Major Tectonic Features arid Struc 

Elemerats in the Northwest r ,£1 ,'f 

the Greenville Quadrangle, 

I . 

.. I • 
'· 
Major Tectonic Features and Structural 

Elements in the Northwest Part of 

The Greenville Quadrangle, Georgia 

By ARTHUR E. NELSON 

A study of major structural 

features, tectonic fabrics, and 

fold analyses of polydeformed 

metamorphic rocks 

comprising three major thrust 

sheets that together form a 

large part of the southern 

Appalachian Mountains in 

northeast Georgia 

U.S. GEOLOGICAL SURVEY BULLETIN 1643 
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1985 

For sale by the Distribution Branch, U.S. Geological Survey, 

604 South Pickett Street, Alexandria, VA 22304 

Library of Congress Cataloging in Publication Data 

Nelson, Arthur E. (Arthur Edward), 1922-

Major tectonic features and structural elements in the northwest part of the Greenville quadrangle, Ga. 

(U.S. Geological Survey bulletin; 1643) 

Bibliography: p. 

Supt. of Docs. no.: I 19.3:1643 

1. Geology-Georgia-Greenville region. 2. Geology, structural. I. Title. II. Series: Geological Survey bulletin; 1643. 

QE75.B9 no. 1643 557.3 s [557.58'455] 85-600011 [QE102.G73] 
CONTENTS 

Abstract 1 

Introduction 1 

Previous work 1 

General geology 1 

Great Smoky thrust sheet 2 

Hayesville thrust sheet 2 

Mafic and ultramafic rocks 3 

Helen-Coweeta terrane 4 

Metamorphism 4 

Structural geology 5 

Faults, joints, and lineament trends 5 

Folding and related deformation 6 

Fold analyses 12 

Area I 12 

Area II 12 

Area III 12 

Area IV 14 

Area V 14 

The northwest subdivision 14 

Helen-Coweeta terrane 14 

East part of Hayesville sheet 16 

Brasstown Bald window 16 

Crenulation cleavage (S3) 16 

F J fold analysis 18 

Summary and conclusions 18 

References cited 21 

FIGURES 

1. Maps showing (A) location of report area and generalized tectonic features 

of northeast Georgia and (B) generalized lithotectonic features of the 

northwest part of the Greenville 2-degree quadrangle, Georgia 2,3 

2. Landsat image of the northwest part of the Greenville 2-degree quadrangle 

and approximate boundaries of the major lithotectonic units of the area 6 

3. Photograph showing three fold phases at an exposure in Brasstown Creek, 

Georgia 8 

4. Photograph showing type 3 fold interference pattern at an outcrop along the 

Richard Russell Highway, Georgia 9 

5. Photograph showing outcrop that contains hinge of an F1 isoclinal fold in 

siliceous metasandstone and schist in the Hayesville thrust sheet, 

Georgia 9 

6. Photograph showing F2 fold that is overturned to the northwest, western 

Union County, Georgia 9 

7. Photograph showing an exposure that displays S0, S~, and S3 foliation, Brasstown Bald, Georgia 10 

Contents Ill 
8. Photograph showing exposure that displays a rootless F2 fold and an F3 fold 

with an axial planar crenulation cleavage, southeast of Young Harris, 

Georgia 10 

9. Photograph showing gently inclined saprolite exposure that shows a small 

conjugate F3 fold pair, north of Ebenezer Church, Georgia 10 

10. Map showing generalized structure of the report area as displayed by foliation form lines 11 

11. Map showing structural areas in northwest Greenville quadrangle, Georgia, 

that were used for statistical analyses of fold events 12 

12. Contoured equal area projections of poles to s. and F2 and F3 fold attitudes 

for areas shown in figure 11 13 

13. Contoured equal area projections of various planar and linear features in 

northwest Greenville quadrangle, Georgia 15 

14. Contoured equal area projections of various planar and linear features in the 

Brasstown Bald area and northwest Greenville quadrangle, Georgia 17 

15. Diagram depicting deformed S1 surface in the area southeast ofthe Hayesville fault, Georgia 20 

IV Contents 
Major Tectonic Features and Structural Elements in 

the Northwest Part of the Greenville Quadrangle, 

Georgia 

By Arthur E. Nelson 

Abstract 

The rocks underlying the northwest part of the Greenville 2-degree quadrangle form parts of three lithotectonic 

units. From northwest to southeast, they are the Great 

Smoky thrust sheet, the Hayesville thrust sheet, and the 

Helen-Coweeta terrane, which divides the Hayesville 

sheet diagonally southwest to northeast. The Hayesville 

thrust sheet was transported westward over the Great 

Smoky thrust sheet along the Hayesville thrust fault. The 

Hayesville fault is part of a major fault system in the southern Appalachian Mountains; in the study area, the Hayesville fault also forms the contact around several windows 

of the Great Smoky thrust sheet through the Hayesville 

thrust sheet. 

landsat images show that each lithotectonic unit is 

characterized by lineaments with distinct trends. The lineaments probably represent fracture zones. They suggest 

that rocks of each lithotectonic unit yielded differently to 

stress or that lineaments were present before thrust emplacement, and they imply different prethrust tectonic histories for the different thrust sheets. 

Rocks in the study area were deformed by at least four 

phases of folding; the second generation folds (Fv form 

the dominant folds and have northeast-trending axes. 

Northwest of the Hayesville fault, the F2 fold axial surfaces 

are upright to steeply inclined; southeast of the fault, the 

F2 axial surfaces range from recumbent to steeply inclined. 

A set of conjugate folds {F3) whose axes trend northnortheast and west-northwest refolds the F2 folds. The F3 

fold axial surfaces are upright to steeply inclined. 

Analysis of conjugate folds (F3) shows that the direction 

of maximum compression during F3 folding was northeastsouthwest, almost parallel to the regional (S1) foliation 

trend. This direction is nearly normal to the maximum 

compression direction during F2 folding. The F3 maximum 

compression direction probably is due to a relaxation of 

compressive stress or due to elastic rebound after F2 

folding. 

INTRODUCTION 

This report describes and interprets the general 

structure and deformation chronology of 

polydeformed metamorphic rocks underlying the 

J)Orthwest part of the Greenville 2-degree quadrangle 

in northeast Georgia (fig. 1). Because most earlier 

geologic investigations of the area were of a reconnaissance nature and because many remote sections 

were not previously mapped, the geologic detail of 

much of the study area has not been well understood. 

My investigation indicates that the rocks underlying 

the report area are allochthonous. They have been 

folded during at least four and possibly six folding 

phases, and they have been locally deformed by ductile and brittle faulting. 

Previous work 

Yeates and McCallie (1896) and Park (1953) 

described some of the gold deposits and mining 

properties of Georgia. One of the major gold producing zones, the Dahlonega gold belt, extends northeast 

from Dahlonega and forms part of the HelenCoweeta terrane, defined later in this report (see p. 

4). Hopkins (1914) described soapstone, and Furcron and Teague (1943) reported on the mica-bearing 

pegmatites within the study area. Crickmay (1952) 

and Hurst (1973) described rocks in this area as part 

of their general descriptions of the Blue Ridge crystalline rocks. Hartley (1973) reported on the ultramafic rocks present in the north part of the area, 

and Hatcher ( 1971) described the geology of Rabun 

and Habersham Counties, Ga. Hatcher also reported 

on the various aspects of the tectonic history of 

northern Georgia and surrounding areas (1974, 1976, 

1978a, c). The general geology of the area is shown on 

the Geologic Map of Georgia (Georgia Geological 

Survey, 1976). Dupuis (1975) and Wooten (1980) 

mapped adjoining areas to the west and north, respectively, of the report area, and Shellebarger ( 1980) 

and Gillon (1982) mapped parts of the study area as 

part of the U.S. Geological Survey Greenville 2-degree quadrangle mapping project. 

GENERAL GEOLOGY 

Three lithotectonic units underlie the northwest 

part of the Greenville 2-degree quadrangle in northAbstract 1 
east Georgia. From northwest to southeast, these 

units are the Great Smoky thrust sheet, the Hayesville thrust sheet, and the Helen-Coweeta terrane. 

The Hayesville sheet was transported westward over 

the Great Smoky sheet along the Hayesville fault, a 

major Appalachian tectonic feature (Williams, 1978). 

Rocks of the Great Smoky sheet underlie the Hayesville fault and are exposed in several windows 

through the Hayesville sheet. The Helen Group (informal usage of Gillon, 1982) and the Coweeta 

Group of Hatcher ( 1979) form a long narrow 

lithotectonic unit herein called the Helen-Coweeta 

terrane that divides diagonally from southwest to 

northeast the Hayesville sheet in northeast Georgia 

and adjacent North Carolina. 

Great Smoky thrust sheet 

Rocks of the Great Smoky thrust sheet consist 

chiefly of interbedded feldspathic and argillaceous 

metasandstone, metaconglomerate, muscovite schist, 

and calc-silicate granofels that together form various 

groups and formations of the Ocoee Supergroup 

(Higgins and Zietz, 197 5) of Late Proterozoic age. 

Although the Great Smoky sheet rocks have been 

metamorphosed and polydeformed, original bedding, 

even at sillimanite grade, is preserved locally. Middle 

Proterozoic plutonic rocks and variably layered 

paragneisses form the basement rocks in parts of the 

Great Smoky thrust sheet, but they are not exposed 

in the report area. 

Hayesville thrust sheet 

Two formations make up the Hayesville thrust 

sheet in the report area; (1) the Tallulah Falls Formation (Hatcher, 1971; Bell and Luce, 1983), which occupies most of the eastern part, and (2) the Richard 

Russell Formation (informal usage of Gillon, 1982), 

which occupies the western part. The Richard Russell 

Formation probably is equivalent to the Tallulah 

Falls Formation of probable late Precambrian age 

(Hatcher, 1971; Bell and Luce, 1983). 

The Richard Russell Formation consists primarily of biotite gneiss and lesser amounts of mica 

schist, fine-grained feldspar gneiss, metasandstone, 

quartzite, hornblende gneiss, amphibolite, and some 

calc-silicate layers. Granitic and granodiorite gneisses 

are interlayered with these rocks. Numerous discontinuous pegmatite veins and pods of various sizes are 

dispersed widely throughout the Hayesville sheet, 

and migmatitic biotite gneiss and granitic gneiss are 

abundant. In the Hayesville thrust sheet near the 

0 10 20 30 KILOMETERS· 

I I I I 

A 

Figure lA. location of report area and generalized tectonic map of northeast Georgia. B, Blairsville; C, Canton; D, 

Dahlonega; H, Helen; GSTS, Great Smoky thrust sheet; 

HTS, Hayesville thrust sheet; H-C, Helen-Cowetta terrane; 

DF, Dahlonega fault; SFF, Shope Fork fault; HF, Hayesville 

fault; A-HF, Allatoona-Hayesville fault; BZ, Brevard zone. 

Hayesville fault, some diamictite is exposed. Although the diamictite is not widespread, its presence 

suggests that it probably formed as the Hayesville 

sheet advanced northwesterly. Some Grenville (Middle Proterozoic) basement rocks are exposed east of 

the report area (in the eastern part of the Hayesville 

thrust sheet), but they have not been observed in the 

study area. 

Rocks of the Hayesville sheet, particularly units 

of biotite gneiss, mica schist, and metasandstone, are 

variably layered. Compositional layering, which results from metamorphic differentiation and transposition of bedding into the regional foliation, is widespread in the report area. Hatcher (1976) described 

similar transposed bedding farther east in the Hayesville sheet. The transposition and metamorphic differentiation probably destroyed most of the primary 

sedimentary features that may have existed in the 

rocks. Layers in most of the rocks range from 2 to 15 

em in thickness; rarely are rock layers greater than 1 

m thick. As a result of interlayering, metamorphic 

differentiation, and transposition of rock units, contacts between mapped units in the Hayesville thrust 

sheet are commonly gradational (Nelson, 1982, 

1983a and b; Nelson and Koeppen, 1984). 

2 Tectonic Features and Structural Elements, Northeast Greenville Quadrangle, Ga. 
HTS 

A 

B 

Shooting Creek 

window 

HTS 

DAHLONEGA 

EXPLANATION 

IGsrsJ 

GSTS, Great Smoky thrust sheet: 

Undivided metasandstone, schist, 

and metasiltstone 

I HTS I 

HTS, Hayesville thrust sheet: Undivided metasandstone, biotite gneiss 

and schist, amphibolite, hornblende 

gneiss, granitic gneiss, mafic and 

ultramafic rocks, and some Grenville 

age basement rocks 

H-C, Helen-Coweeta terrane: Undivided metasandstone, metasiltstone, 

massive biotite gneiss and schist, 

aluminous and graphitic schist, 

granitic gneiss, quartzite, amphibolite, and some ultramafic rocks 

0 

Thrust fault 

~ 

Kyanite 

Isograd 

Approximate position adopted frorri 

Hatcher (1971), Shellebarger 

(1980), and Gillon (1982) 

10 15 KILOMETERS 

Figure 1 8. Generalized lithotectonic map of the northwest part of the Greenville 2-degree quadrangle, Georgia. 

Mafic and ultramafic rocks 

A wide variety of ultramafic and mafic rocks is 

present in the Hayesville sheet, some as small discontinuous pods, some as large mappable units (Hadley 

and Nelson, 1971; Nelson, 1982, 1983a and b). These 

rocks are chiefly serpentinite, dunite, pyroxenite, 

gabbro, and amphibolite (Hartley, 1973). Locally, 

some of these rocks are magnetite rich. The relation 

of the ultramafic rocks to the Hayesville sheet is uncertain. The ultramafic rocks have chemical affinities 

with mantle rocks (Hartley, 1973, p. 59) and, as such, 

may represent fragments of oceanic crust caught up 

in the Hayesville sheet during or before westward 

emplacement of the Hayesville sheet. Some ultramafic rocks are believed to represent small separate thrust slices of oceanic crust underlying the 

Hayesville sheet. 

Ultramafic and mafic rocks that surround the 

Brasstown Bald window (in the north-central portion 

General Geology 3 
of the study area) are believed to form a separate 

thrust slice of oceanic crust between the Hayesville 

and Great Smoky thrust sheets (fig. lB). Some ultramafic and mafic rock bodies high in the thrust 

sheet may represent diapirs or small intrusives. Other 

ultramafic and mafic rocks are exposed along strike 

northeast of the report area, and some ultramafic 

bodies are probably present locally but concealed 

within the Hayesville sheet elsewhere in the study 

area. 

Helen-Coweeta Terrane 

Rocks of the Helen Group (informal usage of 

Gillon, 1982) and the overlying Coweeta Group 

(Hatcher, 1979) form the Helen-Coweeta terrane (fig. 

1B) that extends northeastward from Dahlonega, Ga. 

This terrane varies in width and divides the Hayesville thrust sheet diagonally into almost equal areas 

(fig. lB). The Helen Group contains numerous rock 

types, including metagraywacke, quartzite, graphitebearing garnet-muscovite-biotite schist, metasiltstone, phyllite, and impure feldspathic metasandstone that is locally conglomeratic and interlayered 

with thin muscovite schist beds. Thin to thick layers 

of amphibolite also are present, as are some granitic 

gneiss and ultramafic bodies. Rocks of the HelenCoweeta terrane range from garnet(?)-staurolite to 

kyanite grade; locally they are retrograded. 

The Coweeta Group includes feldspar quartzbiotite-epidote gneiss, metasandstone, granofels, 

quartzite, aluminous sch~~t:L _ _gametiferous biotite 

schist, and minor amphibolite. Granitic gneiss and 

-some ultra mafic rocks also are present. Rocks of the 

Coweeta Group overlie the Helen Group and range 

from staurolite-kyanite to sillimanite grade; locally 

they are retrograded. 

Although some rock types in both the Coweeta 

and Helen Groups are similar, their overall lithology 

differs significantly. Rocks in the Coweeta- Group 

commonly contain numerous thin layers of calc-silicate granofels, which is rarely seen in rocks of the 

Helen Group. The Helen Group contains relatively 

thick units of amphibolite, graphite schist, and 

metasiltstone units, all of which are much less abundant or are absent in the Coweeta Group. 

Correlations of rock units in the Helen-Coweeta 

terrane with mapped units along strike in the vicinity 

of Canton, Ga. (McConnell and Costello, 1980), are 

somewhat tenuous. The Canton area is about 45 km 

southwest of the study area; the area between Canton 

and the Helen-Coweeta terrane is unmapped. No 

one-to-one correlation of mapped units between the 

Helen-Coweeta terrane and the Canton area exists, 

and the Helen-Coweeta terrane has been deformed 

by faulting. Nevertheless, recent investigations by K. 

I. McConnell and J. 0. Costello (1981, oral commun.) indicate that some units in the terrane do correlate with units of the New Georgia Group to the 

southwest (Abrams and McConnell, 1981 ). 

While some rock assemblages of the HelenCoweeta terrane appear to correlate with rocks of the 

Canton area, part of the terrane resembles Ocoee 

rocks of the Great Smoky thrust sheet. Incomplete 

studies by me suggest that some Ocoee rocks may be 

present in the terrane, either as a window or as a 

tectonically emplaced unit. Ocoee rocks are exposed 

in the Brasstown Bald and Shooting Creek windows 

to the northwest in the Hayesville sheet; the Brasstown Bald window is about 12 km northwest of the 

Helen-Coweeta terrane. Because the Helen-Coweeta 

terrane has been deformed by faulting, some Ocoee 

rock units may have been tectonically emplaced. This 

emplacement is plausible because part of the Great 

Smoky thrust sheet is exposed along the trend of the 

Helen-Coweeta terrane just west and southwest of 

Dahlonega (fig. lA). Rocks of the Great Smoky sheet 

are in this location because of a southerly bend of the 

Hayesville fault (Williams, 1978) in the adjoining 

Rome 2-degree quadrangle (fig. 1A). Current field 

studies should help resolve this problem. 

Metamorphism 

A Paleozoic Barrovian-type prograde regional 

metamorphism affected the southern Blue Ridge 

rocks (Hadley and Goldsmith, 1963; Carpenter 1970; 

Butler 1972; Dallmeyer 1975). This metamorphic 

event probably occurred during the Taconic orogeny 

about 450 m.y. to 480 m.y. ago (Butler, 1972; Dallmeyer 197 5). Much of the report area is within a 

large, elongate, northeast-trending sillimanite-grade 

metamorphic zone (fig. lB). However, lower grade 

rocks ( staurolite-kyanite) border the higher grade sillimanite zone in the northwest part of the area. Lower grade rocks also are present in the southeast part of 

the area, especially near the Brevard zone (fig. 1B). 

The southern part of the Helen-Coweeta terrane, 

which ranges from garnet(?)-staurolite to kyanite 

grade, is bordered on both sides by sillimanite-grade 

rocks of the Hayesville thrust sheet. 

Within the sillimanite zone, the effects of metamorphic differentiation and anatectic melting are 

particularly noticeable. Biotite gneiss, mica schist, 

and metasandstone units of the Hayesville sheet have 

4 Tectonic Features and Structural Elements, Northeast Greenville Quadrangle, Ga. 
been variably migmatized and have been differentiated to form gneisses of banded leucosomes and melanosomes. Quartz, which is highly mobile, also has 

been segregated into variably sized veins and pods 

that are widespread. Veins and irregular bodies of 

quartzofeldspathic segregations and anatectic melt 

materials and irregular granite bodies also are common. The migmatized and differentiated rocks of the 

Hayesville sheet contrast strongly with rocks of the 

Great Smoky sheet, which are only slightly migmatitic and do not have an abundance of feldspathic differentiates, even though they are at the same metamorphic grade as the Hayesville sheet rocks. Rocks in 

the study area at kyanite grade are essentially 

nonmigmatitic; they do not have an abundance of 

feldspathic differentiates, and the effects of metamorphic differentiation are rare. 

Sillimanite is distributed widely in most pelitic 

rocks within the sillimanite zone and is commonly 

present in rocks with a moderate quartz content and 

a moderate to low muscovite content. Sillimanite lies 

in and most probably grew in the regional foliation 

planes (S1) during the high temperature peak of regional metamorphism. The foliation formed during 

the 450- to 480-m.y. regional metamorphic event but 

before the high temperature peak. The foliation 

planes were later deformed during regional folding 

(F2) that probably occurred slightly after the high 

temperature peak. 

Ten1peratures probably remained elevated in 

the study area through an episode of deformation 

that occurred after the regional F2 folding. The apparent growth of biotite along planes parallel to the third 

fold generation (F3) axial surfaces supports this hypothesis. Therefore, I believe that temperatures remained elevated in the study area at least until after 

the F 3 folding event. 

In some places, prograde metamorphic minerals have been retrogressively altered. Some, but not 

all, of the altered areas appear to be related to shear 

zones. The alteration is not intense, nor is it widespread. Sillimanite alters to sericite or sericitic clusters, and garnet and biotite alter to chlorite. Some 

plagioclase is saussuritized. Most of the ultramafic 

rocks are extensively chloritized, are serpentinized, 

and are altered locally to talc schists. The age of retrogression is uncertain, and several estimates have 

been proposed for the time of retrograde alteration in 

the southern Appalachian Mountains. Hatcher 

(1972) and Butler (1973) suggested that the alteration 

was due to a Permian thermal event, probably related 

to late Paleozoic thrusting. Shellebarger ( 1980) believes that the alteration resulted from uplift and 

cooling after the last deformation and thus does not 

necessarily imply a separate thermal event. 

STRUCTURAL GEOLOGY 

Faults, joints, and lineament trends 

Numerous thrust faults characterize the southem Appalachian Mountains (Rodgers, 1953; King, 

1964; Hadley and Goldsmith, 1963; Hadley and Nelson, 1971; Hatcher, 1971, 1972). The Hayesville 

thrust sheet was pushed westward over the Great 

Smoky thrust sheet along the Hayesville fault. I believe this fault is premetamorphic to early 

synmetamorphic. The fault does not offset the sillimanite isograd (fig. 1 ), and the foliation (S1) attitudes 

in rocks on either side of the fault do not appear to be 

deflected in the Greenville quadrangle or in the area 

to the north (Wooten, 1980). 

Shellebarger ( 1980) described the Hayesville 

fault and summarized evidence that supports its occurrence in the northwestern part of the Greenville 

quadrangle. He indicated that the fault juxtaposes 

rocks of different lithologies and structural style. 

Southeast of this fault, the Hayesville thrust sheet 

contains most of the known ultramafic rocks and intrusive plutons and volcanic rocks. In addition, the 

metasandstones are more garnetiferous, and the 

schists more mafic, than similar rock types occurring 

in the Great Smoky thrust sheet. In places along the 

Hayesville fault, competent rock types of the Hayesville sheet have been changed to blastomylonite and 

mylonite gneiss. Southeast of the Hayesville fault, the 

rocks are recumbently folded, whereas the rocks 

northwest of the fault are folded into upright folds or 

are only slightly overturned. 

Many smaller faults also are present in the 

study area; they include both thrust and normal 

faults, as well as ductile shear zones that are present 

in individual outcrops. These small faults and shear 

zones are not shown in figure 1 of this report because 

the paucity of exposures precludes mapping them. 

Both brittle and ductile faulting have deformed 

the southern part of the Helen-Coweeta terrane. The 

southeast side of the terrane near Dahlonega (fig. 1) is 

bounded by a fault, and the Geologic Map of Georgia 

(Georgia Geological Survey, 1976) shows a discontinuous fault and a shear zone along the terrane's southeast side. This fault and the shear zone have been 

referred to as the Dahlonega shear zone ( Crickmay, 

1952, p. 48, and Fairly, 1973, p. 693). The northwest 

side of the terrane is bounded by the Shope Fork 

fault, which was mapped by Hatcher (1976), near the 

Georgia-North Carolina boundary. The Shope Fork 

fault is folded by what appears to be F2 folds, and 

Hatcher (1976) suggests that the fault is pre- or 

synmetamorphic. However, a discordance of foliaGeneral Geology 5 
tion attitudes between the Helen-Coweeta terrane 

and the Hayesville sheet indicates that later movement along the Shope Fork fault is post-S1• Recent 

geologic mapping shows that the Shope Fork fault, 

which is probably a fault zone, locally extends southwestward toward Dahlonega (Gillon, 1982); the 

Shope Fork fault appears to join the Hayesville fault 

west of the Greenville quadrangle. 

Reconnaissance mapping in the Helen-Coweeta 

terrane shows that shear zones are present along several prominent northeast-trending topographic lineaments. The shear zone boundaries appear to be gradational, and rocks from these zones include button 

schist, mylonite, blastomylonite, and mylonite 

gneiss. These rocks exhibit deformed fabrics that 

range from microscopic to mesoscopic in size; the 

rocks display a prominent mylonitic foliation. The 

sheared rocks in the Helen-Coweeta terrane are probably the northeast continuation of sheared rocks described by Bowen (1961) in Dawson County, just 

west and southwest of Dahlonega. 

Jointing is present throughout the study area, 

but joint patterns have not been studied in detail. 

Most joints are steeply inclined and do not seem to 

have well-defined preferred strike orientations. Less 

commonly, joints are shallow dipping or are horizontal. Some thin pegmatite and quartz veins occupy 

early joint sets. 

Figure 2 is a Landsat image (Georgia Geologic 

and Water Resources Division, 1977) of the northwest part of the Greenville quadrangle; outlines of 

the major lithotectonic units are superimposed on 

the image. Distinct image patterns and lineament 

trends show a close correlation with the major 

lithotectonic units. The lineaments follow topographic and geologic features, such as aligned stream valleys or some distinct lithologic units, and many lineaments are believed to reflect prominent fracture 

zones. 

Several sets of lineament patterns, which do not 

follow the regional trends of mapped lithologic units, 

are present in the Hayesville sheet but are not evident in the adjoining lithotectonic units. A northtrending set appears to end along the Hayesville fault, 

especially in the Brasstown Bald window area. The 

same set ends along the Shope Fork fault to the south 

and does not appear in the Helen-Coweeta terrane. 

The same set continues, however, in the Hayesville 

sheet, south of the Helen-Coweeta terrane. A westsouthwest-trending set also is present in both the 

eastern and western parts of the Hayesville sheet but 

is not present in the Helen-Coweeta terrane. 

A faint east-southeast lineament trend is present in the Helen-Coweeta terrane and in part of the 

Great Smoky sheet but is not present in the Hayesville sheet. The principal lineament trends in the Inner Piedmont, southeast of the Brevard zone, do not 

have strikes parallel to lineaments in the Hayesville 

sheet. 

The contrasting lineament patterns among adjacent major lithotectonic units suggest that each unit 

was subjected to a different history of fracturing 

before emplacement along thrust faults. Alternatively, the physical makeup of each unit may have caused 

the units to yield differently to stress. 

The gently curving west-southwest-trending 

Warwoman lineament (Hatcher, 1974) forms a prominent Landsat feature (fig. 2). Although bedrock is 

concealed by surficial materials in valleys that form 

most of the lineament, a siliceous flinty crush rock is 

exposed along part of it west of Clayton, Ga. Hatcher 

(1974) reports that the lineament is a late feature-probably post-Paleozoic-and indicates that 

lithologic contacts cross the lineament without being 

offset. 

On the Landsat image (fig. 2), the Warwoman 

lineament appears to cross the Dahlonega shear zone, 

which bounds the southeast side of the HelenCoweeta terrane. A similarly trending, prominent lineament almost on strike with that of the Warwoman 

lies in the Hayesville sheet, west of the HelenCoweeta terrane. Because the lineament's trace is indistinct near the Shope Fork fault, we cannot be certain that the Warwoman is present west of the fault. 

If the Warwoman is present to the west, it appears to 

be displaced about 1.6 km to the right, along the 

Shope Fork fault. A few kilometers northeast of this 

locality, reconnaissance mapping shows a small unmetamorphosed diabase dike of probable TriassicJurassic age that also appears to be offset about 1.6 

km to the right, along the Shope Fork fault. The 

apparent similar displacements of the dike and the 

Warwoman lineament suggest post-Triassic-Jurassic 

movement along the Shope Fork fault. 

Folding and related deformation 

In the southern Blue Ridge, the major folds 

trend northeast, and their axes plunge gently northeast or southwest. These folds vary from upright to 

inclined to recumbent, and, although some of them 

verge southeast, most verge northwest. Evidence for 

polyphase folding is widespread, and the present outcrop patterns of many large structural features have 

resulted from superposed folding (Dallmeyer and 

others, 1978; Hatcher, 1974, 1978b; Wooten, 1980; 

Shellebarger, 1980). The superposed later fold phases 

have formed large-scale interference patterns of 

6 Tectonic Features and Structural Elements, Northeast Greenville Quadrangle, Ga. 
Base from Georgia Department 

of Natural Resources, Blue Ridge 

Mountains sheet. 1977. 

GSTS 

HTS 

H-C 

HF 

SFF 

BZ 

BBW 

WL 

d 

DF 

sew 

0 

EXPLANATION 

Great Smoky thrust sheet 

Hayesville thrust sheet 

Helen-Coweeta terrane 

Hayesville fault 

Shope Fork fault 

Brevard zone 

Brasstown Bald window 

Warwoman lineament 

Approximate position of diabase dike 

Dahlonega shear or fault 

Shooting Creek window 

5 10 15 20 KILOMETERS 

Figure 2. Landsat image of the northwest part of the Greenville 2-degree quadrangle and approximate boundaries of the 

major lithotectonic units of the area. 

Structural Geology 7 
domes and basins, such as the Tallulah Falls dome 

(Hatcher, 1971) and other similar structures within 

and adjacent to the study area (Shellebarger, 1980). 

Within the report area, mesoscopic structures at 

some exposures show that the rocks have been deformed by folding at least four times (fig. 3). Hatcher 

(1976 and oral commun., 1979) reports six phases of 

folding in similar rocks exposed farther east in the 

Hayesville sheet. Fold interference patterns are commonly seen at rock exposures; most of these patterns 

are similar to types 2 and 3 of Ramsay (1967) (fig. 4). 

The first generation folds (Ft) (fig. 5) are represented 

as intrafolial, rootless, recumbent isoclinal folds in 

transposed layers. Second generation folds (F2), 

which form the major folds, are steeply inclined to 

recumbent isoclinal folds, with hinges generally 

plunging gently northeast or southwest (fig. 6). The 

limbs of F2 folds have been folded locally into two 

sets of tight to open, upright to overturned flexural 

folds or crenulations. The axes of one set trends 

north-northeast;· and the axes of the other set trends 

west to northwest. Whether these folds represent separate fold phases F 3 and F 4 or whether they form part 

of a conjugate fold pair (Johnson, 1956) is uncertain. 

Evidence presented below (pg. 18) favors the latter 

interpretation. Hereafter, the two sets of folds will be 

referred to collectively as F3 folds and individually as 

F3 (northeasterly) and F3 (northwesterly). Generally, 

the axial surfaces of the F 2 folds are less steep than 

those of the later folds, but some F2 folds in the 

northwest part of the report area have steeply dipping 

axial surfaces. Statistical analyses of folds suggest 

that the flanks of some F 3 folds were gently folded by 

a later folding event or events, but axial plane cleavages have not been identified with these later folds or 

flexures. Post-F3 folding appears to be around an 

east-west axis and a less well defined north-to-northeast axis. A late episode of folding along northeasttrending axes in an area east of the study area (Hatcher, 1978b) may correspond to post-F3 folding along a 

northeast-trending axis. Flowage folds characterize 

the F1 and F2 folds, and flexure folds are the dominant fold type for the F3 folds in the report area. 

Bedding (So), metamorphic layering, regional 

foliation (St), foliation axial planar to F2 folds (S2), 

and crenulation cleavage (S3) form the principal planar structures in the report area. Bedding can be 

identified in most rock units of the Great Smoky 

sheet northwest of the Hayesville fault. Farther to the 

southeast, however, most of the bedding in rock units 

within the study area appears to be transposed into 

the regional foliation. 

Except for a diabase dike and some small pegmatite and quartz veins, all rocks in the study area 

have a pervasive planar foliation (St). This foliation 

Figure 3. Three fold phases at an exposure in Brasstown 

Creek 2.2 km east-southeast of U.S. Route 76 and south 

of Young Harris. F1 is present as small rootless isoclines; F2 

is overturned and is tight to isoclinal; F3 is an upright fold 

with an almost vertical axial plane (AP). Pencil for scale. 

is axial planar to the first generation folds (Ft) (fig. 5); 

subsequent phases of"deformation refold the regional 

foliation into later fold generations (F2 and F3). The 

second generation folds appear to have a poorly developed axial plane schistosity (S2), but the later F 3 

fold generation locally displays a strong axial plane 

crenulation cleavage (fig. 7). In this report, these surfaces (S~, S2, S3) correspond to the fold phases (F~, F2, 

F3). Foliated clasts are present in some host metasedimentary rocks in the Hayesville sheet, and their foliation is across the St foliation in the host gneiss. I 

interpret this foliation as showing that the clasts were 

probably deformed prior to their incorporation into 

the host rocks before the regional foliation S1 formed 

and, as such, may represent a pre-St deformation 

fabric. 

Crenulation cleavage (slip cleavage), although 

common, is not uniformly well developed except 

where it locally masks the earlier regional foliation 

(fig. 7). Crenulation cleavage is the most recent planar structure associated with folding. This cleavage is 

present in many pelitic units, and, where observed, it 

is axial planar to either the northwest or northeast F 3 

folds (fig. 8). Where the cleavage is well developed, F3 

folds deform the layering and the regional foliation. 

Two principal crenulation cleavage sets are present. 

One set is associated with the northeast-trending F3 

folds; the other set is related to the northwest-trending F3 folds. The northeast-striking set is much more 

common and widespread than is the northwest set. 

8 Tectonic Features and Structural Elements, Northeast Greenville Quadrangle, Ga. 
Figure 4. Type 3 fold interference pattern (Ramsay, 1967) 

at an outcrop along the Richard Russell Highway about 

0.3 km west of Hogpen Gap. F2 folds are refolded by F3 

folds. Hammer for scale. 

Figure 6. An F2 fold (axial plane (AP) dipping gently southeast) that is overturned to the northwest. View is northeastward near the Appalachian Trail in western Union 

County at an exposure 0.25 km north of Puncheon Gap. 

Hammer for scale. 

Figure 5. Outcrop showing hinge of an F1 isoclinal fold in 

siliceous metasandstone and schist in the Hayesville thrust 

sheet and also showing trend of foliation (S1). View is 

northwestward along the shore of Lake Sidney Lanier just 

south of Highway 369 at Browns Bridge. Pencil for scale. 

Locally, small crenulations associated with the 

two cleavage sets form a conjugate fold pair (fig. 9). 

These conjugate folds are rare, but they and their 

related crenulation cleavages suggest that the northwest-striking folds and the northeast-striking folds 

probably formed together as a conjugate F3 fold pair. 

As such, the F 3 folds probably represent one of the 

later sets of compressive structures to form during 

the waning stages of regional metamorphism and deformation that affected the southern Appalachians. 

Throughout most of the study area and elsewhere in the Hayesville thrust sheet, satisfactorily 

defining the chronology and the details of the macroscopic folding is difficult. The principal reasons for 

this difficulty are that ( 1) the original bedding (So) is 

transposed into the regional foliation (S1); (2) no easily distinguished marker beds exist; (3) a thick forest 

cover conceals much of the bedrock; and ( 4) original 

primary sedimentary features, such as graded bedding, are not well preserved. In the Hayesville sheet, 

the compositional layering is almost everywhere parallel to the pervasive foliation (S1), and this foliation 

is axial planar to F1 folds (fig. 5). On figure 5, foliation form lines (constructed from foliation (SI) attitudes) were drawn to depict the _general form of the 

post-F1 folds. 

Figure 10 shows the foliation (SI) form line 

trends for the report area. The two major regional 

structures are outlined; they are ( 1) the west part of 

Structural Geology 9 
Figure 7. Exposure showing So, S1, and 53 foliation. The 53 

foliation is the dominant planar feature and almost masks 

the earlier foliations. A faint 54(?) crenulation cleavage is 

also present. View is northwestward, just southeast of the 

crest of Brasstown Bald. Hammer for scale. 

the Tallulah Falls dome (Hatcher, 1971), which is 

east of the Helen-Coweeta terrane, and (2) the Chattahoochee basin and synform, which occupies much 

of the western part of the Hayesville sheet. The Chattahoochee basin is a broad, shallow-dipping, complex 

structure with a central, shallow-dipping basin that 

merges to the northeast into a synform with a northeast-trending axis. Numerous small folds with several 

distinct trends also are present. Exposures within the 

Chattahoochee basin and synform commonly show 

fold interference patterns, and in places as many as 

four and possibly five episodes of folding are recorded in the rocks. In and near the Chattahoochee basin, 

one fold set trends west-northwest, and other sets 

trend north-northeast. 

Folds in the Helen-Coweeta terrane east ofthe 

Chattahoochee synform trend northeast. 

The previously mentioned limitations (see p. 

9) to fold analysis on a macroscopic scale required 

equal area projections to make generalized interpretations of the fold chronology. Insofar as possible, the 

Figure 8. Exposure showing a rootless F2 fold and an F3 

fold with an axial planar crenulation cleavage S3. View is 

northwestward 0.35 km west-southwest of Chimney Top 

about 5 km southeast of Young Harris. Pencil for scale. 

Figure 9. Gently inclined saprolite exposure showing a 

small conjugate F3 fold pair. Exposure is located in a ditch 

next to Smyrna Road 0.15 km north of Ebenezer Church, 

in the northwest part of the Greenville quadrangle. Felt 

pen for scale. 

1 0 Tectonic Features and Structural Elements, Northeast Greenville Quadrangle, Ga. 
0 5 10 15 20 KILOMETERS 

Figure 10. Generalized structure of the report area shown by foliation 51 form lines. Regional Appalachian fold structures 

trend northeast, and later folds are superposed upon them. B, Blairsville; D, Dahlonega; H, Helen; HF, Hayesville fault; 

SFF, Shope Fork fault; DF, Dahlonega fault; BZ, Brevard zone; GSTS, Great Smoky thrust sheet; HTS, Hayesville thrust 

sheet; H-C, Helen Coweeta terrane; BBW, Brasstown Bald window; SCW, Shooting Creek window; TFD, Tallulah Falls 

dome. 

Structural Geology 11 
study area was divided into structurally homogeneous areas (fig. 11), and the linear and planar fabric 

elements for each area were statistically analyzed by 

using an equal area net. In the fold analyses that 

follow, the S, attitudes are represented by a five-digit 

numeral. The bearing of the strike of fabric elements 

is given by the first three digits, and the dip or plunge 

value by the next two digits. The symbol "nS" refers 

to a great circle of best fit through poles of measured 

S surface segments. The normal to nS is represented 

by ~S, which is the statistically defined axes of folding (Turner and Weiss, 1963). 

Fold Analyses 

Areal 

This area (see fig. 11) occupies the southwest 

part of the Hayesville sheet northwest of the HelenCoweeta terrane. Here the S, foliation attitudes generally strike east-west and have moderate north dips 

that reflect the structural attitudes along the southern 

boundary area of the Chattahoochee basin (fig. 1 0). I 

observed few F2 folds; they are overturned to the 

southeast and are reclined to recumbent. Their axes 

AREA II 

AREA V 

AREA IV 

~ 

~ 

\AREA Ill'\ 

\ 

East part ofthe 

Hayesville thrust sheet 

0 5 KILOMETERS 

L______j 

Figure 11. Structural areas in northwest Greenville 

quadrangle that were used for statistical analyses of fold 

events. 

trend northeast. Figure 12A is an S, pole diagram for 

area I and shows projections of F2 fold axes. The 

concentrations of poles to S, suggest a weak S, girdle 

with a ~S, of 060/16 °. The single s, pole maxima 

concentration is interpreted to show that significant 

post-F 2 deformation did not noticeably affect the 

rocks in area I. Together with the observed F2 folds, 

the concentration suggests that the S, surface in this 

area was deformed by F 2 folds that are overturned to 

the southeast. The plotted fold axes are close to the 

statistical axial plane 086/33 o; this proximity suggests that F2 folds are overturned to the southeast. 

Area II 

Area II (see fig. 11) lies just north of area I in 

the Hayesville thrust sheet. The wide dispersal of S, 

poles along a broad girdle (fig. 12B) suggests that area 

II probably has undergone considerably more post-F2 

deformation than has adjacent area I and that a single ~S, probably does not characterize this area. Besides the F2 regional folds whose axes trend northeast, there are also FJ folds with northwest- and 

northeast-trending axes. I interpret an S, pole diagram for area II (fig. 12B) as showing a trimodal 

distribution for S, pole concentrations. This distribution resulted from a spread of a maxima for northwest-dipping surfaces into two submaxima, possibly 

during FJ (northwest) folding. The 313110° ~S, is 

close to the plotted mean attitude for axes of 17 

northwest-trending FJ folds (fig. 12B). The projections of the mean attitude for axes of 15 southwestand northeast-plunging FJ fold axes have different 

orientations than does the ~S, 07211 oo. However, the 

217/05 o ~S, strike is close to the average strike for 

the axes of northeast-trending F2 and F3 folds, except 

it plunges gently southwest instead of northeast; note 

that some measured FJ folds plunge southwest and 

that others plunge northeast. The ~S, po~itions for 

the southeast- and northwest-dipping S, surfaces suggest that the segment of the Chattahoochee synform 

in area II is folded into upright folds along northeasttrending axes. The general northeast-southwest strike 

of S, contrasts strongly with the east-west S, trend in 

area 1. 

Area Ill 

In area III (see fig. 11 ), the regional schistosity 

(S,) strikes northeast and dips primarily to the northwest, but some other attitudes are also present. Besides the generally northeast-striking major F2 fold 

axes, both northeast- and northwest-trending FJ folds 

are present. In places throughout the report area, F2 

and the northeast-trending F3 folds have almost par12 Tectonic Features and Structural Elements, Northeast Greenville Quadrangle, Ga. 
/351 239/14° • 

A. Area I 

EXPLANATION 

+ F2 fold 

C. Area Ill 

EXPLANATION 

AP 086/33°N 

{351 060/16° 

110 pts 

23% 

18% 

13% 

6% 

1% 

91 pts 

13% 

10% 

6% 

3% 

1% 

+ Mean altitude for 15 southwest- and 

northeast-plunging FrF3 folds 

~::,. Mean altitude for 17 northwestplunging F3 folds 

7TS, 

+ 

E. Area V 

EXPLANATION 

+ Altitude for F2-F3 folds 

66 pts 

9% 

6% 

3% 

1% 

/351 072/1 oo 

291 pts 

6% 

4% 

3% 

2% 

1% 

B. Area II 

EXPLANATION 

~::,. Mean altitude for 17 northwest- and 

southeast-plunging F3 folds 

+ Mean altitude for 15 southwest- and 

northeast-plunging F3 folds 

/351 312/30° 

D. Area IV 

EXPLANATION 

+ Mean altitude for 14 northeast- and 

southwest-plunging F2-F3 folds 

~::,. Mean altitude for 12 northwest- and 

southeast-plunging F3 folds 

133 pts 

5% 

4% 

3% 

1% 

f3S1 062/1 oo 

++ 

F. Northwest subdivision 

EXPLANATION 

+ F3 fold areas 

-i 

+ 

+ 

83 pts 

8% 

7% 

5% 

1% 

Figure 12. Contoured equal area projections of poles to S, and F2 and F3 fold attitudes for areas shown in figure 11. 

Structural Geology 13 
allel axes, and, depending on the rock exposure, one 

cannot always differentiate an F2 from an F3 fold. 

Figure 12C is an S, pole diagram that also gives the 

mean attitudes of undifferentiated F2 and F3 folds in 

area III. The S, pole maxima concentrations are 

somewhat elongate and define a 1tS, girdle with a ~S, 

of 239/14 o. The pole concentrations are locally dispersed away from the girdle, especially near the maximum pole density. I believe that the maximum density for S, poles approximates S, attitudes prior to F3 

strain, but the dispersal of the pole concentrations at 

several points along the girdle may reflect post-F2 

deformation that is .related to the F3 strain. The effects of post-F2 strain in area III, however, do not 

seem to be as widespread as in area II. Figure 12C 

shows that, although some surfaces dip southeastward, most of the surfaces in area III dip to the 

northwest. This northwest dip suggests that, in this 

part of the Chattahoochee synform, the northeasttrending folds are overturned to the southeast. 

Area IV 

Area IV (see fig. 11) contains a wide variety of 

S, orientations. Figure 12D contains plots of poles to 

S, that form a 1tS, girdle with a ~S, of 312/20°. The 

poles to S, are widespread in the diagram, but a bimodal distribution is indicated by two maxima. Also 

shown in the diagram are the mean trends of fold 

axes and their plunges for the undivided F2 and 

northeast-trending (F J) folds, as well as the northwest-trending (F3) folds. 

The bimodal spread of the 1tS, girdle appears to 

be the result of post-F2 deformation. Because the ~S, 

and the mean fold projections for the northweststriking FJ folds are similar, I interpret the post-F2 

strain as resulting from deformation associated with 

FJ (northwest-trending) folds. 

AreaV 

The regional schistosity in area V (see fig. 11) 

almost uniformly strikes northeast and dips primarily to the northwest, but in some areas it dips to the 

southeast. The rocks in this area have been folded 

several times. I observed some type 2 and 3 interference patterns (Ramsay, 1967) in the field within area 

V. The F, folds are small rootless isoclinal folds in 

the foliation; F2 folds plunge to the southwest. These 

F2 folds, which appear to form part of the major folds 

with northeast-trending axes, are reclined and overturned to the southeast. A few asymmetric northeasttrending (F 3) folds also were observed. 

The S, pole concentrations in area V (fig. 12E) 

define a 1tS1 girdle with a ~S, of 012/05°. One high 

density pole maxima, which plots together with a less 

dense point maxima, forms a bimodal S, pole distribution along the girdle. Figure 12£ also shows the 

projections of axes of northeast undivided F2 and F3 

folds that plunge either to the northeast or southwest. 

The F2 and FJ fold axes have very similar trends. I 

interpret the bimodal distribution as reflecting F2 

folding. The irregular scatter from the 1tS1 girdle may 

be a result of FJ (northwest) folding. However, I did 

not observe FJ northwest-trending folds within area 

v. 

The northwest subdivision 

The northwest subdivision (see fig. 11) is north 

and west of the Hayesville fault and southeast of the 

Murphy syncline (fig. 1A). Rocks of the Great Smoky 

thrust sheet underlie the subdivision. Structurally, 

the rocks of this area are overturned. Most of the 

rock units and the included foliations (S,) dip variably southeast, but some rock units dip northwest. 

Fold interference patterns (Shellebarger, 1980) show 

the rocks have been multiply folded. Figure 12F, 

which gives the orientations for S, in the northwest 

area, shows a 1tS, girdle with a closely spaced bimodal 

maxima distribution and a ~S, of 062/10 o. The main 

concentration of points containing the two maxima 

probably represents the least deformed S, surfaces on 

the southeast flank of the Murphy syncline. The 

spread of the maxima, as well as the distribution of 

points away from the girdle, probably represents late 

stage or post-F2 folding. The plots for northeastplunging F2 folds are widely dispersed, also possibly 

due to post-F2 deformation. 

Shellebarger (1980) reported that rocks in the 

study area northwest of the Hayesville fault have 

been folded several times. Wooten (1980) also indicated that rocks northwest of the Hayesville fault just 

north of the report area are multiply deformed. Both 

Wooten and Shellebarger report that folds equivalent 

to the F2 folds of this report have steeply inclined 

axial surfaces and are overturned to the northwest. 

The Helen-Coweeta terrane 

The Helen-Coweeta terrane area (see fig. 11) is 

underlain by rocks whose foliation (S,) trends northeast, parallel to the strike of the terrane. After the 

formation of foliation during F,, the rocks were 

folded around northeast-trending axes, and the foliation now dips either northwest or southeast. Within 

the terrane, differentiating between F 2 and F J folds is 

difficult. Both F2 and FJ folds have axes that strike 

northeast and plunge gently northeast, and some F2 

folds also plunge south-southwest. 

Figure 13A illustrates the S, orientations within 

the Helen-Coweeta terrane. Plots of S, pole concen14 Tectonic Features and Structural Elements, Northeast Greenville Quadrangle, Ga. 
s, 031/10° 

• 

A. 

8 1 plots in 

Helen-Coweeta terrane 

c. 

Plots of s, altitudes in 

east part of Hayesville sheet 

125 pts 

6% 

4% 

3% 

1% 

327 pts 

8% 

7% 

5% 

3% 

2% 

1% 

1rS3_...,.... E. 

B. 

F2 and F3 fold axes in 

Helen-Coweeta terrane 

D. 

S, northeast-trending folds 

70 pts 

8% 

6% 

4% 

137 pts 

12% 

9% 

7% 

4% 

1% 

83 northwest-trending folds 

Figure 13. Contoured equal area projections of various planar and linear features in northwest Greenville quadrangle. 

trations have a bimodal distribution and form a nS1 

girdle whose ~S1 is 031110°. Figure 13B shows the 

bimodal distribution of undivided F2 and F3 fold axes. The ~s~ of figure 13A would plot within the northeast maxima for the fold axes. I interpreted this as 

showing that the bimodal sl pole distribution probably resulted from either F2 or F3 deformation or, 

more probably, from both. Additionally, the northeast maxima is close to the F2 and FJ (northeasttrending) plots elsewhere in the study area. 

Structural Geology 15 
East part of the Hayesville sheet 

The east part of the Hayesville sheet lies just 

east of the Helen-Coweeta terrane (see fig. 11) and 

covers that part of the Hayesville sheet southwest of 

the Tallulah Falls structural dome (Hatcher, 1971) 

where the rock units and S, surfaces strike primarily 

northeast. Most of the dips are to the southeast, but 

northwest-dipping foliation is not uncommon. An 

orientation for poles to S, is shown in figure 13C. The 

poles form a distinct 1tS, girdle with a bimodal maxima distribution and a ~S, of 045/05 o. The orientation of the girdle and the position of the 1tS1 are 

similar to those of the Helen-Coweeta terrane (fig. 

11 ), where the maximum density concentrations are 

more widely dispersed along the 1tS, girdle. Because 

fabric orientations in both the Helen-Coweeta terrane and Hayesville sheet (east) are similar, I believe 

that the S, surfaces in both areas have a similar postS, deformation history. 

Brasstown Bald window 

Hartley and Penley (1974) and Shellebarger 

( 1980) described parts of the Brasstown Bald area 

(see fig. 11). Within the Brasstown window, the regional foliation has been deformed by F2, F3, and 

later folding. Fabric element diagrams (fig. 14A-D) 

were made for this area; these include S-pole diagrams, as well as plots of other fabric elements from 

rocks along a ridge northwest of Brasstown Bald. 

An S, pole orientation for the entire window is 

shown in figure 14A. Here the S, pole plots define a 

1tS, girdle with a ~S, of 03 7/24 o and define a statistical axial plane that contains the ~S,. Figure 14B 

shows the axial plane of a representative F2 fold, its 

axis, and the axes of several other F2 and F3 folds. 

The ~S, (fig. 14A) for the window is reasonably similar to the F2 fold axes. The ~S, and F2 fold axes, 

together with the axial plane and the S, pole maxima, 

suggest that the F2 folds are overturned to the westnorthwest. 

Crenulation cleavage (S3) 

Figure 13D shows the orientations of crenulation cleavage for the northeast-trending (FJ) folds 

throughout the study area. Pole concentrations show 

a somewhat dispersed maxima within a broad zone 

of low pole concentrations that define a questionable 

girdle. The distribution of poles to SJ surfaces (axial 

planar to the northeast-trending folds) represents a 

wide variety of SJ attitudes. The majority of these S3 

surfaces, however, dip to the southeast and suggest 

that most of the axial planes of the northeast-trending folds have similar orientations. The spread of the 

maxima away from the girdle may represent post-F3 

folding about an east-west axis or may be due to 

cleavage fans about F J axes. 

Figure 13£ shows the S3 crenulation cleavage 

orientations for the northwest-trending (F3) folds for 

the entire study area. Pole plots to S3 give a 1tS3 girdle 

with a ~SJ of 093/05 o. The pole concentrations along 

the girdle have a bimodal distribution and probably 

reflect post- FJ folding about an east-west axis. 

Figure 14C illustrates the SJ cleavage pole concentrations in the Brasstown Bald area for the F3 

northwest-trending (FJ) folds that define a 1tS3 girdle 

with a ~SJ of 119/30°. The pole density concentrations form a bimodal distribution, and their separation suggests post-FJ deformation, possibly along a 

west-trending axis. 

Figure 14D shows the poles to S3 cleavage associated with northeast-trending (FJ) folds in the Brasstown Bald area; these plots of SJ cleavage define a 

statistical axial plane at 033/34 ofor the maximum S3 

pole concentration. The ~S, position for the window 

plots on the edge of a cluster of several F2 and F3 fold 

axes (fig. 14B) that are close to the plotted axial 

plane-. The maxima concentration, together with the 

axial plane and FJ fold axes plots, suggests that here 

the northeast-trending FJ folds plunge northeast and 

are overturned to the northwest. The well-defined S3 

maxima density suggests minimal post-S3 

deformation. 

The bimodal distribution of poles to SJ crenulation cleavage for northwest-trending (FJ) folds (figs. 

14C and 13E) suggests post-FJ folding along east-west 

axes. The pole concentrations (fig. 14D) for FJ northeast-trending fold cleavages in the Brasstown Bald 

area, however, do not suggest significant post-FJ deformation, even though post-FJ folding of similar 

cleavages along west-trending axes throughout the 

study area is suggested by figure 13D. This lack of 

agreement presents a problem. If both the northwestand northeast-trending (F J) folds form a conjugate 

pair, their associated rocks also should show evidences of similar post-F3 deformation. Several explanations for this apparent difficulty are possible. ( 1) 

The measured S3 surfaces of northeast-trending folds 

in the Brasstown Bald area might have been taken 

from a position or positions on a relatively ondeformed part of a fold that would have similar attitudes. (2) The measured crenulation cleavages might 

be associated with a fold that is younger than the 

northwest-trending (FJ) folds; that is, a fold that has 

not been previously recognized. (3) The number of 

plotted measured surfaces was insufficient and did 

not indicate the post-FJ folding. 

In summary, the post-F, fold analyses show orientations of the principal folds within specific areas 

of the report region. In the Great Smoky thrust sheet 

16 Tectonic Features and Structural Elements, Northeast Greenville Quadrangle, Ga. 
{3S1 037/24° 

A. 

Brasstown Bald window S1 

c. 

Brasstown Bald S3 (northwesttrending) altitudes 

• 

+ 

E. 

Brasstown Bald ridge 

EXPLANATION 

+ Intermediate compression axis 

• Minimum compression axis 

49 pts 

18% 

14% 

8% 

2% 

34 pts 

17% 

4% 

2% 

• Maximum compression axis 233/10° 

B. 

Brasstown Bald F2 axis, its axial plane, 

and the axes of other F2 folds 

D. 

Brasstown Bald S3 (northeasttrending) altitudes 

+ 

• 

F. 

14 pts 

60% 

45% 

2% 

1% 

Northwest part of Greenville quadrangle 

EXPLANATION 

+ Intermediate compression axis 

• Minimum compression axis 

• Maximum compression axis 200/25° 

Figure 14. Contoured equal area projections of various planar and linear features in the Brasstown Bald area and 

northwest Greenville quadrangle. 

northwest of or beneath the Hayesville fault, the regional F2 folds are mostly overturned to the northwest, and their axial surfaces are steeply inclined. 

The F 3 strain appears to be reflected in the varied 

distribution of F2 fold axes and in the diverse attitudes of sl surfaces. 

Structural Geology 17 
In the Hayesville thrust sheet southeast of the 

Hayesville fault, the F 2 folds are reclined to recumbent and, depending on their location with reference 

to the Chattahoochee basin (fig. 10), have variable 

orientations that reflect considerable FJ (northwestand northeastward) strain. S, attitudes vary widely. 

In contrast, in both the Helen-Coweeta terrane and 

the southeastern part of the Hayesville thrust sheet, 

the F2 fold axes generally strike northeast and have 

steeply dipping axial surfaces. These terranes also appear to have been subjected to post-F2 deformation 

that did not change the orientation of F2 fold axes 

greatly. Throughout the report area, FJ fold axes 

strike west to northwest and north to northeast, and 

their axial surfaces range from gently to steeply inclined. Although statistical evidence suggests post-FJ 

folding about east-west axes, field observations indicate only gentle warping about east-west axes. I recognize no significant post-FJ folding in the study area. 

F3 fold analysis 

Ramsay ( 1962) used some structural elements 

of conjugate folds to determine the principal stress 

directions in the formation of a conjugate fold system. He discussed a procedure to determine the three 

principal stress axes for the deforming forces responsible for conjugate folds. Tobisch and Fiske (1976) 

made regional structural interpretations of the central Sierra Nevada from maximum compression directions (maximum stress of Ramsay) of conjugate 

folds. Ramsay and Tobisch and Fiske indicated that 

the maximum compression directions probably lie 

parallel or subparallel to the surfaces being folded. 

Several crenulation cleavage sets are exposed 

along a ridge north of Brasstown Bald in the Brasstown Bald window. Orientations of the axial planes 

of both sets of crenulation folds were plotted on a 

stereonet. These data were used to obtain a statistical 

orientation for the principal compression directions 

(Ramsay, 1962). Figure 14£ shows the statistical 

compression axes for the conjugate (F J) folds in the 

Brasstown Bald window. The maximum compression 

direction is 233/10° and is subparallel to the regional 

foliation on the ridge north of Brasstown Bald. A 

similar study was made of conjugate folds near Ebenezer Church, which is 8 km northwest of Blairsville 

and 1 km east of the quadrangle boundary in thenorthwest part ofthe study area. Figure. 14F shows a 

statistical maximum compression direction for the 

northwest area at 200/25 o. This direction almost lies 

in the regional foliation for that area. These southwest-striking compression directions are not exactly 

parallel, and the slight angular discordances between 

them are probably due to preconjugate deformation 

that gave the rock units varying orientations. The 

southwest trend of the maximum compressive stress 

axis for the conjugate folds is almost parallel to the 

trends of the regional F 2 and F 3 fold hinges in the 

report area (see figs. 12, 13, and 14). 

In the southern Appalachian Blue Ridge Mountains, the regional folds trend northeast-southwest. 

This trend suggests that the maximum compression 

axes of the stress ellipsoid had a northwest-southeast 

orientation during regional deformation. It has previously been shown that the maximum compression 

direction for the conjugate folds in part of the report 

area was to the southwest. This orientation suggests 

that the stress field during conjugate folding was oriented almost normal to that which was prevalent during regional deformation. Tobisch and Fiske (1976) 

reported on a similar situation in the central Sierra 

Nevada. To explain this anomaly, they suggested a 

model where the conjugate structures resulted from 

forces that developed during an elastic recovery stage 

that occurred after the main folding event. This necessitated shortening parallel to the regional structural trends. Therefore, applying the Tobisch-Fiske 

model in the report area, the stress field that produced the regional northeast-trending structures was 

not rotated almost 90° to obtain the conjugate folding maximum compression. Instead, the compression 

direction for conjugate folding probably resulted 

from forces that developed during elastic recovery 

after the main deformation. 

SUMMARY AND CONCLUSIONS 

The rocks underlying the northwest part of the 

Greenville 2-degree quadrangle form parts of three 

major lithotectonic units. They are the Great Smoky 

thrust sheet, the Hayesville thrust sheet, and the 

Helen-Coweeta terrane. Each of these lithotectonic 

units is characterized by lineaments with distinct 

trends; each is allochthonous and bounded by faults. 

The Hayesville fault and its northern continuation separate two major terranes in the Appalachian 

18 Tectonic Features and Structural Elements, Northeast Greenville Quadrangle, Ga. 
Mountain chain-the Great Smoky thrust sheet and 

the Hayesville thrust sheet (Rankin, 1975; Hatcher, 

1976, 1978; Williams, 1979). The Hayesville fault is 

pre- or synmetamorphic and is folded. The fault 

forms the contact around several windows in the 

Hayesville sheet. 

The Shope Fork fault is probably a pre- or 

synmetamorphic feature, but some evidence indicates a late episode of movement along part of the 

fault. Patterns on Landsat imagery suggest possible 

right lateral offset of the Warwoman lineament along 

the Shope Fork fault. Mapping suggests that a postmetamorphic diabase dike of probable Triassic-Jurassic age(?) is similarly offset along the Shope Fork. 

The Helen-Coweeta terrane is bounded by 

faults, and numerous topographic lineaments within 

the terrane are associated locally with mylonitic 

rocks. These lineaments correspond with aeromagnetic lineaments in rocks of the Helen Group 

that extend southwest beyond the study area. Bowen 

( 1961) also described a band of sheared rocks that are 

on strike with the Helen Group a few miles to the 

southwest, in Dawson County. Therefore, shear 

zones in the Helen Group may be part of a larger 

shear zone; that is, the Dahlonega shear zone in 

northeast Georgia. 

Several major lithotectonic units in the study 

area are characterized by distinctive lineament 

trends on Landsat images. These lineaments, which 

are not the northeast-trending lineaments seen on 

topographic maps, are believed to reflect prominent 

fracture zones in the lithotectonic units. Two interpretations of the lineament trends are possible: ( 1) 

each major lithotectonic unit had different physical 

characteristics that caused the unit to yield differently to stress or (2) the lineaments were present in each 

thrust sheet prior to emplacement into their present 

positions. 

The majority of folds in the terrane northwest 

of (below) the Hayesville fault are F2 folds with 

northeast-trending axes. These folds are overturned 

to the northwest, and their axial surfaces are steeply 

inclined. F 1 folds are not apparent northwest of the 

Hayesville fault, but F3 folds are present and superimposed upon the F2 folds. 

Southeast of the Hayesville fault, most F2 folds 

have northeast-trending axes. In this area, the F2 

folds are overturned, but their axial surfaces are either gently inclined or nearly horizontal. The imprint 

of later folding has variably deformed F2 axial surfaces. The F3 (northeast- and northwest-trending) 

folds are well developed locally, and their axial surfaces range from steeply to gently inclined. In places, 

rocks show type 2 and 3 fold interference patterns. 

These patterns result from F3 folds deforming the 

almost flat-lying F2 and F1 folds. Figure 15 is a schematic diagram of a folded regional foliation surface 

between the Hayesville fault and the Helen-Coweeta 

terrane; the diagram shows the generalized form of 

the F 2 and F 3 folds. 

In the report area, the relations between the 

directions of maximum compression for the conjugate and regional folds seem to agree with the structural requirements of the conjugate folding model of 

Tobisch and Fiske (1976). The analysis of conjugate 

folds shows that maximum compression directions 

for conjugate folding nearly parallel the regional foliation, as shown in figure 12E and F. 

If all the northeast- and northwest-trending FJ 

folds in the report area are part of a conjugate fold 

pair, then one less folding event is required to explain 

the fold structures present. This simplifies structural 

interpretation and eliminates the need for an almost 

90° rotation of the force field after regional F2 deformation. Further work is necessary to determine 

whether conjugate folding extends beyond the report 

area. 

With the inclusion of the conjugate folds, the 

following fold phases occur in the report area: 

F1-Rootless recumbent to reclined isoclinal folds 

that trend northeast. F 1 folds lie in the regional 

foliation and may be coplanar with F2 folds. 

F2-Steep to recumbent isoclinal folds that form major folds. F2 folds deformed S1 regional foliation, probably occurred after peak metamorphism, and rarely have well-developed axial 

plane foliations (S2). 

F3-Upright to slightly inclined conjugate fold sets 

that trend northeast and northwest. F 3 fold sets 

have planar crenulation cleavage in pelitic units 

and probably are late metamorphic. 

F4-Post-F3 folding about east-west and north-northeast axes, as suggested by statistical fold analyses. Field studies, however, have not identified 

axial planar cleavages associated with these later folds. 

Summary and Conclusions 19 
~ 

a 

-· I 

~ 

l 

f 

i 

!1. 

I 

z 

i 

C') 

I. 

f 

-i 

l 

i 

lf" 

~ 

11(1. 

,J~ 

~~ 1-;. 

:7\ 

' ' ' "' ' 

..,. 

Le 

' ' 

~ 

,J~ 

'to 

~~ 

~ ?'~ 

4_"\ 

~~ 0~ 

~ (('ll 

1/ 

~~,.o"'~ ~'2. 

Figure 15. A deformed S, surface in part of the Hayesville thrust sheet between the Hayesville fault and the Helen terrane. The generalized form of the F1 and F, 

folds is indicated. 
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22 Tectonic Features and Structural Elements, Northeast Greenville Quadrangle, Ga.