RYER, THOMAS A., The ARIES Group, Inc., Louisville, CO

ABSTRACT: The Upper Cretaceous Ferron Sandstone of Central Utah: An Overview

The Ferron Sandstone represents the distal part of a major clastic wedge of predominantly sandy material that prograded into the western margin of the Interior Cretaceous seaway during the middle and late Turonian. Some authors have attributed this clastic wedge primarily to tectonic processes, but other authors attribute the wedge to fluctuations in sea level. A case can be made that both factors were important: eustasy may have exerted the dominant influence during deposition of the lower part of the Ferron; an increase in the flux of sediment caused by tectonic factors may have exerted the dominant influence during deposition of the upper part.

The upper part of the Ferron consists of deltaic strata. As many as eight transgressive-regressive cycles of sedimentation have been recognized. The origin of this level of cyclicity is enigmatic. Its scale and pervasiveness point to an allocyclic driving mechanism. The transgressive-regressive cycles are identified on outcrop on the basis of progradational delta-front sandstone units. These are at the scale of the "member" in traditional stratigraphic description and at the "parasequence" or "parasequence set" level of some authors. The older of the upper Ferron delta-front units were deposited largely by river-dominated deltas, and the younger units by wave-dominated deltas.

The older delta-front units can be further subdivided into small-scale progradational units that are perhaps best referred to as "parasequences." They are probably of autocyclic origin, recording shifting of deltaic lobes and/or avulsion events that led to repositioning of the river-dominated deltaic complexes.

AAPG Search and Discovery Article #90993©1993 AAPG Rocky Mountain Section Meeting, Salt Lake City, Utah, September 12-15, 1993.