Skeletal and Isotopic Composition and Paleoclimatic Significance of Late Pleistocene Carbonates, Ross Sea, Antarctica

Abstract

ABSTRACT Carbonates cover an extensive area of the northwestern Ross Sea continental shelf. Radiocarbon dates yield late Pleistocene (Stage 3) ages for these deposits, hence the carbonates appear to be correlative with widespread tills and glacial marine deposits in the region. Four carbonate facies are recognized on the basis of skeletal composition: a barnacle/foraminifer facies, a muddy bryozoan facies, a bryozoan/barnacle/pelecypod/foraminifer facies, and a planktonic foraminiferal facies. These deposits occur on the shelf and upper slope, while carbonate turbidites derived from them occur on the adjacent continental slope and rise. Compositional analyses of Ross Sea carbonates lend support to previously recognized criteria for identifying cold water carbonates. These include: 1) the presence of an associated ice-rafted component (including dropstones); 2) a dominance of calcite relative to other carbonate minerals (the remaining fraction consists solely of aragonite); 3) allochems that are entirely skeletal; and 4) heavy oxygen isotopic compositions (in the range of + 3.0 to +5.1% PDB).