| 要約: | Thin-bedded turbidites are important hydrocarbon-bearing reservoirs in many mature
fields throughout the world. The type of turbidite depositional setting strongly influences
reservoir vertical and horizontal continuity. However, differentiation between lobe and
levee associated thin-bedded turbidites is still challenging because of the generally similar
facies characteristics. This study aims to solve this problem by conducting a detailed bedscale
facies and bed-type analysis on the Early Miocene Temburong Formation exposed
at Kampung Bebuloh, Labuan, Malaysia, which may uncover features that can help in
differentiating both depositional types. Six bed types are recognised in the Temburong
Formation, which are interpreted as low density turbidites (BT1 – 4), hybrid event beds
(BT 5), sustained turbidites (BT6) and possible densite muds (some BT3). Detailed facies
and ichnology analysis reveal features which are consistent with a lobe fringe deposit
rather than levee-associated environment interpretation, including tabular bed
geometries, presence of hybrid event beds, and the absence of thick-bedded channel-fill
sandstones. Five bed type associations are identified and interpreted as representing subenvironments
within an overall lobe depositional setting. A diverse trace fossil
assemblage, comprising the Nereites ichnofacies is consistent with a deep marine
environment. Further identification of the Paleodictyon and Nereites sub-ichnofacies
indicates a distal turbidite system setting, most likely lobe fringe. Based on the thick
accumulation of FA2 and FA3 and no distinct observable vertical trend, the Early
Miocene Temburong Formation in Labuan is interpreted as turbidites deposited at the
fringes of lobe complexes rather than a single lobe fringe. Earlier works into the
Temburong Formation in SW Labuan propose a middle slope to proximal basin floor setting where the thin-bedded intervals were interpreted as potentially representing either
levee deposits or the fringes of confined lobe deposits. Conversely, the Temburong
Formation at Kampung Bebuloh exhibits characteristics of an unconfined lobe setting,
suggesting an evolutionary change in depositional conditions over time.
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