Geological Setting

Recurrent movements on the Paris Thrust, first and westernmost of a progressive sequence of overthrusts (Figure 1), produced an episodically uplifted (Figure 2) sedimentary source area in southeastern Idaho. The Early Cretaceous, synorogenic clastic sediments derived from that highland were transported eastward and deposited in a tectonic foredeep in southeasternmost Idaho and westernmost Wyoming (Wiltschko and Dorr, 1983). Crustal subsidence beneath the foredeep mainly was caused by thrust...

Gannett Group

The Gannett Group has yielded very little fossil vertebrate material, all of it very fragmentary and specifically unidentifiable, in contrast with the partially coeval Cloverly Formation which has produced abundant and diverse material of excellent quality in central Wyoming (Ostrom, 1970). Mansfield (1927) reported unidentified fossil bone from the Gannett Group along Tincup Creek (Figures 1 and 3) in southeastern Idaho, but the exact stratigraphic and geographic provenance of that material is...

Smiths And Lower Bear River Formations

Rubey (1973) and Durkee ( 1979) described the stratigraphy and sedimentology of the Smiths Formation. The Bear River Formation is discussed in Wanless et al. (1955). The Smiths Formation is a coeval, western, stratigraphic extension of the black shales and overlying HG. 3 Aerial photographs, enlarged (see bar scales) from I S.Department of Interior. Geological Survey. EROS Data Center images INHAP80000096 (7 27 1980) and IN H A P80000198 (9 22 1980). (a) Fossil sites A-J in Wayan Formation and...

Sage Junction Formation

The type locality of the Sage Junction Formation is 1.5 miles 2.4 Km west of Sage, Wyoming Rubey, 1973 where the formation now is only poorly exposed. Numerous thin porcelanite beds occur throughout the formation there and a few beds of coal are present in the lower part. Porcelanites also occur in the formation east of Wayan, Idaho, 85 miles 137 Km to the north. There it is described by Oriel and Piatt 1980, Preston Quadrangle as gray and tan siltstone and sandstone, minor quartzite,...

Dominantly Lacustrine

1 IG. 2 Stratigraphic correlation chart. From Rubey, 1973 Schmitt and Moran, 1982 Wiltschko and Dorr, 1983 Herman, Wilkinson and Dorr, 1984. 1982 Schmitt and Sippel, 1983 . The sediments accumulated on a succession of eastwardly and southeastwardly prograding alluvial fans Armstrong and Oriel, 1965 Eyer, 1969 during deposition of the Ephraim, Bechler, Wayan including Thomas Fork and Quealy , Sage Junction and lower part of the Frontier formations. Fan progradations were interrupted by...

Wayan And Sage Junction Formations And Coeval Units

During the middle and late Albian, the margin of the Mowry Seaway fluctuated in an east-west direction across much of western Wyoming, as recorded in the upper part of the Bear River Formation and the overlying Aspen Formation in the Hoback, Wyoming and Snake River ranges. Freshwater and brackishwater mollusks, including Ostrea, alternate stratigraphically there Wanless et al1955 . Royse et al. 1975 reported abundant marine microfossils of several types and from several levels elsewhere in the...

Summary And Conclusions

The Early Cretaceous Gannett Group and the Wayan-Sage Junction couplet with its related tongues are two successive, complex, synorogenic clastic wedges comprised of sediment that was derived from highlands produced by uplift of the Paris Thrust plate. Deformation occurred during an early phase of the Sevier Orogeny. Deposition took place in a foredeep created by crustal loading by that overthrust plate. The eastwardly prograding, wet alluvial fans in that tectonic setting encompassed both...