Most of the Early Miocene deposits in the Northern Sperrgebiet accumulated in pre-Miocene valleys that drained into the Atlantic, but there are crater facies at Chalcedon Tafelberg and elsewhere in the region that may be the same age or slightly younger. All the aeolianites in the northern Sperrgebiet except for those at Buntfeldschuh, are post Early Miocene in age, in all cases lying unconformably on Early Miocene sediments. At the time of deposition of the Early Miocene sediments, the region was semi-arid, with savanna to steppe conditions, as shown by their pedogenic features. It became arid and eventually hyper-arid during the Middle Miocene, and it was from this time that the climate changed from a summer rainfall to a winter rainfall regime and aeolian deposition commenced.