STRATIGRAPHY AND STRUCTURE CASTLETON AREA VERMONT

in the Castleton area will be considered to be related to the Taconic
disturbance.
Joints
Joints are conspicuous in all sedimentary rocks except the marbles,
but no systematic orientation was discerned. The strikes of the joints
in this area box the compass, and the dips are predominantly steeper
than 45 degrees. No classification of the joints was attempted in this
study. Dale (1899, P. 210) and Larrabee (1940, p. 50) described joints in
parts of the Castleton quadrangle and adjoining areas.
Drag Folds and Flowage Folds
In dolomites and clastic rocks of this area drag folds and minor folds
on the flanks of the major folds are useful in determining the direction
of anticlinal crests and therefore in distinguishing normal from inverted
sequences. In drag folds the upper layers move upward toward anticlinal
crests relative to the lower layers. In competent successions and in competent
beds within incompetent marbles, drag folds have proved to be
trustworthy in interpreting major structure.
In plastic marble beds, however, flowage under great stress has produced
plications that Bain (1931) in a thorough study has called flowage
folds. In such folds the plastic marble has flowed toward the synclinal
troughs. Bain likened the movement to that of tar on a hot day flowing
away from the crown of a macadamized road. Flowage folds therefore
have an orientation opposite to that of drag folds. Consequently minor
folds in marble sequences must be interpreted with caution. Most of
them are true flowage folds, but some simulate drag folds. Some small
folds in the West Rutland marbles appear to be an indeterminate complex
of both varieties. Stratigraphic and faunal evidence are ordinarily
necessary in order to be certain of correct structural interpretation.
TIME OF DEFORMATION
In the Catskill quadrangle of New York "the Manlius limestone rests
with distinct angular unconformity on the Normanskill shale on the
western side of Becraft Mountain and on Schodack limestone on the
three other sides" (Ruedemann, 1942a, p. 124-127). Becraft Mountain
is a Siluro-Devonian outlier that unconformably overlies a thrust fault
which brought Schodack above Normanskill. This exposure proves that
the Taconic rocks of the Hudson Valley were deformed in pre-Upper
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