Passing from the Upper Jurassic to the Lower Cretaceous in the Caucasus (Azerbaijan)

Problem of the transition from the Upper Jurassic to the Lower Cretaceous, and the character of subdivision of this stratigraphical interval in the Caucasus, have been often the subjects of studies of Mesozoic deposits in this area. To unequivocally solve the problem, it is necessary to analyze thoroughly the data from large geological regions, especially of the Azerbaijan part of the Caucasus. At the boundary of the Jurassic and Cretaceous there occurred the Cimmerian tectonic movements that resulted often in breaks in sedimentation. Their duration was different in particular areas of this Mediterranean Fold Belt. For these reasons we present the detailed data on the geological sections in the Caucasus in Azerbaijan, including the lithological character of the deposits and their faunal content. The Azerbaijan sections are representative of large parts of the Caucasus: the South East Caucasus (north slopes of the Greater Caucasus, and north-west of the south slopes of Greater Caucasus – these latter include also adjacent regions of Georgia), and the Lesser Caucasus in particular. The character of fauna, especially of ammonites, is very similar in all the regions studied. From the paleogeographical point of view the character of deposits shows that the large reconstruction of the basins took place at the turn of Tithonian and Berriasian. The Tithonian represents the regressive tendencies, whereas the Berriasian is transgressive. These features mark well the boundary between the Jurassic and Cretaceous systems.