Development and Application of Leaf Wax Geochemistry to Reconstruct Late Cenozoic Climate and Environmental Change in Australia A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy Jake William Andrae BSc (Hons Geology) School of Physical Sciences - Department of Earth Science August 2019 1 This page is intentionally left blank 2 Table of contents Abstract .................................................................................................................................. 7 Statement of certification ....................................................................................................... 9 Acknowledgments ............................................................................................................... 10 Chapter 1: Background and literature review ...................................................................... 12 1 Leaf wax n-alkane proxy systems ................................................................................. 13 1.1 Background ............................................................................................................. 13 1.2 n-Alkane molecular distributions as a proxy for vegetation composition .............. 14 1.3 n-Alkane molecular distributions as a climate proxy ............................................. 16 1.4 n-Alkane carbon isotope ratios as a proxy for photosynthetic pathway ................. 18 1.5 n-Alkane carbon isotope ratios as a proxy for carbon sources ............................... 23 1.6 n-Alkane hydrogen isotope ratios as a hydrological proxy .................................... 23 2 Late Cenozoic global and Australian palaeo-environments .......................................... 27 2.1 Late Cenozoic expansion of C4 vegetation ............................................................ 27 2.2 Environmental drivers for C4 expansion ................................................................ 30 3 Thesis outline and research aims ................................................................................... 32 References ........................................................................................................................ 34 Chapter 2: Variation in leaf wax n-alkane characteristics with climate in the broad-leaved paperbark (Melaleuca quinquenervia) ................................................................................. 53 Keywords ......................................................................................................................... 53 Abstract ............................................................................................................................ 53 1 Introduction ................................................................................................................... 54 2 Material and methods .................................................................................................... 59 2.1 Study species .......................................................................................................... 59 2.2 Study sites and sampling ........................................................................................ 59 2.2.1 Time-series study ............................................................................................. 59 2.2.2 South-east Queensland (SEQ) study ................................................................ 60 2.2.3 Cross-Queensland (QLD) study....................................................................... 60 2.3 Lipid extraction and purification ............................................................................ 61 2.3.1 Time-series ....................................................................................................... 61 2.3.2 Spatial studies: SEQ and QLD ......................................................................... 62 2.4 Time-averaged climate data ................................................................................... 63 2.5 Leaf wax characteristic calculations and statistical analysis .................................. 64 3 Results ........................................................................................................................... 66 3 3.1 Time-series ............................................................................................................. 66 3.2 South-east Queensland (SEQ) ................................................................................ 69 3.3 Cross-Queensland (QLD) ....................................................................................... 70 3.4 Levene’s test of homogeneity of variance (SEQ and time-series) ......................... 73 4 Discussion ..................................................................................................................... 74 5 Conclusions ................................................................................................................... 77 Acknowledgements .......................................................................................................... 78 References ........................................................................................................................ 78 Appendix .......................................................................................................................... 85 Chapter 3: Carbon isotope systematics of leaf wax n-alkanes in a lacustrine depositional environment ......................................................................................................................... 90 Highlights ......................................................................................................................... 90 Abstract ............................................................................................................................ 90 1 Introduction ................................................................................................................... 92 2 Materials and methods................................................................................................... 96 2.1 Site information ...................................................................................................... 96 2.2 Sample preparation ................................................................................................. 97 2.3 n-Alkane characterization and quantitation ............................................................ 98 2.4 Calculation of n-alkane distribution indexes .......................................................... 99 13 2.5 Leaf wax n-alkane δ C analysis .......................................................................... 100 3 Results ......................................................................................................................... 101 3.1 n-Alkane quantification ........................................................................................ 101 13 3.2 Leaf wax n-alkane δ C ........................................................................................ 102 13 3.3 Relationship between Paq and n-alkane δ C ........................................................ 103 4 Discussion ................................................................................................................... 104 5 Conclusions ................................................................................................................. 109 Acknowledgements ........................................................................................................ 110 References ...................................................................................................................... 111 Appendix ........................................................................................................................ 115 Chapter 4: Initial expansion of C4 vegetation in Australia during the late Pliocene ......... 120 Key points....................................................................................................................... 120 Abstract .......................................................................................................................... 120 Plain language summary ................................................................................................ 121 1 Introduction ................................................................................................................. 121 2 Materials and methods................................................................................................. 123 2.1 ODP 763 sample preparation ................................................................................ 123 4 2.2 Biomarker quantitation and compound-specific carbon isotope analysis ............ 124 2.3 ODP 763A age model ........................................................................................... 125 2.4 Adjustment for preindustrial atmospheric δ13C and modeling percent C4 .......... 125 2.5 Pollen .................................................................................................................... 126 3 Results ......................................................................................................................... 126 3.1 Leaf wax n-alkane distributions and carbon isotope ratios .................................. 126 3.2 Palynological results ............................................................................................. 128 4 Discussion and conclusions........................................................................................