Microbially induced wrinkle structures in Middle Devonian siliciclastics from the Prague Basin, Czech Republic

The occurrence of wrinkle structures in Middle Devonian deep-water siliciclasticsequences of the Prague Basin (Roblın Member, Srbsko Formation, Givetian) isreported and interpreted to be microbially induced. Current and/or gravitationalforces are considered the simplest explanation of the origin of these structures. Takinginto account the tectonic activity linked with ongoing Variscan orogeny, the wrinklestructures could also be interpreted as soft sediment deformation structures originat-ing due to exposure of mat-bearing sediment to seismic shocks. The distribution of n-alkanes and isoprenoids suggests two types of prevailing biological sources, namelyphytoplankton, representing organic material from the water column, and benthicbacteria. Judging from the sedimentary facies and lack of petrographic characteristicssuggestive of light competition, the microbial mats are interpreted to be formed bynon-autotrophic bacteria.