Project Details
Projekt
Diagenesis at depth: Coupled carbon-phosphorus-metal cycling in an Earthquake-dominated deep-sea trench system (Japan Trench, IODP Expedition 386)
Applicant
Professor Dr. Christian März
Subject Area
Geology
Oceanography
Oceanography
Term
since 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 546772176
Deep-sea trenches are amongst the least studied depositional systems of the oceans - despite their global distribution along subduction zones. Their depositional conditions are often very dynamic: Large volumes of sediment are delivered in phases, e.g., in relation to Earthquakes, while the background sedimentation is very slow. Deep-sea trench deposits are therefore ideal paleo-seimological archives. This was a main motivation for IODP Expedition 386 that very successfully recovered up to 40 m long sediment cores from different sections of the Japan Trench. Another, yet poorly studied aspect of deep-sea trench deposits is their potential role in biogeochemical element cycles. The sudden mobilisation of sediments from shallower parts of the ocean, triggered by Earthquakes, delivers chemically very reactive material into the deep sea. Studying this chemical reactivity, in particular for carbon, phosphorus, iron and manganese, is the focus of this proposal. Two objectives are at its centers: Firstly, we want to study in what form carbon is delivered into these deep-sea trenches, and whether it gets stored in the sediments over long timescales. The chemical association of carbon with iron and manganese oxides, in particular, promotes its long-term preservation in the seafloor. The significance of this "rusty carbon sink" in deep-sea trench deposits is completely unknown so far. Another focus is on the phosphorus cycle. As an essential nutrient for any form of life, phosphorus is deposited at the seafloor mostly in association with organic matter, but in the sediments it changes its chemical speciation. This process called "sink switching" results in phosphorus incorporation into chemically much more stable phases, with a higher potential to be stored in the sediments over longer timescales. This chemical process has not been studied in deep-sea trenches either. Overall, this project aims to understand and quantify poorly studied, but globally significant aspects of the life- and climate-essential cycles of carbon and phosphorus.
DFG Programme
Infrastructure Priority Programmes
International Connection
China, USA
Co-Investigator
Dr. Piero Bellanova
Cooperation Partners
Professor Dr. Min Luo; Professorin Dr. Natascha Riedinger
