Inorganic geochemical redox proxies - indicators for rapid paleoenvironmental changes and related diagenetic processes in recent and ancient marine sediments

Abstract

Deep-sea fan, early diagenesis, susceptibility, anaerobic oxidation of methane, black shale, anoxia, oceanic anoxic event, trace elements, iron, phosphorus, sediment source, redox changes, enrichment factors, sequential extraction. - In the context of present-day changes of atmo-, hydro-, geo- and biosphere processes, there is growing interest to decipher rapid paleoenvironmental changes in the geological past. Marine deposits provide valuable insights into paleoenvironmental conditions that prevailed during their deposition, if we know how to read the respective signals in the sedimentary record. However, caution is demanded as primary signals of past environmental conditions can be altered by postdepositional diagenetic processes. In the presented work, we will show the potentials, but also limitations of inorganic geochemical proxies to record signals of abrupt paleoenvironmental shifts in the terrestrially dominated Late Quaternary deposits of the Zambesi deep-sea fan (SE African margin), and in a fully marine Late Cretaceous black shale succession on Demerara Rise (NW South American margin).