Ho Il Yoon, Byong Kwon Park and Yeadong Kim
Korea Ocean Research and Development Institute
Polar Sciences Laboratory,
Ansan, P.O. Box 29, Seoul 425-600
E-mail:
hiyoon@kordi.re.kr
bkpark@korp.re.kr
ydkim@kordi.re.kr

The formation of layered biogenic sediments in many places has been ascribed to the results of inhibition of benthos by low concentrations of dissolved oxygen either in anoxic silled basins or beneath zones of strong upwelling, where an oxygen minimum layer intersects the shelf or slope. A second possibility is that the layered diatom ooze (LDO) formed as a consequence of higher settling fluxes of biogenic ooze caused by increased primary production connected either with more intense frontal system or chemically proliferous surface ocean. Sedimentological, micropaleontological and porewater data of two piston cores from central Bransfield Strait, northern Antarctic Peninsula have been used to infer the depositional environment for LDO interval encountered at the bottom of the cores. The LDO has high contents of organic carbon and sulfide sulfur. Positive relationship between organic carbon and sulfide sulfur establishes the existing of an oxidizing condition during the deposition of the LDO. The occurrence of intact diatom, Chaetoceros resting spore, in the LDO implies mass sedimentation of diatom floccules at approximately 2,500 yrs BP (the onset of the Neoglacial or the termination of Hypsithermal Warm).

We also report that in a gravity core from eastern Bransfield Strait, LDO that occurs persistently through most of the core, indicative of presently forming diatom mat. We adduce evidences that this LDO can be caused by enhanced biological activity at the ice-shelf margin in northwestern Weddell Sea, combined with mass sinking of phytoplankton blooms through the deep water convection. These remarkable deposits should enable quantification of ancient deep-sea fluxes and the study of short-term climatic fluctuations during the late Holocene.