Transcript Recommendation of a Strategy - University of South Alabama

Cheaha State Park
Highest Point in Alabama
Elevation: 2,413 ft
Bunker Tower on top of the
Mountain. There is a USGS
Marker in front which notates
Highest point.
Location Map of The Piedmont Upland. The broken
back line separates the northern from the southern
piedmont upland districts. The boundary between the
Piedmont and the Valley and Ridge in Chilton and
Shelby counties on the map does not match the geologic
boundary between sedimentary and metamorphic rocks.
The blue line shows the line of the topographic profile (Figure PD1).
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Stage 1: Compressional Deformation in foreland
Stage 2: Low angle thrust sheets
Stage 3: Redeformation of stage 2 nappe pile by
large scale upright folds
Stage 4: Renewed low angle thrusting within
Piedmont rocks
Stage 5: Large scale cross folding at high angle to
previous thrust phases
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Harpersville Generation Folds
Pell City Fault
Sleeping Giants-Choccolocco MountainIndian Mountain Thrust Complex
Talladega Cartersville Fault
Columbiana-Jemison Generation Folds
Hollins Line Fault
Millerville-Childersburg Generation Folds
Goodwater-Enitachopco and Eden Faults
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Folds that occur in the Pell City thrust sheet
Bound by the Pell City Fault and the
Talladega-Cartersville Fault
Large-scale, upright, tight isoclinal folds
Outlined by Ordovician shales and carbonates
Thought to be any age post-middle Ordovician
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Rocks of Pell City thrust sheet have undergone
minimal horizontal slip. This means that
structures predating the fault are found on
both sides
Footwall is generally a narrow, highly
imbricate thrust faulted zone between Pell City
and the Eden Faults (referred to as the Coosa
deformed belt)
Imbricate thrusts in Coosa deformed belt cut
Upper Mississippian rocks are in turn cut by
Pell City Fault
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Thrust slices along
the southeastern
margin of Pell City
thrust sheet
Contain Lower
Cambrian rocks
Variously interpretted
as klippen above
Talladega-Cartersville
Fault
Choccolocco Mountain
Bains Gap Waterfall
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Forms boundary between foreland fold and thrust
belt and the Talladega slate belt
Has large displacement and one of most significant
thrust faults in southern Appalachians
Dischordant to stratigraphy in upper and lower
plates, and to individual thrust plates and
structures below it
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Large scale folds in Chilton, Shelby, and
Talladega counties
Orientation is variable because previously
deformed and non-parallel surfaces are
involved and there is later refolding
Doubly plunge to NE and SW
There are three major structures: the
Columbian synform, the Jemison synform, and
the Kelley mountain antiform
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Forms boundary between Talladega slate belt
and rocks of overlying Ashland Supergroup in
Coosa and Chilton Counties
It is the roof thrust of a major thrust duplex
system that involves large-scale imbrication of
the upper part of the Talladega slate belt
Structure was tilted southeast by subsequent
deformational events leading to the oblique
view of the duplex and the braided pattern of
footwall horses
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Major subregional recess that results from and
antiform-synform pair
Holds the Hillins Line Fault and rock units and
structures within both the hanging wall and
footwall, including the Talladega-Cartersville
Fault, the Pell City Fault, and the faults at the
base of the Sleeping Giant- Choccolocco
Mountain- Indian Mountain thrust complex
Forms a broad synform in the Talladega slate
belt
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Cuts through Millerville-Childersburg Folds
and earlier structures like Hollins Line Fault
Youngest major structures present
Steep reverse faults
Greater regional dip than the major thrusts that
occur between them.
The intensity of metamorphism increases southeast from the Talladega belt to the Southern Piedmont. P/T
determinations on some rocks indicate temperatures as high as 1,400OF and depth of burial during
metamorphism of 15 miles. The main metamorphic event took place about 360-380 Ma (millions of years
before present), which means that as much as 15 miles of material has been eroded since that time to
expose these rocks on the surface.
The rocks in each belt are folded and suffered several episodes of folding. Small and early folds tend to
be isoclinal, while the later and larger folds are more open.
Early isoclinal fold, Dadeville Complex,
Tallapoosa County
Later syncline in quartzite, Pine Mountain
Group, Lee County
Geologic belts in the Piedmont (from Guthrie and others
1994: Alabama Geological Survey):
1. Solid red line: belt-bounding faults
2. Broken red line: faults within a belt
3. Thin red line: belt contact of unknown type
4. Green line: coastal plain boundary.
The Piedmont consists six northeasterly-southwesterly trending belts of metamorphic rocks. With the
exception of the boundary between the Opelika and Dadeville belts, each belt is bordered by a fault.
Most faults are interpreted as thrust faults, though movement along the Towaliga, Brevard, Bartlett's
Ferry and Goat Rock faults appears tohave been long and complex. The thrust faults moved blocks
of rocks northwestward.
The Northern Piedmont consists of the Talladega and Ashland-Wedowee belts. The Talladega belt
contains slate, phyllite, marble, quartzite and greenstone. The Ashland-Wedowee belt contains phyllite,
schist, gneiss and amphibolite.
The Inner and Southern Piedmont contain the remaining 4 belts (Dadeville, Opelika, Pine Mountain,
Uchee). These belts contain amphibolite, schist and gneiss. The Pine Mountain belt also contains
quartzite and marble, as well as the oldest radiometrically-dated rock in Alabama. It is a gneiss that
crops out in Chewacla State Park near Auburn and dates at 1,050 million years.
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Kahatchee Mountain Group
Sylacauga Marble Group
Talladega Group
Hillabee Greenstone
Sylacauga
Marble
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Outcrop width varies from 6-30 km
Dischordant with lower units
Dominantly pelitic slate and phyllite and
metasandstone (also includes a minor
carbonate unit known as the Sawyer
Limestone)
Lots of debate on the stratigraphic equivalence
of other rocks in places like Georgia
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Variable series of dolomite and calcite marbles
Locally cherty and interlayered with phyllites
Upper contact appears to be slightly
dischordant
1700 m thick
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Defined as the phyllites and metasandstones
exposed along Talladega Creek in Clay and
Talladega Counties
Lay Dam Formation: sequence of slates and
metasandstones, large percentage is also unsorted
and unbedded diamictite, 4.5 km thick
Butting Ram Quartzite: thickbedded, course
grained arkosic metasandstone intercalated with
slates and layers of diamictite, variable thickness
(max 850 m)
Jemison Chert: massive, thickbedded, fine-grained
greyish-white metachert, contains marine
invertebrate fossils
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More than 80% of exposed area is composed of
mafic rocks that can be subdivided into
Greenstones and mafic phyllites (greenschists)
Greenstones generally massive, fine-grained, pale
green to light olive-brown and weather to dark
red or brownish yellow color
Mafic phyllites are well foliated slaty rocks and
commonly display laminar layering. Consist of
albite, actinolite, epidote, zoisite, clinozoisite, and
chlorite, although dynamothermal metamorphism
has made primary mineral phases rare
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Higgins Ferry Group: Gneiss, schist
Poe Bridge Mountain Group: Schist, gneiss
Hatchet Creek Group: Gneiss, schist, quartzite
Mad Indian Group: Gneiss, schist
Wedowee Group: Phyllite, gneiss, schist,
quartzite (no slide later)
Emuckfaw Group: Schist, quartzite
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Interbedded clastic and pelitic units with
occasional amphibolite, all of which are
metamorphically retrograded and
differentially folded
Accessory minerals include kyanite,
sillimanite, rutile, and magnetite
Especially well exposed in western Coosa and
eastern Chilton counties
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Almost identiacal in composition to the
Higgins Ferry group, but classified differently
because the two areas are disconnected by
major transverse faults and individual units
can’t be traced from one area to another
Width ranges from 1-13 km
Unit weathers easily because of high feldspar
content
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Two distinct units: Hanover Schist and
Pinchoulee Gneiss
Hanover Schist: consists of staurolite-albitebiotite-sericite quartz muscovite schist and
staurolite biotite feldspathic gneiss
Pinchoulee Gneiss: consists of feldspathic and
migmatitic biotite gneiss
Rocks of Hatchet Creek group are in the upper
amphibolite facies of regional metamorphism
Pegmatites are common
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Composed of interbedded and infolded schist,
gneiss, and amphibolite with scattered granitic
intrusions
Interpretted as complexly folded series of
metasedimentary rocks that have undergone
extensive recrystallization
Metamorphic grade is in the sillimanite or kyanite
subfacies of the almandine-amphibolite facies (but
lower metamorphic facies are scattered
throughout outcrop area and are typically
associated related to late structural features)
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Interlayered sequence of schist and gneiss
Schist is generally medium grained and
composed of muscovite, feldspar, and quartz.
Mineral composition is suggestive of a
subgraywacke
Contains a fair amount of garnets, from 1mm-1
cm depending on area of formation
Commonly exhibits tight crenulation folds
Weathers to a white, sandy, muscovite rich soil