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Palaeoenvironmental implications of Tertiary sediments from Kainan Maru Seamount and northern Gunnerus Ridge

Published online by Cambridge University Press:  02 December 2003

CLAUS-DIETER HILLENBRAND
Affiliation:
Alfred Wegener Institute for Polar and Marine Research, PO Box 12 01 61, D-27515 Bremerhaven, Germany, [email protected]
WERNER EHRMANN
Affiliation:
University of Leipzig, Institute for Geophysics and Geology, Talstrasse 35, D-04103 Leipzig, Germany

Abstract

Sedimentary sequences spanning early Oligocene and Neogene time intervals were recovered with piston and gravity cores along erosional structures at northern Gunnerus Ridge and Kainan Maru Seamount in the southernmost Indian Ocean. Results of sedimentological investigations help to reconstruct the Cenozoic palaeoenvironment. Main emphasis was placed on grain size and clay mineral data. The clay mineral assemblages are dominated by illite and smectite. Chlorite and kaolinite occur in trace amounts. Whereas illite has a distinct source on the East Antarctic craton, smectite is of somewhat speculative origin, but probably is derived from erosion of Cenozoic or older shelf sediments. The presence of terrigenous sand indicates that ice-rafting was active throughout the time represented by the investigated cores, although with varying intensity. During the early Oligocene interval (30.1–29.0 Ma), siliceous phytoplankton production dominated sedimentation. Environmental conditions were quite different from those on Maud Rise and Kerguelen Plateau. The middle Miocene sedimentary sequence (14.1–12.8 Ma) documents an intensification of East Antarctic glaciation. The sediments deposited during the late Miocene interval (8.7–6.5 Ma) and the Pliocene interval (5.1–2.7 Ma) indicate continued cooling of Antarctica, but a more dynamic Antarctic ice sheet resulting in episodic sedimentation patterns.

Type
Research Article
Copyright
© Antarctic Science Ltd 2003

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