T08 - Biochemical processes in sedimentology

T08-SS01 - Microbial imprint on the sediment record: From organomineralization to global biogeochemical cycling

Conveners: Thomas C. (University of Geneva, Switzerland), Petráš D. (Czech Geological Survey, Czech Republic), Pérez A.M. (Institute of Palaeontology ZRC SAZU, Slovenia)

From iron formations to stromatolitic facies, microbes have been instrumental for the formation, composition and preservation of sedimentary units since the dawn of life on Earth. As such, the chemical and isotopic signatures imparted by their activity in these rocks have been used to disentangle the long-term chemical evolution of the atmosphere and ancient oceans. Nonetheless, assessing the primary origin and biogenicity of certain minerals and textures remains challenging, despite these factors being crucial to our quest to understand key stages in evolution of life and earth systems. The diversity and complexity of life forms and metabolisms interacting from the moment of deposition and during shallow burial, along with the rare availability of exceptionally well-preserved ancient chemical rocks has also encouraged an active search for modern analogues to ancient microbially influenced sedimentary deposits. For this session, we seek contributions envisioning approaches for understanding the signatures derived from microbial activity on any type of sedimentary archive, including carbonates, silica-rich deposits, shales, modern lacustrine or marine sediments, soil crusts, etc. Studies describing how active microbes act as key agents in both mineral authigenesis and diagenetic alteration are particularly welcome. Given the complexity of studying such processes, the session is also open to the presentation of approaches allowing multiscale analyses, at the interface between biology and geology.

T08-SS02 - Diagenetic signals in the sedimentary record of environmental change

Conveners: Nohl T. (Geozentrum Nordbayern, Germany), Reuning L. (Kiel University, Germany), Vleeschouwer D. (Universität Bremen, Germany), Wright V. P. (National Museum Wales, UK)

The term “diagenesis” is used for a broad range of processes in sedimentology, including early, late, chemical, and physical alteration. Many of these processes influence the transformation from soft sediment into solid rock. Thereby, paleoenvironmental information can be lost, or even worse, an artificial signal can be introduced. The identification and evaluation of diagenetic processes is vital to accurately interpret and reconstruct palaeoe-nvironmental conditions. This session invites contributions from the wide field of diagenesis, including e.g. the identification and differentiation of diagenetic processes, case studies from fresh water, restricted marine and full marine environments. We welcome abstracts with suggestions on how to circumvent diagenetic overprints in the fields of palaeontology, palaeoclimatology, paleo- ceanography, cyclostratigraphy and sedimen-tology. But we also encourage abstracts warning for potential biases introduced by diagenesis in these fields of study. In other words, this session aims to revive the discussion within this long-standing debate in sedimentology.
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