STRATIGRAPHY AND STRUCTURE CASTLETON AREA VERMONT

Age: The Bomoseen of this vicinity contains only worm trails and
algal impressions. In the Taconic quadrangle of southern Vermont,
New York, and Massachusetts rocks approximately equivalent to the
Bomoseen grit (Prindle and Knopf, 1932, p. 276) contain a numerous
fauna, chiefly trilobites and brachiopods of Lower Cambrian age.
Mettawee Slate
Name: The Cambrian roofing slates, division B of Dale's slate belt
rocks (1899, p. 178), renamed but otherwise unchanged by Cushing and
Ruedemann (1914, p. 69), are called the Mettawee slate. The type area
is the slate belt from Granville, New York to Fairhaven, Vermont, which
is in part drained by the Mettawee River.
Distribution: The Mettawee slate is a widespread formation in the
western part of the Castleton quadrangle. Several bands of Mettawee
crop out in Poultney, Castleton, and Hubbardton townships. In the
southern half of the quadrangle the Mettawee is confined to the slate
belt and does not crop out in the Taconic Range. Kaiser (1945) has
mapped large areas of Mettawee in the Taconic Range north of the
Castleton River. It is probable that the rock here mapped as Nassau
contains some undifferentiated Mettawee.
Description: Typically the Mettawee is a soft, light-apple-green and
purple slate. The purple color seems generally to be confined to the
central part of the formation. The colors of the slate have no particular
relation to bedding or later fractures. In some places one color replaces
the other within the same bed. Bedding is shown only by 2-inch to 2-foot
green quartzites that are interbedded with the slate. Chlorite and some
calcite fill interstices in the quartzites, and tiny limonite speckles are
found. The tops of quartzite beds are usually covered with thin films of
dark green chlorite in which are vague traces of algae or worm trails.
The uppermost Mettawee slate is greenish-gray and may represent a
sedimentary transition toward the black slate of the overlying Schodack.
All slates with a green hue have been mapped with the Mettawee.
In a few places at the top of the Mettawee 10- to 15-foot thicknesses
of limestone conglomerate crop out in the green slate. The boulders of
blue-gray, compact limestone average 6 to 8 inches in their long dimension
and have been fractured, recrystallized in veins, and probably
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