菲律宾海盆东北部晚始新世以来放射虫及其古海洋学意义

研究了菲律宾海盆东北部“大洋钻探工程”１２５航次７８２Ａ孔晚始新世以来的放射虫化石。根据Ｓａｎｆｉｌｉｐｐｏ等１９８５年的分带，将研究区自下而上划分为１０个带。讨论了始新世与渐新世、渐新世与中新世、中中新世与晚中新世、中新世与上新世以及上新世与第四纪的界线。研究区存在两个沉积间断，分别位于晚渐新世与早中新世晚期之间和中中新世与晚中新世之间。研究区第四纪放射虫化石仍以暖水分子为主，冷水分子分布较浅。依据放射虫化石分异度曲线得出，晚第三纪以来本区存在５个相对暖水期和５个相对较凉期，渐新世时处于冷水期，这与钙质超微化石复合分异度和碳酸钙含量曲线的变化是一致的。晚渐新世与早中新世晚期之间的沉积间断是由于中新世南极冰盖扩展造成大洋底层洋流活动加剧而形成的。

LATE EOCENE QUATERNARY RADIOLARIA FROM THE NORTHEAST OF THE PHILIPPINE SEA AND THEIR SIGNIFICANCE FOR PALEOCEANOGRAPHY

The study area named Bonin basin is located in the northeast of the Philippine sea.This paper addresses the radiolaria stratigraphy of Late Eocene Quaternary sediments.The materials were collected from 782A Hole,Ocean Drilling Program,Leg125.Based on the biozonation by Sanfilippo et al.in 1985, ten fossil zones are divided. Zones Stichocorys wolffii Lychnocanoma elongata and Didymocyrtis antepenultima are missing.The two hiatuses are detected as follows: between Late Oligocene/late Early Miocene,Middle Miocene/Late Miocene.The five boundaries are as follows:Eocene/Oligocene,Oligocene/Miocene,Middle Miocene/Late Miocene,Miocene/Pliocene and Tertiary/Quaternary.Most of Quaternary radiolarias in this studied area are warm water species.In this area,fossil abundance and diversity are lower than those in the tropical latitude.Several cold water species are paragenetic with them, and fossil abundance is large,so in the studied middle latitude area they maybe distribute in shallower water.From the change of radiolaria simple diversity,we can identify five relative warmer water stages and five relative colder water stages from Miocene to Quaternary.Oligocene is a colder water stage.The result is in accord with the change of nannofossil complex diversity and the content of calcium carbonate in hole 782A.The hiatus between Late Oligocene/Early Miocene may be formed by the violent scouring of bottom currents.It may be caused by the extension of the Antarctic ice cap in Miocene.