We investigate changes in calcareous nannofossil and ostracod communities, which reflect surface and bottom water conditions, respectively, across the Cretaceous-Paleogene transition (K-Pg) at the Cerro Azul Section, Jagüel Formation, Neuquén Basin, Argentina. The K-Pg transition at the Cerro Azul Section is characterized by calcareous nannofossil and ostracod turnovers, from assemblages dominated by Cretaceous forms to assemblages composed by incoming Danian taxa and several survivor species. These assemblage changes were associated with a collapse in carbonate production at the K-Pg boundary, probably related to a drop of surface water productivity, and a subsequent recovery in the early Danian, as suggested by carbonate content, log(Ba/Fe) and log(Ba/Ti) trends. During the Late Maastrichtian, peak relative abundances of Eiffellithus spp., just before the K-Pg transition, were probably related to enhanced surface water productivity. High abundances of Cervisiella operculata suggest decreased surface productivity during the earliest Danian. This surface productivity collapse may have reduced food availability in the benthic habitat, which probably led to the stablishment of Citherudiae-dominated ostracod assemblages. Upward in the section, increased relative abundances of Braarudosphaera bigelowii, are probably related to overall intensified weathering conditions and, consequently, increased continental runoff and fresh water input.

我们调查了阿根廷内乌肯盆地Jagüel组Cerro Azul断面的白垩纪-古近纪过渡（K-Pg）的钙质纳米化石和ostracod群落的变化，分别反映了地表水和底部水的状况。塞罗·阿祖尔（Cerro Azul）断面的K-Pg转变的特征是钙质纳米化石和成骨龙的周转，从白垩纪形式占主导的组合到传入的达尼安类群和一些幸存物种组成的组合。这些组合的变化与K-Pg边界碳酸盐产量的下降有关，可能与地表水生产率的下降有关，随后在达尼安早期又恢复了，碳酸盐含量，log（Ba / Fe）和记录（Ba / Ti）趋势。在马斯特里赫特晚期，相对丰度达到峰值。刚好在K-Pg转变之前的Eiffellithus spp。可能与提高地表水生产率有关。塞维氏菌高丰度表明最早的达尼安期间地表生产力下降。这种地表生产力的崩溃可能使底栖生境的食物供应减少，这可能导致了以虎尾草科为主导的成龙类组合的稳定化。在该部分的上部，较大的Braarudosphaera bigelowii的相对丰度可能与总体气候条件增强有关，因此，增加了大陆径流和淡水输入。