Recognition and Sedimentologic Description of Recent Debris Flow Deposits from the Ross and Weddell Seas, Antarctica

ABSTRACT The Antarctic continental margin is inferred to be an active site of debris flow deposition and an ideal place to study these deposits. Although similar to the poorly sorted glacial-marine sediments from which they are derived, debris flow deposits can be distinguished, using textural criteria, from sediments deposited by floating ice. Antarctic debris flow units are poorly sorted, massive, texturally homogeneous throughout their thickness, and have sharp upper and lower boundaries. A crudely developed pebble fabric may be present in some units and all contain displaced shelf faunas or are unfossiliferous. Deposits from floating ice are poorly sorted, stratified, bimodal, and texturally heterogeneous within a single unit. They have gradational contacts and a crudely developed pebble f bric. These textural characteristics are useful in distinguishing debris flow deposits from floating ice sediments in the ancient record. No reliable textural criteria were found for differentiating between ancient debris flow deposits and tillites deposited by grounded ice.