|(1) Our study showed that the sediments of Kainan
Maru Seamount and Gunnerus Ridge are suitable for reconstructing the Cenozoic
palaeoenvironment, palaeoclimate and glacial history of Antarctica. The
sediments cropping out at erosional features are therefore promising targets
for further sediment sampling without the need for a drilling ship.
(2) The sediments are dominated by siliceous
oozes and siliceous muds implying deposition south of the Polar Front.
(3) Icebergs reached the area throughout the
time represented by the investigated cores. However, the intensity of ice-rafting
was very variable.
(4) The clay mineral assemblages are dominated
by illite and smectite, whereas chlorite and kaolinite occur only in traces.
Illite and chlorite are derived from physical weathering of an East Antarctic
source. Smectite and kaolinite probably are derived from the erosion of
Cenozoic or Mesozoic shelf sediments. Kaolinite also might be derived from
weathering of Permo-Triassic rocks in the hinterland of Prydz Bay.
(5) The early Oligocene sediments (30.1-29.0
Ma) indicate that surface water temperatures were high enough to allow biosiliceous
production and to make most icebergs melt south of the area. Palaeoenvironmental
conditions on Kainan Maru Seamount obviously were quite different from those
on Maud Rise and Kerguelen Plateau, which are in a similar position. This
leads to the assumption that the Southern Ocean was subdivided into different
(6) The sediments of the middle Miocene time
interval 14.1-13.5 Ma point to similar palaeoenvironmental conditions as
those of the early Oligocene. The diatom oozes deposited 13.5-13.1 Ma indicate
relative warm conditions with perennial siliceous phytoplankton production
and less glacial reworking of smectie-enriched shelf sediments. The 13.1-12.8
Ma old sediments document an intensification of East Antarctic glaciation
resulting in high concentrations of IRD.
(7) Compared to the older sediments, the late
Miocene sediments (8.7-6.5 Ma) have higher contents of poorly crystalline
and biotite-like illites and of IRD and silt. This change indicates a continued
intensification of the glaciation. The strong fluctuations in the sedimentological
parameters point to a much more dynamic ice sheet.
(8) The Pliocene sediments (5.1-2.7 Ma) show
an even more pronounced cyclic sedimentation mirroring glacial and interglacial
conditions. The duration of one cycle is about 400 ka.