GEOLOGICAL SOCIETY OF THE PHILIPPINES

SEISMIC STRATIGRAPHY AND STRUCTURAL ANALYSIS OF THE OFFSHORE MANIGUIN AREA, PHILIPPINES

 

Jovencio D. Esquito


        Seismic data from the offshore Maniguin area, Philippines was subjected to a seismic stratigraphic and structural analysis in order to find out the structural style, paleodepositional systems, and tectonostratigraphic evolution of the area.

        Structural mapping reveals an extensional structural frame consisting of two major half-grabens. Pre-existing fabrics influence the development of structural features that are oblique to the dominant E-W structural trend. Localized inversion related to a collision-related oblique-slip motion along the boundary fault was identified in the southern part of the study area. Seismic stratigraphic interpretation reveals an initial lacustrine depositional setting with some alluvial fan sedimentation that prevailed prior to collision. Then, a transitional phase marked by fluvio-deltaic to shallow marine conditions took place, and was followed by a marine depositional setting similar to today.

        The initial half-graben extensional setting influenced changes in the depositional environment and sedimentation patterns through time. Tilted block configurations controlled lateral and axial sediment transport systems during the early phase of the area’s evolution. Eventually, rifting ceased but sea-floor morphology, which is mainly controlled by the configuration of the tilted fault blocks, still influences the spatial distribution of subrecent to recent carbonate units.

 
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