Lithofacies and paleoenvironmental analysis of the Upper Cretaceous successions: Yagaan Khovil fossil locality, central Gobi region, Mongolia

The Upper Cretaceous successions are exposed at the Yagaan Khovil fossil locality in the central Gobi region, Mongolia. The successions comprise fluvial deposits that are divided into two units based on the lithological characteristics of the floodplain deposits. The lower unit (Unit 1) is characterized by eolian-influenced environments, whereas the upper unit (Unit 2) is composed predominantly of meandering river systems with lateral accretionary channel fill deposits that show concretion at the top of the bed. The shift in depositional processes from the lower to the upper unit can be hypothesized as the result of the change in the proximity of the eolian-affected area to the study area. The successions preserving the similar paleoenvironmental transition are also present in the Nemegt Basin, where the successions shift from reddish mud beds affected by eolian processes to meandering fluvial successions. Additionally, to the similar sedimentological features, similarities in vertebrate fossils between Yagaan Khovil and the formations in the Nemegt Basin imply the close relationship between the two areas in terms of environmental conditions, ages, and stratigraphic positions. To enhance the stratigraphic framework of the Upper Cretaceous strata in Mongolia, future work should integrate the findings of this study with new radiometric dating techniques.