28 Geologic Mapping in the West (Posters)

This poster session highlights geologic mapping in the western Cordillera and Rocky Mountains. We encourage submissions that explore bedrock and surficial geology, geophysics, hydrology, hazards, and more. Both professional and student submissions are welcome.

Tuesday, 19 May 2026
8:00 AM - 5:30 PM
Alvarado D/E

Geologic Map of the Socorro 30- x 60-minute Quadrangle, Socorro, Torrance, and Valencia Counties, New Mexico

Paper number: 28-0
Program: Technical Sessions
Time: 8:00 AM – 8:15 AM

Authors

Abstract

The Socorro 30- x 60-minute quadrangle (1:100,000 scale) contains a wide variety of rock types and was affected by three tectonic events: Ancestral Rocky Mountains orogeny (Pennsylvanian), Laramide orogeny (Cretaceous–early Eocene), and Rio Grande rift extension (34–0 Ma). To the west lies the Rio Grande rift and its namesake river. Proterozoic rocks are exposed at the bases of rift-flank uplifts and unconformably overlain by Mississippian–Pennsylvanian, limestone-rich sedimentary strata. Extensional and minor contractional features extend 15–20 km eastward from the rift across the Quebradas highlands. The eastern half of the quadrangle is relatively undeformed except for the 20 km-wide Torres syncline and Chupadera fault. Permian rocks form a colorful red-bed sequence (Abo Formation and Yeso Group) capped by the hard Glorieta Sandstone and limestone-dominated San Andres Formation. The Triassic section is ~200 m thick and is a reddish- to chocolate-brown sequence of mudstones, sandstones, and minor conglomerate. The pastel-colored Morrison Formation pinches out to the southwest. The yellowish-tan Cretaceous section is ~600 m thick sequence of sandstones through shales; it includes three marine tongues overlain by the terrestrial Crevasse Canyon Formation. A Laramide uplift in what is now the Rio Grande rift resulted in 1,500–1,900 m of exhumation of the Mesozoic and Permian sequence plus variable erosion of Pennsylvanian strata. Volcanic activity characterized the late Eocene–late Oligocene. This produced several hundred meters of volcaniclastic, coarse sediment that interfingers with felsic ignimbrites and lavas ranging from rhyolite through basaltic andesite. East of the rift, northeast and east-northeast-trending dikes are 33–30 Ma and 27–28 Ma; these possibly relate to the Socorro (32.35 Ma) and Mount Withington (27.6 Ma) calderas to the southwest. Dikes penetrated the Yeso Formation and commonly warped overlying units. Santa Fe Group clastic sediment fills the Rio Grande rift and is divided into the Popotosa and Sierra Ladrones Formations. The upper Popotosa Formation has clayey, playa-lake sediment that interfingers outwards into fan deposits. The Sierra Ladrones Formation has sandy axial-river deposits interfingering with gravely fan deposits. Progressive downcutting of the Rio Grande over the past ~800 ka has produced a ~100 m deep valley flanked by four general terrace flights. Dating of the second-from-bottom terrace deposit, the Matanza Formation, indicates at least two cut-and-fill events during 130–62 ka.

Geological Society of America Abstracts with Programs. Vol. 58, No. 4

doi: 10.1130/abs/2026RM-410702

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