Architecture of the Southern Marginal Zone of the Upper Jurassic–Valanginian Carbonate Platform of the Northeastern Caucasus (Dagestan, Shakhdag Massif)

Abstract

The structure of the southern marginal zone of the Upper Jurassic–Valanginian carbonate platform, Northeastern Caucasus, is considered with the Dagestan sector of the Shakhdag Massif as example. The massif consists of several large genetically diverse sedimentary complexes: (1) Upper Jurassic basal complex represented by the shallow-water terrigenous and carbonate sediments, which were formed under unstable sedimentation conditions; (2) reef complex ascribed to the barrier reef system; and (3) sedimentary sequence with the typical clinoform structure and the southwestward dip, toward the Dibrar trough. The formation of the marginal zone of the carbonate platform was mainly determined by (1) climatic conditions (transition from the humid climate in the Early and Middle Jurassic to the arid climate in the Late Jurassic) and (2) differences in the tectonic evolution of different structural-facies zones (weak subsidence of the Northeastern Caucasus, where carbonate platform was formed, and intense subsidence to the south in the flysch trough area). The formation of the internal structure of the Shakhdag Massif was mainly defined by the eustatic sea-level fluctuations.