English: Ripple marks are moderately common sedimentary structures in the rock record. They indicate the presence of a current at the time of sediment deposition. Asymmetrical ripples have a long side and a short side, as seen in cross-section. Symmetrical ripples are more or less evenly shaped in cross-section view. Asymmetrical ripples form in a one-direction current by wind or water. Symmetrical ripples for in a back-and-forth, two-direction current in very shallow water by wave action.

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From Diemer et al. (2012) - Building Stone Walking Tour of Uptown Charlotte:

The 1.5 acre urban pocket park known as the Green is located between the 400 block of South Tryon and South College Streets, immediately west of the Charlotte Convention Center. Designed by Wagner Murray Architects of Charlotte, it was completed in 2002 and sits directly on top of a 7-level underground parking structure.

Sandstone capping retaining walls

This fine-grained, plane-bedded sandstone, used throughout the Green as retaining wall caps, was quarried near Crossville, Tennessee. One of the capstones on the southern side of the plaza has ripple marks, others have parting lineation (the small ridges evidence on bedding planes where the stone has split). This stone was likely formed in a deltaic setting associated with an inland sea, as evidenced by its plant fossils.

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Provenance: "Tennessee Bluestone" from a quarry near Crossville, Cumberland County, east-central Tennessee, USA

Locality: capstone atop retaining wall at "The Green", College Street & 2nd Street, downtown Charlotte, North Carolina, USA