New ichnological findings in Hauterivian sandstones of Mountainous Adygeya

Background. Trace fossils are highly informative objects for geological investigations. However, the information about their distribution in sedimentary settings lacks completeness. The conducted field studies of sandstones of the Hauterivian age in the northern part of Mountainous Adygeya (Western Caucasus) established, to the best of our knowledge, for the first time the presence of ichnofossils in one of their members.Aim. Characterization and interpretation of an ichnofossil assemblage from Hauterivian sandstones of Mountainous Adygeya.Materials and methods. Field investigations included in-situ search and documentation of ichnofossils, as well as their sampling. In the course of laboratory investigations, ichnofossils were interpreted; bioturbation and ichnofacies were evaluated. In addition, petrographical and XRD methods were used to analyze the matter that fills the most widespread traces.Results. The established ichnofossils are distinguished by a low diversity. They can be identified as Ophiomorpha isp., ?Ophiomorpha isp., Skolithos isp., ?Taenidium isp. The latter species, although occurring most commonly, are least clear and hard to identify. Bioturbation is weak, although increasing in particular loci. The ichnofacial interpretation is uncertain due to the coexistence of elements typical of the Scoyenia and Scolithos ichnofacies.Discussion. The studied ichnofossils indicate the activity of shrimps, insects, and worms both on the surface and inside the sediment. The latter accumulated under the conditions of a subaerial part of the river delta near its stream section. Apparently, in the Hauterivian Stage, the area under study was represented by a land mass.Conclusion. The results obtained during the conducted ichnological study of Hauterivian sandstones of Mountainous Adygeya are not only interesting per se, but also serve as an important indicator of sedimentation environments.

bioturbation, deltas, trace fossils, sedimentation environments, Lower Cretaceous, Gubs Formation, Western Caucasus