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1). At the beginning of the Taconic Orogeny, during the early
Ordivician,
Laurentia was in the process of subducting beneath the Piedmont
Terrain.
2). As subduction continued, an accretionary wedge formed at the
subduction zone at the Laurentian Margin.
3). At approximately 460 Ma eclogitization
of the subducting slab occurred at depth in the subduction zone.
4). In the mid-Ordivician, the collision of Laurentia and the Peidmont Terrain
occurred.
5). During the late Ordivician, the Spruce Pine Thrust
Sheet was sutured to the Laurentian rocks of the
Pumpkin Patch Thrust Sheet by the Taconic Orogeny. The
suturing induced amphibolite facies metamorphism in the
Pumpkin Patch Thrust Sheet. The contact between the Spruce Pine Thrust
Sheet and the
Pumpkin Patch Thrust Sheet that contains this amphibolite
facies metamorphism is the strike slip dextral shear zone known as
the Burnsville Fault. The Burnsville Fault, possibly
re-activated during the Acadian Orogeny, records Siluro-Devonian
transpression. 6). During the
Alleghanian Orogeny, northwest thrusting transported the Spruce
Pine / Pumpkin Patch
Thrust Sheet over the Beech Mountain Thrust Sheet of
Laurentian origin. This thrusting induced greenschist facies
metamorphism in the Beech Mountain Thrust Sheet. (Stewart
et al., 1997b; Standard and trupe, 2000)
7). Approximately coeval with this thrusting, The Beech Mountain Thrust Sheet was thrust over the Pardee
Point Thrust Sheet along the Linville Fault. (Stewart et
al., 1997b)
8). Duplexing of all basement rocks
beneath the Grandfather Mountain Window caused subsequent
folding of all aforementioned thrust sheets. 9).
By 320-300 Ma the eclogites were brought to the surface.
10). Erosion removed the younger Paleozoic metasedimentary rocks, exposing the Grenville-age
basement rocks within the
Grandfather Mountain Window and the eclogites. |
