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Stratigraphy, Geochronology, and Geochemistry Of Stratigraphy, Geochronology and Geochemistry of Paleolakes on the Southern Bolivian Altiplano Item Type text; Electronic Dissertation Authors Placzek, Christa Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 08/10/2021 00:18:37 Link to Item http://hdl.handle.net/10150/194352 STRATIGRAPHY, GEOCHRONOLOGY, AND GEOCHEMISTRY OF PALEOLAKES ON THE SOUTHERN BOLIVIAN ALTIPLANO by Christa Placzek ______________________ A Dissertation submitted to the Faculty of the DEPARTMENT OF GEOSCIENCES In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSPHY In the Graduate College THE UNIVERSITY OF ARIZONA 2005 2 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE As members of the Dissertation Committee, we certify that we have read the dissertation prepared by Christa J Placzek entitled Stratigraphy, geochronology, and geochemistry of paleolakes on the southern Bolivian Altiplano and recommend that it be accepted as fulfilling the dissertation requirement for the Degree of Doctor of Philosophy _______________________________________________________________________ Date: 10/08/05 Jay Quade _______________________________________________________________________ Date: 10/08/05 P. Jonathan Patchett _______________________________________________________________________ Date: 10/08/05 Julia E. Cole _______________________________________________________________________ Date: 10/08/05 Jon D. Pelletier 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: 10/08/05 Dissertation Directors: Jay Quade, P. Jonathan Patchett 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 or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interest of scholarship. In all other instances, however, permission must be obtained from the author. SIGNED: Christa Placzek 4 ACKNOWLEDGMENTS This dissertation would not be possible without the direction of both my advisors, Jon Patchett and Jay Quade. Jay and Jon were instrumental in collecting data, refining questions, and obtaining funding. For all of this I am truly grateful. I found Jay’s guidance in the field invaluable. Jay’s enthusiastic and hard work in Bolivia, Peru, and Chile set a high bar for myself and everyone else who works with him. His insights and intuition in the field are an invaluable addition to this dissertation. Likewise, I wish to acknowledge Jon’s mentorship in the laboratory; I can think of no better opportunity for a graduate student then to set up laboratory procedures with such a competent and meticulous chemist as Jon. I have also benefited greatly from the mentorship of Julio Betancourt. Indeed, my interest in South American paleoclimate began with my master’s work, a project directed by Jay and Julio. I have benefited both personally and professionally from numerous discussions with Julio. I also wish to thank the other members of the Desert Lab research group: Tim Fischer, Bill Hart, Camille Holmgren, Claudio Latorre, Zach Naiman, Jeff Pigati, Jason Rech, and Amanda Reynolds. I especially want to thank Sohrab Tawakholi and Servicio Nacional de Geologia y Mineria (SERGEOMIN) for field logistical support. I also thank the University of Arizona Accelerator Facility for 14C dates; the UMBMMR-Geochronology lab and W. McIntosh for 40Ar-39Ar dates; N. English and J. Mendez for field assistance; W. Pratt for mollusk identifications; G. Gehrels, W. Beck and I. Winograd for reference materials and samples; Bruce Bills and Ken Adams for useful discussion; J. Rech and K. Adams for tuffs; C. Isachsen, J. Wagner, and G. Manhes, for advice in the laboratory; Dave Dettman and Chris Eastoe for stable isotope analyses. Microprobe analyses would not have been possible without the assistance of Kenneth Domanik at the University of Arizona Lunar and Planetary Laboratory. Wesley Bilodeau made XRD analysis possible. I wish to thank Julia Cole and Jon Pelletier for useful discussions as well as for sitting on my dissertation committee. I also wish to thank Owen Davis for his mentorship in the teaching portion of my academic experience. This work was supported by NSF-EAR-0207850 to Jay Quade and Jon Patchett, and by grants from the Geological Society of America, the Arizona Geological Survey, Chevron, and University of Arizona Accelerator Facility. Finally, I would like to thank all of the Placzeks, especially Matt and Ellen. I, most of all, want to acknowledge Nathan English, my husband, for his endless support. 5 TABLE OF CONTENTS Page LIST OF TABLES………………………………………………………………... 8 LIST OF FIGURES………………………………………………………………. 9 ABSTRACT……………………………………………………………………… 11 INTRODUCTION……………………………………………………………….. 13 1. ALTIPLANO PALEOCLIMATE………………………………………………. 13 2. SOUTHERN BOLIVIAN ALTIPLANO……………………………………….. 15 3. MODERN CLIMATE………………………………………………………….. 15 PRESENT STUDY………………………………………………………………. 18 REFERENCES…………………………………………………………………… 22 APPENDIX A: STRATEGIES FOR SUCCESSFUL U-Th DATING OF PALEOLAKE CARBONATES: AN EXAMPLE FROM THE BOLIVIAN ALTIPLANO………………………………………………………………………31 ABSTRACT………………………………………………………………………...32 1. INTRODUCTION………………………………………………………………. 33 2. U-TH METHODS………………………………………………………………..39 2.1 Isotopic Tracers and Calibration……………………………………… 39 2.2 Chemical Procedures………………………………………………….. 41 2.3 Mass Spectrometry…………………………………………………….. 43 2.4 Error and error propagation………………………………………….. 45 2.5 Ages for Samples Dated by Other Laboratories………………………. 46 3. BOLIVIAN PALEOLAKE CARBONATES……………………………………47 3.1 Morphology and Petrography…………………………………………. 47 3.2 Character of the siliclastic detritus……………………………………..50 3.3 Initial 230Th/232Th ratios and isochron plots………………………… 53 4. IMPLICATIONS OF OUR STUDY FOR DATING OF PALEOLAKE CARBONATES…………………………………………………………………… 55 4.1 Dating of paleolake carbonates and closed U-Th systematics………… 56 4.2 Selection of carbonate samples from lacustrine settings……………….57 4.3 Selective vs. Total sample dissolution…………………………………..59 4.4 Initial 230Th/232Th…………………………………………………… 60 5. CONCLUSIONS……………………………………………………………….. 61 ACKNOWLEDGEMENTS……………………………………………………….. 62 REFERENCES…………………………………………………………………….. 64 APPENDIX B: GEOCHRONOLOGY AND STRATIGRAPHY OF LATE PLEISTOCENE LAKE CYCLES ON THE SOUTHERN BOLIVIAN ALTIPLANO: IMPLICATIONS FOR CAUSES OF TROPICAL CLIMATE CHANGE…………………………………………………………………………..87 ABSTRACT………………………………………………………………………...88 INTRODUCTION…………………………………………………………………. 89 STUDY AREA ……………………………………………………………………. 92 6 TABLE OF CONTENTS – Continued STRATIGRAPHIC NOMENCLATURE…………………………………………..93 METHODS………………………………………………………………………… 94 Field sampling…………………………………………………………….. 94 Laboratory methods……………………………………………………….. 96 Radiocarbon dating………………………………………….…….. 96 U-Th dating…………………………………………………………96 DATING CONSIDERATIONS…………………………………………………… 97 Radiocarbon dating……………………………………………………….... 97 U-Th dating………………………………………………………………... 99 STRATIGRAPHY AND CHRONOLOGY……………………………………….. 100 Ouki Alloformation…………………………………………………….….. 100 The Salinas Lake Cycle……………………………………………….…... 103 Toledo Geosol………………………………………………………….…...103 The Inca Huasi Lake Cycle…………………………………………….…...104 The Sajsi Lake Cycle……………………………………………………..... 105 Tauca Alloformation……………………………………………………..…106 Tauca Lake-Cycle Transgression………………………………..… 106 Tauca Lake-Cycle Highstand…………………………………….…107 Tauca Lake-Cycle Regression………………………………..…..... 108 The Coipasa Lake Cycle………………………………………………….... 109 Holocene Deposits………………………………………………………..... 111 SYNTHESIS OF THE LAKE RECORD………………………………………….. 112 Paleoshorelines: Climate or basin geometry?………………………………112 Comparison to other records………………………………………………. 113 DISCUSSION……………………………………………………………………... 116 CONCLUSIONS…………………………………………………………………... 120 ACKNOWLEDGEMENTS………………………………………………………...121 REFERENCES…………………………………………………………………….. 123 APPENDIX C: FIELD GUIDE TO GEOCHRONOLOGY AND STRATIGRAPHY OF LATE PLEISTOCENE LAKE CYCLES ON THE SOUTHERN BOLIVIAN ALTIPLANO………………………………………………………………………157 INTRODUCTION………………………………………………………………..... 158 SITE DESCRIPTIONS……………………………………………………………..159 APPENDIX D: GEOCHEMISTRY, CHRONOLOGY, AND STRATIGRAPHY OF LATE PLIOCENE TO HOLOCENE TEPHRA LAYERS OF THE CENTRAL ANDEAN REGION………………………………………………………………. 184 ABSTRACT………………………………………………………………………...185 INTRODUCTION…………………………………………………………………. 186 STUDY AREA…………………………………………………………………….. 188 METHODS………………………………………………………………………… 189 7 TABLE OF CONTENTS – Continued Field methods……………………………………………………………….189 Chronology………………………………………………………………… 189 Tuff identification
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