WSP02105

• File Number: 8200.765
• Description: White River General
• State: CO
• Basin: Yampa/White
• Water Division: 6
• Date: 5/1/1986
• Author: Morrison-Knudsen
• Title: White River Geotechnical Study - Final Report - Volume I
• Water Supply Pro - Doc Type: Report/Study

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MJl131

3. REGIONAL GEOLOGY

3.1 Structure

Plate 2 is a reproduction of the USGS geologic map of Colorado in the region
of the White River Basin. The study area is located in the Southern Rocky
Mountain and Colorado Plateau physiographic provinces. The provinces are
separated by the Grand Hogback, a northerly-trendi ng monocl i nal ri dge that is
cut by the White River just west of the town of Meeker. The White River
structural basi n to the east of the Grand Hogback is i nfl uenced by the Whi te
Ri ver Upl ift, a broad northwesterly-elongated dome about 50 mil es in 1 ength
and 40 miles wide. The region to the west of the Grand Hogback is dominated
by the Piceance Creek Basi n, a structural depressi on about 100 mi 1 es long and
about 40 miles wide. These two significant regional features, the White River
Upl ift and the Pi ceance Creek Basi n, were fonned over a peri od of about 35
mi 11 ion years begi nni ng near the end of the Mesozoi cEra duri ng the Larami de
Revolution about 60 million years ago. Block faulting, associated with
tectonics, ,is most prevalent in the southern part of the White River Uplift;
faults generally trend east-west or northwesterly.

3;2 Stratigraphy

Plate 3 is a geologic column illustrating regional stratigraphy, including
ages and relative thickness of the geologic units mapped in the study area.
The Pl ate al so serves as a key to the Project Geologic Map. Over most of the
region; the surface rocks are composed of a thick sequence of sedimentary
fonnations rangi ng in age from Pennsyl vanian to Tertiary. Small areas of
Precambrian crystalline rocks and early Paleozoic sedimentary rocks are
exposed in the White River Uplift and Tertiary lava flows fonn the "Flat Tops"
of the upl ift. Unconsol i dated Quaternary deposits are found throughout the
region.

The 01 dest rocks in the Whi te River Basi n are located wi thi n the Whi te River
Uplift, cropping out in small areas along the South Fork of the White River.

3-1