Paleoenvironmental assessment and organic matter preservation of the latest Pliensbachian to early Toarcian

The late Pliensbachian to early Toarcian (Early Jurassic, ~183 Ma) records profound environmental perturbations, associated with global rise in temperatures. Climate change was linked to greenhouse gases emissions, as inferred from a globally expressed negative Toarcian carbon isotope excursion (T-CIE). At some shelf areas, such as the European Epicontinental Basin System (EEBS), Toarcian warming favoured the development of oxygen-deficient conditions that culminated in the genesis of the Toarcian Oceanic Anoxic Event (T-OAE). Upper Pliensbachian to lower Toarcian strata, exposed in the Hondelage Section (northern Germany) has been studied by sedimentological and paleontological approaches. These immature black shales provide favourable conditions for organic matter (OM) and biomarker perseveration. Thus, the section represents an ideal sedimentary archive to better understand the environmental changes during the early Toarcian, to study their impact on marine ecosystems, depositional conditions, and to identify possible contributing factors. This thesis is based on the parallel application of different geochemical approaches, including inorganic, organic and isotope geochemistry.

The thermally immature sediments of the Hondelage succession preserve a diverse biomarker inventory. In particular Hopanoid biomarkers, often applied tools for paleoenvironmental reconstruction, are present as various diagenetic transformation products. This allows to trace diagenetic alteration of hopanoids, assess the environmental implications of their composition and hints towards potential precursor molecules and source organisms.

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