Sediment accumulation rates west of the Mid-Atlantic Ridge ([formula omitted

Abstract

Although carbonate curves have a long history of use for temporal correlation, only limited agreement concerning the reasons for down-core carbonate variations has been reached. In this study these variations are examined by analyzing absolute accumulation rates of both carbonate and terrigenous sediment components. Carbonate content was determined in nine cores from approximately 3000–5000 m water depth. Down-core variation in carbonate was correlated to an oxygen isotope curve to establish a down-core time stratigraphy.Weight percent carbonate, carbonate accumulation rate, and terrigenous sediment accumulation rate were plotted as a function of water depth and time (0–130,000 yrs B.P.). The weight percent carbonate plot indicates that carbonate content decreases with increasing water depth. However, the carbonate accumulation rate data demonstrates that this decrease in weight percent carbonate does not result from a decrease in the carbonate accumulation rate in the deeper cores. The accumulation rate of carbonate actually increases in these deep cores. The increase in carbonate accumulation rate is offset by a larger increase in the accumulation rate of terrigenous sediment resulting in a decrease in weight percent carbonate. High accumulation rates of both carbonate and terrigenous sediment in cores below 4250 m appears to result from transport and redeposition of sediment. Most of the carbonate sediment deposited in these deep cores appears to be derived from shallow areas of the Mid-Atlantic Ridge (MAR); the terrigenous sediment probably results from deposition by deep currents.