麻豆传媒

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M. Sc. Thesis

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Piston cores, 8-12 m long, were collected from the tops of seamounts southwest of the Grand Banks. They were examined for climatic signature and change in the sedimentation pattern. The cores consist of alternating clays and foramnanno ooze. They were dated by C14 paleomagnetism and foraminifera and coccolith biostratigraphy. Foraminifera and carbonate cycles were used for paleoclimatic determinations. They indicate that Eastern Canada was deglaciated three times during the last 600,000 years B.P. Deglaciation occurred at 11,000 years B.P., 130,000 years B.P. and 600,000 years B.P. (although the 600,000 years B.P. date is open to question and could be younger). They probably correspond to the classical Holocene Epoch, Sangamon and Yarmouthian Interglacials. In addition three interstadials occurred in the Wisconsinan and two in the Illinoian stage.

The data from the cores allows reconstruction of the following events. With the advance of continental ice, the Gulf Stream moved towards the southeast and there was southward penetration of a cold water front. With the decrease of temperature, bottom current activity also increased. Biogenic productivity was greatly reduced and the faunal and floral assemblages changed. Advance of the ice sheets on the continental shelf and eustatic lowering of the sea level resulted in increased clastic sediment supply on the outer-continental margin. The provenance of the clays deposited during the glacial stages can be determined from their mineralogy. The Early Illinoian sedimentation pattern was controlled by the advance of an ice sheet across Newfoundland. The Laurentian ice sheet eroded the Gulf of St. Lawrence and the Laurentian Channel in the Late Illinoian. Sediment contribution from the Wisconsin ice sheet was relatively small.

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Supervisors: D. J. W. Piper / H. B. S. Cooke