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  Sedimentary and geomorphic evidence of Saharan megalakes: a synthesis

Drake, N. A., Candy, I., Breeze, P., Armitage, S., Gasmi, N., Schwenninger, J., et al. (2022). Sedimentary and geomorphic evidence of Saharan megalakes: a synthesis. Quaternary Science Reviews, 276: 107318. doi:10.1016/j.quascirev.2021.107318.

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 Creators:
Drake, Nick A.1, Author              
Candy, I., Author
Breeze, P., Author
Armitage, S.J., Author
Gasmi, N., Author
Schwenninger, J.L., Author
Peat, D., Author
Manning, K., Author
Affiliations:
1Archaeology, Max Planck Institute for the Science of Human History, Max Planck Society, ou_2074312              

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Free keywords: Sahara desert, Megalake, Remote sensing, Digital elevation model, Sedimentology, Shorelines
 Abstract: It has long been recognised that the Sahara Desert contains sediment, landform and palaeoecological evidence for phases of increased humidity during the Quaternary period. Many authors have also suggested that during some of these humid periods very large lakes, termed megalakes, developed in several basins within the Sahara. Recent work has questioned their existence. In particular it has been argued that the lack of well-developed and spatially extensive shorelines in these basins suggests that discrete groundwater and spring deposits have been misinterpreted as evidence for megalakes. In this paper we re-evaluate the evidence used to identify megalakes. Firstly, we apply a comprehensive remote sensing and GIS analyses to the megalake shorelines, their catchments and the wider Sahara. This not only supports the previously proposed existence of numerous megalakes, but also indicates a previously unrecognised megalake in the Niger Inland Delta region, here named Megalake Timbuktu. Secondly, we review the geomorphic and sedimentary evidence for the megalakes, highlighting the importance of the sedimentary record in identifying lake highstands, particularly through the example of the Chotts Megalake in southern Tunisia where we provide new sedimentary information on lake shorelines. This analysis demonstrates that in much of the Sahara the dynamic aeolian systems preclude the preservation of well-developed shorelines, but the distribution of fragmented geomorphic features and localised lake deposits provide robust evidence for Quaternary megalake formation. The paper concludes by highlighting that although extensive evidence for Saharan megalake formation exists, the current chronology of lake highstands indicates that the vast majority date to Marine Isotope Stage (MIS) 5 or earlier. Only megalakes Chad and Timbuktu, which derive much of their water from outside the desert, show evidence for Holocene (African Humid Period or AHP) shorelines. The AHP record of the other megalakes indicate the existence of much smaller water bodies than those that developed earlier in the Pleistocene indicating that it was significantly drier than these earlier humid phases.

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Language(s): eng - English
 Dates: 2021-12-172022-01-15
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: 1. Introduction
2. Megalakes in the Sahara – current ideas and understanding
2.1. Megalake Chad
2.2. Megalake Chotts
2.3. Lake Megafezzan
2.4. Megalake Darfur
2.5. Megalake Ahnet-Mouydir
2.6. Megalakes along the River Nile
3. Saharan Megalakes – myth or reality?
4. Geomorphological and sedimentary evidence for Saharan Megalakes
4.1. Geomorphic evidence for shoreline features
4.2. Remote sensing and DEM analysis of shoreline features
4.3. Evaluation of megalake geomorphology
4.3.1. Megalake Chad and Darfur
4.3.2. Megalakes along the River Nile
4.3.3. Megalake Timbuktu
4.3.4. Confidence estimation for remote sensing and DEM analysis of megalake geomorphology
4.4. Sedimentary evidence for Saharan Megalakes
5. Catchment mapping and rainfall estimation
6. Chronological evidence for the timing of megalake development
7. Summary and conclusions
 Rev. Type: Peer
 Identifiers: DOI: 10.1016/j.quascirev.2021.107318
Other: shh3113
 Degree: -

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Title: Quaternary Science Reviews
Source Genre: Journal
 Creator(s):
Affiliations:
Publ. Info: Oxford : Pergamon
Pages: - Volume / Issue: 276 Sequence Number: 107318 Start / End Page: - Identifier: ISSN: 0277-3791
CoNE: https://pure.mpg.de/cone/journals/resource/954925505268