Saller, Arthur H.1, Jesse Noah1, Rhys Schneider2, Alif Prama
(1) Unocal Corp, Sugar Land, TX
(2) Unocal Indonesia, Jakarta, Indonesia
(3) Unocal Indonesia, Balikpapan, Indonesia
ABSTRACT: A Sequence Stratigraphic Model for Late Cenozoic Deltaic Basins in Southeast Asia
The classic sequence stratigraphic model of Vail and colleagues is applicable in many basins; however, some key characteristics of that model are missing in late Cenozoic deltaic basins around Borneo (Kutei, Sandakan, northwest Borneo). Missing characteristics include onlapping lowstand systems tracts and thick transgressive systems tracts. In Borneo deltaic basins, depositional cycles on the shelf are dominated by thick progradational packages separated by thin shales and locally carbonates. Progradational packages accumulated during gradually falling eustatic sea level with the landward parts of progradations being deposited during high eustatic sea level and basinward parts deposited during low eustatic sea level. Previous models would divide the progradational packages into highstand, shelf-margin, falling-stage and sometimes lowstand systems tracts, but those systems tracts are difficult to separate because progradational intervals share common toplap and downlap surfaces.
Strata in slope and basin-floor environments are dominated by inclined parallel reflectors that extend from the most basinward clinoforms of progradational packages on the shelf. Slope channels and basin-floor fans cause local thickening and thinning. Strata in slope and basin-floor environments are separated into lowstand and condensed intervals. Lowstand sediments include sand and shale deposited in deep water when lowstand deltas prograded over underlying shelf edges. The stratal geometries in these deltaic basins were caused by: (1) rapid rises and slow falls eustatic sea level, (2) rapid subsidence (~300 m/my), and (3) abundant sediment supply. The best horizons for shelf to basin correlations are transgressive surfaces.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.