Early Permian Freshwater Silicified Stromatolites and Oolites from the Krkonoše Piedmont Basin (Bohemian Massif): Paleobiology, Environmental Setting and Early Diagenesis

 

Authors: Vodrážková S, Vodrážka R, Kumpan T, Franců J, Holá M, Slavíček K

Article in press: Received 10 December 2024; Accepted in revised form 21 May 2025; Online 29 June 2025

Keywords: early Permian, Krkonoše Piedmont Basin, stromatolites, oolites, cyanobacteria, silicification,

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Supplementary material

Electronic supplementary material 1 (1573 kB)

Features of stromatolites and oolitic facies, X-ray diffraction pattern, optical cathodoluminescence, boxplots of selected elements, UCC-normalized REE + Y patterns, discriminating bivariate plots


Electronic supplementary material 2 (3873 kB)

EDS spectra, REE+Y data, biomarkers


 

Abstract

Late Palaeozoic non-marine microbialites remain poorly documented despite their potential significance for understanding terrestrial ecosystems during this period of profound climatic and environmental change. Here we report exceptionally preserved lower Permian (Autunian regional stage ˜ Asselian-Sakmarian) silicified stromatolites and oolites from the Krkonoše Piedmont Basin (Bohemian Massif, Czech Republic). Despite their occurrence in Quaternary eluvial and colluvial deposits, multiple lines of evidence suggest formation in a shallow, ephemeral fluviolacustrine setting. The stromatolites display a vertical succession of different growth forms, including structures similar to modern sheath-forming cyanobacterial taxa that form fan-like and hemispheroidal colonies with characteristic upright growth, features especially common in modern streams and rivers. Early diagenetic silicification preserved not only delicate stromatolitic architectures but also microbial organic matter. The presence of volcaniclastic material within ooidal cortices and cores, as well as within the rock matrix, indicates contemporaneous volcanic input, which likely provided silica for early replacement of the primary carbonate fabric. This exceptional preservation, facilitated by rapid CaCO3 encrustations of microbial structures and subsequent early silicification, provides rare insights into early Permian terrestrial ecosystems.