catawba river geology
TRANSCRIPT
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.