Obukhov Formation

The Obukhov Formation is a geologic formation in Belarus and Ukraine that dates to the Late Eocene;^[1] the Obukhov Formation is equivalent to the Prussian Formation of Russia.

Obukhov Formation
Stratigraphic range: Late Eocene PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Underlies	Mezhigorje Formation
Overlies	Early Eocene Basement
Thickness	2–7 m (6.6–23.0 ft)
Lithology
Other	Sand, Clay, Amber, Glauconite, Quartz
Location
Location	Ukrainian Crystalline Shield
Region	Belarus (Gomel Region) Ukraine (Rivne Oblast)

Rovno amber is found in this formation,^[2] and 90% of amber collected from the Obukhov Formation is extracted illegally and the trade is controlled by armed organised crime groups, although the Ukrainian government has begun to oversee excavations since 1993.^[2]

Geological context

The Late Eocene Rovno amber is hosted in the Obukhov Formation, and it underlies the Early Oligocene Mezhigorje Formation.^[3][2] The formation is found along the northwestern margin of the Ukrainian Crystalline Shield^[1] exposed in the Rivne region of Ukraine and across the border near Rechitsa in the Gomel Region of Belarus.^[4] The granite basement rock was overlain by sandy to clayey deposits that were host to alluvial amber.^[2]

The two formations total between 2–7 m (6.6–23.0 ft) in thickness, both containing interbeds or mixtures of brown coals and carbonized vegetation. Both formations are sandy to clayey in texture, with the Obukhov Formation having more clayey glauconite-quartz plus sandy loess.^[5]