Holocene accumulation rates of pelagic sediment components in the Panama Basin, Eastern Equatorial Pacific Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/4b29b856h

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  • Holocene bulk sediment and component accumulation rates were measured in twenty-eight piston and gravity cores taken from the floor of the western Panama Basin and on the surrounding ridges. Radiocarbon ages and oxygen isotope curves provided Holocene age control in nine cores. Time datums in nineteen other cores were inferred by correlation of calcium carbonate curves to the dated cores. Dry bulk densities were measured in ten cores and were estimated in the others by an empirical relationship between dry bulk density and the percentages of sand, clay, and calcium carbonate. Other studies of the textural, mineralogical and sand fraction composition of near surface sediments in these cores provided analyses which could be used to obtain accumulation rates for these components. A general similarity between the map pattern of surface productivity and the patterns of carbonate and opal accumulation rates suggests a first order control of biogenic sedimentation by fertility of surface waters. Accumulation rates of terrigenous components are highest near the continents; the map and depth patterns suggest dispersal by currents shallower than 2000 m or by winds. It is inferred from textural component accumulation rate patterns that no significant regional redistribution of sediment by winnowing occurred during the Holocene. Deposition from deep thermohaline circulation probably increased the accumulation rates of silt, clay, and opaline components in the gaps between the western and eastern troughs. Calcium carbonate accumulation rates at equal depths are generally lower within 250 km of the edge of the continental shelf. Below 2000 m in high productivity regions > 250 km from the shelf calcium carbonate accumulation rates decrease linearly with depth according to a gradient of -3.3 gm CaCO₃/cm²/1000 yrs/ km. From this gradient, two independent estimates of the lysocline in this region, and a model of calcium carbonate accumulation, the average Holocene rate of supply of calcite from the surface is calculated to be 5-10 gm/cm²/1000 yrs.
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