Geologic Overvi - University of South Alabama

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Transcript Geologic Overvi - University of South Alabama

Presented By:
Alex Owen
Rachael Hudson
Matt McDonald
Kyle Williams
 Precambrian in age
 High grade belt composed of amphibolite facies
metamorphic rock
 Pre-Cambrian to Cambrian in age
 Dominantly pelitic rocks
 Slates and phylites
 Bound above and below by carbonate sequences
 Truncated by the Talladega-Carterville fault
 Waxahatchee Slate Formation:
 Very fine grain, thin laminated grey-green, charcoal grey, to
black meta-mudstone (interbedded with yellow-brown
NE unit forms an isoclinal anticline
Oolites and stromatolites are present
Contacts are conformable and gradational
Pelitic rocks contain muscovite flakes and some biotite
 Brewer Phyllite Formation:
 Gray coarse-grained, poorly sorted sandstone (sub angular-
sub rounded). Thickness: 150-450m
 Meta-siltstone with chlorite porphyroblasts and detrital
muscovite flakes.
 Pelitic rocks are hematitic
 Contains intervals of thick bedded quartzarenite
 Wash Creek Slate:
 Carbonaceous phyllite and fine grain sandstone. Holds up
ridges (sandstones about 86.3 % quartz)
 Gradationally overlays Brewer phylite.
 2300-2400 M thick
 Bioturbation: burrows and feeding trails are near top of
 Gray dolomitic marble, thin laminated micritic marble and
med-grained calcitic marble
 Fossils within group are sparse -due to a singular
metamorphic event
 Jumbo dolomite formation (basal unit)-poorly exposed
with low topography (black slate interbedded)
 Fayetteville Phyllite Formation: Tan, marble, maroon
charcoal purple phyllite
 Shelvin Rock Church Formation: grey thinly laminated
micritic marble with limited phyllite. (calcite/dolomite
with wavy laminations)
 Gooch Branch Chert Formation: Purely calcitic marble
(mostly white) and composes core of Sylacauga syncline.
 Marble observed has tight isoclinal folding with axial plane
parallel or nearly parallel to cleavage in the phyllite
•>2.5 km clastic wedge made up of metaturbidites, arkosic
conglomerates, and olistromes (lower Lay Dam Formation)
•Lay Dam Formation (O-S): comprised of slates and
•Butting Ram/ Cheaha Quartzite (D): contains
metasandstones, conglomerate, and chert
•Jemison Chert/ Erin Slate (D- early M): made of black
slate and siliceous argillite
 Comprised of a >2 km thick clastic wedge and contains
metaturbidites, arcosic conglomerates, and thick
olistromal beds from the south to the southeast.
 Sand to boulder-sized fragments of carbonate rock,
metachert, and metasandstone/metasiltstone are
contained within the olistromal beds which are similar to
the lithology of the underlying Sylacauga Marble and
Kahatchee Mountain groups.
 It is Ordivician to Silurian in age.
 Arkosic metasandstone
 Gradational contact into the Lay Dam formation
 Thin to massively bedded , locally conglomerate, med-
coarse grained.
 Invertebrate fossils bryozoans, gastropods, corals, and
 Suggested that it is Devonian in age
 Contains the thickest (400 m) and least deformed part of
the unit.
Metachert composes 80% of the Jemison.
Fine grained sandy chert common within the phyllite zone
Lower half of Formation contains brachiopods
Gradational contact between Hillabee greenstone and
Jemison Chert.
Erin slate thickness is estimated to be about 950m
Later studies show that Erin is conformable unit at the
top of Talladega Group
Middle Devonian and Early Mississippian
 80% of HG is made up of greenstones and mafic phylites
 Ranges from 2.6 km to only a few hundred meters thick
 Runs 170 km from Cleburne County to Chilton County
• Deformation Phase One (D1): Regional Metamorphic
(dynamothermal) and recrystallization (M1) event
• Resulted in Folding (F1) and Foliation (S1): Fold
structures range from tight to isoclinal (0 to 20º)
• F1 geometry is asymmetric: short limbs 80-90% shorter
than long limbs
• Represented by predominately mesoscopic folds
• S1 foliation is parallel to the axial surfaces of the folds
• Deformational Phase Three (D3): Intense structural
deformation event across the Alabama Piedmont
• F3 fold structures vary from tiny crenulations to
megascopic folds over 1 km in wavelength
• F3 folds generated by flexural slip process
• Crenulation cleavage (S3) is parallel to the axial
planes in F3.
• No changes in mineralogy or recrystallization
• Deformational Phase Four (D4): Formation of Hollins Line
• Structures associated with D3 are deformed by
generation of the Hollins Line Fault
• Reverse thrust fault that juxtaposes lithologies and older
structures between the upper Coosa block and lower
Talladega block
• Knife-sharp contact with variable dips to the southeast
• Deformational Phase Five (D5): Folding event of
Hollins Line Fault designated as F4 folding
• Crenulations crosscut older F3 structures thereby
generating two phases of crenulations
• Several known megascopic F4 folds near Millerville
• The Goodwater-Enitachopco Fault was not affected
by F4 folding indicating it is younger than the Hollins Line
Fault system
• Deformational Phase Six (D6): Formation of GoodwaterEnitachopco Fault System
• This fault system cuts the Hollins Line fault once near
Millerville and again near Hightower
• The fault system juxtaposes the Talladega and Tallapoosa
blocks in the extreme northeast of the Alabama Piedmont
• This fault structure differs from the Hollins Line: contact
is a zone 4 to 50 meters thick and steeply dipping (65-70º)
 Sylacauga Syncline: The hinge of this synclinal fold is
located within the Gooch Branch Chert. The south limb
of the fold is truncated by the unconformity. The fold
plunges at a very low angle to the west-southwest.
 Sycamore Anticline: This fold is a companion of the
Sylacauga Syncline and is located to the south. These
companions share a common limb. The anticline plunges
toward the northeast do to the interference from the
Poe Bridge Mountain synform and the Millerville antiform.
 Columbiana Synform: Occurs along the frontal ramp of
the Talladega-Carterville fault and contains the Sylacauga
Marble Group up to the Shelvin Rock Church formation.
This synform causes the surrounding stratigraphy to
plunge towards the northeast while the fault plunges
 Kelley Mountain Antiform: A companion fold of the
Columbiana synform that forms a large composite half
window in the Talladega-Cartersville fault.
 Fayetteville Synform: Companion fold of the Kelley
Mountain antiform. Plunges to the southeast and trends
 Cross-Antiform and Synform at Sycamore: Companion
antiform of the Poe Bridge Mountain synform and
companion synform to the Millerville antiform. These
folds interfere with the Columbiana- Jemison phase.
• Tull, J. F., 1978, Structural Development of the Alabama Piedmont Northwest
of the Brevard Zone: American Journal of Science., v. 278, April, 1978,
p. 442-446
• Tull, J. F., et al., 1978, The Hillabee Greenstone: Stratigraphy, Geochemistry,
Structure, Mineralization and Theories of Origin: University of Alabama
MRI Research Report Series,
Tull , J. F., Southeastern margin of the middle Paleozoic shelf, southwesternmost
Appalachians: Regional stability bracketed by Acadian and Alleghanian tectonism.