There has been confusion for many years regarding the lithology and age of the rocks exposed in the Muddy Ranch Inlier in north-central Oregon. Taylor (1960) referred to these rocks as metasediments and informally named them the "Muddy Ranch phyllite". My studies indicate the inlier consists of weakly metamorphosed siltstone, mudstone, and less abundant sandstone.
Due to the absence of fossil evidence, it was not possible to determine the age of these rocks. However, from the stratigraphic setting and correlation with similar rocks exposed along structural trend to both the northeast and southwest, rocks of the Muddy Ranch Inlier may be Early Eocene in age, as reported for the "Hay Creek Formation" by Wareham (1986). The depositional environment of these rocks is uncertain but is interpreted to be a submarine fan based on the presence of turbidites and lithologic similarities to the "Hay Creek Formation".
As potential petroleum source rocks the organic-rich siltstones of the "Muddy Ranch Formation" are overmatured. However, this may only indicate that these rocks have produced oil or gas in the past. Occurrences of asphalt and shows of both oil and gas in wells in the vicinity indicate the possibility of commercial quantities of hydrocarbons. Besides petroleum, the Muddy Ranch also has potential to produce metallic minerals such as copper, gold, silver, and cinnabar. In addition, bentonitic clay deposits in the Clarno Formation show promise for commercial production.
Lanny H. Fisk
H. Paul Buchheim
Ivan E. Rouse
Master of Science (MS)
Year Degree Awarded
Date (Title Page)
Library of Congress/MESH Subject Headings
Rocks, Sedimentary -- Oregon; Rocks -- Analysis; Geology, Economic -- Oregon.
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This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.
Kamal, Mustafa, "Geology and Economic Potential of the Muddy Ranch Inlier, North-Central Oregon" (1990). Loma Linda University Electronic Theses, Dissertations & Projects. 1685.
Loma Linda University Electronic Theses and Dissertations
Loma Linda University. Del E. Webb Memorial Library. University Archives