Geomorphological investigations at Mochena Borago rock shelter, Ethiopia
During the last decade archaeological analyses helped to gain insight into the history of settlement of the rock shelter in the last 50 ka. Element and micromorphological analyses as well as computer-supported large scale investigations for sediment sources and transport into the rock shelter itself were carried out to understand the depositional history of Mochena Borago. The arrangement of excavation sites gives a rough overview of the stratigraphic setting, whereas the uneven distribution of the test pits leaves gaps regarding available information on the subsurface.
The trenches show interlaced deposits of volcanic and clastic origin, which are now – to some degree – put in a depositional sequence. The unconsolidated sediments show a sequence of paleo-surfaces, as well as indications for local continuous sedimentation and spontaneous mass movements. Furthermore, indications for humid periods with high sedimentation rates are found which contrast to low sedimentation rates resulting from climatic and/ or morpho-logical changes at the site. Especially common in protected areas within the rock shelter are relicts of Homo sapiens, which are associated with sediment accumulation in the northern part of the cave. The southern part shows high energy erosion through fluvial processes which are also related to the morphological structure of the rock shelter itself and erosion features within the subsurface.
Due to existing high erosion features, it is likely that sediments with archaeological findings have been removed from the cave. This has to be taken into account, because an earlier occupation at Mochena Borago is possible. Further geomorphological investigations for the cave are in progress.