LAKE SEDIMENT RECORDS EXAMINING THE SPATIAL AND TEMPORAL CONNECTIONS OF HUMAN ACTIVITY AND CLIMATE CHANGE IN SOUTHWESTERN CHINA by Aubrey L. Hillman B.S., University of Maryland Baltimore County, 2009 B.A., University of Maryland Baltimore County, 2009 M.S., University of Pittsburgh, 2011 Submitted to the Graduate Faculty of the Kenneth P. Dietrich School of Arts and Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Pittsburgh 2015 UNIVERSITY OF PITTSBURGH DIETRICH SCHOOL OF ARTS AND SCIENCES This thesis was presented by Aubrey L. Hillman It was defended on March 27, 2015 and approved by Daniel Bain, Ph.D., Assistant Professor, Geology and Planetary Science Emily Elliott Ph.D., Associate Professor, Geology and Planetary Science Brian Stewart, Ph.D., Associate Professor, Geology and Planetary Science Loukas Barton, Ph.D., Assistant Professor, Anthropology Dissertation Director: Mark Abbott, Ph.D., Professor and Chair, Geology and Planetary Science ii Copyright © by Aubrey Hillman 2015 iii LAKE SEDIMENT RECORDS EXAMINING THE SPATIAL AND TEMPORAL CONNECTIONS OF HUMAN ACTIVITY AND CLIMATE CHANGE IN SOUTHWESTERN CHINA Aubrey Hillman, Ph.D. University of Pittsburgh, 2015 In regions of the world with long histories of human occupation, both natural environmental change and anthropogenic activities have impacted lake sediment dynamics over several millennia. The Yunnan Plateau of southwestern China is primarily impacted by the Indian Summer Monsoon (ISM) whose variability controls hydrologic balance. Despite the importance of the ISM as a critical water resource, we lack continuous terrestrial records of the ISM over a wide enough spatial gradient to understand its variability over multi-decadal time scales. Yunnan also has an extensive history of settlement, agriculture, and mineral resource extraction next to lakes, creating challenges in separating the impacts of recent disturbance from earlier activities. This dissertation will 1) establish records of anthropogenic impacts to lake sediment dynamics, 2) create records of hydrologic balance from lakes to understand ISM variability over the Holocene/Pleistocene, and 3) examine the intersection between climate variability and human activity around lakes to examine societal responses to changing water availability. Utilizing a multi-proxy approach, including sedimentology and stratigraphy, stable isotopes of authigenic carbonate minerals and organic matter, and trace element geochemistry, this research characterizes the nature, timing, and magnitude of both anthropogenic disturbance and climate variability to four lakes in Yunnan: Xing Yun, Erhai, Chenghai, and Dian. Results iv show that prior to ~2,000 years BP, shifts in hydrologic balance are generally in phase with insolation forcing. Several abrupt drops in ISM strength are inferred over the Holocene and agree with other records of ISM variability from the Tibetan Plateau. Over the last 2,000 years, records of climatic change are overwritten by pre-industrial human activities including soil erosion, eutrophication, heavy metal pollution, and hydrologic modification. The scale of such activities is either equal or greater than modern-day impacts, suggestive of a several millenia legacy that likely contributes to contemporary environmental challenges. v TABLE OF CONTENTS PREFACE ............................................................................................................................. XXVII 1.0 INTRODUCTION ........................................................................................................ 1 1.1 OBJECTIVES ........................................................................................................... 1 1.1.1 Research Aims.................................................................................................. 1 1.1.2 Research Questions.......................................................................................... 4 1.1.3 Hypotheses ........................................................................................................ 6 1.2 REGIONAL SETTING ............................................................................................ 7 1.2.1 Geology ............................................................................................................. 7 1.2.2 Climate ............................................................................................................ 10 1.3 HUMAN HISTORY OF THE YUNNAN PROVINCE ...................................... 18 1.4 LACUSTRINE SEDIMENTS AS ENVIRONMENTAL ARCHIVES .............. 22 2.0 XING YUN LAKE ..................................................................................................... 28 2.1 REGIONAL SETTING .......................................................................................... 29 2.2 MATERIALS AND METHODS ........................................................................... 31 2.2.1 Core collection ................................................................................................ 31 2.2.2 Age Control .................................................................................................... 31 2.2.3 Geochemistry ................................................................................................. 32 2.3 RESULTS AND DISCUSSION ............................................................................. 34 2.3.1 Core Chronology............................................................................................ 34 vi 2.3.2 Sedimentology ................................................................................................ 37 2.3.3 Geochemistry ................................................................................................. 44 2.3.3.1 Unit I- Pre-human disturbance .............................................................. 44 2.3.3.2 Transition period ..................................................................................... 46 2.3.3.3 Unit II- Intensive human disturbance .................................................... 51 2.4 CONCLUSION ....................................................................................................... 57 3.0 XING YUN LAKE- LONG CORE ........................................................................... 58 3.1 BACKGROUND ..................................................................................................... 60 3.1.1 Regional Setting ............................................................................................. 60 3.1.2 Previous Paleoclimate Studies ...................................................................... 62 3.2 MATERIALS AND METHODS ........................................................................... 66 3.2.1 Core collection ................................................................................................ 66 3.2.2 Age Control .................................................................................................... 66 3.2.3 Geochemistry ................................................................................................. 67 3.3 RESULTS ................................................................................................................ 69 3.3.1 Core Chronology............................................................................................ 69 3.3.2 Sedimentology and Geochemistry ................................................................ 73 3.3.2.1 Unit I- >50 to 42 ka .................................................................................. 76 3.3.2.2 Unit II- 42 to 33 ka ................................................................................... 76 3.3.2.3 Unit III- 33 to 17 ka ................................................................................. 77 3.3.2.4 Unit IV- 7.8 to 1.5 ka ................................................................................ 77 3.3.2.4.1 Subunit I- 7.8 to 6.6 ka ...................................................................... 79 vii 3.3.2.4.2 Subunit II- 6.6 to 4.7 ka .................................................................... 81 3.3.2.4.3 Subunit III- 4.7 to 2.95 ka ................................................................. 81 3.3.2.4.4 Subunit IV- 2.95 to 1.5 ka ................................................................. 82 3.4 DISCUSSION .......................................................................................................... 82 3.4.1 Unit I- >50 to 42 ka ........................................................................................ 82 3.4.2 Unit II- 42 to 33 ka ......................................................................................... 84 3.4.3 Unit III- 33 to 17 ka ....................................................................................... 85 3.4.4 Unit IV- 7.8 to 1.5 ka ..................................................................................... 89 3.4.4.1 Subunit I- 7.8 to 6.6 ka ............................................................................ 93 3.4.4.2 Subunit II- 6.6 to 4.7 ka ........................................................................... 96 3.4.4.3 Subunit III- 4.7 to 2.95 ka ....................................................................... 97 3.4.4.4 Subunit IV- 2.95 to 1.5 ka........................................................................ 99 3.5 CONCLUSION ....................................................................................................