Monday, 6 October 2008: 8:55 AM
George R. Brown Convention Center, 332CF
This paper provides a paleoenvironmental analysis of the Upper Cretaceous (middle to upper Turonian) Ferron Sandstone in the Henry Mountains region of south-central Utah. In this region, the Ferron Sandstone records progradation of a series of river-dominated, wave-influenced delta lobes eastward into the Western Interior Seaway. In this work, stratal packages have been correlated over c. 30 km from Caineville township on Utah Highway 24 southward (obliquely along depositional strike) to Blind Trail, and over another section of c. 5 km further south at The Post. The lower half of the Ferron Sandstone comprises crudely thickening- and coarsening-upward intervals 2-10 m thick, recording progradation of the subaqueous portions of delta lobes into the region. Individual parasequences, and even individual beds <1 m thick, can be physically correlated over several km along strike, implying considerable lateral continuity of sands in the strike direction. In contrast, facies changes occur in the depositional dip direction over much shorter distances. The upper half of the Ferron Sandstone comprises a stack of erosionally-based channel sandstone bodies, with subordinate overbank mudrocks and thin carbonaceous shales or coals. Bases of some of these bodies are regionally significant erosion surfaces, and may represent sequence boundaries. Similarity in lithofacies, stacking patterns, and sediment body geometry, including presence of sharp-based mouth bar sandstones, suggests an analogy with the modern Burdekin River Delta of NE Australia, the Holocene delta of which was also constructed as a series of overlapping lobes. The Ferron and Burdekin Deltas are closely comparable, suggesting that the Ferron was the product of modest-sized deltas prograding into shallow water under conditions of limited and varying accommodation.