ABSTRACT: A Comparison of Two Late Pleistocene Shelf
Edge Deltas (Indonesia and Gulf of Mexico)--Stratigraphic Architecture,
Systems
Tracts
,
Bounding Surfaces, and Reservoir Potential
ROBERTS, HARRY H., CSI, Louisiana State Univ., Baton Rouge, LA 70803; JOHAN SYDOW, BP Amoco, Houston, TX 77210-4587; JOHN ROBALIN, Marathon, Houston, TX 77056; RICHARD FILLON, 3730 Rue Nichole, New Orleans, LA 70131
Thousands of kilometers of high-resolution seismic data were collected over two late
Pleistocene shelf-edge deltas in very different Settings, the northern Gulf of Mexico and
the eastern shelf of Borneo in Indonesia. Both deltas were constructed by
falling-to-lowstand deposition associated with the latest Pleistocene glacial maximum, the
former by the temperate Mobile River, the latter by the equatorial Mahakam River. Four
cores provide detailed stratigraphic control for the Mobile River delta while one long
boring and numerous piston and vibracores provide stratigraphic control on the Mahakam
delta. Systems
tracts
and key bounding surfaces have been related to the eustatic
sea
level
curve in both settings over ca. 125 ka. Sequence architectures differ significantly,
an important consequence of different depositional settings. The tropical Mahakam shelf is
tectonically active with low wave energy, strong oceanic currents, upwelling, and a mixed
siliciclastic-carbonate deposystem. Resulting falling-to-lowstand clinoforms downlap a
highly irregular surface of isolated carbonate bioherms built above a transgressive
surface that formed during the preceding
sea
level
rise. The northeastern Gulf of Mexico
is relatively stable, also with low wave energy, but dominated by siliciclastic
sedimentation. Falling-to-lowstand progradation of the Mobile River delta occurred in
numerous overlapping and spatially offset lobes incised by a complex channel network.
Clinoforms downlap an isotope stage 5 interglacial condensed section. The Mobile
depocenter migrated from east to west with eastern lobes showing evidence of wave
reworking while the western flank was fluvially dominated. Both the Mahakam and Mobile
deltas are composed of sand-rich clinoforms and channel deposits that possess excellent
potential reservoir properties.
ROBERTS, HARRY H., JOHAN SYDOW, JOHN ROBALIN, and RICHARD FILLON
AAPG Search and Discovery Article #90908©2000 GCAGS, Houston, Texas