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Laptev Sea – amount and style of continental rifting based on gravity modelling

Author(s): Stan Mazur Getech, Kitson House, Elmete Hall, Elmete Lane, Leeds LS8 2LJ, United Kingdom
School of Earth & Environment, University of Leeds, Leeds LS2 9JT, United Kingdom
S. Campbell Getech, Kitson House, Elmete Hall, Elmete Lane, Leeds LS8 2LJ, United Kingdom
C. Green Getech, Kitson House, Elmete Hall, Elmete Lane, Leeds LS8 2LJ, United Kingdom
R. Bouatmani Getech, Kitson House, Elmete Hall, Elmete Lane, Leeds LS8 2LJ, United Kingdom

An outstanding question concerning continental rifting is the relative contributions of extensional plate boundary forces on the plate and thermal effects, such as from a mantle plume. Magma-rich continental margins and rifts generally represent some combination of these two effects, with large and complex thermal anomalies further complicating the situation. The magma-poor Laptev Sea continental rifts, however, provide an excellent opportunity to study the contribution of rifting dominated by extensional forces.

The Laptev Shelf offshore eastern Siberia represents an interesting tectonic setting, where an active oceanic spreading centre, the Gakkel Ridge, approaches the continental margin. The North America – Eurasia plate boundary, corresponding to the Gakkel spreading axis, continues farther south, passing into the continental area. From the latest Cretaceous to the Pliocene, a continental rift system developed in that area comprising several deep subsiding grabens and high-standing basement blocks identified on seismic sections.

We used 2D gravity modelling and 3D gravity inversion, constrained by published seismic reflection profiles, to assess the amount of crustal stretching across the North America – Eurasia plate boundary in the Laptev Shelf and to understand extension partitioning within the continental crust. Performing our extension calculations separately for top pre-rift sediments and top crystalline crust, we were able to discriminate the effects of the Cenozoic North America-Eurasia interaction from the pre-existing extension that also contributed to the finite crustal thinning.

The joint interpretation of Moho and basement depths from gravity inversion and public domain seismic data suggests that this part of the Siberian margin was already significantly stretched, in a fairly uniform manner, by the Late Cretaceous. The latest Cretaceous–Cenozoic extension in that area was partitioned between two rift zones, the Laptev Rift System and the New Siberian Rift. The models reveal a rapidly increasing extension towards the shelf edge in the Laptev Rift System explained by its connection to the active spreading axis of the Eurasia Basin - the Gakkel Ridge. In contrast, the New Siberian Rift terminates at the continent-ocean boundary and is characterised by a uniform stretching along strike. The Laptev Rift System represents a mature continental rift zone, the architecture of which provides new insight into the development of magma-poor passive margins. Our study suggests that an estimate of ~500 km of total extension is sufficient to entirely eliminate crystalline continental crust. The continental mantle is already exhumed at the base of the late Mesozoic sediments before the break-up of lower lithosphere and the upwelling of the asthenospheric mantle. This situation appears to be a prerequisite for the exhumation of continental mantle after initiation of spreading. The example of the Laptev Rift System shows that extension driven by divergent movement of continental plates is a sufficient factor to produce almost complete continental break-up without substantial heat input from upwelling asthenospheric mantle.


Title:
Laptev Sea – amount and style of continental rifting based on gravity modelling
Type:
Oral
Origin:
Mixed
Day:
2
Session:
1
Daily sequence no.:
11
Lead author last name:
Mazur
Lead author first name:
Stan
Affiliation(s):
Getech, Kitson House, Elmete Hall, Elmete Lane, Leeds LS8 2LJ, UK/School of Earth & Environment, University of Leeds, Leeds LS2 9JT, UK
Country:
United Kingdom
Abstract status:
ok
UID:
57