4 Historical Perspectives: 250 Years of Geology in the Northeast

Sunday, 18 March 2012
8:00 AM - 10:00 AM
Ballroom B

CONTROVERSIES OVER OVERTHRUSTS IN THE PENNSYLVANIA PEIDMONT

Paper number: 4-2
Program: Theme Sessions
Time: 8:20 AM – 8:40 AM

Authors

Abstract

The concept of overthrust faulting involving crystalline rocks of the Pennsylvania Piedmont was introduced by the pioneering geologist Florence Bascom, and greatly extended by her students Anna Jonas (later Stose) and Eleanora Bliss (later Knopf), and by Jonas's colleague and eventual husband George Stose. Ironically, Bascom never accepted the interpretation in 1929 by Knopf and Jonas that the Martic Line marks a major overthrust.

Even more controversial was the suggestion made by Stose and Jonas in 1935 that the crystalline massifs of the Piedmont, in particular the Reading Prong, are allochthonous. This hypothesis, as well as that of the Martic Overthrust, was strongly opposed by Professor Benjamin Miller of Lehigh University. In the early 1940s, Ernst Cloos and Anna Hietanen of the Johns Hopkins University shed new light on the so-called "Martic controversy," without actually resolving it.

In recent decades, re-mapping and re-interpretation have made the concept of major overthrusts in this region much more acceptable, especially in light of the plate tectonics paradigm.