Brown iron-staining on coarse shelf sands has been taken as evidence of subaerial weathering, either in the source area or at the depositional site. However, we note that iron-staining can occur subaqueously, as well. We have found a close correlation between grain size and color on the inner Virginia shelf, with finer sands being olive-gray, and coarser sands being brown. We suggest that the sand-grain surfaces are in chemical equilibrium with their environment. The coarser sands are permeable, and are kept oxygenated by wave surge. The finer sands are relatively inpermeable, and are reduced by interstitial organic matter. While in any given case, brown iron-staining may have occurred sub-aerially, it may also have occurred in the modern marine environment. Hence brown iron-staining is not a definitive criteria for a relict origin or subaerial exposure of shelf sand.

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