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Laptev and East Siberian Arctic Crustal Thickness and Oceanic Lithosphere Distribution from Gravity Inversion

Kusznir, Nick J.*1; Alvey, Andy 2
(1) Earth Interior Dynamics, University of Liverpool, Liverpool, United Kingdom.
(2) Badley Geoscience, Hundleby, United Kingdom.

We have produced regional maps of crustal thickness and oceanic lithosphere distribution for the greater Arctic region including the Laptev, Chukchi and East Siberian 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, in the Podvodnikov basin, 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, of between 10-15 km thickness and covered by thick Cenozoic sediments, is interpreted as highly thinned rifted continental crust formed as the eastward continuation of Gakkel Ridge sea-floor spreading in the Eurasia Basin. The present axis of Laptev 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 greater rifting in the southern Laptev Sea. The presence of very thin continental or oceanic crust of thickness 5 km 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 #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California