Full Title: Geology of the "Martic Overthrust" and the Glenarm Series in Pennsylvania and Maryland
Authors: Ernest Cloos and Anna Hietanen
From the original introduction: The age of the Glenarm series in general and the Wissahickon schist in particular has been under discussion for over 30 years, and in spite of much work done in the areas underlain by this series its age is still left in doubt. Some workers assign it to the pre-Cambrian because of lack of evidence to the contrary, and others hold it to be the equivalent of a metamorphic facies of the Ordovician Martinsburg shale. As an interpretation, the "Martic overthrust" has added a new element to the discussion. Obviously a good store of facts is needed on which all workers can agree and which should help all concerned. The problem involved is fundamental for the interpretation of width and depth of the Appalachian geosyncline, its deformation, the participation of the basement, and the role played by the intrusions. The area reaches roughly from New Jersey to Alabama and accompanies the Appalachians along their southeast side as a belt of "pre-Cambrian" crystalline rocks. This would leave the Appalachians without definite basement and also almost without accompanying intrusions found in other orogenic units like the Caledonians, Variscians, or the Alps. The authors are not particularly interested as to whether the Wissahickon schist is pre-Cambrian or Paleozoic or whether the Martic overthrust does or does not exist. They have tried an application of all modern structural and petrologic methods at their command in a controversial area in which detailed information is lacking, hoping that this may contribute to the analysis of the large complex of questionable age. As a rule a very careful and detailed study of a small region furnishes results more useful to others than the most brilliant generalizations based on insecure facts. Unfortunately, detailed work is time-consuming and not very inspiring, whereas the large picture is more spectacular and also more interesting. The authors have made an attempt to present the facts as free from bias as possible. The reader should bear in mind, however, that even field mapping under ideal conditions is not always objective, for exposures are never perfect. The authors hope that the evidence is sufficient to permit clarification of the problem. E. Cloos spent approximately 400 days in the field and as many in the laboratory in the preparation of petrofabric diagrams and other materials. Philip Guild worked two field seasons in Lancaster County and one winter in the laboratory. Anna Hietanen spent one winter on the thin sections and petrographic work investigating the rocks from Lancaster County, and one winter at Bryn Mawr analyzing the rocks of the easternmost area (Pt. III). Since A. Hietanen had to return to Finland and communication is slow and unreliable, E. Cloos is largely responsible for final form and corrections of the whole paper.
Published: 12/31/1941
ISBN Number: 9780813720357
Pages: 221
Product Category: EBooks
