THE
NATIONAL GEOGRAPHIC MAGAZINE.
Vol. I.
1889.
No. 3.
THE RIVERS AND VALLEYS OF PENNSYLVANIA.[1]
By William Morris Davis.
"In Faltensystemen von sehr hohem Alter wurde die ursprüngliche Anordnung der Langenthäler durch das Ueberhandnehmen der transversalen Erosionsfurchen oft ganz und gar verwischt."
Löwl.Petermann's Mittheilungen, xxviii, 1882, 411.
CONTENTS.
Part first. Introductory.
- Plan of work here proposed.
- General description of the topography of Pennsylvania.
- The drainage of Pennsylvania.
- Previous studies of Appalachian drainage.
Part Second. Outline of the geological history of the region.
- Conditions of formation.
- Former extension of strata to the southeast.
- Cambro-Silurian and Permian deformations.
- Perm Triassic denudation.
- Newark deposition.
- Jurassic tilting.
- Jura-Cretaceous denudation.
- Tertiary elevation and denudation.
- Later changes of level.
- Illustrations of Pennsylvanian topography.
- ↑ The substance of this essay was presented to the Society in a lecture on February 8th, 1889, but since then it has been much expanded.
