Remote Sensing and Gravity interpretation ofNW Borneo: Integrated Basin Analysis on a GIS platform

Geographic Infonnation System (GIS) and remote sensing were applied and used
to study the geological evolution of the sedimentary basin of NW Borneo. For this
study, Landsat, SRTM, bathymetry and satellite derived gravity data were
integrated, manipulated and visualized in a GIS platfonn by using the capabilities
of the GIS software. The onshore region was studied by perfonning lineament
interpretation using Landsat images and SRTM data, whereas in the offshore
region bathymetry and gravity data were used to study the lithosphere of the
region by gravity modelling.
Lineament interpretation was done by using maps that were generated from the
SRTM data (e.g. hillshade and contour maps) viewed concurrently with the
Landsat images. Using the GIS tools, gravity and bathymetry data of offshore NW
Borneo were extracted to study the lithosphere of this region. The area studied
crosses the Dangerous Grounds, Sabah Trough and the Sabah Basin. The
lineament trend was interpreted to be evolving !Tom W-E in southwestern
Sarawak to NE-SW in the central region onto Sabah, and finally ending in anE-W
trend at the northern tip of Sabah. This dynamic change in orientation, coupled
with cross-cutting NW-SE lineaments, support the evidence ofmultiphase tectonic
evolution that might result in the series of episodes of subduction and collisions
during the geological history ofNW Borneo.
For gravity interpretation, the principles of Airy isostasy were used together with
the current tectonic model of NW Borneo to model the crust structure to agree.
The resulting interpretation shows that the offshore region of NW Borneo is
underlain by attenuated crust where the crust is thinnest beneath the Sabah
Through.
This thinned crust is buried underneath prograding sediments of the Sabah margin
overlying accreationary prism fonned during subduction. The thin subducting
crust is the remnant of the extended and attenuated continental rragment of
Dangerous Grounds.