OLIGOCENE-MIOCENE CARBONATE MOUNDS IN THE CENTRAL AND EAST JAVA BASINS, INDONESIA

Carbonate mounds are very abundant in the Oligo-Miocene of Central and East Java Basins, Indonesia. The stratigraphic intervals consist mainly on carbonate mound and off-mound facies. This study integrates subsurface and surface data, using 2D seismic lines, well logs, outcrop and petrographic analyses, and Sr isotopes data.

Seismic mapping shows multiple stages in growth of mounds. The seismic profiles indicate mounded, parallel, chaotic, and progradational facies, some time discontinuously. Laterally seismic reflectors show onlap character. Outcrop analog presents the same feature identified in seismic images. From petrographic point of view, seismic mounded facies are represented by grainstone, packstone, and boundstone petrotypes, parallel facies mainly by mudstone, and off-mound faceis are represented by mudstone and wackestone petrotypes. The carbonate mounds present sharp margin and pass laterally into off-mound facies. The mounds generally are faulted postdepositional. The mounds are stacked or isolated, and they differ in size. The large mounds show a preference to center over high basement areas. Vertical and horizontal mound distribution patterns throughout the area suggest a complex evolution with distinctive stages: initiation, accretion, backstepping, and drowning during Ruppelian - Aquitanian time.