DIATOM DISTRIBUTION IN SOUTHERN-OCEAN SURFACE SEDIMENTS (ATLANTIC SECTOR) - IMPLICATIONS FOR PALEOENVIRONMENTAL RECONSTRUCTIONS

A study of 230 surface sediment samples collected in the Atlantic sect or of the Southern Ocean between the southernmost Weddell Sea and the Subtropical Zone documents the modern distribution of diatoms revealin g patterns of paleoenvironmental significance. Estimations of diatom v alves per gram dry sediment display numbers of (50-200) x 10(6) in the zone of high opal burial located between the mean position of the win ter sea ice edge and the Polar Front and maximum valuer of greater tha n 200 x 10(6) in the near-shore sedimentary basins off the Antarctic P eninsula. Lowest diatom concentrations and assemblages strongly affect ed by dissolution were encountered in the Weddell Basin. Despite alter ation of the diatom assemblages prior to their incorporation into the sediment record, the biogeographic distribution and the abundance patt ern of most of the 35 studied diatom species shows a close relationshi p with the surface hydrography (water temperature). These relationship s can be used to estimate past surface water temperatures based on sta tistical treatments of the assemblages or on simple relations of speci es occurrences in the geological record. Another close link occurs bet ween the distribution of sea ice and sea ice related diatoms. (C) Else vier Science B.V.