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C. J. Northrup1, Walter S. Snyder1
(1) Boise State University, Boise, ID

Abstract: Transpressional and transtensional tectonics of the southern Ural Orogen

The Ural Orogen exhibits a number of unusual characteristics, including: (1) limited shortening in the foreland fold-thrust belt; (2) deepening of the foreland basin away from the mountain belt; (3) narrow overall width; and (4) lack of a significant syn- to post-tectonic metamorphic core along the axis of the orogen. These characteristics are consistent with highly oblique convergence during Uralian Orogenesis, making orogen-orthogonal contraction less important than orogen-parallel transport. Deformation produced by post-collisional convergence may have been partitioned, with the contractional component taken up in the fold-thrust belt, and the orogen-parallel component accommodated by strike-slip movement on major fault zones along the axis of the mountain belt. The character and distribution of deformation along the western margin of the southern Urals is strongly suggestive of sinistral oblique convergence. The southern part of mountain belt forms a westward-convex orocline flanked to the north by the Bashkirian Anticlinorium, and to the south by a rhomb-shaped basin delineated by isopachs of Permo-Carboniferous sediments (the Aqtöbe sub-basin). Together, the anticlinorium and basin resemble a pair of dynamically linked elements produced by transpression and transtension, respectively, during overall sinistral oblique convergence across the Ural Orogen. The Carboniferous-Permian tectonic evolution of the southern Urals is connected to that of the PreCaspian, and local transpressional and transtensional tectonics may have played a critical role in controlling the distribution, geometry, and evolution of basins within this system.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana