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Find Your Science at GSA
14 July 2009
GSA Release No. 09-35
Christa Stratton
Director of Education, Communication, & Outreach
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Collision Catalyzes Cordilleran Orogeny

Boulder, CO, USA - This new Special Paper from The Geological Society of America describes an iconoclastic model for the Cretaceous–Tertiary development of the Cordilleran orogen.

Most models for the development of the Cordilleran orogen invoke Late Jurassic–Cretaceous intraplate, back-arc shortening above an eastwardly-dipping subduction zone. Author Robert S. Hildebrand of Utah State University argues that a simple collisional model, in which the leading edge of North America was subducted to the west beneath a segmented, arc-bearing microcontinent, better fits the data.

Hildebrand theorizes that westerly dipping subduction beneath an exotic ribbon continent named Rubia was followed by development of an eastward-dipping subduction zone outboard of the collision zone. This model explains the origin of Laramide thick-skinned deformation, Cordilleran-type batholiths, early Tertiary metamorphic core complexes, Basin and Range extension, porphyry copper deposits, and the Pelona-Orocopia-Rand schists, and it helps resolve the longstanding Baja–British Columbia controversy.

Individual copies of the volume may be purchased through the Geological Society of America online store, or by contacting GSA Sales and Service, .

Book editors of earth science journals/publications may request a review copy by contacting Jeanette Hammann, .

Did Westward Subduction Cause Cretaceous–Tertiary Orogeny in the North American Cordillera?
Robert S. Hildebrand
Geological Society of America Special Paper 457
2009, 71 pages, US$40.00, GSA member price US$28.00
ISBN 978-0-8137-2457-7