Distribution of foraminifera, pre-Pliocene foraminifera and macrofossil debris in sediment core CRP-2 (Table 1)

The stratigraphic distribution, assemblage content, paleoecology and age of foraminifera recovered in fourteen of sixteen samples from the 5.63 m thick CRP-2 (Lithostratigraphic Unit 2.2) are discussed. LSU 2.2 comprises four discrete lithologic beds. The upward sequence is informally referred to as the lower sand bed, diamicton bed, middle sand bed, and upper sand bed and it is surmised that these four units are closely related in time. The lower sand bed (~1.5m), which overlies lower Miocene sediments and from which it is separated by the Ross Sea Unconformity, contains traces of recycled Miocene diatoms but is otherwise barren of biogenic material. The diamicton bed (~2.42 m) contains 21 species of benthic foraminifera, with assemblages consistently dominated by Cassidulinoides porrectus, Ammoelphidiella antarctica, Rosalina cf. globularis, Cibicides refulgens, and Ehrenbergina glabra. The overlying middle sand bed (~1.9 m) contains 13 species. with C. porrectus and E. glabra dominant and A. antarctica less common than in the underlying diamicton bed. The upper sand bed (~0.46 m) contains four species and very few tests. The diamicton bed and middle sand bed assemblages are considered to be near in situ thanatocoenoses; and sediments interpreted as marine in origin but influenced by hyposaline waters and nearby ice. Planktic taxa are absent, perhaps indicating the presence of tidewater glaciers, sea ice and/or hyposaline surface waters. The small assemblage in the upper sand bed is more problematic and may be recycled. On the basis of foraminifera in the diamicton and middle sand beds. LSU 2.2 is assigned to the Pliocene. The overlying diamicton in LSU 2.1 contains abundant Quaternary foraminifera.本文讨论了取自5.63米厚CRP-2钻孔岩石地层单元2.2（Lithostratigraphic Unit 2.2）的16个样品中14个样品所获得的有孔虫（foraminifera）的地层分布、组合组成、古生态特征及形成年代。岩石地层单元2.2由4个独立的岩性地层组成，其向上序列被非正式命名为下砂层、混杂岩层、中砂层及上砂层，推测这四个地层单元在时间上紧密相关。下砂层（厚度约1.5米）覆于下中新统沉积物之上，二者以罗斯海不整合面（Ross Sea Unconformity）分隔，该层仅含再旋回中新统硅藻痕迹，其余均无生物成因物质。混杂岩层（厚度约2.42米）含21种底栖有孔虫（benthic foraminifera），其组合始终以卷曲拟扣球虫（Cassidulinoides porrectus）、南极小箭头虫（Ammoelphidiella antarctica）、似球卷旋虫（Rosalina cf. globularis）、光亮圆辐虫（Cibicides refulgens）及光滑艾伦贝格虫（Ehrenbergina glabra）为优势类群。覆于混杂岩层之上的中砂层（厚度约1.9米）含13种有孔虫，其优势类群为卷曲拟扣球虫与光滑艾伦贝格虫，南极小箭头虫的占比则低于下伏的混杂岩层。上砂层（厚度约0.46米）仅含4种有孔虫，且壳体数量极少。混杂岩层与中砂层的有孔虫组合被认为是近乎原地的尸积群（thanatocoenoses），其沉积物被解释为海相成因，但受到低盐度水体（hyposaline waters）及近岸冰体的影响。浮游类群（planktic taxa）缺失，这或许指示当时存在潮尾冰川（tidewater glaciers）、海冰（sea ice）及/或低盐度表层水体。上砂层中的小型有孔虫组合则较为复杂，可能属于再旋回产物。基于混杂岩层与中砂层中的有孔虫组合，岩石地层单元2.2被划归为上新世（Pliocene）。覆于岩石地层单元2.2之上的岩石地层单元2.1中的混杂岩层，含有大量第四纪（Quaternary）有孔虫。