STRATIGRAPHY AND STRUCTURE CASTLETON AREA VERMONT

dules, and it weathers with a thin white crust. Its essential minerals are: barkevekite,
titaniferous augite, and zoned plagioclase near labradorite. These minerals
are partially altered to chlorite and probably sericite. Accessory magnetite
and ilmenite and secondary dolomite (?) and analcite are present in small
quantities.
2. Diabase in a dike 4 to 5 feet wide. Chilled for 4 or 5 inches from contacts and
very coarse-grained in interior. Traced 110 feet. Attitude: N 55° W, 80° S.
Location: 1000 feet northwest of B. M. 418 near Gorham Bridge, Proctor.
Country rock: Danby formation. This rock is a fine- to coarse-grained graygreen
rock bearing 3-mm. octahedra of magnetite and weathering with a light
brown crust. Ophitic texture is well displayed. Besides primary and secondary
magnetite it contains essential andesine-labradorite in laths and essential
interstitial pyroxene. Both the plagioclase and the pyroxene are greatly altered,
with the production of abundant sericite and chlorite.
3. Unidentified rock in a dike 15 feet wide with a 6-inch offshoot. Traced 30 feet.
Attitude: N 20 1 E, 80° W. Location: 200 feet west of bridge at Pittsford Mills
in the bed of Furnace Brook. Country rock:Dunham dolomite.
4. Unidentified rock in a dike 3 feet wide. Attitude N 70 ° E. Location: 600 feet
north of B. M. 661 on road near Butler Pond, Pittsford township. Country
rock: a klippe of Taconic rocks lying on Hortonville slate.
Age and Origin
None of the dikes were affected by orogeny, and all follow undeforrned
joints. The Post-Cambrian camptonites of the Champlain region, according
to Hudson (1931), are the youngest of the dikes and were
emplaced considerably later than the Taconic orogeny. Their alkalic
affinities suggest a correlation with the Monteregian intrusives, which
may be correlated with the White Mountain magma series. Billings
(1945, p. 43) has stated that the White Mountain magma series is
distinctly younger than the Acadian disturbance and is probably
Mississippian. The country rocks of the dikes were relatively cool before
the intrusion, for most of the dikes show chilled borders. Hence if any
Acadian deformation or thermal metamorphism affected the rocks in
the present area, it had run its course by Mississippian time.
STRUCTURAL GEOLOGY
MAJOR FEATURES
Genera! Setting
The Champlain-Vermont Valley is bounded on the east by the Green
Mountain anticlinorium, which in the latitude of Rutland trends north.
In the northern part of Vermont the Green Mountain anticlinorium
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