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Taphonomy, palaeoecology and taxonomy of an ophiuroid-stylophoran obrution deposit from the Lower Devonian Bokkeveld Group, South Africa
The Lower Devonian Voorstehoek Formation is a fossil-rich, siliciclastic unit (Ceres Subgroup, Bokkeveld Group, Cape Supergroup) in South Africa. This Emsian unit contains a highly endemic benthic fossil biota characteristic of the cool to cold water Malvinokaffric Realm of southwestern Gondwana. Th...
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| Format: | Thesis |
| Language: | English |
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Department of Geological Sciences
2017
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| _version_ | 1867613157493571584 |
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| access_status_str | Open Access |
| author | Reid, Mhairi |
| author2 | Taylot, Wendy |
| author_browse | Reid, Mhairi Taylot, Wendy |
| author_facet | Taylot, Wendy Reid, Mhairi |
| author_sort | Reid, Mhairi |
| collection | Thesis |
| description | The Lower Devonian Voorstehoek Formation is a fossil-rich, siliciclastic unit (Ceres Subgroup, Bokkeveld Group, Cape Supergroup) in South Africa. This Emsian unit contains a highly endemic benthic fossil biota characteristic of the cool to cold water Malvinokaffric Realm of southwestern Gondwana. The palaeontological and sedimentological investigations of the Voorstehoek Formation suggest that deposition took place in a shallow marine environment within the storm influenced, proximal part of an offshore transition zone. A relatively diverse, ophiuroid–stylophoran assemblage, well-preserved in the Karbonaatjies obrution bed, was excavated at the study site in the Hex River Pass, Western Cape. In this study the taphonomy, taxonomy and the palaeoautecology of Palaeozoic ophiuroids and stylophorans was investigated using micro CT scans. Over 60 samples were scanned, manually segmented and stitched together to create a virtual 3D model of a portion of the Karbonaatjies obrution bed. This method allowed for the determination of the degree of fossil articulation, fossil orientation and faunal counts, without damaging the delicate echinoderm fossils. Furthermore, the ability to digitally analyse the fossil-rich bed has revealed an echinoderm assemblage composed of over 700 articulated ophiuroids dominated by a proposed new genus and species Gamiroaster tempestatis, over 145 articulated mitrate stylophorans Paranacystis cf. petrii Caster, 1954 and eight Placocystella africana (Reed, 1925). Taphonomic analysis of this ophiuroid–stylophoran assemblage indicates this obrution deposit formed due to rapid burial that smothered a potentially gregarious community during a single storm event. Additionally, the admixture of skeletal debris and intact echinoderms present in the Karbonaatjies obrution bed reflects a complex history with significant time-averaging. This unique assemblage provides a taphonomic window into the marine ecosystems of the Early Devonian, including the structure of an unusual, echinoderm-dominated benthic community that forms part of a much wider fossil biota from the Falkland Islands and Precordillera of Argentina, which formed part of SW Gondwana. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/25404 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:31:41.113Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2017 |
| publishDateRange | 2017 |
| publishDateSort | 2017 |
| publisher | Department of Geological Sciences |
| publisherStr | Department of Geological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/25404 Taphonomy, palaeoecology and taxonomy of an ophiuroid-stylophoran obrution deposit from the Lower Devonian Bokkeveld Group, South Africa Reid, Mhairi Taylot, Wendy Bordy, Emese M Geology The Lower Devonian Voorstehoek Formation is a fossil-rich, siliciclastic unit (Ceres Subgroup, Bokkeveld Group, Cape Supergroup) in South Africa. This Emsian unit contains a highly endemic benthic fossil biota characteristic of the cool to cold water Malvinokaffric Realm of southwestern Gondwana. The palaeontological and sedimentological investigations of the Voorstehoek Formation suggest that deposition took place in a shallow marine environment within the storm influenced, proximal part of an offshore transition zone. A relatively diverse, ophiuroid–stylophoran assemblage, well-preserved in the Karbonaatjies obrution bed, was excavated at the study site in the Hex River Pass, Western Cape. In this study the taphonomy, taxonomy and the palaeoautecology of Palaeozoic ophiuroids and stylophorans was investigated using micro CT scans. Over 60 samples were scanned, manually segmented and stitched together to create a virtual 3D model of a portion of the Karbonaatjies obrution bed. This method allowed for the determination of the degree of fossil articulation, fossil orientation and faunal counts, without damaging the delicate echinoderm fossils. Furthermore, the ability to digitally analyse the fossil-rich bed has revealed an echinoderm assemblage composed of over 700 articulated ophiuroids dominated by a proposed new genus and species Gamiroaster tempestatis, over 145 articulated mitrate stylophorans Paranacystis cf. petrii Caster, 1954 and eight Placocystella africana (Reed, 1925). Taphonomic analysis of this ophiuroid–stylophoran assemblage indicates this obrution deposit formed due to rapid burial that smothered a potentially gregarious community during a single storm event. Additionally, the admixture of skeletal debris and intact echinoderms present in the Karbonaatjies obrution bed reflects a complex history with significant time-averaging. This unique assemblage provides a taphonomic window into the marine ecosystems of the Early Devonian, including the structure of an unusual, echinoderm-dominated benthic community that forms part of a much wider fossil biota from the Falkland Islands and Precordillera of Argentina, which formed part of SW Gondwana. 2017-09-26T14:56:12Z 2017-09-26T14:56:12Z 2017 Master Thesis Masters MSc http://hdl.handle.net/11427/25404 eng application/pdf Department of Geological Sciences Faculty of Science University of Cape Town |
| spellingShingle | Geology Reid, Mhairi Taphonomy, palaeoecology and taxonomy of an ophiuroid-stylophoran obrution deposit from the Lower Devonian Bokkeveld Group, South Africa |
| thesis_degree_str | Master's |
| title | Taphonomy, palaeoecology and taxonomy of an ophiuroid-stylophoran obrution deposit from the Lower Devonian Bokkeveld Group, South Africa |
| title_full | Taphonomy, palaeoecology and taxonomy of an ophiuroid-stylophoran obrution deposit from the Lower Devonian Bokkeveld Group, South Africa |
| title_fullStr | Taphonomy, palaeoecology and taxonomy of an ophiuroid-stylophoran obrution deposit from the Lower Devonian Bokkeveld Group, South Africa |
| title_full_unstemmed | Taphonomy, palaeoecology and taxonomy of an ophiuroid-stylophoran obrution deposit from the Lower Devonian Bokkeveld Group, South Africa |
| title_short | Taphonomy, palaeoecology and taxonomy of an ophiuroid-stylophoran obrution deposit from the Lower Devonian Bokkeveld Group, South Africa |
| title_sort | taphonomy palaeoecology and taxonomy of an ophiuroid stylophoran obrution deposit from the lower devonian bokkeveld group south africa |
| topic | Geology |
| url | http://hdl.handle.net/11427/25404 |
| work_keys_str_mv | AT reidmhairi taphonomypalaeoecologyandtaxonomyofanophiuroidstylophoranobrutiondepositfromthelowerdevonianbokkeveldgroupsouthafrica |