The Sakmarian (Cisuralian, Permian) Fossil Cliff Member of the Holmwood Shale is situated in the northern Perth Basin, Western Australia, and consists of alternating beds of shale and silty calcarenite forming three parasequences. Within this member a diverse fauna of ostracodes and foraminifera are present. During the Cisuralian the northern Perth Basin formed part of the Gondwanan supercontinent and was linked to Greater India via an epeiric sea that opened to the north. The ostracode fauna is restricted to the calcareous beds of the member and consists of a diverse benthic fauna comprising 31 new species and 13 previously recorded species. Species from the Healdioidea, Bairdioidea, Youngielloidea, and Thlipsuroidea dominate the assemblage and suggest a normal-marine environment during the period represented by the calcareous beds, with an overall shallowing trend up the sequence. The fauna shows some similarity to faunas from the Tethyan deposits of North America and the Boreal deposits of Russia during the Late Carboniferous and Cisuralian. Twenty-eight species of foraminifera were recorded from the Fossil Cliff Member and underlying Holmwood Shale and comprise two distinct faunas, an agglutinated benthic foraminiferal fauna found within the shale beds and a calcareous benthic foraminiferal fauna present in the calcarenite units. The agglutinated foraminifera are inferred to represent deposition in dysoxic to suboxic (0.1-1.5 mL/LO2;), poorly circulated bottom waters below wave base. The calcareous foraminifera are inferred to represent deposition in normal-marine conditions. Both foraminiferal assemblages show a shallowing trend in their distribution that matches the trend identified in the ostracode fauna. Based upon the palaeoecology of the ostracode and foraminiferal faunas, the depositional environment for the Fossil Cliff Member is inferred to have been within shallow water in an epeiric basin during an overall marine regression that is overprinted by eustatic and isostatic oscillations resulting from deglaciation that occurred during the early Sakmarian (Cisuralian). These sea-level oscillations raised and lowered the oxic surface waters of the epeiric sea above and below the substrate resulting in a sparse agglutinated foraminiferal fauna or an abundant and diverse ostracode and calcareous foraminiferal fauna respectively.
| Identifer | oai:union.ndltd.org:ADTP/220969 |
| Date | January 2001 |
| Creators | Ferdinando, Darren |
| Publisher | University of Western Australia. Dept. of Geology and Geophysics |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Darren Ferdinando, http://www.itpo.uwa.edu.au/UWA-Computer-And-Software-Use-Regulations.html |
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