Steve Bachtel¹, R. Kissling², D. Martono³, S. Rahardjanto², P. Dunn¹, B. MacDonald²
(1) Exxon Production Research Co, Houston, TX
(2) Exxon Exploration Co, Houston, TX
(3) Pertamina, Jakarta, Indonesia

Abstract: Structural influence on carbonate platform architecture: Origin, growth, and demise of the Miocene-Pliocene Segitiga Platform, East Natuna Sea, Indonesia

Interpretation of newly acquired high-density 2D seismic data across the herein-named Segitiga Platform reveals a multi-phase growth history of initial isolation, coalescence, backstepping, and drowning. The Terumbu Formation is up to 1800 meters thick and comprised of strata deposited in platform interior, reef and shoal margin, and slope to basin environments. The platform originated in the early Middle Miocene as three small platforms localized on extensional fault-block highs separated by intraplatform seaways. The seaways were filled during Middle-Upper Miocene time by prograding shallow-water carbonates to form one megabank (1400 km²). A relative rise in sea level at the end of the Miocene caused a major backstep of carbonate margins and a reduction in platform size (600 km²). Rapid subsidence at the end of the Lower Pliocene terminally drowned the Segitiga Platform, prior to burial by Muda Formation shales.

Although eustasy is the primary control on sequence formation, tectonics strongly influenced the sequence architecture and facies distribution of the platform: 1) fault blocks provided a structural template for platform nucleation, 2) cessation of faulting may have instigated platform progradation and coalescence, 3) younger fault movement may have created highs for the localization of backstepping platforms, 4) local tectonic variations produced geographic variability of sequence architecture and facies distribution, 5) backstepping and terminal drowning of platforms coincided with increased regional subsidence associated with foreland basin development. Prevailing winds and oceanographic currents also influenced platform architecture.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana