993 resultados para 7038-115


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Synthetic mass accumulation rates have been calculated for ODP Site 707 using depth-density and depth-porosity functions to estimate values for these parameters with increasing sediment thickness, at 1 Ma time intervals determined on the basis of published microfossil datums. These datums were the basis of the age model used by Peterson and Backman (1990, doi:10.2973/odp.proc.sr.115.163.1990) to calculate actual mass accumulation rate data using density and porosity measurements. A comparison is made between the synthetic and actual mass accumulation rate values for the time interval 37 Ma to the Recent for 1 Myr time intervals. There is a correlation coefficient of 0.993 between the two data sets, with an absolute difference generally less than 0.1 g/cm**2/kyr. We have used the method to extend the mass accumulation rate analysis back to the Late Paleocene (60 Ma) for Site 707. Providing age datums (e.g. fossil or magnetic anomaly data) are available the generation of synthetic mass accumulation rates can be calculated for any sediment sequence.

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Fil: Rodríguez Temperley, María Mercedes. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

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Fil: Rodríguez Temperley, María Mercedes. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

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Late Cretaceous fish debris from Demerara Rise exhibits a dramatic positive excursion of 8 e-Nd units during ocean anoxic event 2 (OAE2) that is superimposed on extremely low e-Nd(t) values (-14 to -16.5) observed throughout the rest of the studied interval. The OAE2 e-Nd excursion is the largest yet documented in marine sediments, and the majority of the shift is estimated to have occurred over <20 k.y. Low background e-Nd values on Demerara Rise are explained as the Nd isotopic signature of the South American craton, whereas eruptions of the Caribbean large igneous province or enhanced mixing of intermediate waters in the North Atlantic could have caused the excursion.