Similar assemblages of sedimentary structures may be produced in two different environments if similar depositional processes are active in both environments. A study of some non-marine Carboniferous rocks in southeastern Massachusetts seems to support this conclusion.

Several sections of the Pennsylvanian Wamsutta Formation comprise alternations (cycles) of coarse- and fine-grade beds. Most of the alternating cycles represent vertical accretion, over-bank, flood-plain deposits. Many of the beds are graded graywacke which displays sole markings. The grading may be repetitive. These properties generally are thought to be typical of turbidites and deep-water flysch, and of eugeosynclinal deposits. These sedimentary types have been discussed at length in the recent literature, as have other features, including horizontal, ripple-drift, and convolute lamination, and intraformational conglomerate associated with graded sandstone. However, well-developed mudcracks interbedded in sandstones indicate that the normal depositional environment was a sub-aerial one which became periodically submerged and then exposed. The top stratum probably was subjected to these floods on a seasonal or annual basis. The typical sedimentation unit rests on an erosion surface, cuts into the underlying bed, and grades upward from conglomerate or sandstone at the base to massive siltstone at the top. Each sedimentation unit represents an episode of flooding on the flood plain, on levees adjacent to sinuous channels, and in crevasse splays and low-lying areas.

Flood and turbidity currents have much in common: (a) flows may appear suddenly in a foreign environment; (b) flows are characterized by high discharge, velocity, turbulence, and load; (c) the sediment load comprises a wide range of size grades; (d) currents are able to erode the bottom and remove scoured material; and (e) the sediment load is released progressively as the intensity of the flow decreases away from the source. The resulting beds are graded vertically and laterally. Similar depositional processes active in environments as different from each other as flood plains and marine slopes and basins can produce similar assemblages of sedimentary structures.

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