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Pavlis, T.L., 1982

Deformation along a late Mesozoic convergent margin: The Border Ranges fault system, southern Alaska

Bibliographic Reference

Pavlis, T.L., 1982, Deformation along a late Mesozoic convergent margin: The Border Ranges fault system, southern Alaska: University of Utah, Salt Lake City, Ph.D. dissertation, 177 p., illust., maps.

Abstract

In the western Chugach Mountains of southern Alaska the first-order distribution of crystalline rocks north of the Border Ranges fault is controlled by a complex system of faults that represent a macroscopic Border Ranges fault system. The fault system appears to represent a shattering of a pre-existing crystalline terrane during initiation (or re-establishment) of subduction and emplacement of the oldest tectonic unit of the subduction complex (McHugh Complex). Cross-cutting plutons together with regional fossil ages show that this event is pre-Albian and probably post-Valanginian in age. This Early Cretaceous age is roughly coeval with a major collisional event in central Alaska, and the Border Ranges fault may represent the shattered trailing edge of this collided block. The Cretaceous disruption conceals details of older events but a working model is discussed in which metamorphic rocks of the western Chugach Mountains are considered pieces of a pre-Jurassic subduction complex that formed the basement pieces of a pre-Jurassic subduction complex that formed the basement for an Early Jurassic arc system Peninsular terrane. Post-Early Cretaceous high-angle faults probably represent a regional transection of older structure during the Neogene rise of the Chugach Mountains. This young event is interpreted to represent the initiation of a forced convection cell in the prism.

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