Paleogeographic conditions of accumulation of Callovian and Oxfordian deposits of the Boloshnevo section (Ryazan region)

Abstract

Introduction: one of the easily accessible Callovian-Oxfordian sections of the Ryazan region, Boloshnevo, was studied by M. A. Rogov, who described the ammonite assemblage, identified substages, and proposed a zonal division. This outcrop was studied by I. N. Makarikhin from 2023 to 2025. Sedimentary rock and fossil samples were collected. The aim of this article was to interpret the paleogeographic history of the basin in this area, taking into account new data.

Results and Discussion: 1) a collection of 170 invertebrate fauna specimens was analyzed; 2) the formation conditions of the studied deposits were reconstructed.

Conclusions: 1. The paleontological characteristics of the section have been significantly expanded. In addition to the ammonites found by M.A. Rogov, other ammonites, belemnites, bivalves, gastropods were discovered.

1. Sedimentation conditions at the end of the Callovian age changed from extremely shallow water (up to 10 m) with active hydrodynamics to deeper water (30–40 m) with calm hydrodynamics.
2. During sediment accumulation, a current existed in the water column. Moreover, it passed through the immediate vicinity of the section under discussion during the accumulation of layers 2 and 4.