A new anomalous section of the Bazhenov formation was described on the territory of the Urengoydeposit in the northern part of Western Siberia. This article presents descriptions of mesostructural complexes in the core, on the basis of which a new model for the formation of the anomalous section of the Bazhenov formation was proposed. It was found that the formation of the mesostructural complexes occurred at different stages of the landslide and when its body moved along the uneven surface of the detachment. In the formation of large injection “sand veins” in the studied section, the main role was probably played by the landslide-induced grain flow from the coastal shallow water area. The penetration of its sandy material into the rocks of the Bazhenov formation and, to a lesser extent, the Achimov formation occurred due to the energy of hydraulic shock and hydraulic fracturing along layer-by-layer and secant fractures.