 The region during the early Paleozoic lay off the coast of the southern portion of Laurentia, in what is now the southern United States.Laurentia straddled the equator at the time and the Rheic Ocean was to the south of Laurentia.Through the Ordovician, Silurian, Devonian, and early Carboniferous, marine sedimentation left extensive deposits of black shale, quartzose sandstone, and chert beds.