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The AAPG/Datapages Combined Publications Database

Utah Geological Association

Abstract


Geology of Northwest Utah, 2006
Pages 29-49

Geology of the Rose Canyon Area, Salt Lake County, Utah - the Exhumed Flank of the Bingham Volcanic Center

Robert F. Biek

Abstract

Rose Canyon and its tributaries are eroded into the southeast flank of the Bingham volcanic center. Much of the Rose Canyon area is underlain by a sequence of middle Eocene, 39- to 38-million-year-old debris-avalanche and lahar deposits and minor lava flows – typical rocks that made up the distal slopes of a composite volcano that once towered over Bingham. Somewhat younger early Oligocene, 32- to 31-million-year-old volcanic rocks, genetically unrelated to those of the Bingham suite, unconformably overlie the Bingham volcanic rocks at Rose Canyon. New 40Ar/39Ar ages on the rhyolite plug of Shaggy Peak and the andesite plug of Step Mountain, considered part of the younger volcanic suite, indicate that these 36- to 35-million-year-old plugs, which intrude block and ash-flow tuffs near the entrance to Rose Canyon, are of late Eocene age; Step Mountain in particular is an extraordinary volcanic neck with prominent horizontal columnar jointing. Reinterpreted exposures of tuffaceous mudstone and siltstone, volcaniclastic sandstone, and oncolitic limestone exposed in nearby Dry Canyon – some of which is silicified and was previously thought to belong to the Pennsylvanian Oquirrh Group – shows that the lower slopes of the Bingham volcanic center once held a small middle Eocene lake basin. The youngest volcanic rocks in the area erupted in the early Oligocene from nearby South Mountain, which is capped by a distinctive volcanic breccia interpreted to have formed as a collapse breccia in the throat of the South Mountain volcano. Collectively, these volcanic rocks bury paleotopography developed on Paleozoic strata folded into northwest-trending anticlines and synclines during the Late Cretaceous to early Tertiary Sevier orogeny. They are exposed today at the west end of the Traverse Mountains, an anomalous, east-west-trending range that owes its existence to the long-lived, intermittently active Cheyenne suture zone.

The Utah Geological Survey recently published 1:24,000-scale geologic maps of the Traverse Mountains, including the Rose Canyon area that drains the scenic, northwest part of the range and the southwest corner of Salt Lake Valley. These new maps, and new geochemical and age data, together with previous geologic studies, help to reveal the fascinating but little known geology of the Rose Canyon area. Although most of this area is privately owned and is being enveloped by a wave of suburban development, much of its geology can be seen and interpreted from Yellow Fork Canyon County Park and along public right-of-ways.


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