Calcareous nannofossils are micrometric calcite platelets secreted by the photosynthetic algae named coccolithophores and incertae sedis. Calcareous nannoplankton inhabit the photic zone from coast to open-ocean and have left an abundant fossil record since the Triassic. Therefore, they constitute an interesting material for geochemical studies although they have been overlooked in comparison to foraminifera. We have analyzed manganese distribution and valence in six calcareous nannofossil species representing different ages (Recent to Jurassic) and geological settings (land sections and deep ocean core-tops) and with different structures to assess the potential of Mn as a paleobiological or paleoenvironmental proxy. Nano x-Ray Fluorescence (xrf) maps were established at the esrf id22ni and id21 beamlines and Mn k-edge x-Ray Absorption Near Edge Structure (xanes) at id21. Mn is more abundant in nannofossils from pre-Quaternary rock samples than from core-top samples. In nannofossil rock samples, Mn nanoxrf maps show distributions correlated with primary crystalline organization whereas in nannofossil core-top samples, Mn is either absent or does not follow the crystal organization. Xanes analyses show that Mn is in the form of MnCO₃. All these observations argue for Mn incorporation within calcareous nannofossils controlled by diagenesis through overgrowth of secondary calcite (Ca, Mn)CO₃. Crusts grew along the original crystal growth directions. The incorporation of Mn in some core-top samples highlights potential early diagenesis input when the detached platelet lies on the seafloor or is still in the water column. Mn should therefore be considered a critical tool to identify diagenetic overgrowth rather than primary environmental conditions.

钙质纳米化石是方解石方解石血小板，由光合藻类分泌的球墨石藻和昆虫无性体分泌。从三叠纪开始，钙质纳米浮游生物栖息在从海岸到大洋的光合带，并留下了丰富的化石记录。因此，尽管它们与有孔虫相比却被忽略了，但它们构成了一种有趣的地球化学研究材料。我们分析了六个钙质纳米化石物种中的锰分布和化合价，这些物种代表不同的年龄（最近到侏罗纪）和地质环境（陆地部分和深海核心顶）并具有不同的结构，以评估Mn作为古生物学或古环境代用品的潜力。纳米x射线荧光（xrf）在esrf id 22 ni和id 21束线和Mn k边缘x射线吸收近边缘结构（xanes）的id 21处建立了地图。第四纪前岩石样品中的纳米化石中的锰含量比岩心顶部中的锰含量更高样品。在纳米化石岩石样品中，Mn纳米xrf图谱显示与初级晶体组织相关的分布，而在纳米化石芯顶样品中，Mn不存在或不遵循晶体组织。X ANES分析表明Mn为碳酸锰的形式₃。所有这些观察结果表明，通过次方解石（Ca，Mn）CO _3的过度生长，成岩作用控制的钙质纳米化石中锰的掺入。结壳沿原始晶体生长方向生长。当分离的血小板位于海底或仍在水柱中时，某些核心顶部样品中Mn的掺入突出了潜在的早期成岩作用。因此，应将锰视为确定成岩过度生长的关键工具，而不是主要的环境条件。