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ABSTRACT: Depositional environment and sequence stratigraphy of Miocene high-frequency deltaic cycles exposed along the Jerudong Anticline, Brunei Darussalam

Back, Stefan1, C.K. Morley1, J. J Lambiase1, and M.D. Simmons2
(1) University Brunei Darussalam, Bandar Seri Begawan, Brunei 
(2) University of Aberdeen, Aberdeen, United Kingdom

Kilometer-scale prograding clinoforms associated with deltas are rarely seen in outcrop, however one such example is found in a Miocene sand-shale sequence exposed along the Jerudong anticline in Brunei Darussalam. Regional sequence stratigraphic interpretation shows that large clinoforms at the base of the Miocene Belait delta represent a succession of at least four high-frequency sand-shale sequences forming a highstand sequence set of a composite (3rd order?) sequence. The stratigraphically highest and best exposed high-frequency sequence exibits large slumps and sharp-based detached sand bodies at its base. Accumulation of these units most likely occurred during a high-frequency lowstand. An overlying 1 to 1.5-km-thick shale is interpreted to have developed during subsequent transgression. Rapid progradation of thick sand-dominated shoreface and tidal deposits characterizes the succeeding highstand systems tract. New sedimentological and micropaleontological data indicate that all deposits formed in a shoreface to shelfal setting. This differs from previous studies that interpreted a continental slope to deep-marine depositional environment.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia