The Hinesburg Thrust Fault is
exposed in its type locality in
Mechanicsville,
Vermont,
just
northeast of Hinesburg, Vermont.
Late Proterozoic to Lower Cambrian
(~540-560 million years old) Fairfield
Pond Phyllite and Cheshire Quartzite
rocks
are
thrust
westward
approximately 6.4 km (~4 mi.) over
the younger, Lower Ordovician (~500
million years old) Bascom Formation
limestones and dolostones (Stanley et
al, 1999). Slivers of the dark Brownell
Mountain Phyllite are also present
along the fault trace (Stanley et al,
1987).
The Hinesburg Thrust Fault is the
major structural boundary in northern
and central Vermont separating the
older, highly metamorphosed rift-drift
sequence Taconian “hinterland” rocks
to the east (phyllites and argillaceous
quartzite here) and the younger,
carbonate-siliciclastic rocks of the
platform “foreland” to the west
(limestones and dolostones here)
(Figure 1: ??, 1972? ; Figure 2: Doll et
al, 1961). The phyllites and quartzites
form the cliffs at the Mechanicsville
site, while the lower plate carbonates
are poorly exposed.
Interesting fault-related structures in
the cliffs include: deformed fractures,
isoclinal folds, shear bands, mylonitic
textures, slickenlines, pressure fringes
around pyrites and “Z”shaped
quartz veins.
References:
Doll, C.G., W. Cady, J.B. Thompson, Jr., and M.P.
Billings, 1961. Centennial geologic map of Vermont,
State of Vermont.
Stanley, R.S., K. Leonard, and B. Strehle, 1987. A
transect through the foreland and transitional zone
of Western Vermont; in Westerman, D., ed., NEIGC
79th Annual Mtg. Guidebook—1987, Vol. 2, p. 80-108.
Stanley, R.S., T. Rushmer, C. Holyoke, and A. Lini,
1999. Faults and fluids in the Vermont foreland and
hinterland in Western Vermont; in Wright, S.F., ed.,
NEIGC 91st Annual Mtg. Guidebook—1999, p. 135158.
Stanley, R.S., and B. Strehle, ????. VGS Report.
For information about other geological teaching
outcrops in Vermont, please contact the
Perkins Geology Museum
Perkins Hall
University of Vermont
Burlington, VT 05405-0122
(802) 656-8694
HINESBURG
THRUST
FAULT
Mechanicsville,
Vermont
Insert photo here
Rolfe Seaton Stanley
Teaching Outcrop
UVM Geology Professor, 1964-2000