Chemotrophy-based phosphatic microstromatolites from the Mississippian at Drewer, Rhenish Massif, Germany

Abstract The Drewer quarry located in the Rhenish Massif is a well-studied outcrop that comprises Upper Devonian (Famennian) to Lower Carboniferous (Viséan) strata. Within deposits two black shale intervals have been described are linked global oceanic anoxic events, Hangenberg Event and Alum Shale Event. shales associated with Middle Tournaisian contain abundant phosphatic concretions, which were investigated using thin section petrography, powder X-ray diffraction, Fourier-transform infrared spectrometry scanning electron microscopy. concretions formed during several growth phases under at least episodically sulphidic conditions within sediment served as substrate for subsurface microbial mats microstromatolites. microstromatolites occur either partially branched columns of up 600 µm length attached or smaller, bulbous aggregates surrounding concretions. Element mapping identified presence pyrite other metal sulphides carbon oxygen stable isotopic composition phosphate-associated carbonate suggests mat-forming microorganisms probably anaerobic, chemotrophic communities dwelling environment Such interpretation agrees deeper-water depositional setting Black its high content organic matter, suggesting potent agents phosphogenesis general, formation stromatolites particular.