Clay and bulk mineralogy of ODP sites 119-745 and 119-746 from the Southern Ocean

• Main Authors: Ehrmann, Werner, Grobe, Hannes, Fütterer, Dieter K
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 1991
• Subjects: 119-745B; 119-746A; DRILL; Drilling/drill rig; Indian Ocean; Joides Resolution; Leg119; Ocean Drilling Program; ODP; Antarc*; Antarctic; Antarctica; Ice Shelves; Southern Ocean
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.587843; https://doi.org/10.1594/PANGAEA.587843

The sediments recovered at ODP Sites 745 and 746 in the Australian-Antarctic Basin are characterized by cyclic facies changes between clayey diatom oozes and diatomaceous clays ranging in age from late Miocene (about 10 Ma) to Quaternary. The gravel and terrigenous sand content of the sediments is used as an indicator of the intensity of ice rafting through time. Maxima are recorded at 8.7-7.9, 6.6-6.0, 5.0-4.4, and 4.0-3.2 Ma. The maxima in more recent times are much less pronounced and occur at 2.4-1.6 and 1.4-1.0 Ma. All sand- and gravel-sized terrigenous sediment particles are of gneissic or granitic origin and originated from the East Antarctic continent. The maxima of ice rafting recorded at Sites 745 and 746 do not appear to represent local phenomena. Rather they document major advances and decays of the Antarctic ice shelves and glaciers and therefore represent events of great importance for the reconstruction of the paleoceanography of the Southern Ocean and the glacial history of Antarctica. In general, ice rafting was pronounced in the late Miocene and early Pliocene epochs, which are characterized by repeated ice advances and retreats. Ice rafting was less intensive during the late Pliocene to Quaternary time period, when ice shelves remained relative stable. The clay minerals indicate the fluctuating influence of different source areas on the delivery of fine-grained terrigenous sediment components. Part of this material may have been delivered from the Permian Amery Formation or from equivalents of this formation.