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The AAPG/Datapages Combined Publications Database

AAPG Special Volumes


Pub. Id: A155 (1986)

First Page: 669

Last Page: 685

Book Title: M 41: Paleotectonics and Sedimentation in the Rocky Mountain Region, United States

Article/Chapter: Laramide Paleotectonics of Southern New Mexico: Part IV. Southern Rocky Mountains

Subject Group: Structure, Tectonics, Paleostructure

Spec. Pub. Type: Memoir

Pub. Year: 1986

Author(s): W. R. Seager, G. H. Mack


The chief mode of Laramide deformation of the foreland area of south-central and adjacent parts of southwestern New Mexico was uplift of relatively simple basement blocks and subsidence of complementary basins that were similar in style to but smaller in size than some of those of the central Rocky Mountains. Uplifts trend generally northwestward to west-northwestward and are asymmetric with southwest-dipping, thrust- or reverse-faulted northeastern margins. Broad, less deformed southwestern flanks plunge into complementary basins filled with lower Tertiary clastic rocks about 600-2100 m (2000-6800 ft) thick. In south-central New Mexico the reconstructed uplifts and basins resemble Wind River-type uplifts and basins; they display evidence of strong horizontal compression nd significant crustal shortening.

The general style of deformation extends into the northern margin of terrane previously regarded as part of the Cordilleran "overthrust" belt. In this region, however, strike-slip as well as reverse movement distinguishes uplift marginal fault zones. Thus, uplifts in this region may be a product partly of convergent wrenching and partly of northeast-southwest compression, and adjacent basins may be a mix of Wind River (compressional) and Echo Park (transpressional) types. Thrust faulting adjacent to steep, uplift marginal faults may also be viewed as a consequence of convergent wrenching rather than regional overthrusting.

Breakup of the southern New Mexico craton into thrust-bounded blocks may be a result of the attempt by the North American craton, driving actively southwestward, to underthrust a resisting magmatic arc. Strike-slip on faults in southwestern New Mexico may be a result of oblique subduction of the Farallon plate or a product or reactivation of suitably oriented pre-Laramide faults.

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