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Deposition of the pre-glacial unit started with the opening of the Weddell Sea and
terminated around early Oligocene (145
34Ma) from our tentative age model. Due to
the fact that this unit experienced a very long deposition history, we expected to
-
nd a
mass of sediment, particularly at southern margin and continental shelf where the
Weddell Sea basin was the earliest spanned. As illustrated in transect A (Fig.
2
)
(Huang et al.
2014
), we observed a large amount of sediments up to 4 km deposited
with quite high sedimentation rate (30.1
44.5 m/Myr) on the slope of continental
margin in front of Filchner-Ronne Ice Shelf. The pre-glacial sedimentation processes
were likely dominated by thermal lithospheric subsidence and variations in terrige-
nous sediment supply as well as it very long depositional history.
Transitional unit started at the Eocene/Oligocene boundary and lasted until the
middle Miocene based on our age model. In comparison with the pre-glacial unit,
the transitional unit yields relatively higher sedimentation rates (14.6
-
78.4 m/Myr)
with thinner sediments layers, particularly, in the central and the western Weddell
Sea. For instance, point 1 shows a sedimentation rate of 78.4 m/Myr, we suggest it
is probably related to several ice sheet retreats and advances. Gravel- and pebble-
grade IRDs (Ice Rafting Debris) have been observed in middle to lower Oligocene
sediments of ODP Leg 113 Site 693 (Barker et al.
1988
). This implies that glaciers
were grounded close to the coast or on the inner shelf at that time (Barker and
Thomas
2004
). We see no obvious evidence to conclude that a major WAIS was
grounded on the inner shelf of the Weddell Sea in the Oligocene. The developing
and
-
fluctuating Antarctic ice sheets have supplied sediments which interacted with
intensi
fl
cant role in
transporting and distributing sediments, particularly after the opening of Drake
Passage/Scotia Sea gateway and intensi
ed ocean circulation in the Weddell Sea to play a signi
cation of the ACC (Huang et al.
2014
).
Sedimentary process in the Weddell Sea is signi
uenced by glacial ice
shelf dynamics. We observed relative thick sediment deposited with very high
sedimentation rates (Fig.
5
), particularly on southern continental margin and wes-
tern continental rise in the Weddell Sea (points 1
cantly in
fl
4) during full glacial time. One
explanation is that the ice sheets advanced to the shelf edge and trigger enormous
gravitational sediment, which was transported from continent to the margin and
deep sea (Huang et al.
2014
). Multiple evidences supported that the signi
-
cant ice-
sheet expansion happened during the middle Miocene (12 Ma) from previous
studies (Miller et al.
1990
; Rogenhagen et al.
2004
). The pronounced global
increase in
18
O ratios from benthic foraminifera indicated that the ice sheet was
built up since the middle Miocene (Zachos et al.
2008
). A major sea level fall is
likely represents the development of polar desert conditions with a permanent ice
cap in Antarctica (Kennett and Hodell
1996
). The
δ
cant observations of
IRDs and turbidite units are reported from the middle Miocene of ODP sites 693,
indicating the presence of ice sheets grounding on the shelves and generating a
large in
first signi
ux of sediments to the Weddell Sea basin (Barker et al.
1988
; Kennett and
barker
1990
). ODP leg 113 Site 694 also reported glacial turbidity units indicated
those grounded ice sheets were present and drained into Weddell Sea basin in
Miocene (Barker et al.
1988
; Miller et al.
1990
; Maldonado et al.
2005
,
2007
;
Leitchenkov et al.
2008
, Anderson et al.
2011
).
fl
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