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The sedimentology of Holocene Prydz Bay : sedimentary patterns and processes

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Franklin, D (1997) The sedimentology of Holocene Prydz Bay : sedimentary patterns and processes. PhD thesis, University of Tasmania.

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Abstract

Material being deposited in Prydz Bay is glaciogenic, aeolian, and biogenic.
Terrigenous material is entrained by basal glacial erosion and introduced to the
sea via iceberg rafting, meltout, and rollover in the periphery of Prydz Bay
where iceberg drift tracks are determined by ocean currents. It accounts for the
deposition of about 8 Mt a-1
.
Aeolian processes transport debris from coastal oases into the manne
environment in the summer or onto fast sea-ice during the winter. Sea-ice
breaks out and releases the debris into the water column as it melts within a
few hundred kilometres ofthe source, accounting for approximately 1 Mt a-1 of
sediment.
The skeletons of phytoplankton settle to the sea floor directly or via the faecal
pellets of predacious zooplankton. Although production is geographically
uniform, the deposition of the resultant ooze depends on bottom currents
concentrating the fine material in deep water basins ( eg. Amery Depression).
Approximately 0. 7 5 Mt of such material is deposited annually.
The deposition of the remains of calcareous organisms is important in water
depths above 400 m, mainly on the shelf break, due to a shallow Calcite
Compensation Depth and Lysocline. Approximately 0.5 Mt of calcite is
deposited annually.
Sediments are reworked by iceberg turbation between 200 and 720 m water
depth producing iceberg turbate, an admixture of the current sediment supply
and underlying relict tills. Elsewhere, the sediment is a Siliceous Mud and
Ooze (SMO) which broadly represents the contemporary sediment supply.
Sedimentation rates are at the lower end of the range of Antarctic rates:
between 0.08 mm a-1 and 0.16 mm a-1
. Were the sediments sourced from the
Lambert Glacier, sedimentation rates would be an order of magnitude higher, indicating that the source of the glacial constituent is smaller, probably the
glaciers along the coast. As such, sedimentary changes in Prydz Bay during
the Holocene are indicative of small scale climate change rather than any large
scale change required to affect the Lambert Glacier catchment.
The sub-surface sedimentology offshore from the Smsdal Glacier indicates that
a significant marine influence existed in the area during the last glacial
maximum, and the Lambert Glacier was not grounded in the Svenner Channel
during this period. The sub-surface geology of Heidemann Valley in the
Vestfold Hills also suggests that ice extent during the last glacial maximum was
not as extensive as previously thought, with glacial ice not extending as far as
the coast.

Item Type: Thesis (PhD)
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Date Deposited: 25 Jun 2012 08:05
Last Modified: 11 Mar 2016 05:55
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