麻豆传媒

The late Quaternary history of the Baffin Bay area has been investigated using piston/gravity cores, grab samples and seismic profiles. Six lithofacies have been characterized in more than 50 cores. Correlation in cores has been established on the basis of several distinct lithological units, three prominent volcanic ash zones, the occurrence and abundance of micro fossils and paleomagnetic inclination and declination. The stratigraphic sequence has been placed into a time framework using 14C dates and the oxygen isotopic curves from two cores.

Detailed mineralogical and sedimentological analyses were carried out and the facies have been characterized on the basis of their mineralogical and sedimentological properties. Numerous potential source rocks and sediment transporting / depositing mechanisms have been assigned for the facies.

The benthic and planktonic foraminifera have been used together with oxygen isotopic data to investigate the preservation state of biogenic carbonate. It is found that carbonate cycles were largely a function of dissolution cycles.

The oxygen isotope curves have been used to investigate the paleoclimatology of Baffin Bay and Davis Strait and four long term climatic cycles varying in length from 67,000 to 115,000 years have been identified in the last 400,000 years, leading to interglacial conditions that started at about 13,000, 128,000, 195,000 and 297,000 yr BP.

Planktonic foraminiferal assemblages, deposition of volcanic ashes and ice rafting have been used together with oxygen isotope curves to investigate the paleoceanography in the area. The major oceanic currents showed a cyclic pattern: during glacial periods one major current, initiating from the northward advection of the North Atlantic sub polar water dominated the circulation pattern. Interglacial periods were characterized by the presence of two oppositely flowing currents.

A cyclic sedimentation pattern was developed in Baffin Bay as a response to the change in climate. The glacial strata were composed primarily of turbidites and debris flow deposits interbedded with ice rafted debris and hemipelagic sediment, whereas interglacial strata were composed predominantly of ice rafted and hemipelagic sediments.

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Supervisor: D. J. W. Piper