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This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Author's personal copy Quaternary Science Reviews 28 (2009) 2165–2212 Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev Glaciation in the Andes during the Lateglacial and Holocene Donald T. Rodbell a,*, Jacqueline A. Smith b, Bryan G. Mark c a Geology Department, Union College, Schenectady, NY 12308, USA b Department of Physical and Biological Sciences, The College of Saint Rose, Albany, NY 12203, USA c Department of Geography, The Ohio State University, Columbus, OH 43210, USA article info abstract Article history: This review updates the chronology of Andean glaciation during the Lateglacial and the Holocene from Received 23 March 2008 the numerous articles and reviews published over the past three decades. The Andes, which include Received in revised form some of the world’s wettest and driest mountainous regions, offer an unparalleled opportunity to 29 March 2009 elucidate spatial and temporal patterns of glaciation along a continuous 68-degree meridional transect. Accepted 30 March 2009 The geographic and altitudinal extent of modern glaciers and the sensitivity of both modern and former glaciers to respond to changes in specific climatic variables reflect broad-scale atmospheric circulation and consequent regional moisture patterns. Glaciers in the tropical Andes and in the mid-latitude Andes are likely to have been far more sensitive to changes in temperature than glaciers in the dry subtropical Andes. Broad-scale temporal and spatial patterns of glaciation during the Lateglacial are apparent. In the southernmost Andes, the Lateglacial chronology appears to have a strong Antarctic signature with the best-dated moraines correlating closely with the Antarctic Cold Reversal. The southernmost Andes do not appear to have experienced a significant ice advance coeval with the Younger Dryas (YD) climatic reversal. At the other end of the Andes, from w0to9N, a stronger YD connection may exist, but critical stratigraphic and geochronologic work is required before a YD ice advance can be fully demonstrated. In the central Andes of Peru, well-dated moraines record a significant ice readvance at the onset of the YD, but ice was retreating during much of the remaining YD interval. The spatial–temporal pattern of Holocene glaciation exhibits tantalizing but incomplete evidence for an Early to Mid-Holocene ice advance(s) in many regions, but not in the arid subtropical Andes, where moraines deposited during or slightly prior to the Little Ice Age (LIA) record the most extensive advance of the Holocene. In many regions, there is strong evidence for Neoglacial advances in the interval between 1.0 and 2.5 ka. Moraines that correlate with the LIA of the Northern Hemisphere are seen in all presently glacierized mountain ranges; most of these date to within the past 450 years. Outboard of these moraines in many regions are moraines of a slightly more extensive advance that occurred several hundred years prior to the onset of the LIA. Priorities for future work include filling in several prominent spatial gaps in the distribution of chronologic studies. For the Lateglacial these gaps include the arid regions of northern Chile and Argentina, the southern Peruvian Andes between 11.5and 13.5S, and the Andes of northern Peru and southern Ecuador between 3 and 9S. Areas in need of better representation in regional datasets of Holocene glaciation include all of the Andes north of the Equator. Specific chronologic priorities include the need for close bracketing radiocarbon ages for purported Early and Mid-Holocene moraines, and the increased application of cosmogenic radionuclide dating to Lateglacial and Early Holocene moraines that are already constrained by maximum-limiting radiocarbon ages. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction these publications (Clapperton, 1983, 1993a; Mercer, 1983, 1984) reviewed evidence for, and the timing of, glaciation throughout This review builds on a series of summary articles, which span South America over the entire Cenozoic. Others reviewed evidence more than 30 years, on the glacial history of the Andes. Several of for specific time intervals and in specific geographic sectors. For example, whereas Mercer (1976, 1982) provided a comprehensive review of Holocene glaciation in southern South America, Clap- * Corresponding author. Tel.: þ1 518 388 6034; fax: þ1 518 388 6417. E-mail addresses: [email protected] (D.T. Rodbell), [email protected] perton and Sugden (1988) reviewed evidence of Holocene glacia- (J.A. Smith), [email protected] (B.G. Mark). tion throughout the Andes, Seltzer (1990) reviewed the record of 0277-3791/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2009.03.012 Author's personal copy 2166 D.T. Rodbell et al. / Quaternary Science Reviews 28 (2009) 2165–2212 Lateglacial and Holocene glaciation in Peru, Clapperton and Seltzer elevational control on precipitation in this region likely yields steep (2001) reviewed evidence for glaciation during marine isotope vertical accumulation gradients, and thus glaciers here may have stage 2 (MIS 2) throughout the Americas, and Mark et al. (2004) and the steepest mass balance gradients of all Andean glaciers. High Smith et al. (2008) summarized the Late Quaternary records from precipitation in the accumulation areas of glaciers in this region Ecuador, Peru, and Bolivia. Finally, Schubert and Clapperton (1990) coupled with the relatively low elevation of the 0C isotherm reviewed the Late Quaternary record of glaciation in Ecuador, results in numerous tidewater and freshwater calving glaciers, Colombia, and Venezuela. All radiocarbon ages referred to herein as including the lowest latitude tidewater glacier on Earth, the San ‘‘ka’’ refer to thousands of calibrated 14C years BP, with BP equal to Rafael Glacier, that drains the west side of the North Patagonian Ice AD 1950, and are thus equivalent to radionuclide and luminescence Field (NPIF) at w46.7S(Warren, 1993). ‘‘ka’’ ages. Calendar ages over the past two millennia are reported in years AD. 2.2. Glaciers in the dry subtropical Andes The Lateglacial (defined for the purposes of this paper as the interval between w16.7 and 11.5 ka (w14,000 and 10,000 14C yr BP) The Andean subtropics as generally defined extend from has attracted the attention of numerous workers and has been the w23.5Sto30S, but climatologically and glaciologically it is focus of several review articles. (Clapperton, 1993a,b) reviewed useful to consider the Andean subtropics as extending from w18S evidence for glacier oscillations during this time interval from the in the western Bolivian Andes to 29S in northern Chile. In the entire length of the Andes, and Heine (1993) focused his review on northern part of this latitudinal belt the western and eastern the tropical Andes. cordillera of the Andes are as much as w200 km apart, and The objectives of this review, in light of the abundance of between these two cordilleras lies the dry Bolivian Altiplano. summary articles noted above, is to provide an update on the Precipitation in this region is primarily derived from the tropical chronology of glaciation in South America over the Lateglacial and easterlies and occurs during the austral summer (Fig. 3B) in the Holocene, and to critically evaluate the database in terms of the association with the development of the South American summer degree of regional and interregional synchrony of events. We focus monsoon (Zhau and Lau, 1998), although south of 27S some on the past w17 ka because there have been numerous papers in moisture is occasionally derived from the westerlies (Ammann the last two decades that report on the timing of glaciation in the et al., 2001). In either case, little precipitation falls; mean annual Andes during this interval. In addition, several events such as the precipitation (MAP) is 440 mm on the summit of Nevado Sajama Antarctic Cold Reversal (ACR; e.g., Steig et al., 1998), Younger Dryas (6542 m a.s.l.) at 18.1S(Thompson et al., 1998) and w300 mm at (YD; e.g., Mangerud et al., 1974), and the Little Ice Age (LIA; e.g., w29S(Grosjean et al., 1998). Owing to the aridity of this region, Grove, 1988) occurred during this interval, and, though these modern glaciers do not exist between 18.5 and 27S despite events have been long recognized in high latitude regions, there is numerous summit elevations above 6000 m, with some as high as still considerable uncertainty and debate over their signature in 6700 m (Ammann et al., 2001), and an elevation of the 0 isotherm different parts of the Andes. that declines southward from w5000 to 4100 m a.s.l. (Klein et al., 1999; Grosjean et al., 1998). The few glaciers that do exist at the 2. Geographic and glaciologic setting northern end of the dry subtropical Andes are wholly above the 0C isotherm, and with ablation limited to sublimation, likely have The Andes span 68 of latitude (Fig. 1) from the northernmost very low vertical ablation gradients (Kaser, 2001). tropical Andes of Colombia (12N) to the temperate Andes of southernmost Chile and Argentina (56S), and include some of the 2.3. Tropical Andean glaciers driest and wettest mountainous regions on Earth (Fig.