Structural Inversion and Channel Evolution in a Transition Zone Across the Boundary Between Passive and Active Continental Margins: An Example From Offshore Southwestern Taiwan

Abstract

This study analyzes both 2D and 3D seismic images in the upper reach of the Penghu Submarine Canyon to investigate sedimentary and structural processes in the transition zone from passive to active margins. The study area lies across the deformation front which separates the rifted South China Sea (SCS) continental slope to the west from the submarine Taiwan accretionary wedge to the east. West of the deformation front, features indicating basin thickening and reverse offsets are observed on 2D seismic profiles, suggesting that pre-existing extensional faults may have been inverted to reverse faults during the arc-continent collision. From 3D seismic images, several structural and sedimentary features have been identified: in the rifted SCS slope domain, besides the paleo-slope surface, buried submarine channels and mass transport deposits (MTDs), the reactivated extensional fault system is mapped; while in the accretionary wedge, the fold and thrust structures are dominate. Since the deformation front is defined as the location of the most frontal contractional structures along a convergent plate boundary, we thus suggest to move the location of the previously mapped deformation front further west to where the inverted reverse fault lies. High resolution 2D seismic and bathymetry data reveal that the path of the paleo-submarine channels ran nearly perpendicular to the slope dip direction, while the present submarine channels head down slope in the study area. We suggest that this might be the result of the structural inversion. The interactions of down-slope processes and active structural controls affect the channel paths in our study area.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015