Occurrence of nannoplankton observed in Early Pliocene samples from Zanclean stratotype of Capo Rossello, Sicily (Table I)

Calcareous nannoplankton biostratigraphy has been worked out in the eastern Mediterranean utilizing deep-sea sediments recovered from DSDP Leg 42A Sites 375 and 376. These two drill sites were located approximately 55 km west of Cyprus on the Florence Rise. Sediments, ranging in age from early Miocene (Helicosphaera ampliaperta Zone) through Holocene, contain sufficient age-diagnostic species to recognize essentially all of the lowlatitude nannoplankton zones described by Bukry, although regional, secondary marker species are needed to define some zonal boundaries. Reworked Cretaceous and Paleogene nannoplankton occur throughout the stratigraphic interval studied, but not in quantities large enough to mask indigenous species. Sedimentation rates at Sites 375 and 376 were highest in the late Miocene and late Pleistocene. Open-marine, warm-water species of discoasters are present in significant numbers throughout the Miocene and Pliocene. Earliest Pliocene assemblages contain numerous specimens of ceratoliths. Nannoplankton in post-Messinian sediments at the drill sites and the Zanclean stratotype at Capo Rossello, Sicily, indicate that the base of the Amaurolithus tricorniculatus Zone (base of Triquetrorhabdulus rugosus Subzone) corresponds with the Miocene-Pliocene boundary.本研究针对东地中海区域，依托深海钻探计划（Deep Sea Drilling Project, DSDP）第42A航次375与376站位获取的深海沉积物，开展了钙质超微浮游生物（calcareous nannoplankton）生物地层学研究。上述两个钻探站位位于塞浦路斯以西约55公里的佛罗伦萨海隆（Florence Rise）之上。 沉积物的形成时代从中新世早期（Helicosphaera ampliaperta带）延伸至全新世，其中含有充足的年代标志种，可识别出Bukry所描述的绝大多数低纬度超微浮游生物组合带，不过部分组合带的边界需要借助区域性次生标志种加以界定。 研究层位全程可见再沉积的白垩纪与古近纪超微浮游生物，但其含量未达到足以掩盖土著种的程度。 375与376站位的沉积速率在晚中新世和晚更新世达到峰值。 广海性暖水盘星藻（discoasters）类群在整个中新世与上新世地层中均大量产出。 最早的上新世组合中含有大量角石藻（ceratoliths）化石标本。 对本钻探站位墨西拿期（Messinian）后沉积物以及西西里岛卡波罗塞洛（Capo Rossello）的赞克尔阶（Zanclean）层型剖面（stratotype）中的超微浮游生物进行分析后可知，三刺拟棒球石（Amaurolithus tricorniculatus）带的底界（即皱饰三角杆石（Triquetrorhabdulus rugosus）亚带的底界）与中新世-上新世界线完全吻合。