STRATIGRAPHY AND STRUCTURE CASTLETON AREA VERMONT

ORDOVICIAN SYSTEM
For many years the standard Ordovician succession in the Taconic
sequence was considered to include the Bald Mountain limestone,
Ryesdorph conglomerate, Tackawasick limestone, and Snake Hill shale
(Ruedemann, 1942, P. 136). It is now the view of Kay (1937, P. 272-277)
and others that these units belong rather to the Valley sequence, lying
beneath the Taconic overthnist. The Ordovician Taconic sequence in the
Hudson Valley now includes, in ascending order, the Schaghticoke
shale, Deepkill shale, and Normanskill formation.
In the Castleton area Normanskill beds are certainly exposed, but
the presence of Schaghticoke and Deepkill is problematical. Dale's
division F of the slate belt section is probably equivalent to the Deepkill
and includes 35 feet of "very thin-bedded limestone and gray or black
shales. Possibly intermittent" (1899, opp. p. 178). The Schaghticoke
and Deepkill are of Canadian age, although the Deepkill may extend
upward into the Chazy. No fossils from the Ordovician of the present
area have been found. Consequently, although some Canadian strata
may crop out in this area, all rocks above the Cambrian are mapped as
Normanskill.
NormansJU Formation
Name: The famous graptolite shales exposed along the Normans Kill,
a tributary entering the Hudson River at Kenwood just south of Albany,
were called the Normanskill shale by Ruedemann (1901, p. 568). These
strata previously had been part of the Hudson River group. Because of
the presence of grit and chert in addition to shale, the unit has since
been called the Normanskill formation (Ruedemann, 1942, p. 88), and
two members were recognized in the Hudson Valley.
Distribution: A narrow band of Normanskill south of Hampton, New
York, crops out in the southwestern corner of the Castleton quadrangle.
A 3.5-mile band of Normanskill passes northward through the town of
Poultney, and a 6-mile parallel band passes through East Poultney. A
narrow 3-mile belt of Normanskill two miles west of Lake Bomoseen and
an oval outcrop slightly east of Beebe Pond are shown by Kaiser (1945,
P1. 1) north of the Castleton River. At the southern border of the Castleton
quadrangle in the township of Middletown a large mass of probable
Normanskill is mapped.
Description: Heterogeneity is the distinguishing mark of the Norman-
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