ABSTRACT: The Rajamandala Limestone at Sukabumi; Can it be considered a field analogue for the Batu Raja Limestone?

Carnell, Andrew , Robertson Research International, N. Wales, United Kingdom

The late Oligocene Rajamandala Limestone of West Java outcrops as topographic highs between Cibadak, in the West, and Bandung, in the east. Despite proximity to the major population centres of Jakarta and Bandung and extensive quarry exposures these limestones, which are often regarded as analogues for the highly productive Batu Raja Limestone (South Sumatra, Sunda and Offshore North West Java Basins), remain little studied and poorly understood. At Batu Asih (near Cibadak) a series of outcrops on a scale equivalent to that seen in conventional cores was examined to better understand the complex facies interrelationships of limestone depostional systems.

Field descriptions accompanied by petrographic and biostratigraphic analyses allowed for identification of depositional facies as follows: Reef facies, Lagoonal facies, Fore-reef debris facies, Foraminiferal/Algal shelf facies, Open marine facies, Eulepidina facies, and Beach facies.

By integrating field observations and analytical data, deposition is interpreted to have occurred as a series of small coral islands surrounded by foraminiferal/algal dominated shelf sediments. The outcrops also allow for a better understanding of the impact and distribution of diagenetic phases and faulting, and impact of exposure.

The Rajamandala Formation is often regarded as an analogue for the Batu Raja limestone, although biostratigraphic analyses indicate that they are not direct age equivalents. Despite the age difference similar depositional processes influenced both formations and consequently similar facies are apparent, although corals are more prevalent in the Rajamandala Formation. The Rajamandala formation is not a direct field analogue for the Batu Raja limestone, although outcrops in the Sukabumi area do allow for a three-dimensional study of carbonates and so enable an appreciation of depositional and post-depostional processes and geometries.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia