27 Structural Geology and Tectonics I

Friday, 21 March 2008
8:00 AM - 12:00 PM

CORRELATION OF TRIASSIC AND JURASSIC TETONOSEQUENCES OF THE COLORADO PLATEAU AND THE NORTH AMERICAN APPARENT POLAR WANDER PATH

Paper number: 27-12
Program: Technical Sessions
Time: 11:40 AM – 12:00 PM

Authors

Abstract

The Triassic-Jurassic stratigraphy of the Colorado Plateau is subdivided by regional unconformities into seven tectonosequences, the Moenkopi, Holbrook, Chinle, Dinosaur Canyon, Glen Canyon, San Rafael and Brushy. Tectonosequence boundaries are characterized by abrupt changes indicative of inception of new sedimentary basins in which successive tectonosequences are deposited. Each successive basin is interpreted to have formed in response to a change in plate-tectonic setting. This interpretation is supported by a strong correlation between tectonosequences and segments of the Late Triassic to Late Jurassic North American low-latitude apparent polar wander path (NA APW). The Chinle tectonosequence was deposited during North American stillstand. The Dinosaur Canyon tectonosequence represents a brief interval of plate rearrangement involving a short duration westward excursion of North America. The Glen Canyon tectonosequence accumulated during the eastward return of North America from the J-1 to the J-2 cusp of the NA APW path. Middle Early Jurassic right-lateral translation and transtension were followed by cratonal-margin obduction and subduction-related magmatism. Initiation of the San Rafael tectonosequence coincides with initiation of the Mojave Sonora megashear and related left-lateral transtension and related magmatism. Deposition of the Brushy Basin tectonosequence coincided with renewed subduction-related magmatism and clockwise rotation of the Colorado Plateau.

Jurassic stratigraphy of the Colorado Plateau is cut by two major unconformities; the basal Glen Canyon sequence boundary and the basal San Rafael sequence boundary. The NA APW path is marked by two cusps, the J-1 and J-2. New data document the timing of the J-1 cusp within the hiatus of the basal Glen Canyon tectonosequence boundary. Although paleomagnetic data is lacking from a stratigraphic interval including much of the Glen Canyon and San Rafael tectonosequences, we predict future acquisition of paleomagnetic pole positions will document the J-2 cusp to lie within the hiatus of the basal San Rafael tectonosequence.

Tectonic events of the Cordilleran margin as evidenced by tectonosequence development and the NA APW path are reflected in magmatic and tectonic events of the Atlantic margin.