STRATIGRAPHY AND STRUCTURE CASTLETON AREA VERMONT

westward so as to overlie the strata of the Champlain Valley. A correlation
of the Taconic formations with other rock units of this region is
given in Plate I.
LOWER CAMBRIAN SERIES
Two incompatible Lower Cambrian successions have been set up in
parts of the Castleton quadrangle. The sequence proposed by Dale
(1899) and Ruedemann (Cushing and Ruedemann, 1914) was followed
in recent years by Larrabee (1939-1940) and by Kaiser (1945). The
TABLE 2
Correlation Formation Thickness
(in feet)
Black River-Trenton (?) Normanskill formation 1250 ±
-- - - - - - U N C 0 N F 0 R M I T Y - - - - - - - - - - -
Zion Hill quartzite 0-70
Schodack formation 0-250
Eddy Hill grit 0-30
Lower Cambrian Mettawee slate 100-300
Bomoseen grit 200+
Nassau formation, including 1000-2000
Bird Mountain grit 0-500
succession followed by Keith (1932) and Swinnerton (1922) was applied
only at the northern end of the Taconic Range. Kaiser rejected Keith's
stratigraphic succession completely, and Kaiser's opinion is accepted
in this report.
Nassau Formation
Name: Cushing and Ruedemann applied the name Nassau beds to a
series of alternating red and green shales and quartzites that underlie
the Bomoseen grit in the town of Nassau, New York. These rocks make
up Divisions A-E of Dale's (1904a, p. 29) series in Rensselaer County,
New York. In the Castleton area the rocks herein mapped as Nassau
were referred by Dale (1899) to the Berkshire schist. A treatment of the
problem of correlating these rocks requires a discussion of the Berkshire
schist.
Dale (1891, p. 8) first named the Berkshire for its prevalence throughout
Berkshire County, Massachusetts. Two years later (1893, p. 303-
306) he further described the Berkshire in the Taconic Range and
Rensselaer Plateau of New York. In his report on the slate belt of New
38