204 Paleozoic Tectonics of SW Laurentia Without Borders: Final Amalgamation of Pangea in the USA, Mexico, and South America

We invite contributions that explore the Paleozoic tectonic evolution of southwestern Laurentia during the final assembly of western Pangea. Research on Paleozoic tectonic belts in Gondwana, particularly from Mexico and South America, is especially welcome.

Tuesday, 21 October 2025
1:30 PM - 5:30 PM
HBGCC, 217B

Role of Tectonic Inheritance in the Western Delaware Basin of Texas

Paper number: 204-2
Program: Technical Sessions
Time: 1:55 PM – 2:10 PM

Authors

Abstract

The Permian Basin is a prolific petroleum province with a complex tectonic history, with events extending as far back as the Mesoproterozoic Grenville Orogeny, and as recently as induced earthquakes related to oilfield operations. Since 2017, there have been ~10,000 local ML 2.0+ earthquakes, many of which are related to the re-injection of produced water into strata above (shallow-SWD) and below (deep-SWD) shale production intervals. Regulatory action of curtailing deep-SWD within seismic response areas (SRAs) have resulted in lower seismicity rates; however, earthquake rates remain elevated.in the Northern Culberson Reeves SRA.

A 3D seismic reflection dataset spanning >1,500 km2 of the western Delaware Basin, south of the Texas/New Mexico border is used to understand the present-day nature and hazard of seismogenesis in the region. Using this data, we identify three distinct levels of faulting: 1) shallow, strata-bound faults (SSB) which are steeply-dipping (~60–80°) elongate, narrow graben, which cut upper-Permian age units, including shallow injection strata, and formed under regional extensional conditions in the Cenozoic. These SSB faults are kinematically unrelated to deeper fault systems. 2) Basement-rooted (BR) faults are moderate-to high-angle reverse and strike-slip (~50–90°) which offset the Great Unconformity and overlying Paleozoic strata including the deep injection strata. 3). IB faults occurring within the geologic basement are low-to moderately-dipping (~20–45°) thrust faults, that are truncated by the Great Unconformity. Through analysis of seismic reflector package characteristics, observation of cross-cutting relationships, and kinematic reasoning, we propose that the IB faults are the deeply buried, imbricate thrust front of the Mesoproterozoic Grenville Orogeny. BR faults developed during the diachronous Ouachita-Marathon and Ancestral Rocky Mountain orogenic events as selective reactivations and propagation of IB faults. There are several instances of BR faults nucleating at the interface of these thrusted features and the Great Unconformity, indicating an element of predisposition.

The larger magnitude earthquakes catalogued in our study area have occurred on BR and IB faults as normal slip reactivation which demonstrates the three episodes of movement in the IB faults: formation during Mesoproterozoic assembly, reactivation and propagation during Penn/Perm orogenesis, and modern reactivation due to anthropogenic agents. These observations improve our understanding of the tectonic evolution of the southern Laurentian margin during Rodinian assembly, as well as how these features influenced subsequent deformation.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413790

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