File:Geology of the Richmond Basin 1899 Plate XXXVII.jpg

English: Plate XXXVII from The Geology of the Richmond Basin published by USGS, which has the following caption:
Large ferruginous concretionary stains in light-colored sandstone, Tuckahoe.
The text of the report refers to the figure as follows:

Stratigraphy of the James River section.—The strata in the James River bluff, by far the longest natural section in the basin, are fairly well exposed in the old road passing by the ruined brick stable at Tuckaboe. At this place there is, below, a dark drab argillaceous sandstone, cut by ragged edged joints into irregular quadrangles (see Pl. XXXVI). Above this comes a coarse granitic sandstone of the arkose type, nearly white in color, but locally marked by gigantic spherical shells of iron-oxide stains surrounding a white center (see Pl. XXXVII). The light color of this stone appears to be the natural color of the granitic sandstones in this basin, as the deep boring at Midlothian goes to show. These iron stains appear to be effects of the weathering of the rocks and the oxidation of the iron which they contain. The concretionary arrangement of the stains shows clearly that the iron oxides have been distributed in this manner since the deposition of the rock. East of the station, in the first ravine on the west of Tuckahoe, Estheria shales crop out in a bed, which is probably between the drab beds and the coarse sandstones above noted. At a few points the thick-bedded sandstones have been quarried to a limited extent.

Later the report states:

The weathered sandstones on the south bank of the James River, as for instance along the private road northward from Moss's store, are marked by concentric bands of iron oxides simulating alternating bands of differently colored layers of sandstone on so large a scale and so closely as to make it difficult to distinguish this secondary banding from the original stratification. Some large concretions of this character occur at about the same horizon in the sandstones on the north bank of the river at Tuckahoe (see Pl. XXXVII).