The greater part of Bechuanaland is covered with superficial deposits consisting of the sands of the desert regions of the Kalahari and the alluvium and saliferous marls of the Okavango basin.
There are ampler expanses of hard saliferous clay (shor) and on the north side of the desert of Lop the surface has been carved and sculptured by the wind into innumerable flat, tabletopped masses (jardangs) with vertical or even overhanging sides, separated from one another by deep-cut, wind-swept gullies, running from north-east to south-west.
In the former case it is often difficult to obtain the brine at a density even approaching saturation, and chambers and galleries are sometimes excavated within the saliferous beds to increase the dissolving surface, and water let down fresh is pumped up as brine.
Thus the lower Eocene has some lignite in the eastern Gulf region, while in Teias lignite and saliferous and gypsiferous sediments are found, though most of the system is marine and of shallow water origin.
The gypsiferous and saliferous marls of Shellata, Suk Ahras and Ain Nussi have yielded Triassic fossils.