Formation Member Period Notes Nubia Formation Holocene [1] Abu Imama Formation Middle Miocene [2] Wadi Milk Formation Wadi Abu Hashim Campanian-Maastrichtian [3] Shendi Formation Campanian [4] Wadi Howar Formation Coniacian-Santonian [5] Abu Agag Formation Turonian [6] Bentiu Formation Barremian-Cenomanian [7] Abu Gabra Formation Barremian-Aptian [8]