CompuServe Messages

<<The Atlantic closed (with continental collision) first, then opened, as it continues to do today. The collision occurred during Devonian time, creating the mountains of the eastern US. The Atlantic started opening up again in Triassic time.>> Agreed with most of your post, but I understood the collision BEGAN at this time or a little earlier and progressed southward. Or else a brief mountain building event in the early Devonian in what is presently New England was followed by a longer, more involved event sometime later in the areas to the south. Most of the Devonian layers in PA and NY are sediments from an earlier uplift. These Devonian beds, and subsequent Mississippian and Pennsylvanian deposits are involved in the folds of the Appalachian Range from NE PA southward, indicating that at least this portion of the Appalachians went up no earlier than the late Pennsylvanian. Also I think I recall that the shallow Permian basin in SW PA lies conformably on top of the Pennsylvanian, which would mean the bulk of the continental collision occurred even later, in the early Permian. Am I way off base here? ed–