Chapter 30 The Khubsugul Group, Northern Mongolia

Abstract

AbstractThe Khubsugul Group of northern Mongolia contains diamictites in the Ongoluk and Khesen formations that are succeeded by a stratiform phosphorite deposit and >2 km of early Cambrian dolomite. The stratigraphy of the Khubsugul Group, including the two diamictites, can be correlated with that of the Dzabkhan platform in southern Mongolia. By correlation, the Ongoluk diamictite is an early Cryogenian glacial deposit. A glaciogenic origin is inferred from the presence of striated clasts and bed-penetrating dropstones. The younger Khesen diamictite consists predominantly of a massive carbonate-clast diamictite, but also contains bed-penetrating dropstones in rare stratified facies, and is inferred to be end Cryogenian in age. The two diamictites are separated by as much as 250 m of allodapic carbonate. The phosphorite in the upper Khesen Formation (Fm.) is likely latest Ediacaran to early Cambrian in age and is separated from the glacial deposits by a major hiatus. Consequently, no links can be made between the phosphogenesis and the glacial deposits. Only limited geochemical, geochronological and palaeomagnetic results from the Khubsugul basin have been reported to date, but work is ongoing and there is strong potential for future studies.