T278 The Rio Grande Rift: Exploring Connections between Deformation, Magmatism, Metamorphism, Sedimentation, Mineralization, and Mantle-to-Surface Processes during Continental Extension

Wednesday, 25 September 2024
1:30 PM - 5:30 PM
304A

KINEMATIC AND GEOCHRONOLOGIC EVIDENCE DOCUMENTING ROTATION OF CRUSTAL EXTENSION DIRECTION AND NARROWING OF RIFT FAULTING IN THE SUNKEN BLOCK GRABEN OF THE SOUTHERN RIO GRANDE RIFT, TRANS-PECOS TEXAS

Paper number: T278-10
Program: Technical Sessions
Time: 3:40 PM – 3:55 PM

Authors

Abstract

We present new fault-kinematic data (n = 308) from six locations across the Sunken Block and Black Gap grabens in the southern Rio Grande rift of Trans-Pecos Texas. Kinematic analysis indicates a prominent NE-SW extension direction preserved at each location, while locations within the Sunken Block also show evidence for multiple incompatible fault populations and changing extension directions through time. Three U-Pb ages of oriented calcite slickenlines in the Sierra del Carmen and Black Gap graben constrain a NE-SW direction of S1 to as old as 30.1 ± 3.1 Ma and as young as 13.7 ± 0.9 Ma. These data support a model in which earliest extension was oriented NE-SW and rotated clockwise to EW and NW-SE after 13.7 Ma, and in which later extension was concentrated within the Sunken Block as the active region of extension narrowed. Clockwise rotation after 13.7 Ma is in agreement with a widely cited regional clockwise rotation of tension and extension at ~10 Ma reported across the Basin and Range province. These observations are also similar to kinematic studies of the central Rio Grande rift, although the timing of rotation is significantly younger in the southern rift (<13.7 Ma), than in the central rift (early Miocene). Together, new and compiled fault kinematic data from the Rio Grande rift suggest that rotation of extension was a time-transgressive process, and that extension was driven by both lateral and underlying plate boundary forces as the transform plate margin lengthened and exerted greater influence on the interior of the North American Plate.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-402545

© Copyright 2024 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.