--> Abstract: Delineation Of Subsurface Proterozoic Chuar Group / Unkar Group (Grand Canyon Supergroup) Sedimentary Basin Deposits In Northern Arizona Utilizing Gravity And Magnetic Geophysical Techniques, by J. M. Seeley and G. R. Keller; #90928 (1999).

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SEELEY, JOHN M., and G. RANDY KELLER
Dept. of Geological Sciences, The University of Texas at El Paso, El Paso, TX

Abstract: Delineation of Subsurface Proterozoic Chuar Group / Unkar Group (Grand Canyon Supergroup) Sedimentary Basin Deposits in Northern Arizona Utilizing Gravity and Magnetic Geophysical Techniques

Sedimentary rocks of the Middle and Late Proterozoic Unkar and Chuar Groups, respectively, are exposed only in eastern portions of the Grand Canyon in northern Arizona. The Chuar Group has gained recent attention as a hydrocarbon source rock due to its high TOC (total organic carbon) concentrations (up to 5%). Unkar and Chuar Group rocks were down faulted during Proterozoic extension, uplifted during Laramide compression, and presently comprise isolated half grabens that dip northeast. From Grand Canyon exposures, one can infer that Unkar and Chuar Group rocks occur in the subsurface to the north and east of the Grand Canyon. Whether or not these rocks occur in the region to the east and southeast of the Grand Canyon is not known, and is the focus of this study.

As the only known outcrops of the Unkar and Chuar Groups occur within the Grand Canyon, other methods of locating these potential source rocks need to be employed. This study utilizes conventional gravity and magnetic geophysical techniques, existing well control, upper crustal velocity estimates from previous studies, and other useful information to locate and model subsurface Unkar and Chuar Group sedimentary rocks. The objectives of this study are: 1) to delineate basement structure using gravity and magnetics; 2) to model half grabens comprised of Unkar and Chuar Group rocks; and, 3) to assess specific areas for hydrocarbon potential.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas