Geology of South Sudan
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The geology of South Sudan is founded on Precambrian igneous and metamorphic rocks, that cover 40 percent of the country's surface and underlie other rock units. The region was affected by the Pan-African orogeny in the Neoproterozoic and extensional tectonics in the Mesozoic that deposited very thick oil-bearing sedimentary sequences in rift basins. Younger basalts, sandstones and sediments formed in the last 66 million years of the Cenozoic. The discovery of oil in 1975 was a major factor in the Second Sudanese Civil War, leading up to independence in 2011. The country also has gold, copper, cobalt, zinc, iron, marble, limestone and dolomite.
The oldest rocks in South Sudan are Precambrian gneiss, metasediments and basic volcanics that form the igneous and metamorphic basement rock that underlies the country and is exposed as 40 percent of its surface. Some Precambrian rocks may be well over two billion years old. However, in most cases they were reactivated and altered in the Neoproterozoic Pan-African orogeny.
Northwest South Sudan has the Mesozoic Cretaceous Nubian sandstone overlying basement rock. Much of northern South Sudan is underlain by deep, oil-bearing rift basins, with sedimentary rocks up 13.7 kilometers thick. Lacustrine shales, claystones, sandstones and conglomerates formed in the Jurassic and Cretaceous. Alluvial sediments formed in the past 2.5 million years of the Quaternary flank major rivers in the north, center and east. The Cenozoic Um Ruwaba Formation covers most of central and eastern South Sudan and basalt, also from the Cenozoic occurs close to the border with Ethiopia.[1][2]
