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2008040281加 勒 比 海 上 新 世 海 洋 的 流 通 和 营 养 水 平 的 变化 — 来 自 底 栖 有 孔 虫 聚 集 比 率 的 证 据 =Changes in circulation and trophic levels in thePliocene Caribbean Sea; evidence from benthicforaminifer accumulation rates. ( 英 文 ). BornmalmL; Widmark J G V. Journal of ForaminiferalResearch, 1999, 29(3): 209-221Changes in benthic foraminifer faunasthroughout the late Neogene (about 5.8-1.8 Ma)were analyzed in DSDP Hole 502A (CaribbeanSea) to determine whether the development ofthe Isthmus of Panama and resulting changes inbottom-water circulation affected the benthicforaminifer community. Benthic foraminiferaccumulation rates (BFAR) of the 11 mostabundant and presumably also ecologically significantspecies revealed three intervals of distinctfaunal developments: Interval 1 (prior to4.65 Ma) exhibits a fluctuating pattern in thebenthic foraminifer fauna with an increase ofEpistominella exigua between 5.7 and 5.35 Ma,except at about 5.4 Ma. This variation of E. exiguamay indicate a period of increased verticalflux of organic (phytodetritial) matter to the seafloorat the base of the sequence. Also towardsthe upper part of Interval 1, E. exigua showsperiods of higher abundance, which could berelated to higher vertical flux of phytodetritus tothe seafloor. Interval 2 (4.65 to 3.9 Ma) ismarked by a gradual increase of C. wuellerstorfiand Oridorsalis umbonatus, and decrease of Nuttallidesumbonifera with periods of higher abundanceof E. exigua. This faunal change can berelated to alternations of sudden phyto-detritusinputs and increased circulation within the CaribbeanSea that resulted from the progressiveemergence of the Panamanian landbridge changingthe Caribbean Sea from a broad oceanicseaway into a marginal sea. The restricted surface-waterflow over the Isthmus of Panamaprobably enhanced northward transport of warm,high-salinity waters into the high latitudes viathe Gulf Stream and thus stimulated the totalproduction of North Atlantic Deep Water(NADW) leading to an increased inflow of UpperNorth Atlantic Deep Water (UNADW) intothe Caribbean Sea. The increased bottom-wateractivity in the Caribbean may have favored C.wuellerstorfi, which has been found to prefer anelevated suspension feeding position above thesediment surface. Intensified bottom-water circulationwould allow more water to pass andthus provide more available food for this particularspecies. Interval 3 (about 3.9 to 1.8 Ma) beganwith a striking decrease of C. wuellerstorficoeval with a rapid increase of N. umbonifera,which became the dominating species. This mayhave been a response to a declined velocity ofthe bottom-water currents in the Caribbean,probably caused by less inflow of bottom watersfrom the North Atlantic. The organic flux intothe area may have been similar to Interval 2, butlower bottom-water current velocities may havefavored the more oligotrophic species N. umboniferarelative to C. wuellerstorfi. The peak abundanceof E. exigua between about 3.55 and 3.45,and at 3.4-3.35 Ma may be a result of strong butinterrupted inputs of phyto-detritus into the ColombiaBasin. Also in the upper part of the intervalparticularly between approximately 2.5 and2.2 Ma the abundance of E. exigua exhibit increasedvalues. At about 3.0 Ma N. umboniferashows a drastic decrease and coeval recovery ofC. wuellerstorfi, O. umbonatus, and Pyrgo murrhina.This faunal change could be attributableto (a) mixing between the base of nutrient-richAntarctic Intermediate Water (AAIW) and theupper layer of Upper North Atlantic Deep Water(UNADW), and/or (b) nutrient-rich local riveroutflow (e.g. from the Rio Magdalena) togetherwith, at least periodically, (c) increased bottomwatercurrents that favored the normally elevatedand suspension feeding C. wuellerstorfi. Theshort term alternation in the benthic foraminiferabundance, i.e. the instant recovery of N. umboniferain the lower part of the interval, may indicatean amelioration of deep-water conditions,which may have been associated with a slowerinflow of bottom water into the Caribbean Sea.Moreover, the increased average benthic delta 13C value during the upper part of Interval 3 mayalso be a result of a better bottom-water ventilationin the Colombia Basin linked to the onset ofthe modern deep-water circulation, which mostlikely is related to periodically increased inflowof UNADW into the Caribbean Sea.2008040282意 大 利 西 北 维 琴 察 市 威 尼 托 区 始 新 统 中 上 部界 线 的 Alveolinids = Alveolinids at the Middle-Upper Eocene boundary in northeastern Italy(Veneto, Colli Berici, Vicenza). ( 英 文 ). Bassi D;Broglio-Loriga C. Journal of Foraminiferal Research,1999, 29(3): 222-235 4 图 版 .The Middle and Upper Eocene successions ofthe Colli Berici (Veneto, northeastern Italy) havebeen studied since the beginning of the nineteenthcentury in order to describe the large, benthicforaminiferal-rich assemblages. The Bartonian-Priabonianexposures in the southeasternpart of the Colli Berici (Mossano) have been theproposed "parastratotype" for the Priabonianstage. The classic Mossano section and two additionalsections outcropping in this area, allspanning the Calcari Nummulitici (Middle Eocene)-Marnedi Priabona (Late Eocene) formations,provided us with new biostratigraphic dataabout two alveolinid species. Borelis vonderschmitti(Schweighauser) has so far been re-91