Multiple Phases of Tectonic Inversion, East Java Sea Basin Indonesia, and Potential Analogues in Pakistan

Abstract

 Inverted basins are structurally very complex as they generally preserve overprints of extensional and compressional tectonics. Intensity of inversion within any basin could vary from partial inversion to total inversion depending upon the tectonic environment, location and stratigraphy of the basin. Amount of inversion could be expected to vary within the fold belts from mild in the external parts to the severe total inversion in its interior.
East Java Sea Basin reveals an excellent example of multiple phases of tectonic inversion where multiple tectonic inversion episodes are well preserved in the tectono-stratigraphic record of the basin. Synthesis of data shows that the intricate tectonic history of the mentioned basin has experienced extension followed by compression (positive inversion-the change from subsidence to uplift), another phase of extension (negative inversion-change from uplift to subsidence) and presently is in compressional phase (positive inversion). These inversion structures are well resolved at seismic scale and can be identified as pre-rift, syn-rift and post rift (syn-inversion) mega-sequences. Timing as well as the degree of inversion varies within the basin from south to north.
Inversion related basins are commonly distributed around the globe and are petroliferous; however, within Pakistan still some reluctance exists in applying the term inversion despite the fact that the orogenic Sulaiman & Kirthar foldbelts and Badin extensional basins were initially part of passive margins of northward drifting In do – P ak is ta n Pl at e whi ch ha s subseque nt ly experienced compressional tectonics during Tertiary period. The overprint of extentional tectonics is preserved at places.
Analyzing the inversion tectonics of East Java Sea Basin, analogous structural configuration can be inferred in the western fold belt (Kirthar and Sulaiman foldbelt) Pakistan which will enhance our understanding of the geology of the region and its hydrocarbon prospectivity.