Mapping Rifted Margin Structure and Ocean-Continent Transition Location Using Crustal Thickness from Gravity Inversion for Asia-Pacific and the Indian Ocean

Alvey, Andy¹; Kusznir, Nick²; Roberts, Alan¹
¹Badley Geoscience Ltd, Hundelby, Spilsby, United Kingdom.
²Geology & Geophysics, Univeristy of Liverpool, Liverpool, United Kingdom.

The investigation and mapping of rifted continental margins and ocean basins is the focus of much current attention motivated by hydrocarbon exploration, territorial claims and geo-dynamic research. Satellite gravity anomaly inversion incorporating a lithosphere thermal gravity anomaly correction has been used to determine Moho depth, crustal thickness and continental lithosphere thinning for oceans and continental margins worldwide. These parameters are used to map rifted continental margin structure, ocean-continent transition location and the distribution of micro-continents within ocean basins. Using a gravity anomaly inversion method, which incorporates a lithosphere thermal gravity anomaly correction and a correction for the addition of volcanic crust during margin formation and breakup, we have produced a global suite of maps showing crustal thickness and oceanic lithosphere distribution for all of the world's oceans and adjacent margins. Here we focus on results from two geographic regions: Asia-Pacific and the Indian Ocean.

Maps of continental lithosphere thinning factor and crustal thickness from gravity inversion provide predictions of ocean-continent transition location and structure, independent of magnetic isochrons. Using these crustal thickness and continental lithosphere thinning factor maps with superimposed shaded-relief free-air gravity anomaly, we improve the determination of pre-breakup rifted margin conjugacy and sea-floor spreading trajectory. Crustal thickness & continental lithosphere thinning maps of the Indian Ocean restored to early post-breakup times show the geometry and segmentation of the rifted continental margins at the time of breakup together with the location of failed breakup basin and micro-continents. The abundance of anomalously thick crust within oceanic regions, interpreted as possible micro-continents and often associated with multi-phase volcanism, suggests that the development of the world's oceans and rifted continental margins has a more complex history than is shown by most large-scale plate reconstructions.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012