Stratigraphic Architecture and Fundamental Sedimentology of Two Late Pleistocene Deltas: Gulf of Mexico and Indonesia
Harry H. Roberts, Sydow John, Fillon Richard, Kohl Barry, 2002. "Stratigraphic Architecture and Fundamental Sedimentology of Two Late Pleistocene Deltas: Gulf of Mexico and Indonesia", Sequence Stratigraphic Models for Exploration and Production: Evolving Methodology, Emerging Models and Application Histories, John M. Armentrout, Norman C. Rosen
Download citation file:
The Mobile River shelf-edge delta, built on the outer Mississippi-Alabama shelf, prograded to the shelf-slope break as sea level approached the latest Pleistocene glacial maximum. At the same time, the Mahakam River built a complex shelf-edge delta on the eastern shelf of Borneo (Indonesia). Both late Pleistocene deltas were constructed during falling-to-lowstand relative sea-level conditions. The former was fed by the temperate Mobile River, the latter by the equatorial Mahakam River. Four coreholes provided detailed calibration of high resolution seismic data for stratigraphic control within the Mobile River delta while one long corehole and numerous piston and vibracores provided similar seismic calibration for stratigraphic control in the Mahakam delta. Systems tracts and key bounding surfaces were related to global eustacy in both settings over ca. 125 ka.
Sequence architectures differ significantly, an important consequence of different depositional settings. 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’s Lagniappe delta has occurred in numerous overlapping and spatially offset lobes incised by a complex channel network. Clinoforms downlap the outer shelf shale directly overlying an isotope stage 5 interglacial condensed section. By contrast, the tropical Mahakam shelf is tectonically active, has low wave energy, strong oceanic currents, upwelling, and a mixed siliciclastic–carbonate depositional system. Falling-to-lowstand clinoforms of this delta downlap a highly irregular surface of isolated and fused carbonate bioherms built above a transgressive surface that formed during the preceding sea level rise. Both the Mahakam and Mobile River depocenters are multilobate and clearly built by autocyclic switching of depositional sites. The eastern lobes of the Mobile River delta show evidence of wave reworking while the western flank is fluvially dominated. Both the Mahakam and Mobile deltas are composed of sand-rich clinoforms and channel deposits that possess excellent reservoir properties.