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Spatial Variability in Proglacial Fjord Sediment Composition Along the Southern Patagonian Icefield (47–51°S)

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Spatial Variability in Proglacial Fjord Sediment Composition Along the Southern Patagonian Icefield (47–51°S) SPATIAL VARIABILITY IN PROGLACIAL FJORD SEDIMENT COMPOSITION ALONG THE SOUTHERN PATAGONIAN ICEFIELD (47–51°S) Matthias Troch Student number: 01205240 Promotor: Prof. Dr. Sébastien Bertrand Jury: Dr. Inka Meyer, Dr. Juan Placencia Master’s dissertation submitted in partial fulfilment of the requirements for the degree of Master of Science in Geology Academic year: 2016 - 2017 Acknowledgements Before reading my master dissertation, I would like to seize the opportunity to thank some people who helped and supported me during this study. First of all, I would like to thank my promotor, Prof. Dr. Sébastien Bertrand. You gave me the opportunity to study the Patagonian fjords, a pristine area of natural beauty. I greatly appreciate your support and readiness to answer my questions. I am very thankful for all your advice and constructive discussions we had. From you, I learned a lot of how to work and think as a geologist. For this, I am very grateful for having you as a promotor. I would also like to thank Dr. Juan Placencia and Dr. Lorena Rebolledo for providing samples from the Cimar 20 and Copas 2014 cruises in the Chilean fjords. Without these samples, and the additional data provided by them, this study would not have been possible. Furthermore, I would like to thank the Renard Centre of Marine Geology for the usage of the equipment in their laboratory and computer lab. I would also like to acknowledge all the people working at the RCMG, who taught me how to work with different kinds of software. I am especially grateful to Veerle Vandenhende from the laboratory staff of the Department of Geology, for helping me in the laboratory, performing ICP- analysis on my samples, and providing answers to all my questions. I would like to express my gratitude to the people who work in the group of Prof. Dr. Sébastien Bertrand: Loic Piret, Elke Vandekerkhove and Dawei Liu. They helped me to solve my problems in the laboratory and practice lots of analytical techniques. I would like to thank all my fellow students. We supported each other during our entire study and, especially, during our final, hard times of writing our master dissertations. I enjoyed the great times we had during the classes, field trips and non-geological related activities. I am grateful to all French wine farmers, who made our evenings during the Alps excursion. I would also like to thank Bruno Vanderborght and Freddy Van Puyenbroeck for reviewing my master thesis. Their comments and suggestions helped me to improve this dissertation. Finally, I would really like to thank my mother, Kristin Vanderborght, and my girlfriend, Hannah Dermaux, for their great support and endless encouragement during my student years. To my mother and father, thank you for providing me the chance of education and your unconditional help and love. To my sister, Hannah Troch, after this experience, I might consider to become a doctor, but probably not the type you want… I would like to thank my girlfriend for all the Netflix evenings helping me relax after a stressful day of writing. This being said, I would also like to thank Netflix for the free month, this came in pretty handy. Thank you and enjoy reading! Matthias 2 The Story of my Research As library books provide information regarding human history, geological records, e.g., ice cores, tree rings, and fjord, lake and marine sediments, provide information about our climate history. The language in which this information is written is however not entirely clear yet. For my master dissertation, I investigated sediments from the fjords in Chilean Patagonia, where glaciers from the Southern Patagonian Icefield terminate, to understand how glacier size variations are written in sediments. More specifically, the goal of my research was to identify fjord sediment properties that can be used to reconstruct past glacier advance and retreat. Since no similar research has been done in this study area, the results of this master dissertation provide a valuable asset to reconstruct past glacier size variability in Chilean Patagonia. Since the size of glaciers is affected by various climate parameters such as temperature and precipitation, reconstructing past variations in glacier size can provide important indications on past climate variations in the glacier’s region. Comprehending past climate change is essential to predict future climate change. Glacier advance might by the result of decreased temperature and/or increased precipitation. Glacier retreat might be caused by increased temperature and/or decreased precipitation. The Patagonian fjords form a pristine area of natural beauty. In the future, human influence in this region may become critical, disturbing local fauna and flora. Scientific research in this area is only in its early stages. Learning more about this region can help preserve it. 3 Abstract An accurate understanding and interpretation of fjord sediment records is essential to reconstruct glacier and climate variability. In order to predict the evolution of glaciers in a changing climate, one must comprehend the dynamic response of glaciers to climate change. Fjord sediments can provide a detailed record of past glacier variability. To better interpret such proxy records, accurate proxies of past glacier mass balance variations are needed. With this in mind, this study investigates the spatial variability of physical properties, sediment composition and bulk organic and inorganic geochemistry of surface sediments within the fjords north and west of the Southern Patagonian Icefield (SPI). The studied surface sediment samples are located along transects from the fjord heads towards the open ocean. The main research objective is to identify bulk organic and inorganic geochemical properties to estimate past changes in terrestrial sediment supply towards these fjords systems. In the case of glaciated fjords, terrestrial sediment supply can serve as an indicator for glacier variability. This study makes use of two fjord systems: the Baker Martinez Fjord Complex (BMFC), which is located to the north of the SPI and mostly composed of river-fed fjords, and the fjord system west of the SPI, which is mainly influenced by calving glaciers. The main difference between both fjord systems is the presence and absence of calving glaciers, hence the presence and absence of icebergs and ice rafted debris. Our results indicate that ice rafted debris can serve as a sedimentological proxy to differentiate glaciated fjords, i.e., fjords with calving glaciers, from non glaciated fjords, i.e., fjords without calving glaciers, in Chilean Patagonia. The spatial variability of the bulk inorganic geochemistry is significantly different between fjords with different sources of terrestrial sediment, i.e., calving glaciers or rivers. Therefore, the use of bulk inorganic geochemical proxies should be confined to one specific fjord, and not over an entire fjord system. Within the BMFC, the elemental log-ratios Fe/Al, Zr/Al, Ti/Al, Mg/Al and litho-Si/Al show promising results to estimate past changes in terrestrial sediment supply. Due to a low sampling density, no such proxies were identified within the fjord system west of the SPI. Throughout both fjord systems, carbon and nitrogen isotopic composition of fjord sediments are well suited to estimate past changes in terrestrial sediment supply. More depleted δ13C (‰) and δ15N (‰) values are found near glacier fronts and river outlets, while less depleted δ13C (‰) and δ15N (‰) values represent more marine environments. The spatial variability of the atomic N/C ratio does not show a significant terrestrial to marine trend in the studied fjord systems. In addition, our results show that the mass-specific magnetic susceptibility signal of fjord sediments can be used to differentiate terrestrial sediment supply from the Northern and Southern Patagonian Icefields, due to the distinct lithologies on which these ice masses occur. The results of this master dissertation should help improve the interpretation of physical, sedimentological and geochemical data from fjord sediment cores in terms of sediment provenance and glacier variability. 4 Table of content Acknowledgements ......................................................................................................................................... 2 The Story of my Research ............................................................................................................................... 3 Abstract ........................................................................................................................................................... 4 Table of content ............................................................................................................................................... 5 1. Introduction .............................................................................................................................................. 7 2. Regional Setting .................................................................................................................................... 10 2.1 Patagonian Geology ...................................................................................................................... 10 2.2 Tectonic Setting ............................................................................................................................. 11 2.3 Patagonian Volcanism ..................................................................................................................
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