Glacial marine sedimentation in the Weddell Sector of the East Antarctic Rise
Harlan, Janis G.
Anderson, John B.
Master of Arts
Seventeen cores were taken by John Anderson and Dennis Kurtz along two shelf-to-rise transects in the northeastern Weddell Sea during January-February 1978 as part of Islas Orcadas cruise 1578. These cores were examined by Wright (198) for mass flow characteristics and by Harlan for paleooceanography. The initial study showed that both shelf cores were comprised of basal till, twelve out of the fifteen slope-to-rise cores were mass flow deposits, and only three represented normal hemipelagic sedimentation. In this study, the three deepest rise cores were extensively analyzed to obtain sediment types and foraminifera for paleooceanography. All three cores were found to be composed predominantly of silt and sandy silt. Sediment types in the eastern Weddell Sea were analyzed as to size frequency distribution. These types were utilized to determine textural variation in each core. Each sediment type was further examined to determine paleocurrent velocities in this area. Bottom water activity was found to be persistently low in the eastern Weddell Sea. Morphological glauconite occurs throughout the cores and indicates slow sedimentation. Only two foraminlferal assemblages were found in these cores, a Uviqerina assemblage, believed to represent somewhat warmer water than present, and a Globocassidulina assemblage. Both faunas are restricted to Brunhes deposits. The overall depositional environment in this area appears to be characterized by low current activity and normal continental rise sedimentation, as evidenced by fine-grained, fairly sorted material Interspersed with Infrequent sediment slumping from the upper slope and intermittent ice-rafting of sediment. This contrasts sharply with the paleocirculation record of the western Weddell Sea, which is indicative of periodic bottom water activity.