The Dakota Formation provides excellent exposures of cyclically deposited fluvial channel sandstones. Each successive channel sequence represents a cycle that commonly decreases in thickness upward. A general fining-upward sequence is typical within each cycle. Rarely, however, are cycles topped with material smaller than very fine-grained sandstone. Outcrops of the cyclic deposits range in thickness from 65 to 115 ft.

The base of each cycle is the basal erosional surface of each channel. The basal sandstones contain the coarsest sediment, which ranges in size from medium grain sand to pebbles. Boulder size fragments of bank material are commonly incorporated in the basal sandstone. Sorting is very poor to moderate. Almost all basal sandstones are nonresistant to erosion and moderate to dark reddish-brown in color. Sandstones above the basal unit are well to very well sorted and range in color from light brown to white.

The cementing agent of the sandstone is mainly clay, which apparently is kaolinite altered from potassium feldspar. Only minor amounts of calcite and silica cement are present. Virtually all samples contain various amounts of subangular to subrounded, frosted quartz grains.

Sedimentary structures are primarily trough and planar cross-stratification and parallel stratification. Thicker cycles commonly have medium- and small-scale trough and planar cross-stratification overlain by parallel stratification. Thinner cycles may contain exclusively trough and/or planar cross-stratification. Ripple marks are uncommon, but where present are situated at or near the top of cycles.

Most cycles probably were deposited in sinuous streams. Thicker sections of the Dakota apparently were deposited in streams of higher sinuosity than thinner sections.

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