In the Late Cretaceous and Paleogene, two prolonged karst periodes interrupted the relatively continuous, predominantly shallow-marine sedimentation of the northern part of the Adriatic Carbonate Platform (AdCP). The younger, Cretaceous-Paleogene paleokarts, separates the Valanginian-Hauterivian to Campanian shallow-marine carbonates of the inner parts of the AdCP from the Maastrichtian to Eocene palustrine, periplatform and shallow-marine carbonates of the synorogenic carbonate platform. The stratigraphic gap widens from the northeast to the southwest, with mailny the inner parts of the platform exposed to the land. On the other hand, during the Cretaceous-Paleogene peroid, some areas of the northeastern margin of the platform were not uplifted above sea level; instead, they were gradually submerged into deeper seas, forming a gentle slope towards the foreland basin in the Late Cretaceous.
The aim of this study was to document the sequence of carbonate rocks of the AdCP in the Postojna region and based on facies of carbonate rocks and diagenetic history, confirm of disprove the hypothesis of the existence of two erosion-discordant surfaces.
At the beginning of profil P1, rudist limestones represent the Lipica formation, followed by micritic limestones of the Liburnia formation with numerous haracean algae and discorbids. Follows the sedimentation in the brackish enviroment near the land with a stong influence of meteoric water, evidenced by the abundant debris of microcodium grains, globules, fenestral porosity and rhizolites. The last segment of the profile represents limestone breccia, deposited in a shallow-marine anviroment with an open connection to deeper seas, as comfirmed by isotopis and elemental analyses. Chatodoliminiscence revealed more reducing contidions of diagenesis. Although the limestone of the studied profile in the upper part of the Cretaceous (Maastrichtian) show unequivocal signs of pedogenic alteration ant the presence of meteoric water in both sedimentary and diagenetic enviroments, we could not prove the existance of longer paleokarstic gaps in carbonate sequence.
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