Transcript Slide 1

By
Steve Gurley and Allen Hubbard
April 23, 2009
Some Geologic Concepts
 Geologic time – think in terms of millions and even billions
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of years. Earth about 4.5 billion years.
Oldest rocks in Lincoln County 600+ million years
Youngest geologic materials are floodplain alluvium
deposits and slope wash.
Lincoln County and all the Piedmont and Blue Ridge have
undergone millions of years of erosion.
Rocks in Lincoln County have gone through various phases
of metamorphism as a result of deep burial and/or earth
movement (tectonics) associated with major mountain
building episodes (orogenies).
Overview
 Most of Lincoln County, like most of the Piedmont and
Blue Ridge of NC, roots of old mountains
 Many of the rocks at surface today were several miles
underground during mountain building episodes.
 Evidence of three major mountain building events in
Lincoln County
 Taconic Orogeny (Tugaloo Terrane)
 Acadian Orogeny (Cat Square Terrane)
 Alleghenian Orogeny (Charlotte and Kings Mountain (?)
Terranes)
Overview (cont’d)
 Lincoln County in four geologic terranes
 Charlotte – Eastern
 Kings Mountain? – East and East Central
 Tugaloo – North Central
 Cat Square – Western
Structure
 Central Piedmont Suture
 Kings Mountain Shear Zone (Central Piedmont
Suture?)
 Newton Window and Brendle Creek Fault
 Eufola Fault
 Rock joints and fractures
Rocks
 Charlotte Terrane
 Metamorphosed granite
 Metamorphosed diorite
Rocks (cont’d)
 Kings Mountain Terrane
 Battleground Formation
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Quartzite (metamorphosed sandstone)
Phyllite (metamorphosed siltstone)
Schist (metamorphosed clay stone)
 High Shoals Granite
 Blacksburg Formation
 Quartzite
 Meta-Conglomerate
 Phyllite
 Schist
Rocks (cont’d)
 Tugaloo Terrane
 Biotite gneiss (metamorphosed clayey sandstone)
 Hornblende gneiss (amphibolite)
 Garnet-quartz rock (gondite)
Rocks (cont’d)
 Cat Square Terrane
 Walker Top Granite
 Toluca Granite
 Biotite gneiss (metamorphosed clayey sandstone)
 Sillimanite schist (metamorphosed clay stone and
siltstone)
 The Great Dike
Focus on Indian/Howards Creek
Basins
 Tugaloo and Cat Square Terranes
 Landforms/topography
 Stream orientation
 Rappahannock/Tallapoosa Line
 Soils
 Generally deep, well drained, low pH red Piedmont clays
 Soils associated with darker rocks (amphibolites,
diorites, etc.) generally have mixed clay mineralogy
making them less suitable for on-site development
Focus on Indian/Howards Creek
Basins (cont’d)
 Environmental geology
 Groundwater geology
 Erosion susceptibility (clayey soils and deep saprolite)
 Water supply watershed (Indian Creek – Cherryville and
High Shoals)
 Mineral Resources
 Monazite (phosphate mineral containing radioactive
thorium) in granites and biotite gneisses
 Spodumene (lithium mineral) in Cherryville Granite
 Sand in alluvial deposits along streams