Delineation of the Paleo-Lake Manyara in Northern Tanzania using Terrain Analysis, Radar- and Multispectral Remote Sensing

Felix Bachofer ^a, Geraldine Quénéhervé ^a, Michael Märker ^b, Volker Hochschild ^a

^a Institute of Geography, University of Tübingen
^b Heidelberg Academy of Sciences and Humanities                       

The surroundings of Lake Manyara in the East African Rift System were in the focus of several paleo-archaeological investigations. Its location is close to Olduvai Gorge where paleo-anthropological findings can be traced back to the homo habilis. In the catchment of Lake Manyara, especially close to the village of Makuyuni, two hominin-bearing sites (0.63 and 0.78 Ma), lots of vertebrate fossils and handaxes from different periods were found. All findings contribute to the knowledge of human evolution and expansion. For a better integration of these discoveries, a better understanding of the paleo-environment in the region is necessary. Therefore, the development and extent of the lake with several transgression and regression sequences is crucial.

Based on RADAR-Remote Sensing analysis a broad range of paleo-shorelines were detected. Therefore, ALOS PALSAR (HH/HV) and TerraSAR-X StripMap (HH) scenes were processed. While the paleo-shorelines are hardly noticeable in optical remote sensing images, they are highlighted by their intense backscatter due to their shape, alignment and texture in radar scenes. A Canny Edge detector was applied using a Python-script to extract the linear features and terraces. Such linear features have been detected up to 20 km east of today’s shoreline. Samples were taken in the field from stromatolites which were found on these paleo-shorelines indicating paleo-water levels.

A combination of DEM-analysis and multispectral band rationing techniques allows to extract the maximum outcropping extent of the Lower Manyara Beds. Hence, the maximum lake level located more than 27 km west of today’s shoreline was identified. Radar images proofed to be useful in detecting paleo-forms which could not be delineated in detail by optical remote sensing. Finally, a better understanding of the former paleo landscape and landscape connectivities are provided.