bY, M arlin B rasier, John C ow ie and M ichael Tavlor D ecisio n o n th e P reca m b rian - C a m b ria n boundary stratotype

The G lobal Stratotype Se(,tion and Pointjbr the P ro- dom inate elsew here. It w its for this reas(川that B D aily (unpub- terozoiC- C anibrian botindarv has been agreed upon. lished) em phasised the potential of' [race stratigraphy as a subsidiary gVuide. The botindarY is defi ned in a coastal section near the T his w a s l 'o llow cd in 1974 by a m eeting in Paris. at w hich the loviln Of' Fortune in sotitheaste,二 N etyfl)undland, follow ing Points W ere 1.111aniniously agreed (C ow ie, 1992). C a n ad a . T he prim ary task of the W orking G ro up w as the choice o f a stra- Lotype boundary point-, a secondary task w as the consideration ot associated stratigraphic divisions above and below the bound- a ry . In tro d u c tio n A ny s uccession selected for the boundary point m ust be as con- fi nUOUS as possible, m arine. and as m ono facial as possib le} the m ain m ethod of guidance in selection should be biostratig- T he problem of the - boundary is part of one raphy although all possible m ethods of correlation should be ol'ihe Lreatcst enigm as of the fossil record; i.e. the relatively abrupt e nliste d . appearance of skeletal and com plex, deep burrow s in sedi- T he 'Edia c a r a' type fauna should be considered as Precam brian- inerriary Successions around the w orld. A s w ill be recounted below , T he 'oleiiellid/t'allotaspid' faunas should be considered its definition has involved the rolling back of a m ajor frontier in as C am b rian - o ver the last three decades. B etw ee n the 'E d iacara' and the trilob ite faun as, tho se fossi川七r- U ntil the la te 194 0 s. it w a s ass u m e d th at the P recam b rian w as ous successions that Could not be allocated w ith certainty to largely w ithout fossils and that the base of the C am brian w as m arked eith er the Prec am brian o r the C am bria n, sh ou ld hav e the W ork - by the low est appearance of , e.g. the 'O lenellus Z one' of' ing G roup’S Close attention. W alcott (1890) and W heeler 门947). M ore traditionally, it w as Increased SUpport for w or k o n the boundary w as m ade possi- draw n a[ a reuional Unconform ity below them , c-g. in R ayner(1967). ble in 1974, w hen 'T he Precam brian-C arnbrian B oundary' w as T he first steps tow ards a m ore precise definition of the base w ere accepted its Project 29 by the IG C 13 B oard. A m eeting in C am - taken in 1960. at the N orden IG C in C openhagen. w hen M F G laess- brid ae. U K , in 1978. review ed discoveries Of SUb-trilobitic sm all net- proposed the establishm ent of a Subcom m ission on C am brian ske le ta l fo ssi卜 an d [race fossils fro m aro u nd the w orld , a s w e ll as StratioCraphy, and in 1968 w hen C hairm an C I Stubblefield and Sec- the potential :)「unacCynetostratigraphy. T he C am bridge m eeting retary J W C ow ie chose the problem of' the 'B ase of the C am brian reco m m ended to the W orking G roup that "T he Precam brian- ' its one of its first tasks. B y this tim e, the existence o l'a latest C am brian boundary should be placed as close as is practicable to Precam brian fauna w as w idely acknow ledged, e.g- in G laessner and the base Of the oldest stratigraphic unit to yield T ornino tian W ade (1966), and w ork by R ussian gL,eologists w as beginning to (sensu lato) fossil assem blages" (C ow ie, 1978). A lthough there dem onstrate a pre-trilobitic succession of skeletal faunas, w hich w as little support at this tim e for it boundary defined by trace fos- w ere referred to the C am brian System . e.v. in Rozanov (1967). siJs. their potential for the correlation ot strata below the first M eetings on the boundary w ere organized for the IG C in C zechoslo- trilobites w its now being explored (see A lpert, 1977; B rasier, vakia in 1968, and at M ontreal in 1972. M uch discussion ensued at 1979, figure I). the latter niceling and it 'W orkin.- G roup on the Precarribrian-C am - C and id ate s f o r the P recanibrian- C anib rian G S S P w ere d is- brian B oundary' (PC -C B W G ) w as form ed, w ith J W C ow ie as its cussed in som e detail at a m ectingC. in Bristol, England in 1983. and C hairm an. Som e of the history of the W orking G roup has been sum - th ree w e re se lecte d fo r (u rther co n sid eratio n, a s fo llow s. m arized elsew here (C ow ie, 1992). U lakfian-SLII.UgLir on the A ldan R iver in castern Sib er i a , ot the In effect, this W orkingC G roup w a s setting itself the challeng- form er U SSR (now in R ussia)-, here the boundary level (at the ina task ofdefi ning the 'bottom line' ofthe biostratig raphic scale; base of bed 8 ) lay in carbonate facies, w ithin a succession of i.e. [()discover, naine and interpret fossils w here few had been sm all skeletal fossils and algae that lay below the earliest found before. M any of the fossils unearthed o ver the follow ing archaeocyathans, and other m arkets ot bTom m otian decades w ere not referable to previously know n groups and their type': this section w as w ell know n and w ell studied. potential for stratigraphic correlation w as, therefore, com pletely T he section at M eishucun near K unm ing, in Y unna n Province u ntested . o f southern C hina. H ere, the boundary level (M arker B ) lay T he W o rkingV G r oup held its first field m eetingV in S iberia in w ithin a phosphorite facies and w as m arked by the abrupt 1973, sponsored by the A caderny of Sciences of the U SS R , to con- appearances of phosphatised in icrom olkiscs and problem atica. sider possible stratotypes For the Precam brian-C am brian bound- T h is sectio n w a s w e ll-stu d ied b ut little kn o w n o utsid e o f ary along the m iddle reaches of the A ldan and L ena rivers in C hina. Y akuLia, eastern . H ere, 29 ForeigMn gCeologists w ere intro- S ev eral s e ctio ns o n th e B urin P en in su la of so u th eastern N ew - duced to the 'T om m oiian I'auna' and the sections of R ozanov and foundland, C anada; here both sm all skeletal fossils and trace fos- others (1969)一M em bers discussed, not for the last tim e, the origin sils w ere kn ow n to occ ur in it rn ix ed carb on ale-silic iclastic suc- of' the low est sm all shelly fossil (S SF ) asscrnblagle in bed 8 at cession. O nly outline studies w ere available from this region and U lakhan Sulugur, that w as referred to the base Ot the T om m otian no precise section w as pinpointed. (C ow ie and R ozanov, 1974 ). D iscussions also focused on A t this m eeting, it w as again dec id e d that the boundary strato- the relationship betw een lithofacies and biofacies, notably the type should be placed "as close as practicable to the low est know n problem of correlatinCg carbonate shelf facies w ith archaeocy- appearance of diverse shelly fossils with a good potential for corre- athans (as in Siberia) w ith clastic shelf to basinal facies that pre- lation" (C ow ie, 1985). Such an em phasis upon SS17s provided a great

, 广 _1 1 1 气, 污 卜 , I , 了

Sti1 111.11L IS [。、their study. but there w as grow ing concern about their how ever- that [lie w hole section w as rem agnetised in O rdovician utility forcon-clation. A prelim inary m andate Forille M eishUCUII SCC- tim es. A W orking G roup visit to the B urin Peninsula in 1979 w as tion w as del'erred at the M oscow IG C in 1984, w hen it w as recog- l'ollow ed up by im portant ,round w ork on SSFs. trace lossils and nised that greater international aIgreem ent oil SSF taxonom y w as Ii [ hostr at igraphy (B engison and Fletcher, 198 1.1983). Further necessary- 'I’h is led to -,in "SSF W orkshop" in U ppsala in 1986, orga- researches Culm inated in a ol'papers w hich detailed the strati- nized bv S Benatson. It call now be seen that this m ecting resulted in gIOraPphic dli、S1h1·-ibLUlti(o川n (o)f trace l O SSjlS, SS[7s and lithostrati-raphy several new thrusts. First, it becalm apparent that the boundary SLIC- (C rim es and A nderson, 1985: N arbonne and others. 1997: N ar- ce ssio ns in C hin a h ad it d istinct c haracter, w hich Co u ld b e trace d into bonne and M yrow , 1998: L anding, 1988; Landing and others, India. Pakistan and Iran (Brasier, 1999a) but correlation beyond 19 89 ). these form er terranes of' G ondw ana w as m ore probleniatical. Scc- A n u n derm anding em erged that SSF s, w hich had hitherto pro- ond, it cricoura-ed the view that sm all skeletal lossils w ere ]oil,,- vided the focus of一 W orking G roup discussions, W ere very greatly ranging, highly variable, over-split taxonom ically, taphonotnically affected bV provincialism and a Virtual restriction to shallow - poorly understood. often restricted by Iacies and provincial in distri- ate facies. T his suggested. to som e, that clefinition of the boundary bution (Landing and others. 1989} Q ian iind B ell"Ison, 1989 ). m iaht be better (TUided by [race fossils as w ell its body fossils. The A item pts W ere M ade to draw [lie data oil paridem ic lornis togt-ether, advanlaacs of trace fossils w ere stressed to he as follow s (c.(, COM Parill", the first appCitrallU S 01一 SLICCCSSIVC. taXa Oil it 10lobal Scale C rim es. 1987} N arbonne and others. 1997. N arbonne and M yrow (c.-. B rasier, 1989b) but the results W CI-C not Cillil-CIV CUIC01-11-alling 19 88 ). I'm high-resolution stratigraphy. T he problem s of' SS I}s w ere begin- 'I’h e y a r e especially com m on in siliciclastic I'lacies. in w hich SS I's ning. to com e into locus. arc typically rare and poorly preserved- T his is im portant since K now ledLg,e about th e C hinese sections im proved after visits by these deposits com prise nearly 70 per cent of' exposed rocks in G roup m em bers in [lie late 1970s -.in([ carly 1980s, and m ost espe- the boundary interval. cially aft er publications in English (IAIO and others. 1984, X ing and C am brian trace lossils a p p ear to have been less restricted in iernis others, 199 1)and the international m eetinu oil ifie T erininal Precam - ofhabilat range than in later intervals. brian and C am brian System s at Y ichangt} in 1987. T he problem s of' Several Successive zones fr o m around the w orld m ay correlatingZ.- the three SUb-trilobitic niarkers a( M eishUCLII) (term ed A , be reco(m ized in strata below the low est trilobites. B and C ) w ere review ed in En,ghsh hy B rasier (1989a). Scientists I'liese zones include ichnogenera w ith it lim ited S t r aLiIgraphic O utside C hina sho w ed co n siderab le con cern abo u t fi ve I'acto rs relat- ran-e and it broad stratigraphic distribUtiO11. O fthese. the P h )- in,) to the G SSP candidate at M eishLIC1111- codes p ethim Z one assem blalye contains typical C am brian ich- T he com parative ol'ilie Z one 11 a s sem bla-c above M arker notaxa in -it hi,yh-divcrsity assem blage w ith branched m or- B , chosen by (lie C hinese as [lie Candidate boundary [)Oilll} phologies, com plex feeding burrow s. escape traces and this question arose because it w as thought .‘)contain lossils dw ellint., burrow s. ']'he Underlying H ai-kiniella potiolica Z one found above the T ornillotian in Siberia (B engr.,ison and others, assem blatle is of low er diversity and com prises sim ple. hori- 19 9 4 )} zontal. sedirrient-Iceder traces, c.a. N enm iles, I'alueopascich- T he pre s ence ol'a possible gap _jUsI below M arket- B , show n by 11 1is . an abrupt changzl}e in lithol"acies (c.gI. B rasici,198911: Landin1g. T he r a il oes o f H arlaniella pm lofica and Ph)-coeles p edum arc 19 94 ). believed not to overlap} one succeeds [he other. providing. it The la c k ‘)门111.111al C0110 111.1itV betw een [lie three m arkers, also rare exam ple oi 加Urial replacem ent w ithin it boundary succes- su-}L,-estive of' breaks in [he sequence (Q ian at记 Bengtson. s io n . 19 99 ). A t F o r tu ne H ead . B u rin P en in su la , these tw o Iraces are seen T he int e rpretation ol'carbon isotopic projiles reported by Brasier w ithin it strati-raphic succession that show s little evidence ol' and others (1990 ). For exam ple. K ii-schvink and others (199 1) environm ental change. C orrelations of the boundary level are sm - ested that Z one If iiii-lit correlate w ith the basal A idabanian also possible betw een Fortune H ead and other localities on the C X C LII-Sio n s in S ib e ria . B urin Peninsula. Sim ilar faunal changes W ere Purported to take ’I ’h e interprelation of' R b/Si- clay m ineral isochrons W ,g. 596.91 place at other localities around the w orld . 4.6 M a, X ing and others, 199 1):recent data 1'rom LJ-Pb isochrons T hese ideas w ere discussed !It a rnecti q g a t S t John ’s . N ew - I'rorn ash hands near M arket- 13 indicate it m uch younoer age of f0tindland in A ugust 1997. and follow ed by f’ield excursions 5251 7 M a (C onipslon and others, 1992). throuoh the 'T erm inal ' and low er C am brian (N ar- Fu rth er d ocu m entatio n also be cam e av a il a b le o n the S ib erian bonne, 19K ). By this tim e. the W orkingC (!]-Out) w as under sorne sections (Sokolov an(] Z huravleva, 1% 3} R ozanov and Sokolov, pressure to reach a decision, because it had exam ined the problem 1984 ) and som e m em bers ol'the W orking G roup w ere able to exam - since 1972. It w as also clear that w hilst it m i'll-it he possible to ine the G SSP at U lakhan-SUIL1,21I.Ir dUrinO 山e Second International reach a decision on the boundary point, its global correlation w its SVII1pOSiUIII Oil the C am brian Systern in 1990 (A stashkin and others. goin g to be open to w ide dispute. N on-biostratigraphic m ethods 1990). Its potential 1"or carbon isotope- and m agnelostratigraphy of con-claiion. Such its carbon一,strontium 一,even1 -st ralj ar aphy appeared good W .g. K irschvink and others. 199 1).D iscussion, how - ,a nd oVe o c hronoloCgy- W ould be needed to im prove stratiLo-raphic res- ever, centred on the origin ol'hcd 8: W as it 11 StratIfiCLI layer. or w as it olution at this level. A proposal w as put forw ard. therefore, by M piped dow n along karstic liSSLII-CS fi-0111 about ;I inetre above" Support [)B rasier and K J H su to the IG C P B oard in 1989. to e11COL1ra(1c l"or the fatter view w as oiven bv lield data (K honicniovsky and oth- 5S:LIcCl1l1 lr℃esce:a11r·che、s thlr,:o川ugah a proJect on 'Pi-ec:iiilbi-iiiii-('ain bi-jaii ers, 1990 ) but isotopic data has proved m ore equivocal (B rasier and E vent Stratigraphy'. Project 30 3 w as accepted and its first in ect- others, 1993 )一A view is em erging ol' it w idespread unconf'orniiLy in-(-, took place in Siheria in July-A u IM SI 1990. T he findings of near the base o f' the T o niniotia n acro ss in uc h o f' the S iberian P lat- this proJect have an im portant hearing on correlation of the P ro- l'orni. represcm ing -.I hia[LIS 01' 1111CCIlain duration (C.g. L anding carribrian-C arnbrian boundary. w hich w ill be diSCLIssed else- 19 94 ). w he re. U n ti l 1981 the potential Ol'SOL11heasiern N eW lOfl idland Im it T h e c h o sen G S S P cand idate at I-o rtu ne H cad . B u rin Pe ninsu la. inixed. carbonale/SSF -siI icicl astic/1 race, I"ossi I stratigraphy w as lit- N ew foundland w its first put forw ard by C anadian and U S m em bers lie tested. H utchinson (1962) and G reene and W illiam s (1974) had ofthc W orking G roup in 1987. T he results of a straw poll held in St reported SS F assernblaves below [he earliest Irilobiles. T P Fletcher John 's W that tim e seerned favourable (C ow ie and B rasier, 1989 ). (1978) had presented an Outline Stratigraphy (们lie B urin Peninsula W ritten proposals w ere then reCILICsted by C hairm an J W C ow ie at C am bridge. T his w ork w as l'ollow ed tip by Furthcr fith()一and bio- Fro m eac h o f the three G S S P can d idates. to ou tline the ir utilitv for stratigraphy CF P Fletcher, 1.111111-il-ifished), accom panied by inaaneto- correlation by biostratigraphic and non-biosiratioraphic (e.,, straligraphy 0 K irschvink, unpublished)- T he littler discovered. 1,1.eocliroiiolo.L,ic. palaeornagnetic and stable isotopic) techniques,

M a rch & J im e /9 V4 for accessibility. and potential for conserv a ti o n. T hese w ere subm it- In this rcgCion, C am brian deposition (Figure 2) w as accornnio- ted in O ctober 1990 as follow s: A Y u R ozanov (U lakhan-SulufL_f ): dated by local, long-term extension of the basem ent, com prising X ino Y , L uo. H , Jiang, Z and Z hang, S (M eiShUcun): and E Landing Late Precam brian volcanics and clastics affected by the -A valonian and G N N arbonne (Fortune H ead, N ew foundland). A postal ballot O rogen'- T he Fortune B ay B asin began w ith the deposition ol ot the 23 V otina M em bers w as arranged by J W C ow ie in the Spring 2750 tit ol'upw ardly fininLg_ r ed beds that gL_rade into perilidal sand- of 199 1.T his ballot received a 100 per cent response, YivinC- an stones tit the top (Beng(son an(] I 1cicher. 19H3. Landing and others, overall m ajority ol'52 per cent to the B Urin candidate. 35 per cent to 1988 ). T hese w ere succeeded by ca- 1000 tit of' siliciclastic shelf' C hina and 13 per cent to Siberia. Follow ing the guidclines o1A C S . a l'acies, placed in the C hapel Island I-orm ation, and deposited dur- second postal ballot w as held on the B urin .,}Lction alone, in the SUrn- in ,L_y ::m ajo,二、ca level' cycle its follow s: peritidal sandstone and nier of' 199 1, w hich led to a 6 1 per cent m ajority for the section at shales (M em ber I):S1.01-111-infILIC11CCd M uddy deltaic and shelf Fortune H ead . T his m ajority w its large enough to allow ratification sandstones and IIIUdstoncs (M em ber 2A )} thinly larninated silt- by the IC S and the IU G S (at the IG C in K yoto. A ugust 1992), w hen stones of the distal shelf', deposited below w ave base (M em ber 213 C hairm anship of' the C am brian Subcom m ission passed to M D tind M em ber 3): UnUdstoncs w ith thin lim estones. deposited under Brasier. R esponsibility for the basal boundary of the C am brian also low energy, inner shelf' to pen tidal con山tions (M em ber 4): and passed from the W orkinCg G roup to the C am brian Subcom m ission at san d sto nes and siltsto ne s o f all o ffsho re to sho rel'ace sto rn i-d o m i- th is tim e . nated shelf(M yrow and H iscolt, 1994 ). T hese w ere then capped by th e m acro lid al san d sto nes all(] sillsto ne s o f the R an d om Fo rm ation , w hich call be traced across the A valonjan region (H utchinson, T h e F o r tu n e H ea d G S S P 1962, L anding, 1992)- M em ber I ol一 th e C hapel Island Form ation (ca. 180 111) T he Fortune [lead GSSP section IS Situated near the tip of the Burin includes upperm ost Precam brian se山m ents. It yields biostrati- Peninsula. Southeastern N ew foundland (figure I),in low cliff's that gL,raphically im portant trace lossils (们he H artaniella podolica ich- extended beyond 'Fortune D um p’. E asy access is possible frorn the nol'ossil B iozone (B enatson and Fletcher, 1993二(.rinies and tow n of' Fortune; there are no political or geographical problem s ol A nderson, 1985)一Ilarlaniella p odolica and P alaeopascichim s del- access. T he stralotype w as Pictured in E-pisodes of’ D ecem ber 1987 icam s ranCa.e into M em ber 2, w licre 山ey are last seen 0.2 ill below (N arbonne, 1987, figure I). th e G S S I1. O rLa nic -w a lled tub es o f" Su b efi eh les ca m bfi en sts l'il-SL C oastal cliff'cxposures a t F ortune H ead display som e 440 m of' appear near the top ol'M ernber I and range at least its high as M cm - the C hapel Island Form ation. w ith beds dipping a[ 15 to 46 degrees her 4 . T he Su be fi d iles ca nd w ien sts skeletal lo ssil B io zo ne is to the w est (steeper dips are tow ard the top (们lie section). Several defined betw een the First occurrence o l' this taxon, and the hi-her SnIall faUlls are present w ell above the stratotype level, but m arket- first appearance of calcareous lube ’L adatheca ’c.1-filldrica ill horizons allow easy correlation across them (Landing and others. M e m be r 2 B . 198K p.35). Breaks in deposition are m inor and restricted to the T he Pre c a m brian -C am brian boundary point (Figure .1) lies bases ol'thin. w ave-deposited sand units. 2.4 in above the base o l'M em ber 2 in the C hapel Island Form ation.

FA C IE S A S S O C T IO N S {二]黯 貂egsreen sandstones 场 }}Y 了 卜 口 Gsarenyd sttoo nbela cakn din steiltrsbteodndee/dshale 丫内 配/ 4L 叮 Illy/ - 0 ;,7 ,犯 - 口 氦愁器饥esrabneddsstone and I I 学 , B O N A V IS T A ,, 夕 N IN S U L A }石刃 R}cl.and green 个 / L 一一-i s m s to n e 勺 份,书‘厂少日 勺尸 .一 ,~~~~曰 丫 了 5 0 k m : 、 军分 M E M B E R I 妙 、 甲 不/ / 2 7:4L. 2 飞 ’ , j M E M B E R 2 勺 {{ , / 毋、 沪 4 向 冲 \ ,、 . 哪 叮, 声 J o h n 's

八甘A L O N 乙3 峭.卜 P E N IN S U L A . 一一」 厂 沪 lo o m N 了 甘 篡 q 、 FO RT U N E H EA D G S SP SEC T IO N , 多 S O U T H E A S T E R N N E W FO U N D LA N D S O U T H E A S T E R N N E W F O U N D L A N D

F igure I G eneralized locality m ap of N ewfoundland (inset) show ing location of t he F ortune H ead stratotype and detail m ap of t he 440 m -th ick section at F ortune H ead. D iagonal ruling indicales.wrike direction. FA =facies associations. Based on landing and others (1988,fi gures 4and 19).

均fi sod eN, V ol. 17 , no s- I & 2 6

In te rpretatio n M e m b e r A Palaeobathym etry 墓 丁 1 内 1 0 0 0 卜 UJ 厂 隔 S 二 卜 < | 5 H 几 子 石 1 厂 叹十 q 0 0 魏 才夕 万 标袭 j 一 L。’二1 一 了气广沙 扮争e" 0' }N' 一L 入 L 8 0 0 4 中 山 S 产 V 工 lwe 几 | 1 7 0 0 3 一 一 6 0 0 。嚣 吕 一。 5 0 0 翔 1 5 。 卜 下 一 4 0 0 、2 二 架 户 山 二 S 全 V H 尸 3 0 0 d 一 S B I 沐 一 I- /1 C A M B R IA N 耸 2 0 0 玉 泛 一 / - *一 F S P R E C A M 13 R IA N J、 咚 es川 es 1 0 0 一 口 9 叹 巨 1 厂 一 厂 越 门 霎墓,二}}fli 1111 } 一Mn.j}dfi Col-,t, U ^ 亡 0 一 一 U 1 十S S 山 ① 。 S 的 S 山 ﹂ 庄 5一 一 匕 巴 巴 山 U一 一 IS W 日 分 鼠一STah,.d/W1 ,h," ,'I-,.at T Shd-,} SdO b,N}td.Id ---d - Sd W- SdGh,a,I Sl}tcO,, G -as1l1, G},- C. Fig ure 2 6 eneralized stratig raphic section .f in- th e C hapel / Island F orm ation, show ing inl}rred paltohathlynietry, three- F igure 3 Faunal succession and lithology throngh th e p hase depositional InstorY, and sequence-stratigraphic Precanibrian-C anibrian boundary stratot yp e se ction at F orlune interpretation. The Precanibrian-Canibrian boundary stralotype H ead. Based on N arbonne and others; (1987,fi gure 5) and point is show n. F S = flooding su}14ce; AIF S =inax tinuin fl ooding landing and others (1988,fi gure 20). F orfi )ssil distribution and surj}ce. SB =sequence boundary. TST =transgressive sYstenis lithological datafiroin the overlying 420 in oj'continuousl-v tract. H S T =highstand system s tract. S W B =slorin wave base. Sh exp osed strato at F ortun e H ead, see N arbonne and others} (1987, =shalel- Sltst=silistone; S's =sandstone; LS =litnestone. The figure 4), L anding and others (1988, figures 21-23); A}Yrow and scale is in inetresft oin the beginning of1he exposure. B ased on fliscott (1993,万gure 8少. M YrO W and H iscott (1993,欣 tire 3)

i.e. just above the transition to ston-n-inflUenced facies and 18.2 in abo ve the base of the Successio n at F ortu ne H ead . T h is G S S P is it N on一biostratigraphic m eans of point in rock that defines it m om ent in tim e and w as selected w ith co r rela tio n Ouidance from the level m arked by the low est Occurrence of Plj_%?- codes pe( (a trace flossil), at the base of the C am brian PhYcodes peduin B iozone (F igure 2; see N arbonne and others, 1987, ligure T he hmil](Lfy IC\rel lack, carbowltCS 141itable for carhon or stron- 8B ,.T he in arker fossil is preserved as it series ol'branched, hypich- tiLIIII isotope analysis. StUdICS 011 IIOCILIICS and bedded lim estones nial ridges on the low er surface ofa sandstone- Its appearance at this hi,her in the Burm sLICCCSSiOII sho)v, the CITects of, w idespread thel level is not directly traceable to a change in facies, w hich takes place m al alteration clLfillg deep hL11-ial and 21-allitiC iIItI-LISiOII(B rasier and low er in [he sequence (M em ber I to M em ber 2A boundary). In addi- others. 1992). Sim ilar problem s have afected suitability of' the s(I-a- tion. both perilidal and subtidal facies in M em ber I contain H ar- to)tYPC i()'- Palaco m aIgn e t ic coirclation (see above). R cI,rcttahly, this laniella podolica, and facies identical to those in M em ber I are m c a n s th a t th e A siatic s c c tio n s o f S ib e iia a n d 〔h in a c a n n o t b e c o r inlerbedded w ithin M em ber 2A , but do not show Lipper Precam brian related w ith the ncw G SSP by m cans of carbon isotope- and m aIg- trace fossils. T hese features SLJ}IgCSt that environm ental factors, netostratigraphy, althOLILIh they pro\idc a valLiahle tool for con-cla- tio n CISCw herc (K ii-sch %ink and othe rs. 199 1二B IaI,iCI a nd o thers w hile sionificant, w ere only of second- order influence upon the dis- tribution oftrace fossils thougC.h this section. T he boundary point also !9 94 ). d e fine s the b ase ()!一the L ow er C am b rian 'P la centia n S erie s ' o l"L and - ing and others (1989). T h e first occu rre n c e o f calc are ou s sh elled skeleta l fo ssils G eoch ronology of the boundary (E adatheca ' c0 indrica) here lies som e 400 in above the Precam - brian-C arribrian boundary. A s m entioned above. their appearance is R ecent U一Pb radiom etric (Ictcrininations on VOlCaIIiC Zil-COlls aFC related to facies and laphonoinic conditions and is unlikely to m ark a\ 7川ab le 1'rom N e,,k B I-LIIIS\ViCk- in strala possibly con-clated w ith the the true origin ol'biornineralization. T rilobites appear som e 1400 in LIPPCI- part of M em ber 5 (Bow rin- and othcrs, 1993). T hese vicid a above the boundary point, and m ark the start ofthe Low er C am brian date of' 530.7+0.7 M a (Isachsen and others, 1994): previously 'B ranchian Series'(们 andinla 〔1992 ). reported its 53 ]士I M a bv B ow i一川9 and others (1993) and Land in9

M (irc h & .1im e 19 9 4 7

(1994) and provides a in axiln Uin a,t,}e fo r the base ol' the overlyinCg Cow ic-I W . 197M. It l(;S/](;('13 Project 29 I3rcCiLiiibi-iaii-('LLiiibi-iiLn Boundary lonnation. T he boundary point lies som e 800 ni below its W orking G roup In C am briLILC. 1979: Geological M agazine, v. 115. pp. possible correlative, the R andom Form ation. in the B1.11-in Peninsula. 15 1一15 2 . A further (,uide to the radiorneiric aae of" the Precam brian- Cow ic, J W . 1985, ('0111ifi lin" x%ork On the PI-CC.1111hrian一('am brian hOLInd- ary: Upisodes, v. S. pp. 93 -97. C am brian boundary com es From recent U -Pb dates I、一()m Siberia C OW iC, J W . 1991 T W O decades Of l-C-search o n the Pro terozoic-P hancrozoic (B ow rino and others, 1993). In the O lenck re,,ion. volcanic hreccias transition: 1972- 199 1, Occur w ithin the N einakit-D aldynian StaCge, above the first sm all C ow ie, J W . and R ozanoN.A Y u. 1974 , lU G S Precarnbrian-k arnbrian B ou nd- shelly fossil (Canibrolubulti.v sp.) but below the first skeletal assem - ary W orking G rOLIp [it Siheria: UICOIOLiCal M a"aZine.、。.Ill.pp.237-25-1. blage w ith A ntibartles Irlsilicants. These breccias have recently been C rim es, T 11, 1997. ']"race Fo ssils and co rrelation of L ate Precanihrian and dated at 543.610.1-4 M a (B ow ring and others, 1993). w hich gives an I} M-IV Call"Ibrian Strala: G CO]OUiCal M al-laZille.、,.124,pp.97-119. estim ated a-e tor the base (们 he N em akit -D aldynian ol' about 544 C rim es. T P. all([ A nderson, M M , 1995, '1’r ace Fossils I"ro m Late Precam - M a. T h is lev el ha s b een corre lated w ith the base o l'the C am brian in hrian-carly Cam brian straia 01' SOLIthcaslern N ew l'oundland (C anada): tem poral and environnicnial im pli cat ions: Journal ol'Palconlology,、一59. N ew foundland (N arbonne and others, 1997 ), oil the 1,0 1low ill" 3 1()一3 4 3 . ','rounds: Occurrence of P hYcodes sp. at all Unspecified level w ithin Fletcher, T 11. 1979. in U nited K ill,([()川〔'01111-ibUtion lo [he International the N cinakit D aldynian (Fedonkin, 1987} actually this taxon m ay G eological Cort-chilion Progran'1111C. 1976-79 Report: 'I lie Royal Socicly. 110L appeal- unti I the m iddle ol'the stage: M A Fedonkin, pers. com in.. London. pp. 26-27. 1993)} occurrence ol' Sabelli(lites canibriensis. w hich ranaL,es 1roni G lae ssner, M F} and W adc. M , 1 966.T he late P i℃一('am brian lo ssils 1'ro m E d i- the base of the stagCe (Sokolov and Fedonkin, 1985). A provisional acara, South A usiralia: Palaconlology, v.(). pli. 599-628. estim ate lor the aue of’ the Precam brian C am brian boundary is. G reene, B . and W illiam s, I L 1974. N cw IONSil 10C1111LICS and the base ol'thc there f'ore- cit. 5 44 M a . C am b rian in so u tlica sie rn N e %k FO LAIW ILHILL C a na d ia n J o u rna l o f' E a rth S c i- crices, v. 11, pp. 3 19- 323. IIULchinson, R D} 1962, CaInhFiall SLI-atiIoraphy and trilobile fitunas ol"south- eastern New FOUndland: 111111CH11 01' Lhe G e ological Survey ol'. Mg. A ckn ow ledgem ents 156 p- Khom entovsky, V V . and K arlova, G A } 1993. Biosiratigraphy ‘们 he Ven- T he I'ollowing are thanked ior comments and C0111-i buti ons:。、this diall-C ambrian beds aild IOWCj- C am brian boundary in Siberia: G cologi- report: T P C rim es, T P F letcher, E Landing. and A R Palm er. Cal m agazine.、,.130} pp. 29-45. Kirschvink..L .M agariiz. M 二Ripperdan. R I,ZhUravlev, A Y u. and Rozanov, A Yu, 199 1, The 1'recaillbl-i!Lll/('illlibFiilii boundary: m agrelosiraligraphy 1111d Carbon isotopes resolve co)rl-ClatiOll problem s bLiween Siberia R e fe r e n c e s M orocco and South Chilla: G SA Today. v- 1, lip. 69-7 1, 97. 9 1 I-arlding, E. 1988, Low cr C am brian ol'castern M assachusetts: stratigraphy 八[pert. S 1'. 1977.Trace Fossils and [lie basal C an-lbrian boundary, in C rillics, :11记S1111111 Shelly I'OSNi]N: .10111-11al(们lillacontology.\.62,pp.661--695. 'T P. and H arper. J C eds- Trace Fossils 2: Geological JOLU-nal SPCCi!ll Landirl,', 1-1. 1992. Low er Cam brian ol' Noutheasiel-ii N ew l'oundland: Issue. 1). Seel H OLISC Press, IJVCrPOo1. 1)1). 1 -M. epcirogcny and Lazaru} Famias. Iiiholacies-biol'acies linkaoc}, and the A slash kin. V A iind seven others. 1990 , G uideboo k [01- CXCUrsion ‘川 Il ie myth ola 'flobal chronostratigrapliv, in Lipps, J H} and Signo)r, P W , eds A ldan and Lena R ivers. Sihel'i!Lll Plall'orin. Novosibirsk. 115 pp. O ri-in and Farly EVOIL11ion ()I-ilic M cla/oa: N ew Y ork, Plenum Press. pp . Bengison. }, and Flelche门 ’P. 198 1, The SLICCCSSiOn Ol'SkCIC1,L] Fossils in the 2 8 3- 3 0 9 . basal I.0%VC1- CILinbrian ol' southeastern N ew l'oundland, in Taylor. M F, Landing., F". 1994. Pi-ec;iiiibi-iiiii-('iiiiihi-iLkii hoUlldal-V global SLI'atotype rati- ed.. Short Palicrs Jbr the Secon(曰nlernalional Sym posium on the Cam - tied alld it 11CIA pCrSpCC`1iVC OJ'Cifl ihrian lim e: G eology, v. 22, 179-1142. brian Syslein: U1111CLI States G eological SLll`VCV O pen-File Report, Landill_ 1". M V1-0\A.P M . BC11LIS. A 1), alld N arbonne, G W 1989. The Pill- h 1- 743. 1 X pli. CClltiW1 Scries: appearance ol'lhe OILICSI A clelalizcd ]'aunas in SoUllicast- Bengtson, S, and Fletcher. T 11, 19M3, 'Tile oldest SCCl1lCllCe Ol'Sk-elClid FOSNill ern NeW l'OllIlLillill(l:,10111-11;11 01’ I'llI a C0111 01O gy.\·63.1)1). 739-769. in th e h m e l-C a nib rian o l'so u ilic asle rn N e \% lO U n d la n 止 C a n ad ia n .10 1.irn a l LandinL. E, Narbonne,(;M . M vrow , P, 13CIRIS, A 11, and A nderson, M M , oFF.arlh Sciences, v. 20, pli. 523-526- 19148, FallilaN and (ICI)OSillOnal cnvironniclils (们 lie uppcr Precam brian Bengtson. S. M issarzhevsky. V V. and Rozanox, A YLI. 1994, 'ri-te n -cciiiii- 0WOU'lli Lower C am brian, southeastern N ew foundland: New Y ork State brian-C anibrian boundary a plea lor Ciftilion: IC C P ProJect 29 C h-CUlar M tiscuill Bulletin,、463. lip. IS一52. Ne% sleller. JLM C 1994. lip. I丰15. LLIO H } Jiang Z ,W LI X . Son, X . V ill" Y. IAU G . Z ang S. and Tao Y. 1984, Bom -ing. S A , G rotzinIger, J P. Isachsen.(一E. Knoll. A H, Pelechaty. S M . 5S1i1l1l1i之a11l1l一-(C、之a1lillhblrji., 11 1 b o)undary candidate ill M cishUcun. Jinning. Y Linnan. and K olosov, 11. 1993, C alibrating rates ol一 early Cam brian evolulion: Sci- C hina: The Peo p le ' s Publishing I , . 16 PI). encc} v. 1-6 1, pl,一]293 1298 M yrow. 11,all‘川iscoll. R N} 1993, D ellosilional hislory and sequence sn-alig- B ra sic r, N 1 D , 19 7 9 . T h e C a m b rian ra d ia tio n e v e n [. in H O LIS C. M R . C LI., 'rh e raphy (们 lie Pi-eciiiiibi-iiiii-C'iiiiiiii-i之iii bOLllldW'V SlraLotype Section. Chapel O riO n of M aJor Invertebrate groups. Academ ic Prcss. [ondon. pp. Island I}orlllatioll, som h easiern N ew l'OUndland: Palacogeography, 川 3- 160 . Palacochillatology. Palacoccology.、104, pp- 13 --35. Brasier. M 1), 1989a, China and [Ile Palacotell-tyan Belt (India. Pakistan, [ran, Narbonne, G M . 1987. Trace fossils, sm all shelly fossils und the Precam - Kazakhslan, and M ongolia). in Cow ic, .1 W . and Brasier, M 1), eds.. The brian-C am brian Boundary: ErIiSOLICS, N. 10, 33,一340. Precarnbriai卜('ainbrian B()川Idary: O XfoFd U niversity Press. pp. 40---74. N arbonne.(;M , and M yrow , 1'. 1988,Trace fossil biostrangraphy in the Pre- B raNicr. M 1). 1989h. Towards a hioSH-aLigraphy ol"die earliest skeletal biw as c a m b rian -IC,a m b i-ja n h o u lid a l-V in te rv al: N e w Y o rk S la te M u seu m B ill- in C o w ie . J W , an d B ras ie r, \14 D . e d s., T h e P i-e ciiiiib rj,.iil- ( .a iiib i-ia ii letin, 463, pp. 72--76. Boundary: O xford U niversity Press. pp. 40-74, N arbonne, (3, M , M yrow , 11, Landing, F, and A nderson, M M , 1997. A candi- Brasier, M 1), A nderson, M M , and Corlield, R M , 19921, O xygen and carbon date sLratotype for the Precam brian-C am brian boundary, Portunc Head, isotope straligraphy ofcarly C am brian carbonates in SOLItheasLu n N ew - B u rin P e n in s u la. SO U Illea SIC I-11 N e w fo u n d la nd : C a n ad ian Jo u rn a l o f E a rth foundland and England: G eological M agazine,、1219, pp. 265-279. Sciences, v. 1-4, p. 156. B rasier. M 1), K homentovsky, V V7 and Corlield, R M , 1993, Stable isolopic Q ian Y . and IlenglNon. S. 1989. Palaconlology and boostraligraphy or ihe calibration of the earliest skeletal assem blages in eastern Siberia (Pre- M CiShLICUIliall Stage ill Y unnan Province, south China-. Fossils and Strata, Canibrian-Cam brian bOLIndary): Terra Nova, v. 5, pp. 225-232. v. 24, 156 pp. Brasier, M D . Corlield, R M , Derry, L A , Rozanov. A Y u, and ZhURIVIev, A Rayner, D , 1967, The Stratigraphy ofthe British Isles: C am bridge U niversity Yu, 1994, M ultiple S 13C excursions spannin},, the Cam brian explosion to P ress, L ondon. the Boloniian crisis in Sibcria: Geology, v- 2121, pp. 455-459. Rozanov, A Y U, 1967. 1’l ie Cam brian lower boundary problem G eological B rasier, M 1), and nine others 1990. T he carbon- alid -isotope record M agazine. v. 104, pi)一4 15-434. o f th e P re c a 川b rian - C a nib rian b o u n d a rv in te rv a l in C h in a ;川cl Iran a n d Rozanov, A Y U, and Sokolov, B S. 1984, Lower Cam brian stage subdivisio,n: their correlation: G eological M algazine. v. 127, pp. 3 19-332. sLraligraphy: A kadem ii NaLik SSSR. M oscow . lzdalelsIvo 'N ULIka'. (in Conipsion. W , W illiam s, I S. Kirschvink. J I.Zhang Z . and M a, G . 1992. Zir- R u ss ian ). con U -13b ages Iroin the Farly C aM brian tinle-scale: Jou rnal 0 1"LlIe G eo- Rozanov, A Y U, and nine others. 1969. 'File Tom m olian Stage and the Cam - logical Socicl), v. 149. 171一184. b ria n L O NW r 130 1111d al-V P rO h le m : A k a d c niia N aU k S S S R , O rd e na T ru -

E p i,m d e}, V()/17, i7o .s. I 浅 三 dovogo K rasnogo Zhum eni G eologicheskii Instituta, no. 206, 380 p. (In D rJ W Cow ie has served a s Secretary R ussian) of the C am brian Subcom m ission Schopf, W J, and K lein, C, 1992, The Proterozoic Biosphere: Cam bridge (1964-1992), C hairm an and P roject U niversity Press. Leadero f t he P recam bn an-Cam brian Sokolov, B S, and Zhuravleva, I T, 1983. Low er Cam brian stage subdivision of Siberia. Atlas of fossils: Akade血i Nuak SSSR, M oscow, Trudy Insti- Boundary W orking G roup (1972- tuta G eologii i G eofyziki, v. 558. (In Russian). 1992) and as C hairm an of the Inter- W alcott, C D , 1890, The fauna of the Lower C am brian or O lenellus Zone: national Com m ission on Stratigrap砂 Tenth A nnual Report of the D irector, 1888-1889, U S G eological Survey, (1984-1992). O ngoing activity in- P a rt 1. cludes w ork w ith the lU G S G eological W heeler, H E, 1947, Base of the Cam brian System : Journal of G eology, v. Database on Geological Sites (IUGS 55, pp. 153-159. GE OSITES) and as Geological X ing Y , Luo, H , Jiang, Z , and Zhang S, 1991 , A candidate global stratotype see- A dvisor to W orld H eritage. tiona nd函int for the Precarnbrian-Carnbrianb oundary at M eishucun, Yun- nan, China: Journal ofC hina U niversity of G eosciences, v. 2, 47-57 口

D r M artin B rasier is C hairm an of t he D r M ichael T aylor, Secretary of the Subcom m ission on C am brian Strati- Subcom m ission on Cam brian Strati- graphy and Leader of IG CP P roject graphy, is a research with 303 o n P reca m b ria n- C am brian E vent the U S G eological Survey, D enver. Stratigraphy. H is research currently H is curren t resea rch in terests in clud e concentrates on the potential ofc arbon early P alaeozoic trilobite and m ollusc and strontium isotope stratigraphy for biostratigrap 勺,biofacies analysis imp roved stratigraphic resolution of the and carbonate depositional environ- late P recam brian-C am brian events, m ents. 月‘has develop ed an ecolog- and on environm ental changes assoct- ical m odelfor explaining the global ated w ith p late m ovem ents (eastern d istribution of trilobite faunas in A sia to A valonia少.H e lectures in the relation to stratifi ed ocean system s E arth Sciences D ep artm ent at O xford, and is a F ellow of S t Edm und H all.

Selected M iddle E ast P apers from G E O ’9 4 _

Presented at the M iddle East G eosciences Exhibition and C onference, April 1994, B ahrain. H osted 勿 the A m erican A ssociation of P etroleum G eologists, D hahran G eological Society, Society of E xplorationists of t he Em irates, Society of E xploration G eophysicists.

This tw o-volum e coloured publication w ill consist of over 1000 pages w ith over 700 figures. 80 technical papers w ill cover state of the art exploration and production developm ents in the w orld's m ost im portant petroleum basin. Papers cover the petroleum system s of the G ulf countries as w ell as Egypt, Syria and Y em en. T opics include: . and M esozoic Exploration Potential of the M iddle E ast .A dvances in G eophysical and G eological Technology .3-D Seism ic Interpretation and Field D evelopm ent .R eservoir G eologic M odelling · A d van ces in R eservoir C h arac t e r i s a t io n .D epositional and D iagenetic C ontrols on R es e r v o i r D i stribution · C ase H istories Papers have been review ed by th e G E O '94 Technical Com m ittee and edited by D r M I A l-H usseini To obtain a copy of t his important publication contact: Gulf PetroLink Telephone: 973 214 881 P 0 B ox 20393 , M an am a, B ahrain Facsim ile: 97 3 2 14 475 p u b lish ed b y G u lf P etro L in k