Abstract
Geological and microbiological information was gathered in order to identify the potential relationships between minerals and/or chemical elements contents in the sparse biomicrite, a sandstone and a mudstone with bacterial communities that were cultivated from a "scrapped off" made on each of these lithologies which were sampled on the Cretaceous sedimentary sequence of the Churuvita Formation (Road Tunja-Villa de Leyva). Three types of evaluations were made on each of these sample rocks: quantitative mineralogy was obtained through rock petrography, X-ray fluorescence analysis of the major element composition (weight percent) of the rocks and quantitative bacterial count per gram in order to know the amounts of communities that would be able to grow in each type of rock. Analogous amounts of bacterial communities grew up in the three lithology types: 144 bacterial morphotypes grew up in total; 43 of them corresponding with the sparse biomicrite, 49 with the fine grain sandstone and while 52 with the mudstone. No significant differences in the growth of bacterial populations were found between the three rocks types. The reason for this could come be because the communities which developed over the biomicrite obtained their basic necessities from calcium carbonate (87.3 percent) while those ones which rose over the sandstone and siltstone obtained there necessities from the silica (82 quartz and 58 percent, respectively). High Al2O3 and SiO2 concentrations in the siltstone (JY-3 sample) could have facilitated the development of most important bacterial populations. The preliminary findings show the need to carry out new systematic samplings on the rocks to establish the influence level the lithologies over the bacterial communities' growth.
