Understanding palaeoenvironmental constraints on glaucony formation – insights from Late Cretaceous greensand giants

绿色自生海相粘土发育于晚古元古代至近代，以白垩纪为中心，形成了最大的沉积期。本项目旨在了解控制晚白垩世（早白垩世至晚白垩世）大量绿色海相粘土矿物形成的环境参数，以及它们在全球许多盆地近岸环境中形成的厚而广泛的绿滩序列（“绿滩巨人”）。综合方法结合了地层学、沉积学、矿物学和地球化学分析以及白垩纪古环境/地理背景。该项目与中欧岛周围年代久远的区域联系在一起，同时也挑战了均变论的地质原则，即“现在是过去的关键”：在近岸环境中，以海绿石为主的绿地的大规模、非常广泛的形成和积累与最近沉积系统的数据不匹配。这些观察结果表明，它们的存在并不总是过去的关键，我们认为白垩纪时期广泛存在的浅海绿色海相粘土形成基本上是由来自低洼、深度风化大陆的河流通量的（物理）化学性质控制的。该项目的主要目标可以概括如下：1)调查中欧岛周围绿地巨人的地层、沉积学和古地理条件；2)获得绿色岩石颗粒的定量数据（形态、颜色、丰度、矿物学、地球化学）；3)表征和认识晚白垩世浅海绿地形成的地球化学环境；4)验证晚白垩世（早期）广泛分布的浅海海绿海的形成与大陆的深层风化作用和河流径流的化学性质有关的假说。尽管该应用程序是基于德国的区域剖面，但它处理的是一个相当重要的全球现象，可以在拟议的研究区域内缩小范围并很好地解决这个问题：对中欧岛周围不同环境的综合分析和比较将为晚白垩世绿地和巨人的形成条件提供线索。

Green authigenic marine clays developed in Earth history from the late Palaeoproterozoic to the Recent with an accumulation maximum centered on the Cretaceous Period. This project aims at understanding the environmental parameters which controlled the massive formation of green marine clay minerals during the (early) Late Cretaceous (Cenomanian to Coniacian) and their accumulation to thick, widespread sequences of greensands ("greensand giants") characterising nearshore settings in many basins worldwide. The integrated approach combines stratigraphical, sedimentological, mineralogical and geochemical analyses with the Cretaceous palaeoenvironmental/-geographical context. Regionally tied to and based on well-dated sections around the Mid-European Island, the project also challenges the geological principle of uniformitarianism positing that "the present is the key to the past": the massive, very widespread formation and accumulation of glaucony-dominated greensands in nearshore settings is not matched by data from recent depositional systems. These observations suggest that the presence is not always the key to the past and we suggest that the widespread shallow-marine green marine clay formation during Cretaceous times was basically controlled by the (physico-)chemical properties of the riverine flux from the low-lying, deeply weathered continents. The main goals of the project can thus be summarised as follows:1) to investigate stratigraphical, sedimentological and palaeogeographical conditions of greensand giants around the Mid-European Island;2) to obtain quantitative data on the rock-forming green grains (morphology, colour, abundance, mineralogy, geochemistry);3) to characterise and understand the geochemical environment of shallow-marine Late Cretaceous greensand formation;4) to test the hypothesis that widespread shallow-marine glaucony formation during the (early) Late Cretaceous is related to the deep weathering of the continents and the chemical properties of the fluvial run-off.Although the application is regionally based on sections from Germany, it deals with a global phenomenon of considerable importance that can be narrowed down and tackled well in the proposed study area: the integrated analysis and comparison of different settings around the Mid-European Island will provide clues for the formation conditions of Late Cretaceous greensand giants.