Insights into the Origin of the East Barents Sea Mega Basin from 3d Geophysical Modelling

Laura Marello, Jörg Ebbing, and Laurent Gernigon
Geological Survay of Norway (NGU), Trondheim, Norway.

The Barents Sea has been affected by multiple tectonic processes including three orogenic phases (Timanian, Caledonian, Uralian) and several episodes of rifting, leading to a complex tectonic setting. Most prominently, this can be observed by differences between the rift basins configuration of the Western Barents Sea and the mega-scale basins of the Eastern Barents Sea. The mechanisms leading to the present day basin and crustal architecture are still not clearly understood, especially in the East Barents Sea area. For the formation of the around 20 km thick Eastern Barents Sea mega-basins different tectonic concepts have been proposed.

To better understand the basins and crustal architecture, we built a 3D potential field model of the great Barents Sea region which integrates pre-existing seismic information, petrophysical data, including densities and magnetic properties of the lithosphere. This model was developed to discuss different scenarios for the evolution of the Eastern Barents Sea basins, and how the different mechanisms would affect the crust properties and geometries.

Possible explanations for the origin and evolution of the East Barents Sea mega sag basin involve a foreland flexural sag system associated with the Uralian Orogeny (Ziegler, 1989) and/or late compressive motions on Novaya Zemlya (Otto and Bailey 1995). Alternative models include multiple phases of extension and related subsidence (Johansen et al. 1993, Otto and Bailey 1995, O’Leary et al. 2004) and/or phase-change processes in the lower crust (Artyushkov, 2005) as main cause for the anomalous subsidence.

We evaluate the different tectonic scenarios with 3D models involving; thinning of the crust, non homogeneous mantle and crust and the presence of a high-density layer in the lower crust. A first analysis shows that a single mechanism for the formation of such extraordinary deep basins is difficult to evoke.. A single rifting event forming such a large basin is in disagreement with the presence of inversion structures recorded in the seismic data, and with the recorded thickness of the crust (> 20 km). The large post-rift subsidence cannot easily be explained by a classic thermal subsidence mechanism, and a contribution in the subsidence history by density changes caused by phase transitions remains likely.

AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia