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Osu1211903448.Pdf (5.68 CLIMATE AND TECTONIC CONTROLS ON SEDIMENTATION AND DEFORMATION IN THE FIAMBALÁ BASIN OF THE SOUTHERN PUNA PLATEAU, NORTHWEST ARGENTINA A Thesis Presented in Partial Fulfillment of the Requirements for the Degree of Master of Science in the Graduate School of The Ohio State University By Heather Meybel McPherson, B.S. * * * * * The Ohio State University 2008 Master’s Examination Committee: Dr. Lindsay Schoenbohm, Advisor Dr. Lawrence Krissek Approved By: Dr. Terry Wilson ______________________ Advisor Geological Sciences Graduate Program Copyright by Heather Meybel McPherson 2008 ABSTRACT Here, we elucidate the relationship between tectonics and climate and their influence on sedimentation, erosion, deformation, coarsening of clastic sediment, regional uplift, and aridification by investigating Punaschotter Conglomerates of the Fiambalá Basin in Northwest Argentina through mapping, cross-section construction and U-Pb dating of interbedded ashes. U-Pb zircon dating of seven interbedded ashes and ignimbrites from within the Punaschotter Conglomerates reveal deposition beginning at 4.02 ± 0.04 Ma. Comparisons to regional basins show that deposition in the Toro and El Cajon Basins preceded deposition in the Fiambalá Basin, while deposition in the Santa Maria, Angastaco, and Hualfín-Río Basins is significantly younger. Regional conglomerate deposition is asynchronous between basins, and with both global and regional climate change. Therefore, we find that deposition is most likely the result of increased aridification driven by regional uplift of basin-bounding ranges, and enhanced by regional and global climate cooling between 6.4-2.6 Ma and 2-4 Ma, respectively. ii ACKNOWLEDGMENTS My sincere gratitude to Lindsay Schoenbohm, my advisor, for intellectual support, guidance, and encouragement during my research and completion of this thesis. Many thanks to Terry Wilson and Larry Krissek, my committee members, for intellectual discussions, advice, and assistance in completing this thesis. With much appreciation and many thanks to Juan Palevecino for his friendship, humor, guidance, and assistance in the field and around Argentina. Thank you to Jonathan Pratt for assistance with sample preparation and analysis at The Ohio State University and UCLA, and to Fritz Hubacher and Jeff Linder for guidance in the mineral separation lab at The Ohio State University. A special thank you to Ben Kirby and Wendy Bohon for their friendship, intellect, and humor over the past two years. With utmost appreciation for my friends and family for their support during this very important personal and intellectual endeavour. iii VITA June 22, 1979……………………………………………Born - San Salvador, El Salvador 2001…………………………………………………….B.S. Geology, Denison University 2002-2006……………………………….……..Hydrogeologist, Eagon & Associates, Inc. 2006-present…………………………..……...Graduate Research and Teaching Associate The Ohio State University PUBLICATIONS 1. McPherson, H., Schoenbohm, L., Carrapa, B., Schmidt, A., and Bohon, W., (2007), Climate and Tectonics Controlling Sedimentation in the Fiambala Basin, Northwest Argentina, Eos Trans. AGU, 88 (52), Fall Meet. Supple., Abstract T23D-1655. 2. Schoenbohm, L., Mortimer, E., Strecker, M., McPherson, H., Pratt, J., (2007), Deposition and Deformation in the El Cajon Basin, NW Argentina: a record of climate change, plateau growth and foreland fragmentation, Eos Trans. AGU, 88 (52), Fall Meet. Supple., Abstract T12D-06. 3. Bohon, W., Schoenbohm, L., Brooks, B., Costa, C., and McPherson, H., (2007), Drainage Analysis and Fluvial Terrace Reconstruction: Assessing Blind Thrust Hazards, Montecitos Anticline, Mendoza, Argentina, Eos Trans. AGU, 88 (52), Fall Meet. Supple., Abstract T23D-1652. 4. McPherson, H., and Hawkins, D., 2002, The June 1886 Eruption of Mount Tarawera, North Island, New Zealand, Denison Journal of the Geosciences, vol. 16, p. 24. FIELDS OF STUDY Major Field: Geological Sciences iv TABLE OF CONTENTS Page Abstract…………………………………………………………………………………....ii Acknowledgments…………………………………………………………………..……iii Vita………………………………………………………………………………………..iv List of Tables…………………………………………………………………………….vii List of Figures…………………………………………………………………………...viii Chapters: 1. Background………………………………………………………………………..1 1.1 Introduction……………………………………………………………………1 1.2 Motivation……………………………………………………………………..2 1.3 Tectonics Driving Climate Change……………………………………………3 1.4 Climate Change Driving Increases in Sedimentation and Erosion...………….6 2. Climate and Tectonic Comparison within the Fiambalá Basin, Northwest Argentina………………………………………………………………………......9 2.1 Introduction……………………………………………………………………9 2.2 Regional Geologic Setting…………………………………………………...12 2.2.1 Puna Plateau……………………………………………………………12 2.2.2 Intramontane Basins……………………………………………………14 2.2.3 Fiambalá Basin…………………………………………………………16 2.2.4 Other Regional Basins…………………………………………………24 2.3 Climatic Setting……………………………………………………………...23 2.3.1 Global Cenozoic Climate Change……………………………………...23 2.3.2 Orbital Forcing of Climate……………………………………………..30 2.3.3 Continental Scale Tectonic Forcing of Climate………………………..32 2.3.4 Local Tectonic Forcing of Climate…………………………………….36 2.4 Methods………………………………………………………………………39 2.5 Results………………………………………………………………………..44 2.6 Discussion……………………………………………………………………54 2.6.1 Age of the Punaschotter Conglomerates in the Fiambalá Basin……..54 2.6.2 Deposition, Folding, and Faulting in the Fiambalá Basin…………...61 v 2.6.3 Geochronology of the Punaschotter Conglomerates Along the Puna Plateau………………………………………………………….…………….64 2.6.4 Comparison to Regional Basins…………………………….………..68 2.6.5 Migration of a Tectonic Orogen………..…………………………....70 2.7 Comparison to Climate and Tectonics……………………………….………71 2.7.1 The Fiambalá Basin Punaschotter Conglomerates…………….………71 2.7.2 Regional Basin Conglomerates……………………………………..….72 2.8 Synthesis……………………………………………………………………..75 3. Conclusion…………………………………………………………………………….78 3.1 Summary………………………………………………………………….….78 3.2 Limitations……………………………………………………………….…..80 3.3 Data Issues……………………………………………………………….…..81 3.4 Future Work………………………………………………………………….82 References Cited…………………………………………………………………………83 vi LIST OF TABLES Table Page 1. Climate Summary – Past 10 Ma……………………………………………..…..29 2. U-Pb Geochronology Results……………………………………………..……..42 vii LIST OF FIGURES Figure Page 1. The Altiplano-Puna Plateau of South America…………………….…………….13 2. Regional basins and associated thrust and reverse faults along the margin of the Puna Plateau………………………………………………………………….…..15 3. The Fiambalá Basin……………………………………….……….………….…17 4. Tamberia Formation and Guanchin Formation………………..……………..….20 5. The Punaschotter Conglomerates …………………………………………….…21 6. Fiambalá Stratigraphy……………………………………………………………23 7. Age of Regional Exhumation, Uplift and Deformation …….……………..……25 8. Cross sections locations within the Fiambalá Basin…………………………..…40 9. Map and cross section A-A’...………………………………………..………….45 10. Map and cross section B-B’……………………………….……………………..47 11. Map and cross section C-C’……………………………………………………...48 12. Map and cross section E-E’……………………………………………………...50 13. Map and cross section D-D’……………………………………………………. 51 14. Map and cross section F-F’……………………………………………………....52 15. Map and cross section from Carrapa et al. (in press)…...…………….………….53 16. Punaschotter-Guanchin contact………………………………..……………...…56 17. Paleowatersheds in the Fiambalá Basin…………………………..………...……60 viii 18. Geologic and structural mapping of the Fiambalá Basin………………………...62 19. Age of the regional Punaschotter Conglomerates………………………………..65 ix CHAPTER 1 BACKGROUND 1.1 INTRODUCTION Tectonics and climate can each independently affect the landscape by changing rates of erosion and sedimentation, through uplift and subsequent shedding of sediment from nearby mountain ranges, by changing depositional patterns, and by causing aridification. However, tectonics and climate cause similar changes in the landscape, making it difficult to distinguish which of the two is the principal driving force in a particular case. This study seeks to elucidate the relationship between tectonics and climate and their influence on sedimentation, erosion, and deformation during the late Miocene-Pliocene in the Fiambalá Basin of Northwest Argentina. This is done by structural, geologic, and geomorphic mapping, and U-Pb zircon dating of interbedded ashes within the Punaschotter Conglomerates shed from the nearby Puna Plateau. Our results are compared with those of other basins in the region to more accurately evaluate and constrain timing of tectonic and climatic influences. This paper is composed of three chapters. The opening chapter provides a background to the problem of distinguishing the interlayered, interdependent effects of climate and tectonics on erosion, exhumation and the sedimentary record. The second chapter presents the details found by this study for the timing of Punaschotter deposition in the 1 Fiambalá Basin, makes a comparison to other basins in the region, and discusses the overall implications for both tectonics and climate change related to this study. The final chapter is a conclusion which summarizes the findings of this study, discusses the limitations of our research and problems with the data, and makes suggestions for future study in the Fiambalá Basin. 1.2 MOTIVATION Increased sedimentation and erosion rates, and increased clastic grain size in the last 2-4 Ma (Peizhen et al., 2001) have commonly been ascribed to late Cenozoic uplift of mountain ranges worldwide. In 1990, Molnar and England proposed an alternative to this hypothesis and suggested that
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