Four major facies are identified in the Upper Cretaceous Shannon Sandstone Member submarine bar complex where it crops out in the Salt Creek anticline area of Wyoming. The Central Bar (trough and laminated) Facies forms the backbone of the bars. This facies is quartzitic and glauconitic, fine to medium grained and is composed of stacked sequences of predominantly trough-bedded sandstones up to 35 ft (10.7 m) thick. A normal vertical (bottom to top) and lateral sequence of facies is Shelf Siltstone, Interbar, Bar Margin, Central Bar, Shelf Siltstone (burrowed). Shelf Silty Shales (bedded and burrowed) surround the bar complex. In general, the outcrop section is sandier than several of the bar complexes that produce in the subsurface about 35 mi (56.3 km) northeast of the o tcrop. Two new subfacies are introduced, the Interbar (sandy) Facies and the Bar Margin (interbedded trough and ripple) Facies.

The mean direction of transport in the trough-bedded Central Bar and Bar Margin Facies in south-southwest, except locally in the top foot or two of the bar where westerly transport directions are observed. If the upper few feet are excluded, the spread of transport directions is commonly less than 45° for individual outcrops and for the area as a whole.

Foraminifera control indicates that the bar sands were deposited at middle-shelf depth. Ammonite zonation by Gill and Cobban provides detailed time stratigraphy and documents that the shoreline, at the time these bar complexes were deposited, was as far as 80 mi (129 km) to the west.

The Eagle sandstone delta complex of south-central Montana is a possible initial source for the sands. Nearly unidirectional currents, in part intensified by storms, are inferred to be the main process involved in deposition of the linear bar complexes.

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