STRATIGRAPHY AND STRUCTURE CASTLETON AREA VERMONT

VALLEY SEQUENCE
GENERAL
The rocks of the Castleton area are preponderantly of sedimentary
origin, somewhat altered by later metamorphism. Two distinct sequences
of sedimentary rocks are represented. The Champlain Valley (Autochthonous,
"In-place") sequence includes basal clastics, carbonate rocks,
and an upper shale. The Taconic (Allochthonous, "Transported")
sequence is dominantly argillaceous. Each sequence spans roughly the
same period of time. Figure 2 shows composite columnar sections of
both sequences.
The rocks of the Champlain Valley or, more simply, the Valley sequence
are divided in the Castleton area into the units shown in Table 1.
TABLE 1
Correlation Formation Thickness
(in feet)
Trenton Hortonville slate 1000+
Whipple marble 50-250
-- - - - - - - - U N C 0 N F 0 R M I T Y - - - - - - - - - -
Trenton (& Black River ?) Orwell limestone 0-50+
DISCONFORMITY?
Middlebury limestone 0-60
Chazy Beldens formation 0-200
Burchards limestone 0-150 (?)
DISCONFORMITY?
Bascom formation 0-500 (?)
Boardman formation
Canadian Columbian marble member 450-600
Intermediate dolomite member 190-2 50
Sutherland Falls marble member 90-100
Upper Cambrian Clarendon Springs dolomite 130-175
Danby formation 700 ±
DISCONFORMITY?
Winooski dolomite 1050-1200
Lower Cambrian Monkton quartzite 0-250
Dunham dolomite 1500-3000
Cheshire quartzite 400+
UNCONFORMITY?
Lower Cambrian or Mendon series 2 000+
Pre-Cambrian
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