Sedimentology and micropalaeontology of gravity cores from the N.E. Atlantic continental slope south west of Ireland

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dc.contributor.advisorRogers, Johnen_ZA
dc.contributor.authorBuck, P Jen_ZA
dc.date.accessioned2016-03-11T14:26:21Z
dc.date.available2016-03-11T14:26:21Z
dc.date.issued1988en_ZA
dc.descriptionBibliography: pages 45-55.en_ZA
dc.description.abstractEleven gravity cores from the continental margin off Eire and Land's End (SW England) were examined and found to document the major trends of the Late Pleistocene climate. Several stratigraphic indicators; - carbonate content, sediment texture, grain size, composition, nature of terrigenous components, ice-rafted debris and foraminiferal diversity were examined and show that the glacial history of the study area can be closely correlated with the palaeoclimatic evolution of the adjacent European shelf. Sediments deposited during Late Pleistocene glacial conditions show the following characteristics when compared to the surface sediments deposited under Holocene interglacial conditions: an increase in the quantity of ice-rafted debris and percentage of mica, and a notable increase in the degree of frosting and pitting of the quartz grains. Overall grain size was finer resulting in a silty sediment package. Sedimentologically the cores fall into two groups (1 and 2). The major difference being that Group 1 (located on the Pendragon Escarpment) received increased quantities of fine silts from a 'shelf spill-over' mechanism operating on the Fastnet and Western Approaches Basins, during glacial regressions. All sediment samples displayed polymodal characteristics reflecting the interaction of several different physical processes e.g. ice-rafting, contour currents etc. Striking variations in the populations of planktonic foraminifera were noted, alternating between Arctic and Sub-Arctic assemblages, reflecting the waxing and waning of glacial activity. The coccolith-carbonate minima correlate with the Arctic-fauna maxima and the ¹⁸O/¹⁶O maxima of the oxygen-isotope curves. Foraminiferal-test analysis (ratio of whole foraminifera fragmented foraminifera) revealed that no correlation existed with any of the other parameters analysed. However, the cores were severely affected by the presence of bottom currents which were strong enough to remove the fragmented tests. Parallellaminated contourites and evidence of erosion were noted in all cores. Ten cores penetrated sediments deposited during the last glacial maximum of 20,000 B.P - 18,000 B.P. near the 75cm depth mark (Core 1865 was too short to reach such sediments). However sediments reflecting the 11,000 B.P glacial readvance, detected at around the 25cm mark, were not as clearly represented. Bioturbation has smoothed the climatic record throughout the lengths of these cores and has also suppressed the high-frequency oscillations (<10³ B.P).en_ZA
dc.identifier.apacitationBuck, P. J. (1988). <i>Sedimentology and micropalaeontology of gravity cores from the N.E. Atlantic continental slope south west of Ireland</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Geological Sciences. Retrieved from http://hdl.handle.net/11427/17655en_ZA
dc.identifier.chicagocitationBuck, P J. <i>"Sedimentology and micropalaeontology of gravity cores from the N.E. Atlantic continental slope south west of Ireland."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Geological Sciences, 1988. http://hdl.handle.net/11427/17655en_ZA
dc.identifier.citationBuck, P. 1988. Sedimentology and micropalaeontology of gravity cores from the N.E. Atlantic continental slope south west of Ireland. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Buck, P J AB - Eleven gravity cores from the continental margin off Eire and Land's End (SW England) were examined and found to document the major trends of the Late Pleistocene climate. Several stratigraphic indicators; - carbonate content, sediment texture, grain size, composition, nature of terrigenous components, ice-rafted debris and foraminiferal diversity were examined and show that the glacial history of the study area can be closely correlated with the palaeoclimatic evolution of the adjacent European shelf. Sediments deposited during Late Pleistocene glacial conditions show the following characteristics when compared to the surface sediments deposited under Holocene interglacial conditions: an increase in the quantity of ice-rafted debris and percentage of mica, and a notable increase in the degree of frosting and pitting of the quartz grains. Overall grain size was finer resulting in a silty sediment package. Sedimentologically the cores fall into two groups (1 and 2). The major difference being that Group 1 (located on the Pendragon Escarpment) received increased quantities of fine silts from a 'shelf spill-over' mechanism operating on the Fastnet and Western Approaches Basins, during glacial regressions. All sediment samples displayed polymodal characteristics reflecting the interaction of several different physical processes e.g. ice-rafting, contour currents etc. Striking variations in the populations of planktonic foraminifera were noted, alternating between Arctic and Sub-Arctic assemblages, reflecting the waxing and waning of glacial activity. The coccolith-carbonate minima correlate with the Arctic-fauna maxima and the ¹⁸O/¹⁶O maxima of the oxygen-isotope curves. Foraminiferal-test analysis (ratio of whole foraminifera fragmented foraminifera) revealed that no correlation existed with any of the other parameters analysed. However, the cores were severely affected by the presence of bottom currents which were strong enough to remove the fragmented tests. Parallellaminated contourites and evidence of erosion were noted in all cores. Ten cores penetrated sediments deposited during the last glacial maximum of 20,000 B.P - 18,000 B.P. near the 75cm depth mark (Core 1865 was too short to reach such sediments). However sediments reflecting the 11,000 B.P glacial readvance, detected at around the 25cm mark, were not as clearly represented. Bioturbation has smoothed the climatic record throughout the lengths of these cores and has also suppressed the high-frequency oscillations (<10³ B.P). DA - 1988 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1988 T1 - Sedimentology and micropalaeontology of gravity cores from the N.E. Atlantic continental slope south west of Ireland TI - Sedimentology and micropalaeontology of gravity cores from the N.E. Atlantic continental slope south west of Ireland UR - http://hdl.handle.net/11427/17655 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/17655
dc.identifier.vancouvercitationBuck PJ. Sedimentology and micropalaeontology of gravity cores from the N.E. Atlantic continental slope south west of Ireland. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Geological Sciences, 1988 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/17655en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Geological Sciencesen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherMarine sediments - North Atlantic Oceanen_ZA
dc.subject.otherGeology - North Atlantic Oceanen_ZA
dc.subject.otherMicropaleontology - North Atlantic Oceanen_ZA
dc.titleSedimentology and micropalaeontology of gravity cores from the N.E. Atlantic continental slope south west of Irelanden_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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