Abstract

Dake (1921) hypothesized that, prior to the mid-Silurian establishment of soil-binding land plants, wind must have been an important transport mode for sands and silts. Cotter (1978) has interpreted the absence of pre-mid-Silurian meandering fluvial deposits to be the result of the absence of soil-binding plants, which dictate a braided style for fluvial processes. A natural consequence of this is to assume that accumulation of pre-Silurian shelf sands may be, at least in part, the result of the offshore accumulation of wind-blown sand. Recent analogues, and the results of physical experiments, indicate that this mechanism could account for the entire accumulation of such a sandstone as the St. Peter in terms of rate of deposition. An analysis of the morphology of quartz grains (using Fourier and SEM techniques) from samples from the St. Peter Sandstone supports this conclusion.

Acceptance of such an origin for St. Peter-like blanket sandstone, resolves the apparent paradox of deposition of relatively thick sheet-like sands on a stable craton during marine transgression — a mode of deposit not observed on present-day stable continental shelves. An aeolian interpretation of St. Peterlike sandstones implicitly carries with it a prediction of the size and location of areal thickness variations: 1. the deposit should be thickest in the vicinity of the low-stand shoreline; 2. large local changes in thickness will be most pronounced near the highstand shoreline because of erosion/karstification of the unconformable substrate; and 3. the relation of shoreline orientation to prevailing wind direction should play a major role in producing intermediate-scale thickness variations.