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Copyright by Veronica Jacqueline Anderson 2015 The Dissertation Committee for Veronica Jacqueline Anderson Certifies that this is the approved version of the following dissertation: UPLIFT AND EXHUMATION OF THE EASTERN CORDILLERA OF COLOMBIA AND ITS INTERACTIONS WITH CLIMATE Committee: Brian K. Horton, Supervisor Richard A. Ketcham Daniel F. Stockli Timothy M. Shanahan Carmala N. Garzione UPLIFT AND EXHUMATION OF THE EASTERN CORDILLERA OF COLOMBIA AND ITS INTERACTIONS WITH CLIMATE by Veronica Jacqueline Anderson, B.S., Geophysics Dissertation Presented to the Faculty of the Graduate School of The University of Texas at Austin in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy The University of Texas at Austin May 2015 Acknowledgements I would like to thank a number of people for their time, advice, and insight during the course of this work. First, I would like to thank my advisor, Dr. Brian Horton, for his consistent and level-headed guidance throughout the course of my Ph.D, and for being an excellent role model as a scientist. I would also like to thank each of my committee members – Richard Ketcham, Daniel Stockli, Timothy Shanahan, and Carmala Garzione – for being available for spirited and productive scientific discussions that greatly improved this work. Although he was not an official member of the committee, I would also like to thank Joel Saylor for his major contributions to this work as an involved and insightful collaborator and coauthor. In addition, I would like to thank Andrés Mora and his colleagues at Ecopetrol for their continued support of our research, and their invaluable assistance in planning and executing several successful field seasons, as well as funding a significant portion of this reasearch. Juliana Barrientos Mesa and Miguel Corcione in particular provided critital assistance to us in the field that allowed the 2011 field season to be exceptionally productive and enjoyable. Sean Sylva and Konrad Hughen at WHOI generously committed their time and resources to assisting us with leaf wax hydrogen isotopic analyses that played a key role in Chapter 3. Dan Breecker and Toti Larsen provided essential guidance and scientific knowledge for the soil carbonate analysis in Chapter 4. Finally, I would like to thank my friends and family for their support and companionship over the last 5 years, and for making this time fly by as fast as it did. In particular, I’d like to thank my husband Jeff, who has happily put up with my worries, frustrations, and complaints as a Ph.D student, and who consistently makes all of this work seem worthwhile. iv UPLIFT AND EXHUMATION OF THE EASTERN CORDILLERA OF COLOMBIA AND ITS INTERACTIONS WITH CLIMATE Veronica Jacqueline Anderson, Ph.D The University of Texas at Austin, 2015 Supervisor: Brian K. Horton Recent breakthroughs in assessing past elevation using stable isotopes of sedimentary materials have provided important constraints on the timing and geodynamics of surface uplift in various orogenic systems. These advances in paleoaltimetry have enabled discrimination between competing models of topographic development in the Tibetan plateau, have provided constraints on the longevity of the Sierra Nevada as a major topographic feature in western North America, and have highlighted the possible role of lower lithospheric delamination in the central Andes of South America. However, there remains considerable debate over the geodynamic mechanisms involved in Andean uplift, as most available estimates on the timing and pace of past elevation gain show an irregular spatial and temporal distribution. In particular, uncertainty persists over the timing of surface uplift of the Eastern Cordillera in the tropical northern Andes of Colombia. Although changes in sediment accumulation, provenance, and thermochronometric estimates of bedrock exhumation suggest Andean shortening in the Eastern Cordillera since late Eocene-Oligocene time, the rise of the ~2600-m-high Bogotá plateau (Sabana de Bogotá), a intermontane hinterland basin appears to have significantly lagged the onset of shortening in the fold- thrust belt. In addition, there is dramatic variation in structural style along strike within the Eastern Cordillera, making it unclear whether a major basement-involved topographic high (the Garzón Massif) at the southern end of the range was contemporaneous with the rest of the Eastern Cordillera. Studies of pollen assemblages in clastic sedimentary fill of v the Bogotá plateau suggest that it may have risen rapidly from ~6-3 Ma and has maintained the same elevation thereafter. However, this scenario of rapid latest Miocene- Pliocene uplift followed by post-3 Ma stasis appears inconsistent with the structural geologic record, as more than half of the total shortening along the eastern Andean flank has occurred since ~3 Ma. We investigate the elevation history of the Bogotá plateau using novel lipid biomarker proxies for past surface temperature and isotopic composition of precipitation, and update the geochronologic framework of this basin using a refined magnetic polarity stratigraphy. We also utilize a multidisciplinary approach to determine the timing of uplift-induced exhumation of the Garzón Massif, employing U-Pb detrital zircon geochronological and sandstone petrographic results as tracers of sedimentary provenance, apatite fission track (AFT) thermochronometry to constrain exhumation, and the isotopic composition and elemental composition of paleosols and carbonate nodules to track climatic shifts associated with the uplift of the Garzón Massif. These approaches indicate that (1) the Bogotá Plateau had likely been partialy elevated prior to the late Miocene (~7.5 Ma) and has been uplifting continuously since then, (2) and that while the timing onset of exhumation of the Garzón Massif is similar to other parts of the Eastern Cordillera, it did not begin to build substantial topography until ~ 6 Ma. These results imply that the Eastern Cordillera did not become a contiguous topographic barrier, until late Miocene-Pliocene time, providing new constraints on the establishment of the Magdalena River, a northward-draining system that contributes an enormous sediment load to the Caribbean Sea, as a discrete system fully separated from the Amazon basin. vi Table of Contents List of Tables ...........................................................................................................x List of Figures ........................................................................................................ xi Chapter 1: Introduction ...........................................................................................1 Chapter 2: Sources of local and regional variability in the MBT’/CBT paleotemperature proxy: Insights from a modern elevation transect across the Eastern Cordillera of Colombia ......................................................................3 Abstract ...........................................................................................................3 2.1 Introduction ............................................................................................5 2.2 Materials and Methods ...........................................................................9 2.2.1 Field Area and Sampling ..............................................................9 2.2.2 Sample Preparation .....................................................................11 2.2.3 HPLC Analyses ...........................................................................12 2.2.4 Calculation of the BIT Index ......................................................13 2.3 Results and Discussion ........................................................................15 2.3.1 Colombia Dataset ........................................................................15 2.3.2 Evaluation of interpolation schemes for MAT data ....................17 2.3.3 Local Variability Within the Colombia Dataset .........................21 2.3.4 Comparison to the Global Soil Dataset .......................................25 2.3.5 Heterogeneity in brGDGT Patterns Across Five Transects ........29 4. Conclusions ..........................................................................................33 Chapter 3: Paleoelevation records from lipid biomarkers: Application to the tropical Andes ............................................................................................................35 Abstract .........................................................................................................35 3.1 Introduction ..........................................................................................37 3.2 Paleoaltimetry and organic geochemical proxies ................................41 3.2.1 Isotopic constraints on paleoelevation ........................................41 3.2.2 The MBT’/CBT proxy ................................................................42 3.2.3 Hydrogen isotopes in leaf waxes ................................................44 vii 3.2.4 Biomarker-based paleoaltimetry .................................................45 3.3 Chronostratigrapic Framework ............................................................47 3.3.1 Field localities .............................................................................47 3.3.2 Paleomagnetic chronology ..........................................................50 3.4 Geochemical methods ..........................................................................53 3.4.1 Biomarker