Cenozoic radiolaria in the western North Atlantic

Eight Cenozoic radiolarian zones were recognized in samples from two holes at Site 603, drilled on the lower continental rise off North America during Leg 93 of the Deep Sea Drilling Project. Paleocene to early Eocene radiolarian zones (Bekoma bidartensis, Buryella clinata, and Phormocyrtis striata striata zones) and early to late Miocene radiolarian zones (Calocycletta costata, Dorcadospyris alata, Diartus petterssoni, and Didymocyrtis antepenultima zones) were recognized in sediments from Holes 603 and 603B. In addition, a new Paleocene Bekoma campechensis radiolarian Zone is defined by the interval between the first morphotypic appearance of B. campechensis and the B. campechensis-B. bidartensis evolutionary transition. This zone is immediately below the B. bidartensis Zone of Foreman (1973), and has previously been discussed as a Paleocene "unnamed zone" by other investigators. A hiatus between Neogene and Paleogene sequences was also recognized in the radiolarian faunas.

在北美洲大陆坡下方进行的深海钻探计划第93航次中，于603号地点的两个钻孔样本中识别出了八个新生代放射虫带。从603号和603B号钻孔的沉积物中，可辨认出古新世至早渐新世的放射虫带（包括Bekoma bidartensis、Buryella clinata和Phormocyrtis striata striata带）以及早中新世至晚中新世的放射虫带（包括Calocycletta costata、Dorcadospyris alata、Diartus petterssoni和Didymocyrtis antepenultima带）。此外，通过Bekoma campechensis首次形态型出现与Bekoma campechensis-Bekoma bidartensis演化过渡之间的时间间隔，定义了一个新的古新世Bekoma campechensis放射虫带。该带位于Foreman（1973）的Bekoma bidartensis带之下，此前已被其他研究者称为古新世的“未命名带”。同时，在放射虫群中，也识别出了中生界与古生界的序列间断。