Arctic Margin Ocean-Continent Transition Structure and Heat-flow Prediction from OCTek Gravity Inversion Mapping

Nick Kusznir

The determination of continent-ocean boundary (COB) location, ocean-continent transition (OCT) structure and magmatic type for the continent-ocean margins of Amerasia and Eurasia Basins, and the prediction of their heat-flow, presents a substantial scientific and technical challenge common to all frontier deep-water hydrocarbon exploration. The ocean basins of the Arctic formed during the Mesozoic and Cenozoic as a series of small distinct ocean basins leading to a complex distribution of oceanic crust, rifted continental margins, micro-continents and volcanic ridges. Using OCTek gravity anomaly inversion, we have produced the first comprehensive regional maps of Moho depth, crustal thickness, continental lithosphere thinning and oceanic lithosphere distribution for the Arctic. We use maps of crustal thickness and continental lithosphere thinning factor to constrain the location of the continent-ocean boundary and the distribution of oceanic lithosphere. Crustal cross-sections using Moho depth from the OCTek gravity inversion allow continent-ocean transition structure to be determined (e.g. narrow versus wide) and also provide constraints on their magmatic type (magma poor, “normal” or magma rich). Using gravity inversion mapping, we predict top basement heat-flow for the Amerasia and Eurasia Basins of the Arctic and their continental margins. Continental lithosphere thinning and post-breakup residual thicknesses of continental crust determined from gravity inversion have been used to predict the preservation of continental crustal radiogenic heat productivity and the transient lithosphere heat-flow contribution within thermally equilibrating rifted continental margin and oceanic lithosphere. The resulting crustal radiogenic productivity and lithosphere transient heat flow components, together with base lithosphere background heat-flow, are used to produce regional maps of present-day Arctic top-basement heat-flow. The sensitivity of present-day Arctic top basement heat-flow to initial continental radiogenic heat productivity, continental breakup age and oceanic lithosphere age has been examined. We determine crustal thickness, continental lithosphere thinning factors and ocean-continent transition location using a new gravity inversion method which incorporates a lithosphere thermal gravity anomaly correction (Greenhalgh & Kusznir 2007; Alvey et al. 2008; Chappell & Kusznir 2008). Public domain free-air gravity anomaly, bathymetry and sediment thickness data are used in the gravity inversion.

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