勿 Isabella P rem oli Silva and D G raham Jenkins Wv1%,ecision on the E ocene-O ligocene boundary stratotype

The G lobal Stratotyp e Section and Pointfor the E ocene- G roup on the Eocene-O ligocene B oundary and (3) close collabora- tion with both IGCP Project 196 (Calibration of the Phanerozoic O ligocene boundary has been agreed upon. The new T im e Scale) and the Subcom m ission on G eochronology (G S O din, boundary is defi ned in the M assignano section near C hairm an, France). A ncona, Italy A n internation al m eeting of the Subcom m ission on Paleogene Stratigraphy w as held in A ncona, Italy, in 1987 to consider the E ocene-O ligocene boundary. T he m eeting w as attended by 38 par- ticipants, and 18 papers w ere published in a special volum e know n as the A ncona V olum e (Prem oli Silva and others, 1988). The partic- In tro d u ctio n ipants concluded that the M assignano, section, about 10 km southeast of A ncona, w as the best available stratotype for the E ocene-O ligo- T he first coordinated, worldwide study of the Eocene-Oligocene cene boundary. Subsequently, the E ocene-O ligocene w orking boundary w as undertaken by the International G eological C orrela- group, having been provided w ith the necessary details of the B ath tion Program m e's (IG C P ) Project 174 (1980- 1985), led by C harles section in B arbados and the M assignano section in Italy, concluded Pom erol and Isabella Prem oli Silva. A t the final m eeting of IG C P that the M assignano section w as the best choice for the Eocene- Project 174 in P aris in 1985, the project's participants decided to O ligocene boundary stratotype and G lobal Stratotype Section and publish a volum e of the papers presented at the m eeting (P om erol Point (G SS P). Ten of the m em bers w ere in favour, one w as unde- and Prem oli Silva, 1986). Follow ing this initial w ork, the Subcom - cided, and one did not reply. m ission on Paleogene Stratigraphy continued the search for a suit- Prior to the Internationa l G eological C ongress in W ashington able boundary stratotype. This involved (1) a w orldw ide postal sur- D C in 1989, the 20 voting m em bers of the Subcom m ission on Pale- vey follow ed by (2) the establishm ent of the international W orking ogene Stratigraphy w ere provided w ith copies of the A ncona V ol-

羹攀豁 啊 澎罕弥 悉珊

A N C O N A ‘ 事 0 如 I j ．刀曲1 曰 内 斌澎 ．曰‘二 ．．L 二 J ．． 数 0肠 万奋云七w 麟﹃一 法襄翼撼 1办 攒 从 d ei C oM ，Sc匆hipd T '4} 二少岔万 尸时竺n口v。 F igure L - T he 撇介 A}d抽 志 - 4吵 isd ,七吧Pm . 帐伪 } e m M assignano section, ，： 弓 粗 ． ～ ＿ located in a quarry 蒸 "}-A d ,S P w } 0 知 1．吕‘． 神为弧 ，： 口 长 广石h' ab o u t 10 km so u th - G 日映旧10 占 . . } ' V - east ofA ncona, Italy, 乍石蕊）卜群 产0 把 ‘口0 扭m 巍 二 at latitude 43 32 '13 ' 诊吮 N and longitude 乙口 扣 赢百 鼓I- "V O 伪y- 乐 Fig. 1. The M assignano section and its geographic location. 13 '35 '36 "E . Th e 叮 ． 氮‘后蒸 n u m b ers in th e }糕 A6b}豁 降 p hotograp h of t h e section are d ista n ces in m etres a bo ve th e base of t he m easured sectio n. T h e E o cen e- O ligocene boundary G S S P is a t 19 m . Contours on the m ap a re in m etres.

A b b re via tion s E E o cen e 0 O ligocene. Taken 了}-onz C occioni ando thers (1988).

即 isodes, VoL 16, no. 3 38 0

0 8 F igure 2.- Calcare- － 8 二 M A S S IG N A N O 6 Z O N E S ous nannofossil and d 5 ＾ 尸 V 匡 1 p lankton icf oram in- 5 山 S E C T IO N － 匡1 ︵ 卜 的一 C A L C A R E O U S N A N N O F O S S IL S 比 卜 匡 V 1 匡 8 iferal events in th e 口 V 卜 丫 6 A N D 工 山 －J N 钾 M assignano section 工 芝 V 0 n ︶ ＾ 5 O 卜 尸 一 P L A N K T O N IC F O R A M IN IF E R A 0 V ． d ︶ 口 ︵护 plotted a gainst 匡 2 5 0 － S 2 6 N 0 之 0 0 习 9 山 chrono-, h tho-, O i － 山 0 uJ 1 芝 工 6 S 5 －J －J －J 1 N V 尸匡 m agneto- and 山 O 一 山 l ︶D O 5 －J ． d U d 心 i O 0︵兮 d H 1 2 乏 H V 芝 N O biostratigrap 匆． 一 V － 口 山 匡 V 8 0 匡 l 之 O 0 V i O 哎 0 V 义 6 M A IN E V E N T S l V －J 山 A b b revia tio n s 山 －J n S 0 S 一 O 5 芝 1 芝 0 尸8 口 －J 口 ︶ 山 N 1, N 2 norm al 2 C P R, R 1, R 2 reverse 山 ＾ 0 －J 黑 1 6 b N P nan no/ossil 匡 A cm e E ob ruta 0 ︸ 之口n e V V 潍一 P 1 8 ｝ "G .“tap uriensis 0 山 C P calcareo us － uJ －J 匡 2 0 nannofossil zo n e 0 山 13RI 2 P p lanktonic － N P H a n tke n in id a e O }=-L =F4 丁 ／ T foram inifer a l 2 1 一「 ＼ T cu n ia len si.s ：口n e 13 V C P c o c o a e 门S IS － 1 6 a M odifi ed from －J P 1 7 O C occio n i a n d oth ers V (1988). O S 1 5 ＊ 阵 千 ＊ ｝13 几 一厂 C . in fl a ta ba rb a die nsis ＊ ＊ 丁 炭县 sa妇anensis 山 ＊ ＊ ︺ 爪 u一.uIU. fine rubeaxC h e ri． 2 山 限﹃ 冲 山 卜 雕 肚 0 喊 畔 土 C． 1 0 15 N 丁 C．lazz a rii 0 限﹃ －J 喊 ﹂ P 1 6 k ing ii 卜 嚣 山 ＜ N P ｝C P 0 1 5 R 9 /2 0 11 5 b 山 勇＊ －L T． 一 cu n ia len sis 比 ＊ ＊ 6 N 下 C． 哎 ＊ re tic ula tu m ， ﹄ ‘ 6 R

喊 － 1 哎 下 －J A 5 匡 0 山 丁不pom eroli 匡1 ＜ 山2 G . s em fin vo luta 考一 下 0 0 H 一S N . true m p yj 5 0－ 止 0 ／ /. re cu rvus 山 工 ＼P . co sta ta

N P ｝q P P 1 5 1 8 11 5 a

0

G re e nis h一g rey 昏要 月 G reenish-qrev B io tite -b ea rin g I r- 阵 曰 ． ～ ‘ ． 小 口匕 First a ppe ara nce m a d 1- T 三1二三i c a ic a re o u s m a r i lay e r 一厂 Last ap pea ra nc e — A c m e

um e and w ere asked to vote on the suitability of the M assignano sec- tion. Fift een voted for it, none voted against it, one abstained, and Boundary stratotype (G SSP) fo ur did no t v ote. In 1992, the I n t er national C om m ission on Stratigraphy voted in 瓜。M assignano section is located。。the Adriatic coast of Italy in favour of the M assignano section, and this w as ratified by the Inter- the M onte C onero area. It is an abandoned quarry on the east side of national U nion of G eological Sciences at the international G eologi- the A ncona-Sirolo road near the village of M assignano (figure 1). O n cal C ongress in K yoto in 1992. the geological m ap of Italy (F. 118, A ncona), the section is located at latitude'43032113"N and longitude 13'35'36"E. The quariy face is up to 4 m etres high and does not constitute any senous hazard to vis-

Septem ber 1993 3 8 1

itors. It is part oft he M onte C onero protected area, and is M A S S IG N A N O C O N T E S S A thereby preserved from dam age. T he exposed section, from N occhi a nd others (1986) m arked by a m etal plate, is show n in figure 1, w here the V .G .P . L a titu d e G SSP is draw n in the photograph at 19 m above the base (after rem oval of tectonic rotation) P O L A R IT Y P O L A R IT Y A N O M A L Y of the sectio n. m I . } .，甲甲 } i . 甲 .一. .一. .甲 . . I 13 N The M as s ig n ano section, w hich covers the late 1 7 5 Eocene to early O ligocene, is 23 m thick and consists of 2 0 reddish and greenish grey m arls and calcareous m arls (fig- ure 2). T he low er part is in the Scaglia V ariegata Form a- tion (12.3 in), and above this is the Scaglia C inerea. For- 1 7 0 1 3 R m ation (10.7 m ). The sedim ents of the M assignano sec- 1 5 tion are entirely m arine, and no evidence exists of any hia- tus or structural com plexity in the sequence. The G SSP is 16 5 at the base ofa greenish grey m arl bed 0.5 m thick. A t this 1 5 N level, both the planktonic foram inifera H antkenina and 10 Cribrohantkenina, E ocene genera of the H antkeninidae, 1 5 G becom e extinct (figure 2). T he stratigraphic ranges of 1 6 0 planktonic foram inifera and calcareous nannofossils have been detailed by C occioni and others (1988), and of the 1 6 N benthonic foram inifera. by P arisi and C occioni (1988). T he sequence has been correlated w ith the established cal- 15m5 1 6 R careous nannofossil zones N P21 of M artini (1971) and 1 7 N C P 16a of O kada and B ukry (1980), as w ell as w ith the -9 0 0 0 0 +90 0 planktonic foram iniferal boundary of zones P I 7 and P I 8 of B low (1969) and B erggren and others (1985). 鑫留 norm al 馥撇爹intermediate ［二二 reverse The m agnetostratigraphy of the M assignano s e ction (tw o c om p on en ts) has been docum ented by B ice and M ontanan (1988), w ho hav e b een able to correlate it w ith the C o nte ssa sec tion in F igure 3.- M assignano section s virtual geom agneticp ole (V G .P ) latitude Gubbio, northern Italy (figure 3). The M assignano section correlated w ith the C ontessa H igh way III section (N occhi and others, 1986). lies w ithin m agnetic polarity reversal 13R . Radiom etric ages (K -Ar and 40Ar-19A r ） have been A b b revia tio n s obtained from biotites (M ontanan and others, 1985; M on- N n orm al R re verse G interm ediate. tanari and others, 1988; and O din and others, 1988b). T he date of 34.6 + 0.3 M a at 14.7 m above the base of the sec- Taken from B ice and M on tanari (1988). tion indicates that the age of the G SSP at 19 m is younger and is estim ated to be 34 M a (figure 4). A dditional published data on the M a s si gnano section include sedim entological and geochernical data (O din and others, 1988a), and strontium 工 isotope data (C apo and D ePaolo, 1988). Fur- O C O N T E S S A M A S S IG N A N O O A N O M Z o n e S 下E P the r d etails c an be fou nd in the A nco na V o l- D－ S E C T IO N S E C T IO N 山 -A L 丫 C ID H E A T IN G ZoPne um e (Prem oli Silva and others, 1988). － G U B B IO A N C O N A 田 N ＊ (35.4 士0.4) 山 0 1 6 b 0 13 i s C o n clu sion 0 －J1 0 T he Oligocene-Eocene GSSP in the Massi- gnano section is w ithin calcareous nanDOfOS- 1 6 a sil zones N P21 and C P 16a and w ithin m ag- 17 netic polarity reversal 13111. It coincides w ith ＊ 3 4 .6 :t 0 .3 34.1 G ood plateau the planktonic foram iniferal boundary of zones P 17 and P 18. T he radiom etric age is ＊ 3 4 .3 :t 0 .2 34.9 G ood plateau estim ated to be 34 M a. 1 6 山 1 5 1 5 b N 山 0 F igure 4.- Stratigraphic levels and radio- 0 (36.0 士1.0) ＊ 3 5 .5 士 0 .3 (36.6) N o platea u 山 ？｝＊ m etric dating of volcaniclastic biotites (level C Q -ETT) (level C O -ETT ) (asterisks) in the Contessa quarries near 1 6 G ubbio and at the M assignano section. B old num bers are少)-om O din and others (1988), and the resta re from M ontanari and oth ers (198习and M ontanari an d ＊ 3 6 .4 士 0 .3 1 5 others (1988). 1 7 1 5 a

A b b revia tio n s C P calcareous nannofossilz one P planktonic foram iniferal zone CQ -ETT sam plefrom the Contessa section 1 8 14 Taken from O din and o thers (1988).

E pisodes, Vol. 16, no. 3 3 8 2

O din, G S, Clauser, S, and Renard, M , 1988a, Sedim entological and geo- A cknow ledgm ents chem ical data on the Eocene-O ligocene boundary at M assignano (Apen- nines, Italy), in Prem oli Silva, 1, and others, eds., The E ocene-Oligocene boundary in the M arche-U m bria Basin (Italy): A ncona, Italy, Interria- W e thank all members of the W orking Group Boundary。。the tional U nion of G eological Sciences, Com m ission on Stratigraphy, pp. E ocene-O ligocene B oundary and the voting m em bers of both the 17 5 - 1 86 . Subcom m ission on Palcogene Stratigraphy and the International O din, G S, G uise, P, Rex, D C , and K reuzer, H , 1988b, K-A rand 39A r/4OA r C om m ission on Stratigraphy, as w ell as the International U nion of geochronology of late Eocene biolites from the northeastern Apennines, G eological Sciences. W e are particularly indebted to the contribu- in Prem oli Silva, 1, and others, eds., The Eocene-O ligocene boundary in tors to the A ncona V olum e. V alerie D eisler typed this m anuscript, the M arche-U m bria Basin (Italy): A ncona, Italy, International U nion of L in N orton redraft ed the figures from the A ncona V olum e, and G eological Sciences, Com mission on Stratigraphy, pp. 239-245. Jud ith Jen kin s check ed th e article. O kada, H , and Bukry, D , 1980, Supplem entary m odification and introduction of code num bers to the low latitude coccolith biostratigraphic zonation (Bukry, 1973, 1975): M arine M icropaleontology, v. 5, pp. 321-325. Parisi, G , and Coccioni, R , 1988, D eep-w ater benthic foram inifera at the R efe re n c es Eocene-O ligocene boundary in the M assignano section (A ncona, Italy), in Prem oli Silva, 1, and others, eds., The Eocene-O ligocene boundary in Berggren, W A , K ent, D V , and Flynn, I J, 1985, Paleogene geochronology the M arche-U m bria Basin (Italy): A ncona, Italy, International U nion of and chronostratigraphy, part 2 of Jurassic to Paleogene, in Snelling, N J, G eological Sciences, C om m ission on Stratigraphy, pp. 97- 109. ed., The chronology of the geological record: Geological Society of Lon- Pom erol, C , and Prem oli Silv a, 1, eds., 1986 , T erm inal E ocene even ts: E lse- don, M em oir 10, pp. 141-186. vier Science Publishers, D evelopm ents in Palaeontology and Stratigra- Bice, D M , and M ontanari, A , 1988, M agnetic stratigraphy of the M assi- phy 9, 414 pp. gnano section across the Eocene-O ligocene boundary, in Prem oli Silva, Prem oli Silva, 1, C occioni, R, and M ontanari, A , eds., 1988, The Eo- 1, and others, eds., The Eocene-O ligocene boundary in the M arche- cene-O ligocene boundary in the M arche-U m bria B asin (Italy): A ncona, U m bria Basin (Italy): A ncona, Italy, International U nion of G eological Italy, International U nion of G eological Sciences, Com m ission on Sciences, Com m ission on Stratigraphy, pp. 111-117. Stratigraphy, 268 pp．口 Blow , W H , 1969, L ate m iddle Eocene to R ecent planktonic foram iniferal biostratigraphy, in Bronnim ann, R , and R enz, H H , eds., International Conference on Planktonic M icrofossils; Is t, G eneva, 1967, Proceedings: Leiden, E J Brill, v. ],pp. 199-4 2 1. D r I P rem oli Silva is P rofessor of C apo, R C , andD cPaolo, D J, 1988, Sr isotopic analysis ofm arine carbonates from the M assignano section across the Eocene-Oligocene boundary, in M icropaleontology in the D epartm ent Prem oli Silva, 1, and others, eds., The Eocene-O ligocene boundary in the of E arth Sciences, U niversity of M ilan, M arche-U m bria B asin (Italy): A ncona, Italy, International U nion of Italy, and isp ast Chairm an of t he Sub- G eological Sciences, Com m ission on Stratigraphy, pp. 189-192. com m ission on Paleogene Stratig - C occioni, R , M onaco, P, M onechi, S, N occhi, M , and Parisi, G , 1988, Bio- rap 柳．H er research includes detailed stratigraphy of the Eocene-O ligocene boundary at M assignano (A ncona, biostratigrap hic studies of C retaceous Italy), in Prem oli Silva, 1, and others, eds., The Eocene-O ligocene bound- to M iocene p lanktonic foram inifers ary in the M arche-U m bria B asin (Italy): A ncona, Italy, International 加 in land and deep -sea deposits. She U nion of G eological Sciences, C om m ission on Stratigraphy, pp. 59-80. 黔 M artini, E, 1971, Standard Tertiary and Q uaternary calcareous nannoplank- has participated in six cruises for the ton zonation, in Farinacci, A , ed., Planktonic Conference, 2nd, R om a, D eep Sea D n lling P roject and O cean 一 1970; Proceedings: Rom e, Edizioni Tecnoscienza, v. 2, pp. 739-785. D rilling P rogram . 卜 M ontanari, A , D eino, A L , D rake, R E, Turrin, B D , D ePaolo, D J, O din, G S, Curtis, G H , A lvarez, W , and B ice, D M , 1988, Radioisotopic dating of the Eocene-O ligocene boundary in the pelagic sequence ofn ortheastern D r D G raham Jenkins is an H onorary Apennines, in Prem oli Silva, 1, and others, eds., The Eocene-O ligocene R esearch A ssociate in the D ep artm ent boundary in the M arche-U m bria Basin (Italy): A ncona, Italy, lntem a- tional Union of G eological Sciences, Com m ission on Stratigraphy, pp. of G eology, N a tional M useum of 1 9 5- 2 0 8 . W ales (C ardif , W ales, UK C F ] 3N P ) M ontanari, A , Drake, R E , B ice, D M , A lvarez, W , C urtis, G H , T urrin, B D , and is C hairm an of the Subcom m ission and D ePaolo, D J, 1985, Radiom etric tim e scale for the upper Eocene and on Paleogene Stratigrap彻．H is re- O ligocene based on K -A r and R b-Sr dating of volcanic biotnes from the search concentrates m ainly on the pelagic sequence of G ubbio, Italy: G eology, v. 13, pp. 596-599 w orldw ide distribution of C enozoic N occhi, M , Parisi, G ., M onaco, P, M onechi, S, M adile, M , N apoleone, G , planktonic foram inifera and their use Ripepe, M , Orlando, M , Prem oli Silva, 1, and Bice, D M , 1986, The in correlation, evolution, and paleo- Eocene-O ligocene boundary in the U m brian pelagic sequences, Italy, in ecology. H e has participated in three P om erol, C , and P rem oli S ilva, 1, eds ，T erm inal E ocene events: E lsevier Science Publishers, Developm ents in Palaeontology and Stratigraphy 9, D eep Sea D rilling P roject cruises. pp. 25一0.

Septem ber 1993