A new late quaternary palaeohydrological record for the Atherton Tableland, northeastern Queensland, Australia
Creators: name: Burrows, Mark Andrew
Publisher: name: The Australian National University
Year: 2016

description: This study focuses on the application of humification to organic rich deposits as a measure of palaeohydrological change over the last 37 ka on the Atherton Tableland of northeastern Australia. Studies in southern Australia have illustrated the effectiveness of certain volcanic landscape features (specifically crater basins) to act as rain gauges recording changes in both contemporary and past rainfall. Preliminary field researches on the Atherton Tableland in 2009 identified two volcanic crater basins, Bromfield Swamp and Mount Quincan crater, that retained deep peat and organic-rich sequences in basins that had a large surface area relative to their total catchment area, indicating lake systems little impacted by fluvial processes. Sediment cores were extracted from each basin using a piston corer mounted on a stationary floating platform. In each case the sediment profiles where not homogenous but changed with increasing depth from surface peats to gyttja and laminated organic sediments through to fine-grained inorganic sediments at depth. Palaeohydrological proxy indicators, including humification, pollen analysis, stable isotope analysis (Delta 13C), C/N analysis, charcoal analysis, magnetic susceptibility, grain size and ITRAX scans were applied to the sediments to infer changes in past environments and climate. The application of humification as a proxy for palaeohydrological change in Australian landscapes is poorly understood. The thesis aims to (i) test the validity of peat humification as a reliable proxy indicator of past variability, (ii) apply humification at high resolution to deep peat deposits (Bromfield Swamp and Mount Quincan crater) spanning the last 4000 years and compare these to existing palaeoclimate records, and (iii) produce a near-continuous record of changes in relative precipitation spanning the last 37 ka years using a suite of palaeohydrological proxies applied to organic and inorganic clastic sediments from Bromfield Swamp. The study shows that peat humification analysis can identify wet and dry shifts in a peat sequences from the humid tropics with significant correlation between the humification record and other proxies used in determinations of past climate (pollen, Delta 13C, C/N, macrocharcoal). Seventeen wet and fourteen dry shifts were detected in the last 4000 years from peat humification at Bromfield Swamp and Mount Quincan crater. The long sediment record (ITRAX, magnetic susceptibility, grain size and humification) from Bromfield Swamp shows that prior to 4000 years BP there are a further fifteen significant wet periods that can be identified in the 37 ka sedimentary record for Bromfield Swamp. These date to 36450, 36110, 34720, 29050, 27560, 2678, 26100, 25800, 24660, 24240, 23670, 22530, 13610, 11880, 10020, 8140, 3980 cal. yr BP. The study shows that high resolution ITRAX scanning combined with multi-proxy analysis (humification, pollen, charcoal, grain size and magnetic susceptibility) of organic-rich sediments can produce robust palaeoclimatic data, allowing identification of wet and dry shifts in a complex sedimentary sequence from the late Pleistocene-Late Holocene. The XRF record identifies periods of abrupt climate change which strengthens the capacity to correlate these changes with high-resolution records from terrestrial sites across the Southern Hemisphere and potentially, global events.