The western Georgia Piedmont between the Cartersville and Brevard fault zones

Crawford, Thomas J.; Medlin, Jack H.

doi:10.2475/ajs.273.8.712

Cited by 4 publications

(5 citation statements)

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“…The Austell Gneiss (Sa) has been truncated along its southeastern side by the Chattahoochee fault (Crawford and Medlin, 1973;Hurst, 1973), along its northeastern side by the Olley Creek fault, and along its northern side by faults of the Oak Mountain fault zone. The Chattahoochee fault bounds the southeastern side (German, 1985, p. 15) of the Olley Creek fault zone (proposed here), which is bounded on the northwest by the Olley Creek fault, named for Olley Creek which it follows for several kilometers.…”

Section: Early Silurian Austell Gneissmentioning

confidence: 99%

“…(1) The Chilhowee Group, which is represented in the Atlanta quadrangle by the Crawfish Creek Formation (£cf) and the overlying Nantahala Formation (£n) and its Laffingal Member (£nl). The Crawfish Creek and Nantahala Formations are part of the unit that Crawford and Medlin (1973) called the Frolona Formation, which Higgins and others (1996a) recognized is the Crawfish Creek, Nantahala, Sweetwater Creek, and Illinois Creek Formations. Crawford and others (1999) abandoned the name Frolona because the name Nantahala, which is the unit present at the type locality of the Frolona Formation, had precedence (Keith, 1907).…”

Section: Stratigraphic Sequencementioning

confidence: 99%

“…Crawford and others (1999) abandoned the name Frolona because the name Nantahala, which is the unit present at the type locality of the Frolona Formation, had precedence (Keith, 1907). (2) The Sweetwater Creek and the Illinois Creek Formations (£sw and £i, or £swi where they cannot be divided) (McConnell and Costello, 1980;McConnell and Abrams, 1984;Crawford and others, 1999), which are the nongraphitic parts of the abandoned Frolona Formation of Crawford and Medlin (1973), that crop out in the Austell-Frolona anticlinorium in the southwestern corner of the Atlanta quadrangle. (3) The Bill Arp Formation (O£b) and its informal schist of Hulett facies (O£bh), which directly overlie the Nantahala Formation where the Sweetwater Creek and Illinois Creek Formations are not present.…”

Section: Stratigraphic Sequencementioning

confidence: 99%

“…In western Georgia (Anniston and Atlanta quadrangles and the southwestern part of the Cartersville quadrangle, see fig. 2),• the Bill Arp Formation (Crawford and Medlin, 1973;Higgins and others, 1988) is a clastic metapelitemetagraywacke unit that lacks amphibolite or other metavolcanic rocks and lies structurally and probably stratigraphically above the Illinois Creek Formation in the Corbin massif, and above the undivided Sweetwater Creek and Illinois Creek Formations in the Mulberry Rock structure, the Crawfish Creek structure, and the Austeii-Frolona anticlinorium. Like the Nantahala Formation, the Bill Arp Formation undergoes a facies change in northern Georgia.…”

Section: Bill Arp Formationmentioning

confidence: 99%

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Geologic Map of the Atlanta 30' x 60' Quadrangle, Georgia

Higgins¹,

Crawford²,

Atkins³

et al. 2003

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Section: Early Silurian Austell Gneissmentioning

confidence: 99%

Section: Stratigraphic Sequencementioning

confidence: 99%

Section: Stratigraphic Sequencementioning

confidence: 99%

Section: Bill Arp Formationmentioning

confidence: 99%

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Geologic Map of the Atlanta 30' x 60' Quadrangle, Georgia

Higgins¹,

Crawford²,

Atkins³

et al. 2003

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“…Rocks in the Austell-Frolona antiform, including the Austell gneiss, lie in fault contact with rocks of the Sandy Springs Group to the southeast. A reverse fault, the Chattahoochee fault [Hurst, 1973;Crawford and Medlin, 1973] has juxtaposed rocks of the Sandy Springs Group [Higgins and McConnell, 1978] with those in the Austell-Frolona antfform.…”

Section: Introductionmentioning

confidence: 99%

Magnetization of the Austell Gneiss, northwest Georgia Piedmont

Ellwood¹,

Abrams²

1982

J. Geophys. Res.

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The Austell gneiss is located in the Piedmont 16 km west of Atlanta, Georgia, and 8 km northwest of the Brevard fault zone. This metamorphosed granite gneiss lies refolded in the nose of the Austell‐Frolona antiform, a doubly plunging structure of regional extent. Subsequent to intrusion, the unit has undergone four episodes of deformation. The first and second generation folds (F1 and F2) are coaxial but not coplanar. The two later fold events were less intense and have little effect on local outcrop patterns in the study area. The age of the unit has been estimated to be greater than 325 m.y. but less than 365 m.y. The induced and remanent magnetic properties for at least six cores drilled at each of 10 sites within the Austell gneiss have been determined. The magnetic foliation for the unit is approximately parallel with field estimates for S1 foliation planes exhibited by mineral orientations within the body, indicating post‐emplacement magnetic grain mobility. The stable remanent magnetization exhibited by the body was therefore probably acquired during or slightly after the F1 or F2 deformational events as a result of cooling from metamorphic temperatures (∼600°C), or, alternatively, from secondary magnetite grain nucleation and growth. A paleopole position calculated for these data without structural correction, ϕ = 126.2, θ = 34.4, dp = 6.6, dm = 13.2, can be explained by magnetic acquisition in at least three possible geologic settings. From simple to complex, these are the following: First, since a large oval of confidence is observed for the unit and minor tilting can not be resolved, the data may be explained by magnetization of the Austell at its present site during cooling from metamorphic temperatures. Second, a northwestward thrust event may have resulted in bringing the Austell to its present location. Third, the data can be explained by two major translational events. The Austell may have initially been magnetized and then moved to the northeast by transcurrent strike slip faulting >1000 km into juxtaposition with the southern Appalachians, followed by thrusting of the unit to the northwest to its present location. In support of this last interpretation is the similarity between the paleopole for the Austell and paleopoles determined for the Maritime Provinces of North America, which were suggested to have moved ∼1500 km to the northeast during the mid to late Paleozoic. Against such an interpretation is the lack of geologic evidence in support of large‐scale left‐lateral strike slip faulting in the southern Appalachians.

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