A Model for Evolution of Laramide Axial Basins in the Southern Rocky Mountains, U.S.A.

Abstract

The structural, stratigraphic, and sedimentologic development of Laramide axial basins of the southern Rocky Mountains is inconsistent with previous models relating them to transpressional tectonics. Axial basins are better explained as broad synclinal troughs in the hanging walls of large pop-up structures, in contrast to perimeter and ponded basins formed in the footwalls of these same structures. Laramide faults in the southern Rocky Mountains can be divided into the E-dipping Park Range thrust system and the W-dipping Sangre de Cristo thrust system. The W-dipping Front Range fault is the backthrust of the Park Range system, and the E-dipping Nacimiento fault is the back-thrust of the Sangre de Cristo system. The broad synclinal troughs formed between these two pairs of oppositely verging thrust systems were the locations for sediment deposition in axial basins, as exemplified by the Galisteo-El Rito basin of northern New Mexico. The Eocene Galisteo and El Rito formations were deposited on a broad syncline of Phanerozoic strata with crystalline basement along the basin margins. Most sediment was derived from the northeast, north, and northwest, except near the NE-trending TijerasCañoncito transfer zone along the southeast margin of the basin. Uplift of the Sangre de Cristo Range occurred first, followed by backthrusting to uplift the Sierra Nacimiento. This model explains Laramide uplifts and basins as the direct response to rapid NE-SW convergence between the North American and Farallon plates, without multiple reorientation of Laramide stress fields, and without major strike-slip along the eastern side of the Colorado Plateau.

Phanerozoic Tectonic Evolution of Central California and Environs

“…Con tinental lithosphere likely was stripped from beneath the western part of the continental margin and accumulated in the modern Rocky Mountain and Great Plains areas (Bird, 1984(Bird, , 1988. Laramide thick-skinned deformation and related sedimentation are consistent with NE-SW rapid convergence with the Farallon plate (Dickinson et al, 1988;Yin and Ingersoll, 1997).…”

Drainage reorganization and Laramide tectonics in north‐central New Mexico and downstream effects in the Gulf of Mexico

“…The El Rito, Galisteo, and Diamond Tail formations are interpreted to be deposited within a single Laramide basin (Dickinson et al, ; Ingersoll, Cavazza, Baldridge, & Shafiqullah, ; Lucas, ; Yin & Ingersoll, ), one of several north‐south trending “axial” basins developed between “perimeter” basins to the east and “ponded” basins to the west (Dickinson et al, ). Dickinson et al () defined axial basins as elongate depocenters with small areas, high‐relief margins, and dominated by alluvial deposition.…”

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“…Yin and Ingersoll (1997) interpreted Ancestral Rocky Mountain and Laramide faults in the Southern Rocky Mountains as mostly dip slip, and that the observed dextral basement separations therefore must be Proterozoic. They cited a lack of defi nitive evidence for strike slip during the Phanerozoic orogenies, but did not produce compelling evidence for their preferred dip-slip model (see Cather, 2004, p. 236, for a critique of their Laramide model).…”

“…This controversy derives in part from the lack of defi nitive piercing points in Phanerozoic rocks of the region. As a result, dextral slip has variously been inferred to have occurred primarily during the Proterozoic (Montgomery, 1963;Yin and Ingersoll, 1997;Fankhauser and Erslev, 2004;Wawrzyniec et al, 2007), mostly during the late Paleozoic Ancestral Rocky Mountain orogeny (Baars and Stevenson, 1984;Woodward et al, 1999), mostly during the Late Cretaceous-Eocene Laramide orogeny (Chapin and Cather, 1981;Chapin, 1983;Karlstrom and Daniel, 1993;Daniel et al, 1995;Bauer and Ralser, 1995;Cather, 1999), or during both the Ancestral Rocky Mountain and Laramide orogenies (Cather, 2004;Cather et al, 2006). The possible regional kinematic role of the Picuris-Pecos fault during Proterozoic deformations is unclear; regional strain analysis suggests lateral slip on the fault during known Proterozoic deformations was probably sinistral (Cather et al, 2006).…”