STRATIGRAPHY AND STRUCTURE CASTLETON AREA VERMONT

York and Vermont Dale (1899, P. 191-192) regarded the Berkshire
schist of the Taconic Range in the Castleton area and adjacent quadrangles
as equivalent to the entire Ordovician argillaceous sequence as
exposed in the slate belt. In 1912 Dale assigned the Berkshire to the
Trenton and younger Ordovician. In mapping the western part of Massachusetts
Emerson (1917, p. 39 and map) followed Dale's usage by showing
the Berkshire as lying stratigraphically above the Cambro-Ordovician
Stockbridge limestone. Later work in the Taconic quadrangle of Massachusetts,
Vermont, and New York (Prindle and Knopf, 1932) made it
clear that Dale's Berkshire schist includes rocks of Cambrian age in
addition to Ordovician strata. Where correlations were possible in the
Taconic quadrangle the Berkshire was subdivided into the several
Cambrian and Ordovician formations described by Dale in the slate
belt (1899) and in Rensselaer County, New York (1904a) and in part
renamed in the Saratoga Springs report (Cushing and Ruedemann,
1914, p. 69-70); namely, Bomoseen, Mettawee, Schodack, etc. The
remainder of the Berkshire schist in the Taconic quadrangle was regarded
partly as the metamorphosed equivalents of these same Cambrian
and Ordovician formations, and the Cambrian parts thereof were directly
correlated with the Hoosac-Rowe sequence typically exposed in the
Hoosac Range of western Massachusetts. Some of Dale's Berkshire,
however, lies stratigraphically above the Valley carbonates in the
Taconic quadrangle, and such rocks were named the Walloomsac slate
(Prindle and Knopf, 1932, p. 274-275). In this way the name Berkshire
schist was entirely eliminated in the Taconic quadrangle.
It is the view of the United States Geological Survey (Wilmarth,
1938) that the name Berkshire schist is a valid general term to designate
rocks of probable Cambrian and Ordovician age that are present in the
Taconic Range. The Survey anticipates that with further work the
Berkshire terrane will be subdivided into other named units, as was
begun in the Taconic quadrangle. Pursuant to this, Larrabee(1939-1940)
mapped the Berkshire schist of the Castleton area as Rowe schist,
thereby implying a Cambrian age. Kaiser (1945) was able to subdivide
the Berkshire at the northern end of the Taconic Range into the Cambrian
Mettawee and Schodack formations.
During the present investigation the Hortonville slate and some of
the phyllites of the Mendon series were removed from the Berkshire
schist, where Dale had placed them. The remainder of the Berkshire
schist of Dale belongs to the Taconic Allochthone, and for reasons given
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