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Date Permissions Signed
Date of Award
Master of Science (MS)
Suczek, Christopher A., 1942-2014
Vance, Joseph A., 1930-
Pevear, David R.
Upper Eocene to lower Oligocene sedimentary rocks in the Lake McMurray area of Skagit County, Washington, consist of approximately 1500 m of conglomerate, sandstone, shale, and siltstone which were deposited in fluvial and marine environments along the continental margin. These rocks are known as the rocks of Bulson Creek.
Two main lithofacies can be recognized within the sequence: the lowest is nonmarine and consists of poorly sorted, thick, and structureless conglomerate with interbedded sandstone, siltstone, shale, and minor coal lenses; the upper lithofacies grades from a transitional nonmarine facies to a shallow water marine facies that consists of well sorted, fossiliferous pebbly sandstone, sandstone, and siltstone. The lower lithofacies rocks lie unconformably on paleosols developed on pre-Tertiary rocks. The upper lithofacies rocks lie unconformably over the lower lithofacies rocks.
At least three periods of tectonism and two periods of deposition are recognized. The Devils Mountain fault is a major east-west trending structural feature along which there has been a long and complex history of motion. The deformation of the rocks in the Lake McMurray area can be attributed to movement along this fault, which forms the northern border along which the Bulson Creek rocks crop out. Deposition of the lower lithofacies rocks followed compressional folding associated with normal faulting. These rocks were folded prior to the deposition of the upper lithofacies, as is evident by the angular unconformity between the two units. Normal faulting along the Devils Mountain fault tilted these units to the south.
Bulson Creek, Rocks of Bulson Creek, Sedimentary rocks
Western Washington University
Subject – LCSH
Sedimentary rocks; Geology, Structural; Geology, Stratigraphic--Eocene; Geology, Stratigraphic--Oligocene; Petrology--Washington (State)--Skagit County
Skagit County (Wash.)
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Marcus, Kim Lance, "The Rocks of Bulson Creek: Eocene-Oligocene Sedimentation and Tectonics in the Lake McMurray Area, Washington" (1981). WWU Graduate School Collection. 674.