Neogene planktonic foraminifera of DSDP Leg 41 holes

During Leg 41 Neogene sediments were recovered from five sites off northwest Africa.
On the Sierra Leone Rise (Site 366), Neogene sediments consist of nanno oozes, nanno chalk, and calcareous clays 230 meters thick, resting conformably on the late Oligocene sediments. The common succession of zones occurs with two hiatuses. The lower gap corresponds to an interval around the lower/middle Miocene boundary (the Praeorbulina glomerosa and Orbulina suturalis-Globorotalia peri-pheroronda zones are absent) and the upper gap coincides with an interval around the middle/upper Miocene boundary (the Sphaeroidinellopsis sub-dehiscens-GIobigerina druryi, Globigerina nepenthes-Globorotalia siakensis and Globorotalia conlinuosa zones are missing).
In the Cape Verde Basin (Site 367) deep-water Neogene turbidites (about 200-250 m thick) contain poor fauna of redeposited and sorted Cretaceous, Eocene, Oligocene, and Neogene species.
On the Cape Verde Rise (Site 368) the Neogene section starts with slightly calcareous and non-calcareous clays with poor planktonic foraminifers of the lower Miocene. Later on this area was uplifted and clayey sediments have been replaced upsection in order by more shallow-water clayey nanno and nanno-foraminifer oozes and marls and pure calcareous oozes. In the middle Miocene, planktonic foraminifers are still not diverse, but since the level of the Globigerina nepenthes-Globorotalia siakensis Zone, almost all Neogene zones have been traced. The minimum thickness of the Neogene sediments is about 230 meters.
On the continental slope off Spanish Sahara (Site 369) monotonous calcareous pelagic sediments of Neogene age (164 m thick) overlie the late Oligocene comformably, or with a small time gap. A set of zones beginning from the Globigerinoides primordis-Globorotaiia kugleri Zone up to the Globorotalia fohsi fohsi Zone has been revealed with a gap corresponding to the Globigerinita stainforthi and the Globigerinatella insueta-Globigerinoides irilobus zones. Above that follow sediments with heterogeneous microfauna which result from redeposition or mixing of sediments during drilling. The section ends with sediments of the late Miocene and lower Pliocene with abundant planktonic foraminifers. The latter are unconformably overlain by the Quaternary ooze.
In the Morocco basin (Site 370) deep-water marls and calcareous clays of the lower Miocene contain poor assemblages of planktonic foraminifers. The middle and upper Miocene are represented by turbidites (alternation of nanno oozes, clays, siltstones, and sands) with heterogeneous microfauna. Total thickness of Neogene is up to 200 meters.
In general the Neogene foraminifer microfauna of the area studied includes the majority of species which developed within the tropical-subtropical belt. The entire succession of the Miocene and Pliocene foraminifer zones occurs. The only exclusion is the Sphaeroidinellopsis subdehiscens-Globigerina druryi Zone of the middle Miocene.
The distribution of species is shown on three tables. Comments are given for 47 species and subspecies of foraminifers (stratigraphic ranges, peculiarities of morphology, and ultrastructure of the shell wall).

第41航次在非洲西北外海的5个站位获取了新近纪（Neogene）沉积物。
在塞拉利昂海隆（Sierra Leone Rise，站位366），新近纪沉积物由厚度达230米的颗石藻软泥、颗石藻白垩及钙质黏土组成，整合覆于渐新世（Oligocene）晚期沉积物之上。该区域发育典型的有孔虫带序列，但存在两处沉积间断（hiatus）：下部间断对应下/中中新统（Miocene）界线附近时段，缺失格氏拟球室有孔虫（Praeorbulina glomerosa）带与缝口抱球虫-周缘回转有孔虫（Orbulina suturalis-Globorotalia peripheroronda）带；上部间断对应中/上中新统界线附近时段，缺失亚裂球室拟抱球虫-德鲁里抱球虫（Sphaeroidinellopsis subdehiscens-Globigerina druryi）带、猪笼草抱球虫-西亚克回转有孔虫（Globigerina nepenthes-Globorotalia siakensis）带及连续回转有孔虫（Globorotalia continuosa）带。
在佛得角盆地（Cape Verde Basin，站位367），厚度约200~250米的深水新近纪浊积岩（turbidites）中含有保存较差的再沉积、分选后的白垩纪（Cretaceous）、始新世（Eocene）、渐新世及新近纪物种化石组合。
在佛得角海隆（Cape Verde Rise，站位368），新近纪剖面以含下中新统浮游有孔虫（planktonic foraminifers）且保存较差的弱钙质及非钙质黏土为开端。后续该区域发生构造抬升（uplifted），黏土沉积物自下而上依次被更浅水环境的黏土质颗石藻-有孔虫软泥、泥灰岩（marls）及纯钙质软泥所取代。中中新世时期，浮游有孔虫仍未呈现较高分异度，但自猪笼草抱球虫-西亚克回转有孔虫带以来，几乎所有新近纪有孔虫带均可被识别。新近纪沉积物的最小厚度约为230米。
在西属撒哈拉（Spanish Sahara）外海大陆坡（continental slope，站位369），厚度164米的均质新近纪钙质远洋沉积物（pelagic sediments）整合（或仅存在微小沉积间断）覆于渐新世晚期沉积物之上。已识别出一套从始初抱球虫-库格勒回转有孔虫（Globigerinoides primordis-Globorotalia kugleri）带到福氏回转有孔虫福氏亚种（Globorotalia fohsi fohsi）带的有孔虫带序列，其中缺失斯坦福斯抱身虫（Globigerinita stainforthi）带与不整抱球虫-伊尔博斯抱球虫（Globigerinatella insueta-Globigerinoides irilobus）带。该间断之上的沉积物含有不均一的微化石组合，其成因是钻探（drilling）过程中的沉积物再沉积或混合。剖面顶部为富含浮游有孔虫的晚中新世（late Miocene）及下上新统沉积物，其上以不整合接触关系覆盖有第四纪（Quaternary）软泥。
在摩洛哥盆地（Morocco basin，站位370），下中新统的深水泥灰岩与钙质黏土中含有保存较差的浮游有孔虫组合。中中新统与上中新统由含不均一微化石组合的浊积岩（颗石藻软泥、黏土、粉砂岩（siltstones）与砂岩（sands）互层）所代表。新近纪沉积物总厚度可达200米。
总体而言，研究区域内的新近纪有孔虫微化石组合包含绝大多数热带-亚热带域（tropical-subtropical belt）发育的有孔虫物种。该区域完整发育了中新统与上新统的有孔虫带序列，仅缺失中中新统的亚裂球室拟抱球虫-德鲁里抱球虫带。
物种分布情况详见3张表格。文中对47种有孔虫及其亚种进行了注释，内容包括地层延限（stratigraphic ranges）、形态特征及壳壁（shell wall）超微结构（ultrastructure）。