Tertiary cooling and tectonic history of the White River uplift, Gore Range, and western Front Range, central Colorado: Evidence from fission-track and 39Ar/ 40Ar ages

GSA Special Papers
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Abstract

Apatite fission-track (AFT) data from Proterozoic and Paleozoic rocks in the mountains of north central Colorado (White River Uplift, Gore Range, and western Front Range) record significant cooling that began with uplift and erosion related to the Laramide Orogeny and continued through the Tertiary to Pliocene time. The mountains immediately flanking the Blue River half graben (Williams Fork Mountains to the east and the Gore Range to the west) cooled significantly during the Neogene.

The AFT ages along the flanks of the Blue River half graben are significantly younger than AFT ages farther to the east in the central and eastern Front Range and to the west in the White River uplift. In both of these areas, the apatite ages suggest Laramide cooling. The Williams Fork Mountains–Gore Range zone of young AFT ages extends southward adjacent to the axis of the Rio Grande rift through southern Colorado and New Mexico. These young ages result from a combination of elevated heat flow, uplift, and erosion along the axis of the Rio Grande rift during Neogene time.

Zircons from Proterozoic rocks yield Proterozoic fission-track ages, indicating that this part of the Colorado basement has not been heated to temperatures 200 C since Middle Proterozoic time.

A sanidine 40Ar/39Ar age of 27 Ma from a rhyolite tuff just above a basal boulder conglomerate of the Troublesome Formation in a tilted fault block within the Blue River half graben shows that Tertiary deposition started there in middle Oligocene time. Xenocrystic sanidine from a basalt stratigraphically higher than the rhyolite tuff has an age of 24 Ma. Thus, the basalt is significantly younger than its postulated source, the 32 Ma laccolithic complex at Green Mountain.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Tertiary cooling and tectonic history of the White River uplift, Gore Range, and western Front Range, central Colorado: Evidence from fission-track and 39Ar/ 40Ar ages
Series title GSA Special Papers
DOI 10.1130/0-8137-2366-3.31
Volume 366
Year Published 2002
Language English
Publisher GSA
Contributing office(s) Eastern Geology and Paleoclimate Science Center, Geosciences and Environmental Change Science Center, Florence Bascom Geoscience Center
Description 23 p.
First page 31
Last page 53
Country United States
State Colorado
Other Geospatial Central Colorado
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