presented by: alex owen rachael hudson matt mcdonald kyle williams
TRANSCRIPT
Presented By:
Alex Owen
Rachael Hudson
Matt McDonald
Kyle Williams
Geologic Overview of the Talladega Belt
Location
Precambrian in ageHigh grade belt composed of amphibolite
facies metamorphic rock
Ashland Supergroup
Pre-Cambrian to Cambrian in ageDominantly pelitic rocks
Slates and phylitesBound above and below by carbonate
sequencesTruncated by the Talladega-Carterville fault
Kahatchee Mountain Group
Waxahatchee Slate Formation: Very fine grain, thin laminated grey-green,
charcoal grey, to black meta-mudstone (interbedded with yellow-brown siltstone)
NE unit forms an isoclinal anticline Oolites and stromatolites are presentContacts are conformable and gradationalPelitic rocks contain muscovite flakes and some
biotite
Kahatchee Mt. Group
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
Kahatchee Mt. Group
Wash Creek Slate: Carbonaceous phyllite and fine grain sandstone.
Holds up ridges (sandstones about 86.3 % quartz)
Gradationally overlays Brewer phylite.2300-2400 M thickBioturbation: burrows and feeding trails are
near top of layer
Kahatchee Mt. Group
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
Sylacauga Marble Group
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 formation
Sylacauga Marble Group
Talladega Group (Ordivician-Early Mississippian)
•>2.5 km clastic wedge made up of metaturbidites, arkosic conglomerates, and olistromes (lower Lay Dam Formation)•Formations • Lay Dam Formation (O-S): comprised of
slates and metasandstones• 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.
Lay Dam Formation
Arkosic metasandstone Gradational contact into the Lay Dam
formationThin to massively bedded , locally
conglomerate, med-coarse grained.Invertebrate fossils bryozoans, gastropods,
corals, and brachiopodsSuggested that it is Devonian in age
Butting Ram/ Cheaha Quartzite
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
zoneLower half of Formation contains brachiopodsGradational contact between Hillabee greenstone and
Jemison Chert. Erin slate thickness is estimated to be about 950mLater studies show that Erin is conformable unit at
the top of Talladega GroupMiddle Devonian and Early Mississippian
Jemison Chert/ Erin Slate
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
Hillabee Greenstone
• 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 1
• 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 3
• Deformational Phase Four (D4): Formation of Hollins Line
Fault
• 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 4
• 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
HighTower
• The Goodwater-Enitachopco Fault was not affected by F4 folding indicating it is younger than the Hollins Line
Fault system
Deformational Phase 5
• Deformational Phase Six (D6): Formation of Goodwater-
Enitachopco 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)
Deformational Phase 6
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.
Folds Predating Pre-Lay Dam Unconformity
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 southwestward.
Kelley Mountain Antiform: A companion fold of the Columbiana synform that forms a large composite half window in the Talladega-Cartersville fault.
Folds Postdating Pre-Lay Dam Unconformity
Fayetteville Synform: Companion fold of the Kelley Mountain antiform. Plunges to the southeast and trends northwest-southeast.
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.
Folds Postdating Pre-Lay Dam Unconformity (cont.)
• 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.
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