Variations in 14C ages of various organic fractions in a turbidite sediment core from Suruga Trough.

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Abstract
Radiocarbon (14C) ages have been measured for four organic-carbon fractions, i.e., humic acid and solid organic materials of plant residues, and humic acid and humin of sandy-mud component, separated from a turbidite sediment, with a Tandetron accelerator mass spectrometer at Radioisotope Center, Nagoya University. The KT7819-24 piston-cored sediment, 275 cm in length, was collected at Suruga Trough, off Suruga Bay. The sediment materials from the lowermost turbidite bed of the cored sediment were used for the 14C analysis. Different organic fractions from the turbidite sediment showed relevant 14C ages. The nonhydrolyzable humic acid of the plant materials was the youngest, with a 14C age of 270 .+-. 80 y BP. The solid substances of the plant fragments showed a much older age of 1550 .+-. 130 y BP. The nonhydrolyzable humic acid from the sandy mud was dated to be 2270 .+-. 90 y BP, and the humin component was to be the oldest, with a 14C age of 9400 .+-. 170 y BP. Concerning the chemical and physical character of the sedimentary organics in the turbidites, and their adsorption and mixing mechanism, it is inferred that the turbidite bed was produced shortly after 1550 .+-. 130 y BP, which is the age of the solid substances of the plant residues.