Search

Sedimentologika is a community-driven Diamond Open Access (DOA) scientific journal about sedimentology. The journal aims to create a place where people can publish their research and access scientific studies on all types of sedimentary processes, methods, deposits, and environments, across all spatial and temporal scales, on Earth or any other planetary body, for free. The published material will be free to share (i.e., no embargo period) since authors retain the copyright. Sedimentologika is driven by the community for the community and is part of a broader DOA movement in geosciences. Sedimentologika aspires at emancipating from the financial barriers associated to private publishing houses to provide direct and equal access to science to all citizens, scientists, and institutions all over the globe. This journal will be defined by Open Science principles to promote ethical dissemination of science and knowledge, following high equality, diversity, and inclusion standards. Each step of the review and publication process will be visible and easy to follow for authors, reviewers and the community. Sedimentologika will be launched by mid-2022 and we are always looking for motivated people keen on giving a little bit of their time to make Sedimentologika a viable and recognized peer-reviewed scientific journal. Interested in this initiative? Come discuss with us!

Exopolymeric Substances (EPS) form biofilms in which the vast majority of prokaryotic organisms develop and thrive. They are ubiquitous, harbor metal and chemical species binding properties and can be the matrix for bio/orgamineralizations. Because of these properties, EPS have also been proposed as some of the most ancient traces of microbial life on Earth. They form sedimentary structures diagnostic of biological activity in some of the most ancient sedimentary rocks of the Archean. However, the metabolisms hosted by such ecosystems remain poorly understood given poor preservation and specificity of the available molecular, isotopic or fossilized signatures. Deep time paleobiological research therefore needs for new ways to unlock the history of the rare and variably preserved sedimentary rocks of these ages, by looking for new proxies that could help characterizing microbial ecosystems and better understand the co-evolution of the geosphere and the biosphere.We here attempt to describe trace metal signatures of a modern, arsenic-rich lacustrine microbial mat fueled by oxygenic and anoxygenic photosynthesis as an analog to better understand how microbial mats and their sedimentary and chemical signatures can be preserved in the Archean sedimentary record. We coupled in-situ imaging of a microbial mat from modern Dead Sea shore with SEM, Raman spectroscopy, and X-ray mapping, to (meta)genomics data and chemical analyses. Arsenic enrichments in the anoxygenic photosynthetic layer of the mat reached a 10’000-fold level, and was associated to Mg-Si-rich EPS. The latter ultimately mineralized into aragonite clusters with a co-enrichment of Sr, Mn and Mo. At the mat scale, the mineralized zone (rich in Fe, Sr and Ca from authigenic calcium carbonates and detrital clay) is clearly located above the As-enrichment layer, in association with Mn. These data support a chemically dynamic microbial mat where microbial activity, EPS chemical affinity and environmental processes lead to specific organic and mineralized chemical signatures linked to metabolic activity. Metagenomics and synchrotron-based speciation analyses shall confirm the links between elemental enrichments and the microbial metabolic pathways.We parallel this study to a well characterized microbial system of the Archean, the stromatolitic units of the Tumbiana Lake (2.72 Ga, Pilbara, Western Australia). In this environment, microbial mat accretionary behaviour has formed limestone stromatolites harboring layered nanopyrites embedded in carbonaceous material and chlorite (Marin-Carbonne et al., 2018). C, N and S isotopes of mineral fractions have suggested a connection of photosynthetic activity, sulfate reduction and methane cycling, potentially influenced by arsenotrophy (e.g. Thomazo et al., 2009; Sforna et al., 2014; Lepot et al., 2019). This is likely the most diverse undisputed microbial environment of the Archean. Our trace-elemental mapping using PIXE suggests co-enrichment of Mo and As in association to the nanopyrite-OM layer, that could be attributed to arsenotrophic and anoxygenic photosynthetic activity, in a similar fashion than argued for in the Dead Sea mat. Simulated diagenesis experiments are planned and should be able to provide chemical insights into the transformation of microbial mats to their fossilized counterparts at the microscale, to further validate the promises of metal biosignatures for reconstructing Archean ecosystems.

Lake sediments bear valuable information allowing multidisciplinary research to address paleoclimatic and paleoenvironmental reconstructions at regional to global scales. Sedimentological, geochemical, paleontological and biological tools are commonly used to tackle these questions, which are generally driven by a set of intricated parameters. Among them, the importance of biogeochemical cycling is largely acknowledged in the lake (paleo-) water columns and has been at the heart of most paleolimnological studies. The way these signals are transferred to lake sediments has largely been studied. However, microbial communities - the principal actors in the biogeochemical cycling framework - keep being active in the sediment, and continue to influence the preservation and retention of organic and inorganic matter while buried. Gathered within the “early diagenesis” black box, these processes, once qualified, can help better interpret the proxies they may influence, and even constitute new ones. Within this work, we provide examples showing that the integration of studies of the subsurface biosphere within geo- and paleo-limnology investigations can help unlock or secure the potential of multiproxy analysis for reconstructing the paleoenvironments, paleoclimates and paleo-ecology of lake basins. The use of now well-developed OMICS methods, through the analysis of environmental and/or ancient DNA and lipids in particular has been coupled to mineralogical, isotopic and magnetic information in the Dead Sea (Levant) to demonstrate the differential preservation of mineralogic and sedimentologic signals along the last two glacial-interglacial cycles (Thomas et al., 2015, 2016; Ebert et al., 2018). Similar signals have been unlocked in Lake Towuti (Indonesia) and in Laguna Potrok Aike (Argentina) (Vuillemin et al., 2015, 2017). In Lake Ohrid (North Macedonia/Albania), environmental DNA has provided limited inputs on that perspective (Thomas et al., 2020), but has shown that ancient/fossil DNA could provide valuable information regarding the lake primary productivity and the status of its watershed land-cover. Integrating OMICS methods to tackle the identity and activity of the ancient and modern subsurface biosphere of lakes therefore holds an immense potential not only for microbiology investigations, but also for paleoclimatic and paleoenvironmental reconstructions.Ebert et al. (2018) Overwriting of sedimentary magnetism by bacterially mediated mineral alteration. Geology 46, 2–5.Thomas et al. (2016) Microbial sedimentary imprint on the deep Dead Sea sediment. The Depositional Record 1–21.Thomas et al. (2020) Weak influence of paleoenvironmental conditions on the subsurface biosphere of lake ohrid over the last 515 ka. Microorganisms 8, 1–20.Thomas et al. (2015) Impact of paleoclimate on the distribution of microbial communities in the subsurface sediment of the Dead Sea. Geobiology 13, 546–561.Vuillemin et al. (2015) Recording of climate and diagenesis through fossil pigments and sedimentary DNA at Laguna Potrok Aike, Argentina. Biogeosciences Discussions 12, 18345–18388.Vuillemin et al. (2017) Preservation and Significance of Extracellular DNA in Ferruginous Sediments from Lake Towuti , Indonesia. Frontiers in Microbiology 8, 1–15.