Influence of local sedimentary conditions on development of microbialites in the Oxfordian carbonate buildups from the southern part of the Kraków–Częstochowa Upland (South Poland)

During the Late Jurassic, the Kraków–Częstochowa Upland area was situated on a shelf that linked a shallow epicontinental basin with the Tethys Ocean. Locally, carbonate buildups of differentiated size and structure developed on this shelf. The buildups comprise different varieties of microbialites: leiolites, thrombolites and stromatolites of variable properties. Negative Ce anomalies and distinct enrichment in heavy rare earth elements present in all studied microbialites indicate that on the entire Late Jurassic shelf in the Kraków region the sea water was generally well oxygenated and comparable, as far as alkalinity is concerned, to the recent one. Differentiated development of microbialites was controlled by local sedimentary conditions, unrelated to distinct changes of sea water chemistry. It is likely that formation of microbialites was mainly dependent on the content of dissolved amino acids, colloidal organic matter or fine-grained nutrient suspension and the energy of sedimentary environment.