--> ABSTRACT: Paleocurrent Analysis of Cretaceous Mitchell Formation, North-Central Oregon, by Craig A. Sandefur and Lanny H. Fisk; #91022 (1989)

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Paleocurrent Analysis of Cretaceous Mitchell Formation, North-Central Oregon

Craig A. Sandefur, Lanny H. Fisk

Cretaceous sedimentary rocks in north-central Oregon contain both potential petroleum source rocks and reservoir rocks. Thus, determining their extent under the cover of Tertiary volcanics is of great importance to future petroleum exploration in the southern portion of the Columbia basin. Limited studies of sediment transport direction have been previously reported by several workers; however, no conclusive evidence was obtained. This study was undertaken to resolve the differences in the previously presented interpretations. The outcropping sedimentary sequence represents part of a subsea fan complex consisting of fan-apron facies turbidites and mudstones (Hudspeth mudstone facies) and channel-facies conglomerates and sandstones (Gable Creek conglomerate facies). Paleoc rrent data derived from sole marks, flute casts, clast imbrication, and alignment of elongate plant fragments document that sediment transport was primarily from the south-southeast toward the north-northwest. Thus, the greatest potential for petroleum production from Cretaceous sediments in north-central Oregon lies to the west and northwest of the Mitchell area in northeast-southwest elongated rift basins. These basins, presumably containing thick accumulations of Cretaceous marine sediment fill, are now evidenced by large gravity and magnetic lows.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.