The lower portions of the formation are composed of yellow conglomerate, with the higher areas being dominated by red clays, silts and sands, as well as lava and basalt flows.

[1] The Hsanda Gol levels rest directly over, and are continuous with the earlier Houldjin Gravels which are sometimes counted as part of the formation, but were rather deposited during the latest Eocene under wetter and more energetic conditions.

In general, the Houldjin Gravels and the Hsanda Gol formation show a transition from more humid, forested conditions to an arid climate with presence of dunes and ephemeral rivers.

Some taxa lived through this change including hyaenodonts and indricotheres, but others, such as brontotheres, amynodonts, rhinocerotids and entelodonts went extinct and are as a result absent from Hsanda Gol proper.

It is composed largely of rodents and lagomorphs with high-crowned teeth adapted to chew hard vegetation; several of these species are fossorial and none arboreal, indicating that there were no areas with high tree density.