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Allen J. Dennis and Others
lel to the pole to a great circle of poles to folded foliations,
and are interpreted to represent west-vergent folding of
Alleghanian age.
Dennis and Shervais (1995) report whole-rock major
and trace element geochemistry from this series of outcrops
(their samples 2472, 2473a, b, 2474a, b). Dennis and Shervais
interpreted the protoliths of the rocks they analyzed
from this location to be high-Mg basalts (hornblende and
augite porphyries), basaltic andesites, and basalt.
Dallmeyer and others (1986) report a 40Ar/39Ar biotite
plateau age at 289±5 Ma from this site (their sample 45).
This mineral age is consistent with a hornblende plateau age
of 302±6 Ma (sample 46B) reported by Dallmeyer and others
(1986) 3 km north-northwest of here also on Dutchman
Creek (S- - 91 bridge, the same site where the 579±4 Ma
foliated diorite (Dennis and Wright, 1993, 1996) was collected).
Their sample 46A, also from that site, was a biotite
plateau at 313 Ma, older than that of the hornblende ands
interpreted by these authors as evidence of extraneous argon
contamination. Dallmeyer and others (1986) note that variations
in the 40 Ar/ 39 Ar plateau ages they report for Inner
Piedmont - Kings Mountain belt - Charlotte belt samples are
“not clearly related to any belt boundary, . . . and are tentatively
interpreted to indicate faulting or northwestward tilting
of isothermal surfaces between ca. 275 and 300 Ma.”
Based on the stops presented on this trip, it is suggested that
uplift related to northwest-vergent folding accompanied by
minor Alleghanian-age faulting in this segment of the central
Piedmont suture is responsible for the observed variation.
It is thought that the undeformed felsic dikes here are
related to the Buffalo gabbro, and are equivalent to those
observed at Stop 8. If the Buffalo gabbro belongs indeed to
the Siluro-Devonian array of gabbros, and these dikes are
related to the late stages of its intrusion, then it can be said
that there has been very little penetrative deformation in the
subsequent period. This observation and the proximity to
the central Piedmont suture was another line of evidence
that led Dennis (1995) to conclude that the primary, significant
motion on the central Piedmont suture predates ca. 400
Ma (see also Stop 1). Thus, his interpretation is that significant
motion on the central Piedmont suture in this area postdates
foliation formation (ca. 535 Ma) and predates intrusion
of post-metamorphic rocks ca. 400-380 Ma. Where the
strike of this fault is oriented northeast-southwest, to the
north and to the south (Kings Mountain shear zone and Middleton-Lowndesville
zone respectively), it is reactivated as
an Alleghanian, retrograde strike-slip shear zone, but in this
area Alleghanian effects are less dramatic. The advantage is
that we have a better opportunity to see what this boundary
looked like prior to the strong Alleghanian overprint
observed in areas to the north and south.
REFERENCES CITED
Charles, A.D., 1987, Narrative history of Union County, South
Carolina, Spartanburg: Reprint Company, 512 p.
Dallmeyer, R.D., Wright, J.E., Secor, D.T. and Snoke, A.W. , 1986,
Character of the Alleghanian orogeny in the southern Appalachians.
Part II. Geochronological constraints on the tectonothermal
evolution of the eastern Piedmont in South Carolina:
Geological Society of America Bulletin, v. 97, p. 1329-1344.
Dennis, A.J., 1988, Preliminary geology of the Glenn Springs-
Jonesville area and tectonic model with road log, in Secor, D.T.,
ed., Southeastern Geological Excursions: Columbia, SC: South
Carolina Geological Survey, p. 226-249.
Dennis, A.J., 1989, Tectonogenesis of an accreted terrane: The
Carolina arc in the Paleozoic: [Ph.D. thesis]: Columbia, University
of South Carolina, 139 p.
Dennis, A.J., 1991, Is the central Piedmont suture a low-angle normal
fault?: Geology, v. 19, p. 1081-1084.
Dennis, A.J., 1995, The Carolina terrane in northwestern South
Carolina: Relative timing of events and recent tectonic models,
in Hibbard, J.P., van Staal, C.R., and Cawood, P.A., eds., New
Perspectives in the Appalachian-Caledonian Orogen: Geological
Association of Canada Special Paper 41, in press.
Dennis, A.J. and Shervais, J.W., 1991, Evidence for arc rifting
along the Carolina terrane boundary in northwestern South
Carolina: Geology, v. 19, p. 226-229.
Dennis, A.J. and Shervais, J.W., 1992, Reply: Geology, v. 20, p.
473-475.
Dennis, A.J. and Shervais, J.W., 1995, The Carolina terrane in
northwestern South Carolina: Insights into the development of
an evolving island arc, in Nance, R.D. and Thompson, M.D.,
eds., Avalonian and related peri-Gondwanan terranes of the
Circum-North Atlantic: Geological Society of America Special
Paper 304, in press.
Dennis, A.J. and Wright, J.E., 1993, New Late Precambrian-Cambrian
U-Pb zircon ages for zoned intrusives in the western
Carolina terrane, Spartanburg and Union Counties, South Carolina
[abstract]: Geological Society of America Abstracts with
Programs, v. 25, p. 12.
Dennis, A.J. and Wright, J.E., 1995, Mississippian (ca. 326-323
Ma) U-Pb crystallization ages for two granitoids in Spartanburg
and Union Counties, South Carolina: South Carolina Geology,
v. 38, in press.
Dennis, A.J. and Wright, J.E., 1996, The Carolina terrane in northwestern
South Carolina, USA: Age of deformation and metamorphism
in an exotic arc: Tectonics, accepted pending
revision.
Garihan, J.M., Ranson, W.A., Sargent, K.A., and Niewendorp,
C.A., 1995, Geology of Masters' Kiln and history of the marble
occurrences in Laurens and Union Counties, South Carolina:
South Carolina Geology, v. 38, in press.
Glover, L., III and Sinha, A.K., 1973, The Virgilina deformation, a
Late Precambrian to Early Cambrian (?) orogenic event in the
central Piedmont of Virginia and North Carolina: American
Journal of Science, v. 273, p. 234-251.
Hibbard, J. and Samson, S.D., 1995, Orogenesis unrelated to
Iapetan cycle in the Southern Appalachians, in Hibbard, J.P.,
van Staal, C.R., and Cawood, P.A., eds., New Perspectives in
the Appalachian-Caledonian Orogen: Geological Association
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