Silicoflagellate abundance in ODP Holes 183-1138A and 183-1140A@en

The biostratigraphic distribution and abundance of lower Oligocene and Miocene to Pleistocene silicoflagellates are documented from Ocean Drilling Program Leg 183 Holes 1138A and 1140A, on the Kerguelen Plateau. The Distephanus speculum speculum forma pseudofibula plexus is found in the upper Miocene in Hole 1138A, but other important biostratigraphic markers are not available. Diversity and abundance of silicoflagellates vary considerably in Hole 1138A, with silicoflagellates more abundant in the Pliocene and Pleistocene and some intervals of the Miocene barren of silicoflagellates or containing only limited numbers of specimens. The silicoflagellates of Hole 1140A include a new skeletal morphology, described here as Distephanus speculum speculum forma cylindrus. Silicoflagellates were generally abundant throughout the lower and middle Miocene in Hole 1140A.本数据集系统记录了凯尔盖朗高原（Kerguelen Plateau）上大洋钻探计划（Ocean Drilling Program，ODP）第183航次1138A号与1140A号钻孔中，渐新统下部、中新世至更新世硅鞭藻（silicoflagellates）的生物地层分布与丰度特征。1138A号钻孔的上中新统地层中发现了Distephanus speculum speculum forma pseudofibula plexus这一硅鞭藻变型，但其余重要生物地层标志类群较为匮乏。1138A号钻孔内硅鞭藻的多样性与丰度差异显著：上新统与更新统中的硅鞭藻丰度更高，而中新世的部分层位无硅鞭藻分布，或仅含少量标本。1140A号钻孔的硅鞭藻类群包含一种新的骨骼形态，本文将其描述为Distephanus speculum speculum forma cylindrus。1140A号钻孔的下中新统至中中新统整体硅鞭藻丰度较高。