The Sahara in the Holocene: Sahara.readme file --------------------------------------------------------------- World Data Center A- Paleoclimatology --------------------------------------------------------------- NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!! NAME OF DATA SET: The Sahara in the Holocene LAST UPDATE: 01-01-1994 EDITOR & CONTRIBUTOR: Dr. N. Petit-Maire, CNRS, Marseille Assistant Editors: N. Page, P. Laforest, CNRS, Marseille IGBP PAGES/WDCA Data Contribution Series #: 94-002 SUGGESTED DATA CITATION: Petit-Maire, N., 1994, The Sahara in the Holocene. IGBP PAGES/World Data Center-A for Paleoclimatology Data Contribution Series # 94-002. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCES: Petit-Maire, N., 1990. Will Greenhouse green the Sahara? Episodes, vol. 13, No. 2: 103-107. Petit-Maire, N., M. Fontugne, and C. Rouland, 1991. Atmospheric methane ratio and environmental changes in the Sahara and the Sahel during the last 130 kyrs. Palaeogeography, Palaeoclimatology, and Palaeoecology, 86: 197-204. Petit-Maire, N., N. Page, and J. Marchand, 1993. The Sahara in the Holocene. Map, 1/5,000,000 Scale. UNESCO and CGMW. Paris. GEOGRAPHIC REGION: Northern Africa PERIOD OF RECORD: Holocene, approximately 10,000 - 2,000 YBP LIST OF FILES: SAHARA.csv (comma delimited ASCII) , SAHARA.txt (tab-delimited ASCII), SAHARA.DOC (notes on methodology and compilation, plus bibliography), README. DESCRIPTION: The data set consists of over 2000 radiocarbon dates from a variety of organic and mineral deposits in the Sahara Desert region of northern Africa. Most are from the earlier compilation of R. Vernet (1991) (Please see SAHARA.DOC for complete bibliography). Most specimens are freshwater mollusc shells from paleolacustrine deposits, terrestrial mollusc shells from paleosols, wood, large mammalian bones, or human bones and charcoal from neolithic sites, all of which are indicative of Holocene climatic conditions in northern Africa significantly wetter than the current hyperarid environment. The age range of the data base spans most of the Holocene, from approximately 10,000 to 2,000 Years Before Present. The World Data Center distributes the numerical data tables in ASCII and Microsoft Excel formats. The results are also available in the form of a color wall map illustrating locations, dates, and types of macrofossil sample. The map, titled "The Sahara in the Holocene", is available from CGMW, 77 Rue C. Bernard, 75005 Paris, or from UNESCO, Division of Earth Sciences, 1 rue Miollis, 75015 Paris. TEXT of SAHARA.DOC: THE SAHARA IN THE HOLOCENE Numerous multidisciplinary field research were conducted in the Sahara desert during the last decade by international scientists, mainly members of UNESCO-IUGS IGCP 252. The (Holocene) last warm climatic optimum has been particularly well studied in the frame of more than 2000 radiocarbon dates on palaeolacustrine and other proxy data, bringing evidence to a totally different environment relative to the extant one. The Saharo-Sahelian boundary was then located 500 km to the North of its present position (22oN, now 17oN). A vast surface was covered with swamps or lakes and a sahelian grassland was inhabited by the large mammalian fauna now found in the Sahel. Neolithic man lived a sedentary life in this favourable biotope. These results correspond to several hundred publications in english, french, german, and to several specialized volumes. The paleogeographical map summarizes those results for the most significant part of extant Sahara: its hyperarid core extending to the North and South of the Tropic of Cancer, between the 100 mm isohyets. This area covers about 9 million km2 from the Atlantic to the Red Sea. Its extreme aridity is due to the very low ratio between Precipitation (ranging from 100 mm to less than 5 mm) and the potential Evaporation (about 6 m). Nowadays, quasiabiotic environ- mental situations occur locally. The map thus represents the consequences of the last global warming relative to a present extreme climatic situation. Scale. A 1/5,000.000 scale was chosen for practical reasons: - covering the whole area in one sheet, allowing a visual overview. - use the already existing IGN backgrounds for relief and hydrography. They fit, since relief and rivers systems have not significantly changed in such a short geological time (10 millennia), although it has to be emphasized that the wadis extant dry or underflow courses (shown on the map as dashed lines) flowed seasonally during the Holocene, as evidenced by geomorphological features. Time scale. The Holocene s.s, from 10 ka(end of the Younger Dryas short cooling between the two deglaciation steps) to 2 ka ("saharisation" of the whole area). Data. - Only radiocarbon dated information have been positioned on the map (which eliminates a good number of observations, most of them from literature prior to 1970). They represent 1890 selected data. - Those data correspond to proxy markers for humidity, implying local precipitation or aquifer rise: . surface water: lakes, swamps(generally dated from freshwater mollusks shells). . dissolution processes: calcretes, travertines. . vegetal cover: organic matter and paleosols, pollen, charcoal. . large mammalian fauna implying both fresh water accessibility and a grassland cover (elephant, rhinoceros, antelopes, etc..) or even a wooded grassland (giraffe). . prehistoric habitats: archaeological sites, burials and artifacts, also implying possibility of sedentary or semi-sedentary life, i,e accessible water and food (game, vegetals). - Most data are adapted from R. Vernet and G. Aumassip's compilation (1991) with substantial additional items from the following: Bathily M. 1993. Neolithique moyen a final littoral et continental d'un secteur saharien: Le Nord-Ouest mauritanien. These Univ. Paris 1. Baumhauer, R., Schulz E. 1984. The Holocene lake of Seguedine, Kaouar, NE Niger. Palaoecology of Africa 16:283-291. Callot, Y., Fontugne M. 1992. Les etagements des nappes dans les paleolacs holocenes du N-E du Grand Erg Occidental (Algerie). C.R. Acad.Sci.Paris, 315, II,:471 Commelin D., Petit Maire N., Casanova J. 1980 Chronologie isotopique saharienne pour les derniers 10,000 ans. Essai d'interpretation: migrations humaines et paleoclimatologie. Bull.Mus.Anthrop. Monaco, 23:37. Commelin D., Raimbault M., Salege J.F..(in press). Nouvelles donnees sur la chronologie du Neolithique au Sahara malien. C.R.Acad.Sci.,Paris). Durand A. 1993. Enregistrement sedimentaire de la dynamique climatique au Quaternaire superieur dans le Sahel central (Niger et Tchad). These, Univ. Bourgogne, 580p. Fontes, J.C., Andrews J.N., Edmunds W.M., Guerre A., Travis Y. 1991 Geochemical evaluation of groundwater evolution and recharges in arid areas: The Azzaouad depression of northern Mali. Water Resour. Res., 27,2. Haaland R., Magid A.A. 1992. Radiocarbon dates from Mesolithic sites in the Athara region, Sudan. Nyame Akuma, 37:17. Haynes C.V., Eyles C.H., Pavliszh L.A., Ritchie J.C., Rybak M. 1989. Holocene paleoecology of the eastern Sahara; Selima oasis. Quaternary Sci. Reviews 8:109-136. Kuper R. (Ed.) 1989. Forshungen zur umweltgerschichte der Ostshara. Africa Praehistorica 2, Henrich-Barth Inst. Koln, 339p. Lezine A.M. 1993. Chemchane, histoire d'une sebkha. Secheresse 4:25-30. Lezine A.M., Casanova J., Hillaire-Marcel C. 1990. Across an early holocene humid phase in western Sahara, pollen and isotope stratigraphy. Geology 18:264-267. Miller G.H., Wendorf F., Ernst R., Schild R., Close A.E., Friedman I., Schwarcz, H.P. 1991. Dating lacustrine episodes in the Eastern Sahara by the epimerization of isolencine in Ostrich shells. Paleo.3, 84-175. Neumann K., Schulz E. 1987 Middle holocene savanna vegetation in the central Sahara. Preliminary report. Palaeoecology of Africa 18:163-166. Neumann K. 1988. Die Bedeutung von Holzohleuntersuchungen fur Vegetationgeshichte derr Sahara. Das Belspiel Fachi-Niger. Wursb. Geogr. Arb 69:71-85 Neumann K. 1989. Vegetationgeschichte der Ostsahara im Holozan aus prashistorischen Fundstellen. In: Kuper R (Ed.) Forshungen zur Umweltgeschichte der Ostsahara. Henrich-Bart Inst. Koln, Africa Praehistorica 2:13. Neumann K. 1989. Holocene vegetation of the eastern Sahara- charcoal from Prehistoric sites. African archeological review 7:97-116. Pachur H.J., Kropelin S., Hoelzmann P., Goschin M., Altmann N., 1990. Late Quaternary fluvio-lacustrine environments of Western Nubia. Berliner geowiss, Abh., A, 120.1:203. Pachur H.J., Hoelzmann P., Paleoclimatic implications on late Quaternary lacustrine sediments in Western Nubia, Sudan. Quaternary Research, 35/3:252. Petit-Maire N., Riser J. 1983. Sahara ou Sahel? Quaternaire recent du Bassin de Taoudenni (Mali). Marseille Impr. Lamy, 473p. Petit-Maire N., Riser J. 1988. Le Sahara a l'Holocene: Mali. CCGM Paris, 1988 - 1 carte au 1,000,000 Petit-Maire N., Commelin D., Fabre J., Fontugue M. 1990. First evidence for Holocene rainfall in the Tanezrouft hyperdesert and its margins. Paleo 3., 79:333. Petit-Maire N. (ED.) 1991. Paleoenvironements du Sahara. Lacs holocenes a Taoudenni (Mali). CNRS Parisd, 239p. Petit-Maire N., Burollet P.F., Ballais J.L., Fontugne M., Rosso J.C., Lazaar A. 1991. Paleoclimats holocenes du Sahara septentrional. Depots lacustres et terrasses alluviales en bordure du Grand Erg Oriental a l'extreme Sud de la Tunisie. C.R. Acad.Sci.Paris, 312, II: 1661. Petit-Maire N., Fontugne M., Rouland C. 1991 Atmospheric methans ratio and environmental champs in the Sahara and Sahel during the last 130 kyrs., Paleo 3,86:197- 204. Raimbault M., Dutour O. 1990. Decouverte de populations mechtoides dans le Neolithique du Sahel malien (gisement lacustre de Kobadi); implications paleoclimatiques et paleoanthropologiques C.R. Acad.Sci.Paris, 310-631. Ritchie J.C., Eyles C.H. Haynes C.V. 1985. Sediment and pollen evidence for an early mid-holocene humid period in the eastern Sahara. Nature 314:352-355. Ritchie J.C. 1987 A holocene pollen record from Bir Atrun. northwest Sudan. Pollen et Spores 29, 4:391-410 Ritchie J.C., Haynes C.V. 1987 Holocene vegetation zonation in the eastern Sahara. Nature 330:645-647 Riser J. 1992. Le plateau du Tagant et le massif du Tamaga entre Sahel et Sahara 115o. Congr.Nat.Soc.Sav. Avignon 1990, Geologie africaine: 125. Schulz E. 1987. Die Holozane vegetation der zentalen Sahara (N Mali, N Niger, SW Libyen). Palaeoecology of Africa 18:1243-161. Schulz E., Joseph A., Baumhauer R., Schultze E., Sponholz B., 1990. Upper Pleistocene and Holocene history of the Bilma region (Kawar, NE Niger). Proc 15 Coll.African Geology. 281-284. Vernet R. Et Aumassip G. 1991. Le Sahara et ses marges. Paleoenvironnements et occupation humaine a l'Holocene. Inventaire des Datations 14C (1ere edition jusqu'en 1989). Univ. Niamey, CNRS Paris G 0848, 107P (bibliogr. exhaustive:305 references).. Wendorf F., Schild R., Close A E., Hillman G G., Gautier A., Van Neer W., Donahue D.J., Jull A.S.T., Linick J.W. 1988 New radiocarbon dates and Late Palaeolithic diet at Wadi Kubbaniya, Egypt. Antiquity, 62:279-283. Wendorf F., Close A.E., Shild R., Wasylikowa K. 1991 The combined Prehistoric Expedition. Results of the 1990 and 1991 seasons, Newsletter of Amer.Res.Center in Egypt, no154, 8p. Wendorf F., Close A.E., Schild R.,Wasylikowa K., Housley, R.A., Harlan J.R., Krolik H. 1992. Saharan exploitation of plants 8,000 years B.P., Nature, vol.359, no6397:721. Wendorf F. 1992. The impact of radiocarbon dating on north African archaeology. In: R.E. Taylor, A long, R.S. Kra Edit. Radiocarbon after four decades, Springer Verlag, 309-323. - The 14C ages for each local cluster of data are shown in pie-diagrams indicating the range and the number of dates. - The data base corresponding to the map has been communicated to Dr. R. Webb, NOAA National Geophysical Data Center, Boulder, CO. USA As can be expected, such a small scale map lacks precision and the surfaces covered by the symbols are obviously inexact. In many cases, several sites had to be grouped into one symbol. However, such a synthetic representation is quite fit for validating Global Circulation Models, (GCM's) generally produced at such small scale. The map provides a full picture of a climatically homogeneous vast area, during the warm peak of our interglacial: it thus may allow a better understanding of a regional past climatic change, to be related with the global changes recorded in ice or ocean deep cores.