The University of Manchester Research Quaternary Glaciations of the Atlas Mountains, North Africa DOI: 10.1016/B978-0-444-53447-7.00076-3 Link to publication record in Manchester Research Explorer Citation for published version (APA): Hughes, P. D., Fenton, C. R., & Gibbard, P. L. (2011). Quaternary Glaciations of the Atlas Mountains, North Africa. In Developments in Quaternary Science|Dev. Quat. Sci. (Vol. 15, pp. 1065-1074). Elsevier BV. https://doi.org/10.1016/B978-0-444-53447-7.00076-3 Published in: Developments in Quaternary Science|Dev. Quat. Sci. Citing this paper Please note that where the full-text provided on Manchester Research Explorer is the Author Accepted Manuscript or Proof version this may differ from the final Published version. If citing, it is advised that you check and use the publisher's definitive version. 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This chapter was originally published in the book Developments in Quaternary Science, Vol.15, published by Elsevier, and the attached copy is provided by Elsevier for the author's benefit and for the benefit of the author's institution, for non- commercial research and educational use including without limitation use in instruction at your institution, sending it to specific colleagues who know you, and providing a copy to your institution’s administrator. All other uses, reproduction and distribution, including without limitation commercial reprints, selling or licensing copies or access, or posting on open internet sites, your personal or institution’s website or repository, are prohibited. For exceptions, permission may be sought for such use through Elsevier's permissions site at: http://www.elsevier.com/locate/permissionusematerial From: Philip D. Hughes, C.R. Fenton and Philip L. Gibbard, Quaternary Glaciations of the Atlas Mountains, North Africa. In J. Ehlers, P.L. Gibbard and P.D. Hughes, editors: Developments in Quaternary Science, Vol. 15, Amsterdam, The Netherlands, 2011, pp. 1065-1074. ISBN: 978-0-444-53447-7. © Copyright 2011 Elsevier B.V. Elsevier. Author's personal copy Chapter 76 Quaternary Glaciations of the Atlas Mountains, North Africa Philip D. Hughes1,*, C.R. Fenton2 and Philip L. Gibbard3 1Quaternary and Geoarchaeology Research Group, Geography, School of Environment and Development, The University of Manchester, Manchester M13 9PL, United Kingdom 2NERC Cosmogenic Isotope Analysis Facility, Scottish Universities Environmental Research Centre, Scottish Enterprise Technology Park, Rankine Avenue, East Kilbride, Glasgow G75 OQF, United Kingdom 3Cambridge Quaternary, Department of Geography, Downing Place, University of Cambridge, Cambridge CB2 3EN, United Kingdom *Correspondence and requests for materials should be addressed to Philip D. Hughes. E-mail: [email protected] 76.1. INTRODUCTION no modern glaciers exist although periglacial activity is thought to be still active above 2000 m (Couvreur, 1966; The Atlas Mountains contain the highest mountains of Robinson and Williams, 1992). North Africa and some of the highest mountains that sur- Climatically,theAtlasMountainsexperiencehumidcon- round the Mediterranean basin, several of which exceed ditions in the northern section bordering the Mediterranean 4000 m a.s.l. The mountains stretch over 1500 km from Sea and progressively drier conditions towards the south- central Morocco to northern Tunisia and are commonly west. The climate is strongly seasonal with dry summers subdivided into the High, Middle and Saharan Atlas and precipitation in winter (Delannoy, 1971). In the north, (Fig. 76.1). The mountain chain is situated at the Africa– inregionsborderingtheMediterranean,suchastheDjurdjura Eurasia plate boundary and has been uplifted and deformed massif in the Greater Kabylie area of the Algerian Tell, pre- together with its Palaeozoic basement, during the Mesozoic cipitation exceeds 2000 mm (Vita-Finzi, 1969, p. 54). At and Cenozoic. The highest peaks are formed in Palaeozoic Ifrane, in the Middle Atlas, Morocco, mean annual precipi- basement granites and extrusive lavas such as basalt, andes- tation(1961–1990)isalsorelativelyhighat1118 mm(World ite and rhyolite, whilst elsewhere the mountains are formed MeteorologicalOrganisation,1998).Incontrast,atMidelt,in in uplifted and deformed Mesozoic carbonate rocks the lee of the Middle Atlas at the foot of the northern-eastern (Dresch, 1941; Pique, 2001; Pouclet et al., 2007). The high- High Atlas, the 1957–1989 annual precipitation average is est peaks are situated at the south-western end of the range just 208 mm (World Meteorological Organisation, 1998), in the High Atlas and culminate in the Jbel Toubkal massif although totals vary considerably year on year from <100 (4167 m a.s.l.). North of the Atlas proper are the Rif and tonearly500 mm (Rhanem,2009).Precipitation values from Tell mountains which border the Mediterranean Sea and the highest parts of the High Atlas are rare, although Messerli extend from northern Morocco to Tunisia. They are a folded (1967) noted mean annual precipitation totals of ca. 800 mm range consisting of carbonates, flysch and crystalline base- on the north-western flanks of the Toubkal massif. The east- ment rocks (Pique, 2001). ern flanks of the Atlas range, draining into the Sahara region, Glacial and periglacial activity has occurred in North are particularly arid with annual precipitation as low as and West Africa on numerous occasions. The oldest 200 mminthesouth-eastfoothillsofJbelToubkalintheHigh recorded is that of the Ordovician ice sheet, which existed Atlas (Messerli, 1967; Rhanem, 2009). over what was then western Gondwanaland (Ghienne, 2003). More recent, Quaternary glacial and periglacial fea- tures are in evidence throughout the Atlas Mountains 76.2. THE HIGH ATLAS (Hughes et al., 2004) like in many other mountains sur- rounding the Mediterranean basin (Hughes et al., 2006) The highest mountains in North Africa exist in this region, and also other high mountains across Africa (Osmaston including the Jbel Toubkal (4165 m a.s.l.), Irhil M’Goun and Harrison, 2005; Mark and Osmaston, 2008). However, (4071 m a.s.l.) and Jbel Ayachi (3751 m a.s.l.). Glacial Developments in Quaternary Science. Vol. 15, doi: 10.1016/B978-0-444-53447-7.00076-3 ISSN: 1571-0866, # 2011 Elsevier B.V. All rights reserved. 1065 Author's personal copy 1066 Quaternary Glaciations - Extent and Chronology FIGURE 76.1 Location map of the Atlas Mountains indicating mountain areas mentioned in the text. features such as cirques, troughs, roche moutone´e, riegels rock glaciers, whereas these features better resemble land- and moraines have been noted in all these massifs (Dresch, slides as a result of rock-slope failure. Nevertheless, these 1941, 1949; Heybrock, 1953; Mensching, 1953; Wiche, coarse boulder deposits, like at Arroumd (also spelt Aremd 1953; Awad, 1963; Beaudet, 1971). or Aremdt), are closely associated with glaciation since rock- The largest glaciers formed in the Toubkal massif, slope failures and resultant landslides are common in the where valley glaciers emanated from a central ice field Mediterranean mountains and frequently occur in over- which formed between the two highest summits, Toubkal deepened glacial valleys (Figs. 76.5 and 76.6). Furthermore, (4167 m a.s.l.) and Ouanuokrim (4067 m a.s.l.). The north- it is possible that rock-slope failures produced a catastrophic ern outlet glacier draining this ice field extended nearly landslide onto the surface of a retreating glacier in this valley. 10 km to an altitude of just 2000 m a.s.l., ca. 1 km downval- This is supported by the presence of lateral moraines bound- ley of the shrine of Sidi Chamarouch. Valley glaciers also ing rock-slope-failure debris on both sides of the valley formed on the northern slopes of Aksoual and Bou Igue- (Fig. 76.6). Cosmogenic nuclide exposure ages from boul- nouane. Well-defined cirques are present in the upper ders on both the surfaces of the landslide debris and the catchments around Toubkal and on the northern slopes of lateral moraines will help test this scenario further. Aksoual and Bou Iguenouane and these cirques contain A similar mechanism of paraglacial glacier–landslide inter- moraines (Figs. 76.2 and 76.3). In fact, at least three sepa- action has been suggested for the formation of the barrage at rate moraine units are present in these mountains, widely Lac D’Ifni on the southern slopes of Toubkal (Celerier and separated in altitude with some moraines present at eleva- Charton, 1923). tions as low as 2000 m a.s.l. (Fig. 76.4). Until recently, the age of the High Atlas moraines was a Dresch (1941) estimated that the Pleistocene snowline matter of speculation. However, a programme of cosmo- was situated at 3600–3800 m a.s.l., whilst later workers have genic isotope analyses is now underway at the UK Natural derived slightly lower estimates at 3400–3500 m a.s.l. Environment Research Council Cosmogenic Isotope Anal- (Mensching, 1953) and at 3300–3400 m a.s.l. (Awad, ysis Facility, at East Kilbride in Scotland. This dating pro- 1963). However, most researchers have underestimated gramme is focusing on dating glacial landforms in the the extent of glaciation in the Toubkal area and overesti- Toubkal massif and is applying 10Be analyses to quartz mated the altitude of Pleistocene snowlines. Dresch (1941) veins and 36Cl analyses to andesite boulders to provide esti- and Mensching (1953) both recognised clear moraines in mates of exposure history for the moraines in this area.