The Calico Bluff Formation (Carboniferous) is an interbedded limestone and shale unit which is exposed along the Yukon River in east-central Alaska. A prograding submarine-fan model explains the observed lithofacies succession and sedimentary structures.

The rocks of the Calico Bluff Formation are subdivided into five lithofacies: (1) coarse-grained bioclastic limestone, (2) fine-grained bioclastic limestone, (3) platy micritic limestone, (4) calcareous shale, and (5) siliceous shale. Shallow-water fauna in the bioclastic limestones contrast with deep-water goniatites, straight cephalopods, and brachiopods found in the platy micritic limestone and calcareous shale. Sedimentary structures include graded bedding, sole marks, Bouma sequences, and soft-sediment deformation.

Depositional processes of the Calico Bluff Formation range from basinal pelagic sedimentation to sediment gravity flows. Both proximal and distal turbidites are recognized. Distal turbidites represent deposition in a lower-fan environment, whereas proximal turbidites are deposited in a mid-fan environment. Several thickening and coarsening upward cycles are recognized in outcrop. Individual cycles may represent shifting suprafan depositional lobes. Paleocurrent measurements indicate direction of transport to the south-southeast.

Micritic beds are probably calcareous pelagic oozes that have been transported downslope by turbidity currents and deposited in the basin. Calico Bluff Formation shales were deposited by suspension and weak suspension currents.

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