Siberian Arctic Seas Crustal Thickness and Oceanic Lithosphere Distribution from Gravity Inversion

Nick J. Kusznir¹ and Andy Alvey^2
1Earth Interior Dynamics, Liverpool University, Liverpool, United Kingdom.
²Badley Geoscience, Hundleby, United Kingdom.

We have produced comprehensive maps of crustal thickness and oceanic lithosphere distribution for the greater Arctic region including the Laptev, East Siberian and Chukchi Seas using gravity anomaly inversion. Crustal thickness, continental lithosphere thinning factors and ocean-continent transition location for the Amerasia and Eurasia Basins and their adjacent continental shelves have been determined using a new gravity inversion method which incorporates a lithosphere thermal gravity anomaly correction. Data used in the gravity inversion is public domain gravity, bathymetry and sediment thickness data. Our gravity inversion predicts thin crust and high continental lithosphere thinning factors in the Eurasia, Canada, Makarov and Podvodnikov Basins consistent with these basins being oceanic or highly thinned continental crust. Gravity inversion also predicts thin crust in the Laptev Sea and North Chukchi Basins. The thin crust under the Laptev Sea, covered by thick Cenozoic sediments, is interpreted as oceanic crust representing an eastward continuation of Gakkel Ridge sea-floor spreading in the Eurasia Basin The present axis of Laptev sea-floor spreading (or rifting), as indicated by a clear lineation of earthquake epicentres, is located in the northern Laptev Sea adjacent to the De Long Massif, and follows earlier sea-floor spreading in the southern Laptev Sea. The presence of very thin continental or oceanic crust under the North Chukchi Basin has major implications for understanding the Mesozoic and Cenozoic plate tectonic history of the Siberian and Chukchi Amerasia Basin margins, and the evolution of Chukchi Cap and Northwind Ridge. Thinner crust is also predicted in the region of the East Siberian Sea Basin and is separated from the Podvodnikov Basin by thick crust under the De Long Massif. Moho depths predicted by gravity inversion calibrate well with seismic refraction estimates from the TransArctica-Arctica profiles across the Eurasia, Podvodnikov and Makarov Basins, and the Lomonosov Ridge.

 

AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.

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