Do swarms of migrating barchan dunes record paleoenvironmental changes? — A case study spanning the middle to late Holocene in the Pampa de Jaguay, southern Peru Ralf Hesse ⁎ Department of Geography, Friedrich Schiller University Jena, Löbdergraben 32, 07740 Jena, Germany abstract article info Article history: Received 12 February 2008 Received in revised form 19 August 2008 Accepted 21 August 2008 Available online 28 August 2008 Keywords: Aeolian dynamics Barchans Peru Holocene Swarms of barchan dunes are common in arid environments. Unlike immobile or slowly moving dunes whose stratigraphy can be used to reconstruct paleoenvironmental changes, the high migration rate of barchans seems to prohibit their use as geoarchives. In this paper, a possible use of barchan swarms for paleoenvironmental reconstructions is presented. The approach is based on dune migration. In a case study based on 500 dunes in the Pampa de Jaguay aeolian transport corridor in coastal southern Peru, middle to late Holocene changes in the supply of aeolian material are inferred from calculating the time of dune initiation at the coastline. Limitations posed by the assumptions underlying this approach are discussed. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Immobile or slowly moving sand dunes have frequently been used as archives of paleoenvironmental changes. Dune stratigraphy has been combined with archaeological (McFadgen, 1994) and faunal evidence (Brook, 1999) as well as ESR (Khadkikar et al., 1999), TSL (e.g. Chawla et al., 1992) and OSL dating (e.g. Li and Sun, 2006) to gain information about phases of sand accumulation or geomorphic stability. Dune field pattern parameters have been correlated with dune field ages (Ewing et al., 2006). Barchan dunes, however, do generally not appear suitable for such paleoenvironmental recon- structions due to their high migration rate which commonly leads to a complete overturning of their sediment within a few years. However, they do represent the best-studied type of dunes, and both their morphological and dynamic parameters are well understood (e.g. Bagnold, 1941; Hesp and Hastings, 1998) and have been successfully modelled on the individual dune scale (e.g. Herrmann and Sauer- mann, 2000; Hersen, 2004) as well as on the dune field scale (Lima et al., 2002). Besides their wide distribution in arid environments on Earth (e.g. India: Singhvi and Kar, 2004; Israel: Tsoar and Blumberg, 2002; Saudi Arabia: Abolkhair, 2004; Chad: Warren et al., 2007; North America: Forman et al., 2001) they have also been observed in submarine environments (Todd, 2005) and on Mars (Bourke et al., 2006). In the coastal desert of southern Peru, barchans have been investigated by Finkel (1959), Hastenrath (1967), Lettau and Lettau (1969) and Gay (1962, 1999). Empirical relationships between barchan width and height have been found by several authors and summarised by Hesp and Hastings (1998). Furthermore, an empirical relationship between barchan width and migration rate has been established for the Pampa de Jaguay barchan swarm and a further group of barchans (Gay, 1962, 1999). The aim of this paper is to investigate whether swarms of migrating barchan dunes as a whole record paleoenvironmental changes beyond the single dune scale and whether they can thus be used as geo- archives. To this end, the entire Pampa de Jaguay barchan swarm, of which a section was studied by Gay (1962, 1999), is analysed. A local width–height relationship is established and the findings of Gay (1962, 1999) are applied to reconstruct the middle to late Holocene changes in the volume of aeolian material supplied to the Pampa de Jaguay barchan swarm. A comparable approach has previously been used for a single dune by Haynes (1989) but not for an entire dune swarm. 2. Research area The area under investigation is the Pampa de Jaguay (Fig. 1 , ca. 15°08′–15°37′S, 74°42′–74°58′W) in the coastal desert of southern Peru. This desert is characterised by hyperarid conditions with average annual precipitation b 10 mm yr - 1 (ONERN, 1971) and is completely devoid of vegetation with the exception of allogenic river oases and lomas (fog vegetation) in situations with steeply rising coastal topography (Rundel et al., 1991). The Pampa de Jaguay is bordered by the Cordillera de la Costa to the west and the foot of the Cordillera Occidental to the east. It rises from sea level to ca. 560 m asl some 35 km inland from the coast or 50 km from the coast in the prevailing wind direction. Geomorphology 104 (2009) 185–190 ⁎ Tel.: +49 3641 948813; fax: +49 3641 948812. E-mail address: Ralf.Hesse@uni-jena.de. 0169-555X/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.geomorph.2008.08.006 Contents lists available at ScienceDirect Geomorphology journal homepage: www.elsevier.com/locate/geomorph