The geochronology, palaeoenvironments and palaeontology of Robertson Cave inner chamber, Naracoorte.
| dc.contributor.author | Robertson, B. | |
| dc.contributor.school | School of Physical Sciences | en |
| dc.date.issued | 2022 | |
| dc.description | This item is only available electronically. Whole thesis (as available). | |
| dc.description.abstract | Robertson Cave inner chamber within the Naracoorte Cave Complex (NCC) preserves a 4m sedimentary infill record that is relatively unexplored in terms of geochronology and paleoenvironmental history. The inner chamber of this cave also preserves undated megafauna remains and fossil evidence for long-term overwintering activities of the Southern Bent-Wing bat, a critically endangered species with only two known maternity caves in Australia. This thesis aims to provide a detailed geochronology (single-grain OSL dating) and geochemistry (XRF, XRD) study of the inner chamber to better contextualise the palaeontological, palaeoenvironmental and palaeoconservation significance of the Robertson Cave sedimentary sequence. The suitability of OSL dating in this deep cave setting is demonstrated by examining a modern surface sample and two samples from complex sediment horizons affected by syn-depositional mixing (i.e. entrainment and re-transportation of pre-existing sediments within the closed cave environment). These suitability tests confirm that the OSL signal is fully reset prior to entering the cave, providing a modern age of 0ka, and that it is advisable to employ statistical models (minimum age models) that target the most recently reset grain populations when dating deep cave sediments affected by syn-depositional mixing. Twelve single-grain OSL samples from the Inner Chamber excavation provide stratigraphically consistent ages spanning 74.6-10ka, demonstrating that the infill sequence covers a much longer time period than indicated by radiocarbon dating. The entire sequence was deposited between MIS (marine isotope stage) 4 or late MIS5 to early MIS1, with high sedimentation rates evident in late MIS3 (40.5-32.3ka), the MIS2 glacial (26.5-11.8ka) and early MIS1 (11.5-9.8ka), and disconformities coinciding with major climatic transitions at the MIS4/3, MIS3/2 and MIS2-1 boundaries. Two OSL ages from the lowermost unit constrain the timing of in situ megafauna fossils to 74.6-60.1ka, meaning Robertson Cave inner chamber is one of only three well-dated NCC caves preserving late MIS5 to MIS4 megafauna remains. XRF and XRD analyses indicate the presence of multiple guano-rich layers with elevated sulphate, phosphate, organics, and trace metal concentrations. These results imply complex diagenetic processes and reinforce the fossil bat record by confirming an intermittent geochemical signature of bat overwintering activities at Robertson Cave extending back to the last interglacial complex. The findings of this study have broader implications for understanding how sediment accumulation dynamics of NCC roof window cavities can be closely tied to changing climate conditions associated with glacial-interglacial cycles. The results also reinforce the palaeontological and palaeoconservation significance of Robertson Cave, particularly the long-term resilience of its critically endangered Southern Bent-Wing bat populations and their ability to adapt to widely varying climate regimes prior to European colonisation. | |
| dc.description.dissertation | Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, YEAR | |
| dc.identifier.uri | https://hdl.handle.net/2440/146275 | |
| dc.language.iso | en | |
| dc.provenance | This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the author of this thesis and do not wish it to be made publicly available, or you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals | en |
| dc.subject | Honours | |
| dc.subject | Geology | |
| dc.subject | Robertson Cave inner chamber | |
| dc.subject | OSL dating | |
| dc.subject | geochronology | |
| dc.subject | Naracoorte Caves | |
| dc.subject | Southern Bent-wing bats | |
| dc.subject | palaeoenvironments | |
| dc.title | The geochronology, palaeoenvironments and palaeontology of Robertson Cave inner chamber, Naracoorte. | |
| dc.type | Thesis |
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