U-Shaped spreiten-burrows filled by pellets in the Bathonian of the Saratov region and their significance for reconstruction of sedimentary environments

In the lower half of the Bathonian Kamenny Ovrag Formation of the Saratov region (the left-bank of the River Volga area), that is represented by the interbedding of light-gray clays and grayish-white soft siltstones, and characterized by rare foraminifers Ammodiscus baticus, we observed the 5-metre interval that has been intensively reworked by U-shaped spreiten burrows filled by Coprulus oblongus pellets and fine-grained silt material. The interval is contrasted markedly with lack of bioturbation in the adjacent sediment. Morphology and specific filling of the burrows are similar to Rizocorallium commune. It differs by subvertical orientation, absence of marginal tubes, and uniformly small size. Taking into account sedimentological and palynological data this monospecific association of trace fossils can be considered as occupying the tidal flat depositional environment