Characterization of Miocene-Pliocene carbonate platforms, southern Southwest Palawan Basin, Philippines

Abstract

Isolated carbonate platforms and buildups of the Likas Formation provide a long record of carbonate sedimentation in the southern end of the Southwest Palawan Basin. While most carbonate platforms terminated in early Miocene and middle Miocene time in northern parts of western offshore Palawan (i.e. Northwest Palawan Basin and central South Palawan), carbonate deposition began later in the south during late middle Miocene time. Carbonate platforms of the Likas Formation developed in the Paragua sub-basin, which is interpreted to be a depozone eastward of the Palawan accretionary wedge in the structurally complex Southwest Palawan Basin. A regional 2D seismic grid and borehole data from four wells were used to analyze the growth patterns of the carbonate platforms, identify seismic facies, and reconstruct the evolution of the platforms. The carbonate platforms developed on the folded and faulted middle to premiddle Miocene siliciclastic strata. These older siliciclastic units were thrusted onto the southern end of the North Palawan microcontinental fragment, which represents a block of continental crust that drifted southward from South China during early Tertiary time. The platforms aggraded over time and backstepped to keep pace with increasing rates of relative sea level rise. Karst features are recognizable on seismic sections and indicate that the platforms were subaerially exposed at various times during their development. The platforms exhibit variable morphology from faulting and tilting. The platforms terminated in early Pliocene time, as relative sea level continued to rise, and were buried by deep-marine siliciclastic units.