171-4 Intra-fold Strain Analysis via Vertical-surface Mapping, Dog Canyon, Big Bend National Park, Texas

Session: Advancing Geologic Analysis with Digital Outcrops and Close-Range Remote Sensing Data

Presenting Author:

Authors:

Abstract:

Dog Canyon in Big Bend National Park, Texas (BBNP) exposes vertical beds of a portion of a reclined syncline on a ~200m x 60m cliff wall at the end of a moderate and popular hiking trail. The exposed syncline is in the footwall of the NNW-striking Santiago thrust fault. Mesoscale structures within the fold limbs are visible from the canyon floor and higher. We captured imagery of the cliff wall and converted it to a single orthomosaic photo exposing complex joint patterns that we then mapped to interpret localized strain-axis orientations documenting a three-stage deformation history between late Cretaceous or early Paleogene contraction and Neogene extension. Strain analysis indicates that earliest strain occurred by orthogonal flexure during fault-propagation folding ahead of the west-southwest-verging Santiago thrust fault. Second, the lower, upright limb of the syncline was horizontally contracted as the thrust fault cut the upper limb of the fold. Last, the fold’s hinge and upper limb extended horizontally, either upon relaxation of contraction or during Neogene extension. We are working with BBNP science staff to present a cross section and the geologic history of Dog Canyon as an interpretive wayside exhibit for visitors to the park.

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

doi: 10.1130/abs/2025AM-10374

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