STRATIGRAPHY AND STRUCTURE CASTLETON AREA VERMONT

in Pittsford and at the Pittsford Valley quarries at the northern terminus
of the Clarendon and Pittsford Railroad. The Boardman is divided into
three members, the Sutherland Falls marble, the Intermediate dolomite,
and the Columbian marble. These divisions are used as defined by Bain
(1931), and their names are retained because of their economic importance
in the marble belt. Unfortunately suitable stratigraphic names
remaining in this area are not many as a result of generations of predatory
geologists. There can be no advantage in renaming these members
according to convention, and there could be some confusion.
Distribution: The Boardman formation crops out in a band that extends
from the northern to the southern boundary of the Castleton
quadrangle from Pittsford township through Proctor and Center Rutland
to Clarendon township.
Description: The three members of the Boardman are, in ascending
order: -
Sutherland Falls marble member: The lowest member of the Boardman
is a thin-bedded, green-streaked, white and cream-colored marble
with contorted chains of dolomite crystals standing out on weathered
surfaces. Dolomitization in the lower part is so complete that the rock
has the appearance of an angular breccia of marble cemented by frothy
white dolomite. A central siliceous band called the Hen Hawk layer is
found in quarrying (Bain, 1939, p. 10). The name of this member is
apparently taken from Sutherland Falls on the Otter Creek in Proctor,
although the rocks exposed at the falls belong to the Winooski dolomite.
The type locality is probably a quarry 2000 feet west of Sutherland Falls.
Intermediate dolomite member: The Intermediate dolomite is a
thick-bedded, rather porous, light-gray dolomite generally containing
some sandy beds and typical large quartz knots. Some patches of white
marble are enclosed in the dolomite. Bedding is usually difficult to see,
and the rather craggy exposures are in some contrast to the more
rounded forms developed on the upper and lower marbles.
Columbian marble member: The Columbian marble member is a
generally white-weathering white and blue-gray marble, the darker
zones of which are striped with gray parallel to bedding. Beds are rarely
less than 6 inches thick and are commonly thicker. Occasional threads
of green silicates wind irregularly through the brilliant white marble.
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