Structure and formation of the Lower Cretaceous–Eocene section in the central part of the Simferopol Uplift

Abstract

This article provides the first detailed description of the 25-m thick Cretaceous–Eocene section near the Mazanka village and its stratigraphic subdivision. The geological history of the Simferopol Uplift was unraveled by comparison with the outcrops of the Zuya quarry and the Bodrak River basin, facies analysis, and reconstruction of the sedimentation environments. The results obtained show that the Valanginian–Early Hauterivian silty and sandy deltaic deposits of the regressive sedimentation phase are concordantly overlapped by a transgressive sequence formed (from bottom to top) by sandy sediments of the coastal shallows, interlayering middle ramp clayey silts and sands, and outer ramp clays. Above the unconformity, a break of at least 70 Ma was registered from the Early Hauterivian to the Late Ypresian. The Upper Ypresian sediments dated by foraminifera were found to rest erosively on the Lower Hauterivian clays altered by the processes of subaerial soil formation. The Upper Ypresian lower part is formed by the transgressive lag of glauconite-quartz sandstones accumulated near the coast. Sandy marls with boulders of nummulitic limestones lie above, they must have formed in highly dynamic shallow marine conditions. The uppermost nummulitic limestones are the accumulations of large shells of benthic foraminifera driven to the bank by sea waves. It was concluded that the central part of the Simferopol Uplift was an island area until the end of the Early Ypresian. Its flooding caused the accumulation of coastal glauconite-rich sands, as well as carbonate sediments of the nummulitic bank at the later stages.

Keywords

• lower cretaceous
• eocene
• stratigraphic unconformity
• sedimentation environments
• foraminifera
• crimea
• simferopol uplift