Detrital zircons and sediment dispersal in the Appalachian foreland GEOSPHERE

25 Pages·2017·4.1 MB·English

Research Paper
GEOSPHERE
Detrital zircons and sediment dispersal in the Appalachian foreland
GEOSPHERE; v. 13, no. 6 William A. Thomas1, George E. Gehrels2, Stephen F. Greb3, Gregory C. Nadon4, Aaron M. Satkoski5, and Mariah C. Romero6
1Emeritus, University of Kentucky, and Geological Survey of Alabama, P. O. Box 869999, Tuscaloosa, Alabama 35486-6999, USA
doi:10.1130/GES01525.1 2Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA
3Kentucky Geological Survey, University of Kentucky, Lexington, Kentucky 40506-0107, USA
12 figures; 3 supplemental files 4Department of Geological Sciences, Ohio University, Athens, Ohio 45701-2979, USA
5Department of Geoscience, University of Wisconsin, Madison, Wisconsin 53706-1692, USA
6Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, USA
CORRESPONDENCE: geowat@uky .edu
CITATION: Thomas, W.A., Gehrels, G.E., Greb, S.F.,
Nadon, G.C., Satkoski, A.M., and Romero, M.C., 2017,
ABSTRACT INTRODUCTION
Detrital zircons and sediment dispersal in the Appala­
chian foreland: Geosphere, v. 13, no. 6, p. 2206–2230,
doi:10.1130/GES01525.1. Seven new detrital-zircon U-Pb age analyses along with a compilation The late Paleozoic Appalachian orogen along eastern North America (Fig. 1)
of previously published data from Mississippian–Permian sandstones in the long has been recognized as the dominant source of clastic sediment spread-
Received 6 March 2017 Appalachian foreland (total n = 3564) define the provenance of Alleghanian ing cratonward into orogenic foreland basins (e.g., King, 1959; Thomas, 1977)
Revision received 10 July 2017
Accepted 27 September 2017 synorogenic clastic wedges, as well as characterize the detritus available to and beyond, into intracratonic basins and farther across the North American
Published online 19 October 2017 any more extensive intracontinental dispersal systems. The samples are from Midcontinent (e.g., Gehrels et al., 2011). The late Paleozoic orogen represents
the cratonward-prograding Mauch Chunk–Pottsville clastic wedge centered the final assembly of supercontinent Pangaea as a result of a succession of
on the Pennsylvania salient, the cratonward-prograding Pennington-Lee clas- Ordo vician–Permian (Taconic, Acadian, and Alleghanian) accretionary pro-
tic wedge centered on the Tennessee salient, and a southwestward-d irected cesses along the Neoproterozoic–Cambrian Iapetan rifted margin of Lauren-
longitudinal fluvial system along the distal part of the foreland. Grenville-age tia and the Cambrian–Ordovician passive margin (e.g., Hatcher et al., 1989a;
detrital zircons generally are abundant in all samples; however, ages of Williams, 1995). The orogen includes the Precambrian Grenville province of
the Taconic and Acadian orogenies are dominant in some samples but are supercontinent Rodinia assembly, synrift and passive-margin rocks of the
minor to lacking in others. Taconic–Acadian ages are dominant in the Mauch Laurentian margin, and Ordovician through Permian synorogenic rocks and
Chunk–Pottsville clastic wedge, in parts of the longitudinal system, and in accreted terranes of the Appalachian and Ouachita orogenic belts (Fig. 1). The
the upper part (above Middle Pennsylvanian) of the Pennington-Lee clastic objectives of this article are to characterize the detrital-zircon populations of
wedge; but they are minor to lacking in the lower part (Upper Mississippian– the late Paleozoic synorogenic clastic wedges within the Appalachian foreland
Lower Pennsylvanian) of the Pennington-Lee clastic wedge. New Hf isotopic and to evaluate the contributions of the various components of the prove-
analys es show a similar distinction between the two clastic wedges, sup- nance within the Appalachian orogen. This characterization of Appalachian
porting an interpretation of differences in provenance contributions during detrital-zircon populations provides a template to determine possible Appala-
the early stages of basin filling. U-Pb ages and Hf isotopic ratios also indicate chian contributions to more distal intracontinental dispersal systems.
that the Mauch Chunk–Pottsville transverse dispersal fed the northern part
of the longit udinal system. A few samples in the distal southwestern part of LATE PALEOZOIC SYNOROGENIC SEDIMENTARY DEPOSITS
the Mauch Chunk–Pottsville clastic wedge and adjacent parts of the longitu-
dinal system have unusually large populations of grains with Superior and Mississippian–Permian Alleghanian synorogenic clastic deposits vary sig-
Central Plains ages. The relative distance and isolation of these samples from nificantly along the orogen. Between the New York and Alabama promontories,
the Canad ian Shield, which is the primary source of Superior and Central two late Paleozoic classic synorogenic clastic wedges filled foreland basins cen-
Plains zircons, indicates likely recycling from synrift sediment, passive-mar- tered on the Pennsylvania and Tennessee embayments (Fig. 2). From the New
gin strata, or Taconic–Acadian clastic wedges. Among the lesser components York promontory northward to Newfoundland, late Paleozoic clastic sedimenta-
are a few grains with ages that correspond to Iapetan synrift igneous rocks tion along the Appalachian orogen filled fault-bounded pull-apart basins along
and also to Pan-African–Brasiliano components of Gondwanan accreted ter- a regional system of dextral strike-slip faults (Fig. 1) (e.g., Thomas and Schenk,
For permission to copy, contact Copyright ranes. Synorogenic zircons of the Alleghanian orogeny are very rare (seven 1988; van de Poll, 1995). From the Alabama promontory westward along the
Permissions, GSA, or [email protected]. grains in the total of 3564). Ouachita and Marathon embayments, late Paleozoic synorogenic clastic wedges
© 2017 Geological Society of America
GEOSPHERE | Volume 13 | Number 6 Thomas et al. | Appalachian detrital zircons 2206
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Research Paper
90W 80W 70W 60W
EXPLAApNpAaTlaIcOhNian-Ouachita thrust front Neemwbfoauynmdelna50ntNd
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emMbaaryamtheonnt promToexnatosryN 900W 200 40085W600 km (f2(afrf0lrroooo1mn0mmg) ;T HTtlhohhiobceomab mOtaairouasdnsa e ecsath t no aiatdfll a.. ,f, Sa 1o2uc9r0hlo8t0es9g7n be;w kn;H ,Hi at(1haft9rction8chm8h et;erh ,vrT e,2a h 20nloa01 m01tde0)e;a ) P t;sP rab,ao la2eclsl0eo,e 0 z1om6o9f) i9et.c h5n GMe)t;r maAaayrnpai tdposi masuoiltfauelsicstn ohl iebnfi a aeGsnsh r-ioeonOfnw uilvnaasi tl ctelthehh -iPeetaa a gnll oeteohoc rrratzouhtocsieioktcr sn nfc r ( oolAfarnfosp tttmp hi(cace loHw ammacethapdcipihagl eneeidnrss,
100W 95W Figure 2. B.R.—Blue Ridge external basement massif; M.R.—Midcontinent rift system.
GEOSPHERE | Volume 13 | Number 6 Thomas et al. | Appalachian detrital zircons 2207
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B Mauch Chunk–Pottsville clastic wedge
A
PA NW SE
e
F ccPLadiiFpFsTltPninhtloAiiniesoihuagggrs e neetae—Sbscp.uut t tt tiAilh4userrlr(ieinPiogeecrcv rspepxe ep sl cr Fih ppsetlandr2a3ailE eeosalgpen.l; toe ad dv liauh ssao(mnifrii( rnAiyr mydlcbncuareyddleshe)o lv mn e uiit1oin iwanrcPMeanaa.efetb nafemnn Ttlaso ctaeyt inaa h)lhawtrep rts mlinre;(sih Tcyo e rsign sa tlrtoobansO arhiuiyebmwnftcel ssiHus lwil(ane voteastrse—lroin a en a p)cet fdSabf n f hmr cO aeafanoiaw1ietopsarnrtphanra rrearenbMadsllion to,yeondeh en wgg(as l;lacPgdodof olseurrce)eee wc Waiol.nschtps sinsad nmehNgn ,ltVnrsa soec iii eunaCo iat—b t itnFpsumtisnimdthyonihgeoe dWg,i u bnw cdop tordia.nottan ee wl u nhee1eknotiisratndnd)l)eess–t-f-ll.. AL TN longi5tu1d8in5al syst2em6O1KH71-YG4169A57320111P0en7ni29nclgW-tao4st2nVi-cV L1Aeweedge 114Mauch 1Ch3uclnak1s–ti6Pc otwtsevdilgle ULwp MPeisnsSnW1MSatounchy GChaupnk432–PPHBorliunitntetscosventiotlolenn eclaMLswdULt i cwPpP 1 e we1PP4nneeenMnPdnrmoganteuNt3sNcEvhSi llChe7ahruPonrnok-4PcNteoSnrhn22ain10rgoGWtno-ranSes-eLhneinee111g 9ct87olanCulsoUptowippcn11e eeMw6r3rm eiMMsSTadsouhougnmangeorohbpnnl igMgnSaagthnh Re.elulaan
Virginia; KY—Kentucky; VA—Virginia; TN— Md Penn
Tennessee; AL—Alabama; GA—Georgia. 12 7upper Raleigh
(soBcf a)s laDem)i atpgolre as smhitomewsa (ttcihrcoe sc ssrt osrsaestc itgsioerancpsti hoairnce s pa (opnspoirttoi oxtoni- local source N Pennington-Lee clastic wedge Lw Penn 11109loBwPoeottrco Ramha olCenrigteahesk
mately along each of the blue and red 200 km NW SE Up Miss
arrows in A). Numbers are the same as EXPLANATION OF SYMBOLS FOR SAMPLE LOCATIONS Md Penn 6 Princess #7
in A; color fills and outlines of numbered 1 KY-21-SG Stony Gap 5 Grundy-Norton
circles and rectangles match those of the 2 KY-18-CB Corbin 2Corbin
arrows in A. Perm—Permian; Penn—Penn- 23 OH-4-SN Sharon (north) Lw Penn 6Lee Pennington-Lee clastic wedge
syl vanian; Miss—Mississippian; Up— 4 OH-1-SS Sharon (south) SW NE
Upper; Md—Middle; Lw—Lower. 5 VA-1-GN Grundy-Norton
6 KY-19-PR7 Princess No. 7 coal Md Penn 15 Cross Mountain
7 WV-1-PR Proctor 12Montevallo 8 Sewanee
6 previously published, listed by number in Figure 4 Lw Penn (local source) 5 Raccoon Mountain
of deep-water turbidites (Fig. 1) have relatively small wavelength-to-amplitude are more quartzose (Becker et al., 2005; Grimm et al., 2013). On the basis of
ratios (Arbenz, 1989; Viele and Thomas, 1989). The shallow-marine to deltaic paleocurrents and sandstone petrography, the relatively lithic sandstones of
clastic wedges in the Pennsylvania and Tennessee embayments have large the transverse drainage systems generally have been interpreted as being
wavelength-to-amplitude ratios; these clastic wedges are the focus of this article. derived from unroofing of the internal belts of the Appalachian orogen south-
The Mauch Chunk–Pottsville clastic wedge is centered on the Pennsylvania east of the foreland basins (Thomas, 1966; Meckel, 1967; Davis and Ehrlich,
salient of the Appalachian thrust belt (Pennsylvania embayment of the rifted 1974; Edmunds et al., 1979; Donaldson and Shumaker, 1981; Donaldson et al.,
margin), and the Pennington-Lee clastic wedge is centered on the Tennessee 1985). Quartz pebbles are common in Lower Pennsylvanian polymictic con-
salient of the thrust belt (Tennessee embayment of the rifted margin) (Figs. glomerates. In Pennsylvania, a southeastward increase in quartz-p ebble sizes
1, 2) (Thomas, in Hatcher et al., 1989b). Sediment-dispersal patterns in both indicates a source along the southeast side of the foreland basin in the Penn-
clastic wedges reflect generally semi-radial transverse drainages across the sylvania embayment (Meckel, 1967). In contrast, on the basis of paleocur-
foreland basins toward the craton (Fig. 2) (e.g., Meckel, 1967; Thomas, 1977). In rents, as well as more quartzose composition and concentrations of quartz
contrast to the transverse drainages, south- to southwest-directed longitudinal pebbles, Lower Pennsylvanian sandstones in the longitudinal drainage sys-
(orogen-parallel) drainage characterized the distal parts of the basins in the tem have been interpreted as derived from the Canadian Shield or northern
Early Pennsylvanian (Fig. 2) (Archer and Greb, 1995; Grimm et al., 2013). Appalachians (Siever and Potter, 1956; Edmunds et al., 1979; Chesnut, 1994;
Sandstones of the transverse drainage systems in the proximal parts of Archer and Greb, 1995; Greb and Chesnut, 1996; Grimm et al., 2013), as has
the clastic wedges generally are more lithic, whereas those of the Early Penn- one sandstone in the proximal part of the Mauch Chunk–Pottsville clastic
sylvanian longitudinal drainage system along the distal parts of the basins wedge (Robinson and Prave, 1995).
GEOSPHERE | Volume 13 | Number 6 Thomas et al. | Appalachian detrital zircons 2208
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Table S1. Zircon U-Pb geochronologic analyses by laser ablation–multicollector–inductively coupled plasma mass spectrometry: Mississippian–Permian sandstones DETRITAL-ZIRCON SAMPLING AND ANALYTICAL METHODS 232, and 238 were measured with Faraday detectors, whereas the smaller 202
Isotope ratios Apparent ages (Ma)
KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY-----------------------------------------2222222222222222222222222222222222222222211111111111111111111111111111111111111111-----------------------------------------SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSAGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGn-a---------------------------------------—SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSlyppppppppppppppppppppppppppppppppppppppppSsooooooooooooooooooooooooooooooooooooooootiotttttttttttttttttttttttttttttttttttttttts n1317225221521212232312223322121282512147059976642883325451438741108613858101446y3375070726403815364652811161 Gap Sa(pnpUdms642141112221451111211111121312t7445873488944602566967330211246425574259)o6342110829438445114919577499865071262522ne 22M11121111008116121328883111525326246222846157138e648790144941815415100827716512256779508732mPP1192125803974254527611297130480920750076bbb6400093077210481991329916454046518684330195327045785221939903915099810786e0409277r—U37/T° h021110111120121111261121121211111202221109........................................0541976532851110142101745892380403854099' 26221111111111111111111111111111111111111111.007776777787877778778777877766996878877676176........................................'6677896918557772680673060143612915116972'PP N1031059843483328874080547940060516879569bb0064276825077184573338672038500501028073,** 240521981719078538710074248086765394372782°( %38 ±2' 1s22433222233225533152212211145522221132225)........................................0698195811029606285305979996520007668621.2''2 2W0000000000000000000000000000000000000000037........................................54555555555568455644444555555567745555566PU6373336686702925736676222211914551114610b5424517920926827034498515735812460783099**4856474053904878898494851376552444682876(% ±2s2454333323323654352223322356522223214322)........................................8553190697682280789804269000879555393768220000000000000000000000000000000000000000036........................................00000000000000000000000000000000000000008P5676777777966668666666666667778966667776Ub9948233344737796001236778892358104883569*4065533423772631451119150141896318242336(% ±2s1321121221122111112111122122212112112112)........................................9606629018479868870388733964691852715571ecrorr0000000000000000000000000000000000000000or........................................r.783456655644544536665567736346776675656402803264742304401096277778894921022796392203634444444446344453333344444444455344444448P7362555566091233778891122234574670225673Ub2037155611079112882847814428817364565843*........................................*2463099958995894062373522979733529264039(Ma± 1111111129766988985670179667567799764101681958817s........................................)00898373025828245430840358961337428569292203734444444464445333334444445443444444445445P8535565671533268899222328712812232788645Ub8946761481055167780968004007183432693302........................................*0683417456014206301025095890023777637306(Ma± 1111111111221111111111221111111128599969403033040042577110078630202123005s........................................)96691746897407326030341084190264893781732200764444445445644444454423444344425566444554PP8537861275541568695796966911376430193927bb3994356599118448774202281942491700554265........................................**2297041850360555540344734457322814078754(Ma1111111± 408556466465434677433646251444432025168423945278676915323804581155373383150237837s........................................)9877891775862160272270873695393146906311Be(sM3444444444433346344533344444444444554444t a7625555663378810912377912222234567460357a)2371556110182880791268471445628881734354g........................................63099958499267970e94262359958420732233593(Ma± 1111111127966988986757567795660719989764106187811s........................................)0089837304300582455843548896769922813223C(1111111111o%3000060001798988888887999999998898789899n)0862304752705152149990103591388162960632c........................................2845587447067451784796907173303635011892 hM(ddFFiaeegiigvttsurrTse.ii rotti 2eaasb )sslld.e- i zzoTep3iicnrh rpaccu einocoam onndnnlee– s l4genPw a rceti ar stardeei mnno idsaasri pvga.al yeananIsnrin dless ai aaszyabed lnnil dnedooa cifrlbft lyooiudyozgrde en detced,rne o i pUptitmcuhro- esrPpcsov blaifaitur orisoaogiustgmnhioscea ln tsyltwh h a(aepFeegn uid segdAbtg . rplt Heaio4spstf) hi a.egi ieslnsTraodta hcatt pehhodbh iepaldaii itscnacAah t s pda ofuaop arp cortatca riglmUeea (esscF-enePshi gi,nbfio ar.st ananaa3m tg m)oib oefefrapn s otslf heomoiinnesrf aitpaAgtnehnnrrnceeeodaaln vuulp ly 2iyndro1z0sede eu4esvdsds si)i i o, osnaw cutan tow1iesm tnb5 ghessp erl asviaalasme eltmtili ne wo1pPdstn laesb e swsgo .i inrfwces atooareitetm tigh1oo mr2 pnpat l heesteoisea otni e snnil unlatpyser s eiewpgeoadurrnika t rfi wshtgci r oeoiwtithnndhuiegt nfhoi ,rlot a noeants mrhn pesced,er ot ahufilauakesr ns3sii nsent 0ewygrg r ss, ios tta a.ehdf nfTm2 e dt(h0lhfa. o e aeSyμ r a3 mm ltbac0os aqa sbelecu lerdkeni asgerosim lrugtfaoifror yuea(dn f tniion toardhrs mo psa buw)ute,a t retticfignherkfreeee--.
evolution of drainage systems, as well as by distribution separately for trans- An average of 275 analyses was conducted on each sample with one U-Pb
1Supplemental Table S1. Zircon U-Pb geochronologic
verse dispersal into the two clastic wedges and the longitudinal system in the measurement per grain. Grains were selected in random fashion; crystals were
analyses by laser ablation–multicollector–inductively
coupled plasma mass spectrometry: Mississippian– distal part of the basin. rejected only if they contained cracks or inclusions or were too small to be
Permian sandstones. Please visit http:// doi .org /10 analyzed. The use of high-resolution BSE and CL images provided assistance
.1130 /GES01525 .S1 or the full-text article on www
in grain selection and spot placement.
.gsapubs. org to view the Supplemental Table. Sample Collection and Processing
Data reduction was accomplished using the “agecalc” Microsoft Excel
spreadsheet, which is the standard Arizona LaserChron Center reduction
Approximately 12 kg of medium- to coarse-grained sandstone was col-
protoc ol (Gehrels et al., 2008; Gehrels and Pecha, 2014). Data were filtered for
lected from a restricted stratigraphic interval for each detrital-zircon sample
discordance, 206Pb/238U precision, and 206Pb/207Pb precision as indicated in the
and then processed utilizing methods outlined by Gehrels (2000), Gehrels et al.
notes in Supplemental Table S1 (see footnote 1). Data are presented on nor-
(2008), and Gehrels and Pecha (2014). Zircon grains were extracted using tra-
malized age-probability diagrams (Fig. 3), which sum all relevant analyses and
ditional methods of jaw crushing and pulverizing, followed by density sepa-
uncertainties and divide each curve by the number of analyses such that all
ration using a Wifely table. The resulting heavy-mineral fraction was further
curves contain the same area. Age groups are characterized by the ages of
purified using a Frantz LB-1 magnetic barrier separator and heavy liquids. A
peaks in age probability and by the range of constituent ages.
representative split of the zircon yield was incorporated into a 2.5-cm epoxy
mount along with multiple fragments of the U-Pb primary standard Sri Lanka
SL-F and Hf standards R33, Mud Tank, FC-1, Plesovice, Temora, and 91500.
Hf Isotopic Analysis
The mounts were sanded down to ~20 μm, polished to 1 μm, and imaged by
back-scattered electrons (BSE) and cathodoluminescence (CL) using a Hitachi
Hafnium isotopic analyses were conducted utilizing the Nu multicollector
3400N scanning electron microscope (SEM) and a Gatan Chroma CL2 detec-
LA-ICPMS system at the Arizona LaserChron Center following methods re-
tor system at the Arizona LaserChron SEM Facility (www .geoarizonasem. org).
ported in Cecil et al. (2011) and Gehrels and Pecha (2014). An average of 45 Hf
Prior to isotopic analysis, mounts were cleaned in an ultrasonic bath of 1%
analyses was conducted per sample; grains were selected to represent each of
HNO and 1% HCl in order to remove surficial common Pb.
3 the main age groups and to avoid crystals with discordant or imprecise ages.
TaObrled eSr2: Hf isotSoapmic pdleata: Missis(s1i7p6pYiba n+– P17e6rLmu)i a/n 1 7s6aHnfd (s%to)nesVolts Hf 176Hf/177Hf ± (1σ) 176Lu/177Hf176Hf/177Hf (T) E-Hf (0)E-Hf (0) ± (1σ)E-Hf (T) Age (Ma) CL images were utilized to ensure that all Hf analyses are within the same
KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY---------------------------------------------111111111111111111111111111111111111111111111888888888888888888888888888888888888888888888---------------------------------------------CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB---------------------------------------------1111111111213221112222122555244456666511137336560051561555225532200300978754167869343256418772518566665158932367481 11212221131211211213111111121111649479766869964307563740022955098385913201004.............................................479726705588883868481346156160246913943771732 322333232443424253343323232251232333644355554.............................................329119016426951563837989470689064445163064532 000000000000000000000000000000000000000000000.............................................222222222222222222222222222222222222222222222888888888888888888888888888888888888888888888220201222222221222221222212111112222221222022339797220143149862313014191809295602320431822315672997512286254692215530368130578756113861327186815731635345372029245195840704069337503 000000000000000000000000000000000000000000000.............................................000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000247233333223342724424354333334334433222333232512556494836407363470118641472470957852955706 000000000000000000000000000000000000000000000.............................................000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000010001011010120100001100101020101000000100000402583665267016587466048232328193843867276668029889413882317546616578681898911389125202284403619333017129297714758377923376038016499765 000000000000000000000000000000000000000000000.............................................222222222222222222222222222222222222222222222888888888888888888888888888888888888888888888022220122222221222122211212221111221222220222937228720313049862303199401508918620022348121306899063149964142092929442031468444596405159290563307827359068595035715150267972697934945 -----------------------------------------61116312121-21215-21232-1622325316211116212104944676477562330891350061124385080567437380.....3........................................86968036615324225791570709603255627908701062 010112111101111121101011111111111111110011010.............................................949243242086324056694178932135234230298282919 --11111--------11677127196466996547274774366573361200681101020......................................623708416230865993698573607386......637.012559348338 2111131111111211111211121112112111644444444447002007123141515627756677407017030165432684562897108748196660356004723840311699188719255324731828451275410807149538448812431 i(TUbals2naλ0uthy7-tv  Prte Pe=ohlebUAdar blmem,v1s nr m a9aeeGAaeon3nrdlanre y dii atEtuzaonse bolo2bmemcre0lnisfl6ahmaa -P)a 2tlcl rt3ei b eiocooL8foaUr,nonann ondatus d–o2m anepoiugl nndrolf sceeCdt d iztghoidnueh oi2eicr gdcrn3cch t2otlH o o TweircnAvo neh-oi eecnlnC t,uEuoih laotyeenxslh l tlilnti eotcheyncehtocgreseerge tus yrilo Narls a p ( fr ioFwu on lNPeafI rtwIC hduro Ci2anoP w 0PptdI4dtMhnPMo .lailaesbvanSySst is, p r.dm M c eu2uluU0oarma4tacalsHil lclthlmeemir ghzranczeo,iaait- ntrdaop n sscse n rsu. Foososm dran su reA orgpu 2r ac0nrc)elh2d rt.eaHic iyeoTac ltgsolyroynhitou tf l ea(e clcmmste lo hoiseGcsle eueltow2ceto nrIt aS cCraoyetrt ues xPporI(rpi CcMiLresccpisPAd om S falMf eon-on.IetmCrdhSrar uP 2e mlel0yacoM 8nsPatsereteS ebbaadasr)--l, speid1ddeilsnu7tvpoilr6oareitHiotsmietntmioiHilfoacclud/naot1lpa et a7li un1fiyin7noro7cnHn 6dt f unioHaa icfustf nlsnoyfpo,a m/ iT mp1lrntttot7ashmh iod7cdpt bHeesap a aol ε frte Ule otH s e oar 2cxfi-sSaf tf oPσttiie atne2oinb)itrrso r hdnvt eo(n sipeisro nnva ae ipeaitei lUtrpde,r Fr n petoe ua-i(htfgPsCr rlaaoeeteetubHllheoxc nr stcodUitpeaitsanrmue rnRuimfo3eodgoas)e.tsn hpr lte usy(O o l Bieeiisess2fsnnaodii s ) snz sc u2 tm aigiahhhr–nvprcn o eo2ei iHaoetdεw .s sn5pHbnrf t. n aa ra feeeacetC sls vwytpnrsn io yostsesaoaihmsi tlinllstuolhyet.aot a,ptfs e otni alale2iotdlneor ivhs0nz urt nie eeoaH0n nH,r d t8w faiiiSfHw nti)o geass.luf- nha vge rIpo( siuino r2crspnfeantelσhooeulr ml e)εt r aratr.opH mni stenaoHpiiaf tpvlaen(isl flcreF lne yea ippw ivtsgtsdsnalroooeioe.aeals l trtntTuc3tl oesayhoait)tp s ss,iefbil oaii no e owcltznnces ch inShhrd eaeSd c(ouetv 2 foie2HHoronpa.nd2e4rff----.
t
2Supplemental Table S2. Hf isotopic data: Mississip- Table S11 for specific methods used for each sample), depending on grain size. grams, which are based on a 176Lu/177Hf ratio of 0.0115 (Vervoort and P atchett,
pian–Permian sandstones. Please visit http://d oi. org
For larger grains, a 30-μm-diameter spot was used, and masses 206, 207, 208, 1996; Vervoort et al., 1999).
/10 .1130/ GES01525. S2 or the full-text article on www
.gsapubs. org to view the Supplemental Table.
GEOSPHERE | Volume 13 | Number 6 Thomas et al. | Appalachian detrital zircons 2209
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20
15
10 Figure 3. Relative U-Pb age-probability
plots (lower panel) and Hf evolution dia-
DM
gram (upper panel) showing results from
5 analyses of Mississippian–Permian
sandstones in the Appalachian foreland
(analytical data and location informa-
0 tion are in Supplemental Tables S1 [see
CHUR footnote 1] and S2 [see footnote 2]).
Lower panel: Relative age-probability
–5 plots for seven analyzed samples. Vertical
–10 creuvsotlalutio n coATohfp leppo aorpletaleodcnt hsbti iaaaannlr sedp sarco norvedleop Nnrr aeocnsrotecdhene tAdp t mrhaoesev r iiiancngca eenFs i grc aiurnanr tegto hen2es.:
blue—Mauch Chunk–Pottsville clastic
–––122505 AlleghanianAcadian Pan-African–Brasiliano & Iapetan synrift Grenville Granite-Rhyolite Central Plains Penokean &Trans-Hudson Eburnian &Trans-Amazonian Superior SCAGGGuepraraepnnpnnetdarivrlteaiaieolrlcl /-ePrhRA l&hiava iyaPnnoleosslnintoekean wgU(bptdoyarpeape ndsptieecaygenl me)rap.— ; nboTpraeolihaondllyenstn—s setage lhPv:sai ea te rεnut(er H2anad .gifcr6inteoen g ed laeotupaxolrn stpn dcaicl-lieaoL osrifendnptoea eeer uid cdnrnls s taiiiaynatsxns t l to idcshsaf a eytwsH m shl2efotσo pdewi)wslgm eeoeinssr-;.
c shown in the upper right. The Hf evolution
ni diagram shows the Hf isotopic composi-
o
c tion at the time of zircon crystallization,
Ta Lower Permian Pennington-Lee clastic wedge in epsilon units, relative to the chondritic
7. WV-1-PR Proctor (n=234)
uniform reservoir (CHUR) (Bouvier et al.,
2008) and to the depleted mantle (DM)
Middle Pennsylvanian Pennington-Lee clastic wedge (Vervoort and Blichert-Toft, 1999). Shown
6. KY-19-PR7 Princess No. 7 coal (n=284) for reference is the evolution of typical
continental crust (black arrow), which
is based on a 176Lu/177Hf ratio of 0.0115
bility Lower Pennsylv a5n. iVaAn -P1-eGnNni nGgrtuonnd-Lye-Neo crltaosnt i c( nw=e2d7g4e) (eVt earlv.,o o19rt9 9a)n. dR ePfeartecnhceet t,fi e1l9d9s6, ;w Vheicrvho aorret
a shown by colored areas (explanation in
b lower right of upper panel), summarize
o
r Lower Pennsylvanian longitudinal system published Hf isotopic data for the Appa-
P
d 3. OH-4-SN Sharon (north) (n=319) ltaricthaila gnrsa i(nfrso; mM uAeplplearl aecth aial.n, -2d0e0r7iv, e2d0 0d8e)-,
e
z the Gander and Avalon accreted terranes
ali (Willner et al., 2013, 2014; Pollock et al.,
m 2015; Henderson et al., 2015), the Grenville
or orogen (Bickford et al., 2010; Gehrels and
N Lower Pennsylvanian longitudinal system Pecha, 2014), Meso protero zoic rocks of
4. OH-1-SS Sharon (south) (n=183) the Granite-Rhyolite province and Paleo-
proterozoic rocks of the Central Plains oro-
Lower Pennsylvanian longitudinal system gen (Goodge and Vervoort, 2006; Bickford
2. KY-18-CB Corbin (n=319) et al., 2008; Gehrels and P echa, 2014), and
the Penokean and Superior provinces of the
Canadian Shield (Gehrels and Pecha, 2014).
Upper Mississippian Mauch Chunk–Pottsville clastic wedge
1. KY-21-SG Stony Gap (n=310)
200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200
Detrital Zircon Age (Ma)
GEOSPHERE | Volume 13 | Number 6 Thomas et al. | Appalachian detrital zircons 2210
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Lower Permian Pennington-Lee clastic wedge
21. Greene (Becker et al., 2006; n=78)
20. Washington (Becker et al., 2006; n=83)
Upper Pennsylvanian Pennington-Lee clastic wedge
19. Upper Monongahela (Dodson, 2008; n=92)
18. Lower Monongahela (Dodson, 2008; n=172)
17. Conemaugh (Dodson, 2008; n=83)
Middle Pennsylvanian Mauch Chunk–Pottsville clastic wedge
16. Sharp Mountain (Gray and Zeitler, 1997; n=44)
Middle Pennsylvanian Pennington-Lee clastic wedge
15. Cross Mountain (Thomas et al., 2004a; n=37)
Lower Pennsylvanian Mauch Chunk–Pottsville clastic wedge
14. Pottsville (Becker et al., 2005; n=77)
ability AlleghanianAcadian Taconic Pan-African–Brasiliano & Iapetan synrift Grenville Granite-Rhyolite Central Plains Penokean &Trans-Hudson 1Eburnian &3Trans-Amazonian. Tumbling Run (BeSuperiorcker et al., 2005; n=26) FsfAcrahiopgtompiuowar nleUai, n c-4aPhg.nbi adRp na res nelftaavortlairyioetvsiluegaes nsraal dyopg feh(p a-isuncpa abrniolnldyibfstsoaithcrobmaenildl aeidt tsryai eo itnspna u,l otallhtorteess-
b available in the cited references). Vertical
d Pro Lower Pen1n2s.y Mlvaonnitaenv aPlleon (nBinegcktoenr -eLte ael .c, l2a0st0ic5 ;w ne=d3g9e) coof lpooretedn btiaanl dpsr orveepnreasnecnet p trhoev inagcees r ainn gthees
e Appalachians and North American craton.
maliz 11. Lower Raleigh (Eriksson et al., 2004; n=84) Tanhde 3p:l obtlus ea—reM caoulochr cCohduendk –aPso itnts Fviiglleu rcelsa s2-
Nor 10. Bottom Creek (Grimm et al., 2013; n=155) twice dwgeed; ggree;e rne—d—lonPgeintundiningatlo dni-sLpeeer scalla ssytsic-
tem. The plots omit a total of six analyzed
grains, which have ages younger than the
9. Pocahontas (Becker et al., 2005; n=61) stratigraphically documented depositional
Lower Pennsylvanian longitudinal system ages.
8. Sewanee (Thomas et al., 2004a; n=41)
7. Upper Raleigh (Eriksson et al., 2004; n=67)
6. Lee (Becker et al., 2005; n=58)
5. Raccoon Mountain (Becker et al., 2005; n=68)
Upper Mississippian Mauch Chunk–Pottsville clastic wedge
4. Bluestone (Park et al., 2010; n=91)
3. Princeton (Park et al., 2010; n=96)
2. Hinton (Park et al., 2010; n=93)
1. Mauch Chunk (Park et al., 2010; n=96)
200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200
Detrital Zircon Age (Ma)
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Our Hf isotope data are interpreted within the standard framework of juve- Sharon Conglomerate Member of the Pottsville Formation
nile (positive) values indicating magma consisting mainly of material extracted (Northern Sample OH-4-SN)
from the mantle during or immediately prior to magmatism, versus more
evolved (negative) values that record incorporation of significantly older crust. The Sharon Conglomerate Member of the Lower Pennsylvanian Pottsville
Vertical arrays on εHf diagrams are interpreted to represent magmas that Formation in northwestern Pennsylvania and northeastern Ohio laps onto an
t
contain both material derived from the mantle during (or immediately prior erosional unconformity that cuts down section northward to as low as U pper
to) magmatism and significantly older crustal materials. For comparison with Devonian strata (Fuller, 1955; Wanless, 1975). Paleocurrents in the Sharon Con-
our new data, color-shaded fields in Figure 3 encompass the main clusters of glomerate Member in northwestern Pennsylvania and northeastern Ohio in-
data points previously reported for potential provenance provinces (original dicate longitudinal (southwestward) drainage (Fig. 2) (Meckel, 1967) that was
data are in the cited references for Figure 3). separated from coeval transverse (northwestward) drainage during Pottsville
deposition in eastern Pennsylvania (Edmunds et al., 1999). A sample of the
Sharon Conglomerate from northeasternmost Ohio (Fig. 2) has a dominant
concentration between 1302 and 972 Ma with a strong peak at 1037 Ma and a
RESULTS OF DETRITAL-ZIRCON ANALYSES
weak peak at 1162 Ma (Fig. 3). Another prominent concentration at 491–361 Ma
has a peak at 443 Ma. Minor concentrations are between 1881 and 1302 Ma
New analyses include seven samples for U-Pb age data (Supplemental with peaks at 1648, 1458, and 1366 Ma; and between 682 and 538 Ma with a
Table S1 [see footnote 1], Fig. 3) and six samples for Hf isotopic ratios (Sup- peak at 618 Ma. A few grains are scattered between 2846 and 2675 Ma and
plemental Table S2 [see footnote 2], Fig. 3). The U-Pb age data are described between 972 and 777 Ma.
here in order of depositional age (oldest to youngest) and are placed in the
context of the two transverse dispersal systems in the clastic wedges and in
the longitudinal system in the distal part of the basin. The Hf isotopic ratios are Sharon Conglomerate Member of the Pottsville Formation
described separately. (Southern Sample OH-1-SS)
The sample location in southern Ohio is within the longitudinal dispersal
U-Pb Age Data system; however, paleocurrents and paleotopography indicate transverse
(northwestward) drainage locally during deposition of the Sharon Conglomer-
Stony Gap Sandstone Member (Sample KY-21-SG) ate Member (Fuller, 1955; Rice and Schwietering, 1988; Ketering, 1992). The
regional drainage and quartz-pebble distribution patterns suggest that the
Sandstone was collected from the Upper Mississippian Stony Gap Sand- local variations around the sample site reflect distributaries within the transi-
stone Member of the Pennington Formation at a site on the leading edge of tion from the Mauch Chunk–Pottsville transverse drainage into the longitudinal
the Appalachian thrust belt in eastern Kentucky in the distal part of the fore- drainage. The sandstone sample has one dominant mode at 1056–894 Ma with
land basin (Fig. 2). The sandstone has dominant concentrations of detrital- a peak at 1012 Ma and another at 501–380 Ma with a peak at 465 Ma (Fig. 3).
zircon ages in the ranges of 1238–936 Ma and 474–372 Ma with peaks at The sample includes a secondary mode at 1278–1070 Ma with peaks at 1232
1091 and 426 Ma, respectively (Fig. 3). Secondary concentrations are in the and 1182 Ma. The sample also has a minor concentration between 1791 and
ranges of 2966–2558 Ma with a peak at 2718 Ma and of 1815–1254 Ma with 1292 Ma with peaks at 1554 and 1332 Ma, and another between 711 and 554 Ma
peaks at 1660, 1508, and 1347 Ma. A few grains have ages of 2116–1876 Ma with a peak at 616 Ma. A few ages are scattered at 2695–2418, 2095–1883, and
and 637–532 Ma. The Stony Gap Sandstone Member, regionally, is the lower 336–330 Ma. The youngest grain is 330 Ma, which is the age of the earliest
member of the Hinton Formation within the Mauch Chunk–Pottsville clas- Alleghanian orogeny and also near the depositional age of the Sharon. Simi-
tic wedge northeast of this collecting site (Fig. 2) (e.g., Thomas, in Hatcher larities in the detrital-zircon populations indicate that the two Sharon samples
et al., 1989b); the sandstone unit has been correlated to this distal location are parts of the same longitudinal dispersal system.
as the Stony Gap Sandstone Member within the Pennington Formation
(Group) (e.g., Thomas, 1959; Wilpolt and Marden, 1959). This sample lo-
cation is within the area of overlap of the Mauch Chunk–Pottsville clastic Corbin Sandstone (Sample KY-18-CB)
wedge with the Pennington-Lee clastic wedge, leaving the provenance un-
certain; however, regional distribution and inferred continuity of the Stony A sample of the Corbin Sandstone represents the youngest part of the
Gap Sandstone Member are consistent with the distal part of the Mauch south west-directed longitudinal fluvial system along the distal part of
Chunk–Pottsville clastic wedge. the Appal achian foreland basin (Fig. 2) (Archer and Greb, 1995; Greb and
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Chesnut, 1996). The dominant concentration of detrital-zircon ages is in the weak secondary mode at 1524–1296 Ma has peaks at 1469 and 1339 Ma, and
range 1191–924 Ma with a prominent peak at 1076 Ma and a secondary peak another at 488–364 Ma has peaks at 487 and 432 Ma. Minor modes at 1692–
at 1176 Ma (Fig. 3). Another important concentration at 1843–1543 Ma has a 1624 and 628–585 Ma have peaks at 1653 and 625 Ma, respectively. A few
prominent peak at 1652 Ma and less pronounced peaks at 1808 and 1744 Ma. grains are scattered at 2810–2664, 1855, 1755–1754, 1565–1560, 757–718, and
The sample includes strong secondary concentrations at 2813–2531 and 533 Ma. The youngest detrital zircon in this stratigraphically highest sample is
499–406 Ma, with peaks at 2716 and 456 Ma, respectively. Another secondary 364 Ma, within the age range of the Acadian orogeny.
concentration at 1543–1211 Ma has peaks at 1502 and 1390 Ma. A few grains
are scattered at 3591–2986, 1987–1896, and 822–609 Ma. The concentration of
Hf Isotopic Data
grains with ages of 2813–2531 Ma, which corresponds to the Superior province
of the Canadian Shield, is distinctly greater than in any other samples, except
Hafnium isotopic analyses have been conducted on detrital-zircon grains
the Mississippian Stony Gap Sandstone Member (sample KY-21-SG) of the
from six samples that represent deposition in the two clastic wedges and
Pennington Formation, which is stratigraphically below the Corbin Sandstone
longit udinal system during Mississippian–Permian time (Fig. 3). For each
in the same general area. In contrast, other sandstones (samples OH-4-SN and
sample, zircon grains from each age group were analyzed with emphasis on
OH-1-SS) of the longitudinal dispersal system have only minor numbers of
younger (<800 Ma) grains and on avoiding grains with significant discordance
grains of Superior age.
or poor precision.
Precambrian grains from these samples yield juvenile to intermediate
εHf values, most of which overlap with values from Paleoproterozoic–Meso-
Grundy-Norton Stratigraphic Interval (Sample VA-1-GN) t
proteroz oic igneous rocks of the Grenville, Granite-Rhyolite, and Central Plains
provinces (Fig. 3). There is no discernible pattern in the εHf values with age or
A sample of a sandstone from the Lower Pennsylvanian Grundy-Norton t
basinal setting. Neoproterozoic grains in both clastic wedges yield εHf values
stratigraphic interval in the distal part of the transverse Pennington-Lee dis- t
that are quite variable, ranging from –13 to +7.
persal system (Fig. 2) has a strongly dominant mode of detrital-zircon ages
Zircon grains with early Paleozoic U-Pb ages yield interesting geographic
at 1252–934 Ma with peaks at 1175 and 1067 Ma (Fig. 3). A secondary mode
and temporal patterns (Fig. 3). Using the three phases of Appalachian magma-
at 1479–1252 Ma has a peak at 1454 Ma. Minor concentrations at 1770–1544,
tism (Taconic, Acadian, and Alleghanian) as a temporal guide, the two clastic
625–517, and 462–322 Ma have peaks at 1588, 619, and 370 Ma, respectively. A
wedges and longitudinal system contain abundant Taconic- and Acadian-age
few grains are scattered between 2720 and 2659, and at 1895 Ma. The young-
grains. Samples from the Pennington-Lee clastic wedge yield mainly interme-
est grain at 322 Ma is the only grain with an Alleghanian age; 322 Ma is near
diate (–5 to +5) εHf values, which are also present in samples from the Mauch
the depositional age of the interval. t
Chunk–Pottsville clastic wedge and the longitudinal system. Samples from the
latter two systems also contain grains with more negative and more positive
εHf values, which suggests that the sources contained more heterogeneous
Princess No. 7 Coal (Sample KY-19-PR7) t
crustal materials than those for the Pennington-Lee clastic wedge.
A sample of a sandstone above the Middle Pennsylvanian (Desmoine-
sian) Princess No. 7 coal (Fig. 2) has a dominant peak of detrital-zircon ages at APPALACHIAN POSSIBLE PROVENANCE COMPONENTS
1089 Ma, within a concentration in the range of 1254–901 Ma (Fig. 3). The sam-
ple includes a secondary concentration between 1550 and 1254 Ma with peaks Canadian Shield
at 1471 and 1318 Ma. Minor concentrations are in the ranges of 1733–1615,
661–551, and 470–373 Ma with peaks at 1656, 631, and 417 Ma, respectively. A The Canadian Shield of the eastern North American craton includes several
few grains are scattered at 2763–2668, 2153, and 1839 Ma. distinct age provinces: Superior, Penokean, Central Plains, and Grenville (Fig. 1).
These, as well as the Granite-Rhyolite province, are covered by Paleozoic sedi-
mentary rocks across the Midcontinent. Sedimentary thickness and facies dis-
Proctor Sandstone Member (Sample WV-1-PR) tributions along the present eroded limits of the Paleozoic cover strata, as well
as erosional remnants on the Shield and xenoliths in diatremes, indicate that
The Proctor Sandstone Member of the Greene Formation is the youngest much of the Shield was covered before Mississippian time and, therefore, not
exposed sandstone in the Dunkard Group in the Permian System in West Vir- available as a primary source of late Paleozoic sediment (Sloss, 1988; Cecile and
ginia (Fig. 2). A dominant mode of detrital-zircon ages of 1275–944 Ma has a Norford, 1993). Earlier, during Iapetan rifting of Laurentia and initial passive-
prominent peak at 1051 Ma and another peak at 1166 Ma (Fig. 3). A relatively margin transgression (e.g., Sloss, 1988), the exposed craton provided a primary
GEOSPHERE | Volume 13 | Number 6 Thomas et al. | Appalachian detrital zircons 2213
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source of zircons with ages from Superior to Grenville (Fig. 3), which were dis- Gondwanan Accreted Terranes
persed irregularly to parts (but not all) of the rifted margin (e.g., Cawood and
Nemchin, 2001; Eriksson et al., 2004; Thomas et al., 2004a, 2004b; Allen, 2009; Accreted terranes of Gondwanan affinity extend along the internal parts
Chakraborty et al., 2012) and were reworked by passive-margin transgression of the Appalachian orogen (Fig. 1) (e.g., Hatcher et al., 2007; Hibbard et al.,
(e.g., Konstantinou et al., 2014). The Shield has been interpreted to be a primary 2007; Hatcher, 2010). Three major composite terranes—Ganderia, Avalonia,
source of sediment supplied to the distal margins of Appalachian foreland ba- and Meguma—along the orogen from the New York promontory to the New-
sins, and these interpretations can be evaluated herein with detrital-zircon data. foundland embayment (Fig. 1) had been accreted by the late Paleozoic (e.g.,
Hibbard and Karabinos, 2013). From the Pennsylvania embayment southward
Grenville Province to the Alabama promontory, the Carolinia composite terrane comprises the
internal part of the Appalachian orogen (Fig. 1) (Hibbard, 2000; Hatcher, 2010).
The Grenville province encompasses the Elzevirian and Shawinigan orog- The Suwannee terrane (documented by drill data in the subsurface beneath
enies and the Ottawan and Rigolet phases of the Grenville orogeny, ranging the Gulf and Atlantic Coastal Plains) was accreted in the Pennsylvanian (Fig. 1)
through a time of approximately 1300 to 950 Ma (Fig. 5) (Bartholomew and (Thomas et al., 1989a; Thomas, 2010; Mueller et al., 2014).
Hatcher, 2010; Rivers et al., 2012). The Grenville province includes inliers of The Gondwanan terranes have Neoproterozoic metavolcanic, metasedi-
older, partially reworked crystalline rocks of various ages, including compo- mentary, and plutonic basement rocks with ages of 800–520 Ma, correspond-
nents of the Granite-Rhyolite province (1500–1320 Ma, reworked in the Gren- ing to Pan-African–Brasiliano events in Gondwana (Fig. 5) (e.g., Pollock et al.,
ville province of southern Canada), the Labrador province (1700–1600 Ma, re- 2010; Willner et al., 2013; Mueller et al., 2014; Henderson et al., 2015); Sm-Nd
worked in the Grenville province of eastern Canada) (Rivers et al., 2012), and systematics from the Suwannee terrane indicate interaction with Mesop rotero-
the Mars Hill terrane (1800 Ma, reworked in the southern part of the Grenvillian zoic (1330–1040 Ma) lithosphere (Fig. 5) (Heatherington et al., 1996; Mueller
Blue Ridge external basement massif) (Fig. 1) (Ownby et al., 2004). As shown et al., 2014). Detrital zircons from late Neoproterozoic to Cambrian sedimentary
on Figure 3, igneous rocks of the Grenville orogen and sediments derived cover strata generally are dominated by Pan-African–Brasiliano ages of 760–
from these rocks yield εHf values that range from –5 to +10 (Mueller et al., 530 Ma; older components of Gondwana, including ages of 2730–2550 and
t
2008; Bickford et al., 2010). Relative enrichment in zirconium during the Gren- 2160–1140 Ma, especially Eburnian–Trans-Amazonian ages of 2160–1950 Ma,
ville orogeny generated extraordinarily abundant zircons of that age (Moecher are variably represented in the sedimentary detritus (Fig. 6) (Pollock et al.,
and Samson, 2006), at least partially accounting for the dominant numbers of 2010; Willner et al., 2013; Henderson et al., 2015). Detrital zircons from the
Grenville-age zircons in many Paleozoic sandstones. Cambrian to Devonian cover succession of the Suwannee terrane have age
Grenville-age rocks exposed in Appalachian external and internal base- concentrations at 650–510 Ma and 2250–2000 Ma (Fig. 6), corresponding to
ment massifs (Fig. 1) provide a primary source of detrital zircons with ages Pan-African–Brasiliano and Eburnian–Trans-Amazonian, respectively (M ueller
of 1300–950 Ma, as well as some older ages from inliers within the Grenville et al., 1994, 2014). Within the Devonian–Permian fill of the fault-bounded
province. Abundant Grenville detrital zircons are available for recycling from composite Maritimes basin (Fig. 1) (e.g., van de Poll et al., 1995), Devonian–
post-Grenville Appalachian sandstones. Mississippian sandstones in the St. Marys sub-basin have detrital-zircon age
Alleghanian plutons
A
Acadian plutons
Figure 5. Diagram of ages of potential n=54
primary sources of detrital zircons for the Taconic plutons 350 400 450 500 Ma
Appalachian foreland. Black bars indicate
crystallization ages of zircons; gray bars
Iapetan synrift plutonic and volcanic rocks
indicate ages of xenocrysts, inclusions,
and protoliths within the primary igneous
rocks. Data are from references cited in the Gondwanan terranes
text. Inset A: Relative age-probability plot
of data from Taconic and Acadian igneous Grenville province
rocks (from Sinha et al., 2012).
2 3 4 5 67 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Age (×100 Ma)
GEOSPHERE | Volume 13 | Number 6 Thomas et al. | Appalachian detrital zircons 2214
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Research Paper
AlleghanianAcadianTaconic Pan-African–Brasiliano Eburnian &ns-Amazonian
a
Tr
GANDERIA, AVALONIA, MEGUMA
Devonian–Mississippian basin fill (St. Marys sub-basin), Avalonia, Meguma
(Murphy and Hamilton, 2000; n=95)
Cambrian sedimentary cover, Ganderia (Willner et al., 2014; n=302)
y Cambrian sedimentary cover, Ganderia (Fyffe et al., 2009; n=277)
bilit
a
b Figure 6. Relative age-probability plots of
o previously published results from U-Pb
r
P analyses of zircons from sedimentary
d cover rocks in accreted Gondwanan ter-
ze ranes (analytical data, location, and strati-
ali graphic information are available in the
m Neoproterozoic–Cambrian sedimentary cover, Avalonia (Henderson et al., 2015; n=570) cited references). Vertical colored bands
r represent the age ranges of potential prov-
o
N enance provinces for sedimentary rocks in
Gondwanan accreted terranes. The plots
are color coded to distinguish between
Neoproterozoic–Cambrian sedimentary cover, Avalonia (Willner et al., 2013; n=432) different Gondwanan terranes.
Early Neoproterozoic, Avalonia (Henderson et al., 2015; n=160)
CAROLINIA
Neoproterozoic–earliest Cambrian sedimentary cover, Carolinia (Pollock et al., 2010 n=410)
SUWANNEE
Cambrian–Devonian sedimentary cover, Suwannee (Mueller et al., 1994, 2014; n=75 )
ALL (n=2321)
200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200
Detrital Zircon Age (Ma)
GEOSPHERE | Volume 13 | Number 6 Thomas et al. | Appalachian detrital zircons 2215
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