Quantifying Structural Deformation History in the Central Indian Ocean

Abstract

The central Indian Ocean displays one of the most perplexing intra-plate deformations in an oceanic realm. Despite several studies attempting to explore this intriguing phenomenon, understanding about its structural style and spatiotemporal genesis is still debated. Earlier geophysical and deep-sea drilling studies proposed the late Miocene onset of extensive crustal deformation. Subsequent geophysical studies, however, speculated that parts of the deformation may have begun significantly earlier (c.a. 15.4–13.9 Ma) consequent upon contemporaneous dynamics of the India-Eurasia convergence. Alternative hypotheses argue about the crucial role played by temporal variations in the rotational motion of the India-Somalia-Capricorn plates. Here we examine new deep penetrating multi-channel seismic reflection data from the central Indian Ocean region to gather the style and extent of structural deformation in this region. We explore plausible mechanisms and estimate the onset of extensive intra-plate deformation. Based on seismic-stratigraphic interpretation and cumulative fault-throw analyses of new regional seismic profiles, our study confirms that extensive faulting occurred during the early Miocene period across the CIDZ. We document that an average of 40% of faults were activated around or before early Miocene time, showing maximum throw at a regional unconformity dating to 17–18 Ma. We also identify distinct categories of deformation manifested in these faults. While our findings endorse significantly prior to the late Miocene time of onset of deformation, new subsurface images offer much-improved constraints on prominent stratigraphic and structural variations.