10 Be, 14 C and U-Th decay series nuclides and δ 18 O in a box core from the Central North Atlantic

• Main Authors: Somayajulu, B. L. K., Sharma, P., Berger, W. H.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier Science 1984
• Subjects: QE Geology; North Atlantic
• Online Access: http://repository.ias.ac.in/49776/; http://www.sciencedirect.com/science/article/pii/0025322784900367

The stratigraphy of several radioisotopes has been determined in an undisturbed core from the central north Atlantic ( 14 C, 238 U, 230 Th, 232 Th, 226 Ra, 210 Pb, 10 Be). Carbon-14 indicates a sedimentation rate of 1 cm 1000 yrs −1 . The core represents about 30,000 years. The oxygen isotope signal agrees with this scale. The δ 18 O range is about 1.5%., from glacial to Holocene. The maximum change is near 11,000 years B.P. Mixing effects are minor because of the low fertility of the overlying waters. Excess lead-210 shows a minimum between 1 and 2 cm depth, and a maximum immediately below. It does not yield a diffusion coefficient for the Goldberg and Koide (1962) mixing model. The 10 Be concentration in the Holocene sediment (on a CaCO 3 -free basis) is somewhat higher than that deposited during the previous cold period. However, both clay and 10 Be deposition rates are lower by a factor of over two during the Holocene. The source of the excess 10 Be in the glacial section could be a continental reservoir or increased cosmic ray production. The U and Th concentrations as well as the excess 230 Th/ 232 Th activity ratios of the sediment deposited during the Holocene are higher (by 30-100%) than in glacial sediments. Again, this is in contrast to the deposition rates of U and Th, which are lower in the Holocene by a factor of about two. The most reliable signals are the radiocarbon and the oxygen isotope stratigraphy.