Proceedings, Indonesian Petroleum Association
Thirty-Third Annual Convention & Exhibition, May 2009
Architectural Elements of a Longitudinal Turbidite System: The Upper Miocene Halang Formation Submarine-fan System in the Bogor Trough, West Jawa
M. Ma’ruf Mukti*, Makoto Ito*, Cipi Armandita**
The lower part of the Upper Miocene Halang Formation in the south of Kuningan, West Java is re-interpreted to have developed as a longitudinal turbidite system downsloping in the east along the axis of Bogor Trough. The Halang Formation turbidite system is represented by high-sinuosity channels in association with crevasse- and frontalsplays, and is interpreted to have developed as a mud-dominated submarine-fan system. Detailed field mapping of the deposits and observation of centimeter-scale lithofacies features were identified on the basis of five major lithofacies associations: (1) channel deposits; (2) overbank deposits; (3) sheet sandstones; (4) basin-plain deposits (5) sediment-wave deposits. Hemipelagite-dominated intervals were used as datums for clarifying spatial and temporal variations in the five major lithofacies associations. In general, channel deposits documents high-sinuosity channel patterns and locally contain lateral accretion surfaces. Sinuosity of submarine-fan channels decreases upsection along with the increase of sandstone to mudstone ratio, and this temporal variation in geometry of channels appears to have responded to the increase in the supply of coarse-grained particles into the basin. Sheet sandstones are interpreted to represent both frontal-splay and crevasse-splay deposits in relation to channel mouth and proximal overbank deposits in upslope areas, respectively. Sedimentwave deposits are identified in overbank deposits. The generally eastward-directed paleocurrents are dominant, and interpreted to reflect the existence of paleohigh in the western margin of Bogor Trough that appears to have been one of the major hinterlands for the lower Halang Formation. Furthermore, the increase in the sandstone-tomudstone ratio upsection may have responded to the activation of this hinterland. The present sedimentological study can provide a framework for new avenue of petroleum geology in the border of West-Central Java.