Palinspastic Maps of Central Appalachians

ABSTRACT A map showing pre-deformation sites of various Appalachian outcrops is extremely useful in reconstructing paleogeographic relations and other matters. This paper presents two such palinspastic maps for the central Appalachians; although constructed by different methods, these maps are remarkably similar. Both maps suggest approximately 40 per cent or more of foreshortening during the final deformation of the Ridge and Valley region, and indicate that to restore any point to its pre-folding position, one must transpose it east and south by a distance that may range between 25 and 65 miles. This means, in a general way, that an Appalachian trend which now strikes N-S was originally positioned NW-SE, and that many trends now striking NE-SW had an original direction nearly N-S. Both advantages and disadvantages of using the palinspastic base are considered. The Appalachian geologist is urged to plot some of his critical data on a map of this kind to determine whether or not it may reveal features unnoticed when the data are studied on a normal map. He is finally reminded that a map on a present-day geographic base, even though it be familiar and presently correct, is really the one that has been distorted from the frame of geographic reference prior to regional deformation.