Using Crustal Thickness & Continental Lithosphere Thinning Factors from Gravity Inversion to Constrain Plate Reconstructions for the Arctic & Northeast Atlantic

Andy Alvey

The investigation and mapping of rifted continental margins and adjacent ocean basins is the focus of much current attention, motivated by hydrocarbon exploration, territorial claims and geodynamic research. 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. The results of this exercise are used to map rifted continental-margin structure, location of the continent-ocean boundary (COB) and the distribution of micro-continents within ocean basins. By using this gravity-inversion method, which also incorporates a correction for the addition of new volcanic crust during margin formation and breakup, we have produced a global suite of maps which shows crustal thickness and oceanic lithosphere distribution for all of the world's oceans and adjacent margins. Here we focus on results from the Arctic & Northeast Atlantic. Maps of continental lithosphere thinning factor and crustal thickness from gravity inversion provide predictions of the ocean-continent transition structure and COB location, independent of magnetic isochrons. Using these maps, with shaded-relief free-air gravity-anomaly superimposed, we have improved the understanding of pre-breakup rifted margin conjugacy and sea-floor spreading trajectory within the Arctic basins. By restoring crustal thickness & continental lithosphere thinning maps of the Eurasia Basin & NE Atlantic to their initial post-breakup configuration we can show the geometry and segmentation of the rifted continental margins at their time of breakup, together with the location of highly-stretched failed breakup basins and rifted micro-continents. In this talk we focus on the Tertiary development of connectivity between the Eurasia basin & the NE Atlantic. We interpret gravity inversion crustal thicknesses underneath Morris Jessop Rise & Yermak Plateau as continental crust which provided a barrier to the tectonic and palaeo-oceanic linkage between the Arctic & North Atlantic until ~ 33Ma, at which time the two ‘micro-continents’ become separated. Before this time, we link the seafloor spreading within the Eurasia Basin to that in Baffin Bay, rather than transfer south into the NE Atlantic.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013