Molecular and petrographic indicators of redox conditions and bacterial communities after the F/F mass extinction (Kowala, Holy Cross Mountains, Poland)

► Web-like structures typical for microbial mats and presence of cyanobacteria biomarkers suggest elevated microbial activity after the global Frasnian-Famennian extinction event. ► Presence of cyanobacterial mats implies the prevalence of suboxic to oxic but photic bottom water conditions. ► Common occurrence of isorenieratane and other green sulphur bacteria biomarkers as well as small pyrite framboids through the section suggested that portions of the water column were at least intermittently euxinic.