Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 162sive. The MST data, however, have a sampling density unapproach-able by any practical scheme for discrete sampling and are collected on board with minimal effort. Changes in ice rafting on glacial–inter-glacial and suborbital tim...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.490.9988 http://www.moraymo.us/1999_Carter+Raymo.pdf |
| Summary: | Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 162sive. The MST data, however, have a sampling density unapproach-able by any practical scheme for discrete sampling and are collected on board with minimal effort. Changes in ice rafting on glacial–inter-glacial and suborbital time scales have been shown to have had a clear impact on the quantity and mineralogy of ice-rafted debris (IRD) in sediments of the North Atlantic over the last glacial cycle (e.g., Ruddiman, 1977; Bond and Lotti, 1995). Because past studies have shown that MST data sets can be useful proxies for sediment source area, transport processes, and local conditions affecting sedi-mentation, it seems likely that changes in terrigenous input by ice rafting or bottom currents could have distinct signatures in the MST data from Sites 981 and 984. Variation in GRAPE wet bulk density can reflect lithologic variability in sediments that have components of distinctly different grain density or packing efficiency. For exam-ple, GRAPE data were used as a proxy for organic carbon content at two Arabian Sea sites (Busch, 1991) and for the relative proportions of opal and carbonate in equatorial Pacific sediments (Mayer, 1991; from Site 984, representative of the full range of MST values over a long time interval, were selected for complete mineralogical and sed-imentological analysis. The mineralogy of the clay and fine silt frac-tions, grain-size distribution, weight percent CaCO3, and concentra-tions of lithic grains and foraminifers were determined for each sam-ple. These results were compared to the MST data and the benthic foraminiferal isotopic records (for 0.9–1.4 Ma only) from each site. R-mode factor analysis helped elucidate the relationships between the discrete variables and the MST data. Core Location Sediment drifts in the far North Atlantic were targeted for drilling during Leg 162 because they record physical and chemical changes in the northern downwelling limb of the global “conveyor belt.” High-latitude deep-water ... |
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