Formation of fossiliferous concretions in the Cretaceous Santana Formation - Assessing the role of microbial processes

卓越的化石保存（包括在富含有机物的黑色页岩中，软组织磷酸盐化通常与化石标本周围保护性碳酸盐外壳的形成有关。虽然控制软组织矿化的机制，在最早阶段的泥石化相当好的理解，只有有限的信息，目前可用于复杂的地球化学过程，导致沉淀的固结碳酸盐体周围的化石。拟议的试点研究将侧重于碳酸盐结核的有机和无机地球化学，这些结核来自早白垩世桑塔纳组（巴西东北部阿拉里皮盆地）的黑色页岩矿床。这种konservat类型的化石lagerstätte是世界著名的含盐结核托管一个异常保存的鱼类和爬行动物群。本研究的主要目的是双重的，包括（1）识别的类型和桑塔纳结核和（2）不同的微生物或微生物介导的过程与连续的结核生长在早期埋藏的有机质的来源。有机分子地球化学（包括有机地球化学）与地球化学、地球化学具体化合物的δ 13 C分析）与高分辨率无机地球化学和沉积岩相学。

Exceptional fossil preservation (incl. soft-tissue phosphatization) within organic-rich black shales is often associated with the formation of a protective carbonate shell surrounding the fossil specimen. Whereas the mechanisms controlling soft-tissue mineralization during the earliest stage of fossilization are considerably well understood, only limited information is currently available on the complex biogeochemical processes which lead to the precipitation of the concretionary carbonate body around the fossils. The proposed pilot study will focus on the organic and inorganic geochemistry of carbonate concretions derived from black shale deposits of the Early Cretaceous Santana Formation (Araripe Basin, NE Brazil). This konservat-type fossil lagerstätte is world famous for its fossiliferous concretions hosting an exceptionally preserved fish and reptile fauna. The principle aim of this study is twofold including (1) identification of the type and source of organic matter trapped within the Santana concretions and (2) assessment of the different microbial or microbially-mediated processes associated with successive concretion growth during early burial. The achievement of these goals is expected from the combination of organic molecular geochemistry (incl. compound-specific δ13C analytics) with high-resolution inorganic geochemistry and sedimentary petrography.