WÜRZBURGER GEOGRAPHISCHE ARBEITEN Mitteilungen der Geographischen Gesellschaft Würzburg Herausgeber: R. Baumhauer - B. Hahn - H. Job - H. Paeth - J. Rauh - B. Terhorst Heft 103 Jens Brauneck LATE QUATERNARY CLIMATE CHANGES IN THE CENTRAL SAHARA - New evidence from palaeoenvironmental research in NE-Niger 2010 Im Selbstverlag des Instituts für Geographie der Julius-Maximilians-Universität Würzburg in Verbindung mit der Geographischen Gesellschaft Würzburg Jens Brauneck LATE QUATERNARY CLIMATE CHANGES IN THE CENTRAL SAHARA - New evidence from palaeoenvironmental research in NE-Niger WÜRZBURGER GEOGRAPHISCHE ARBEITEN Herausgegeben vom Institut für Geographie der Universität Würzburg in Verbindung mit der Geographischen Gesellschaft Würzburg Herausgeber: R. Baumhauer – B. Hahn – H. Job Schriftleitung: B. Sponholz WÜRZBURGER GEOGRAPHISCHE ARBEITEN Mitteilungen der Geographischen Gesellschaft Würzburg Herausgeber: R. Baumhauer – B. Hahn – H. Job Heft 103 LATE QUATERNARY CLIMATE CHANGES IN THE CENTRAL SAHARA Jens Brauneck 2010 Im Selbstverlag des Instituts für Geographie der Julius-Maximilians-Universität Würzburg in Verbindung mit der Geographischen Gesellschaft Würzburg Computersatz: Jens Brauneck, Institut für Geographie der Julius-Maximilians-Universität Würzburg Druck: Bezug über den Buchhandel oder direkt bei: Institut für Geographie der Julius-Maximilians-Universität Würzburg – Würzburger Geographische Arbeiten – Am Hubland D-97074 Würzburg E-Mail: [email protected] URL: http://www.geographie.uni-wuerzburg.de/vortraege_schriftenreihen/ wuerzburger_geographische_arbeiten/ Zuschriften: Geographische Gesellschaft Würzburg c/o Institut für Geographie der Julius-Maximilians-Universität Würzburg Am Hubland D-97074 Würzburg © Institut für Geographie der Julius-Maximilians-Universität Würzburg ISSN ??????? CONTENTS List of figures…………………………………………………………………………..VI List of tables………………………………………………………………………….…V Preface……………………………………………………………………………..….VII Abstract……………………………………………………………….…………...…VIII Zusammenfassung………………………………………………………………….…..X 1 Introduction ............................................................................................................... 1 2 Geographical setting of the study area ...................................................................... 2 2.1 Geomorphology ............................................................................................................. 2 2.2 The geological framework ............................................................................................. 4 2.3 Vegetation ..................................................................................................................... 5 2.4 Present climatic dynamics of Northern Africa .............................................................. 6 2.5 Geographical setting of the study sites ........................................................................ 10 2.5.1 Seggedim ................................................................................................................ 10 2.5.2 Fabérgé depression ................................................................................................. 11 2.5.3 Enneri Achelouma / Seeterrassental ....................................................................... 13 2.5.4 Yoo Ango ............................................................................................................... 15 3 Sedimentary deposits as tools for environmental reconstruction ............................ 17 3.1 Physical sediment features .......................................................................................... 18 3.1.1 Visual description ................................................................................................... 19 3.1.2 Grain size ................................................................................................................ 20 3.1.3 Magnetic susceptibility ........................................................................................... 21 3.2 Sediment chemistry ..................................................................................................... 21 3.2.1 Organic carbon ....................................................................................................... 21 3.2.2 Silicon and aluminium ............................................................................................ 22 3.2.3 Iron and manganese ................................................................................................ 23 3.2.4 Alkali and alkaline earth metals ............................................................................. 23 3.3 Mineralogy .................................................................................................................. 23 3.3.1 Carbonates .............................................................................................................. 24 3.3.2 Evaporitic Minerals ................................................................................................ 25 3.3.3 Silicate minerals ..................................................................................................... 26 3.4 Biological Indicators ................................................................................................... 26 3.5 Archaeological findings .............................................................................................. 27 3.6 Age determination ....................................................................................................... 28 3.6.1 Radiocarbon dating ................................................................................................. 28 3.6.2 Optically stimulated luminescence (OSL) dating ................................................... 29 4 Palaeoenvironmental research on North African climate changes .......................... 30 4.1 Palaeoenvironmental reconstruction by proxy data ..................................................... 30 4.2 Review of palaeoenvironmental evidence from the central Sahara ............................. 36 4.2.1 Seggedim ................................................................................................................ 37 4.2.2 Falaise de Kaouar ................................................................................................... 37 4.2.3 Fachi ....................................................................................................................... 38 4.2.4 Zoo Baba ................................................................................................................ 38 4.2.5 Adrar Bous ............................................................................................................. 39 4.2.6 Ténéré ..................................................................................................................... 39 I 4.3 The issue of the Middle Terrace .................................................................................. 40 4.4 Computer-model-based investigations ......................................................................... 41 4.5 Summary ..................................................................................................................... 44 5 Materials and Methods ........................................................................................... 46 5.1 Fieldwork..................................................................................................................... 46 5.2 Laboratory methods ..................................................................................................... 47 5.2.1 Core handling and sample pre-treatment ................................................................ 47 5.2.2 Physical Methods .................................................................................................... 48 5.2.2.1 Sediment texture/grain-size analysis .................................................................. 48 5.2.2.2 Magnetic susceptibility ...................................................................................... 49 5.2.3 Geochemistry .......................................................................................................... 49 5.2.3.1 ICP-OES ............................................................................................................ 49 5.2.3.2 X-ray fluorescence spectrometry (XRF) ............................................................ 50 5.2.3.3 Fuse tablets (XRF) ............................................................................................. 50 5.2.3.4 Geoscanner (XRF) ............................................................................................. 51 5.2.3.5 Carbon analysis .................................................................................................. 51 5.2.3.6 pH measurement ................................................................................................ 52 5.2.4 Mineralogy.............................................................................................................. 52 5.2.4.1 XRD ................................................................................................................... 52 5.2.4.2 Thin sections ...................................................................................................... 53 5.2.5 Biological Indicators ............................................................................................... 53 5.2.5.1 Microfossils ......................................................................................................