Shelf and shoreface sequences form the lowermost sandstone deposits and the leading edge of a progradational deltaic wedge (Upper Cretaceous Ferron Sandstone Member of the Mancos Shale, Central Utah). Cores taken by ARCO Oil and Gas Company penetrated these shelf and shoreface sequences about a mile from their outcrop in Castle Valley, Utah. Outcrop evidence suggests that the shelf sandstone/-siltstone unit underlying the Ferron Delta complex is the distal part of a shelf sand body originating from another delta complex at least 50 mi to the north. Possible amalgamated shelf sand deposits have been recognized at the base of a shoreface sequence in one core. The Ferron cores offer excellent opportunities to examine wire-line log and core recognition criteria for shelf sandstone sequences in association with deltaic settings. Shelf sands associated with delta systems have been shown to be important hydrocarbon exploration targets.

Ferron Delta progradational facies consist of two main assemblages: bioturbated shelf siltstones and sandstones underlying the delta proper, and upward-coarsening delta front sandstones. The bioturbated shelf facies consist of several lithofacies which include laminated mudstone, rippled and burrowed siltstone, and bioturbated sandy siltstone. Component lithofacies of the upward-coarsening sandstone interval are rippled sandy siltstone, interbedded sandstone and siltstone, horizontally bedded sandstone, and cross-bedded sandstone.