gsa data repository 2019126 from the alleghanian to the ...chong ma, david a. foster, willis e....
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GSA Data Repository 2019126 From the Alleghanian to the Atlantic: Extensional collapse of the southernmost Appalachian orogen Chong Ma, David A. Foster, Willis E. Hames, Paul A. Mueller, Mark G. Steltenpohl Analytical Methods Eighteen granitic samples were collected from Alleghanian and Ordovician plutons in the Piedmont (sixteen samples of >5 kg each from outcrop) and coastal plain basement (two samples from drill cores) of Georgia, northern Florida, and eastern Alabama. Sixteen biotite, eight muscovite, and one hornblende separates were obtained from these samples utilizing standard density and magnetic techniques following crushing, sieving, washing, and air drying. Minerals were handpicked to >99% purity (see the grain size of each separate in Table DR1) and cleaned using ethanol in an ultrasonic bath before irradiation at the U.S. Geological Survey TRIGA reactor in Denver, Colorado, United States.
40Ar/39Ar thermochronology was performed in the Noble Isotope Mass Analysis Laboratory at Auburn University. Irradiated biotite and muscovite along with monitor minerals (GA1550 Biotite of 98.79 ± 0.54 Ma and FC Sanidine of 28.02 ± 0.16 Ma, Renne et al., 1998) were hand loaded into a copper planchet under a stereomicroscope with 30‒45 grains averagely in each hole. Gas was extracted from the mineral separates by incremental heating with a 50 W Synrad CO2 IR laser attached to an automated extraction line and then into a 90-degree sector, 10-cm radius mass spectrometer. SAES AP-10 getters were used for purification of the gas. Blanks were measured after every 5‒7 unknows. The measured 40/36 of Air was 288.0 ± 1.5. Isotopic data were collected on a single electron multiplier detector and are corrected for interfering nuclear reactions, blank, and mass discrimination. Isotopic data were reduced using an in-house Excel spreadsheet and the ages (±1σ error) were calculated in Isoplot v. 3.75 (Ludwig, 2012). Plateau ages are defined by three or more continuous steps that include ≥ 50% of the 39Ar released and give concordant ages at the 1σ level. If the criteria of a plateau age are not met, an integrated age is calculated for those consecutive and concordant (within 1σ) steps based on weighted average of the data with errors at the 95% confidence level.
References for Data Repository: Dallmeyer, R.D., 1978, 40Ar/39Ar incremental-release ages of hornblende and biotite
across the Georgia Inner Piedmont; their bearing on late Paleozoic‒early Mesozoic tectonothermal history: American Journal of Science, v. 278, p. 124-149.
Dallmeyer, R.D., 1988, Late Paleozoic tectonothermal evolution of the western Piedmont and eastern Blue Ridge, Georgia: Controls on the chronology of terrane accretion
and transport in the southern Appalachian orogen: Geological Society of America Bulletin, v. 100, p. 702-713.
Dallmeyer, R., Hess, J., and Whitney, J., 1981, Post-magmatic cooling of the Elberton Granite: Bearing on the late Paleozoic tectonothermal history of the Georgia Inner Piedmont: The Journal of Geology, v. 89, p. 585-600.
Dennis, A.J., 2016, Structural analysis of the Kiokee belt and its framing elements: Savannah River transect, in Doar, W.R., III, ed., Gold, Structures, and Landforms in Central South Carolina: Geological Society of America Field Guide 42, p. 37-51.
Foster, D.A., Mueller, P.A., Heatherington, A., Wooden, J.L., Daitch, P., and Ma, C., 2012, Alleghanian magmatism in the southern Appalachians: Implications for Pangean tectonic models: Geological Society of America Abstracts with Programs, v. 44, no. 4, p. 23.
Hatcher, R.D., 2010, The Appalachian orogen: A brief summary, in Tollo, R.P., Bartholomew, M.J., Hibbard, J.P., and Karabinos, P.M., eds., From Rodinia to Pangea: The Lithotectonic Record of the Appalachian Region: Geological Society of America Memoir 206, p. 1-19.
Hibbard, J., Van Staal, C., Rankin, D., and Williams, H., 2006, Lithotectonic map of the Appalachian Orogen, Canada-United States of America: Geological Survey of Canada Map 2096A, scale 1:1 500 000.
Huebner, M.T., Hatcher, R.D., and Howard, C.W., 2011, Geologic overview of the Inner Piedmont at the northeast end of the Pine Mountain Window, in Huebner, M.T., and Hatcher, R.D., eds., The Geology of the Inner Piedmont at the northeast end of the Pine Mountain window: Georgia Geological Society Guidebooks, v. 31, p. 1-26.
Layfield, N.T., 2009, Permian to Cretaceous evolution of the Piedmont along the Alabama-Georgia coastal plain unconformity [M.S. thesis]: Auburn, Alabama, Auburn University, 145 p.
Lin, Q., 2015, Spatial-temporal distribution of the Alleghanian magmatism in the southern Appalachians: Implication of the assembly of supercontinent Pangaea [M.S. thesis]: Gainesville, Florida, University of Florida, 160 p.
Ludwig, K.R., 2012, User's manual for Isoplot 3.75: A geochronological toolkit for Microsoft Excel: Berkeley Geochronology Center Special Publication No. 5, 75 p. http://www.bgc.org/isoplot_etc/isoplot/Isoplot3_75-4_15manual.pdf.
Maher, H.D., Dallmeyer, R.D., Secor, D.T., and Sacks, P.E., 1994, 40Ar/39Ar constraints on chronology of Augusta fault zone movement and late Alleghanian extension, Southern Appalachian Piedmont, South Carolina and Georgia: American Journal of Science, v. 294, p. 428-448.
McClellan, E.A., Steltenpohl, M.G., Thomas, C., and Miller, C.F., 2007, Isotopic age constraints and metamorphic history of the Talladega belt: New evidence for timing of arc magmatism and terrane emplacement along the southern Laurentian margin: The Journal of Geology, v. 115, p. 541-561.
McDonald, W.M., 2008, 40Ar/39Ar ages of muscovite from the western Blue Ridge and Talladega belt, Georgia and North Carolina [M.S. thesis]: Auburn, Alabama, Auburn University, 114 p.
Renne, P.R., Swisher, C.C., Deino, A.L., Karner, D.B., Owens, T.L., and DePaolo, D.J., 1998, Intercalibration of standards, absolute ages and uncertainties in 40Ar/39Ar dating: Chemical Geology, v. 145, p. 117-152.
Sagul, D.A., 2016, Constraining the age and petrogenesis of the Zana and Kowaliga gneisses, eastern Blue Ridge, Alabama [M.S. thesis]: Gainesville, Florida, University of Florida, 150 p.
Steltenpohl, M.G., Heatherington, A.L., Mueller, P.A., and Miller, B.V., 2005, Tectonic implications of new isotopic dates on crystalline rocks form Alabama and Georgia, in Steltenpohl, M.G., ed., New perspectives on southernmost Appalachian terranes, Alabama and Georgia: Tuscaloosa, Alabama, Alabama Geological Society, p. 51-67.
Steltenpohl, M.G., and Kunk, M.J., 1993, 40Ar/39Ar thermochronology and Alleghanian development of the southernmost Appalachian Piedmont, Alabama and southwest Georgia: Geological Society of America Bulletin, v. 105, p. 819-833.
Steltenpohl, M.G., Goldberg, S.A., Hanley, T.B., and Kunk, M.J., 1992, Alleghanian development of the Goat Rock fault zone, southernmost Appalachians: Temporal compatibility with the master decollement: Geology, v. 20, p. 845-848.
Steltenpohl, M.G., Schwartz, J.J., and Miller, B., 2013, Late to post-Appalachian strain partitioning and extension in the Blue Ridge of Alabama and Georgia: Geosphere, v. 9, p. 647-666.
Supplemental Figures: Figure DR1. 40Ar/39Ar age spectra of muscovite, biotite, and hornblende reported in this study. In each plot, the horizontal line above the age spectrum shows the steps used to calculate the cooling age (1σ error).
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
SAOBH-2Integrated age
= 308.4 ±� 0.9 MaIncludes 83.1% of the 39Ar
Ben HillBt
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
GGS3001Plateau age = 298.2 ± 0.4 Ma
Includes 100% of the 39Ar
Hbl Seminole
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
SAOTCR-2Plateau age = 277.8 ± 0.5 Ma
Includes 99.98% of the 39Ar
Ms Town Creek
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
SAOPAL-1Plateau age = 297.6 ± 0.4 Ma
Includes 81.8% of the 39Ar
Ms Palmetto-Tyrone
175
200
225
250
275
300
325
350
0.0 0.2 0.4 0.6 0.8 1.0
MC13SAO-9Plateau age = 271.8 ± 0.4 Ma
Includes 78.6% of the 39Ar
Ms Modoc
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
AHGA-9Plateau age = 254.4 ± 0.3 Ma
Includes 80.3% of the 39Ar
Ms Elberton
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
AHGA-4
�Plateau age = 293.7 ± 0.5 Ma
Includes 69.8% of the 39Ar
Ms Stone Mountain
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
DF11-104B
Includes 53.6% of the 39Ar
Ms Indian Springs
Plateau age = 289.8 ± 0.4 Ma
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
SAOPAL-1Plateau age = 313.3±1.2 Ma
Includes 81.9% of the 39Ar
Palmetto-TyroneBt
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
AHGA-4Ingerated age= 301.2±� 1.2 Ma
incl. 32.1% of the 39Ar
Stone MountainBt
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
MC13SAO-20Plateau age
= 288.9 ±�0.4 MaIncludes 85.8% of the 39Ar
PanolaBt
175
200
225
250
275
300
325
0.2 0.4 0.6 0.8 1.0
DF11-104BIngerated age= 299.4 ± 0.5 Ma
incl. 29.9% of the 39Ar
Indian SpringsBt
Motts
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
TH-2Plateau age
= 284.4 ± 0.4 Maincl. 94.8% of the 39Ar
Bt
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
MC13SAO-24APlateau age
= 280.0 ± 0.6 MaIncludes 86% of the 39Ar
HospilikaBt
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
TCK-1Plateau age = 275.6±1.0 MaIncludes 63.2% of the 39Ar
Town CreekBt
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
SPAR-2Plateau age = 277.6±1.0 MaIncludes 91.9% of the 39Ar
SpartaBt
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
AHGA-8Plateau age = 269.3 ± 0.4 Ma
Includes 62.2% of the 39Ar
ApplingBt
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
MC13SAO-9Ingerated age= 276.1 ± 0.5 Ma
incl. 41.8% of the 39Ar
ModocBt
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
SIL-1Plateau age = 276.2 ± 0.4 Ma
Includes 88.1% of the 39Ar
SiloamBt
250
275
300
325
MC13SAO-4APlateau age = 302.3 ± 0.5 MaIncludes 79.7% of the 39Ar
Danburg
0.0 0.2 0.4 0.6 0.8 1.0
Bt
175
200
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
MC13SAO-3Plateau age = 252.9±1.0 MaIncludes 89.9% of the 39Ar
ElbertonBt
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
CALHOUN-1Plateau age = 283.8 ±�0.7 Ma
Includes 98.6% of the 39Ar
CalhounBt
Age
(Ma)
Cumulative 39Ar Fraction [Ages are shown with 1σ errors, Ms = Muscovite, Bt = Biotite, Hbl = Hornblende]
Ms Zana
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
DEX023Plateau age = 319.6 ± 0.6 Ma
Includes 77.1% of the 39Ar
Ms Kowaliga
225
250
275
300
325
350
0.0 0.2 0.4 0.6 0.8 1.0
JKG029 Plateau age = 314.8 ± 0.5 Ma
Includes 90.9% of the 39Ar
Bt Kowaliga
225
250
275
300
325
0.0 0.2 0.4 0.6 0.8 1.0
JKG029 Plateau age = 316.2 ± 0.5 Ma
Includes 71.7% of the 39Ar
Fig. DR1
Figure DR2. Locations of available 40Ar/39Ar dates of hornblende, muscovite, and biotite shown on the geologic map of the southernmost Appalachians (modified from Hibbard et al., 2006 and Hatcher, 2010). New ages reported in the current study are outlined by boxes and those previously published dates are from Dallmeyer (1978), Dallmeyer et al. (1981), Dallmeyer, (1988), Steltenpohl et al. (1992), Steltenpohl and Kunk (1993), Maher et al. (1994), Steltenpohl et al. (2005), McClellan et al. (2007), McDonald (2008), Layfield (2009), Steltenpohl et al. (2013), and Dennis (2016).
Columbu
s
Atlanta
Macon
August
a
Carters
ville
Between
Dahlon
ega
Siloam
Milledg
eville
Sparta
Butler
Phenix
City
Tuskeg
ee
Auburn
Pine M
ounta
in
The Roc
k
GriffinW
edow
ee
Heflin
Tallap
oosa
Sylacau
ga
Alexan
der C
ity
Wetu
mpka
Opelik
a
Dadev
ille
Lincoln
ton
Tallad
ega
Athens
Elberto
n
35N
83
Alabama
Florida
Georgia
South Carolina
Alabama
Georgia
34
32
31
34
86 85 84 83
8385
86W
GR
EA
T S
MO
KY
F
AU
LT
50 km
North
PN
MT
MT
HP
BH
PM
IS
SL
TC
SP
AP
MD
DB
SM EB
SN
CH
284.4±0.2 B
283.8±0.7 B
298.2±0.4 H
280.0±0.6 B
277.8±0.5 M275.6±1.0 B
254.4±0.3 M252.9±1.0 B
297.6±0.4 M313.3±1.2 B
301.2±1.2 B293.7±0.5 M
289.8±0.4 M299.4±0.5 B
271.8±0.4 M276.1±0.5 B
269.3±0.4 B
277.6±1.0 B
302.3±0.5 B
276.2±0.4 B288.9±0.4 B
308.4±0.9 B
Sparta
362±4H,302±1M
273±5H,236±4M,237±5B
276±4H
274±5H,246±5M,240±4B
267±5H,237±4B
296±2H,288±4H
339±3H,306±1M
343±4H,308±2M
350±5H,306±2M
349±4H
322±5H
332±5H
313±2M
311±1M308±1M
311±2M
312±2M
310±1M 307±3M
308±1M
324±4H
345±5H 341±7H
323±4H
337±3H
334±4H
318±2M,305±1B
325±4H
325±5H
331±4H
235±4B
240±4B
240±4B
241±4B
278±.4M 278±.4M
272±.7M
278±.5M
275±.6M
241±4B
227±5B
330±1H
320±3H
347±3H
329±2M
287±1M
296±3M
278±1M
283±3M
285±1M
293±3H
291±3H
293±3H
289±3H
297±3H,286±3M
292±1H,284±1B
327±2M
327±2M
311±2B
329±3M
329±1M
323±4M
322±1M
322±2M
330±2M
338±1M
339±1M
316±1M
329±2M 351±3M
336±2M
349±3H,318±2B
350±2H,311±2B
327±5H,297±2B
322±4H,299±2B
314±2H
296±3H
307±2H,289±4B
306±3H,286±2B
283±2M,281±4B
261±3B
251±2B
236±2B
244±2B
301±3B
321±2M
334±2H
Names of dated plutons:
Minerals and dating methods:H: Hornblende (Ar/Ar)
B: Biotite (Ar/Ar)M: Muscovite (Ar/Ar)
Ben Hill
Panola
Elberton Danburg
Siloam
Appling
Sparta
Indian Springs
Town Creek
Stone Mountain
Palmetto-Tyrone
BHCalhounCH
PM
IS
TCSP
AP
ModocMotts
HospilikaHP
MTMD
SL
Seminole SN
DB
PN
SM
EB
Zana
KowaligaKL
ZN
Suwannee terrane
Charleston terrane
Brunswick magnetic anomaly
314.8±0.5 M316.2±0.5 B
319.6±0.6 MZN
KL
Fig. DR2
Figure DR3. Low-angle, southeast-dipping normal-sense shear zone with high-angle normal faults in the hanging wall in the Uchee terrane (32°36'45.8"N; 84°57'02.9"W). (A) Cross-section with no vertical exaggeration (VE). (B) Central part of the low-angle normal shear zone, photo was taken in 1988. (C) A representative high-angle normal fault with bended Alleghanian gneissic layers showing normal faulting. (D, E) Photomicrographs of oriented samples with mica fish, sigma-type porphyroclasts, and S-C fabrics, showing hanging wall down-to-the-southeast. (F) Slickenlines on the fault surface of the low-angle normal shear zone. (G) Slickenlines on the fault surface of a high-angle normal fault; note the steps indicating normal faulting. (H) Structural data of the low- and high-angle normal faults and the hosting gneissic layers. See outcrop location on Figure 1.
Mean fault plane of low-angle normal shear zone
North
West
Step
Mean lineation of low-angle normal shear zone
poles to gneissosity, hanging wallpoles to gneissosity, footwall
poles to high-angle normal fault
lineations of high-angle normal fault
poles to low-angle normal shear zone
High-angle normal faults
High-a
ngle
norm
al fau
lt
Low-angle normal shear zone
Light-colored gneiss
lineations of low-angle normal shear zone
Line
atio
n
Line
atio
n
SC
C
SE
A
B C
D F
E G
H
SE 0 12m
SE
SE
SE
1 cm
1 cm
NW
NW
NW
NW
NW
VE=1
Low-angle normal shear zone
Fig. DR3
Table DR1. Sample location, mineral size, and summarized 40Ar/39Ar ages of the granitic plutons in the study.
Pluton name Sample name Mineral
Average grain size
(µm) 40Ar/39Ar Age
(Ma) 1σ
(Ma) Sample location Zircon U-Pb age (Ma)
Palmetto-Tyrone, GA SAOPAL-1 Ms 300-400 297.6 0.4 N33°33.847'/W84°45.363' 334, Foster et al. (2012)
SAOPAL-1 Bt 800-1800 313.3 1.2 N33°33.847'/W84°45.363' Stone Mountain, GA AHGA-4 Ms 600-1000 293.7 0.5 N33°44.973'/W84°08.652' 337, Lin (2015)
AHGA-4 Bt 500-600 301.2 1.2 N33°44.973'/W84°08.652' Ben Hill, GA SAOBH-2 Bt 800-1500 308.4 0.9 N33°42.991'/W84°34.013' Panola, GA MC13SAO-20 Bt 1000-1500 288.9 0.4 N33°37.336'/W84°10.589' Indian Springs, GA DF11-104B Ms 500-1000 289.8 0.4 N33°15.745'/W83°56.270' 312, Huebner et al. (2011)
DF11-104B Bt 500-1000 299.4 0.5 N33°15.745'/W83°56.270' 312, Huebner et al. (2011) Elberton, GA AHGA-9 Ms 500-1000 254.4 0.3 N34°05.810'/W82°55.408' 292, Lin (2015)
MC13SAO-3 Bt 500-1500 252.9 1.0 N33°57.335'/W83°03.362' Danburg, GA MC13SAO-4A Bt 1000-2000 302.3 0.5 N33°53.023'/W82°38.652' Siloam, GA SIL-1 Bt 300-500 276.2 0.4 N33°32.243'/W83°04.142' Modoc, GA MC13SAO-9 Ms 400 271.8 0.4 N33°36.766'/W82°30.782' 303, Lin (2015)
MC13SAO-9 Bt 600 276.1 0.5 N33°36.766'/W82°30.782' 303, Lin (2015) Motts, AL TH-2 Bt 350-600 284.4 0.2 N32°32.998'/W85°09.887' Hospilika, AL MC13SAO-24A Bt 300-800 280.0 0.6 N32°30.306'/W85°11.476' Town Creek, GA SAOTCR-2 Ms 500-1000 277.8 0.5 N33°09.085'/W82°05.348' 295, Lin (2015)
TCK-1 Bt 500-1500 275.6 1.0 N33°09.095'/W83°05.862' Sparta, GA SPAR-2 Bt 800-1000 277.6 1.0 N33°17.508'/W82°55.988' Appling, GA AHGA-8 Bt 600-1000 269.3 0.4 N33°31.353'/W82°15.345' Seminole, GA GGS3001 Hbl 350-650 298.2 0.4 GGS well #3001 Calhoun, FL CALHOUN-1 Bt 150-300 283.8 0.7 FGS well #16298 Zana, AL DEX023 Ms - 319.6 0.6 N32°44.802'/W 86°8.876' 466, Sagul (2016) Kowaliga, AL JKG029 Bt - 316.2 0.5 N32°54.815'/W85°50.062' 465, Sagul (2016) JKG029 Ms - 314.8 0.5 N32°54.815'/W85°50.062' 465, Sagul (2016)
GA—Georgia; AL—Alabama; FL—Florida.
Table DR2. Complete step-heating 40Ar/39Ar data of hornblende, muscovite, and biotite from granitic plutons in the southernmost Appalachians. (See Excel file for data)