50-1 Laramide-Age, Oblique-Slip Faults in Texas

Session: Latest Research Advances in Structural Geology and Tectonics

Presenting Author:

CHRISTOPHER ZAHM

Authors:

ZAHM, CHRISTOPHER K¹, UKAR, ESTIBALITZ², FALL, ANDRAS³, STOCKLI, LISA⁴, STOCKLI, DANIEL⁵

Abstract:

Understanding the timing and origin of Laramide-age faulting is critical for reconstructing intraplate tectonic evolution and evaluating its implications for subsurface reservoir systems. Recent advancements in U–Pb calcite geochronology provide direct age constraints on brittle deformation and offer new insights into the kinematic regimes associated with the Laramide Orogeny. In this study, we integrate U–Pb dating of calcite mineralization with detailed structural analysis from South and West Texas to refine the spatial and temporal extent of Laramide-related deformation. U–Pb analyses of calcite veins and fault surfaces from outcrops located over 60 km north of previously mapped Laramide compressional folds yield oblique-slip fault ages ranging from 59.4 ± 0.9 to 36.0 ± 4.6 Ma. These ages overlap with the peak period of Laramide uplift and erosion, suggesting that northeast-trending faults in the Carta Valley Fault System, as well as faults at the southern terminus of the Pecos River and near Sanderson, Texas, were active during this orogenic phase. Structural orientations and kinematic indicators from these sites are consistent with northeast-directed Laramide compression. Additionally, fluid inclusion analyses from calcite cements at the Sanderson locality indicate formation depths of 2–4 km, confirming that faulting occurred under significant burial conditions. These results extend the known foreland limit of Laramide-age deformation well beyond previously recognized boundaries, demonstrating that Laramide-related brittle faulting affected a broader region of intraplate Texas than previously documented. The combined geochronologic and structural framework not only refines the chronology of deformation but also offers insight into the timing of associated sedimentation, uplift, and subsidence within the Laramide foreland and northern Gulf of Mexico Basin.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-4829

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