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Late Miocene-Pleistocene evolution of a Rio Grande rift subbasin, Sunshine Valley-Costilla Plain, San Luis Basin, New Mexico and Colorado

January 1, 2014

The Sunshine Valley-Costilla Plain, a structural subbasin of the greater San Luis Basin of the northern Rio Grande rift, is bounded to the north and south by the San Luis Hills and the Red River fault zone, respectively. Surficial mapping, neotectonic investigations, geochronology, and geophysics demonstrate that the structural, volcanic, and geomorphic evolution of the basin involves the intermingling of climatic cycles and spatially and temporally varying tectonic activity of the Rio Grande rift system. Tectonic activity has transferred between range-bounding and intrabasin faults creating relict landforms of higher tectonic-activity rates along the mountain-piedmont junction. Pliocene–Pleistocene average long-term slip rates along the southern Sangre de Cristo fault zone range between 0.1 and 0.2 mm/year with late Pleistocene slip rates approximately half (0.06 mm/year) of the longer Quaternary slip rate. During the late Pleistocene, climatic influences have been dominant over tectonic influences on mountain-front geomorphic processes. Geomorphic evidence suggests that this once-closed subbasin was integrated into the Rio Grande prior to the integration of the once-closed northern San Luis Basin, north of the San Luis Hills, Colorado; however, deep canyon incision, north of the Red River and south of the San Luis Hills, initiated relatively coeval to the integration of the northern San Luis Basin.

Long-term projections of slip rates applied to a 1.6 km basin depth defined from geophysical modeling suggests that rifting initiated within this subbasin between 20 and 10 Ma. Geologic mapping and geophysical interpretations reveal a complex network of northwest-, northeast-, and north-south–trending faults. Northwest- and northeast-trending faults show dual polarity and are crosscut by north-south– trending faults. This structural model possibly provides an analog for how some intracontinental rift structures evolve through time.

Citation Information

Publication Year 2013
Title Late Miocene-Pleistocene evolution of a Rio Grande rift subbasin, Sunshine Valley-Costilla Plain, San Luis Basin, New Mexico and Colorado
DOI 10.1130/2013.2494(03)
Authors C.A. Ruleman, R.A. Thompson, R. R. Shroba, M. Anderson, B. J. Drenth, J. Rotzien, J. Lyon
Publication Type Article
Publication Subtype Journal Article
Series Title GSA Special Papers
Series Number
Index ID 70100905
Record Source USGS Publications Warehouse
USGS Organization Geosciences and Environmental Change Science Center