60-13 Paleogeography and provenance of the Telluride Conglomerate, western Colorado

Session: 2YC and 4YCU Geoscience Student Research Poster Showcase

Poster Booth No.: 13

Presenting Author:

Grant Barnes

Authors:

Barnes, Grant¹, Aslan, Andres², Cumella, Steve³, Gonzales, David A.⁴, Karlstrom, Karl E.⁵, Heizler, Matthew T.⁶, Schwartz, Darin⁷

Abstract:

The Telluride Conglomerate represents a Late Eocene to Early Oligocene fluvial system that drained the western margin of the Southern Rocky Mountains.  The deposits form a clastic wedge that thickens from east to west to as much as ~300 m near Lizard Head Pass and Sheep Mountain in Colorado.  Study of a relatively thick and undeformed sequence of the Telluride Conglomerate at Sheep Mountain, along with nearby outcrops, indicates that the Telluride Conglomerate represents a mosaic of tributaries and larger rivers, which drained different bedrock regions.

Gravel clasts in the Telluride Conglomerate are represented by at least two distinct compositions: 1) Precambrian quartzite and granite and Paleozoic sedimentary clasts, and 2) late Cretaceous(?) shallow intrusive igneous rocks and Precambrian quartzite.  Mapping the distribution of different Telluride Conglomerate clast compositions indicates that Telluride tributaries drained upland areas including 1) the Needle Mountains uplift (south) and 2) the Ouray area (north).  The Needle Mountains uplift supplied Precambrian granite and quartzite along with Paleozoic sedimentary clasts whereas the Ouray area supplied shallow intrusive igneous clasts as well as Precambrian quartzite.  The Telluride Conglomerate at Sheep Mountain is represented chiefly by gravelly sandstone and sandy conglomerate and represents a distal deposit relative to the proposed source areas.  Clast lithologies are predominantly Precambrian quartzite, shallow intrusive igneous rocks, and sedimentary rocks.  It is possible that the Sheep Mountain section and adjacent areas represent mainstem rivers that were fed by tributaries draining a combination of the Needle Mountains and Ouray.  Paleocurrent data supports the suggestion that Telluride tributaries flowed southwest away from Ouray towards Lizard Head Pass and Sheep Mountain. 

U-Pb detrital-zircon (DZ) dating of the basal Telluride Conglomerate at Sheep Mountain did not produce a useful maximum depositional age (MDA) although previous DZ MDAs suggest a Late Eocene to Early Oligocene age for the Telluride Conglomerate in this area.  The Sheep Mountain DZ age spectrum is consistent with reworking of Precambrian, Paleozoic, and Mesozoic rocks including Late Cretaceous intrusive rocks near Ouray, and supports provenance interpretations based on clast compositions.  A paleogeographic implication of these results is that highlands existed during Telluride Conglomerate deposition that probably included the Ouray area in addition to the Needle Mountains uplift.

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

doi: 10.1130/abs/2025AM-7861

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