Biomarkers for understanding paleoclimate and organic matter inputs in the Southern Ocean
The opening of the Tasmanian Gateway around the Eocene/Oligocene boundary is a crucial evolution stage for the formation of the Antarctic Circumpolar Current, and plays a pivotal role in global ocean circulation, regional climate, and terrestrial vegetation variations. Multiple proxies such as micro...
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| Format: | Thesis |
| Language: | unknown |
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2023
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| Online Access: | https://doi.org/10.25949/26793580.v1 https://figshare.com/articles/thesis/Biomarkers_for_understanding_paleoclimate_and_organic_matter_inputs_in_the_Southern_Ocean/26793580 |
| Summary: | The opening of the Tasmanian Gateway around the Eocene/Oligocene boundary is a crucial evolution stage for the formation of the Antarctic Circumpolar Current, and plays a pivotal role in global ocean circulation, regional climate, and terrestrial vegetation variations. Multiple proxies such as microfossils or terrestrial palynomorphs, have been used to study Paleogene tectonic, climatic, oceanographic, and vegetation evolution in the Tasmanian Gateway. However, except for glycerol dialkyl glycerol tetraethers (GDGTs) and alkenones, which contain water temperature information, biomarkers have rarely been studied in ODP Leg 189 samples. Nevertheless, they could provide useful information about organic matter input and depositional environment. This PhD thesis provides the first detailed organic geochemical analysis of hydrocarbons and biomarkers in four cores (1168, 1170, 1171, 1172) from the early Paleogene interval of Ocean Drilling Program (ODP) Leg 189 in the Tasmanian Gateway region to the south of Australia. 114 sediment samples were analysed by gas chromatography-mass spectrometry (GC-MS), including multiple-reaction monitoring (MRM) mode. Results showed that sediments are all immature with significant microbial input. Interesting polyaromatic hydrocarbon features were observed in sediments. Land-derived perylene is only concentrated at the site (1168) closest to Tasmania under dysoxic conditions, while the terrigenous-sourced organic matter was detected at all four sites. This was attributed to the short transportation distance and fast deposition rate of the organic matter, which preserve the precursors of perylene. This study indicates that perylene cannot serve as a palaeoenvironmental marker for anoxia, and sustained reducing conditions are not necessarily essential for the formation of perylene from its precursors. Unusual alkylnaphthalenes and alkylphenanthrenes isomer distributions were detected in Site 1168, with unknown terrigenous or algal-derived sources. Reworking, combustion or preferential ... |
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