during aca.lrncl fall, whcroaa othcra moro donamrd during dar. lo both carra thc ropa bocnmo .... Jamenon Land, where il croons abeat 900 kmt (Fig. 1), und ...
SAND BANK AND DUNE FACIES ARCHITECTURE OF A WIDE INTRACRATONIC SEAWAY: LATE JURASSIC-EARLY CRETACEOUS RAUKELV FORMATION, JAMESON LAND, EAST GREENLAND FINNSURLYKA21DN4rNNANOE-NYGAARD
G logical liman Urriccroiry of Coprrahcrgar, Orrrc Voldguda 10 DK-1350 Kobrrrhcacr, K. Drroa.a,k
Aoaycoc'r Tha 200- ru 300-rn-thick Raukclo Formano,, war drpoairod irr an inoccraronic way b wnoc Eaor Grrcrrfand arrd Nono y duriog thr Lair Juraanic-caolicat Cocracooua (Volgian-Vafaogioian), prriod of coroidorablr arcronic unman io thn ,cgion. mr foomanion u
ia
thocr-diorcuaiooally nnpoaod nor, 900 kma. Four baaic rrchirocruoal
,ccogniaod 1. mo aandhank (SB) rlcmror in componrd of aioglc, arbolar mnga-croaa-bnda 15-
50 m thick, which cercod ooca thc whoir ourcrop arca (900 kma). 2. the auod-durrc (SD) rfcmrnn 000niana of a largr.acalc rabot ar croaa-hrddcd coach 2-8 m thick, which cnrcnda ovcr thc whoic ourcoop arca (900 gma). 3. thc aaodahoca (SS) olamenn comprima a burrowcd and gloncom'nired, mainly arough cooaa-brddcd coarn. 2-10m airick. with ahccr gcomcny, which corroda oecr moat or all of thr oucorop ama; and 4. tha ailumoor (SI) airmoon in 2-20m thick. ham ahccr goomeny, and corroda coro mr maar tOO kro°. mc SB, SD and SS clrmccu arc roppod by planar, glancueiaincd commooly pcbblc-aoown
omiaaioraaurfocraroith U-ohaprri burooma. Moar aaod bacrka of thr SB clrmrnn migrarrd roncward from dan wcarrm coaarlinc, whorcar thr liorar donan of tho SD rlrm001 migralod aouthwacd, parallcf to thr bario ania and ro thn ooaaa. Simnrlcliooaccma ro heno boon g000mnd mainly by coaar-pnrnllol or oflahora.diaccrod curocoro aca up by arorrrra and nidca. Thc low-arrrplirudn 3-D donna of tho SS olomool migrarnd roward thc aonda on. randy, rowmd
thc north.
Barca of acidcccc and acdanr
rocoidcrcd co oclarinoly coco0001 for thn Soo can rimr inrernnl ir qucarino. Thc aucccsaion mnaiarn cf arackod SB, SD, SS and 5f clemonla. A
cicar. ayarrmaric. arqunnlial arockiog mdc, baa nor boon obacrnrd, alrhough thor, io o rondrncy loa dcnnlnpmcnrofao SB, SS, SDcycir. A rural of four SB, th000 SD, Orneo SS and
neo Si cicmrnu han boon aanordcd. Dopoairinn ja inrcrprrrcd an coornollod mamly by Oucruaniona in angional oca leoni during a poriod of lowanond. Thr indinidual nlnmrnra mOnd fairly rapid rogional aaa-lrnrl flucanariona on a background of thc 000aall loornrand. Thc main rranapooa of aend in dar borin rook pleco in rnrenaioc hrlda of honor aand donna (SD clrmcnr). Sand hacha (SB nlcmcnr( worn iciajarnd nr rimca of high ram of una-Inno) miar, and thc main growth by eaarward progrndalion rook plano duriog highanacth. Snmr bank ropa wrrn cr0404 during aca.lrncl fall, whcroaa othcra moro donamrd during dar. lo both carra thc ropa bocnmo
glanconirirnd and bmrowrd during tho auccccding nino. mc omiaaion aurfacr mua alowly concord by biomnrbarrd ailraronr (SI nlnmmnr) during high ram nf ana-Iront nan. in corn of al owor raro of riararcworkrd. nanagooaaion abrer aand (SS olomror) mar fonnnd. Sra lcnrl cnrimnmuf to banc Oncauorrd bnrneoon 30 and 30m during drponirinn of tho SB cicmonla. Thrar oaciilaaiona had a duronion nf afanar t my. and reran auperimpeaod onalonnarund following dar Kirrnrncoidgiana higharand. mo lowarand had a ducarino of aboun IO my.
Suclyk aod Nee-Nygaard
INTRODUCI'ION
Acchirodlraral 3-D marnrsnigotmons of anoieai. sandy, ahatlow-maniaao dcpnair.0 arr low io
number, mr great latrmi rntroi mrd the commonly groat thickarns of auch uuccosai000 rr9uirr Iucgr-scalr 3-D cnpoauana daui roncal frafranru uf dar aaaur icair al those occurring in dir connclatino caaeireamrnt, nuproiatly whrn applyiog nrqa000e nloafigraphic cncccpiu thus wenn rlcvelopod mainly from seiamio arctiooa aorrss p050inc continental mang inn. Scatiog problema cuaaed by 3-D rrconsBsrclion of iangr-rcair doponitionai nyutcmn anude from 2-D cuponurms miar adda of cauniog a nomencf alare and ionerprrsatiooal moruno of dar noci that baa hamprced vabmarior-fan research fon moro sinon 50 your, (uro Normark and olhers. 1984), Io thin asady. we report on the 200-300-rn-thick aaaady, Shallow macina Rauknlv Fomwotion, drpositrd io dar Laie Juranuic-rarliros Crrsaceoas (Volgian-Vatauginiao) in a wido opeinic seaway between East Gcrecivad and Norway. Virsualiy eompfrrr mnpouucr io fouod in a 900,knot aera io 2am0000 Land, tant Ge000laand. with o basin-margin ouslier in Milne Lood 80kw want of dar maim outceop arca (Figa. 1.2), Individual brds and bed boundaries have been mapped Itaroaghosi dar arca. Biosiraligrophic c0000i iv rmanonobly good (Sonlyk, 1973; lluriyk and otbemn, 1973; Suniyk and Zukharov, 1982), aiding estimation of a gradadonai and progrodutional mirs us welt on hiatal simm opaca. A complcie 3-D ceconstractioo of the drpnnitiional nyotem bon benn ondrctairen, together mida an iotrrpcctarion of dar rrtalioe importance nf sire controlling factoro, notably neo-tonel changes, sabsidenor and sediment napply. Thc trudy prrorots drtaila of geometry, intcnrral nrrractsres and growth pasterns of hugn, sabalar sand backs and migrating doer brida. Our obscrvatinns from the Jurasnic succession nf East Gerrolued and from liserarure nindirn uuggrsnS that the mega-tandbonk cross-bedding is moo, cemmos atine anoirntrrcnrd thon iridaeete rccogsizrd, and wo hope that dar drnoniptioos offrerd brrr will pmmpt mncngnilien of comparubte fruturms in odarr anoirct voccemirno.
The Raukels Fornlutioe 000ars iu southernmost lamosos Land. Stia of Votgian ago (buotyk, 1973. 1975; Sorlyk und rdaers, 1973; barfyk and Zakbaeoo, 1982). 1g iv subdisidod into dar towre sandy Bjarliandsctu Member (Lomee-Maddle Votgras). a middle, uhuly balia Dal Mrmber (Middle Volgian), and an upper Fynarin Member (Middlr Upper Volgian) (Fig. 2). An imlasod radico occurs so Milor Land io the wrut (Fig. 1), and is described under a diffrrmnt art nf names oancsrd by Birkeland and ethers (i984((Fig. 2). Recent studien havr rendered this Sanai nomendiaiurr naprefluoua; dam
Kecbsedat and Pcmat'yggen Member, ace similar so dir Sjaettandsciv Member, the Astortodal Member is a lighdy coarser margisnul coreotastvr of she Satin Dal Member, and
In mid-Carhoniferous simm, dar nnikr-nlip regime changed roan rssensi000l one, and in Eros Oermeiand nfting continued ontii mid-Pnnnian time (Sonlyh and others. 1986). Latme basin mvolatinn in East Oeneniand man nirongty genraned by the Inoolioution und difference, in the nausee of the individrsol mid-Folcoroic banian. The neuthcmn rod of ihr onahom basin in tasarnos Laud is looaiirod 00m a deep midPatcnoeic basin with highiy attenuated crust (Larsen and others. 1989), and thr Lard Pcnnian iherugh Mrsoroic nubsideoor can mnrntiuliy be rnplained an having bree caused by daermai contraction following mid-Palr000ic srlovtcvsinn aod rifting (Saeiyk bd edades, 1986). North cf Jumoson Land, the Late Premiun-Menoroic evetation wan markedly differeos,
romging fmm asean whero Denonian-Canbenifcmun estonsionoi thinnieg wan much trot shad io Jammsoo Land so armas whenc basin formation was fmrnt initiused in Mcsoreic times. In Ute loiter areas. Mnanmnic rifting paises werd assaniused with dan fonnotion of daick nyn-rifs wedge, (lluriyk, 1978. 1909).
Miall (1985) in recograiring bart of basic 3-D architectateal elements defmed by scale, grain size, cnlcrnul geometry, internal aeqarncn, bedform composition, und nunuer of lower and upper beunding surfaces. The aechilooturat rlrmrotn form a vimpin hierarchical syntrm defined by theti relativo scale - dan micro-, meure und rnocr000rms of Jocknon (1975). Four aaohitoctneut clemenm urn recognized: Idar sandbank (SB) clamons, 2. the nund-
during several huadned million yruas of Men000ic time. This paper dowaibes the nuodhuoko and sand-dunn fields nf dar Fynsets Member (Fig. 2). This unit shows oslap mr the eastern boum margin, mrd major beunding hiornseu arr
km° outcrop aera milhous showing significant syssematic chongea is grain size, thickness or ethcr fralurms. The tower vet boundary muy be sharp, consistiog of dar
conceded along beth the western und rostem margins. The main outcrop is in noudaron Jamenon Land, where il croons abeat 900 kmt (Fig. 1), und whom the member is nbeal 100 er daick. Esposuen is virtually total, mida only u thin negetution cone, no a few
downward mb biotarbated silty or noody shale (Fig. 3). The upper boundary is either
shaly intervals daut cup major tundscapo-fonning saandsarse sheets.
from the degree of truncation of star npper. asymptotic part of tttr sigmoidal fnrrsrss. The upper oseface is gluaronisized and meter-long hairpin U-burrows, Dipiocn-uren-inm babichi.
MElfiOtE
compimn. Cruntut thickening during Catedonian mnuotuio-hrif formasino in dar Lair Sutueiao was followed by crgnsas cotlopse und estrosina duriog dar Denonian (rg., MoCluy und othmu, 1986; Slgorrt and other,, 1989). Drop Dmvociun iranios formed in dad tronnteoli000l portions of an overall fonda-south teanacarment notting. Some of dam basins almost reached a narrow mocan usage, with a highly ihinnmd continental cmst (Luesrn und odacnn, 1989), whereon ostension eus aorrstrd al eurlier osagen ig oshrc
This pupor forusrn on hierarchical elrmrnls, scales and 3-D gromrtry; details on ooglimenlaay procrssrn will be drucaibod ebewhcrc. The analysis follows Alba (1983) und
dar Henoigmyggen Mnmber corresponds se the Fynsels Member, but conceda a major Uppee Velgias-Ryazuniun hiatos regecsiug irs busia-muegin position. The Ruokets Foovution basan overall theol geomeloy. although tris thickest in the basin conter and thin loward the erstem and eastern moegiun. The strong crlief formed by edt-shoulder uplift indie areas nords of Jamenon Lund uodoubtedty neesed us proseraoce for the formation. It is itnponsant so stress that the Raukeln Formation was deposited io au idreacronnoic, esrensional basin. Thin sype of setting was highly characteristic doming the Me000inc, and compacable basins oocrstmed ott along the macgins of dar prrsret-duy Atlantic Dorais and mary ethnr places in dar world. Elongate, introcmsosic rift basing with rdlotisciy ohotmnw.anarinn coodilioos arr virtually unknown today. The Raukels selling rnoy dios have on modem ceuorerpaeto, but nonetheirm represents a sensing that occurred middy
ThcthsSIc AriD StRSDO,SPOCSEi'flSG
Thanughous dar Juraasica 600-imm-wide north-nuuth-oaimased araway rstrnded hrtwmoo (lrreotand and Norway. The underl4ng secienic hackgenand foe dar erigio of dir irania is
aRcIOTEccr1RSLflEMON1S
Euely mapping demonstrated dar pranence of an osrmnnise continuity of u number 0f
thick beds nr units io the Ruukeln Formotirn ie tIre study area (Surlyk. 1973, 1975; Sactyk und others, 1973). Recent finid work by dar authors darwed Ihot, in particular, the top norfaces nf thrum animo represent sigoificont hiulal or ornianion surfaces that peasros a combiord sel 0f features allowing them te be idmntifird edro io isolated
duno (SD) rlcmrnt. 3. the sundsiamrs (SS) rlcmcnt, and 4. the siltotone (SI) element. Figure 3 daoma u schematic diugrasn of the mnnrstigutrd vuocesnion based oc numerous locubitiou studied in detail und mopping of rlrments und emisnioa surfaces oser as much as 900 km°. Elerserrt SB: Sund benin
The largest clemens idrntificd in dar Fynselo Member consists of niogle cross-bedded nets ofcouenr-geaioed sandstone. The sets arr 15-50 m thick und tabular with sigmoidal or tangential berets (Figs. 4-10). The individual sels can be troced throughonl dar 900-
gluuconitioed und burrowed sarfacn of the uodeelyicg bed, or the foersem punn gradually sharp and erosional (tutsgensial formrts) or sharp bui non-esorainnol (sigmoidul forrnrts).
Erosion has nrsor removed more than, 01 nunimam, I er of the top of the bedan seen
penetrate downward from is (Figs. 5, 6). Gravel veneer, arr cemrnon, contaiving quurtzitic, flut, webb-sorted, molt-rounded pebbles thus range boteros 2 and 8 cm in musimum diameter. The fomsets huyo gende dips in dam upper and lower pacts of the individual sets, whereas dar middle puais sleep and mop reach angle of repose (Figs. 5, 7). A maximum dip of abeut 25° of the steepest part of dac forevet is the anrut unmmoo.
Toward thr top of the set, Ihe fomnels gradually mergr into a 2- te 5-m-lhick,
rsammned by thawing sel and istraodl beundunien, paleocuarent mrasuremcnlo and notoplo
herirootally-heddod topset. The foreseto maybe simpbo avalanche beds 10-30cm thick. showing inverse feuding, or alternations of coarner and finer beds. Simple avatunche boda dominoto in the more steeply dipping parts df thr forevets. Other foernrts ato cornpoand, composed 0030- lo 100-cm-thick trough ceom-brdded intrusels (Fig. 8). Intranets une characteristic of mord gently-dipping foresets und arc particularly common sa the upper part of the foersetu. Tmnuporled ussembluges of bioalvru, belemniten, asnmoniles. and occasionally criooidn. occur in the foreurts. lt in mmarkablr thus the assemblages change in species composition between succmnsivr foresets. The mcgu.focrsers ef moot bunks uhow a distinctly unimodal dip toward the east. aud dip direetions of indisidoal neto change only seny little along sinke. indicating a linear
locations on ocreiopping color polaroid photographs. This nimplo sochnique han a
freni of the bddform (Fig. 15). Thr forennl dip-direction of the intranets deviates
oemendoan potennial io memoir oleas where normal fdms cannot br readily developed and overlay techniques cursos be opplied (cf. Alien, 1983). The macgm-scale bedfomms und structures characteristic nf the Pynsotc Membre arr shows berran interpreted pholomnuaicu (Figs. 4-15). The uninterpreted mosaic in shown obene and the interpreted und annotaird sersion below. in mach figure. The intorpeenation of the phommosaicu in dar ofgcr was aided by polaroid phomgraphs of the ammo vretioe irleapeetrd und marked in the BrId.
systemulically ubeul 45° toward dan south of the mega-foersess. This shows daul thc umubb 3-D dusru, daut formed Ihr intrusets, migrated with an oblique ungIr down thr uuefacr nf the mrga-foresets. Thn SB clemens is clearly a macroform in the senor of Jackson (1975). The rlrmenl formed by cussward progmadation from dan coastal zone nf an eslensive tubular sand hauls with a linear noeth-south-orienled macgin. The moga-fomuess can adequately be described an cbinofornrv. although thin term mainly refers se succnsumve
nutcropn (Sunlyk and Nee-Nygaurd, 1989). In oorrtcass, Ihm mnncrscning bedn repernect
only two major architectural nlrments, dar nandbunk (SB) and she sand-dune (SD) elements, chararsra'irrd by mega- and large-scald cress-bedding, respectively, und daean featomcu alone ore insufficient to allow hod identification. The mega-croas-bods of thm SB
elrmrsl hase set thiokarsu in evoess of 15m in contrast te the sol daicknew of the SD element, which is below 4 m; inlennediusm femss hanm not bers recognized. Tracing mf omission saciados was done by mappiog en fool, by helicopter and by intempemsation of vertical urriul photographs (scalr 1:50.000). The geometry of mrga-crosn-brds wan
Sand bank and dirse facies uechilcclurc
261
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24°
71°'
230
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MILNE LOUD
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Jameson Land
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