Nummulitic accumulations are an important component of the Eocene sedimentary record in the Neotethyan realm. Their age, paleoenvironmental significance and depositional model are almost exclusively based on the interpretation of the larger benthic foraminiferal assemblages. We show here, however, that the high-resolution study of the other, often neglected, microfossils (calcareous nannoplankton and benthic foraminifera) is crucial to better constrain the diversity and paleoenvironmental gradient along the nummulitic accumulation(s). The studied micropaleontological assemblages, recovered from the large Eocene (Bartonian) nummulitic accumulation in the northwestern Transylvanian Basin (Romania), suggest an inner shelf depositional environment. A depth and nutrient gradient along the nummulitic accumulation from the south to the north could be recognized. In the southern part of the study area the environment was shallow and oligotrophic with Zygrablithus bijugatus, Blackites inflatus, Neococcolithes dubius, Ericsonia spp., larger sized reticulofenestrids and epiphytic foraminifera taxa (Pararotalia, Lobatula and Cibicides) on a sandy substrate. The progressive deepening toward the north led to an increase in clay content and more nutrient-rich marine waters in which calcareous nannoplankton (especially Reticulofenestra minuta), agglutinated foraminifera and calcareous infaunal foraminifera (Nonion, Protelphidium and Reusella) proliferated. The calcareous nannoplankton and smaller benthic foraminiferal assemblages confirm and further constrain the Bartonian age of the studied nummulitic accumulation, previously based on the larger benthic foraminiferal SBZ 17 zone.

分子沉积物是新特提斯地区始新世沉积记录的重要组成部分。它们的年龄，古环境意义和沉积模型几乎完全基于对较大底栖有孔虫组合的解释。但是，我们在这里显示，对其他经常被忽略的微化石（钙质纳米浮游生物和底栖有孔虫）的高分辨率研究对于更好地限制沿生物累积的多样性和古环境梯度至关重要。从西北特兰西瓦尼亚盆地（罗马尼亚）的大型始新世（Bartonian）算术成藏中回收的研究的微古生物学组合表明了一个内部陆架沉积环境。从南到北沿累积积累的深度和养分梯度可以被识别。在研究区的南部，环境较浅，贫营养，Zygrablithus bijugatus，Blackites inflatus，Neococcolithes dubius，Ericsonia spp。，较大尺寸的网状雌蕊和附生有孔虫类群（Pararotalia，Lobatula和Cibicides）都在沙质基质上。对导致增加粘土含量和营养丰富的多海域北部的进行性加深，其中钙质微型浮游生物（尤其是Reticulofenestra小粒），凝集有孔虫和钙质infaunal有孔虫（非离子型，Protelphidium和Reusella）激增。钙质的纳米浮游生物和较小的底栖有孔虫组合证实并进一步限制了所研究的数字积聚的巴通时代，以前是基于较大的底栖有孔虫SBZ 17带。