Formation and diagenetic evolution of actualistic, aragonite-cemented seafloor carbonates

• Applicant: Professor Dr. Adrian Immenhauser
• Subject Area: Palaeontology ; Mineralogy, Petrology and Geochemistry
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 435379576

• Final Report Year: 2024

Final Report Abstract

Work in the Abu Dhabi lagoon has been an eye‐opener in questioning classical paradigms that are cited over and over again in the literature. The transgressive movement of depositional and diagenetic belts in a landward direction has resulted in a "smoking gun" in terms of diagenetic processes in the most proximal domain, while sub‐recent to Pleistocene features are preserved in a lagoon‐ward direction only meters to kilometres apart ("time machine"). The contrast comparison of recent to fossil diagenetic products has proved insightful. Results obtained include a very wide range of diagenetic features, such as the earliest diagenetic seafloor stabilisation by means of microbially‐mediated processes leading to nano‐ACC formation, or a novel and critical view of the genesis of radiaxial calcites and botryoidal types of cement. Moreover, the extremely diverse range of aragonite crystal morphologies stands in clear contrast with the classical perception of marine aragonite fabrics being, a priori, needle‐like features. The combination of direct, actualistic field observations placed into context with environmental and hydrogeochemical processes and the investigation of products by means of thin section, SEM and isotope geochemistry has been very instrumental.

Publications

• Composite micrite envelopes in the lagoon of Abu Dhabi and their application for the recognition of ancient firm- to hardgrounds. Marine Geology, 423, 106141.
  Ge, Yuzhu; Lokier, Stephen W.; Hoffmann, René; Pederson, Chelsea L.; Neuser, Rolf D. & Immenhauser, Adrian
  
• Botryoidal and Spherulitic Aragonite in Carbonates Associated with Microbial Mats: Precipitation or Diagenetic Replacement Product?. Frontiers in Earth Science, 9.
  Ge, Yuzhu; Della, Porta Giovanna; Pederson, Chelsea L.; Lokier, Stephen W.; Hoffmann, René & Immenhauser, Adrian
  
• Seawater chemistry of a modern subtropical ‘epeiric’ sea: Spatial variability and effects of organic decomposition. Geochimica et Cosmochimica Acta, 314, 159-177.
  Pederson, Chelsea L.; Ge, Yuzhu; Lokier, Stephen W.; Swart, Peter K.; Vonhof, Hubert; Strauss, Harald; Schurr, Simon; Fiorini, Flavia; Riechelmann, Sylvia; Licha, Tobias & Immenhauser, Adrian
  
• Radiaxial fibrous calcite forms via early marine‐diagenetic alteration of micritic magnesium calcite. Sedimentology, 70(2), 434-450.
  Ge, Yuzhu; Pederson, Chelsea L.; Lokier, Stephen W.; Strauss, Harald & Immenhauser, Adrian
  
• Carbonate sediment dynamics in the Abu Dhabi lagoon - implications for low-angle inner-to-middle ramp models. Marine Geology, 465, 107172.
  Zhong, Yisi; Lokier, Stephen W.; Pederson, Chelsea L.; Fiorini, Flavia; Hennhoefer, Dominik; Ge, Yuzhu & Immenhauser, Adrian