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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JOIHO

beds was tentati vely i denti fi ed as the Gartra Sandstone and mapped as the
contact between the two fonnations. The relatively weak rock of the State
Bri dge and Chi nl e Fonnati ons fonns gently roll i ng topography covered by scrub
oaks through the middle two miles of the upper canyon section of the study
area, causing the valley to widen between Miller Creek and about one mile
upstream of Veatch Gulch: The combined thickness of the two fonnations is
about 2.000 feet. They mark the upper 1 imi t of the red bed deposi ti on that
started in Pennsylvanian time.

Entrada Sandstone (Je)
The Chi nl e Fonnati on is overl ai n by the Jurassi c Entrada Sandstone whi ch is
di sti ngui shed by the spectacular, near verti cal, pal e orange sandstone cl iffs
fonned on either side of the White River valley. The sandstone is of eolian
origin and is unifonnly medium grained, poorly cemented, and crossbedded. The
total thickness of the fonnation ranges from 120 to 160 feet. The
northwesterly dipping cliffs intersect the valley floor just upstream of the
confluence of Veatch Gulch.

Morrison Fonnation (Jm)
The Jurassic Morrison Fonnation overlies the Entrada sandstone. The basal 150
to 200 feet of the fonnation is composed of white-to-gray, well sorted, well
cemented, fine-to medium-grained sandstone. This unit fonns fairly steep
slopes and cliffs on the right side of the river and caps the dip slopes on
the left side. The upper 500 to 600 feet of the Morrison is characterized by
vari egated green and purpl e mudstone and shal e. The best exposure of these
weak units is in the road cut just upstream of Agency Park. The thickness of
the Morrison Fonnation in the study area is approximately 800 feet.

Dakota Sandstone (Kd)
The highest elevations in the eastern part of the mapped area are fonned by
the Cretaceous Dakota Sandstone that unconfonnably overlies the Morrison
Fonnati on and fonns northeasterly trendi ng ri dges and gentl e northwest dip
slopes. The sandstone is light grey-to-tan, fine-to medium-grained, and well
cemented. The Dakota has a thickness of 50 to 100 feet.

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