Lithological–geochemical, petromagnetic, and paleoecological characteristics of the Campanian–Selandian sedimentation conditions in the Ul’yanovsk–Saratov basin

Abstract

The results of a complex study of the Upper Cretaceous carbonate section in the quarry of the cement plant of the town of Sengilei (Ul’yanovsk district) are presented. The Lower Paleocene cyclic opoka member is described. The formation conditions of the Upper Cretaceous cyclic and cryptocyclic, as well as Lower Paleocene cyclic, rocks are interpreted for the first time on the basis of lithological, petrographic, petromagnetic, geochemical, and paleoecological methods. The cyclicity was formed due to dilution cycles under climate fluctuation and eustatic variations, which were caused by eccentricity cycles of the Earth’s orbit. These cycles are identified in the cryptorhythmic lanceolata sequence of the Lower Maastrichtian rocks.