Sequence Stratigraphy of Miocene-Pliocene Deltaic Shelf Margin Sequences in a Tectonically Active Basin, Brunei, Southeast Asia

Paul Crevello, Philip Rowell, Komut Maneechai, Fook Meng Foo, Le Nhat Vinh, and Kwong Wee Poh

Stratigraphy of Miocene-Pliocene deltaic shelf margin sequences are displayed from selected subsurface and outcrop locations in Brunei and adjacent areas. Subsurface seismic data are used to illustrate the association between basin dynamics and stratal geometries of large-scale stratigraphic packages, while well log and outcrop data are used to resolve sediment partitioning of higher frequency packages.

Deltaic shelf margin sequences dominate the stratigraphic architecture of the Brunei shelf. These depositional systems are 'regionally' correlative and often are 'transgressed' by marine shales. Variations in shelf margin sequence types include: (1) aggradationally stacked sequences associated with steep shelf margins that developed adjacent to counter-regional faults, while (2) low-relief progradational sequences that show lateral migration during times of local tectonic stability. Highly aggradational margins are predicted to contain vertically stacked and linked depositional systems with limited sediment partitioning; low stand systems tracts are not evident.

Sequences in the aggradational margins are only evident by interpreted transgressive events. Locally, incised valleys punctuate aggradational topset strata. Low-relief progradational margins may contain more highly partitioned stratigraphy and conform to sequence correlations (sensu stricto). Sediment supply and eustatic sea level fluctuations are interpreted to have more influence on these margins.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California