henderson, K.A., and Lin, P.N., 2000, A high-resolution millennial record of the South Asian Monsoon from Himalayan ice cores: Science, v. 289, p. 1916-1919. Tian, L., Yao, T., Numaguti, A., and Sun, W., 2001, Stable isotope variations in monsoon precipitation on the Tibetan Plateau: Journal of the Meteorological Society of Japan, v. 79, p. 959-966. 302 Todd, S., 1989, Stream-driven, high-density gravelly traction carpets - Possible deposits in the Trabeg Conglomerate Formation, SW Ireland and some theoretical considerations of their origin: Sedimentology, v. 36, p. 513-530. Turner, S., Hawkesworth, C., Liu, J., Rogers, N., Kelley, S., and van Calsteren, P., 1993, Timing of Tibetan uplift constrained by analysis of volcanic rocks: Nature, v. 364, p. 50-54. Vail, P., Audemard, F., Bowman, S., Eisner, P., and Perez-Cruz, C., 1991, The stratigraphic signatures of tectonics, eustasy and sedimentology - an overview, in Einsele, G., and Ricken, W.S., A, eds., Cycles and Events in Stratigraphy: Berlin, Springer-Verlag, p. 617-659. Vail, P., Mitchum, R.J., and Thompson, S.I., 1977, Seismic stratigraphy and global changes of sea level, part four: global cycles of relative changes of sea level, American Association of Petroleum Geologists Memoir, Volume 26, p. 83-98. Valli, F., Arnaud, N., Leloup, P.H., Sobel, E.R., Maheo, G., Lacassin, R., Guillot, S., Li, H., Tapponnier, P., and Xu, Z., 2007, Twenty million years of continuous deformation along the Karakorum fault, western Tibet: A thermochronological analysis: Tectonics, v. 26. Van Wagoner, J., Posamentier, H., Mitchum, R.J., Vail, P., Sarg, J., Loutit, T., and Hardenbol, J., 1988, An overview of the fundamentals of sequence stratigraphy and key definitions, in Wilgus, C., Hastings, B., Ross, C., Posamentier, H., Van Wagoner, J., and Kendall, C., eds., Sea-level changes: An integrated approach, Volume Special Publication 42, SEPM, p. 39-45. Vanhinte, J.E., 1978, Geo-history analysis - Application of micro-paleontology in exploration geology: Aapg Bulletin-American Association of Petroleum Geologists, v. 62, p. 201-222. Vannay, J., Grasemann, B., Rahn, M., Frank, W., Carter, A., Baudraz, V., and Cosca, M., 2004, Miocene to Holocene exhumation of metamorphic crustal wedges in the NW Himalaya: Evidence for tectonic extrusion coupled to fluvial erosion: Tectonics, v. 23, p. -. 303 Wan, S.M., Li, A.C., Clift, P.D., and Stuut, J.B.W., 2007, Development of the East Asian monsoon: Mineralogical and sedimentologic records in the northern South China Sea since 20 Ma: Palaeogeography Palaeoclimatology Palaeoecology, v. 254, p. 561-582. Wang, J.H., Yin, A., Harrison, T.M., Grove, M., Zhang, Y.Q., and Xie, G.H., 2001, A tectonic model for Cenozoic igneous activities in the eastern Indo-Asian collision zone: Earth and Planetary Science Letters, v. 188, p. 123-133. Wang, P.X., Clemens, S., Beaufort, L., Braconnot, P., Ganssen, G., Jian, Z.M., Kershaw, P., and Sarnthein, M., 2005, Evolution and variability of the Asian monsoon system: state of the art and outstanding issues: Quaternary Science Reviews, v. 24, p. 595-629. Wang, R., 2003, C-4 plants in the vegetation of Tibet, China: Their natural occurrence and altitude distribution pattern: Photosynthetica, v. 41, p. 21-26. Wang, S.F., Blisniuk, P., Kempf, O., Fang, X.M., Chun, F., and Wang, E., 2008a, The basin-range system along the south segment of the Karakorum fault zone, Tibet: International Geology Review, v. 50, p. 121-134. Wang, S.F., Zhang, W.L., Fang, X.M., Dai, S., and Kempf, O., 2008b, Magnetostratigraphy of the Zanda basin in southwest Tibet Plateau and its tectonic implications: Chinese Science Bulletin, v. 53, p. 1393-1400. Wang, W., Zhang, J., and Zhang, B., 2004, Structural and sedimentary features in Zanda Basin of Tibet: Acta Scientiarum Naturalium, v. 40, p. 872-878. Wang, Y., Deng, T., and Biasatti, D., 2006, Ancient diets indicate significant uplift of southern Tibet after ca. 7 Ma: Geology, v. 34, p. 309-312. Wang, Y., Kromhout, E., Zhang, C., Xu, Y., Parker, W., Deng, T., and Qiu, Z., 2008c, Stable isotopic variations in modern herbivore tooth enamel, plants and water on the Tibetan Plateau: Implications for paleoclimate and paleoelevation reconstructions: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 260, p. 359-374. 304 Wang, Y.J., Cheng, H., Edwards, R.L., Kong, X.G., Shao, X.H., Chen, S.T., Wu, J.Y., Jiang, X.Y., Wang, X.F., and An, Z.S., 2008d, Millennial- and orbital-scale changes in the East Asian monsoon over the past 224,000 years: Nature, v. 451, p. 1090-1093. Weedon, G., 2003, Time-series analysis and cyclostratigraphy: Examining stratigraphic records of environmental cycles: Cambridge, Cambridge University Press. Williams, M., Haywood, A.M., Taylor, S.P., Valdes, P.J., Sellwood, B.W., and Hillenbrand, C.D., 2005, Evaluating the efficacy of planktonic foraminifer calcite delta O-18 data for sea surface temperature reconstruction for the Late Miocene: Geobios, v. 38, p. 843-863. Woodburne, M., Bernor, R., and Swisher, C.I., 1996, An appraisal of the stratigraphic and phylogenetic bases for the ―Hipparion‖ Datum in the Old World, in Bernor, R., Fahlbusch, V., and Mittmann, H., eds., The evolution of western Eurasian Neogene mammal faunas: New York, Columbia University Press, p. 124-136. Xu, R., 1981, Vegetational changes in the past and the uplift of the Qinghai-Xizang plateau, in Liu, D., ed., Geological and ecological studies of Qinghai – Xizang Plateau, Volume 1: Beijing, Science Press. Yang, W., Spencer, R., Krouse, H., Lowenstein, T., and Cases, E., 1995, Stable isotopes of lake and fluid inclusion brines, Dabusun Lake, Qaidam Basin, western China - Hydrology and paleoclimatology in arid environments: Palaeogeography Palaeoclimatology Palaeoecology, v. 117, p. 279-290. Yin, A., and Harrison, T., 2000, Geologic evolution of the Himalayan-Tibetan orogen: Annual Review of Earth and Planetary Sciences, v. 28, p. 211-280. Yin, A., Harrison, T., Murphy, M., Grove, M., Nie, S., Ryerson, F., Feng, W., and Le, C., 1999, Tertiary deformation history of southeastern and southwestern Tibet during the Indo-Asian collision: Geological Society of America Bulletin, v. 111, p. 1644- 1664. Yin, A., 2006, Cenozoic tectonic evolution of the Himalayan orogen as constrained by along-strike variation of structural geometry, exhumation history, and foreland sedimentation: Earth-Science Reviews, v. 76, p. 1-131. 305 Yoshida, M., Igarashi, Y., Arita, K., Hayashi, D., and Sharma, T., 1984, Magnetostratigraphic and pollen analytic studies of the Takmar series, Nepal Himalayas: Nepal Geological Society Journal, v. 4, p. 101-120. Yu, J., Luo, P., Han, J.-e., Meng, Q.-w., Lu, R.-p., Meng, X.-g., Zhu, D.-g., and Shao, Z.- g., 2007, Sporopollen records from the Guge section of the Zanda basin, Tibet, and paleoenvironmental information reflected by it: Geology in China, v. 34, p. 55-60. Zachos, J., Pagani, M., Sloan, L., Thomas, E., and Billups, K., 2001, Trends, rhythms, and aberrations in global climate 65 Ma to present: Science, v. 292, p. 686-693. Zachos, J.C., Arthur, M.A., Bralower, T.J., and Spero, H.J., 2002, Palaeoclimatology - Tropical temperatures in greenhouse episodes: Nature, v. 419, p. 897-898. Zhang, J., Ding, L., Zhong, D., and Zhou, Y., 2000, Orogen-parallel extension in Himalaya: Is it the indicator of collapse or the product in process of compressive uplift?: Chinese Science Bulletin, v. 45, p. 114-120. Zhang, Q., Wang, F., Ji, H., and Huang, W., 1981, Pliocene sediments of the Zanda basin, Tibet: Journal of Stratigraphy, v. 5, p. 216-220. Zheng, H., Powell, C., An, Z., Zhou, J., and Dong, G., 2000, Pliocene uplift of the northern Tibetan Plateau: Geology, v. 28, p. 715-718. Zhisheng, A., Kutzbach, J., Prell, W., and Porter, S., 2001, Evolution of Asian monsoons and phased uplift of the Himalayan Tibetan plateau since Late Miocene times: Nature, v. 411, p. 62-66. Zhou, Y., Ding, L., Deng, W., and Zhang, J., 2000, Tectonic cyclothems in the Zanda Basin and its significance: Scientia Geological Sinica, v. 35, p. 305-315. Zhu, D., Meng, X., Shoa, Z., Yang, C., Han, J., Yu, J., Meng, Q., and Lu, R., 2006, Early Pleistocene deposits and paleoclimatic and paleoenvironmental changes in the Zanda Basin, Ngari area, Tibet: Geology in China, v. 33, p. 1276-1284. 306 —, 2007, Evolution of the paleovegatation, paleoenvironment and paleoclimate during Pliocene - early Pleistocene in Zhada Basin, Ali, Tibet: Acta Geologica Sinica, v. 81, p. 295-306. Zhu, D., Meng, X., Shoa, Z., Yang, C., Sun, L., Wang, J., Han, T., Han, J., Du, J., Yu, J., and Meng, Q., 2004, Features of Pliocene - lower Pleistocene sedimentary facies and tectonic evolution in the Zanda Basin, Ngari area, Tibet: Journal of Geomechanics, v. 110, p. 245-252.