Late Pleistocene Palaeo Environment Reconstruction from 3D Seismic data,
NW Australia.The ACROSS project - Australasian Research: Origins of
Seafaring to Sahul.
Abstract
The earliest human migration from Sunda (South-East Asian archipelago)
to Sahul (Australia and New Guinea) is still heavily debated with
proposed timings between c.65-45kaBP depending on the evidence base and
interpretation of the data. As part of the EU funded ACROSS project,
focused on the mode and route of early migration in to SAHUL, we are
undertaking an integrated interpretative study of the evolving submerged
landscapes for the Late Pleistocene of the NW Australian Shelf. Oil and
gas industry 3D and 2D seismic data, with some core/borehole data, are
being used to determine lowstand palaeo-environments and shoreline
positions. This information is informing modelling of ocean tide and
current patterns that may have been influenced. The seismic is being
interpreted supplemented by using time-slices on relative impedance
inverted post-stack data. Layer stripping, seismic geomorphology,
sequence boundary and depth analysis are being applied to datasets in
the Bonaparte Basin, Kimberley Shelf and Arafura regions of Australia’s
North-West Shelf area. Interpretation of the seismic data is constrained
by dated stratigraphy in shallow cores with lower bounds determined from
oil/gas well bores. MIS stages 1-4 are identified, however, the seismic
response is a composite of time periods due to varying sedimentation
rates, non-depositional hiatuses and minimal vertical seismic travel
time covering this interval which limits the analysis to the top 50ms
TWT (c. 40-45 m) of events below the seabed. This paper reviews the
workflows that have been developed to maximise the fine scale detail
that can be recovered for a range of terrestrial and marine
environments. Procedures include inverse-Q, impedance inversion,
spectral decomposition and time-slicing relative to seabed. High
resolution 2D seismic data is also being used to augment and inform the
interpretation of the conventional oil/gas 3D seismic data. Data
examples will be presented showing the geomorphological characteristics
(river channels, avulsions, levees, drainage channels, dunes and near
shore carbonate reefs) of the lowstand and transgressive landscapes
during this period. The palaeo-reconstructions are now being developed
from the interpreted seismic geomorphology for the specific
consideration of human seaborne travel.