Evolution of Miocene Pre-Mahakam Delta, East Kalimantan, Indonesia
Charles J. Stuart, Richard A. Leveque, R. Abdoerrias, Hal
L. Heitman, Achmad Nurhono, Hans F. Schwing, Benny Sidik, and Suta Vijaya
Sequence stratigraphy played a prominent role in two Unocal regional studies of late Paleogene and Neogene strata in the eastern (offshore) Kutei basin, East Kalimantan, Indonesia. A chronostratigraphic framework was applied to regional correlation, facies analysis, organic geochemistry, and 2-D basin modeling. Sedimentation at the southern basin margin was significantly affected by the stable Paternoster platform and reactivation of faults associated with the Paleogene Adang fault zone. Three major delta systems are recognized, in addition to late middle Miocene Mahakam deltaics: the early Miocene Maruat system, and middle Miocene Yakin and Sepinggan systems. The depocenters of these delta systems appear to have shifted progressively to the east- northeast where they bec me fixed in the late middle Miocene (Mahakam delta). Maruat deltaic sedimentation ended abruptly at the Maruat Limestone, which was deposited during a widespread, possibly global-eustatic, flooding event. Variations in limestone thickness may be due to irregular paleobathymetry caused by early movement of normal faults within the reactivated Adang zone. Normal fault movement accelerated during deposition of overlying Yakin Formation deltaics. The Yakin thickens abruptly across faults in the Adang fault zone demonstrating syndepositional fault movements. Yakin deltaics are sharply overlain by a thick, aggradational succession of coaly deltaic sediments that comprise the Sepinggan Deltaics. These strata grade upward into distal deltaics and reefal(?) limestones that are the southerly equiv lents to the Mahakam delta system.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California