The general topic of this proposal is the study of nitrogen isotopes in chlorins, here broadly defined as chlorophylls and their diagenetic products (i.e. dihydroporphyrins that are functionalized precursors of sedimentary porphyrins..
The general objective is to evaluate the postdepositional sedimentary alteration of the nitrogen isotopic signatures of chlorins, from the early stages of the diagenetic alteration of chlorophylls to the initial stages of the formation of porphyrins. This will allow to constrain the interpretation of nitrogen isotopic signature derived from tetrapyrroles in sediments to reconstruct depositional conditions related to biogeochemical processes in ancient environments.
Measurements of nitrogen isotopes in marine sediments provide a unique way of understanding the cycling of the major nutrients between geologic and biologic reservoirs. Photoautotrophs exist at the interface of these reservoirs, while nitrogen is a central component of their biomass and one of their major nutrients. In this sense, biologically available nitrogen (i.e. non-N2) is representative of the fundamental patterns of biogeochemical cycling in the ocean.