| Popis: |
It was studied that the possibilities of preservation, migration and transformation of organic matter (OM) in rocks of Precambrian age, the textural and structural characteristics of which are inextricably linked with the physiological characteristics of microorganisms, and the role of stylolithization structures in these processes. The similarity of modern stromatolites with ancient ones in the mechanism of deposition of carbonate micrite and the formation of porous frameworks allowed us to establish that a significant amount OM of cyanobacterial lamins could be preserved after the buildings were immersed in the sedimentation basin and transformed into sedimentary strata. OM was concentrated on numerous relict surfaces between micrite carbonate secretions deposited by microorganisms during life. Subsequent transformations were expressed in the recrystallization of the carbonate substance, accompanied by a significant loss of primary voidness, oustion and redistribution of OM, as well as clay material deposited from the suspension. During detailed petrographic studies, it was observed how clay-organic material (COM), displaced by recrystallization, concentrated on the crystal faces and in intercrystalline pores in certain areas and composed numerous lenticular layers in contact with each other, forming surfaces of complex configurations - rudimentary microstylolites. According to the authors, recrystallization is one of the main catalysts of stillolithization processes, because it creates mineral aggregates in which the pressure on the COM enclosed between them varies greatly at different points. This contributes to the occurrence of the phenomenon of differentiated dissolution under pressure, more intensive transformation of OM in areas with maximum load and, as a consequence, excessive release of CO, which in turn leads to saturation of pore solutions with carbon dioxide and initiation of chemical dissolution. Probably, this is how stylolites and associated fractured voidness are formed in stromatolites, which is available for the migration of OM. |
