--> Abstract: Interaction Between Hyperpycnal Flow-Derived Turbidites and Debrites from Submarine Slopes; from Outcrop Example from the Temburong Fm, Labuan, NW Borneo, by Christopher A. Jackson; #90078 (2008)

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Interaction Between Hyperpycnal Flow-Derived Turbidites and Debrites from Submarine Slopes; from Outcrop Example from the Temburong Fm, Labuan, NW Borneo

Christopher A. Jackson
Earth Science and Engineering, Imperial College, London, United Kingdom

The Temburong Fm (Late Oligocene-Early Miocene), NW Borneo, provides one of the only opportunities to study a succession which contains units genetically (if not age) equivalent to turbidite-hosted reservoirs located on the NW Borneo margin. Based on detailed sedimentological analysis two gravity-flow facies are identified; (i) ungraded, silty mudstone, 20-60 m thick, rich in large (>5 m), moderately deformed lithic clasts; and (ii) organic-rich, sharp-based, medium-grained sandstone, which are 0.4-2 m thick and dominated by planar-parallel lamination (Tb) alternating with minor massive (Ta), climbing-current and current-ripple laminated (Tc) intervals. Channelised sandstone beds also contain laterally discontinuous, cobble-mantled scours. Based on these characteristics, the clast-rich silty mudstones are interpreted as slump-derived, debris-flow deposits (debrites) derived from the unstable upper slope and the organic-rich sandstones are interpreted as hyperpycnal turbidites derived directly from river effluent, probably associated with a coeval shelf-edge delta. Analysis of the large-scale stratal architecture of the two facies indicates that the turbidites where locally ponded within topography developed at the top of the debrites and are locally eroded-out at the base of overlying debrites. This study has implications for the identification of hyperpycnal flow-derived turbidites in ancient sedimentary successions and the style of interaction between cohesive (turbidites) and non-cohesive (debrites) gravity-flows on submarine slopes. From an applied perspective, this study also has implication for the style of sediment delivery to the NW Borneo margin, an area where hyperpycnal flow-derived turbidites have not previously been documented. Furthermore, this study also highlights the potential reservoir geometry of sand-rich turbidites encased in mud-rich debrites.

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas