Provenance and Paleodrainage of Late Jurassic andEa r ly CretaceousReservoir Sandstones in the Flemish Passand
Orphan Basins By
©David GeorgeLowe
inpanialfulfillmcnt of thc requirementsfor thedegree of
Departm ent ofEarth Scien ces MemorialUniversityof Newfoundland
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Figurel.R:Geologiccross-scctionof thcOrph anB asin.Th e Whilc Sail faultscparalcslhe older East Orphanand younger west Orphan Basins.TheBonavista Faultisthemajcr basinboundingfauh.und
Figurc2.13:Corelogforcorc 2inBaccalieu 1-78.Corc2isfromthe Avalon Forrna Ovcrall.ilisahca\'il yhioturbalcd.finc graincd argillaccous androorly ccmcntcd s:l
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Figurc4.3:I)ic chartgi vingproportiollsofdctritalhcavym incra]sofinlcrcslrromlhrcc 5-msamplc intervals (3(1I51ll-3630rn)intheJurassic Sandstone#1inMizzenL-il
Figurc-t.e :Pic chartgivingproportions of delritaI heavyminerals ofinterestfromthree5-msample intervals(3255m· 3270m)from the HiberniaFonn ationequiv alentin Baccalieul-78 Figurca.j:Picchartgivingproportions of detritalheavyminerals ofintcres I from four 5-msample intervals(2160m-2185m)from theAvalonFormationequivale ntin Baccalicul-Zx Figure4.9:Cross-plotsofheavymineralindexvaluesfrom allsamplcs.Seescctiona.Zfor explanation of mineral indexes,andSection 4.3and-l.afor descriptionsand interpretations 1~6
Figure 6.8:Cross plOISofgrainzoningtypes versesConcordia agesofdatc dzirconsfromeachinterval Onlyconeordant U·Pbagcsarcincludcd.Error h'lrsarc2u.oc.ct.en=oscillatoryconcentric centered;
Figurc6.14 :BS Eima gcs ofdcl rital l irconswith localions of40·40prn iascr rastcrp itsf romJli hcmia SandsloncinBaccalicul-78.(A) Rclati\'c1yc1ongatc.cuhcdralosc illaloryzo ncdLateDevonian detrital
Figur e 7.6: Regionalprovenanceinterp retationfor thcAlbian sandslonc inBlu cH -28.Ap romincnt agc peakcomprising first-cycleSilurian aged detrital zirconsindicates proximal sourcestothe west and
~~~~'~~::~:~lludingSilurianorogenicgranitoids intheGanderZone.and minor sourcingfrom Avalon
Cha pte r 1: Introdu ct ion an dGeolo gicalSetti n g
I.lln'rodu cti on andPu rpose
Thisthesis co ntainsan in-depthstudyof EastCoastCanada Mesozoicsands to ne provenanceusingdetritalheavyminerals.Thesandstones were interccptedbyindustrial oilandgas exploration wellsin the FlemishPass and Orphanbasins.wh ichnrc located approx ima tcly 400 kmnorthea st ofSt. John ' s,ewfound land (Figure l.l).Thesebasins arc fault-boundedMesozoicagedbasinsthat fonncdbyattenuationofthc contincntal crustduringrepeated Mesozo icritt periodsthatpreced edthebrcakupand seafloor spreadingbetween North America and itsconjugatemarginsIberia andN\VEurope.
Coveredbyrelativelythick passive marginsedimentaryscquences,thcba sinsarc currentlytargetsof oilandgasexplorat ionbecausetheyarcstratigraphically similarto theadjace nt Jeanne d'Arc Basin,aprolificoilandgasprovince.Thcstratigraphic similaritiesinclude thepresen ce o f a matureKirnmerigianaged sourccrockaswellas LateJurassicto EarlyCretaceou spotentialreserv oirsands toneformationsin the Flemish PassBasin,cons idered analogou stothe primaryrcscrvoirsand stone fonnationsin the Jeann ed'ArcBasin(theJeanned'Arc,Hibernia,Avalonand Ben NevisForm ation s) (Cre ane yandAllison,19 87;foster and Robinson,1993;Desilva,2000).Thedistribution andgeologyof reservoirsands tonesinthe Jeann e d'Arc Hasin arcwellconstrain ed.based on theusc of coreanalysis.well corre iatio nsandcorrobora ting2 D JDseismic interpr etati on s(Tankard andWelsink,1987;Enaehescu,1 988; Sin elair,1 993;Enachcscu
ctaI., 19941. However,unlikethesha llow waterJeanned'Arc!Jasin,the deepwater FlemishPass and Orphanbasins havePOOfwellcontrol.duetothe greatcrcxpcnscof drillingthese areas;and thus.provenance.orientations.correiations.Iatera lrcscrvoir qualityvariationsandother depositional constraintsofsandstonesin these basinsduring this time arcverypoorly constrained.Also,our understandingofrcgionalrifting.
drainage and tectonics islimited.give» onlyknowledgeof proven aoee,paleodrainage orientations and uplift histories fromstudies into theJeanne d'ArcBasin .
Thegoalsofthisstudy arcasfollows:
I.To furtherconstrain regionalpaleo-drainage,paleo-geography, upliti and basin confi gu rationsduringrifting.
2.Todctennineconstraint s ontheorien tation,extentand quali typredictions ofLatcJura ssicand Early CrctaccOllsr c scrvoir facicsinthci-=lcmi sh Pass and OrphanBasins.based onregionalpaleod rainagemodels.
3.Tomake regionalcorrelations betweenpotentia lrcscrvoirsandstones,and 4.To testtheapplicationofheavymineralanalysisandthe analytical
methodsused(MLAand ICP -MS1t oindustry-relatedfronticr cxploration
Severalsyn-riftsandstones from theFlem ishPassBasin ,ranging inagefrom TithoniantoBerri asian.andoneAlbianagedsyn-riftsandstone from the\Vest Orphan Basinwere usedin thisstudy. This study utilizes severalcomplirnentary methods to interpret provenance. includingthinsectionpetrography (Chapter3).provcnance - sensitiveheavymineral ratios(Chapter 4). detritaltourmalinechemicaldiscriminations (Chapter5) anddetritalzireonpelrog raphy and U-Pbgeoehronology(Chaptero).
_ _I
This chapter focu ses onthe regionalgeologica lsetting ofthesesyn-rift sands toncs,with emphasi s on basinandbasement platform configurations and sedime ntation duringtheTith onian -Albian,aswellasthegeol ogyandagesofvarious surro unding potcntialsourceareas.Alsoincludedaremoredetailedoverv iewsof thc geology andgeologicevolutionof theFlemishPassand Orphanbasins.
1.2 i\les olo ic O ffshoreNewfon nd landgeolovicala ndtec'onicsettinV
Asshown in Figur e1.1,curre nt daysyn-riftMesozoi crocksotTshore Newfoundlandareconfi ned to aseries of varia blyintercon nectedhalf-graben riftbasins sepa ra tedand bounded bypre-Mesozoic ba seme nthighs.andincl udetheJea nn ed'A rc, WestOrphan.EastOrphanand FlemishPassbasin s.These basinsformedduringthe Mesozo icintra-contin entalrifting, spanningfromthePermo-Triassic untilthe Mid Cretaceo us,whichwasfollowe dby NorthAtlantic seafloorspreadingand passivemargin sed imenta tio n untilrec enttimes(Enachcscu,1987 and19 88;Tanka rd andWclsink.1989;
McAlpinc.1990;Enachcscuctal..200 5).
Theriflsystemandopen ingofthe Atlanticwas seq uentialandgraduallymo ved fromsouthtonorthduringtheLate TriassictoearlyLateCretaceous•resultingin prolonged extensionand basinfon nat ionon the Newfoundlandcontinentalshelf {Figurc 1.2).TheJeanned'ArcBasinpresc rvcsthcdecp est(-22km)andmostcompl c tcsyn-ri ll successionoutoftheMesozo icbasins ofTshoreNewfoundland ,dueto itsproximitytothc ma inlistr icde tac hme nt,orbasin boundi ngfault.and rclati vcl
YcontinU:(U~SS UbSidcncc
throughthecontinentalnil phases(Figure1.3) (Keenctal.,1987;Enachescu.1987;
4
TankardandWclsink,1987).ltalsohostsscvcraloff shorc oilficlds,h ascxtcn sivcwcll co ntrol,andhasbeenstudicd cxtcns ivcJy.Thus,thcstra tigra phy0fthc Jeanne d'Arc Basinis conside reda goodanalogue for regionalexplorationandstudiesofsyn-riftbasin sedimentation c1scwhereoffsho reNewfoundland(Figure IA).Thrcestagcso f rifting
sho wn to have affec ted many ofthc NorthAtlantic Basin srcgionall y(Enachcscu,1 9 87;
Tank ardandWcl sink,19 87;Sinclair,199 5).ThcThrccriftstages,acc ordin gto Enac hcscu( 1987),arc;[ll thcTcth ysrifting stngc, fromLateTriassic to EarlyJurassic, whichresultedin themid-Jurassic breakupbetweenNorthAmericaandAfrica and
subscqucnts calloorsprcad ingsoulh o f thcNcw found land Frac turcZo nc;(2 )thc North Atlanticrifting stage. fromLateJurassicto EarlyCretaceous,whichendedin incipien t scatloors prcadinga ndb rcak· up bcl\vcen thcso uthcmG rand 13anksand Iberia: and (3 ) the LabradorSea rifting stage. occurrin ginthclate EarlyCretaceous (from the Barremian to Alb ian),thalresulted in thefinalbreak- upbetwee n Iberia an dtheG ran d lJanks, propagation ofincipientscatloo r and cvcntualbreak-upbetweentheNortheas t Newfo undlandshelf andNorthernEuro pe,and riftin gbetw eenLab radorandGreenland (Enach cscu,1987;Tankard an dW elsin k,1 9 89;M cAlpine,1990 ;SinJc air,1993 ).A fourthrifting stag e thatintluencedthe Orphan and Lab rador area isrelatedtoLate Cretaccousto T crtiaryriftingbetweenLabrador and Greenland( Enachesc ue l aL,2005) Follow ingthesucceeding intra-continentalriftingstages wasthc final post-riftstag e.
wherethennalsubsidcnceofthcncwlycrcatcd contincntalm arginsdomin atedfrom Late Cretac eous (Earl y Tertiary in thenorth ) onwa rdsand pass ivemarginscd imcnts wcrc depo sitedalongtheAtlanti cshclf,slopcandin deep water.
Syn-riftlili fromtheTethysriftovcrlicsprc-riftbasem entandiscomposedof Triassiccarly syn-riftcontinentalredbedsandevapora tes.Mid-to LateJurassic post- Tethysrifting strata aredominatcdbycarbon ate s,butineludeth cKimmeridgian aged organic-richcarbonaceou s shalesof the EgretMemb er.whichrcpresentstheprovcn regional oilandgas source rock.TheLateJurassictoEarly Cretaceoussequenccs ofth c North Atlant icand Labrad orSearift phases genera llycomprisesa suecession of terrestrialto marginalmarin esiliciclastics.whichincludethetluvial-deltaic and shorefacc sandstones that make up the mainoilandgasreservoirs(Jeanned'Arc ,Hibernia,Avalon andBenNevis Formations).Thepost-rift success ion comprises stratafromLatc Crctaccousonwards.and is dominatcd by contincntal marginsiliciclastics(Tankardand Welsink,1989;McAlpine,1990;Sinlcair,1993).Thesame orsimilarpackage of Late TriassictoMid-Late Cretaceou sagedsequences arc consideredto existin the Flemish I'ass and EastOrphan basins(FosterandRobinson ,1993;Enachescuet al.,2005).Wells intheFlemish PassBasinhaveintercept ed similarLate Jurassic toEarly Cretaceous packages, and thesepackageshave been tracedfro mthe FlemishPassBasin intothe East Orphan llasin(F igure 1.5) (FosterandRobinson,1993;Enaeheseuetal.,2005).
Additiona lly,theGreat Barasway F-66 well,drilledin theEast OrphanBasin in 2007, intcrceptcdJ urassicandCretaeeou s strata( C-NLOPIl,2009 ).lnthcWcstOrphanllasin , riftingbeganinthe Albian,muchlater than in the East Orphanor FlcrnishPassbasins.so thc ageofsyn-rifl sedimentary infillonlyranges fromEar lyCre taccous(Albian)to Palcoccnc ( Enacheseu etal.,2004;Enaeheseue ta l.,2005;Hardy,2008).
Out ofthcbasinshighli ghtedin Figure1.1.the Flemi shPass,Jeann ed'Arcand East OrphanBasinswere acti ved cpoccntrcs ofclastic materialduri ngtheTithonian to
Valanginian.duringwhichtimereservoir sandstoneswercdcpositedlocally,at leastin theJcanne d'Arca ndFl emishPassbasins,butpresumably alsointhe EastOrphanBasin (TankardandWelsink,1989;M cAlpine,1990;Sinlcair ,1993;Enachescu etal.,200 5;
lIardy,2008).Syn-depositional comm unicationbctwccn thcsc basinsisthoughttohave bcenlikcly( Enachcscuctal.,2005)(Figurcl.6).Thcdcpositional constraintsand insightsintotheprovcn ancc of such sandstonesin thcJeanned 'Ar cBasin havcbcen described in detail,andarcreviewedbrieflyinthe nextsection, alongwithconstraintson syn-riftsandstoncdcposition fromo therNorth Atlantic rift basins.Theprovenanceand orientationsof reservoir sandstonesofthe sameageare notknownin theFlemish Pass Basin,and thisprojectaddresses thislackinginform ation,Theprovcnanccand implicationsfor sand body orientationsofAlbiansyn-riftsandstonesin the\Vcst Orphan basinarcalso addr essed, and similarly,contempora neousregional riftevolution and
1.3 Latl' ,Jurassirto[arh·C ntacl'ousRl'gion al sl'ttin g
DuringMesozoictime,mainlyfrom thePermo-Triassic untiltheLate Cretaceo us.
intra-cont inentalrifting that precededthebreakupofPangaea and openingofthe Atlantic Ocean wasextensive.TheopeningoftheAtlanticwas sequentialand graduallymoved fromsouthto north duringtheLateTriassictoearly LateCretaceous,resultingin prolonged riftinginsomeareas(Figure1.2).Thisprolonged riftingresultedin thc formationof riftbasins along theNorth Atlanticmargins.includinglbe rian andlrish continentalshclvcs (Figurc1.7).Figur e1.7 showsanapproximate rcconstructionof Late
Jurassicto EarlyCretaceo us(Tithonian-Albian) paleogeography•includingintra- continentalrift basins.variousplatform areas.andoceanspreadingridgesat that time (see captionof Figure1.6 forrefe renc esl.Basin conne ctivity waslargelycontrolled by the orientationsof basementplatforms, whic hwereexposedduringmuchofthis time .Thus, the orienta tionsof theseplatformspresumablyhad importantcontroIs onpaleodrainage andsyn-depos itiona lcommun icationbetweenbasins,andadditionallymay have actedas thoroug hfaresfor regionaldrainage systemsintobasins,orwerc upliftedperiodically, providing detritus to basins.Figure t.7alsoincludes potential basin andplat form conju gatepairs.Thepairin g ofconjuga te platformsis important forreconstruct ing paleogeography.aswell asfordeterminingphysicalbarrierstoregionalpaleodrainage systems.Someof theseconju gatepairingsinclude the PorcupineBasin-Orph anBasin.
LusitanianBasin-CarsonBasin.theGalici aBank -Flemi sh Cap-Go ban Spur,and PorcupineBank-OrphanKnoll(Masson and Miles,1984.1986;Verho cfand Srivastava, 1989; Enachescu,1992;Srivastavaet al.,2000;Sibuetct al., 2007)
Similarlytimedrifting events, occurrin gfromthePcrmo-Triassictoth e Paleocene, occurredin conjugatemarginbasinsincludin gthePorcupinc.Lusitani an.und Ce lticSeabasins,resultingina broadlysimilarsyn-riftstratigraphyin these basinsasis presentin theJeanned'Are ,Flemi shPass and Orphanbasinson the NorthAmerican margin(Masson and Miles,1984,1986; Sinclair,1995;Hiscott,I990;Johnston ct al, 200 1).In parti cular,thesebasinsexperienced markcdlysimilar tectonichistorie sand conte mporaneo ussourceand reservoir rockdeposition duringtheLateJurassicto Early Cretaceou s(Kimmeri dgian10Aptian)(Sinclair,1995)
This section briellydescribesthe genera larchitectures andorientations ofba sins and platformsanddepositionofreservoirfaciesinto basinsduring the late Jurassic to Early Cretaceous.Theb eststudicdb asinsin ciud e the ScotianBasin.OrpheusGraben.
WhaleBasin.J eanned'ArcBasin,Flem ishPassBasin.OrphanBasin,LusitanianBasin, Porcupin eBasin.andCeltic SeaBasins;basemen t platformsinclud etheLahavePl atfonn, Ava lonUplift/so uthern GrandBanks.HonavistaPlatform .FlemishCap.Galicia Bank.
GobanSpur,Com ubian Platform,PorcupineBank.aswell thelargerupliftedareas inciudingthe Newfoundland.lberian. andlrishPlatfornls.andt heR oc kallPlatfornl (Figurc I.7 ).The pre- Mesozoicg eologyof theseareas isdescribedinalatersectiono f this chapter.
TheScotian Basinis atruerift basin that iscomprisedof aseriesof Triassic sub- basinsdissected byshallowbasementhorsts andsaltstructures.Its western marginisa composite deep listricbasinboundingfaultand theLal lavcPlatfonn ,andits eastern marginistheAtlanticOcean and thecontinent-ocean bound ary(Figure1.7).Itcontains similarTethysstagcs yn-rift depositsasarepresent inother basins(incl udingredbeds andevaporates).butstratayoungcrt han13ajocian(mid-Jurassic)aremostlyplatfo rm carbonatesand progradationalpost-riftclas tics.depositedafter thebreak-upbetween NorthAmerica and Africa.Thusunlike manyoft heother north Atlantic rift basins,the Scot ianUasin experiencedonly one rillingp hase.followed by earlyand prolongedsyn- rillsedimenlalion in anopenshelfe nvironment (Ja nsaa nd Wade, 1975; We lsinket.al.
1989;Wadeand Mcl.ean,1990).TheOrpheusGrabenhad a similardepositionalhistory andsyn-andpost-riftsedimentaryfillasthe Scotian Basin intheMesozoic.However.jt remainsconfined betweenbasem entplatforms (theScatarieRidgc and the CansoRidge )
andis boundc d bc rcactiva tcd tra ns fcrfa ults(Jansa andWadc,1975;Wclsink ct.al, 19 89 ) (Fig ure 1.7).These ofTshorc Nova Scotiaplatforms andbasinsarcnot cons idere d tohave beenregionalsediment source areasto the Grand Banksbasinsor connectedbyreg ional drainage duringtheLateJurassicto Early Cretaceous. becau sethey\v'ere atthetim e located in apassivesubsiding marginsetting alongthe proto-AtIantic.and thuswould have beenan area oflowand negati vereliefrelativeto the Grand Banks.Addition ally.
thcsc basinsarcIikcly to have beenseparated fromthc Grand banksbasinsbythe Avalon Uplift,an extensiveupliftedareasouthofthc Jeanne d'Arcand FlcrnishPassbasin s where extensiveup liftoccurredfrom the Tithonianto the Aptian (Keenct.al ,1987;
Tankar dand Wclsink,1987;Enachescu, 19 88; Sinclair,1993).Pc-Pipcr and McKay (2006)showthat duringth c EarlyCrctaccous,dctrituscntcrcdthe ScotianandOrpheus basinsviaa seriesof regional drainage systemsextendingto variouspartsoftheAtlantic Canadianmargin,including New Brunswick, Gaspe, Labrador-Quebec andwesternand
Basin sonthesouthernGra ndBanks,incl udin gtheWhale,lIorseshoeandSouth Whalcbasins,arc all halfgrabcnsboundcdtothc wcst bylistricdctachmcnts alongthc BonavistaPlatform . similarinovcrnllstruc tureto theJeanned'ArcandFlemish Pass basins( Enach cscu,1987;Kccn ct. al,1 9 87;Enachcscu,1988) (Figurcsl.land I.7).
These basinsexper ienced rift tecton ism andsyn-ri ft depositionduringthe Triassicto mid- Jurassic,andhave earlysy n-rift deposits similar to theJeanned' ArcBasin,includingred beds,evaporntes,limeston esandshales.However, ahiatusindcposition,coevalwith upli ftalongwithlargcpartso f thcsouthcrn Grand Banks,tcnncdthc AvalonUpli ft, occurred between the TithoniantoAptian,atatime when syn-riftdepositionwas
prevalentinmost otherNorthAtlantie basins(llubbard,1988;Tankard andWcl sink.
1987;Enachescu,1988;l3alkwillandLegall.1989;Sinclair.1993).Mucbofthematerial erodedfrorn thisareaduringtheTithonian-Aptian wasdepositedtothesouth.intothe seawardedgeof theSouth WhaleBasin, whichat thistime wasc xperiencingapost-rift stage, akinto thatoftheScotianBasin.whileothermaterialwastransported north.into theJ eann ed'Arcbasin (Tankard andWelsink,1987;llubbard,1988;Enachcscu. 1988).
TheJeanned'Arcbasinis adeephalf-graben failedrittbasin,with22km topre- ritlbasem ent.ltisboundedt oth e westb ya deepcrustaleast-dippinglistricfault (the Murre-Mercury fault)against theBonavistaPlatformtothewest,tothe eastbythe Central Ridgehi gh,toth esouthbytheEgretfaultand AvalonUplift and10thenorth by the Cumber landRidge (Tan kardandWelsink,1987;Enachescu.1987;Keene t.a l,1987;
Enachescu1988)(Figures1.1.1.3 and 1.7).The Honavi staPlatforrn isa peneplained basement upliftoverlainwithepeiric Mesozoicand thinTertiarypost-riftdeposits,and formsthewesternshoulderofallof the rift basinsOffshoreNcwfoundland(Enachcscu, 1987;Tankard and Wclsink,1987;Grantand McAlp ine1990)(Figure sl.land 1.7).The CentralRidgc comprises a groupofn ort heast-sou thwcsttrcndingb asement ridgcs ovcrlain byaLatcT riassicand Jurassicscqucnccwith minorCrc tacco us sedimc nts filling inlocal grabens. Mostoftheupliftofthe Central Ridge occurred fromthe Tithonian10 thcl:3erriasiandu ctoa ctivation ofthc supracrustalEgrctandVoyagcr faultsystems, at whichtimeitwouldhave fonn cdaph ysiographicbarricr bctwccnthcJeanned'ArcBasin
and Flemi sh PassBasin Ifinachescu,1987.1988; TankardandWelsink.1987;Foster and Robinson.1993;DeSilva, 2000)(Figures1.1and1.3).The Cumberl and Ridgeis a prominentcast-west trendingbasementhigh and forms aphysiographicba rricrb etwccn
lhc Orph anll asin andlh eFl emishPassand Jcannc d'Arcbasinsandi s covcrcd by rclativcly thinCretaceo usandTertiarysediments:althoughitsrolein LateJurassicand EarlyCrclaceo usdrainagcanddepositionisunknown (Figure s1.Iand1.5).Thc Avalon Upli ft.usmentionedpreviously,W3Sanarea ofrillingandsubsidcnce until thcTithonian.
at which timeit wasuplifted untilthe Berriasian.and againfromthe Valanginianuntil the Aptian.Upliftofthis area isthoughttohave occurred duetotransfonnmovcmc nts alon g thcNcwfoundland transfer zoncto thcsouth and incipicntbreak up betwccn thc southcm Grandlla nksandlberia(E nachescu, 1987;T an kardandWelsink,1987;Sinc1air, 1993).
Dcpositionof course c)astics (rcscrvoirsandstoncs)intotheJeanned'A rcbasins peakedbetw eentheTithonianto theAptian:andcoincideswiththe tim ing of rifting between theGrand Banksand Iberiauntilthebreak-upand seatloorspreadingbctwecn thcsetwo continent alfragm ents.Thcd cposition ofre servoirsand stonesduringthis time waslargelyinfluenced byfaultin g and tectonicupliftandsubsidence(Massona nd Miles 1986;TankardandWclsink,1987;Sinclair,1993).Syn-rillsandstone depositionbeganin theTithonian.withthedeposition of thefluvial-deltaicJeann ed'ArcFormation.These sands enteredthebasinfrorn thesouthandsoutheastmainly. andevidencedbthe presence ofchannel-like incisionson thesouthem marginorthebasin,anda concentra tionofthethickest and most aeriallyextensivefan delta sands in the southwest margin or thebasin.Depositionwascoevalwithupliftof the AvalonUplifttotheso uth (Tankardand Welsink,1987;McAlpine,1990;Enachcscu,1994).lnolhcr partsof lhc basin.small marginal alluvia land marginal marinefanswere depositedintothe basin frorn local pointsource s,suchasthemarginofthc13onavistaPlatform(Tank ardand Wclsink,1987).T he second pulscof coarscclaslicinpul is characlcrized bythc
depositionof thelargesandy fandeltasof theHibernia Formation,duringthe Berriasian.
Uplillofanddrainageoffofareastothewest and south,includingth eBon avistal'latfoml and the AvalonUplift.occurr edduringthistime. resulting inarelativelyrestricted distributionof theHibernia Formati oninto the southernand westernmarginsof thebasin
(Tan kardandWelsink,1987;MeAlpine,1990),Duringth el atellaITemian,another pulse ofcoarsesedimentationoccurred,resultin gin thedeposition oft hestacked prograding shore face. estuarine and coastalplainsand and mud packages of the Avalon Format ion.
Thisfonnationthickensintothe southw estemmargin of thebasin.and presumably episodicmarginuplift led to progradati on of thesesands from theAvalon Uplifttothe so uthwest(Tankardand Wclsink,1987;McAlpine,1990; Sinclair,1993;Ainsworthet. al, 2005).Thcfinal maj or pulseof coarsec1asticscdimcntationoccurred intheAptian- Albian.withthetransgressive shoreface and estuarine sands of theBcn NevisFonn ation.
Transportofclastic materialintolarge estuariesduring thistime wasthough lowgradicnt riversdraining ofTofareas tothesouthwest (AvalonUpliftandBonavista Platform) (Tankardan d Welsink,1987; MeA lpine,1990;Sine lair,1993).
The Flem ishPassbasinis alsoahalfgrabenbasinbounded tothecastbya decp listric fault. antithetic to the Murre-Mercuryfaultand infonnallyknownasthe Voyager Fault(FosterandRobinson,1993) (Figure sL1,L3and1.7).It form stheouter part of a double-failedriti asdescribedby Enaeheseu ( 1988).Tothe west,theFlemishI'assllasin isboundedbytheCentralRidgehigh,to the East andsouth bytheFIemishCa p-Beothuk Knolland tothe north by theCumberland Ridge andEast Orphan llasin( Enachescu . 1987;Keenet. al,1987; Enaeheseu 1988;Enaeheseue t.a l,20 05)( FiguresLl,L3 and 1.7).It mayhave beenincommunication with the East OrphanBasinduringperiodsof
riftingandsedimentation (Enach escu atal.,2005) (Figu res1.5and 1.6). Essentiallyt he FlemishPassBasin conta inssyn-a nd post -ri ftdeposit swithagcnerall ysim ilar to thatof theJeanned'ArcBasin,butwithabout halfth edepthto basement(Enachescu ,1988;
Fosterand Robin son.1993).Dcposition of courseclasticsinto occurred atsimilarperiods between the Tithonia nand Aptianasthey weredeposited intot helean ne d'Arc Basin:
however. jheexten t,orientation and provenance ofthese sandstones are not known or poorlyconstraine d (Foster andRobinson,1993).Thegeology andgeologicalevolution of theFlemish PassBasin is describedindetail latcr inth ischapter.
TheFlemi sh Cap is aphysiographicallyisolated pre-riftbasementfragment, fonnin gth e eastcmmar gin ofth eFl cmishPassB asin (Figurcsl.l aod1.7 }.ltconsistso f
acentralareaofexpose d basem ent,surro undedbyon-lappingTertiaryand minor Cretaceoussedimentary rocks . Seismic interpretations acrosstheFlemish Capshow no
evideneeforcxtcnsionalbasins or syn-rift strata.andforthem ost part theFlemish Cap is a cohere ntcontinentalblockcovcredb y aveneer of postriftsediments(G rant.1973:
Enachescu,1987,1988;Grant&McAlpine1990 ;Foster and Robin son,1993;Hopperet al..2 006).Rece nt magnetica ndg ravityg eo physicalstudicsof incipicntseafloo rat the marginbetw eentheNewfoundlandand IberiashowthattheFlemishCapandGalicia
(Srivastavaela l.,2000; Sibueteta l.,200 7).ltsroleasabaseme nt platforminLate Jurassic to EarlyC rctaceo us palcodrainagcanddcpositionofclas tics is not known.
dissectedby N-SandNW-SEnorma lfaultsand various salt diapirs,andhas complicatcd structure andsyn-riftsediments confined to multipledepocentres(\Vilson et al..1 989;
Alvcsct al..200Ja,200Jb).ltconlainsabroadly simil arM csozoicriftand post-rill stratigraphy asthe leanne d'ArcBasin.undit isthoughtto havebeen connectedtothe Carson l3as in bcfore break up(Hiscottc t al., 1990;E nachcsc u. 1992;Sinclair, 1995;
JohnSlun clal.,2001)(Fi gurc l.7 ).FromlhcTithoniantoth el3erriasian,depositionof tluvial-dcltaic sandsintothe Lusitani anBasinfromhinterlandsinthe northeast (Iberian Massif) ,northwe st and north (Galicia l3ank?) wasrelati vclyconstant.After a bricf Berriasianhiatus.coin cidingwithaperiod of uplift and non-deposition,thesamc deposition oftluvial-deltaicsands from thenorth-northw cst occurred from the ValanginianuntiltheAplian(Rcy,1972;\Vil son et al..1989;Alvcset al.,200Ja. 200Jb ).
TheGaliciaBank isastructural basemen thighlocatedeastof mainlandn orthcm Spain(Figure1.7).Morph ologically,it iscompri sed of faulted basemcnt,givingahorst- andgrabenstructure.overlainbya relativelythinscdimcntarycoverranginginagefrom Valanginian10recent(Ercillnctal.,2008).Duringmost ofthc Latc Jurassic- Early Cretaceousit formeda platformotundefo rmcdpre-Mesozo icbasemen t,and was conncc tcd to thcF lc mishCap,fonningacoherentcontinentalb loc k,untilt heA lbian
(Srivastavaetal.,2000;Sibuctel al., 2007).Rillingandlocalizcdsyn-ritls cdimcntation intograbe nsoccurred fromthe ValanginiantoAlbian,and movedfrom the eastto thc westduringthistime.Thisdiachronousriftingrcsultcdinabasinal easternintcrior and a promin entbasementridge at thewesternmarginoftheGali ciaBank,thus creating a localizcd barrier forsedimcnlslravellingwcslward fromtheIberian Plateau Ilircillact al., 2007).
ThcOrphanBasin isactuallycomprisedof twohal f-grabenriftbasinswith highly attenuated pre-riftbasem ent.These arcthe\VestandEastOrphan Basins,w hichare
tcmpora llydi stinclandareseparated byan cast-d ippinglistricdetachmcnt. callcdthc WhilcSaiIFault(Chianet al.200 1;Enachcscuct.al, 2005)(Fi gurc s1.1. l.7and I.S ).
The basinboundingfaultto the west.whichseparates the Orphan Basin from the undcfonncdBonavistaPlatfonnl NewfoundlandShclf,isc onsidcr cdacontinuationofthc deep listricfault along the westcm margin ofthe Jeanned' ArcBasin,t oth c south (Enachc scu clal.,2005;Hardy,2008). ThcEast Orphan Basinistheolderpart of the basin.containin g syn-and post-rift success ionsfromtheTriassi ctoCenozo ic;whereas the WcstOrphanBasin contains syn-u nd post-riftfillthat isn ooldcrthanAlbian (Enachescu ct.al.2005) (Figure1.8).Thc gcology and gcologicalcvoluti on ofth c OrphanBasin isdcscribed later in thisch aplcr.
TheOrphan Knoll is anunde r-extendedcontinentalfragmcnta tt henortheastern corncro f theWest Orphan Basin (Figures1.7and 1.8).Ithas subsidedmuchmore than theFlemishCapandisoverla inbyTertiary.Mesozo icandLowerPalcozoic scqucnccs.
TheMesozoicrocksinclude some Baj ocia n agedterrestrialsandstones andrare coals, implyin gthatthe Orp ha n Knoll wasexposedup until themid-Jurnssic (Ruff manand van IlinlcI970; vanll inte etal.1995).ltispostulatcdto havc bccn corrcctcd to thc PorcupincB ankpr cccdingbrcak-up (Vcrhocf and Srivastava. 1989).
The Porcupine Basin isa large and deepnorth -south oriented extensionalrift graben.located offshorewesternIreland .butonce waslocated alongside theOrphan Basin,andIt hasbeensugges tedthat both oft hese basins compriscdacoherentbasin untilthe Aptian break-upbetweenthe North America andNorthernEurope(Massonand
Miles, 1986; Keenet.a l,1989;Enaeheseuet.a l,2005)( Figure l.7).lt isboundedtothe easl,nort ha ndsoulh bydeeperuslalno mla lfaults,which lie adjacent 10 theIrish Platform. SlyneRidge andPorcupine Bank,respectively.The Porcupine Bank,fonning thcwcstcmboundary .i sanundefonncdbascl11cntplatfonnthatwasconn cctcdtothc
Orphan Knollcontinentalfragmenl beforebreak-up(Verhoefand Srivasta va,1989).To theso utheast it is borderedbythe GobanSpur,and tothesouthwestbythecontinent- ocean boundary (TaleandDobson,1988;CrokerandKlemperer,1989).lteonlains Triassicto EarlyCretaceou s syn- and post-riftsuccess ionsand Mid Cretaceoustorecent posl-ritlfill slraligrap hically similar lo lhose presenl in lhe Jeanne d'Arcand other OffshoreNewfoundland Basins (Croker and Shannon, 1987; Tale and Dobson,1988;
Sincla ir 1995).Duringlh e Tilhonian-Berriasian,sandswere depositedmainlyalong the margin s ofthebasin. as alluvia lfans in the northanddeep water turbititcfans in thesouth of the bas in (Johnslone t.al,2001;Robinsona mICanham,200 1).During lhe Valanginian-Aptian,thePorcupineBasin waslargelyfullymarine,unliketheJeanne d'Arc basin atthistimc,rcsultin ginthcd cposition o f shcl falmudstoncs, siltstones and minorthin sandstones intheNorthand progradationofdeep marineturbiditefans and shelfciaslies inthesoulh (Jo hnstonelal.,2001).S andsdeposiledinlol he Porcupine Basin during theLateJurassic arcthoughttohave been from theIrishPlatform. to the easl(Jo hnslonela l.,2001;Smilhand lliggs,2001).
TheCelticSea basinseomprisea series ofsub-parallel east-westorientedfault- bounded half-grabenrift basinslocated to thesouthof theIberianPlatcau.and northof theComubi anPlatfonn(Figurel .7).TheyinciudetheFaslneIB asin,lheNorthCeltic Basinand theSouth CelticBasin.TheWesternboundaryof thesebasi ns,especiall ythe
easternedgeof theFastnetBasin,arecharacterizedbythinning strataalongthe eastern edgeofthe Fastenthigh,tothewesL ThenorthandsouthCelticBasinsarc dissectedby basementhighs;thePembrokeRidge,anextensionoftheWelshPiatfonn,inthe east,and theLabad ieBank inthewest. They containsy n-and post-rifts uccessions.withages rangingfromPermo-Triassictomid-Cretaceous andal.ate Crctaccous andTertiary post- riftsuccess ion.broadlysimilar tothosetheJeanned'ArcBasin(MiIIson,19 S7;Petrie et.
al.19S9) .Riftingandsyn-riftsandstone depositionoccurred mainlyduringtheBerriasian totheAptian,duringwhichtime stackalluvialfansbuiltup,mainlyon the northern marginof theCelticbasins .Mo stmaterialisthoughttohavebeenderived fromuplifted
parts ofsoutheastIreland,tothe northeastof thebasins (Petrie etal.,1989}.
The GobanS pur is amarginal plateauthat hasbeenhighlynmltedduri ngthe Mcsozuiccandislocated southofIreland.east ofthePorcupincBasin andsouthwest of therastnetbasin(Figurel.7).ltisconsideredt o bc a continuation ofth eCornubian Platt'onnto the cast,anddu ringthelateJurassic-Early CrctacCOliSW3Sprobably
connected to theFlemishCap(DingleandSerutton,1979; Masson and Milcs,1984, 1986;Kecn etal.,1989;Verhoef and Srivastava,1989).Ashallowandrelative lysmall Mesozoicbasinformed ontheGobanSpur.which hasEarlyJurassicto Early Cretaceous syn-riftsediments;however,duringtheLatcJurassic,thebasinwasupliftedalongwith the restoftheGobanSpur.Outsideofthe Basin,theGoban Spuriscoveredonlybythin tertiarypost-riftstrata,andthuslikely existedas anexposed bascme ntplatform duringthc Mesozoicriftingevents(Dingleand Scrutton, 1979; Colinetal,1992}
Inadditiontosomc of thc bascmcnt platformsmcntioned above,mosto fthc
Plateaus,incl udingmainlandandshelfareas.are thoughtto hav ebeen expos ed during thistime(Zeigler ,1989) (Figur e1.7).Someapatit etherm obarom etrydata exists with regard stoupliftofsomeof these areasduringthel.atcJurassicro EarlyCretaceo us.
lIend riks et al.(199 3) showthat thelong rangeinlierofWestern New foundland was expose d bytheLateJurassic, andHolfordetal.(2009)showthat cpisodesof uplift in Irelandoccurrcd in themid-Jurassic and theEarly Cretaceous.Ac cording to Turrinand Hemm ing(2000 ).basement ontheIberianmarg in.north of theLusitani anBasin, expe rie ncedupliftduringtheLateJurassicto EarlyCretaceous
I.4Pre-l\l esozo icBasem ent GeoIOt'\'
The pre-M esozoi cbasementgeologyandgeneralpaleogeograph icreconstructions forthispart oftheNorthAtlanticareoutlinedinFigures1.9and 1.10.The follow ing sectionis a descriptionof thepreviousstud iesof ofTshoreandonshorepr e-Mcsozoic basementwh ichcouldhavebeenexposedas source areasforde tritusduring theLatc Jurassic andEarlyCretaceoustimes.Isotopicage constraintsarcalsogivenfor corre lationstodetrit alzirconU-Pbgcoc hrono logyfromthis studyinlatercha pters .
/.4./Norlh AmericanConjugatei\largin
Themostproximal pre-Mesozoicbasem entin the underlyingtheGrand Banks
andNortheas tNewfoundlandshelf ispart of theeoproterozo icAvalonzone,which spanstheareafromthe Charlie-G ibbsFracture Zonesouthtothe Coliector Anomaly (Hawo rthand Lef ort,1978;King et al.,t985,19 86;Wiliiamsel al., 1999 ).The Avalon
Major Igneousoecwenees
:==-...
~::=.... :\::;".:. ~:::;::=:,::.~...
•8at.Moc...-.;... ,
Major IgneousOccurancn
:=::- ~==- ':"::::':":~::==-::'-~
_ _ I
zoneonshore and offshoreiscompri sed ofNeopro terozo icarc-phasevolcanica nd magmaticunits,lateNeoproterozo iccover sequencesandearly Paleozoiccover sequences.Arc-pha seigneous rockshavebeentraced in tbe offshore acoustic basement usingmagnetic anomalies;how ever,withale w exceptions(e.g.theFlemishCap), Precambrian igneousba sernent has not been encountercdasPr e-Mesozoicsub crop (Hawort hand Lefort.1978;Kinget al.,1985).TheLate Neoproterozo iecover sequences presentin the onshore presumably extendandsub-cropofTshorealongtheeastern margin oftheBonavistaPlatform . the CentralUplillarea.and beneath the shallowcover sequencesof theFlemishCap(King etaJ..1985;Bellandllowie. 1990).EarlyPaleozoic (CambriantoSilurian)c1asti c cove~ seq uences occurinthenortheasternand \\'estenl
Grand Banks(AvalonUpliftand BonavistaPlatform areasj.on the shel f andslopear ea beneaththeWest Orphan Basin aswellasbeneaththeNorthern Jeanned'Arcand Flem ishPassBasin (K inget al. .1 986;Belland llowie.1990) (Figures 1.9 and J.lO).The Cumberland ridgehasbeen interpretedasavolcanic mountainrangeformedastheresult of eitheraHercynianshearzone (LefortandHaworth.1978;Haworth and Lefort.1979;
Enaehescu .19 87) oramaficc omplexin volvedinth eAc adianOrogeny(Ja cobiand Kristotlerson.1981 )or simplya s aMe sozoictra nsferzoneth atfonlleda complexchain ofbasemeothorstsduringextension (Enachcscu,1987).
Arcphasemagmaticand volcan icigneous formationsof theexposedAvalonzone inEasternNewfoundland,includingtheRockHarbou r, Marystown and Harbour Main Groupsand Hollyrood Granite.have U-Pbzirconagesrangingfrom 586 to 632 Ma.One unrelat ed outlier.theWandswort h Gabbro of theBurio Ophio liteGroupon theBurin Peninsula.wasdat ed at763±2.2Ma (K rogh et al.•1987).Baddeleyitefrommalic sills
onCapeSt. Mary ' son theAvalon Peninsula wcredaled lo441±2Ma,indicatingthc occurrenceof localizedSilurian orog enic volc anic rocksin the AvalonZone (Gr eenou gh el al., 1993).Precambriangra nodiorite has beensampledon thefiemishCap,which yicldcddiscorda nlU-Pbz irco nages with uppe rinlcrceplso f75 land833 Ma, representingan age ofintrusionbetw een 750Ma and 830 Ma.Itisinterpreted to represent anofTshoreextensionof the AvalonZone; albcitonc thatpotentially represe nts an oldermagmaticphase (Kingetal.,1985).
Neoproteroz oicclasticseque nces.includin gthe Conce pt ion.HarbourMain.
Marystownand St.J ohn'sGroups arcextcnsivcly cxposcd onshore;h owcvcr.thcir ofTshorcbasemen tsub cropextens ionsarepoorly constrainedanditappears thatearly Paleozo ic coversequencesoverlyPrecambrian basemcntotTshorc(Kingctal..19X6).
Thcrcarc only scvcral locationsoffshorc whcrcAvalonianP rccambriancovcrscqucnccs havebeencoredinthcpre-Mesozoicsub crop:the VirginRocks-EasternShoals area (eastof theJeann ed'ArcBasin) ,andon theFlemishCap(Lilly,1966; King etal.,19 85).
Detritalzircons from the Precambrianmainarc-phasesediments (ConceptionGroup) arc dominantly570-620 Ma.Youngerarc-platformtransition sediments(Musgravcto wn and St.John ' sgroups)containdominantly 600-650Madetrital zirconswithveryminor MesoprotcrozoicandPaleoproterozoicdetritalzircons(Pollocketa1..2009)
The Cambrian-Ordoviciansequences present olTshorcarcconsideredanalogoust o thosepresent ontheAvalonPeninsula,parti cularl yfromtheBcll IslandGroup in thc Conceplio nBayarca (King eta l.,1986). ThcCumberian d B-55 wcli pcnelrateda lmost 400mof O rdovician shalesandsiltstones.and theLinnet E-63pen ctraled320 mof LowcrPaleozoicshalesandsiltston es.Kyle L-II,intheFlemi shPassBas in alsodrilled
throughalmost700mofmetasedimentary basement rocks(C-NLOPB.2004).Detrital zirconsfrom theequivalentCambrian-Ordoviciancoversequences on the Avalon Peninsulaaredominantly NeoproterozoictoEarlyCambrian(500-680 Mal in age:
how ever.Mesoprot erozoie(1.0-1.6Ga),Paleopr otcrozoic(1.9-2.3Ga)andminorLate Archean(2.7-2.8Ma)d etrital zirconsarcalsopresent (Polloeketal., 2009).
The Cambrian-Ordovicianmetasedimentaryturbidites andassociatcdLate DevoniangranitesoftheMeguma Zonearc presentbeneaththesouthern GrandBanks.
andcomprise thepre-Carbonif erousbasement oftheAvalon Uplift.Thisis supportedby tracingofsubsurface magnetic anomalies;inparticular.the Collector Anomaly.which is anextensionofthcCobequid-Chcdabuctofaultzone inNova Scotia.representingthe boundarybetweenthe Megum aandAvalonzones(HaworthandLefort.1978)(Figures 1.9and 1.10).A K-Arwhole-rockisotopic ageof 376±17Maof'granite basement'at thebase ofJaeger A-49also supports thepresence of theMcguma Zonc in thisarca,asit isknownto bcuniquely abundantly intruded bysuchLateDevonian (Acadian)granites (KreugerEnterprises.1972; Clarkect al.,1997;Kontaketal..2004 ).Detritalzireons taken fromtheGoldenvilleForm ationmetasediments of theMegumaZone inSOlithem NovaScotiahad predominantlyLate Neoproterozo ic(550-750 Ma).Middle Palcop rotcrozoic (2.0-2.2Ga)andasignificantamount ofArchean (2.8-3.0Ga)ages (Kroghand Keppie,1990).Furtherstudiesofa younge rsequencein theMeguma Zone yieldedsimilar dctritalzirconages.except lackingArcheanagedgrainsandhavinga smallpopulation of rareMesop roterozoieaged grains (1.0-1.2Ga)(White etal.,2008) Metaluminoustoperaluminous granitesarecommon in theMegumaZone andareMiddle toLateDevonianinage(380Ma-365Ma),correspondingto emplacernent duringthe
Acadianorogcny(Clarke eta l.,1997,KontakclaI.,2004).Metamorphic andgranitic tourma linesoccurabundantlyinthemetasedimentary andgranitic rocksof theMeguma Zone, respectively;with metasedimentary grainsmorecommonlyhaving schorl-Iike
compositions,andgranitictounnalincsmorecommonly havingdravite- Iikecompositions (Raes idect al.,1988;Clarke ctaI.,1989).
Rocksof theCentralMobileBelt.comprisingsedimentaryandvolcanicremnants oftheIapetusOcean.occurincentralNewfo undlandandextendaspre-Carboniferous bascmcntofTsh orcnorthwestof thcCharlie-GibbsFractureZonc(Figures1.9 and 1.10).
Theypredorninantlycomprise Cambrian to Siluriansedimentary andmetasedimentary rocks.volcanicrocksandgabbros.aswellasSiluria ntoDevoniangranitcs.Dctrital zircons fromaCambrianagedlowgrademetasedimentaryunit(theJonathansPond Formation)along thecastcm portion of thcCentral MohileIlelt inth eGanderZoncof New foundland havemainlyMcsop rotcrozoic(1.0-1.3Ga),Palcoprotcr ozoic(2.0-2.2Ga)
andArchean(-2.7Ga) ages.with theexception ofasingle LateNcoproterozoic-Early Cambrian (-540Ma)grain(O'Neill1991).Furthcr eastin thcCcntralMobilcBclttfrom within theExploit Subzone)LateOrdovicianto Siluriansedimentary successionscontain
detritalzirconsdominatedbyOrdo viciantoLate Neoproterozoic (450-550Ma), Mcsoproterozoic(1.0 - 1.5 Ga),LatcPalcoprotcrozoic ( 1.6-1.8 Ga), andm inorLatc Archean(2.7-2.5Ga)ages(Pollocket aI.,2007).Magmatic rocks in the Central Mobile
Belthaveages rangingfromLateCambrian to Early Devonian.andgenerally.rhe ages of theseinlrusiverocksb ccome oldertowards thcw cst;howcvcr. graniticand volcanic rockswith U-Pbages ranging throughl.ateOrdovician andEarly Devonian arccommon throughout centralNewfoundland (Dallmeyerctal.,1981;ChorltonandDallmeyer, 1986;
Dickson,1990;O'Neill,1991;Dube etal.,1996; Valverde-Vaqucroct al.,2003;
Valverde- Vaquero et aI.,2006).LateDevoniangranites arc rare.butdo alsooccur in the GanderZone(Currie.1995).Metamorphic tounnalincsarc ubiquitousin metasediments adjacent to granitesandfaultzones inthe GanderZone (O'Neill,1991).
containCarboniferouscontinentalcias tics.andhavcbceninterccptcdby severalofTshorc
wells (Figures1.9 and 1.10).HareBay E-21,loeatedonthe shelf areaof theWest Orphan Basin,penetrated almost1500mofPennsylvanian red-brownsandstonesand siltstones.
Thesemay be equiva lent to theupper\Vindsor Groupand basalCanso Group exposedon mainland Nova Scot iaandNew Brunswick(BPCanada,1979;Belland Howie,1990).
UpperPaleozoic(Devonian- Pennsylvanian)coversequences arcalsopresentwithin a largecast-westtrending syneline belowthe centralGrandBanks (on the AvalonUplift) andoffshoresouthof theAvalonPeninsula.Thesearc intcrprctcdto includc thc
Devonian-MississippianshaleandsandstoneoftheHorton Group,Mississippian evaporatesandshaleofthe Windsor Group,Mississippian -Pennsylvanianred shaleand
sandstoneofthe CansoandRiversdale Groups,andPennsylvanianred sandstoneand shale ofthePictouGroup(Barssetal.,1979;Belland Howie,1990).On mainland Nova Scotia.ages of detritalzirconsfrom theHorton GroupinthelatePalcozoicStMary's Basin cluster in a bimodalmannerintoNeoproterozoic (550-700Ma)and Paleop roterozoie (2.0-2.2 Ga) agegroups,andare interpreted to be derived mainlyfrom uplifted portionsoftheMegumaZone.MinorDevonian (370-380 Ma)and Silurian (411 Ma) detrital zirconswerealso present(MurphyandHamiiton, 2000).
A LowcrPaleozoiccarbonate sequencehasbeeninterpreted ontopof partsof the OrphanKnoll;basedon angularOrdovicianand Devonia nlimeston ecobblcsdrcd gcd fromshallow depositsncarthetop of thc Knollthatarc considercdtobe insitu fragments (vanHinte etal., 1995).Theymay correlate with theLow erPaleozoic Carbonates otTshore wes tcma nd northcmcwfoundland that fonnc do n the pass ivc Laurentian Margin andsubs eq uentPaleozoicforeland basins.Howe ver, geophysiculevidcnce suggests theOrphanKnoll ismostlikely afragme nt of the Avalon Platform (Haworth and Lefon ,19 78) eoveredinplacesb yM esozoic sedim ent s( Enachescu etal., 2005).
Anumbcrofwells offshore haveinterceptedMesozoic syn-rifrigneous rocks, includingagranitic rock inthc\Vcst OrphanHasinundvarious Mesozoicsyn-r ift volcanicsinthc southcma ndccntraIGrand 13anks.Thc13onavistaC -99\vcllin terccptcd IOOm o fgranitc and/orp egmatiticgranitc which yicldcd a K-Ar wholc-rockisotori cagc
ofI46±6Ma (UPCa nada,1975).Triassic-Jurassicbasaltsw ereenco unleredin SpoonhillC-30andCorrnorantN-83wells;howeverthese basaltshavenot been dated (Amococt aI.,1973;Jansa andPc-Pipcr,1986).IntheSouthemGrand Uanks, sevcral wcllsintcrceptcdLa te Jurassic-Ear lyCrctaccous volcani cro cks.In13rantP-87.5 5m of basaltandpyroelasticsand 123 mof diabase sillsorIlowsweredated atI35±6Ma.ln TwillickG-49, a15 mthick porphyriti cdiabasewasdated at177±5Ma.lnE merillonC- 56,a2 I mthick diorile dy kewas da leda t96 .4±3 .8Ma.A llo f theseageswere detenninedbywhole rockK1Arisotopic ratios (Jansaa nd Pc-Piper,1988). Thelludgell lIarbor Stock . a small alkalineultramaficplutonlocated on landinCentral
ewfoundland, hasa K-Ar biotiteageo fI39±9 Ma( lI elwig eta l., 1974)
/.4.2/rishConjugateAfargin
Becauseof theproximit y of the Irish andIberian conju gatemargins duringthe lime which theunitsfromthis study were deposited,Iheywould have been potential source areas.Therefore.itispertinentto summarizethcgeologyoftheseareas,with emphasison anycrustalagesthatcould be usedtodiscrim inate sourcingfrompotcnti al Europeanhinterlandsintheseareasfrom thoseontheorthAmerican conju gatemargin, usingdetritalzircongeochronologyastheprimaryproxyforprovenanceanalysi s.
The pre-Mesozoicb asementge ology ont he lrishc onjugate margini slargely comprisedofEarlytoMiddlePaleozoicsequencesfromtheclosure of the Iapetus (analogous10theCentral Mobil eBeltinNewfoundlandjthatislargely overlainbyLate PaleozlIie(mainly Carboniferous)c1asliesandearbonales(Figures1.9and 1.10).SeYeral largcplutons and batholithsare presentthathaveLateSiluriantoE arly Dc vonian agcs.
Thelarge stof theseexposedplutonsisthe GalwayGranite,which hasV-Pbzircon ages
belween395and405 Ma(EarlyDevonian)(Fccly et ul.2004).Othererystalline basem ent exposureson thcIrish Mainlandareolder(EarlyPalcozoicand Mesoproterozoic) andsparsely exposed.Magmaticrocksfromwithin theSlishwood Divisionof theDalradian Supergroup inNorthwestern Irelandhave EarlyOrdovicianU- Pbzireon ages ranging belween4 67±6 Maand474±5M a(FllIwerdew el al.,2005).
The Annagh Gneiss,whichstructurallyunderliestheDalradian Supcrgrou p in Northwestern Ireland,haslateMesoproterozoic U-PbZirco nageswithaweighted mean age of963±8Ma (Daly elal., 2005).
TheolTshorepre-MesozoicbasemenIgeology is poorlyconstrainedon thc lrish conjugate margin.Presumably.the pre-MesozoicbasementunderneaththePorcupine Basin.Porcupine Ridgeand Galicia Bank areasformsacontinuation alongthe Caledonian-A ppalachianlrendandlapetusSutureZone,ineluding(fromsoutheast to northwest)partsof AvalonZone, Centra l MobileBelt,Laurentian margin, andGrenv ille ZOllc(Figurcl.8). ThcC larcLincamcnt.amajorc ast·southcast-wcst-northwcst trcnding struc turethatdissectsthe Porcupin eBasin,has beeninterpretedas a trans-A tlantic
boundarybetween AvalonZonebasement,to thesoutheast. and CentralMobileBelt
basementtothe northwest(Johnsonelal.,2001) (Figure1.9 and 1.10).There iseviden ce tosuggestthepresence of Carbonif erou scover sequences aspre-M esozoicbasementin the area aswell.Althoughno Carboniferou sbasementhasbeen drilled,reworked Carbonifero uspalynomorphshave been found in EarlyMesozoicriftrelated clastics in thePorcupin eBasin.indicatingthepresence of nearbyCarboniferous-agedso urces (SmithandHiggs,2001). Addil ionally,apotentialMesozoic source ofdctri talzircons exitsolTshore Ireland.The Porcupi ne Medianhigh,a3-5kmthic kseismicallyimaged featureinthe centre ofthePorcupine Basin.hasbeen interpreted asan igneous featureo f Berriasian to Valanginianage(Earliest Cretaceous) byTaleand Dobson(1988);h owcver, thisfeature hasnot been sampled.and therefore its age. andcomposition,isunknown.
Johnstonet al.(200 1)suggest a younger age, probablyAplian andcoincidingwith early seafloorspreading,forthePorcupineMedianhigh
JA.3Iberian ConjugateMargin
Paleozoic granitoids constitutemuch of thebasementpresentin theIberian Penn insula.particularlyin thenearest areas on the northv..'estem IberianPennsinsula, where theymake upmost of the exposedrocksof theVari scanCentralIberianZone (Figures1.9 and1.10).TheU-I'bagesof these granitoidsarc predominantlyLate Palcozoi c. and wcrc generatcd duringthrcedi stinct time illtervals:Mississippian (330- 320 Ma),I'cnnsylvanian (310-300 Ma),andEarlyl'enn ian (290-28oMa) (I'riem and Tex, 1984).Additionally,olderbutlesserexpose d EarlyOrdovician gniesses arepresentas pre-Varsicanbasementin the area. with V-Pbagesrangingbetwee n 460 Ma and 490Ma (I'riemandTex,1 984;V al verde -Vaqucro andDunning, 2000 )
interprctcdtobeundcrlainbypr c-Mcso loicbascmentcomprisingextensions of thc Ccntrallber ianZo nc,largelyco mprisedoflate Palcoloi c( Carboniferous-Pcml ian) granitoids(Priem andTex,1984; Capdevila andMougenot,1988).lIowever,thc continentalslope.includingtheGaliciaBank.has been interpretcd tobe underlain by extensionsof theOssaMorena Zonebased on lithologic comparisons toonland equivalents(Capdevilaand Mougenot,1988).On land ,theOssaMorena Zone predominantlycontains Neo proterozoic metasedim entary rocks,aswell as intrusiveand
volcanicigneousrocksthat formedduringthreemagmat icphases:587Mat o 535!\1 a (Neoproterozo ic),530Ma to 470Ma (CambriantoEarlyOrdovician)and359Mato 330 Ma (Mississippian)(Romeo cta l.,2006 ;Solaetal., 2008).
Mesozoic syn-riftvolcanicrocks are alsopresent on theIberian Margin, mostof whichare presentfartothe southwithinthesouthc m Lusitan ianBasinonlandand offshore .The volcanics arcpredominantlymafi c andoccurredi nfourdistinct cycles:
LatcTr iassicl o EarlyJurassic (203-224 Ma), EarlyMiddlcJurassic (160-190 Ma),Early Crctacco us(13 0-135Ma),aodLate Crclacco us(100-70 Ma) (p inhc iro ct al.,1996).
Additionally,metamorp hosedMesozoic syn-riftgabbro sillshave beenencountered on thc contincntalslopc on lhcwc stcm cdgc oft hc GaliciaB ank, andh avc a U-P b agc of cmplaccmcntofI22±0.3Ma(Schacrcrcta l., 1995).
1.5 Geolog\'andgeologice \'olutionof theFlemishPass Ha sin
/.5./Localioll lllld Regiolla/Ge% g)·
ThcFlcmish PassBasinisi ocatcd approximatcly4 00 km cast ofS aintJohn's Newfoundland. undertheFlemi shPassbathyme triclowbetweentheFlemi sh Capand the GrandBanks(Figure 1.1).Itcovcrsa nareaofapproximately30,000km'andoccursat ocean depths ranging from 400to1100m (Fostcr andR obinson,1993;DcSilva. 2000) Struc turally. it isuhalf-grabenthat formedduringLateTriassictoEarlyCrctaccous rilling.Thcdcpthtob ascmcntinthcFlcmishPassBasin isabout IOtol 5 km.lli s bou nded(a)tothcsouthwest bythc CcnlralRidge , (b) tothecastbythe BeothukKnoll- Flcm ishCap bascm cnthigh,(C) lothcnorth by lhc Cumbcrland Ridgc,and (c )tothe south bythe AvalonUplill (Enachescu etal.,1987;Foster andRobinson,199 1;DcSilva, 2000).Itis thc outcrha lf-grabcnof thc"doublc-failcdrill",which alsoincludesthc Jcanncd'ArcBasin hal f-grabcnandthc Ccntra lRidgc horslto thc wcst(Enachcscu,
1987) (Figure 1.3).Thc CumbcriandIlclt Fault Zone is not strictly a barri crbctw ecnthe FlemishPass andEast OrphanBasin.Scismic stratigraphiccvidencesugges ts thatthe FlemishPassBasinforms aterra ce ofthe EastOrphanBasin. and bothbasinsar e interpretedtohave been connectedthroughmuchofthc ir rift phasedcvcloprncnttime (Enachcscu et al..2005)(Figure1.5).
/.5.2Te('t()nicandGeologic E:~'()luli()n
TheMesozoicandTertiary geology andgeologicevolutionof theFiernishPass Basinisdescribedin detailbyFoster and Robinson (\993).Thcfoilowingsection is a summary oftheir work ,Theirgeneralizedstrat igraphyof theMesozoic riftand post-rift sequencesis shownin figure1.11.
fourbroad seque nces.Theseinclude(I) Late Triassicto LateJurassicsyn- and post-rift:
depositsoft heTethys rift stagc(MSI).(2)Berriasian to Aptiansyn-andpost-rift dcposilsofthcNorthA tianticrift sta gc (MS 2).(3)Aptianlo Albian syn-riftdcposilS of the LabradorSeastagc (MS3).and(4) Late Cretaceousto recent post-rift thcrrnal subsidence deposits(PR).Thefirstthree sequencesarc localized in fault-bo unded depocentr eswith difTering orienta tions.Duringmost ofthe LateJurassicto Early Cretaceous.depositionofsyn-r iftclasticswas confined to northernandsouthern subbasins. referredto asthe Baccalieusubbasinand the GabrielSubbasin.respecti vely (FosterandRobinson.1993).Thisproj ect focuseson thedepositionofreservoir
and prospect iveMizzen0-16wells (Figu re1.12); although thc oricn tationufdcposition ofcoa rse clasticsintotheBaccalieu subba sin s shouldalsohave implicationsfor thc depositionof coar seclastic sintotheGabrielsubbasin
TheTeth ys stag eseque nce(MS l; from Fostcr and Robi nson1993) islocat ed between thctop ofth ccc onomic basement and a regionalnon-crosionalu ncon formity that record s anabru ptcha ngefromshallow marine to opendeep marinedeposition.
Verylitt lehasbeen establishedabout thelowerp art o f MSI (LateTriassicto
EarlyJurassic scdirnents), duc to alack of wellcontro l and poorrcsolution inseismic sections. However,itislikelythattheyarc similar totheir countcrpartsinth cJcann c d'ArcBasin. and include eq uiva lentsto theEurydice.Argoand Downing Fonnations (redbeds.evaporites.and marine mudstones.respect ive ly).Iiisunclearwhether massive saltan dsa ltst ructuresa re prescnt.a hhoughvariousauthorsstudy ingse ismicsectionsof
the FlemishPassl3asinhavcalludcdtoth cirprcscnce ( Ench cscu,1987;Kccn etal.,1987;
Fostcr andRobinsonI993).
ThcKimmcrid giantol3crri asianscdim cntary sccti on o fM SI(MSI-5O)i s wcll constrained fromwells andseismicsections.MS I-50is generallyinterpreted to comprise post-riftdep osits of thc Tethysriftin g stage overlainbysy n-riftdcposits of thc North
Atlantic rifting stage (Foster and Robi nson,1993;DcSil va,2000).MSI-50fills two cast- westtrending subbasins.inciudingthcUaccalicu subbasin.toth en orth(Fi gurel.12 ).Th e
FlemishPassBasinduringthisperiod.associatedtomovementbetween NorthAmerica and Africa,and increased riftingbctwcc n Ibcria andth e Grand Ban ks.ThcbascofMo l- 50isdefi nedby aKimm eridgian Unco nfo rm itythatrecordsonlapo fsedimcntary rocks
southernsubbasi n.MSI-50i s charactcrizcdb yth cBaccal ieu1-78 wcll.jnwhichthe section formsashoalingupwardspack age, comprising.frombottomtotop:marine shales,shallow marine sandstones interbeddedwithshalcs.overlainbythicknon-marine sandstones.Asimilar changeupwardfromopen tornarginalmarinedepositionhasbeen interpr etedfortheMSI -50sequence thro ughouttheFlemishPassBasin(Fosterand Robinson.1993).Sourcerocksoccur in thelower partof MS I-50. andarcprcscnt inthc Baccalicul-78andMizzcnL-11wclls(Fostcr andRobin son,1993;DcSil va.2000;
Enachcscuetal.,2005).
Thesecondrift parascqucnce,MS2.ranges in agefrom Valanginian toAptia nand isvery we llconstrainedby wellandseismic data.DepositionofMS2 occurredduring a bricfpost-rifisubsidence phasefromtheValangini anuntil theHauterivian-Barremian, andthenduringtheLabrador Sca rift phascuntilthcApti an.Thcciastic dcpositsof MS2 arc relati velythickintheBaccalicusubbasin,whichat thetimeo fdepositionhad aN E- SWorientation(figure1.12).Theorientationof thisbasinind icatcsnorthwest-southcnst directedextension in theFlemishPassBasinduringthisperiod•assoc iated toriftingand incipientbreakup betweenthe Grand Banksand Iberia.Itwasalsoduringthisperiod whenthe supracrustalFlemishPass andVoyage rboundaryfaults weremostactive and most ofthcdccpcningofthcFlcmishPassBasinoccurrcd(Enachcscu.1987;Fostcrand Robinson,1993)(Fi gurc1.l 2)
ThebaseofMS2isa regiona l unconformityrepresentin gregion alsubsidenccand onlapofscdimcnts.T he topoftheseq uencc is defi ncdby anero sionalunconfo nn ity,and
in the Gabrielsubbas in,wherea lower sub-seq uenceof mudstonesand turbiditiesis overlainby an uppersub-sequence of prograding coarse clasticwedgesscparatedbyhigh standshaleintervals.Thelower sub-sequence record searly syn-rift passiveclastic deposition.Theuppersub-sequence record smultiplc syn-riftshclf'progradations,sourced from thenorth-west. TheBaccalicusubbasinlacks aprogradin g shelfsub-sequence. and conte mporaneo ussedimentsarcfi nergrained andpoorlysortcd.rnost likclyrcprcscnting syn-riftelastiedepositinn belowwavebase(FosterandRobinson,1993).
Asa resultofa rotationtonorthe ast-southwestdirected regionalextensionin AptiantoAlbiantimesduringtheLabradorSeaphase,northw est-southeasttr cnding faults and depocent resin the FlemishPassBasinfonn ed .Thc scquenee from thisperiod.
MS3. wasdepositedbetweenandoutsideofthepreviousdepocentr esin theHaccalicu and Gabrielareas,mainlyin anarea thatwaspreviously abasement high.Therefore.the MS3scquence isnotrepresentcdinanywcllsinthcar ca.Prcviou sdepoccntrcswcrc oplill eddu ringthisperiod andth et op ofM S2 waseroded.The mainM S3d epoeentres contain llat parallelretlec torsthat onlapontobasinmargins and have beeninterpreted as mainlydecpmarinemudstonesand turbiditic sandstones.A channclizedzone hasbccn identified justto thc southeastof theBaccalieuareathatisintcrprctcd asthemain migrationpathwayfor sediments.The top of MS3 ismarked bythe regionalbreakup (pnstrift]unennf nrrnity andhasnotbeendated,but isprobablyAlbianinanalogyt o the Jeann ed'Arc l3asin(Foster andRobinson,1993 )
Thc driftstage sedimentsunconformablyoverly allof thc previousscquenccs in theFlemishPassBasins.Theyare more orlesslaterallyexten sive,andonlyfillshallow depressionsovcrMS3 subbasins.TheAlbianto recentdepositsrecordthe progradati onof
a clasticshel f fr ont fromthecast mai nly.butalsofromthenorthwest(Flemish Caparea).
interrupted byaregionalEocene tilting event(FosterandRobinson. 1993)
1.5.3Oil1I1UIgllspotentia l
InMay2004 the Canada-Ne wfoundlandand Labrador Offshore PetroleumBoard andtheGeologicalSurvey ofCanadapublished areportthatput the undiscovered rccovcrablcpctroieumreservcs ofth cFlcmishPassBasin at l. 7bilIi on barrcls.with expected fieldsizes rangingfrom 5281044millionbarrels (Enachesc u• 2006).The Flemi shPassBasin containsmatureLateJurassic sourcerocksand potcntialreservoir rocksof LateJurassicandEarlyCretaceousages.Nurnerous large structuraltrapsh avc beenide ntified in theFlemishPass13asinbyindustry 3-Dseismicmapping,including SOIl1Clarge faultedextensionalanticlinesandothersuch trappingsystcmsthatexceed Iliberniainsize(DeSilva,2000;Enachescuand Hogg,2006).
MatureLate Jurassic sourcerocksandheavyoil havebeendiscovercd in both the
interc epted164mof upperKimmeridgiansourcerocks with2.2to 3.6percentTOeanda
Hydr ogenIndexof395t0 391, indicative ofa TypeII,or rnarine-typekerogen (DcSilva.
2000;McCracken.2000).MizzenL-IIintercepted 5mofnon-commerc ialoilpayin EarlyCretaceo ussandstone,andas well Jurassic sandsto neswithexcellcntrescrvoir charaeteristics( Enaehescu , 2006). The GabrieIC-60w ell never penetral edt heLate
havc a gc ochemicalsignatu re that indicate dcri vationfrom aKimmeridgiansourcerock;
however.oncthatwasdepositedinamore oxidizingenvironment thantheEgretMember
intheJc ann ed 'Ar eB asin(Creaney andAliison,1987).Creaneyand Allison (1987) createda currentdaymaturitymapof theKimmeridgiansource rocksintheFlemish Pass
currentlyintheoilwindow.overlainbypotentialLateJurassic andEarlyCrctaceo us
Recentl y,StatoilHydrohas announced asignificantdiscovery atthe wellMizzen O-16,andsubsequentlyhasappliedfora signiliea nt discoveryIicensefromtheCanada Newfoundlandand Lab rador OffshorePetroleumBoard;however,thedeta ilsof this discovery, and of'thewcllitself.remainclassifi ed atthistime.
t.6GeoIOtJ" andfJeologica levolutio nof theOrphanBa sin
l.o.lLocationand Geology
TheOrphan Basinisthelargestand deepestof theNewfoundlandotfshore basins, coveringanareaof160,000km'and rangingindepth from 1000t 0 3000m.lteontains thicksyn-and post-riftMesozoic and Tertiary sedimentary intiIIoverlyingattenuated continentalcrustof the AvalonZone.Thehighly attenuatedbasement hasanaverage stretchingfaetoro f 2.5(Enaeheseuetal.,2005).The OrphanBasin islocated(I)southof the Charlie-GibbsFaultZone (CGF Z),(2) north of the Cumberland Belt FaultZone (CIlFZ),(3)west of theContinent-Oceanboundary (COB)and theOrphanKnoll-
rlcmishCapc lcvatcd lrcnd.and(4)castofthc llonavislaPlatformand the basin- bounding IlonavistaFaultIf'igure1.1).
Although the Cumberland 13eltFault Zone fonn s a cha inof bascment highs andi s considered thesouth cmlimitof theOrphanBasin, seismicstratigraphic interpretations indicatethatithasnot been anuninterru ptedbarrier throughthevarious phases ofthe basinevolutio nandsediment deposition .Localized basementdeprcssions probably
form ed.allowi ngcommunicationbetwee nbodiesof water(seasorlakes) in theNorthern
Jeann ed'Arc,Flemi shPass andOrphan basinsthroughouttheJurassic and Cretaceous (Enachcscu et al.,200 5)(Figure1.6).
The continent-ocean boundaryislocated approxi mate lyat the4000mbathym etric contour.There is approximately110 kmoftransitiona lcrustlandwardof theCOB, comprisingattcnuatcdcontincnla lc ms t madcupof highly tiltcd faultblocksofundcrlain by a shallow detachm ent surfaceandsepara ted locallybylinear ridgcs o fe xhumcd mantleperidotite (Kcarscy andEnachescu,2005)
TheBonavistaFaultisanorth west eontinuationo f thc Murre-Mer eurybasin- boundingfaultsystem,and defi nesthewesternlimit of extensioninthe OrphanBasin.
The BonavistaFault dips to the cast.and the dipof thisfaultzone varies fromsteepto shaliow along strikc ( Enachcscuct al.. 2005).
The basementstructuralarchitectureof the Orphan Basinisdomin atedbynorth- north east/south -southw est and north-southtrendin gelongatcbasement ridgesand half- grabens,formcdbyl argc synlhct icand ant ithcticfaultsto the basin-boundi ngfaultSome ofthc ridgcsandsub-basinlroughsarccomparab lci nsizct olhcCcnlral Ridgcand Jcannc d'Arc llasin(C hiancta l.,2001;Enachcscuctal..2005)(Figorcs1.I,I.5and1.8)
Based ont cctonic and strJtigraphic charnctcristics.thc OrphanB asin can bc
subdividedintotwolarge subbasins.theWest and EaslOrphanbasins.Theyare separated bythe While SailFault.a deeplypenetratingbasemen tfault.roughIyparallcltothe BonavistaFauh.thatt rcndsnorthcast-southwcstand dipstothc cast.ltisa continuation
(Chiane tal..2001;Enae hescueta l..200 5)(Figurcs1.1and1.8).Thelith ostratigraphy and Mesozoic geologi c cvolution o f thcEastand WestOrphanbasinsis bestdescribcdby Enachcscuctal.(2005).Sevcralmajorun con formitieshavebccndcti ned fromsci smic
interp retati on.undrcprcscntthctopsofthemajorse ism icscq uc nccs.Thcscinclude:(I) top of thepre-riftbasem ent (thepre-riftunconformit y ).(2)thetopoftheTriassicrifi seq uence. (3)Thetop oftheJurassic,(4 )thetopofEarly Cretaceous(a.k .a.thc Avalon or
"breakup"unconformity ), and (5) the Top of thcCretaceous or BascTcrtiary Unconfon nity.
13ascmcntarchitccturcdifl'crsin thc\VcstandEastOrphanBasins.The basem ent ridgesin the\Vcst OrphanBasinhavebeenerode dbytheBaseTertiary Unconformityas wellasbytheAvalonUnconf ormity.Thehighsarepartiallycovered byprc-rift Palcozoic sedimentary cover.andarcrarely alsooverlainbythinsyn-riftMesozo ic scdimentary cover.TheEast Orphan Basin cont ain sthickMesozo ic sed imenta rycove r, which ove rlies basement ridgc s.JurassicandCretaceous syn-riftsedimentsinthe EastOrphan Basinare structu rally complex,withrolloveranticli nes andnormalfaultingtha tarc attrib uted to movementofadjacentbasementblocks(Figur e1.8).
1.6.2Tectonic11l1dGeolog ic Evolution
TheOrphanBasinevolved over roughly160Million years, with fourmajorrifling
event s occurringatroughly210.150,120and 60M a (Enachcscuct al.,2005.).Rifling beganin the cast, andmoved westwardwitheachsuccessiveri ftingstage.The tirs tt hrec
rifl stagescorres pond to theregiona l Tethys,North AtlanticandLabradorSca stagerills:
the lastrifting stage istheLate CretaceoustoPaleocene East Green land stage.Each rif ti ngepisode wasfollowcd by aperiod of thermalsubsidence, with the most rapidand signilicants ubsidenceoccurringa fter thc finalriftingeventinthe Eocenc.Veryminor volcanicrocks havebeenidcntiti cdthroughoutthe entireOrphan Basin.indicatingthat theOrphan Basin was anon-volcanictailed rili(C hianet al.,200 1:Enachescu ctnl., 2005).
TheEast Orphan BasinfirstunderwentriftingduringtheregionalLateTriassicto EarlyJurassic Tethysriftstage, asindicated bythepresence ofLateTriassic andJurassic syn· riHsedimentaryrocks.TheTriassics cqucnccisonlyprcsentin theEastOrphan Basin, whcreit maycontain redb edsandstratitiedevaporites(Enachcscu eta l.,200S) Massivesaltstructures ,suchasdiapirs.havenotbeenidentified.Anearlytomiddle Jurassicpost-rilisequence isalso probablyprcscnl.TheDSDPsiteIIIwellon the OrphanKnoll intercepted MidJurassic (Bajocia n)continentaltomarginalmarinetluvial sandsto ncs (Ruffmana ndva nllintc.1970).During thcTethys riliing, the EastOrphan Basinwas connected to thePorcupineBasin ofTshoreIreland,and theFlemishCa pwas
duringthis stage.andacted as the basin boundingfault.The\Vest Orphan Basin was still
anelevated pcneplainedpart of the continent,andthe western riftshoulder.Sediments were mostlikely derived from this western riftshoulder,from southernupliftedareas,and
fromrotated basementblocks within the East OrphanBasin.The earliestsedimentswere deposited in alluvialandlacustrinesettings .This wasfollowed bythennalsubsidence, marineinvasion.and deposition ofmixed evap oritesandcontinentalclastics.
DuringtheLateJurassic toEarlyCretaceousNorthAtlantic riftingstagc,the East Orpha n rift wasreactivated.Astheregionalextensiona lvectorrotatedfro manorth-south toeas t-wes torientationduringthe North Atlantic riftstage,trans-tensioncaused defonn ation ofprevio us syn- andpost-rift sedimentary rocks in the East OrphanBasin.
The OrphanKnollwas emergen tat this timeandbecameasource ofproximal sedime ntation. Although the GrandBanksandIberia continenta l margins separa tcd duringthis stage, theOrphanBasin andFlemishCapremain ed eonneeted to the lrish conjugatemargin.Late Jurassicto Early Cretaceous(Kimmeridgian to Albia n) rift sedimentsfrom the NorthAtlantic riftstage arc predomin antlypresentin the East Orphan Basin. andextendintoseveraldeeper troughs.parts of theWestOrphanBasin.The presence oft hcse stratais supportedbyJurassic andEarlyCretaceousseismic marke rs thathavebeentiedtowellsin theNorth Flem ishPassBasin(Figure 1.5).ThcJu rassic10 EarlyCretaceo ussequence thickensin half-grabensandisprobabIymade upo f continentalsiliciclasticsand marine shales.analogousto thoseencount eredin wells ofth e
FlemishPass and Jeanned'Arcbasins.The EarlyCretaceo us sequence may alsocontain sandstones andshalesthatare analogousto thoseintheJeanned'ArcBasin.Additionally, paleogeographicrecon stru ctionsindicatethatthcEast OrphanBasin riftwas connected to the Grand BanksandIrishconj ugate marginviaa regiona lepeiric sea,whereorganic-rich
shallow marine shales(the regional oilandgassourcerocks) werewidelydepositc d duringtheLateJurassic(Masonand Miles,1986;Srivastavaand Vcrhocf,1992).
An Aptianto Albiansequence ispresent in both the\Vest and EastOrphan basins.
related theregionalLabrador Sea riftstage.Earlyin thisriftstage.a triple junction\v-ith three incipien tscafloorsprcadingccntrcsformedjust northeast of thc FlcmishCap.Thc threespreading centrebrancheswent (a) south,between GrandBanksandlberia.jb) northw estbetwee nNortheastNewfoundland/Labrado randNorthernEurope/Greenland, und tcjcasr.be tweenIberia andFrance.formingtheBay of Biscay.Evide ncesugg ests thatsignificantupliftandc rosioninthe\VestOrphanBasin occurrcdduringtheLabrador riliingslageduringwhi ch,TheOrphanKnoJland otheri ntra-basinb ascmcnlhighslikely becamcsourccsforlocaJlydcrivcdscdimcnts (Enachcscu ct al.,2005).Towardsthe end ofthis stage, duringtheAlbian,the western riftingmarginof theOrphanBasinmigrated westward past theWhiteSailFault,formingtheearlyeaste rnportionofthe\Vest Orphan Basin(E nac hcscu ctal.,2005).Thisritlingwasaccommodatcdby castward movcmcntof the FlemishCap micro plate.whichat thistimewas stillattached tothe conjugateGalicia Bank,focusingritling inth e OrphanB asin rathcrthanat thcc uITc ntAtlanticOcean
margin(Srivastavaetal.,2000;Sibuctc l al.,2007).Depositionofa syn-rift clastic sequcnccin thcWcstOrphan basin during lhisperiodissupportcd bylhc prcs cncc of Albia nsy n-rilisilicidasticsintcrcc plcd inthcBluc11-28wcJl(RobertsonRcscarch, 1979).Basedon furthcrseismi c studics,lheupper boundaryof this sequenceisthe regional brcak-upunconfonni ty.the AvalonUnconfonn ity,w hic hseparatesit fromthe overlyingLate CretaceoustoTertiarypost-rift deposits.Thelithostratigraphy ofthe l.owerCretaceous sequenceisinterpretedtoinclude siliciclast ics suchasmarinesha les
and deltaicand/orshallow marine sandstonessimilar toEarly Cretaceousdepositsin the Jeanne d'Arc and FlemishPassbasins(Enachescuctal.,2005 ).
Duringthe Late CretaceoustoPaleocene EastG ree nlands tage ,r ift ingmovemcnts
South of the Charlie-Gibbs Fault Zone,rilli ng wasmainl y confined tothe westernm ost part of the WestOrphan Basin.Duringthisperiod,clockwisedisplacem ent of theFlemish Capaccommodated further open ingofthe West Orphan Basin.TheUpperCretaceo usto Paleoc cne sedimentary sequencei slocated aboveth e Av alon Unconformity andbcl ow theBaseTertiary Unco nformity.and comprisesmostlymarginaltodeepmarine shales
and mudstones.The seq uence thins to the East,andistbickcst over the\VestOrphan Basin. Repcatedoblique-slipmovc ments alongth e Charlic-GibbsFaultZonewcrc
transmitted throughthe entire OrphanBasinviasmallcrtransformfaults. cau sing basement block rotationsaswellasuplift,erosionanddeformation0fearlierMesozoic syn-riftsedimentaryrocks.
Inthc Early Tertiary,thc entire OrphanBasin underwent rapidsubsidencc.
followedbyprolongedsubsidence andpassivemargin scdirncntation.TheTertiary sequence comprisesthermal subsidence-stage deep marinesha lesdeposited onthe current passivemargin.This sequence isthickest over theWest Orphan Basin. where itsaverage thicknessin4km.Over the East OrphanBasin,the average thicknessiso nly approximately 2km(Chianetal.,200 1:Enaeheseu ela I.,2005).
