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  • 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.
    Data Types:
    • Other
  • 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.
    Data Types:
    • Other
  • 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.
    Data Types:
    • Other
  • 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.
    Data Types:
    • Other
  • Marine sediments Indian Ocean... Paleontology Quaternary
    Data Types:
    • Other
  • Marine sediments Indian Ocean... Paleontology Quaternary
    Data Types:
    • Other
  • Marine sediments Indian Ocean... Paleontology Quaternary
    Data Types:
    • Other
  • Marine sediments Indian Ocean... Paleontology Quaternary
    Data Types:
    • Other
  • The relatively understudied intermediate waters of the world have been implicated as an important part of the global ocean circulation. This thesis discusses the intermediate waters of the Pacific over space and time. Initially, by using geochemical tracers to look at the present distribution, sources and mixing of the water masses. Secondly, by using oxygen and carbon isotopes from sediment cores to study changes in Antarctic Intermediate Waters (AAIW) over the late Quaternary in the north Tasman Sea. ¶ The geochemical tracers highlight the presence of three separate intermediate water masses in the Pacific: North Pacific Intermediate Water (NPIW), AAIW and Equatorial Intermediate Water (EqIW). The EqIW has previously been considered an extension of intermediate water masses to the north or south. The unique geochemical characteristics of EqIW indicate, however, that it cannot be formed by direct mixing of the NPIW and AAIW. Geochemical tracers suggest instead that EqIW must also include mixing with nutrient rich, oxygen deficient, old Pacific Deep Water (PDW). ...
    Data Types:
    • Other
  • This research endeavoured to lay the groundwork in understanding the oceanic cycling of silicon (Si) during the past, with a particular focus on the Southern Ocean, using a multi-proxy and multi-organism approach. Two oceanographic tracers, one based on the fractionation of natural abundances of stable Si isotopes and the other based on the germanium:silicon ratio (Ge/Si), were examined in siliceous sponges and diatoms and their surrounding seawater. Specifically, this thesis attempts to validate the use of the Si isotope composition and Ge/Si, measured in siliceous organisms, as proxies for Si utilisation in order to test questions such as the Silicic Acid Leakage Hypothesis (SALH). The investigations examine (1) Ge/Si fractionation in diatoms, (2) Si isotope fractionation in sponges, (3) Si utilisation over the past 120,000 years in a low Si environment based on Si isotope and Ge/Si signatures of fossil diatoms, and (4) the utility of Ge/Si and Si isotope composition for estimating Si utilisation in paleoceanographic reconstructions. (1) In the modem global ocean, Ge/Si fractionation occurs as a result of subtle differences in the uptake of germanium and silicon via diatoms in surface waters. Temporal changes in seawater Ge/Si are likely to be faithfully recorded by diatoms in areas that do not drop below a seawater Si concentration that leads to a reduction in diatom growth; (2) A new model is proposed by which Si isotope fractionation in marine sponges is regulated by the Si influx to efflux ratio which, in tum, is controlled by the external Si concentration of seawater. The model indicates that Si isotope fractionation associated with uptake transport is constant at -1.34 per mil whereas fractionation during spicule formation increases as a function of external Si concentration. The model predicts that the observed Si isotope fractionation in sponges will never exceed -6.02 permil; (3) The comparison of two geochemical proxies for Si utilisation, Ge/Si and Si isotope composition of diatoms, for sediment core E33-22 located north of the Antarctic Polar Front (APF) in the Pacific sector of the Southern Ocean provides geochemical evidence that seawater Si concentrations do not change over glacial-interglacial periods of the late Quaternary. The estimated Si concentrations, ranging from 0 to 3 micro mol L-l, were used to elucidate the decoupling between the Ge/Si and Si isotope composition of diatoms. The temporal fluctuations in Si concentration are small and do not meet expectations of the SALH where a major assumption is that Si "leaked" northward of the APF into the sub-Antarctic zone; (4) This thesis suggests that the reconstruction of paleo-Si concentrations comparing two geochemical proxies for Si utilisation, Ge/Si and Si isotope composition of siliceous organisms, is more accurate than if used alone. Further, the reconstruction of deep-water Si concentrations based on sponge spicule analyses provides more useful information on whole ocean changes than simply examining surface water variation provided by the Ge/Si or Si isotope composition of diatoms.
    Data Types:
    • Other