STRATIGRAPHY AND STRUCTURE CASTLETON AREA VERMONT

such a discordance at various places in and bordering the central and southern
Taconics. This would suggest that most of the Taconic Allochthone pseudo-conformably
overlies Canajoharie equivalents, making it somewhat doubtful that the
discordance noted at the north end of the Taconic Range, although at a point where
a thrust fault might be expected, is other than a conformable overlap of the Canajoharie
rocks on older truncated strata.
"A stratigraphic break beneath the Canajoharie is well established at several
localities northwest of the Taconic Range. The Canajoharie lies on Beekmantown
within a small area at the Orwell-Benson line near Lake Champlain and adjacent to
the Adirondack border. Similar breaks have been noted near or at the base of the
Canajoharie or its equivalents at several localities at (Clark and McGerrigle, 1936,
p. 672-673; Kay, 1937, p. 264, 275-276) or east (Ruedemann, 1901, p. 546-549; 1930,
p. 104-113; Kay, 1937, p. 276-277) of the meridian of the Adirondack Mountains.
At the Adirondacks the Canajoharie shale gradationally overlaps northwestward
upon the Denmark limestone member of the Sherman Fall formation—the nonclastic
equivalent of the Canajoharie in northwestern New York (Kay, 1937, p.
267-268, P1. 4). This break may be present also to the east of the Green Mountains
(Currier and Jahns, 1941, p. 1510)."
This investigation confirms Cady's conclusions. From the pattern
of the unconformity it appears that folding increased in intensity southward
and eastward. This mild episode of orogeny seems to have been
connected genetically with the great flood of clastics that make up the
Canajoharie and Martinsburg formations. Kay visualized the rising of a
land mass Vermontia during the later Ordovician located in the vicinity
of the present Connecticut Valley (1937, p. 291). Vermontia was the
source of the muds that in the middle Trenton covered the limestones
of the Castleton area. Probably the orogenic movements that culminated
in the Vermontian Disturbance in Trenton time affected the rocks of
the Champlain Valley with increasing strength eastward from the
Adirondack land mass.
TACOMC SEQUENCE
GENERAL
The rocks of the Taconic sequence are divided into the following
units in the Castleton area (Table 2).
The argillaceous Taconic rocks have a composite thickness of 3000-
4000 feet. These strata are contrasted strongly in lithology with the
adjacent rocks of the same age in the Champlain-Vermont Valley. Under
the hypothesis adopted here they were deposited in a trough east of the
carbonates of the Champlain Valley and were subsequently thrust
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