This image illustrates part of the geological map of Highland County, Virginia in the Valley & Ridge province. Note the linear belts Paleozoic sedimentary rocks that are repeated by folding. From oldest to youngest these include O1 = lower Ordovician strata, O2 = upper Ordovician strata, S1 = Silurian strata, SD = Silurian-Devonian strata, D1 = lower Devonian strata, and D2 = middle and upper Devonian strata. The red blobs are igneous intrusions (primarily basalt and andesite) that formed 35 to 55 Ma, and are Virginia’s youngest igneous rocks.
