Late-Quaternary Paleoclimate of Mount Field, Tasmania by Andrew
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Late-Quaternary paleoclimate of Mount Field, Tasmania by Andrew Rees BSc University of New Brunswick, 2005 BA University of New Brunswick, 2005 A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in the Graduate Academic Unit of Biology Supervisor: Les Cwynar, PhD Examining Board: Joseph Culp, PhD, Department of Biology Tillmann Benfey, PhD, Department of Biology Joseph White, PhD, Department of Earth Sciences External Examiner: James Shulmeister, PhD, School of Geography, Planning and Environmental Management, University of Queensland, Australia This dissertation is accepted by the Dean of Graduate Studies THE UNIVERSITY OF NEW BRUNSWICK May, 2014 ©Andrew Rees, 2014 Dedication To my families Rees and Hickey Together we‟ve overcome many hardships and, Without whose love and support, I could not have persevered ii Abstract The mid-latitudes of the Southern Hemisphere possess a complex history of paleoenvironmental change. I address two objectives using lake sediment records from Tasmania, one of the few landmasses situated within this critical region of the “Water Hemisphere”. First, cosmogenic dates from terminal moraines and sea surface temperatures (SST) suggest the climate of south-eastern Australia warmed rapidly after the Last Glacial Maximum, whereas pollen records indicate temperatures only began to increase at the onset of the Holocene, roughly 11.5 thousand calibrated years before present (cal ka BP). To explicitly address this discrepancy, I surveyed the modern environmental drivers of chironomid (Insecta: Diptera) distributions in Tasmania and developed an independent proxy of temperature. Second, a large body of literature has emerged invoking the Southern Westerly Winds (SWW) and El Niño/Southern Oscillation (ENSO) as major drivers of paleoenvironmental change. Some researchers have hypothesized that the SWW governed broad scale precipitation patterns from 14 to 5 cal ka BP, when ENSO became the main control of synoptic climate. Using a suite of lacustrine proxies, I investigated the nature of the transition from a SWW- to ENSO- dominated climate regime. In terms of the first objective, pH explains most of the variance in the modern chironomid distributions. This environmental variable delineates between two geological provinces in Tasmania: one province has infertile, acidic soils and the other has soils generally richer in clay, possessing a greater buffering capacity. However, temperature of the warmest quarter (TWARM) explains most of the variance in the chironomid fauna within either iii geological province. Consequently, I applied a chironomid-based transfer function for TWARM to a pair of fossil chironomid records from Mount Field National Park. Temperatures were at or above modern values early in the record, from about 15 to 13 cal ka BP, supporting the evidence from the cosmogenic dates and SST. After a prolonged cooling, temperatures again returned to modern, supporting a mid-Holocene thermal maximum between 6.7 and 4.6 cal ka BP. I used another lake sediment record from Mount Field to address the second objective. Based on lacustrine proxies, SSW controlled precipitation from 12 to 4.9 cal ka BP, fluctuating from wet to dry conditions around 8.4 cal ka BP. The abrupt shift to a generally dry though variable climate at 4.9 cal ka BP was characterized by an increased fire frequency. Considering all of the proxies, their transitions were nearly simultaneous and concurrent with the onset of ENSO activity in Ecuador, highlighting close links between the equatorial Pacific and south-eastern Australia. iv Acknowledgments I would like to start by thanking my supervisor and mentor, Dr. Les Cwynar. Where I am details-oriented, and sometimes cannot see the forest for the trees, Les was always able to help me see the big picture; he outlined the sandbox, but let me choose how to play. With this freedom, I was able to cultivate a toolset particular to the paleolimnologist‟s trade and develop templates of environmental change for parts of Tasmania. These templates can be used to generate specific climate questions, bringing me to the most important lesson. Les always stressed the significance of asking good research questions, and I look forward to putting this lesson to use throughout my career. I also appreciate the advice, feedback, and open doors of my other supervisory committee members, Dr. Steve Heard and Dr. Donald Baird. This research was made possible by the generosity of many funding agencies. I am thankful to the Natural Sciences and Engineering Research Council of Canada, the Dr. John S. Little International Study Fellowship, The O‟Brien Fellowship and the various funding opportunities provided by the University of New Brunswick. I am also grateful to my wonderful lab mates who made the tedium of core subsampling and chironomid sorting bearable. Thank you Phil Brown, Katie and Kristie Richardson, Laura Bursey, Nancy Zhou, Daniel Lebouthillier, and Emily Higgins. On the other side of the microscope, I am indebted to Joshua Kurek for interspersing advice with fishing tips and to Stefen Engels for expanding my numerical literacy while simultaneously reducing my brain cell count at “Metal Mondays”. Thank you Roger Smith and Bong Yoo for enlightening the photo shoot of sediment cores and terrestrial macrofossils. And a special thanks to my colleagues who made life inside and outside of v Bailey Hall fun: Fonya Irvine, Stephan Köning, Bridgette Clarkston, Julie Ryu, Laura Grace, Katrina Chu, Jeff Crocker and David Armanini. Many thanks to Margaret Blacquier, Melanie Lawson, Rose Comeau, and Marni Turnbull for cheerfully dealing with my administrative and financial ineptitudes. I am also appreciative of Mike Casey for venturing outside of the Apple ecosystem to help me with technical issues of a PC nature. To Sean and Heather, thank you for supplying a second home and the psychological nurture only best friends can provide. I will finally admit that our associations are based on more than geographical location! Also, thank you Adam, Nicole, Trevor, Janice, Andrew, Helen, Gabe, and Shawn for making Fredericton such an extraordinary place. I am especially grateful for the best of all possible families. Mom, Dad, Katie, and Tim, thank you for putting up with my rants, encouraging my decisions, and being unwavering in your support; a person could not ask for a better clan. And finally, to my moon and stars, your love gives me the strength to attempt any challenge, your understanding the courage to pursue seemingly unattainable goals, and your patience the opportunity to finish this thesis! Thank you. vi Table of Contents Dedication .................................................................................................................................ii Abstract................ .................................................................................................................. iii Acknowledgments .................................................................................................................... v Table of Contents .................................................................................................................. vii List of Tables ........................................................................................................................... xi List of Figures........................................................................................................................ xii List of Common Abbreviations ............................................................................................xiv Chapter 1 Introduction ............................................................................................................. 1 The significance of Tasmania to Quaternary research in the Southern Hemisphere ........................................................................................................................... 1 Tasmania and its (paleo)climate.......................................................................................... 3 Chironomids and the transfer function approach ............................................................... 5 Thesis organization and objectives ..................................................................................... 8 Statement of contributions ................................................................................................. 10 References .......................................................................................................................... 11 Chapter 2 Midges (Chironomidae, Ceratopogonidae, Chaoboridae) as a temperature proxy: a training set from Tasmania, Australia ................................................... 22 Abstract ............................................................................................................................... 23 Introduction ........................................................................................................................ 24 Study area ........................................................................................................................... 27 Climate............................................................................................................................ 27 Geology and vegetation ................................................................................................. 28 Materials and methods ......................................................................................................