ABSTRACT

A boulder conglomerate facies is found almost continuously along the western edge of the Cretaceous seaway in central and southern Utah. At the present time, north-south continuity of the facies is disrupted by Tertiary volcanic cover and basin and range-type faulting, making the original distribution of conglomerate difficult to follow.

Careful physical comparison of good conglomerate exposures and developing palynologic control in fine-grained equivalent sediments to the east allows some correlation of the facies trend and indicates a close time relationship with Sevier thrust events. Silicic and carbonate boulder conglomerates were limited to a relatively narrow east-west zone directly in front of the leading thrust edge. Rapid eastward transition to well-sorted sand and coastal marine conditions suggests deposition relatively close to base level.

Major unconformities within the conglomerate sequence and the upper and lower limits of coarse clastic sedimentation define several depositional episodes. It appears that the conglomerate packages are related to specific Sevier orogenic events.

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