Biological and geological characterization of modern biofilms and microbial mats and comparison with similar lithified structures in Colombian Cretaceous formations.

Microorganisms may play an important role in the binding of sediments and the formation of sedimentary structures, by means of the formation of biofilms and microbial mats. In this work, filamentous cyanobacteria from three different environments were compared: a biofilm from a lacustrine environment with intervals of flooding/desiccation, a biofilm from a continental saline environment, and a microbial mat from a thermal spring. The optical identification of the cyanobacteria allowed to establish that in the biofilms there is a dominance of the Order Oscillatoriales, while in the microbial mat both cyanobacteria of the Orders Nostocales and Oscillatoriales dominated. Two rock samples isolated from the thermal spring which genesis was possibly influenced by the activity of cyanobacteria are described and classified. One of them is a travertine/microbial framestone with stromatolitic and thrombolytic texture. The second one is classified as a mudstone/microbial boundstone. Finally, a comparison between the sedimentary structures identified in those rocks with similar structures in the formations La Luna, Paja and Tetuán, deposited during regressive phases of the Colombian Cretaceous epyric sea, and microbial mat features previously described is performed. Based on morphological resemblance, fibrillar networks identified locally in those formations are interpreted as possible biolaminations originated from the activity of cyanobacteria. [ABSTRACT FROM AUTHOR]