--> Abstract: The Kinematic Evolution of the West Spitsbergen Fold-and-Thrust Belt: Insights from Analogue Modelling, by K. A. Leever, R. H. Gabrielsen, J. I. Faleide, D. Sokoutis, and E. Willingshofer; #90096 (2009)

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The Kinematic Evolution of the West Spitsbergen Fold-and-Thrust Belt: Insights from Analogue Modelling

Karen A. Leever1, Roy H. Gabrielsen1, Jan Inge Faleide1, Dimitros Sokoutis2, and Ernst Willingshofer2
1Department of Geosciences, University of Oslo, Oslo, Norway.
2Tectonics Department, VU University Amsterdam, Amsterdam, Netherlands.

The Paleocene-Eocene West Spitsbergen Fold-and-Thrust Belt (WSFB) defines a segment of the NW margin of the Barents Sea, the former transform plate boundary between Eurasia and Greenland. The western part of the WSFB is characterized by thick-skinned deformation with steep basement-involved faults while the eastern area constitutes a classical, foreland-directed thin-skinned fold-and-thrust belt, with shortening directions generally orthogonal to the plate boundary. Detailed kinematic studies of the WSFB reveal a complex pattern of transpressional, transtensional and convergent events.

The WSFB has been regarded as a classical example of transpression and associated strain partitioning, accommodating more than 300 km of along-strike displacement during its development. To explore the validity of this model and to investigate the strain partitioning mechanism and its consequences when strain distribution is concerned, scaled analogue tectonic modelling has been performed. A homogeneous sand pack or a sequence consisting of sand with a thin intercalated layer of silicon putty overlies a basal velocity discontinuity across which the convergence angle was varied from 3.75 to 30 degrees. Incremental displacement fields calculated by digital Particle Image Velocimetry (dPIV) were used to constrain fault kinematics, facilitating the analysis of the experiments.

We observe a progressive kinematic evolution in which (1) an initial stage characterized by the formation of Riedel shears and linkage of these shears to define lozenge-shaped units, is followed by (2) a stage of strain partitioning where strike-slip along a central shear zone (Y-shear) is coeval with orthogonal contraction and the development of reverse faults and thrust faults originating at the basal discontinuity. Finally, (3) in a strain weakening stage the strain becomes concentrated along the central shear zone. With sufficient deformation, the system switches back to the strain partitioning stage (2).

In cross section an asymmetrical positive flower structure is observed in the central part of the deformation zone, while low-angle faults branch to the foreland-side of the fold-and-thrust belt. The considerable along-strike geometrical diversity that characterizes the structure is consistent with that seen in the WSFB. Altogether, the present experiments support the hypothesis that strain partitioning in low angle convergence may have played an important role in the development of the WSFB.


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