Publication Date


Document Type


First Advisor

Weiss, Malcolm P. (Malcolm Pickett), 1921-

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Geology


Geology--Utah; Geology; Stratigraphic--Eocene; Petrology--Utah


The Colton Formation consists of green calcareous claystone, red, green and variegated mudstone, speckled mudstone and siltstone, thin-bedded carbonates, siltstones and sandstones, and channel sandstone. Sedimentary structures include dessication cracks, burrows, rootlets, graded bedding and cross bedding. Ostracodes, gastropods, pelecypods, charophytes, bone fragments and fish scales constitute the fossil assemblage; of these only the first two are numerous and locally conspicuous on the outcrop. The Colton Formation thins northward and westward from a maximum thickness of 853 ft. (260 m) in the southeast quadrant of the plateau. In the northwest quadrant the limestones are thicker, and more abundant relative to the mudstones. Sections in the southwest quadrant contain fewer limestone beds and more red mudstones. Channel sandstones are more abundant in the sections to the east and southeast. Speckled mudstones that contain analcime are absent in the southwest but are found at or near the top of the other sections. The geographic and stratigraphic distributions of rock assemblages are consistent with the model of an oscillating lake surface and consequent transgression and regression of near-shore lacustrine and nearby alluvial-deltaic facies. Green calcareous claystone (locally dolomitized) interbedded with thin limestones and calcareous siltstones is representative of a fresh water lake-carbonate flat environment. Units composed of channel sandstone, thinbedded siltstone and sandstone, green calcareous claystone, and red and variegated mudstone are indicative of alluvial sediments that accumulated along the lake-margin to form deltaic deposits. Speckled mudstone and siltstone belong to the group of saline lake deposits. The Colton Formation represents a mixed fresh water and saline lacustrine, and deltaic unit formed during the waning of Flagstaff Lake and onset of Lake Uinta, and separates the fully lacustrine Flagstaff and Green River Formations. In the area immediately west and northwest of the study area, lacustrine conditions were continuous across this time interval as Flagstaff Lake transformed into Lake Uinta.


Includes bibliographical references.||Includes illustrations.


ix, 132 pages




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