Mapping & Reconstructing Rifted Margin Crustal Thickness, Ocean-Continent Transition and Micro-Continents Using Satellite Gravity Inversion: A Tool for Deepwater Exploration

Alvey, Andy ¹; Kusznir, Nick J.²; Roberts, Alan M.¹
(1)Badley Geoscience Ltd, Hundelby, Spilsby, United Kingdom. (2) Department of Earth & Ocean Sciences, University of Liverpool, Liverpool, United Kingdom.

The investigation and mapping of rifted continental margins and ocean basin development 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 locate the ocean-continent transition and the distribution of micro-continent along rifted continental margins and adjacent ocean basins.

Using a new gravity anomaly inversion method, which incorporates a lithosphere thermal gravity anomaly correction, we have produced the first comprehensive 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 three geographic regions: Asia-Pacific, the South & Central Atlantic and the Indian Ocean.

Maps of continental lithosphere thinning factor and crustal thickness from gravity inversion provide predictions of ocean-continent transition location independent of magnetic isochrons (that are often difficult to interpret). Superposition of shaded-relief free-air gravity onto crustal thickness maps from gravity inversion provides improved determination of pre-breakup rifted margin conjugacy and sea-floor spreading trajectory. Crustal thickness & continental lithosphere thinning maps from gravity inversion restored to early post-breakup times show the geometry and segmentation of the margin 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 has a more complex history than is shown by most large-scale plate reconstructions.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.