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 siltstone) 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 layer
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 formation
>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.
Arkosic metasandstone Gradational contact into the Lay Dam formation Thin to massively bedded, locally conglomerate, med- coarse grained. Invertebrate fossils bryozoans, gastropods, corals, and brachiopods 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 (D 1 ): Regional Metamorphic (dynamothermal) and recrystallization (M 1 ) event Resulted in Folding (F 1 ) and Foliation (S 1 ): Fold structures range from tight to isoclinal (0 to 20º) F 1 geometry is asymmetric: short limbs 80-90% shorter than long limbs Represented by predominately mesoscopic folds S 1 foliation is parallel to the axial surfaces of the folds
Deformational Phase Three (D 3 ): Intense structural deformation event across the Alabama Piedmont F 3 fold structures vary from tiny crenulations to megascopic folds over 1 km in wavelength F 3 folds generated by flexural slip process Crenulation cleavage (S 3 ) is parallel to the axial planes in F 3. No changes in mineralogy or recrystallization
Deformational Phase Four (D 4 ): Formation of Hollins Line Fault Structures associated with D 3 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 (D 5 ): Folding event of Hollins Line Fault designated as F 4 folding Crenulations crosscut older F 3 structures thereby generating two phases of crenulations Several known megascopic F 4 folds near Millerville HighTower The Goodwater-Enitachopco Fault was not affected by F 4 folding indicating it is younger than the Hollins Line Fault system
Deformational Phase Six (D 6 ): 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)
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 southwestward. 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 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.
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.