catawba river geology

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.

33

43

Large tor showing exfoliation and jointing.

53

Tor cluster on steep slope that has collapsed.

63

Boulders (Tors) along the river, vertical jointing at

the right.

73

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.

83

Reduced sea level provided a steeperriver gradient - down cutting was muchgreater.

During interglacial epochs sea levelsrose reducing gradients - slowing riverdowncutting.

93

Sea level fluctuations resulted in greater erosion

and down cutting, removed saprolite along steep

slopes exposing widespread single and multiple

corestones.

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..

103

Topographic map of area river diverted below Fishing

Creek Dam.

113Aerial photograph 2004 contour Aerial photograph 2004 contour interval = 2 feetinterval = 2 feet

Cont. Cont. at at

rightright

Cont. Cont. at at

rightright

123

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

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

133

Erosion and Weathering During Pleistocene River Entrenchment

Exposed Numerous Tors (Boulders).

143

The Exposed The Exposed Nitrolee Nitrolee

RiverbedRiverbed Pictures Showing Diversity of Rock

Exposures.

153

Exfoliated Granite Exposed in Middle of River Bed, Facing

Southeast.

163

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

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

River Bed Looking North.

183Exfoliation dome.

193Exfoliation dome.Exfoliation dome.

203

213

223Looking south.

233

243

Granite Pavement in Middle of Exposed River Bed.

25312/22/2008 433

Typicalexposure,MountainIsland in

Back.

263

Round granite Round granite boulder that rolled boulder that rolled from steep slope from steep slope

into the river.into the river.

Round granite Round granite boulder that rolled boulder that rolled from steep slope from steep slope

into the river.into the river.

273Very large tor perched on cliff.

283

Tor, Possibly Rolled Onto Rock Pavement.

Large pavement outcrop.

293

Two large round tors that may have rolled from steep

slope into the main channel note base altered by water

flow.

303

Rock smoothed by river flow, note water level

change.

Anvil rock - a pedestal rock undercut by flowing waters.

313 Anvil rock - a pedestal rock

undercut by flowing waters.

323 Large pedestal Large pedestal

undercut by water flow.undercut by water flow.

333

Excellent pedestal rock in main river channel Nitrolee riverbed.

343

Details of layered metaDetails of layered metagranitegranite texture texture

on a water on a water polishedpolished surface. surface.

353

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

363

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

373

Granular texture in an altered metagranite.

383

Mafic dikes have been intruded into the granite, they

contain minerals that are more water

soluble, therefore, are weathered more

relative to the metagranite.

393

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.

403

Vertical Mafic Dikes Injected Into the Metagranite.

413Mafic dike offset by faulting.

423

Contact of mafic dike and granite.

Contact of mafic dike and granite.

433

Mafic dikeMetagranite

Metagranite

Brunton Brunton compass for compass for

scale.scale.

Brunton Brunton compass for compass for

scale.scale.