Quartz sand grain shape and other criteria used to distinguish glacial and non-glacial events in a marine core from Frobisher Bay, Baffin Island, N.W.T., Canada.

Analyses of quartz sand grain shape, sedimen rates and foraminifera define glacial and non-glacial episodes in a 9·69 m core from Frobisher Bay, Arctic Canada. Five radiocarbon dates on organic matter provide a preliminary core chromology, with a basal date of 11,910 yr BP. Quartz sand grain morphology is measured for samples at seven core levels using: (1) Fourier shape analysis; (2) percentage of grain surface conchoidally fractured. Samples at 2·0 and 7·5 m are most fractured an have Fourier roughness coefficients similar to the particles sampled directly from glacier ice. These two samples probably represent glacial events in the core. Major intervals of non-carbonate and influx occur at 9·0-4·5 m and 3·5-1·5 m, separated by several thousand years of slower sedimentation. Detritial carbonate influx rates are relatively high prior to 4·3 m, then decline rapidly indicating a shift in sediment provenance from limestones flooring Frobisher Bay to rafting from far-travelled icebergs. Bio- and lithostratigraphic analysis allows definition of five core units: (1) an environment similar to today below 8·5 m; (2) glacial conditions from 8·5-6·8 m, associated with ice proximal to the core site; (3) ameliorating conditions from 6·8 and 3·2m; (4) cooler conditions from 3·2 to 0&miidot;5 m, probably related to increased iceberg flux rather than neological advances of nearby ice caps; (5) an environment similar to today from 0· [ABSTRACT FROM AUTHOR]