1313

Produced byDonald R. Privett, Ph.D.- P.G.

Environmental and Engineering Geologist

Lower Catawba River Valley ofSouthern Chester and Lancaster

Counties, S.C. - Geology -Archeology and History

Part 2

23

Single tors, tor clusters and tor fields are

common in the Great Falls Metagranite

especially along the steeper slopes along

drainage draws and along the slopes of most

creeks flowing into the Catawba River.

33How tors form.How tors form.

43Large tor showing

exfoliation and jointing.

53Tor cluster on steep slope that has collapsed.

63

In the past one million years (Pleistocene) a series of ice sheets covered northern North America. Ocean volume was reduced - sea levels dropped more than 300 feet during some glacial epochs. Reduced sea level provided a steeper river gradient - down cutting was much greater. During interglacial epochs sea levels rose reducing gradients - slowing river downcutting. Sea level fluctuations resulted in greater erosion and down cutting, removed saprolite along steep slopes exposing widespread single and multiple corestones

73

Tors on the divides are embedded in saprolite, upper tors collapsed onto the lower ones in the larger fields.Cascades, rapids and falls formed at several locations where tor fields and large near surface bedrock exposures were exhumed.

The Great Falls Of The Catawba dropped about 35 meters, the river about 54 meters in a distance of 13 kilometers.

83

Topographic map of area river diverted below Fishing Creek

Dam.

93Aerial photograph 2004 contour interval = 2 feetAerial photograph 2004 contour interval = 2 feet

Cont. at Cont. at rightright

Cont. at Cont. at rightright

103

South end of long South end of long bypass.bypass.

South end of long South end of long bypass.bypass.

113

Erosion and Weathering During Pleistocene River Entrenchment Exposed Numerous Tors (Boulders).

123

The Exposed The Exposed Nitrolee Riverbed Riverbed

Exfoliated Granite Exposed in Middle of River Bed, Facing Southeast. Exfoliated Granite Exposed in Middle of River Bed, Facing Southeast.

133

Exfoliation in Granite, Rounded by Water Flow.Exfoliation in Granite, Rounded by Water Flow.Exfoliation in Granite, Rounded by Water Flow.Exfoliation in Granite, Rounded by Water Flow.

River Bed Looking North.

153Exfoliation dome.

163Exfoliation dome.Exfoliation dome.

173

Looking south.

183

Granite Pavement in Middle of Exposed River Bed.

19312/22/2008 433

Typicalexposure,MountainIsland in

Back.

203

Round granite Round granite boulder that boulder that rolled from rolled from

steep slope into steep slope into the river.the river.

Round granite Round granite boulder that boulder that rolled from rolled from

steep slope into steep slope into the river.the river.

213Very large tor perched on cliff.

223

Tor, Possibly Rolled Onto Rock Pavement.

Large pavement outcrop.

233

Two large round tors that may have rolled from steep slope into the main channel note base altered by water

flow.

243

Excellent pedestal rock in main river channel Nitrolee riverbed.

253Large pedestal undercut by water flow.Large pedestal undercut by water flow.Large pedestal undercut by water flow.Large pedestal undercut by water flow.

263 Anvil rock - a pedestal rock undercut by flowing

waters.

273

Details of layered metaDetails of layered metagranitegranite texture texture

on a water on a water polishedpolished surface. surface.

283

Metagranite (light) and Metagranite (light) and metadiorite?metadiorite?

293

Weathered sheared metagranite, off Brooklyn Weathered sheared metagranite, off Brooklyn Road.Road.

303

Granular texture in an altered metagranite.

313

Mafic dikes have been intruded into the granite, they contain minerals that are more water

soluble, therefore, are weathered more relative to the

metagranite.

323

A dike intruded into metagranite. Location is a roadcut above the river near Dearborn dam. Rocks here are weathered to saprolite i.e.

minerals are chemically altered in place.

333

Vertical Mafic Dikes Injected Into the Metagranite.

343Mafic dike offset by faulting.

353

Contact of mafic dike and granite.Contact of mafic dike and granite.

363

Metagranite

Metagranite

Brunton Brunton compass for compass for

scale.scale.

Brunton Brunton compass for compass for

scale.scale.

Mafic dikeMafic dike