Diatom Stratigraphy Defining Ice Sheet Grounding Chronology, Ross Sea
Total Page：16
File Type：pdf, Size：1020Kb
Louisiana State University LSU Digital Commons LSU Doctoral Dissertations Graduate School 2010 Diatom stratigraphy defining ice sheet grounding chronology, Ross Sea, Antarctica Juan Manuel Chow Louisiana State University and Agricultural and Mechanical College, [email protected] Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_dissertations Part of the Earth Sciences Commons Recommended Citation Chow, Juan Manuel, "Diatom stratigraphy defining ice sheet grounding chronology, Ross Sea, Antarctica" (2010). LSU Doctoral Dissertations. 3150. https://digitalcommons.lsu.edu/gradschool_dissertations/3150 This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Doctoral Dissertations by an authorized graduate school editor of LSU Digital Commons. For more information, please [email protected]. DIATOM STRATIGRAPHY DEFINING ICE SHEET GROUNDING CHRONOLOGY, ROSS SEA, ANTARCTICA A Dissertation Submitted to the Graduate Faculty of Louisiana State University and Agricultural and Mechanical College in the partial fulfillment of the requirements for the degree of Doctor of Philosophy in The Department of Geology and Geophysics by Juan Manuel Chow B.Arch., Louisiana State University, 1991 M.S., Louisiana State University, 2003 May 2010 Dedicated to Mother. Come in from the garden and sit a spell. ii ACKNOWLEDGEMENTS I hear it told that the people one meets are outside the realm of coincidence. In this regard, I am thankful for the people with which I have crossed paths. Moreover, the act of research and making of a dissertation is never done alone, although it can feel lonely at times. My advisor, Dr. Philip Bart, who has been guiding my research, I value for his patience, friendship, and generosity. I will take his lessons wherever I go. My dissertation committee, Dr. Laurie Anderson, Dr. Brooks Ellwood, Dr. Richard Keim, and Dr. Juan Lorenzo. It would have been impossible to go forward without their help. Dr. John Wrenn and Dr. Lui-Heung Chan, they left us too soon and I am afraid I will never understand why. Dr. Charlotte Sjunneskog, who patiently helped me navigate the world of diatoms, and helped me figure out many other things as well. Thank you. Dr. Reed Scherer and Dr. Diane Winter – where would the world be without diatomers? The LSU Department of Geology and Geophysics – fellow students, staff, and faculty. Ms. Joan Payne, Ms. Stacey Leblanc Halphen, Ms. Heather Lee, Ms. Latosha Mullins, Mr. Rick Young – I love you guys. I am especially beholden to the following for their financial support: Dr. Bart and his support from various NSF grants; Dr. Sjunneskog for her support from NSF/ANDRILL grant; and the LSU Department of Geology and Geophysics, who have supported me through teaching assistantships. Of course, this manuscript would not have been possible without the helpful, hopeful, and tireless input from Drs. Bart and Sjunneskog. Mr. Sean Kerrin, thank you for reading an early version of the manuscript and thereby helping make it easier to read. Dr. Jeff Agnew, Dr. Lawrence Febo, and Dr. Rebecca Tedford. Yes, it seems we're a dying breed of LSU paleontologists, but I tell you what – we ain't extinct yet. iii Dr. Jacek Cygan, Ms. Małgorzata Cygan, Dr. John Weaver – Sunday afternoons just wouldn't be the same without you. Mr. John Winstead, thank you for teaching me to have the resolve I have always sought, but always seemed out of reach. My sisters and mother, thank you so much for your support. I love the blank look on your faces when I drone on and on about the microscopic world of diatoms. Last but certainly not least, Ms. M. Christine Hill. You crazy Mexicoon, you understand me in a way no one else does. The world would be a lonely place without you. Of course, where would I be without being able to hear Dwight Yoakam whenever I felt the ol' geology blues: “I've had to buy back damn near everything I own From a little man whose name is Saul And has a lot of money to loan I drive a beat up '67 Chevrolet With a torn up seat That pokes a brand new hole in my back near every day I got a letter from the folks over at Bell Just to let me know for my next phone call I could walk outside and yell Hey, I know my life seems a mess But honey, things to me still look real swell...” iv TABLE OF CONTENTS ACKNOWLEDGEMENTS…………………….………………………………………...…..….iii ABSTRACT………………………………...………………………………………..……...…...vi CHAPTER 1. INTRODUCTION…………………………………………..….………......….....1 CHAPTER 2. THE LAST EXTENSIVE GLACIAL ADVANCE OF THE WEST ANTARCTIC ICE SHEET…………………………………………………..….………..9 CHAPTER 3. ARE TILL SHEETS HOMOGENEOUS? A DIATOM PERSPECTIVE………………………………………….………………......…..42 CHAPTER 4. EARLY PLIOCENE DIATOM RECORD OF THE ROSS SEA CONTINENTAL SHELF, ANDRILL-1B CORE, ANTARCTICA…............................50 CHAPTER 5. CONCLUSIONS…………...……………………………………………..….…79 APPENDIX A. SUPPLEMENTAL DATA TABLES – EASTERN BASIN DIATOM RELATIVE ABUNDANCES………………………………………….…………….….81 A-1. BLUE UNIT SAMPLES.…………………...…………………………………..…82 A-2. PURPLE UNIT SAMPLES……………………………………………………….98 A-3. RED UNIT SAMPLES…………………………………………………..………118 A-4. BROWN UNIT SAMPLES………………………………………………...……138 A-5. GREY UNIT SAMPLES…………………………………………………..…….154 A-6. CENTRAL TROUGH SAMPLES……………………………….……….……..162 APPENDIX B. SUPPLEMENTAL DATA TABLES – BROWN UNIT DIATOM RELATIVE ABUNDANCES………………………………………..…..……….……174 APPENDIX C. SUPPLEMENTAL DATA TABLES – ANDRILL DUXII AND DUXIII DIATOM RELATIVE ABUNDANCES……………………………..…………....…..182 VITA……………………………………………………………………….……..………....…242 v ABSTRACT Evidence of Antarctic ice sheet behavior and paleoenvironment is often approached from proxy records because there is a dearth of direct records from Antarctica itself. The studies presented here seek to augment our knowledge of translations of the West Antarctic Ice Sheet’s (WAIS) marine termination based on direct biostratigraphic evidence. Diatom analyses were conducted from two areas of Ross Sea, Antarctica. In the first study, diatoms were used to constrain the age of diamictons from five seismic units in the Eastern Basin and thus expand our knowledge of WAIS behavior during the Southern Hemisphere Last Glacial Maximum (LGM). All five units have a late Pliocene diatom assemblage. The absence of a late Pleistocene diatom assemblage indicates that the Eastern Basin LGM could not have been at ca. 20 kyrs. Moreover, differences in diatom assemblages indicate that units previously assigned to a single phase of LGM advance and post-LGM retreat must have included two temporally distinct grounding events. In the second study, diatoms were used to assess the uniformity of a till sheet by comparing the assemblage from the topset bed to that of the interior of the till sheet. The analysis suggests that the till sheet as observed from seismic data is homogeneous, and helps support the validity of studies made by using short sediment cores that sample only the upper part of the till sheet. In the third study, diatoms from diatomite units from south of Ross Island were used to provide paleoenvironmental information about the early Pliocene. The diatom assemblages have no modern analogues, but they do indicate that sea surface temperatures were much warmer in the early Pliocene compared to the present, there was enhanced ice sheet ablation, and katabatic winds were absent at least during the diatom growth season. vi CHAPTER 1 INTRODUCTION 1.1 Introduction Much of what is known concerning Antarctic glacial cycles comes from evidence gathered from sites distant from Antarctica. For example, growth and collapse of the East Antarctic Ice Sheet (EAIS) and West Antarctic Ice Sheet (WAIS) are inferred from eustatic fluctuations such as those compiled by Haq et al. (1987). Additionally, geochemical records such as δ18O (Miller et al., 2005; Zachos et al., 2001) and Mg/Ca ratios (Billups, 2002; Billups and Schrag, 2003; Lea et al., 2000; Lear et al., 2000) give us important information not only on ice volume fluctuations, but also a host of other information such as thermohaline circulation and deep sea temperatures. Around the Antarctic margin, several drilling programs have been undertaken since the 1970's (e.g., DSDP Leg 28, ODP Legs 113, 119, 178, and 188). While important information have been obtained from those cruises, sediment and rock recovery from individual holes have generally been low, thereby limiting the amount of information that could have otherwise been obtained (Figure 1-1). There is a wealth of information from the Ross Sea and surrounding Transantarctic Mountains (TAM), most of them regarding the Last Glacial Maximum (LGM). These studies are mostly from the western Ross Sea, and as such are records EAIS advance and retreat (Licht et al., 2005). The eastern Ross Sea, on the other hand, records expansion and contraction of the WAIS. On the central and eastern Ross Sea, geomorphological evidence shows that the last 1 Figure 1-1. Map of Antarctica, with major ice sheets (WAIS and EAIS). Grey areas represent ice shelves. Truncated wedge shape marks the location of map in Figure 2-1. Rectangle within Figure 2-1 marks the location of map in Figure 4-3. glacial advance in the area (Mosola and Anderson, 2006; Shipp et al., 1999) proceeded to the outer continental shelf. Domack et al. (1999) conclude that ice sheet occupation of the outer continental shelf was between 19,500 and 26,500 years BP, based on a hiatus in bulk-organic carbon-dated sediments. Licht and Andrews (2002), however, place the ice sheet on the outer 2 continental shelf at 13,770 years BP. The retreat history of the WAIS is important because it provides a contextual comparison to Northern Hemisphere glaciation and sea level rise. Furthermore, the WAIS, because of its instability (Anderson et al, 2002) and therefore more dynamic nature compared to the EAIS, has been a focus of attention in order to understand and predict its future behavior in a changing/warming climate. 1.2 Diatoms Diatoms are siliceous microscopic unicellular algae that are abundant in high latitude and equatorial Pacific marine sediments.