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.