T83 Exploring Connections between Extension, Sedimentation, and Volcanism in the Rio Grande Rift

Monday, 23 September 2019
8:00 AM - 12:00 PM
Room 231ABC, North Building

A SHALLOW RIFT BASIN SEGMENTED IN SPACE AND TIME: THE SOUTHERN SAN LUIS BASIN, RIO GRANDE RIFT, NORTHERN NEW MEXICO

Paper number: T83-3
Program: Technical Sessions
Time: 8:35 AM – 8:50 AM

Authors

Abstract

Interpretation of gravity, magnetotelluric (MT), and aeromagnetic data coupled with geologic constraints within the southern San Luis basin reveals a shallower and narrower basin with a more complex structural history than indicated by previous modeling efforts. Spatial variations of low-density basin fill thickness are estimated primarily using a 3D gravity inversion method that improves on previous modeling efforts by separating the effects of the low-density basin fill from the effects of pre-rift rocks. Five distinct subbasins are recognized within the broader southern San Luis Basin. The oldest and shallowest (~400 m-deep), north-trending Las Mesitas graben formed along the northwestern basin margin coeval to the transition between Oligocene volcanism and the onset of rifting. The ~2 km-deep Tres Orejas subbasin formed in the southwestern portion of the basin, coeval to development of the southern-bounding Embudo fault zone and a hypothesized fault zone along its western margin. The Sunshine Valley-Costilla Plain (~1.2 km deep), Questa (~0.8 km deep), and Taos (~1.8 km deep) subbasins occupy the eastern part of the southern San Luis Basin and are bound on the east and west by the west-down, active southern Sangre de Cristo fault zone and east-dipping Gorge fault zone, respectively. These were the dominant structures controlling post-20 Ma subbasin development. Tectonic activity within all subbasins primarily culminated with emplacement of the Plio-early Pleistocene Taos Plateau volcanic field, and rift-related subsidence became more narrowly centered on the eastern margin of the basin, controlled mainly by the linked southern Sangre de Cristo and Embudo fault zones.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-334379

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