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Folded Paleozoic limestones at the edge of the Rio Grande

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View looking north at the mountain range-scale anticline of the Little San Pascual Mountains. The Rio Grande and Socorro Peak can be seen in the background on a striking fall afternoon.
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Snir Attia

— November 29, 2021

Bureau field geologists Dan Koning, Jacob Thacker, and Snir Attia joined John Nelson and Scott Elrick of the Illinois State Geological Survey to map folded strata in the Little San Pascual Mountains that sit just east of the Bosque Del Apache. This small mountain range was uplifted during formation of the Rio Grande Rift, but the complexly folded limestones exposed here were deposited over 300 million years ago in the Pennsylvanian! The complex folding and more cryptic, associated faulting likely resulted from regional contraction during the Late Cretaceous Laramide Orogeny. Bureau geologists and our colleagues from the Illinois State Geological Survey have been mapping related strata and structures in adjacent areas to the north and south for a long time.

— Snir Attia, Field Geologist, NMBGMR

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NMBGMR and Illinois State Geological Survey geologists discussing the geology of the mountain range. The Fra Cristobal and southern San Mateo Mountains can be see, in the background to the southwest, with the Mesa del Contadero adjoining the Rio Grande in the midground.
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Snir Attia
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Geologic mapping tends to involve quite a bit of hiking uphill.
(click for a larger version)
Snir Attia