Phenomena of underwater landslides in the Senonian deposits of Dagestan

Abstract

When mapping in Mountainous Dagestan in the summer of 1937, in the Upper Cretaceous deposits, I observed horizons of crushed rocks among quietly lying sediments. These horizons, as well as the underlying and covering rocks, are represented by light, strong, layered limestones, characteristic of the Senonian deposits of Dagestan. Small domes composed of Upper Cretaceous rocks among Tertiary sediments are observed near the villages. Gubden, then in the north of the region - the dome of Maraulark and to the north of it - the dome of Eldam. The region of interest to us is transitional from the area of development of normal folding to the area where dome-shaped structures appear. Apparently, dome formation also occurred here in the Upper Cretaceous, but the dome-shaped structures that appeared were obscured by subsequent folding. At the same time, it is quite natural to assume that during folding, the anticlinal folds were located corresponding to these domes. Indeed, against the background of elongated anticlinal folds, we often observe dome-shaped uplifts. This situation fits very well with the general picture of the distribution of landslide breccias in the study area. It is characteristic that everywhere landslide breccias are confined to synclinal zones and are absent in the crests of anticlines (against the background of a general synclinal fold). In the arches of anticlines, a sort of loss of horizons and local unconformity are sometimes observed. It is very likely that these domes were the uplifts along whose slopes the movement of sediments occurred.