 The underlying rocks of the West African craton are covered in the northwest by sediments of the Taoudeni basin, with two main outcrops of crystalline rocks in the northern Reguibat shield in Mauritania and the southern Leo shield which includes the Bougouni and Kenieba outcrops, both of which contain valuable minerals.There may also be petroleum reserves in the Taoudeni basin.Mali shares a total of 7,243 kilometers (4,500 miles) of land boundaries with seven bordering states