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
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
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