JOURNAL OF QUATERNARY SCIENCE (2006) 21(6) 629–643 Copyright ß 2006 John Wiley & Sons, Ltd. Published online 15 June 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jqs.1002 The geomorphology and sedimentology of the ‘Te ´mpanos’ moraine at Laguna San Rafael, Chile NEIL F. GLASSER, 1 * KRISTER JANSSON, 2 WISHART A. MITCHELL 3 and STEPHAN HARRISON 4 1 Centre for Glaciology, Institute of Geography and Earth Sciences, University of Wales, Aberystwyth, Ceredigion, UK 2 Department of Physical Geography and Quaternary Geology, Stockholm University, Stockholm, Sweden 3 Department of Geography, University of Durham, Durham, UK 4 School of Geography and the Environment, University of Oxford, UK Glasser, N. F., Jansson, K., Mitchell, W. A., and Harrison, S. 2006. The geomorphology and sedimentology of the ‘Te ´mpanos’ moraine at Laguna San Rafael, Chile. J. Quaternary Sci., Vol. 21. pp. 629–643. ISSN 0267–8179. Received 21 July 2005; Revised 5 November 2005; Accepted 18 December 2005 ABSTRACT: The San Rafael Glacier is one of the largest and most dynamic outlet glaciers of the North Patagonian Iceﬁeld, Chile. The contemporary glacier calves into a large tidal laguna, which is partially impounded by a large arcuate moraine. This moraine, termed the ‘Te ´mpanos’ moraine, marks the former extent of an expanded San Rafael Glacier and is of an unknown age. Here we describe the geomorphology and sedimentology of the ‘Te ´ mpanos’ moraine and relate these to styles of glacier advance and recession. The ‘Te ´mpanos’ moraine attains a maximum height in excess of 40 m and is either single-crested with a gentle ice-proximal face and steep distal face, or consists of multiple crests superimposed on a gentle slope. The internal composition of the moraine is vari- able, comprising diamicton, sorted sedimentary facies (silts, sands and gravel) and laminites. We interpret these sediments as evidence that the San Rafael Glacier advanced over a former proglacial area, culminating in the formation of the ‘Te ´mpanos’ moraine. This advance deformed a carpet of lacustrine or marine mud, which was eroded from its original location, transported and smeared over the glacier bed as a subglacial deposit. We use these sedimentary descriptions as the basis for a recon- struction of the Holocene ﬂuctuations of the glacier. Copyright ß 2006 John Wiley & Sons, Ltd. KEYWORDS: glacier ﬂuctuations; glacial geomorphology; sedimentology; Patagonia. Introduction The ‘Te ´mpanos’ moraine at Laguna San Rafael is a large mor- aine complex developed in front of the San Rafael Glacier, one of the largest and most dynamic outlet glaciers of the North Patagonian Iceﬁeld in southern Chile. The San Rafael Glacier is of considerable global signiﬁcance because measured sur- face velocities indicate that it is amongst the fastest-ﬂowing gla- ciers on Earth (Warren et al., 1995). Terminating in the tidal Laguna San Rafael, with water depths typically between 50 and 100 m and locally deeper (Nakajima et al., 1987), it is the only tidewater outlet glacier of the North Patagonian Iceﬁeld, and the closest tidewater glacier to the Equator on Earth. The glacier also has the longest documented ﬂuctuation history of any glacier in southern South America (Simpson, 1875; Bru ¨ ggen, 1950; Lawrence and Lawrence, 1959; Heusser, 1960; Muller, 1960; Warren, 1993; Porter, 2000). In addition, the ‘Te ´mpanos’ moraine is important because of its place within South American Quaternary strati- graphy (Bru ¨ ggen, 1950; Lawrence and Lawrence, 1959; Heusser, 1960; Muller, 1960). The aim of this paper is to pro- vide a description of the moraine morphology and its internal composition and to present an interpretation of the glaciologi- cal context in which the ‘Te ´mpanos’ moraine was formed. The North Patagonian Iceﬁeld (47  00 0 S, 73  39 0 W) is 120 km long and 40–60 km wide, capping the Andean Cordil- lera between altitudes of 700 and 2500 m above sea level. There are ca. 70 outlet glaciers draining the North Patagonian Iceﬁeld, with a total ice area (excluding rock outcrops) of 3953 km 2 (Rivera et al., in press). The iceﬁeld is nourished by mid-latitude weather systems and is characterised by abundant precipitation, high ablation rates, steep mass-balance gradients and high ice velocities, which, together with sharp local topographic and climatological contrasts, creates a dynamic and temperate glacier system (Warren and Sugden, 1993). Most glaciers of the North Patagonian Iceﬁeld are currently receding from their historical maximum positions attained during the ‘Little Ice Age’ between AD 1200 and * Correspondence to: N. F. Glasser, Centre for Glaciology, Institute of Geography and Earth Sciences, University of Wales, Aberystwyth, Ceredigion SY23 3DB, UK. E-mail: nfg@aber.ac.uk