STRATIGRAPHY AND STRUCTURE CASTLETON AREA VERMONT

egarded as eastern facies of the Potsdam-Little Falls seciuence adjacent
to the Adirondack Mountains. The three units of the standard Croixan
section, Dresbach, Franconia, and Trempealeau, appear to be represented
in Vermont by the Danby and Clarendon Springs dolomites.
There is no proof, however, that the oldest Potsdam and Danby beds
may not be pre-Dresbach in age.
Upper Cambrian sandstones near the Adirondacks are represented
eastward by sandy dolomites. Such progressive loss of sand with increasing
distance from the ancient land mass has been noted in the
Lower Cambrian and in some Ordovician beds. Cady (1945, passim)
has built up a general picture of an Adirondack source for most or all
of the sands in the strata of the Champlain Valley.
New light on the ages and correlations of post-Potsdam units in
Vermont may be shed by work now in progress in New York State
southeast of the Adirondacks.
Danby Formation
Name: From the towns of Danby and Wallingford, Vermont, Keith
(1932, p. 396) named two dolomitic formations of supposedly Lower
Cambrian age. Later (Cady, 1945, p. 535) the beds were reinterpreted
as Upper Cambrian, and the Wallingford was given the status of an
upper member of the expanded Danby formation.
Distribution: The Danby crops out in a narrow belt extending from
the boundary of the Castleton and Brandon quadrangles southward
through Florence and Proctor to the western slopes of Pine Hill. The
southern exposures of Danby cover an area extending from the boundary
of the quadrangle southwest of Chippenhook northward to the western
slope of Boardman Hill.
Description: Approximately the lower half of the Danby consists of
an alternation of white, medium- to coarse-grained quartzite in beds
10 to 15 inches thick and light-gray and cream-colored dolomite in beds
several feet thick. Some thicker quartzite ledges contain thin dolomite
seams. On weathered surfaces the quartzite beds stand out prominently
against brown, gray, or deeply iron-stained dolomites. A 10-foot coarse
intraformational conglomerate of dolomite and quartzite boulders is
exposed north of the Chippenhook cemetery.
The Wallingford member, which is the upper part of the Danby formation,
includes sandy dolomites displaying abundant cross-bedding, many
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