Biologically-mediated weathering in modern cryptogamic ground covers and the lower Palaeozoic fossil record

• Main Authors: Mitchell, Ria L., Strullu-Derrien, Christine, Kenrick, Paul
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Figshare 2019
• Subjects: Geology; FOS Earth and related environmental sciences; Iceland
• Online Access: https://dx.doi.org/10.6084/m9.figshare.c.4373717.v1; https://geolsoc.figshare.com/collections/Biologically-mediated_weathering_in_modern_cryptogamic_ground_covers_and_the_lower_Palaeozoic_fossil_record/4373717/1

Specific micro-weathering features and biochemically-derived residues formed by living organisms can be used as biomarkers to infer the presence of biological communities within sedimentary units of ancient ecosystems. We examined basaltic soil minerals from modern cryptogamic ground covers (CGCs) in Iceland and compared these to two lower Palaeozoic fossil systems. Nine biologically-mediated weathering features (BWFs) were identified in modern soils including micron-scale surface trenching and penetrative tunnels, which are attributed to the actions of bacteria, fungi, and exudates. Specific BWFs are associated with Fe residues and with Fe-rich bio-precipitated nodules. Further, putative comparable features and Fe enrichment are identified in palaeosols from the upper Silurian (Llansteffan; south Wales) and the Lower Devonian (Rhynie chert, Scotland). Although we are cautious about attributing biological affinity to individual isolated features, results demonstrate the potential of using multiple BWF types as a collective together with their chemical signatures as new proxies to understand community structure and interactions in early terrestrial ecosystems body fossil-lacking early terrestrial ecosystems. This new information is the first evidence of interactions between ancient CGC-like organisms with substrate/soil inorganic components in the fossil record, and demonstrates the ability of CGC-like biospheres to contribute to mineral weathering, soil development and biogeochemical cycling during the lower Palaeozoic.