Abstract

The modern continental slope offshore Brunei provides an analog for the relationship between syndepositional structure, slope accommodation space, and sediment dispersal systems. The bathymetric profile is best described as a "stepped slope" resulting from progressive basinward thrusting, driven by regional tectonism and up-dip deltaic sediment loading. It is characterized by elongate, structurally controlled mini-basins 2-10 km in width and 20-60 km in length. Sediment dispersal pathways can extend for >60km and are quite tortuous across the irregular bathymetric relief. The regional depositional system across this slope consists of a complex array of depositional elements. Sequence stratigraphic terms such as lowstand systems tract, slope fan, or basin floor fan are too generic to adequately describe this slope/basin depositional system. It is more effective to define the system by documentation of its component depositional elements. There are four primary elements that characterize this system. 1) Sediment dispersal fairways that range from 2-5 km in width characterized by multiple straight (erosional/bypass) channels or sinuous (depositional/leveed) channels. 2) Distributary channel/lobe complexes consisting of sheet deposits punctuated by low relief channels. 3) Mass wasting features ranging in scale from local cohesive slump complexes up to regional debris field/mass transport complexes. Cohesive slumps reflect short distance transport by down slope creep and mass transport complexes reflect long distance cohesive and debris flow events. 4) Submarine canyons developed by gravity mass wasting along the forelimbs of thrust-cored structures. Long distance sediment dispersal follows complex flow paths across this slope system that link adjacent mini-basins and associated depositional elements.