Abstract Strata of Valanginian age (Early Cretaceous, 139.8–132.9 Ma) record a 1.5‰ positive carbon isotope excursion (CIE), the Weissert Event. It coincides with volcanic activity of the Parana-Etendeka large igneous province. Unlike the Mesozoic Oceanic Anoxic Events (OAEs), no organic-rich deposits documenting widespread perturbation of the marine carbon-cycle are associated with the Weissert Event. To study the impact of paleoceanographic changes in the Valanginian on calcareous nannofossils, this study analyzes coccolith size data of three species (Biscutum constans, Watznaueria barnesiae, Zeugrhabdotus erectus) from northern Germany and the western North Atlantic. Further it presents a new Valanginian carbon isotope record of organic material (δ13Corg) from northern Germany. The dataset records the Weissert Event CIE in the late Valanginian. At both locations biometric analyses reveal size decreases of B. constans coccoliths during the Weissert Event. A size reduction of ~1 μm has been observed for northern Germany (37°N) and of 0.4 μm for the North Atlantic (23°N). The different magnitudes of size decrease possibly reflect the different paleogeographic positions of the sites and the paleoceanographic response to the late Valanginian climate variations. Proxy data support a link between a humid climate with increased weathering, and the observed coccolith size variations. This impacted nannoplankton communities either through the availability of light or by eutrophication and, possibly, nutrient limitation. In addition to increased terrigenous input, emissions of the Parana-Etendeka volcanism possibly acted fertilizing. Furthermore, widely dispersed volcanic emissions possibly caused increased concentrations of toxic trace metals in the surface ocean which affected marine primary producers.

中文翻译：

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Valanginian Weissert 事件（白垩纪早期）期间气候和古海洋学控制钙质纳米化石的大小变化

摘要 Valanginian 时代（早白垩世，139.8-132.9 Ma）地层记录了 1.5‰ 的碳同位素正偏移（CIE），即 Weissert 事件。它与巴拉那-埃滕德卡大型火成岩省的火山活动相吻合。与中生代海洋缺氧事件 (OAE) 不同，没有记录海洋碳循环广泛扰动的富含有机物的沉积物与魏塞特事件有关。为了研究 Valanginian 古海洋学变化对钙质纳米化石的影响，本研究分析了来自德国北部和北大西洋西部的三个物种（Biscutum constans、Watznaueria barnesiae、Zeugrhabdotus直立）的颗石粒大小数据。此外，它还提供了来自德国北部的有机物质 (δ13Corg) 的新瓦兰吉尼亚碳同位素记录。该数据集记录了瓦兰吉阶晚期的 Weissert 事件 CIE。在这两个位置的生物特征分析显示，在 Weissert 事件期间，康斯坦丁藻球粒的尺寸减小。在德国北部 (37°N) 和北大西洋 (23°N) 观察到约 1 μm 的尺寸减小。不同大小的减小幅度可能反映了遗址不同的古地理位置和古海洋对晚瓦兰吉期气候变化的响应。代理数据支持潮湿气候与风化增加之间的联系，与观察到的球石大小变化之间存在联系。这通过光照或富营养化以及可能的营养限制影响了微浮游生物群落。除了增加陆源输入外，Parana-Etendeka 火山活动的排放可能起到了施肥作用。此外，