77 勿 Pi r ge n Re mane , Mi c hael G Bas s et t , John W Cowi e , Kl au s H Gohr bandt , H Ri c har d Lane , 01 可Mi c hel s e n and Wang Noi we n, wi t h t he c ooper at i on q fmen i ber s q f I CS Re vi s e d gui de l i ne s f or t he e s t abl i s hme nt of gl oba l c hr o nos t r a t i g r a phi c s t a nda r ds by t he I nt e r na t i o na l Co mmi s s i o n o n St r a t i g r a phy ( I CS) Bac kgr ound 1 Introduct i on The s e Re vi s e d Gu i d e l i n e s a r e t h e r e s u l t of c l os e c oo p e r a t i o n b e t we e n t h e Bu r e a u a n d SU b c ommi s s i o n s of I CS. A i f r s t p r o vi s i on a l d r a f t wa s p r e - pa r e d b y J Rc ma n e, Ch a i r ma n o f I CS. t a ki n g i nt o a c c ou n t p r op o s a l s ma d e b y K H Go h r ba nd t , t h e n S e c r et a r y Ge n e r a l o f I CS. A mo r e f o r ma l dr a t f wa s e s t a bl i s h e d o n t hi s ba s i s b y t h e Bu r e a u o f I CS a t i t s me e t i n g a t Th e Si l ur i a n -De v oni a n Boun da r y Commi t t e e wa s t h e ir f s t t o p ut i n t o p r a ct i c e ( i n 1 9 60) t h e pr i n ci pl e t o d e in f e c hr o no s t r a t i g r a p hi c u ni t s b y t he i r l o we r bo u nda r y on l y, whi c h t h us be c o me s a ut oma t i - c al l y t h e upp e r bou nda r y of t he un de r l yi ng uni t . Th e Si l ur i a n-De vo ni a n b oun da r y- s t r a t ot yp e a t Kl on k i n t he Cz e c h Re pu bl i c wa s r a t i ie f d a t t he 24 t h I nt e r n at i o na l Ge ol og i c a l Co ng r e s s ( I GC) a t Mont r e a l , 1 97 2. Dur i ng t hi s p r oc e s s . t he c ommi t t e e d e ve l - op e d t h e pr i n c i pl e s of ch r on os t r a t i gr a ph i c bo un da r y d e ini f t i on. Neuc hdt el ( Swi t zer l a nd) i n Mar ch 1 994. Thi s was ci r cul at ed t o al l Sub- commi ss i ons f or comment s . That dr a t f was al s o di s cus s ed a t t he I nt ema- t i o n al Sy mp os i u m on P e r i ni a n S t r a t i g r a p hy a t Gui y a n g ( Ch i n a ) i n Se p - t e mb e r 1 9 9 4, t h e 4t h I n t e r n a t i o na l Symp os i um o n J u r a s s i c S t r a t i g r a p hy a t Me n do z a ( Ar g e n t i n a ) i n Oc t o b e r 1 99 4. a n d a t t h e 2n d I n t e r na t i on a l Symp os i u m o n Cr e t a c e o u s S t r a t i g r a p hy a t Br u s s e l s ( Be l gi u m) i n Se p - t e mb e r 1 9 9 5. Th e in f a l v er s i o n, i n c or p or a t i ng a s f a r a s p o s s i bl e o r a l a nd wr i t t en comment s f r om member s of I CS bodi es, wa s wor ked out at t he me e t i ng of t h e Bu r e a u o f I CS a t Ne u c h5 t e l i n Ap r i l 1 9 9 6, a t t e n d e d b y J Remane ( Chai r man) , M G Bass et t (I s t Vi ce- chai r man) , 0 Mi chel s en ( Se c r e t a r y Ge ne r a l ) , a n d H R La ne ( I s t Vi c e - c ha i r ma n el e c t ) . a n d wa s t h e n s u bmi t t e d f o r v o t e t o t h e f u l l Co mmi s s i o n o f I CS ( c on s i s t i n g of t h e iv f e me mb e r s o f t he Bu r e a u of I CS a n d t h e 1 6 Ch a i r p e r s o ns o fI CS Su b - commi ss i ons) . I n t h i s v o t e , t h e Re v i s e d Gu i de l i n e s we r e a pp r o v e d by t h e f u l l Co m- mi s s i on wi t h a n o v e r whe l mi n g ma j o r i t y, wi t h on l y on e o p po s i n g v ot e . Th e Re v i s e d Gui d e l i n e s a r e t h u s a f or ma l a n d ma n da t o r y d oc u me n t r e g - ul a t i ng t h e p r oc e du r e t o b e f ol l o we d i n t h e d e in f i t i o n o f c h r on o s t r a t i - gr ap h i c b ou n da r i e s . Th e pa r t i c u l a r i mpo r t a n c e o f t hi s t e x t l i e s a l s o i n t h e f a c t t ha t t h i s i s t h e ir f s t do c u me n t on s t r a t i gr a ph i c p r o c e d ur e i s s u e d by I CS whi ch r epr es ent s a vot ed f or mal agr eement . Contents I Int roduct i on 2 Ai ms a nd pr i nc i pl es These ' l es sons l earned' ( McL. ar en, 1 977: 23) cons t i t ut ed t he bas i s of t h e ir f s t Gu i d el i n e s of I CS, wh er e t he c o nc e p t o f t h e Gl ob al St a nd a r d St r a t ot yp e- s e c t i on a n d Poi n t ( GSSP) wa s i nt r od uc e d: T hi s Bo un da r I v St r a t o t y pe S e c t i on a nd Poi nt i s t he de s i gna t e d ( y pe o fa s t r at i gr a phi c bou n dar y i de nt i ie f d i n pub l i s h e df o r m an d mar k e d i n t h e s e c t i o n as a s pe c诱c poi nt i n a s pe c 币c s e q ue n c e可. r o c k s t r at a a nd c o ns t i t u t i ng t he s t an d ar df or t h e de f i ni t i on a nd r e c og ni t i on o , f ' t h e s t r at i gr a phi c b ou nd ar y be t we e n t wo n ame d gl ob al s t r at i gr a phi c ( c hr on os t r at i gr a ph i c ) uni t s ( Cowi e a nd ot h e r s , 1 9 86: 5) . Thi s def ini t i on i s st i l l val i d for t he Phaner ozoi c. A GSSP vot ed by t h e Ful l Commi s s i o n o t I CS ( t h e Bur e a u o f I CS a nd Cha i r pe r s on s of al l I C S Subcommi ssi ons, s ee al s o Bass et t , 1990) and conf ir med by t h e Exe c u t i ve of t he I n t er na t i on al Uni on o f Ge ol og i c a l Sc i en c e s ( 1 UGS) r e p r e s e n t s a r a t i ie f d b oun da r y de ini f t i on Th e ne c e s s i t y f o r a pr e c i s e g l o ba l c hr o nos t r a t i gr a p hi c s ca l e i s obv i ous . Res e a r c h o n gl ob a l e v en t s me a ns c omp a r i s on of s t r a t i - gr a p hi c doc u me nt s f r om di s t a n t r e gi on s -b ut ho w c a n we b e s ur e t o d ea l wi t h t h e s a me e v e nt t h r ou gh ou t , wi t h o ut ha vi n g a p r e c i s e a n d r e l i a bl e ch r on os t r a t i g r a phi c s c a l e ' ? ' I he s a me i s t r u e f or t h e es t a bl i s h- me nt ot e us t a t i c s e a - l e v el cu r v es o r t he r ec o ns t i t u t i on o f gl o ba l c l i - ma t i c ch a ng e s i n t h e p a s t . P r o g r e s s i n t h e s e a n d ma ny ot he r ie f l d s o f g eo l o gi c al r e s ea r c h i s on l y p os s i b l e i f pr o gr e s s i s a l s o ma de i n t h e def ini t i on of chr onost r at i g r aphi c uni t s. 2. 1 Ai ms of t he r evi si on 2. 2 The Pr ecambr i an St an dar d 2. 3 Co r r el a t i on pr e c e d es de ini f t i on 2 Ai ms and pr i nc i pl es 24 Pr i or i t y a n d na t ur a l b oun d ar i e s 2. 5 Bo un da r y - s t r a t ot yp es i ns t e a d ot un i t - s t r a t o t y pe s f o r c h r on os t r a t i gr a p hi c u ni t s 2. 1 A i m s of the revi si on 3 The choi ce of t he be st boundary l evel 3 . 1 Some g en e r a l c o ns i d er at i o ns on c h r o n os t r a t i gr a ph i c me t hod s 3 . 2 The be s t bo un da r y l e ve l 4 Re qui r eme nt s f or a GSSP 4. 1 Ge ol ogi c a l r e qu i r e me n t s 4. 2 Bi os t r a t i gr a p hi c r e q ui r em e nt s 4. 3 Ot her met hods 4. 4 Ot her r equi r ement s i nal Gui del i nes. Never t hel ess, a caut i ou s r evi si on of t he Gui del i nes 5 Submi s si on of a GSSP 5. 1 Edi t i n g o f t he s u bm i s s i o n 5. 2 Vot i ng pr ocedur e 6 R evi si on of a G SSP 7 Sel ect ed ref erences Ernsodes, Vol. 19. no. 3 Th e or i gi na l Gui de l i n e s we r e i s s u ed by t h e Bu r e a u of I CS ( Co wi e a nd ot he r s , 1 986 ) an d s umma r i s e d by Cowi e( 1 9 86 ) i n Epi s od e s , t h e o ic f i a l pu bl i c a t i on of l UGS, a nd by Cowi e( 1 9 90 , 1 9 9 1 ) . The y ha v e gu i d e d uni f o r mi t y o t d ef i n i t i o n f or 2 0 c hr o no s t r a t i gr a p hi c b ou nd- a r i e s d ur i ng t e n ye a r s o t s uc c e s s f ul a pp l i c a t i on. Th e ex p e r i e n c e g ai ne d i n t h i s pr o c e s s h a s c on ir f me d t he ba s i c p r i nc i pl e s o t t he o r i g- a pp e a r s us e f u l f o r di f f e r en t r e a s ons : I Th e Pr e ca mb r i a n Su bc o mmi s s i on o t I CS h as pr opo s e d a g l o ba l st r at i gr aphi c s ubdi vi s i on f or t he Pr ot er oz oi c wher e boundar i es a r e de ine f d i n t e r ms of a bs ol ut e a ge s ( s e e s e c t i on 2. 2) , wi t h e nt i r e l y n ew na me s f o r t he ni ne Pr ot e r oz o i c s ys t e ms c r e a t e d on 7N t hi s bas i s . The r es ul t ant new S ubdi vi si on of t he Pr ot er ozoi c was Th er e i s n o f or ma l p r i o r i t y r eg ul a t i on i n s t r a t i gr a ph y. The r e- f or e , i n r ed e ini f ng b ou nd ar i e s , p r i o r i t y c a n b e g i v en t o t h e l e ve l wi t h t on, 1 989; i t i s t hus f or mal i s ed ( and s houl d t her ef or e not have t h e be s t c o r r el a t i on p ot e n t i al . I h e r e d ef in i t i o n wi l l gi v e L I S t h e opp o r - been omi t t ed i n t he 2nd edi t i on of t he I SG) . t u ni t y t o us e f o s s i l g r ou ps ( S u c h a s c o no don t s ) an d me t h od s of 2 Dur i n g t h e l a s t ye a r s , gr e at pr o gr e s s ha s b e e n ma d e i n t h e he l d ch r ono cor r e l a t i on ( S u ch a s t r i a -t i et os t r a t i a r a phy) whi c h we r e of n on- bi o s t r a t i gr a p hi c me t ho ds o f c or r e l a t i o n ( s ee s e ct i o n 3. 1 ) un . kn own or p oo r l y de v el o pe d a t t he t i me ( i f t he or i g i n a l de ini f t i on. Th e s e s h ou l d t h er e f o r e be gi ve n mo r e wei ght i n t he c hoi c e of Thi s d oe s n ot me a n t h a t pr i or i t y s h oul d b e t ot a l l y n e gl e c t e d. Pr a c t i - b ou n da r y l e ve l s a n d t y pe - s e c t i ons . c al c on s i de r a t i on s Wi l l i nc i t e L I S t o l i mi t c ha n ge s t o t h e n ec e s s a r y 3 Cer t a i n pr o bl e ms c on c e r ni ng t h e ph i l o s op hy of bo un da r y d ef i ni - mi n i mum. I t ' , h owev e r , t he I nt e r r e gi on al c or r e l at i o n po t e n t i al of a t i on c a me up r e pe a t e dl y i n r e c en t d i s cu s s i ons of GSSP c a nd i - t r a d i t i o na l bo un da r y do e s no t co r r e s p on d t o t h e n e ed s of mo de r n d a t es , s u c h a s t h e ne ce s s i t y t o r e s p e c t pr i o r i t y , t o ha v e n a t u r a l s t r a igr f a p hy, i t s p os i t i on ha s t o be c h an g e d. b ou n da r i es ( s e e s e c t i on 2 . 4) , t he r ol e of f os s i l s i n b oun da r y d e h - Chr o nos t r at i g r a ph i c b oun da r i es a r e c o n vc n t i on al bou n da r i es . n i t i o n ( s e e s e c t i o n 3. 1 ) , a n d t h e de gr e e t o whi c h gl o ba l c or r el a - Th e y a r e a ma t t e r of n or ma t i v e s ci en c e an d c a n be de c i d e d b y a t i o n h a s t o b e e x a c t be f o r e de hni ng i t b oun d ar y ( s e e s e c t i on 2. 3) . ma j or i t y vo t e ( Cowi e a n d ot he r s , 1 986 ) . To a c e r t a i n de g r e e, t h i s 4 S i nc e t h e p ub l i c a t i o n o f t he o r i gi n a l Gu i de l i ne s ( Co wi e e t a l 二 pr i n ci pl e c a n b e r e c on c i l e d wi t h t h e de ma n d f or n a t u r a l bo un da r i es . As st at ed above, mos t of t he cl assi cal boundari es ar e not cl ear - cut 1 9 8 6) , i mp or t a n t p ub l i c a t i on s on t h e p r i n c i p l e s of s t r a t i g r a p hy h av e a p pe a r e d . e s p e ci a l l y t h e 2n d e di t i o n( 们h e I n t e r na t i on a l St r a t i - bu t co r r e s p on d t o c r i t i c a l bi ot i c a nd / o r cl i mat i c t r a ns i t i on s . Pl a ci ng a g r a p hi c Gu i d e ( I SG) ( Sa l v a d o r , 1 9 9 4) , o r Ha r l a n d( 1 99 2) . Th e b ou nda r y wi t hi n s u c h a n i nt e r v a l wi l l p r e s e r v e t h e a dva n t a g e of ha v - p os i t i o n o f t h e Gu i de l i n e s i n t hi s n e w c o n t ex t ha d t o h e c l a r i ie f d . i ng s u c c es s i v e u ni t s whi c h a r c di s t i ng ui s h e d b y t he i r c on t e nt s . But The r ol e of t he Gui del i nes r emai ns, however , Unchanged. Th ey whe r e e x a c t l y t he b ou nd a r y i s t o b e pl a c e d, a r e ma t t e r s of c on v en t i on r e g ul a t e t h e pr o c e du r es of b oun d ar y de ini f t i of l . t h e s e l e c t i on of a n a n d pr a c t i c a l co ns i d er a t i ons . a p pr o pr i a t e b oun da r y l e v el , a nd t he c o r r e s p on di n g v ot i ng pr o c e - On c e a bo un da r y i s ( r e ) d ct i ne d b y a GSSP ora GSSA, i t s h ou l d d ur e s ( al s o p a r t l y d e al t wi t h i n a r t i c l e s 3 an d 7. 1 of t h e s t a t ut e s o f b e us e d i n a l l p u bl i s h e d hg ur e s an d t a bl e s . Su c h a n obl i g a t i on wi l l I CS) . Th e y f u r t h e r de in f e t h e r e q ui r emen t s t o he f ul f i l l e d b y t h e s t r a - n ot h i n de r a ny au t h or s f r om e xp r es s i ng t h ei r pe r s on al opi ni on s t ot yp e - s e c t i o n ho us i n g t h e bou n da r y p oi nt . v o t e d b y I CS a nd r a t i ie f d b y l UGS a t t h e 2 8t h I GC i n Wa s hi ng- 2. 2 The Precam bri an St andard The n e w bou nd a r y- t yp e d ef ini t i on , ir f s t i n t r o du c e d f o r t h e Pr ot cr o - z o i c i n 1 98 9, wa s n e c e s s i t a t e d by t h e l a c k ofa d e qu at e f os s i l s i n mos t of t he Pr ecambr i an. I t i s t er med her ei n t he Gl obal St andar d St rati - gr a ph i c Age ( GSSA) . De ini f ng bou n da r i es i n t er ms 01 ' a b S OI L I t c a g es me a ns t ha t t h e nu me r i ca l v al u e of t h e bo un da r y a g e i s a t he o r e t i c al po s t ul a t e . i nd e pe n de n t of t h e me t h od a ppl i e d t o ob t a i n n ume r i c al a g es . But , a s i n t h e c a s e ofb oun da r i e s d e f i ne d by a GSSP, a n ex pl i c i t mot i v a t i on f or t h e c hoi c e of t he pr o po s e d n ume r i c al v al ue s hou l d be gi ve n , c l a r i f yi ng , a t t h e s a me ume - i t s r e l a t i o n t o t r a di t i o na l b oun d- a r y de in f i t i o ns . GSSAs h a v e t h e s a i ne s t a t us f or bo un da r y d ehn i t i on i n t he Pr ecambr i an as GSSPs have i n t he Phaner oz oi c. 2. 3 Cor r e l at i on pr e c e de s de ini f t i o n Exc e p t f o r t he Pr ec a mb r i a n, t hi s p r i n c i p l e i s s t i l l v a l i d. To d e hne a b ou nd a r y ir f s t a n d t h e n e v al ua t e i t s pot e nt i a l f or l on g- r a n ge c or r e l a - t i o n ( a s ha s b e e n p r op os e d i n s ome c a s e s ) wi l l mo s t l y l e a d t o b ou nd - a r y de in f i t i o ns of l i mi t e d p r a c t i c a l v al u e. On t he o t h e r h a nd , i t Woul d b e un r e a l i s t i c t o de ma nd t h a t a gi v e n b ou nd a r y b e r e c ogn i s a bl e al l o ve r t he wor l d be f o r e i t c a n b e f or ma l l y d ef in e d. I n e a c h c a s e we mu s t in f d t h e b e s t po s s i bl e c omp r omi s e . ot he r wi s e t he , ca t c h f or t h e Hol y Gr a i l o f t h e p e r f e c t GSSP wi l l ne v e r en d. 2 . 4 Pr i or i t y a nd na t ur a l boundar i e s Ou r ma i n t a s k f or a nu mb e r of y e a r s wi l l b e t o de v el op pr e c i s e bo un da r y d ef in i t i o ns f or t r a di t i on al c hr on os t r a t i gr a p hi c u ni t s . Mos t o f t he m we r e d ef i n e d i n t h e l a s t c en t u r y b y t h ei r c ha r a c t er i s t i c f os s i l c on t en t s , a nd t he i r bou n da r i e s c oi nc i de d wi t h s p e c t a c ul a r bi os t r a t i - g r a p hi c a n d l i t h ol ogi c ch a n ge s . Th es e wer e ' na t ur a l ' b ou nda r i e s , i n p e r f e c t ag r e e me nt wi t h t h e c a t a s t r o ph i s t p hi l o s o ph y of t ha t t i me . I n r e a l i t y, r a pi d f au n al t u r nov e r s a r e t o a c e r t a i n e xt en t a r t e f a c t s du e t o s t r a t i g r a phi c g a ps or c on d en s a t i o n. Mos t o f t h e cl a s s i c t yp e - l o c ah - t i e s a r e t hu s u ns ui t a bl e f or a pr e c i s e b oun da r y de ini f t i on: we ha v e t o l ook f or new s ect i ons wher e sedi ment at i on i s cont i nuous acr oss t he b ou nd a r y i nt e r v a l ; bu t t he n b ou nd a r i e s wi l l r a r e l y c or r e s p on d, t o a l i t h ol o gi c c ha n ge . Th e i d e a t h a t c hr on os t r a t i gr a p hi c bo un d ar i e s s h oul d a l wa ys c o r - r e s p o nd t o s ome t h i n g ' vi s i bl e ‘ h a s a l s o l e d t o c on f l i c t i ng r e g i o na l * d e f - i n i t i on s ' of i n t e r n a t i o na l c h r on o s t r a t i g r a ph i c bo un da r i e s , wh i c h we r e a da p t e d t o r e g i on al l i t ho s t r a t i g r a p hi c bo un d ar i e s of di f f e r en t a g e s , 2 . 5 Bounda r y- s t r at ot ype s i ns t e a d of uni t - s t r a t ot ype s 1 1 ' c h r on os t r a t i or a p hi c u ni t s we r e de hn e d by u ni t - s t r a t ot ype s , t he b o und a r y b e t we en t wo a d j a c e nt Uni t s Wo ul d b e d e ine f d b y t wo s e pa - r a t e GSSPs : a s t h e L i pp e r b ou nd a r y of 一 t he l ower u ni t i n on e u ni t - s t r a - t o t y pe a nd a s t h e l owe r bo un da r y of t h e s u c ce e di n g un i t i n t h e o t h e r . Th e Gl ob al Chr ono s t r a t i I - r a p hi c S ca l e mus t , h owev e r , c ompr i s e s t r i c t l y c ont i g uo us Uni t s , wi t ho ut ov e r l a ps a nd wi t h n o g a ps be t we e n t h em. Bu t t he r e i s n o me t h od ofc or r el a t i on whi c h wou l d gu a r an t e e a p er f e c t i s oc hr ony of t wo s e pa r a t e b ou n da r y p oi n t s . ev e n a t a s h or t di s t a nc e a pa r t ( Ha r l a n d, 1 9 92) . Thi s pr obl em was a l r e a dy r e c og ni s e d i n t he ir f s t e di t i on of t h e I SG ( He db e r g, 1 976) . bu t un i t - s t r a t ot y pe s f or c h r on os t r a t i gr a p hi c un i t s we r e s t i l l a dmi t t ed a s a n a l t e r n a t i v e p os s i b i l i t y. I n t h e s e co nd e di t i on ( Sa l v a d or , 1 9 94) . b o und a r y- s t r a t ot yp es a r e gi v en a s t r o ng e r pr ef er en c e , bu t as a wh ol e, t he pos i t i o n r ema i ns a mbi gu ous : ' Si n c e t he onl y r e co r d o f g e ol ogi c t i me. 二l i e s i n t he r oc ks t h e ms e l v e s , t h e b e s t s t a nd ar d f o r a c hr on os t r a t i o r a phi c un i t i s a b od y o f r oc ks f or me d b e t we e n t wo d es i g na t e d i ns t a n t s o f g e o l o gi c t i me . ' ( Sa l va do r , 1 99 4: 8 8) . I h e Gu i de l i ne s o f I CS a r e u n ai r i b i g uou s : Chr onos t r at i gr a phi c uni t s o f t he Phane r o z oi c Gl obal St a ndar d c an onl y be de ine f d t hr o ugh boundar y s t r a t o t ype s . Ev e n s h ou l d t he s i t u a t i on a r i s e ( e. g. i t s i n t h e Si l u r i a n s t r a t o t yp e s i n Br i t a i n) t h a t t he GSSPs de in f i n g t h e l owe r a nd L i p pe r b oun da r i e s o f on e- an d- t he - s ame u ni t a r e l oc a t e d i n t h e s a me s e c t i on , t h i s do es n ot i mpl y t ha t t h e s t r a t i g r a phi c i n t e r v al a nd i t s h i ot a b et we en t h e t h e t wo GSSPs r e p r es e nt a u ni t s t r a t o t yp e . F or s ev e r a l s ys t ems , L i pp e r a n d l ower bou n da r i e s a r e no w de in f e d b y GSSPs . Fol l o wi n g t h e c ho i c e of t he b es t t y pe - s ec t i o n t h e s e a r e l oc a t e d i n di s t a nt r e gi on s : t he ba s e of t h e Si l u r i a n i n Sc o t - l an d, M t h a t o f t h e De von i an i n t h e Cz e c h Rep ubl i c; t h a t of t h e Ca r bo ni f er ous i n t he Mo nt a gu e Noi r e - Fr a nc e } of t h e Per mi a n i n Ka z ak hs t a n: a nd t h e b as e of t h e Qua t e r na r y i n I t a l y. Th e l owe r b ou nda r i e s o f c hr on os t r a d g r a phi c un i t s of hi gh e r r a n k ( s er i e s , s ys t e ms e t c. ) ar e a ut oma t i c al l y d ehn e d b y t he b as e o f t he i r l ower mo s t s t a g e. I n ot h e r wor ds : t h e l owe r b oun da r y of a s ys - t e r n i s a l wa ys al s o a s e r i e s a n d a s t a ge bo un da r y, A GSSP c a nn ot b e c ompa r e d t o t h e hol o t yp c of Zool og i ca l Non i e n cl a t t l r e } i t c o r r es p on ds r a t he r t o a s t a nd a r d of mea s ur e i n p h ys i c s ( Ha r l a nd, 1 9 92) . Th e u s e oft er ms l i k e h ol os t r a t ot y p e, pa r a - s t r at ot yp e e t c . s h o ul d t he r e f or e b e a v oi d e d ( Co wi e a nd ot he r s , 1 98 6) . I f r e f e r en c e s e c t i ons a n d p oi n t s s e em n e c e s s a r y i n or d er t o gi v e a b e t - t e r un de r s t a ndi n- of t h e bo un da r y i n a n ot he r f a ci e s or pa l c obi o ge o- 1 1 r a p hi c c on t e x t , a n a uxi l i a r y s t r a t o t y pe p oi n t i na y b e d ef in e d. Su c h a uxi l i a r y p oi nt s a r e s ub or di na t e t o a GSSP. , S el wi nber 1996 79 3 The c hoi c e of t he bes t boundar y l e ve l 3. 1 Some general cons i derat i ons about c hr ono s t r at i g r aphi c me t hods Chr o nos t r a t i gr ap h y a n d c h r on oc or r e l a t i o n ha v e b e e n di s c us s e d a t l e n t a } t h i n t h e I SG ( Sa l va d or , 1 9 94) . We ma y t hu s l i mi t t h e f ol l owi n g di s c us s i on t o s e l e c t e d t op i c s wh i c h a r e o f pa r t i c ul a r i mpo r t a n c e f or t h e c h oi c e o t t he b oun da r y l e ve l . Cons i d e r a bl e p r og r es s ha s b e e n ma d e i n t h e f a s t f e w y e a r s i n de v e l op i n g an d i mp r ov i n g met ho ds o f non - bi os t r a dg r a phi c c h r on o- c or r e l a t i o n. Sor r i e o f t h ei n a r e b a s e d on ge oc h ei ni c a l s i g na l s , l i ke t he f amous I r - s pi k e us e d as gu i da n c e f or t he de ini f t i on of t h e Cr e t a - c e ous -Pa l e og e ne b oun da r y , or on s h i ts f of s t a bl e i s o t op e s whi c h s h oul d b e h e l p f 一 ul i n t he d ef in i t i on o f t he Pe r r ui a n -Tr i a s s i c b ou nd a r y ( Bau d a n d ot he r s , 1 989) . Rev e r s a l s o f t h e Ea r t h' s ma gn e t i c f i e l d a r e i mpo r t a nt , be c a u s e t h e y a r e a wor l dwi de p he n ome no n a n d p r a c t i c al l y i n s t an t an e ou s , t hu s pr o vi di n g a p r e ci s e an d r e l i a bl e me a ns o f c hr o no c or r e l at i o n. La t e J ur a s s i c t o Re c en t r e v e r s a l s ha v e b ee n c a l i br a t e d t o t h e Ma g- ne t i c P ol a r i t y Ti me Sc a l e ba s e d on oc e a ni c an oma l i e s ( Ha i l wo od, 1989) . Ge op hy s i ca l a nd g e oc he mi c a l e ve n t s a r e , h owe ve r , r ep e t i t i ve a nd do no t a ] l o w a n un e qui v oc a l de t e r mi n a t i on o ft h e a ge . Th e y n e e d c al i b r a t i on t h r ou gh r a di oi s o t op i c o r bi os t r a t i gr a p hi c da t i n g. Un i f or m- na t el y, r a di oa c t i v e i s ot op es a r e r a r el y av a i l a bl e wh e r e ne e d e d s o t h a t s t r a t i gr a phi c r out i n e wor k de p e nds mo s t l y on o t h e r me t h o ds . Bu t r a di oi s ot op i c da t i n gs a r e ve r y i mpor t a n t f or t h e q ua nt i t a t i ve c a l i br a - t i on o f r el a t i v e a ge s . Bi os t r a t i g r a p hi c b oun d a r i e s , i . e. t h e b oun da r i e s of t h e ma t e r i a l s t r a t i gr a ph i c o cc u r r en c e of s p e c i es , a r e di a c hr on o us ( I SG) . Thi s f a c t ha s , h owe ve r , b ee n ov e r s t a t e d. A s p e c i e s ex i s t s f o r a ini f t e s pa n of t i me a nd i s t h er e f or e c h a r a c t e r i s t i c o f a c er t a i n g e ol o gi c i nt e r v a l . I n r a pi dl y ev ol vi ng l i ne a ge s t hi s ma y be l e s s t h an on e mi l l i o n y ea r s , s o t h a t mos t b i o s t r a t i gr a ph i c da t i n gs a t t a i n a h i g he r d e gr e e of r es ol ut i on t h an t h e u s e of r a di oi s o t o pe s . Th e us e of f os s i l s f o r c al i br a t i n g c h r on os t r a t i g r ap hi c un i t s do e s not o nl y i nv ol ve t r a c i n g o f bi os t r a t i g r a phi c bou nd a r i e s . I t i s i nd e e d l e s s a ma t t e r of c o r r el a t i on t h a n o f de t e r mi ni ng r e l a t i v e a ge s wi t hi n a bi oc hr ono l o gi c s t a n da r d of r e f e r e n c e. Bi o c hr o nol og y i s t h e r ec o n- s t r u c t i on of t he s u cc e s s i on of s pe c i es i n t i me t h r ou gh t h e s ynt he s i s of l o c al a nd r e gi on a l bi os t r a t i g r ap hi c da t a ( f or a r e c e nt ov e r vi ew, s e e Re ma n e , 1 991 ) .Th e c h r on os t r a t i gr a p hi c r e l i a bi l i t y of bi os t r a t i - gr a p hi c b ou nd a r i e s c a n t hu s b e t e s t e d by c ompa r i ng da t a f r om d i f - f e r en t s pe c i e s . I n t hi s pr o ce s s , ma t h e ma t i c a l a p pr o a ch e s ( Qua n t i t a - f i ve St r a t i g r a ph y) pl a y a n i n c r e as i n gl y i mpo r t a n t r ol e ( Gr a ds t ei n a n d ot her s, 1985} Guex, 1 991;M a nn and Lane, 1 995) . F os s i l s p e ci e s de pe n d o n t he e nv i r o nme n t a n d a r e bi og eo g r a p h- i c a l l y l i mi t e d. An a p pr op r i a t e c ho i c e o f wi d e s p r e a d s pe c i es ma y di mi ni s h bu t n e ve r t ot al l y e l i mi n a t e t h es e s h or t c omi n gs . Ra di oa c t i ve i s ot op es d o n ot s u f f e r f r o m t h es e g e og r a ph i c a l r e s t r i c t i o ns : bu t t h e i r r es ol ut i o n di mi ni s h e s wi t h i n c r e as i ng a g e. Th er e f o r e, no n- bi os t r a t i - gr a p hi c ma r k e r s l i k e ma gn e t i c r e v er s al s a nd s t a bl e i s ot o pe s h a ve ga i ne d i nc r e a s i ng i mpo r t a n c e i n l on g- r a ng e l a t e r a l co r r e l a t i o n. Th e b ou nd a r y d ef in i t i o n wi l l n or ma l l y s t a r t f r om t h e i de nt i ic f a - t i on of a l e ve l whi c h c a n b e c ha r a c t er i s e d b y a ma r ke r e v en t o f o pt i - i na l c o r r el a t i on p o t e n t i al . Thi s ma r k e r ev e nt ma y b e a ma g ne t i c r e ve r s al , s ome ki nd o f ge oc h e r n i c a l o r i s o t o pi c s i gn a l , or t h e ir f s t a pp e a r a nc e or l a s t oc c u r r e nc e of a f o s s i l s pe c i e s . Howe ve r , on l y t h e bo un da r y p oi n t i n t h e s e c t i o n, t h e GSSP ( Cowi e e t a l . . 1 986 ) f or - i nal l y de ine f s t h e bo un da r y. Thi s me a ns t h a t a n oc c u r r e nc e o f t he p r i - ma r y mar k e r d oe s n ot a ut oma t i c a l l y d et e r mi n e t he bo un da r y. Ot he r mar ker s s houl d t her ef or e be avai l abl e near t he cr i t i cal l evel , i n or der t o s u p por t c h r on os t r a t i gr a p hi c c or r e l a t i on i n s e c t i on s ot he r t ha n t he GSSP. I f t h e p r i ma r y ma r k e r i s a f os s i l s pe c i e s . ir f s t a pp e a r a n c e s a r e ge n e r al l y mor e r e l i a bl e t ha n ex t i nc t i o n e v e nt s , e s p e c i a l l y i t t he g r a d- ual t ransi t ion bet w een t he m arker and i ts ancestor can he observed. 4 The r equi r ement s f or a GSSP Th e da ng e r of e t e r n al i s i ng t h e s e a r c h f or t he be s t t yp e - s e c t i o n h a s a l r ea dy be e n a d dr e s s e d i n s e c t i o n 2 . 2. 1he s t r at ot y pe - s e c t i o n s h oul d c on t ai n t he be s t po s s i bl e r e c or d of t he r e l e v a nt mar ke r e v ent s . I n t hi s s e ns e , t h e r e q ui r e me nt s l i s t e d be l ow c ha r a c t e r i s e t h e i de a l s e c t i on . Not a l l of t he m ca n b e f ul il f l e d i n e v e r y ca s e , b ut t he f a c t t h a t al l GSSPs a r e v o t e d b y I CS i n a c c o r da n c e wi t h t he pr e s e n t Gu i d e l i n es i n s ur e s t ha t le f xi bi l i t y wi l l n ot de g e ne r a t e t o a r b i t r a r i n e s s . 4. 1 Geol ogi cal requi rement s Expo s ur e ov e r a n ade quat e t hi c kne s s of s e di men t s i s on e r e qu i r e me n t t o g ua r a n t e e t h a t a s u fi c i en t t i me i n t e r v a l i s r e pr e - s e n t e d b y t h e s e c t i on , s o t ha t t he bo un da r y ca n al s o be d e t e r - mi n e d by i n t e r p ol a t i on , us i ng a ux i l i a r y ma r k e r s c l o s e t o t h e boundar y. Co nt i nuo us s e di me nt a t i on: n o g a ps , n o c o nd en s a t i on i n p r o x- i mi t y of t h e b oun da r y l e v el . The r at e of sedi m ent at i on s houl d be s uf i ci ent t hat success i ve e v en t s c a n be e a s i l y s e pa r a t e d. Abs e nc e o f s y ns e di me nt ar y a nd t e c t oni c di s t ur ba nc e s . Abs e nc e o f me t amor phi s m and s t r ong di a ge ne t i c a l t er a t i on ( i d e nt i ic f a t i on of ma gn e t i c an d g e oc h er ni c a l s i gn a l s ) . 4. 2 Bi ost r at i graphi c r equi r eme nt s Abunda nc e a nd di v er s i t y of we l l - pr e s e r ve d f os s i l s t h r ou gh ou t t h e c r i t i c a l i n t er va l . Di ve r s i ie f d b i ot a s wi l l o f f e r t h e be s t po s s i - bi l i t y off i r e c i s e c or r e l a t i on s . Abs e nc e o f ve r t i ca l f a c i e s c ha nge s a t or n e a r t he b ou nd a r y. A c ha n ge o f l i t ho- o r b i o f a c i e s r e le f c t s a c h a ng e o f e c ol og i c c on di - t i on s whi ch may ha v e c o nt r ol l e d t h e a p pe a r a n c e of a g i v e n s p e c i e s a t t h e b ou nd ar y l e v el . A s h a r p l i t ho f a c i a l c ha ng e ma y a l s o c or r es po nd t o a hi a t u s . ' An obv i o us b ou n da r y s ho ul d b e s u s p e c t ' ( Cowi e a n d ot he r s , 1 98 6) . Fa v our abl e f a c i e s f o r l ong - r ang e bi o s t r at i gr a phi c c o rr e l l a - t i ons ; t hi s wi l l no r mal l y c or r e s pon d t o a n o pe n ma r i ne e n vi r on- me nt wh er e s pe c i es wi t h a wi d e g e og r a phi c r a ng e wi l l b e mo r e c ommo n t h a n i n c oa s t a l a n d c on t i ne n t a l s e t t i n gs . Th e l a t t e r should ther efore be avoi ded. 3. 2 The bes t boundary l eve l Wi t h t h e a bov e c on s i de r a t i o ns i n mi n d, t h e c or r e l a t i on po t e nt i a l o f a ny b ou nda r y l e v el s h oul d b e t e s t e d t h r ou gh a d e t a i l e d s t u dy o f s e v- e r a l c on t i nu ous s u c c es s i on s c ov e r i n g t h e c r i t i c a l i nt e r v a l , i f p os s i b l e on di f f er ent cont i nent s. The mos t sui t abl e of t hes e s ect i ons can t hen be s e l e c t e d f or de ini f t i on o f t he GSSP. I f t wo b ou nd a r y l e v el s o f e qu a l co r r e l a t i o n p ot e nt i a l a r e a v ai l a bl e, t h e be t t e r c a n di da t e ( s ee c ha p t e r 4) wi l l d e c i d e t h e c h oi c e o f t he b oun da r y l e ve l . Thi s i mpl i e s t h e i n t e g r a t i on of da t a f r om di f f e r e n t f a c i e s a n d pa l e og e ogr a p hi c p r ov i n c es i n a gl o ba l s yn t h es i s . The p er f e ct GSSP, wh e r e a l l e l e me n t s of s u c h a s yn t h e s i s a r e we l l r e p r e s e n t e d, wi l l of ten not be avai l abl e. Fl exi bi l i t y i s t her ef or e necess ar y i n or der t o ma ke a t i mel y d ec i s i on. Epi s ode s, Vol . 19, no. 3 4. 3 O ther m ethods M a g n et os t r a t i g r ap h y , s e qu e n c e s t r a t i g r a ph y , c yc l o s t r a t i g r a p hy , a n al y - s i s o f s t a bl e i s ot op e s s ho ul d b e gi ve n du e we i gh t i n t h e s el e c t i on of a GSSP. I f a c h oi c e ha s t o b e ma d e b e t we e n c a n di da t e s ha v i n g mor e o r l e s s t he s a me bi os t r a t i gr a p hi c qua l i t i e s , t h e o n e o f f e r i n g t he be t t e r a p pl i c a t i on s o f n o n- b i os t r a t i gr a p hi c me t ho ds s h o ul d b e pr e f e r r e d. Radi o i s ot o pi c dat i ng. Wh e ne v e r p os s i bl e, i t i s i mpo r t a nt t o a c hi e ve di r e c t q ua n t i t a t i ve c a l i br a t i o n ( n ume r i c al a ge ) o f a c h r on os t r a t i gr a p hi c b ou nd a r y a t t h e GSSP. Mag ne t os t r a t i g r aphy. A r e p r odu c i bl e ma g ne t i c r e v er s a l s t r a t i gr a p hy i s a d es i r a b l e r e qu i r eme n t i n or d e r t o kn o w w h e r e i n t h e ma g ne t os t r a t i gr a p hi c s e qu e n c e t h e GSSP i s l oc a t e d. so Che mos t r at i gr aph y. i n cl u di n g t h e s t u dy of 、 ve r t i c a l c h a ng es of ' t h e p r op o r t i o ns ol ' s l a bl e i s o t o pe s , whi ch ma y b e i n di c a t i v e o t gl ob a l e v en t s . Th e r e gi on al pa l c og e ogr a phi c a l c on t ex t a n d t h e f a c i e s r e l a t i o n- s h i p s o t t he s t r a t o t y p e- s e c t i on s ho ul d b e c l a r i ie f d. Kn owl e d ge ot t h e s e qu e n c e s t r a t i g r a ph y wi l l c ont r i b ut e t o a n U nd e r s t an di ng of ' t hes e r el at i ons 2 I f t hi s ob t a i ns t h e s t a t u t or y wor ki ng ma j or i t y川t he Wo r k i n g Gr o up. me mb er s of t h e r e s pe c t i v e Su bc ommi s s i o n wi l l v ot e o n wh e t h e r or n o t t h e c a n di da t e b e a p pr ov e d. 3 I n t h e c a s e ofa s t a t u t or y ma j o r i t y be i ng i n f a vo ur , f or mal s u b- i ni s s i on o f t h e c a n di da t e t o I CS f o r a ppr o va l . 4 Ag a i n , i n t h e ca s e ofa s t a t ut or y ma j or i t y, s u bmi s s i on of t h e GSSP or GSSA candi dat e t o t he I UGS Execut i ve Commi t t ee f or r a t i f i c a t i on. t og et he r wi t h a n a bs t r a c t o f t h e s u bmi s s i o n, p r e - p a r e d b y t he r e s p ons i bl e I CS bo dy. I CS s h oul d a t t e mpt t o in f al i s e , w i t hi n t h r e e y e a r s a te f r I UGS ' I h e GSSP s h ou l d be i n di c a t e d b y a pe r ma n en t l y f i x e d i na r k e r . r a t i f i c a t i on , 之 m y r e ma i n i n g o f f i c i a l s t e ps f o r t h e p r ot e c t i on of t h e s i t e Ac c es s i bi l i t y : c a n di da t e s e c t i ons i n r emo t e r e gi on s wh i c h c an wi t h t h e au t h or i t i es of t h e c oun t r y i n whi c h t h e GSSP i s l oc a t e d. on l y be vi s i t ed b y o r ga n i s i n g c os t l y e xp e di t i ons s h oul d n or ma l l y 4. 4 Ot he r r e qui r e me nt s be excl uded f r om t he s el ect i on. Fr e e a c c e s s f or r e s e a r c h t o t he t y pe - s e c t i on f o r a l l s t r a t i gr a ph e r s 6 Revi si on of a GSSP r e g a r dl es s o f t h ei r na t i on a l i t y. Whe n ma k i n g a f or ma l s ub mi s s i on t o I CS, t he c on c e r ne d Su b- A GSS P or GSSA c a n be ch a ng e d i t ' a s t r o ng de ma n d a r i s e s ou t o f c o mmi s s i on s ho ul d t r y t o obt a i n gua r an t e e s i f - or n t h e r e s p e c t i v e r e s e a r c h S u b s e q u e n t t o i t s e s t a b l i s h m e n t . B u t i n t h e m e a n t i m e i t w i l l a u t h or i t y c on c er n i n g f r e e a c c es s f o r r es e a r c h a n d p e r ma n en t l i v e a s t abl e po i n t o f r ef er e n c e. Nor ma l l y, t h i s s t a b i l i t y s h oul d b e pr ot ect i on of t he s i t e. , ma i nt ai n e d a nd t h e p r a c t i ca l v al u e of t he bou n da r y de ini f t i on t e s t e d f or a mi ni mum p er i o d of t en ye a r s . Re vi s i ons f or o t h e r r e a s ons s h oul d b e ma d e o nl y i n ex c e pt i o na l c i r cu ms t a n ce s , s uc h a s : 5 Pr ocedur e f or t he submi s si on of a GSSP I Th e p er ma n e nt de s t r uc t i on or i n a c c e s s i b i l i t y of a n e s t a bl i s hc d G SSP 5. 1 Edi t i ng of t he s ubmi s s i o n 2 a vi ol a t i on of a c c ep t e d s t r a t i g r a phi c pr i nc i p l es di s c ov e r e d on l y Su bmi s s i ons mu s t b e i n EnI gl i s h. I n o r de r t o p r ov i de a cl e a r pi c t u r e o f t h e qua l i t i es ot t h e p r op os e d GSSP c a nd i d a t e , t h e f o r ma l s u bmi s - s i on t o I CS or t o t h e c on c e r ne d Su b co mmi s s i on s hou l d gi v e t h e f ol - ] o wi ng i nf o r ma t i on : af ter t he r at i icat f i on of a GSSP. 7 Sel ect ed r ef er ences I name of - t he boundar y } 2 i ndi cat i on of t he exact l ocat i on ( coor di nat es) of t he s t r at ot ype- Th e 2 nd e di t i on oft h e I SG ( Sal v a dor , 1 9 94) c on t a i ns a c or np r eh e n- s i v e l i s t of p ub l i c a t i on s d e al i n g wi t h t he pr i nc i pl es a nd t ec h ni qu es of s ec t i on on a de t a i l e d t o po gr a ph i c n i a p o r a er i al ph ot og r a ph, i f t r at i gr apl - t v. The pr es ent l i s t of r efer ences i s t her ef or e l i mi t ed t o p os s i b l e a t a s c al e n o t l es s t h a n I: 50. 0 00: s p ap e r s pr ov i di n g f ur t he r i nf o r ma t i on on t h e p r i n ci p l e s un de r l yi n g 3 l o c a t i on on a d e t a i l e d g e ol ogi c ma p; t he s e Gu i del i ne s , a d di m I , s ome t i t l es n o t me nt i on e d i n t h e I SG. 4 d et a i l e d d e s c r i pt i on of t h e s t r at ot yp e - s e c t i on i n c l u di n g a l i t h ol og a nd ph ot os o t ' t h e s e c t i on, i n di c a t i ng t h e b e d i n whi c h t h e Bas s et t , M G, 1 990, I nt cr i i a t i onal ( ’ o ni n i i s si on on St r at i gr aphy, hi Br i ggs bo un da r y - po i n t i s de f i n e d a nd t h e k e y- l ev e l s f or al l p hy s i c al a nd D E G a nd Cr owt h er . P( ’ .eds. . Pal e obi ol ogy, a s ynt hes i s: Bl ackwel l , bi os t r a ig f r a phi c ma r k e r s } pp468-469. 5 mot i v a t i on f or t h e c h oi c e of t h e bou n da r y l ev e l a n d t h e s t r a t o- Baud, A, Maga r i t z, M. and Hol s er , W T. 1 989, Per mi an-Ir i as s i c of t he t y pe - s e c t i on , wi t h a di s c u s s i o n of 、 J a i l e d c a n di da t e s an d t h e i r I c t h ys : Ca r bon i s ot ope s t u di es : Geol ogi s che Run ds c hal - 1 . v. 7S, pp. 649- eas e of i nt er cont i nent al cor r el at i on: 6 a n y c ompa r i s on wi t h f o r me r u s a g e s h oul d be di s cu s s e d f ul l y} 7 di s cus si on of al l mar ker s us ed i n t he det er mi nat i on of t he 677 Cowi e. J W, 1 986, Gui del i nes f or boundar y s t r at ot y pes: Epi s odes , v. 9, pp. 78-82. Cowi e, J W, 1 990, Cdobal boundar y s t r at ot ypes , i n Br i ggs , D E G a nd Cr owt he r , P C, eds,Pal eol b i ol o gy. a s yn t he si s : Bl a ckwel l , pp. 471 -48 2. Cowi e. J W, 1 991 , Op eni ng a ddr e ss : I l e Cong r es I nt er nat i onal de St r a t i gr a - phi e et d e Gc ol ogi e du Car boni f e r e, Bei J i ng 1 987 v. 1, pp. 1 6-20, Nan . j i ng. has been us ed} Cowi e. J W. Zi ef ler , W, Bouc ot , A . 1 , Bas s e t t , M G, a nd Remane. J , 1 986 1 0 r e s ul t s ot al l v o t e s wi t hi n t h e Wor k i n g Gr o up a n d t h e Su bc om- Gui del i nes a nd s t at ut es of t he I nt er nat i ona l Commi s s i on on St r a t i gr aphy m ission . ( I CS) : Cour i er I } ot s ch l - i n&s i ns t . Sen ckenbe r g, v. 83, pp. I 一1 4. No t e : Wi t hi n t he s e pr o c e du r e s , onl y i t ems I , 6, 7, 9, 1 0, a n d t he Gr a dst ei n, F M, Agt cr her g, F R Br ower , J C, a nd Schwa r za che r , W S, eds mo t i va t i o n f o r t h e c ho i c e o f ' t h e bo un da r y- l e ve l a r e r el e va n t t o t he 1 98 5. Qu ant i t a t i ve s t r a t i gr aphy: Unes co. Par i s , Rei del , 598 pp. es t abl i shment ol ' a GSSA. Guex, J. 1 99 1 ,Bi oc hr onol ogi c al cor r el at i ons: Spr i nger , 252 pp Har l a nd, W B, 1 992. St r at i gr aphi c gui dan ce and r egul at i on: A cr i t i que Of Cut Fol l o wi ng a c c e p t a n c e of t h e s u bmi s s i o n wi t hi n t h es e Gui de - r ent t en denci es i n s t i at i gr aphi c codes a nd gui de s: Bul l e t i n oft he Geol og- l i ne s , t he Cha i r p er s on or t h e Se c r e t a r y of I CS wi l l a r r a n ge a v ot e b y i cal Soci et y of Amer i ca, v. 1 04. pp. ] 231 一123 5. t h e f ul l Commi s s i o n wi t h i n a p e r i o d of no mor e t h an 60 da ys . He db er g, H D, ed. , 1 976, I nt er na t i onal s t r a t i gr aphi c gUi de-- a gui de t o s t r at i - gr a phi c cl as s i f i cat i on, t e rmi nol ogy an d pr oc edur e: New Yor k, John 5. 2 Vot i ng pr o c e dur e Wi l ey an d Sons , 200 pp. Ha i l woo d, F A, 1 989, Ma gn et os t r at i gr aphy: Speci al Re por t oft he Geol ogi cal I n a c c or da n c e wi t h t h e I CS s t a t u t e s , a l l f or ma l vo t i ng mus t be c on- Soci et y. no. 1 9, 8 4 pp. d uc t e d by pos t , gi vi ng a d e a dl i n e o t ' 6 0 da y s f or t he r e c ei p t of vo t e s . Mann, K( )and La ne, H R, e ds . , 1 995, Gr a phi c Cor r el at i on: SEPM Soc. Vot i n g me mb e r s ( o f t h e Wor ki ng Gr o up , Su b c ommi s s i on or f ul l s e di m. Gcol . , Sp ec. Publ . No. 53, 263 pp McLar en一D . 1 , 1 977, The Si h - i r i an-De voni a n Boundar y Cor r i n ut t e e-a f i nal Co mmi s s i on) ma y vo t e ' YES' , ' NO' . or ' ABSTAI N' . The l a s t s t e p r e por t , i n Mar t i ns s on, A. e d. , The Si l ur i a n-Devoni an Boundar y: i n t h e s e l e c t i on of a ina f l ca n di da t e f o r a bo un da r y l ev e l a n d/ or i t St ut t gar t : I UGS Ser i e s A, n o. 5, pp. 1 -34. GSSP s h oul d al wa ys b e a vo t e on on e s i ngl e c a n di d a t e ( Cowi e et a l . - Odi n, G S, 1 992, New st r al oopc s f or t he Pal eogene, t he Cr et ac eous / Pal eo- 1 986) gen e, Foc ci r e / Ol i gocci i c and Pa l cogene [ Neogenc boun da r i es : Neue s I n ou t l i n e, t h i s pr o c e du r e i nc l ud e s t h e f ol l owi n g s t e ps : Jah r buch t ui - Geol ol l i C Und Pal a ont ogi e Ahhandl ungen v. 1 86, pp. 7 -20. I Su c c e s s i v e v ot i n g b y me mbe r s of t h e c o nc e r ne d Wor k i n g Gr oup Rema ne, J, 1 9 91 , Fr om bi os t r at i gr aph y t o bi o chr onol ogy: I ' i r r r e cor r el at i on l e a di ng t o t he c h oi c e o f a b oun da r y l e v el an d t he f i na l s e l e c t i o n b y I os s i l s :! I c Congr 0s I nt e r nat i onal de St r at i gr a phi e e t de GM ogi e do of a s i n gl e GSSP or GSSA c an di da t e. Car boni f er e, Bei i i ng,、.I .pp. 1 87 -20 0. b ou n da r y l ev e l : 8 i l l us t r a t i on o f i mpo r t a n t f os s i l s : 9 r es ul t s of r a di oi s o t o pi c da t i ng , i nd i c a t i n g cl e a r l y wh a t me t h od Se pt embet - 1996 81 Sa l v ador , A, e d. , 1 994, I nt er na t i ona l s t r at i gr a phi c gui de -a gui de t o s t r at i - gr a phi c cl as s i icat f i on, t er mi nol ogy and pr oce du r e, 2nd edi t i on: l UGS and t he Ge ol ogi ca l Soci e t y ofA mer i ca , 21 4 pp. Kl aus H Gohr ban dt , or i gi n al l y a Pa l e o ge n e s t r a t i gr a ph e r ha s l o ng e x pe r i e nc e as pe t r ol e um ge ol o gi s t i n s e v e r al c o mpani e s . He wa s Se c r e- t ar y Ge n er al o f I CS fr om 1 99 2 t o 1 9 95 , whi l e wor k i n g as a s e ni or r e s e ar c h g eo l o gi s t wi t h Ch ev r on Overseas Petrol eum. Pi r ge n Re mane t e ac he s pal e on t o l - og y and s t r at i gr a p扔,a t t he Uni v er - s i t y o f Ne uc hdt e l . Hi s s t r at i g r a ph i c r e s e ar c h i s mai nl y c on ce r ne d wi t h c al pi o ne l l i d b i o s t r at i gr a ph y o f t he Te t h y an u ppe r mos t Jur as s i c an d l owe r Cr e t a c e ou s , wi t h万e l d wor k i n t he Al ps a nd Me x i c o . He was S e cr e - t ar y Ge ne r al o f t h e I nt e r n at i o na l Co mmi s s i on o n St r a t i gr a p勺 ( I CS) 户o m 19 85 t o 1 9 9 2, a nd h as b e e n Ch ai r man o fI CS s i n ce 1 99 2. 摧蒸黯薰蒙鬓翼襄 臀i摹 燕薰蒸鬓 { 缨蒸 H Ri c ha r d La ne i s a gr a du at e o f t he Uni v e r s i t y o f I l l i n oi s an d a po s t - gr adu at e o f t he Un i v e r s i t y o f I owa . For mo s t o f h i s c ar ee r he ha s b e e n a pal ae on t ol ogi s t / s t r at i gr a ph er wi t h Amoco, at t he Resear ch Cent er i n Tul sa, Okl ahoma, and wi t h t he Wor l dwi de Ex pl or at i on Bus i ne s s an d Ex pl or at i o n a nd Pr odu c t i on Te c hno l og y Gr ou ps i n Hou s t o n, T e x as . Cur r e nt l y, he i s t he Di r e c t o r o f t h e Bi o s t r at i gr a phi c Su p por t a nd Devel opment Sect i on. Mi c hae l G Bas s e t t i s Ke e pe r o f Ge ol og y at t he Nat i o n al Mus e um o f Ol a f Mi c he l s e n ha s l o ng e x pe r i e nc e Wal es, UK. Hi s r es ear ch i nt er est s wor k i n t he Dani s h Geo l ogi c al Sur v e y . S i n c e 1 9 89 , he h as t au gh t s t r at i gr a ph y a s a pr o fe s s o r at t he Uni v e r s i t y o fA ar hu s , wi t h a s pe c i a l a r e mai nl y i n Ca mbr i a n- Si l ur i a n bi os t r at i gr a phy, j ac t e s e v ol u t i on a nd br ac hi o pod p勺l o ge n y , e s pe - c i al l y i n t h e UK an d Ba l t os c ana di a. He i s a pas t Se cr e t a r y Ge ne r al an d Fi r s t Vi c e Cha i r ma n o f t he I nt e r n a- t i o nal Co mmi s s s i o n on St r a t i gr a p妙 a nd r e c en t l y r e t i r e d as Ch ai r man o f t he Ge ol o gi c al So c i e t y o f Lon do n, Co mmi s s i o n o n St r at i gr aph y . John W Cowi e i s a r e t i r e dpr o f e s s or o f t he Uni v e r s i t y o f Br i s t o l , UK. He i s mai nl y a Ca mbr i a n s t r at i gr a ph er and has done much work on t he Pr e- c ambr i an -Cambr i an boun dar y. He wa s Cha i r ma n o f t he Pr e c am- b r i an -Ca mbr i a n Bo un da r y Wor k i n g Gr ou p o f I CS f or s ev e r al y e ar s . Fr om 1984 t o 1992 he was Chai r - man o f I CS a nd s i nc e t h e n , h as a ct i v e l yp a r t i c i pat e d i n t h e ac t i v i t i e s o fI CS Bu r e a u. Eni sodes. Vol. 19. no. 3 i n Me s o z o i c s t r at i gr a ph y , fr o m hi s i nt e r e s t i n s e q ue n c e s t r at i gr a ph y o f t he Ce noz oi c success i on i n t he Nort h Se a. He was Se cr et ar y o f t he Ju r a s s i c Su bc o mmi s s i o n o f I CS f o r t e n y e ar s a nd , s i n c e 19 95 , ha s b e e n Se c r e t ar y Ge ne r al o fI CS. Wang Nai we n i s a Me s o z oi c s t r a t i g- r a phe r wor k i ng wi t h o t h e r s i n Ti b e t . He i s a pr o f e s s or o f t he Ge ol og i c a l I n s t i t u t e o ft h e Chi n e s e Ac ad e myf or Ge ol ogi c al Sc i e nc e s i n Be i j i ng, Chi na. He was Second Vi ce- Chai r - man o fI CSfr o m 1 9 92 t o 19 96 .