One of the Most Famous Fossil-Bearing Localities in Russia
The Lower Cretaceous sediments exposed here are assigned to the Zaza Formation and represented by beds with the total thickness of about 70 meters. The fossil-bearing deposits are represented by conglomerates with occasional shell and siltstone beds, bituminous black shales and cyclically alternating fine-grained sandstones, siltstones, and marls.
The collection of insects from Baissa includes now more than 20 000 specimens. Insect remains occur throughout the section except for the most coarse-grained beds but their abundance and the state of preservation vary strongly from layer to layer and even within the same bed. Well-preserved insect fossils are mostly restricted to fine laminated marl beds or marl boulders in conglomerates, whereas their remains are always in a poor condition in bituminous shales, although they may be occasionally abundant there.