STRATIGRAPHY AND STRUCTURE CASTLETON AREA VERMONT

Much of the Castleton area is occupied by a small part of the Tacoruc
Range, which lies in east-central New York and adjacent parts of
Vermont and Massachusetts. Nearly forty years ago Arthur Keith
concluded that the Cambro-Ordovician rocks of the Taconic Range in
Vermont are a klippe or thrust outlier composed of an argillaceous facies
that had been thrust westward over a carbonate facies of similar age.
Although this concept has found general acceptance among geologists
working in the area, the roots of the overthrust have not been found.
Moreover, modern detailed stratigraphic and structural studies have
not been made in much of the Taconic region. The Castleton area was
chosen in order to ascertain the validity of the concept of a large Taconic
overthrust.
Originally this study was confined to the rocks of the Taconic sequence,
but it became evident that a clear picture of the relation between the
Taconic sequence and the rocks of the marble belt bordering the Taconic
Range on the east required remapping of the part of the marble belt
that lies in the Castleton quadrangle. This investigation, therefore, has
carried the mapping of the Champlain and Vermont Valleys (Cady,
1945) to the southern border of the Castleton quadrangle. Folding,
faulting, and metamorphism of the rocks have made accurate stratigraphic
work difficult. Identifiable fossils are rare, and the thickness of
several formations is obscure.
The area was mapped by the pace-and-compass method aided by
Paulin altimeter and aerial photographs. Data were plotted on photostatic
copies of the Castleton and Proctor sheets of the United States
Geological Survey enlarged to a scale of three inches to the mile. Twentyseven
weeks were spent in field work during the summers of 1947 and
1948.
Achnowledgments
Professor Marland P. Billings directed this work and spent nearly
two weeks with me in the field. I acknowledge with gratitude his aid
in solving many problems. Professors E. S. Larsen, Jr. and P. E. Ray -
mond have both given advice. Dr. Wallace M. Cady helped me both on
details and in understanding the areal picture. Professor Charles G.
Doll, State Geologist of Vermont, arranged for financial aid during the
field season of 1948.
Several geologists working in Vermont provided useful suggestions.
Chief among these are: J. L. Rosenfeld, J. B. Thompson, P. H. Chang,