Molekulare Fossilien: Schlüssel zum Ursprung diagenetischer Karbonatkonkretionen

成岩碳酸盐结核通常在浅层埋藏过程中通过软沉积的局部岩化作用形成，长期以来被认为是保存完好的化石的来源。虽然结核在许多古代沉积物中很常见，但现代的等效物非常罕见，我们对其形成背后复杂的生物地球化学过程的理解尚不完整。在这个项目中，用有机地球化学技术研究包裹在古代固结物中的有机物，为这些沉淀物的形成提供进一步的线索，并测试它们作为保存异常的分子化石容器的意义。研究人员提出，固结物中的脂质生物标志物和干酪根可能代表了原始沉积有机质的“快照”，以及在新沉积的沉积物中曾经发生的早期微生物过程。一个特别的重点放在测试羧酸（特别是脂肪酸，“脂肪”）的钙和或镁盐的作用，以及它们的厌氧降解产物作为形成碳酸盐结块的原料。为此，将使用萃取物（GC-MS, IRM-GC-MS）和热解技术（Hypy; Py-GC-MS）研究巴伐利亚州布滕海姆（Buttenheim）和下萨克森州Hondelage)的古（早侏罗世）碳酸盐固结物与其直接寄主岩石的关系。

Diagenetic carbonate concretions commonly form during shallow burial via localized lithification of soft sediment and have long been recognized as a source of exceptionally preserved fossils. While concretions are common in many ancient sediments, modern equivalents are very rare and our understanding of the complex biogeochemical processes underlying their formation is incomplete. In this project the organic matter enclosed in ancient concretions is studied with organic geochemical techniques to provide further clues to the formation of these precipitates and test their significance as containers of exceptionally preserved molecular fossils. It is proposed that lipid biomarkers and kerogen locked in concretions may represent a "snapshot" of the original sedimentary OM, plus the early microbial processes as they once occurred in the freshly deposited sediment. A particular focus is placed on testing the role of Ca- and or Mg-salts of carboxylic acids (particularly fatty acids, "adipocere"), and their anaerobic degradation products as raw materials for the formation of carbonate concretions. For this purpose, ancient (Early Jurassic) carbonate concretions from Buttenheim (Bavaria) and Hondelage (Lower Saxony) will be studied in relation to their immediate host rocks using extract based (GC-MS, IRM-GC-MS) and pyrolysis techniques (Hypy; Py-GC-MS).