LARGE FORAMINIFERA FROM LIMESTONE IN THE RAJAMANDALA FORMATION, SUKABUMI, WEST JAVA

Abstract

Rajamandala Formation is a limestone reef formation that is exposed in the Rajamandala – Sukabumi area, West Java. Different from those in the Rajamandala area, this formation which is located in the Sukabumi area is still rarely analyzed, especially from its large foraminifera. This study aims to assess the content, age, and depositional environment of reef limestone from the Rajamandala Formation based on large foraminifera. Research method was carried out in several stages. Sampling was done by spot sampling as many as 6 samples. Then, thin section observations was carried out using Olympus CX-22 binocular microscope. Finally, age and environmental analysis were carried out using basic biostratigraphic methods and cluster analysis based on the fossil content of large foraminifera. Result, the limestone reefs of Rajamandala Formation in Sukabumi area have varied material content. These rock ages were found to be in the Late Oligocene range (Chattian). This rock depositional environment is in shallow marine environment which is divided into 3 main clusters. The first cluster is dominated by Austrotrilina and Borelis which shows the Backreef shelf environment. The second cluster is dominated by Heterostegina and Cycloclypeus which shows the Forereef shelf environment. Finally, the third cluster is dominated by all large foraminifera representing the Reef environment. When compared with previous studies, the limestone of Rajamandala Formation in Sukabumi and Rajamandala areas has the same age and depositional environment.

Keywords

• content
• rajamandala formation
• large foraminifera
• reef
• sukabumi