DETERMINATION OF TURBIDITE DEPOSITS FACIES BASED ON OUTCROPS AND PETROGRAPHIC DESCRIPTION OF CINAMBO - HALANG FORMATION, BOGOR ZONE, WEST JAVA

摘要

The Bantarujeg area is located in Majalengka District, West Java. This area is known for their submarine fan turbidite deposit that forms the widespread Cinambo Formation. The Cinambo Formation is Late Oligocene - Early Miocene in age. The Gunung Kromong Limestone Complex is deposited conformably above it. The Halang Formation is conformably deposited above the latter, subdivided into two formations, i.e. the Lower Halang Formation consisting of monomict breccia, claystone, tuff, and conglomerate, and the Upper Halang Formation consisting of tuffaceous sandstone, claystone, and conglomerate. This formation is Middle Miocene - Upper Miocene in age(Djuri, 1973).The turbidity current depositional mechanism in Majalengka is closely related to the morpho-tectonic settings during the early rifting of Bogor Basin (Martodjodjo, 2003). The Oligocene extentional regime and subsequent normal block faulting of Bogor Basin caused steep slope gradient from the neritic shelf margin marine in the north Java coast to upper bathyal marine along the axis of Bogor Basin. The Cinambo Formation and Halang Formation are representing two sequences of sedimentary structures related to sediment gravity flow. From the bottom to the top, the grain size is coarser eventually breccias, forming progradation of deep submarine fan (Walker, 1978). In detail, the internal characteristic of a turbidite shows more than just simple grading; a pattern of texture and sedimentary structures in this deposit was first noted by Arnold Bouma (1962) which is named after the inventor as the Bouma sequence.This paper intends to determine the facies characteristic and distribution geometry of theHalang Formation turbidite. It is based on field data observation and analysis to provide an overview of the field-outcrop perspective in relationship with reservoir and seal characteristics, rock distribution, and properties from proximal to distal turbidite facies area. This overview or idea can be applied in deepwater turbidite oil field, as we know thye are depending upon subsurface geophysical data, both seismic and well log.