ARTICLE IN PRESS

Quaternary International 138–139 (2005) 145–167

Regional synthesis of last glacial maximum snowlines in the tropical Andes, South America

Jacqueline A. Smitha,Ã, Geoffrey O. Seltzera,y, Donald T. Rodbellb, Andrew G. Kleinc

aDepartment of Earth Sciences, 204 Heroy Geology Lab, Syracuse University, Syracuse, NY 13244-1070, USA bDepartment of Geology, Union College, Schenectady, NY 12308, USA cDepartment of Geography, Texas A&M University, College Station, TX 77843, USA

Available online 18 April 2005

Abstract

The modern glaciers of the tropical Andes are a small remnant of the ice that occupied the mountain chain during past glacial periods. Estimates of local Last Glacial Maximum (LGM) snowline depression range from low (e.g., 200–300 m in the Junin region, Peru), through intermediate (600 m at Laguna Kollpa Kkota in Bolivia), to high (e.g., 1100–1350 m in the Cordillera Oriental, Peru). Although a considerable body of work on paleosnowlines exists for the tropical Andes, absolute dating is lacking for most sites. Moraines that have been reliably dated to 21 cal kyr BP have been identified at few locations in the tropical Andes. More commonly, but still rarely, moraines can be bracketed between about 10 14C kyr (11.5 cal kyr BP) and 30 14C kyr BP. Typically, only minimum-limiting ages for glacial retreat are available. Cosmogenic dating of erratics on moraines may be able to provide absolute dating with sufficient accuracy to identify deposits of the local LGM. Ongoing work using cosmogenic 10Be and 26Al in Peru and Bolivia suggests that the local LGM may have occurred prior to 21 cal kyr BP. r 2005 Elsevier Ltd and INQUA. All rights reserved.

1. Introduction ages that are calibrated to calendar years before present (Stuiver and Reimer, 1993). The primary purpose of this synthesis of snowline This synthesis differs fromprevious studies of information for tropical South America is to serve as a regional snowline change (e.g., Hastenrath, 1967, 1971, resource for climate modelers seeking reliable informa- 1985; Nogami, 1976; Fox and Bloom, 1994; Klein et al., tion about equilibrium-line altitudes (ELAs) or snow- 1999, 2001; Dornbusch, 2001) in that it is a critical and lines to use for comparison with output from climate conservative examination of evidence for LGM mor- simulation of the Last Glacial Maximum (LGM). As aines. It includes an evaluation of the methods used by used here, the term ‘‘last glacial maximum’’ refers to workers to establish the age of glaciation, the proximity the maximum extent of glaciation in the Northern of the ages associated with glacial features to the LGM Hemisphere at about 18,000 14C yr BP (about 21,000 target age of 21,000 cal yr BP, and an assessment of the cal yr BP) as interpreted fromthe marine oxygen isotope methods used to determine the change in snowline or record (Imbrie et al., 1984). Throughout this manu- ELA. One criterion in the evaluation of chronological script 14C yr BP refers to radiocarbon years before data is the requirement that the feature have radiometric present (AD 1950) and cal yr BP refers to radiocarbon dating associated with it to be considered useful for comparison with climate modeling output. We have focused on the tropical Andes that border the Pacific Ocean south of the equator as a coherent ÃCorresponding author. Tel.: +1 315 443 2672; fax: +1 315 443 3363. geomorphic unit; the Andes of the circum-Caribbean E-mail address: [email protected] (J.A. Smith). region are treated separately (see Lachniet and yDeceased. Vazquez-Selem, this volume). The tropical Andes are

1040-6182/$ - see front matter r 2005 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2005.02.011 ARTICLE IN PRESS 146 J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 characterized by prevailing easterlies that bring moisture to group the major study regions by the nations in which across the Amazon Basin from the Atlantic Ocean they are located: Ecuador, Peru, and Bolivia (Fig. 1). (Johnson, 1976). As a result, there is a general east–west Table 1 is a compilation of snowline data presented in gradient in snowlines, with the lowest snowlines on east- this synthesis. Estimates of snowline depression at the facing slopes of the Eastern Cordillera. Increasing LGM are summarized in Fig. 2. The discussion begins in aridity to the south produces a general north–south the north and proceeds southward through the region. gradient in snowlines as well, with the highest snowlines Our goal has been to include sites where the glaciation (6000 m) on the arid Altiplano, although the 01 chronology is based on radiometric dating and the isothermlies approximately 1000 mlower. In such areas method used to calculate changes in snowline at the of extreme aridity, the location of the ELA is highly LGM has been specified. These criteria set this study dependent on the availability of moisture, rather than apart fromprevious regional syntheses that made temperature (Johnson, 1976). In their respective surveys simplifying assumptions about LGM chronology and of geomorphic evidence for Pleistocene glaciations, incorporated snowline changes estimated by differing Hastenrath (1967, 1971, 1985), Nogami (1976), and methods. Klein et al. (1999) concluded that a pattern of rising snowlines fromeast to west and fromnorth to south also existed during the Pleistocene in the tropical Andes. 3. Ecuador In a study limited to Peru, Fox and Bloom(1994) concluded that Pleistocene snowlines rose fromeast to The Ecuadorian Andes consist of two north–south- west in the Peruvian Andes. trending, near-parallel chains, the Eastern Cordillera The tropical Andes are currently dominated by valley (Cordillera Oriental) and the Western Cordillera glaciers located above altitudes of 5 km; only a few ice (Cordillera Occidental), which are separated by high- caps remain (e.g., Quelccaya Ice Cap in Peru). During altitude basins. The highest peaks in the Ecuadorean the LGM in the region, glacial ice expanded and Andes are volcanic and include ice-covered Volca´ n descended up to 1000 mor morefromcurrent terminal Chimborazo (6310 m), the highest point in Ecuador, and positions (e.g., Klein et al., 1999), ice caps were more Cotopaxi (5900 m), the world’s highest active volcano common, and many areas now devoid of ice were then (Johnson, 1976). South of about 21S the altitude of the occupied by both valley glaciers and piedmont glaciers highest peaks in the Ecuadorian Andes falls below (e.g., Clapperton, 1993). The mass-balance regime of 5000 mand modernglacial ice is absent. Peak altitudes glaciers in tropical climates with distinct wet and dry continue to decrease toward the southern end of seasons differs fromthose in high latitudes. On tropical Ecuador and the northern end of Peru, where peak glaciers, ablation typically occurs year round, altitudes are typically in the range of 3000–3500 m whereas accumulation occurs during the wet season, (Instituto Geogra´ fico Militar, 1991). which is generally the austral summer in tropical South No LGM moraines have been definitively identified America (Benn et al., this volume; Kaser and Osmaston, and dated in the Ecuadorian Andes. Near Papallacta 2002; Johnson, 1976). This mass-balance regime com- Pass on the Potrerillos Plateau, moraines have been plicates the determination of snowlines on tropical loosely constrained to a period that includes the LGM. glaciers. Clapperton et al. (1997) have bracketed the Sucus Porter (2001) outlined five techniques commonly used advance between 13 14C kyr BP (15.5 cal kyr BP) and to estimate snowlines: cirque-floor altitude, upvalley 30 14C kyr BP, but background information on the limits of lateral moraines, glaciation threshold, altitude older age is incomplete. ratios (including terminus-to-headwall-altitude-ratio, or THAR), and accumulation-area ratio (AAR). In his 3.1. Volca´n Pichincha, Western Cordillera, 01 12.50 S, comparison of the five methods, Porter referred to the 781 350 W(Fig. 1, Site 1) conclusions of Meierding (1982) that THAR and AAR methods produced the most consistent results. Benn Heine (1995a) identified seven Quaternary moraine et al. (this volume) discuss the assumptions and sets in the Ecuadorean Andes: M I–M VII (M I is requirements associated with specific techniques used oldest). He concluded that the M IV moraines were to estimate snowlines. deposited at the LGM. On Volca´ n Pichincha (4784 m; Fig. 1, Site 1) in the Western Cordillera, the M IV moraines commonly consist of narrow lateral and 2. Major study regions terminal moraines enclosing irregular, hummocky tills, which Heine inferred to be remnants of ice-cored In tropical circum-Pacific South America, national moraines. Heine reported that the M IV moraines boundaries broadly coincide with changes in the descend to altitudes of 3900–4000 mand that deposition structure and climate of the Andes. It is therefore useful of these moraines ‘‘gave evidence of a depression of the ARTICLE IN PRESS J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 147

Fig. 1. Location of sites in the tropical Andes of South America that are discussed in the text. Thin gray lines are 3000-m contour lines; thick black lines mark political boundaries. lower limit of ice-cored moraines of about 800–1000 m the Potrerillos Plateau, with peak altitudes of less than compared with the recent occurrence of similar forms on 4400 m, is currently free of glacial ice. Clapperton et al. Mt. Chimborazo.’’ He did not provide explicit ELA (1997) estimated the modern ELA at Volca´ n Antisana at estimates for the M IV moraines. 4970750 mon the northern and western sides, where Chronological control for the M IV moraines at modern glaciers terminate at 4600 m. They did not Volca´ n Pichincha is minimal (Fig. 2). No radiocarbon describe the specific method used to estimate the modern dates are directly associated with the M IV moraines ELA. themselves. The M V moraines immediately upvalley The Plateau, which lies mostly at altitudes of fromthe M IV morainesat 4100–4200 menclose a basin 3900–4200 m, has been glaciated more than once during containing varved clays and peat fromwhich a the Quaternary (Clapperton et al., 1997). Weathered minimum age for deglaciation of 13,010 14CyrBP terminal moraines at altitudes of 3000 mon the (15.6 cal kyr BP) was obtained on peat. Organic-rich leeward west side and 2700 mon the windward east sediments on the inner edge of the M II moraines side mark the most extensive Quaternary ice cover. (located downvalley fromthe M IV moraines) were Younger moraines upvalley generally terminate above dated at 449,500 14C yr BP. 3600 mon the west side and 3000 mon the east side of the Plateau. Clapperton et al. (1997) noted that the 3.2. Papallacta Valley, Potrerillos Plateau, Eastern radiocarbon age of organic material beneath two tills Cordillera, ca. 01 200 S, 781 120 W separated by a lava flow at 3500 mindicated that glacial ice had advanced past that point at least twice after The Potrerillos Plateau (Fig. 1, Site 2) is located in the 30 14C kyr BP. Eastern Cordillera of Ecuador, extending northward Clapperton et al. (1997), working near Papallacta approximately 40 km from Volca´ n Antisana (5758 m). Pass on the southern side of the Plateau, focused on Whereas Volca´ n Antisana still supports a small ice cap, moraines in several valleys that showed morphostrati- ARTICLE IN PRESS 148 J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 5 5 : : : : : : : : 0 0 0 0 0 0 0 0 ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ Glacier type LGM ELA (m) LGM ELA method 4600 Outlet NA No ELA reported  Terminus altitude (m) Headwall altitude (m) altitude (m) 77.30 WSW 5360 4825 3850 Valley 4143 THAR 77.30 WSW 5630 4950 4250 Valley 4460 THAR 77.25 W 5682 5050 4025 Valley 4333 THAR 77.47 E 4300 3760 3000 Valley 3170 THAR 77.55 W 4350 3911 3452 Valley 3591 THAR 77.50 W 4525 4077 3746 Valley 3827 THAR 78.75 S 5202 5202 3800–4000 Ice cap NA No ELA reported 78.85 W 6313 5800 3800–4000 Ice cap 4090 THAR 78.70 E 6313 5800 3800–4000 Ice cap 3880 THAR 78.82 N 5202 5202 3800–4000 Ice cap NA No ELA reported 78.82 N 5202 5202 3800–4000 Ice cap NA No ELA reported 78.82 N 5202 5202 3800–4000 Ice cap NA No ELA reported 78.82 N 5202 5202 3800–4000 Ice cap NA No ELA reported 78.78 NW 5202 5202 3800–4000 Ice cap NA No ELA reported 78.78 N 5202 5202 3600–3800 Ice cap NA No ELA reported 78.15 N&W 5758 5758 78.17 SE 4313 4313 3950 Valley 4050 not clear—logic? 78.17 SW 4170 4170 3850 Valley NA No ELA reported 78.58 S, SE 4784 4784 3900–4000 Valley NA No ELA reported À À À À À À À À À À À À À À À À À À À 9.75 9.80 9.90 7.65 7.60 7.80 1.45 1.45 1.45 1.36 1.36 1.36 1.36 1.34 1.33 0.50 0.33 0.33 0.21 À À À À À À À À À À À À À À À À À À À Peru Peru Peru Peru Peru Peru Ecuador Ecuador Ecuador Ecuador Ecuador Ecuador Ecuador Ecuador Ecuador Ecuador Ecuador Ecuador Ecuador % n Antisana, n Pichincha, a, W Cord. ´ ´ o Pumapampa, ´ Quebrada Cotush, Cordillera Blanca Quebrada Gueshque, Cordillera Blanca Cordillera Blanca Cordillera Oriental-E of main divide Cord. Oriental-W of main divide; E of local of local divide Chimborazo- Carihuairazo Massif, glac. lake, W Cord. Chimborazo- Carihuairazo Massif, Chimb. W, W Cord. Chimborazo- Carihuairazo Massif, Chimb. E, W Cord. Chimborazo- Carihuairazo Massif, Site 4b, W Cord. Chimborazo- Carihuairazo Massif, Site 4 Chimborazo- Carihuairazo Massif, Site 3b, W Cord. Chimborazo- Carihuairazo Massif, Site 3a, W Cord. Chimborazo- Carihuairazo Massif, Site 2, W Cord. Carihuairazo Massif, Site 1, W Cord. Volca Eastern Cord. Potrerillos site, Papallacta V., Potrerillos Plat., E Cord. V., Potrerillos Plat., E Cord. Western Cordillera 5Rı 4 Cordillera Oriental-W 3 Chimborazo- 2 Sucus site, Papallacta Table 1 Summary of published snowline information for eachSite site discussed in the LGM snowline text locality Country Latitude Longitude Aspect Summit 1 Volca ARTICLE IN PRESS J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 149 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) 2 & 0.4 (ave.) : : : : : : : : : : : : : : : : : : : 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ 178 THAR 7 Heine, 1995a Clapperton et al., 1997 Clapperton et al., 1997 Clapperton et al., 1997 C22 2 7 14 C827 C727 10,035 14 14 4 13,200 13,010 10,855, 4 o LGM date # Dates DMC DC References 4 77.30 WSW 5237 4900 3850 Valley 4165 THAR 77.3077.36 WSW77.42 SW77.38 SW77.42 SW 572077.38 SW 5700 507077.43 SW 572077.43 5075 3900 6370 SW77.47 5400 6370 SW 385077.13 5425 Valley 6222 SW 395077.40 5425 N Valley 3950 550077.21 5250 NNE Valley 3950 618077.23 4251 NE 5050 Valley 3950 616077.26 E 5525 4218 Valley 5208 370077.26 NE 5450 5580 4385 Valley 355077.24 THAR 4393 5200 5200 E Valley 3750 510077.24 4145 THAR SSE Valley 5240 4350 4900 4078 THAR 372577.36 5100 ENE Valley THAR 4900 4105 3900 Valley WSW 4900 5425 Valley THAR 4143 5100 3700 THAR 4260 5870 Valley 4050 4900 5000 THAR 4605 Valley 5700 5300 4138 4050 Valley THAR 4000 4200 5075 THAR 3850 Valley 4060 Valley THAR 3850 THAR 4305 Valley THAR Valley 4305 4300 THAR THAR 4285 4218 THAR THAR THAR 1996? 1996? 1996? 0 NA NA À À À À À À À À À À À À À À À À À À À date 9.70 9.65 9.60 9.58 9.54 9.51 9.50 9.50 9.47 9.47 9.78 9.76 9.67 9.65 9.60 9.55 9.53 9.47 9.60 Antisana, 40 kmS Antisana, 40 kmS Antisana, 40 kmS À À À À À À À À À À À À À À À À À À À Modern ELA method Modern ELA 4800 Summit is ice-free (4784 m) 1995  4970 Apparent ELA, N&W 4970 Apparent ELA, N&W 4970 Apparent ELA, N&W Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru ELA (m) 4 n Antisana, n Pichincha, ´ ´ o Negro, Cordillera ´ V., Potrerillos Plat., E. Cord. Potrerillos site, Papallacta V., Potrerillos Plat., E. Cord. Volca Eastern Cord. Quebrada Queroccocha, Cordillera Blanca Rı Blanca Quebrada Rurec, Cordillera Blanca Quebrada Cashan, Cordillera Blanca Quebrada Pariac, Cordillera Blanca Quebrada Shallap, Cordillera Blanca Quebrada Quilcayhuanca, Cordillera Blanca Quebrada Churup, Cordillera Blanca Quebrada Cojup, Cordillera Blanca Quebrada Llaca, Cordillera Blanca Quebrada Tayash, Cordillera Blanca Quebrada Pongos, Cordillera Blanca Quebrada Tambillo, Cordillera Blanca Quebrada Huamish, Cordillera Blanca Quebrada Shancompampa, Cordillera Blanca Quebrada Huantsan, Cordillera Blanca Quebrada Pamparaju, Cordillera Blanca Quebrada Carhuascancha, Cordillera Blanca Quebrada Rurec, Cordillera Blanca Western Cordillera 2 Sucus site, Papallacta Site LGM snowline locality Modern 1 Volca ARTICLE IN PRESS 150 J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 ; ; ; ; ; ; ; Clapperton, 1987a, b Clapperton, 1987a, b Clapperton and McEwan, 1985 Clapperton, 1987a, b Clapperton, 1987a, b Clapperton, 1987a, b Clapperton, 1987a, b Clapperton, 1987a, b Clapperton and McEwan, 1985 Birkeland et al., 1989 Rodbell, 1991, 1992 Seltzer, 1987 Birkeland et al., 1989 Rodbell, 1991, 1992 Seltzer, 1987 Birkeland et al., 1989 Rodbell, 1991, 1992 Seltzer, 1987 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 C1C1 2 2 5 5 14 14 35,440 35,440 C1 2 7 C2 2 7 C1 2 7 C1 2 7 C1 2 7 C3 4 7 C3 4 7 C3 4 7 C1 3 6 C1 3 6 C1 3 6 C1 3 6 C1 3 6 C1 3 6 C1 3 6 C1 3 6 C1 3 6 o o 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 11,380 11,370 14,770 1 2 5 35,440 40,330 38,520 14,770, 14,770, 13,280 12,100 12,100 13,280 13,280 13,280 13,280 13,280 13,280 13,280 13,280 12,100 4 o o 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 o 1987 1987 1987 1987 1987 1987 1987 1962 1987 1987 1962 1962 1962 1962 1962 1962 1962 1962 1987 1987 80% origin-term. 80% origin-term. 80% origin-term. 80% origin-term. 80% origin-term. 80% origin-term. 80% origin-term. 80% origin-term.        glacier (map, photo) gradient across E. Cord. gradient across E. Cord. glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) gradient across E. Cord.  4800 Observation, air photos; ELA 4800–4900 Observation, air photos; ELA 4800–4900 Observation, air photos; ELA 4800–4900 Observation, air photos; ELA 4900 Observation, air4800–4900 photos; ELA Observation, air photos; ELA 4800–4900 Observation, air photos; ELA 4950 Approx. midpoint modern 4636 Modern GT+snowline 4558 Modern GT+snowline 49755000 Approx. midpoint modern 4775 Approx. midpoint modern Approx. midpoint4875 modern 4925 Approx. midpoint modern 5075 Approx. midpoint modern 5175 Approx. midpoint modern 4950 Approx. midpoint modern Approx. midpoint modern 4661 Modern GT+snowline 4800–4900 Observation, air photos; ELA ) continued o Pumapampa, o Negro, Cordillera ´ ´ Chimborazo- Carihuairazo Massif, Chimb. E, W Cord. Chimborazo- Carihuairazo Massif, Site 3a, W Cord. Chimborazo- Carihuairazo Massif, Site 3b, W Cord. Chimborazo- Carihuairazo Massif, Site 4a, W Cord. Chimborazo- Carihuairazo Massif, Chimb. W, W Cord. Chimborazo- Carihuairazo Massif, glac. lake, W Cord. Chimborazo- Carihuairazo Massif, Site 4b, W Cord. Cordillera Blanca Cord. Oriental-W of main divide; E of local Cordillera Oriental-E of main divide Quebrada Gueshque, Cordillera Blanca Quebrada Cotush, Cordillera Blanca Quebrada Queroccocha, Cordillera Blanca Rı Blanca Quebrada Rurec, Cordillera Blanca Quebrada Cashan, Cordillera Blanca Quebrada Pariac, Cordillera Blanca Quebrada Shallap, Cordillera Blanca of local divide Carihuairazo Massif, Site 1, W Cord. 4 Cordillera Oriental-W 5Rı Table 1 ( 3 Chimborazo- ARTICLE IN PRESS J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 151 5, MELM, 5, MELM, 5, MELM, 5, MELM, 45 45 : : : : : : 6 6 6 6 0 0 0 0 0 0 : : : : 0 0 0 0 ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ AAR AAR AAR AAR Glacier type LGM ELA (m) LGM ELA method Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 Rodbell, 1991 3400 Valley NA No ELA reported  Terminus altitude (m) Headwall altitude (m) 5200 Piedmont 4500 Limit of bedrock erosion 5200 Valley 4600 Cirque-floor altitude 5300 Piedmont 4500 Cirque-floor altitude    altitude (m) C1 3 6 C1 3 6 C1 3 6 C1 3 6 C1 3 6 C1 3 6 C1 3 6 C1 3 6 C1 3 6 C1 3 6 C1 3 6 C1 3 6 14 14 14 14 14 14 14 14 14 14 14 14 13,280 13,280 13,280 13,280 13,280 13,280 13,280 13,280 13,280 13,280 13,280 16 cal ka 1 3 6 13,280 4 4 4 4 4 4 4 4 4 4 4 4 4 70.44 E 5505 Valley THAR 70.44 S 5505 Valley THAR 70.44 NE 5505 4300 Valley 4650 THAR 70.44 NE 5505 Valley 4800 THAR 70.88 W 5645 5470 4745 Valley 5070 THAR 71.33 NW 6384 5700? 4000–4200 Valley NA 71.25 NW 6384 5700 4300 Valley 4930 THAR 75.05 E 5557 5557 76.08 W 5000 4200 Ice fields 4300 Cirque-floor altitude 76.50 E 76.60 W 76.67 E À À À À À À À À À À À À 1962 1962 1962 1962 1962 1962 1962 1962 1962 1962 1962 1962 1962 15.33 15.33 15.33 15.33 13.97 13.76 13.76 11.92 10.69 11.20 11.00 10.71 À À À À À À À À À À À À glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) glacier (map, photo) Peru Peru Peru Peru Peru Peru Peru Peru Peru 50005200 Approx. midpoint modern 4975 Approx. midpoint modern 5075 Approx. midpoint modern 5125 Approx. midpoint modern 5100 Approx. midpoint modern 5030 Approx. midpoint modern 5030 Approx. midpoint modern Approx. midpoint5030 modern 5030 Approx. midpoint modern 4850 Approx. midpoint modern Approx. midpoint4925 modern Approx. midpoint modern 4950 Approx. midpoint modern Valley, ´ (modern-E), Cordillera Ampato Nevado Sara Sara (modern-S), Cordillera Ampato Sara Sara I (NE), Cordillera Ampato Sara Sara II (NE), Cordillera Ampato Quelccaya Ice Cap Jalacocha Valley, Cordillera Vilcanota Cordillera Vilcanota Junin-East Peru Cordillera Callejon- East Cordillera Callejon- West Quebrada Churup, Cordillera Blanca Quebrada Cojup, Cordillera Blanca Quebrada Llaca, Cordillera Blanca Quebrada Tayash, Cordillera Blanca Quebrada Pongos, Cordillera Blanca Quebrada Tambillo, Cordillera Blanca Quebrada Huamish, Cordillera Blanca Quebrada Shancompampa, Cordillera Blanca Quebrada Huantsan, Cordillera Blanca Quebrada Pamparaju, Cordillera Blanca Quebrada Carhuascancha, Cordillera Blanca Quebrada Rurec, Cordillera Blanca Quebrada Quilcayhuanca, Cordillera Blanca 11 Nevado Sara Sara 10 Huancane 9 Upismayo Valley, 8 Nevado Huaytapallana Peru 6,7 Cerros Cuchpanga Peru Site LGM snowline locality Country Latitude Longitude Aspect Summit ARTICLE IN PRESS 152 J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 5, MELM, 5, MELM, 5, MELM, 5, MELM, 5, MELM, 5, MELM, 5, MELM, 5, MELM, 5, MELM, 5, MELM, 5, MELM, 5, MELM, 5, MELM, 5, MELM, 5, MELM, 5, MELM, 5, MELM, 5, MELM, : : : : : : : : : : : : : : : : : : 6 6 67 67 67 67 67 67 67 67 67 67 67 67 67 67 67 67 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 : : : : : : : : : : : : : : : : : : 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ ¼ AAR AAR AAR AAR AAR AAR AAR AAR AAR AAR AAR AAR AAR AAR AAR AAR AAR AAR 70.44 SW 5505 4050 Valley 4500 THAR 70.44 SW 5505 Valley 4700 THAR 73.08 NW 5228 4100 Valley 4800 THAR 73.08 SW 5228 4400 Valley 4650 THAR 73.08 SE 5228 4400 Valley 4350 THAR 73.08 SE 5228 4400 Valley 4700 THAR 73.08 SE 5228 4400 Valley 4900 THAR 72.90 N 6093 4600 Valley 5000 THAR 72.90 N 6093 4750 Valley 5250 THAR 72.90 N 6093 4850 Valley 5400 THAR 72.90 SW 6093 4400 Valley 4725 THAR 72.90 SW 6093 Valley 4850 THAR 72.90 SE 6093 4500 Valley 4850 THAR 72.39 SW 6377 4450 Valley 4750 THAR 72.39 SW 5270 3850 Valley 4450 THAR 72.39 S 5270 4375 Valley 4700 THAR 72.39 S 5270 4850 Valley 5000 THAR 72.39 E 5270 Valley 4700 THAR 69.00 W 5617 5617 3700–4000 Valley NA No ELA reported À À À À À À À À À À À À À À À À À À À 15.33 15.33 15.11 15.11 15.11 15.11 15.11 15.40 15.40 15.40 15.40 15.40 15.40 15.59 15.59 15.59 15.59 15.59 15.00 À À À À À À À À À À À À À À À À À À À Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Peru Bolivia ) continued Sara Sara I (SW), Cordillera Ampato Sara Sara II (SW), Cordillera Ampato C. Huanipaco/ Cocauro/Allcc. (NW), Cord. Ampato C. Huanipaco/ Cocauro/Allcc. (SW), Cord. Ampato C. Huanipaco/ Cocauro/Allcc. (SE#1), Cord. Ampato C. Huanipaco/ Cocauro/Allcc. (SE#2), Cord. Ampato C. Huanipaco/ Cocauro/Allcc. (SE#3), Cord. Ampato Nevado Solimana (N#1), Cordillera Ampato Nevado Solimana (N#2), Cordillera Ampato Nevado Solimana (N#3), Cordillera Ampato Nevado Solimana (SW#1), Cordillera Ampato Nevado Solimana (SW#2), Cordillera Ampato Nevado Solimana (SE), Cordillera Ampato Nevado Coropuna (SW), Cordillera Ampato Cerros Jollpa/ Yanahuara (SW), Cordillera Ampato Cerros Jollpa/ Yanahuara (S#1), Cordillera Ampato Cerros Jollpa/ Yanahuara (S#2), Cordillera Ampato Cerros Jollpa/ Yanahuara (E), Cordillera Ampato Cordillera Apolobamba Table 1 ( 12 Nevado Ulla Khaya, ARTICLE IN PRESS J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 153 37 (better 5 (first : : 0 0 ¼ ¼ estimate) estimate) ; ; ; ; Dornbusch, 1998 Dornbusch, 1998 ; ; Wright Jr., 1983, 1984 Wright Jr., 1983, 1984 Wright Jr., 1983, 1984 Wright Jr., 1983, 1984 Seltzer, 1987, 1990 Wright Jr. et al.,Instituto 1989 Geografico Nacional, 1983 Mercer and Palacios, 1977 Mark et al., 2002 Mercer and Palacios, 1977 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Mark et al., 2002 Dornbusch, 1998 4000? Valley NA No ELA reported  6000 5460 4260 Valley 4700 THAR 6000 5460 4260 Valley 4860 THAR 4 4 C4 3 6 C4 3 6 C4 3 6 C4 2 7 C1 2 5 C1 4 7 14 14 14 14 14 14 13,540 13,540 14.3 cal ka 5 2 7 10,960 18.5 cal ka14,010 4 3 4 13,540 42,000 4 4 4 4 o 4 4 LGM date4 # Dates DMC DC References 68.33 SW 68.60 ? 6382 NA 68.33 SW À À À 1962 1962 19551955 No dates1955 No dates1955 0 No1955 dates No1955 dates 0 5 No dates 0 No dates 5 0 8 0 5 8 0 5 5 8 5 8 8 8 1987 1962 date 1962 5 (inventory data) 1962 5 (inventory data) 1962 5 (inventory data) 1962 : : : 0 0 0 ¼ ¼ ¼ 16.17 15.85 16.17 À À À photos photos Ames et al. (1988) Ames et al. (1988) Ames et al. (1988) Ames et al. (1988) Ames et al. (1988) Ames et al. (1988) front, 1987) photos Modern ELA method Modernphotos ELA Bolivia Bolivia Bolivia 49004900 Map of 1967 based on air Map of 1967 based on air 5300 AAR 5350 Average, glacier5112 inventory of Average, glacier5350 inventory of 5350 Average, glacier inventory of 5112 Average, glacier inventory of 5112 Average, glacier inventory of NA Average, glacier inventory of NANANA 1955 1955 No dates 1955 No dates 1955 0 No dates 0 No dates 5 0 5 8 0 5 8 5 8 8 51005100 AAR AAR ELA (m) Valley, ´ o Palcoco, Cordillera o San Francisco, o Palcoco, Cordillera ´ ´ ´ Real Cordillera Real Real Rı Cordillera Callejon- West Cordillera Callejon- East Junin-East 4800 Map of 1967 based on air Quelccaya Ice Cap (modern-E), Cordillera Ampato Nevado Sara Sara (modern-S), Cordillera Ampato Sara Sara I (NE), Cordillera Ampato Sara Sara II (NE), Cordillera Ampato Sara Sara I (SW), Cordillera Ampato Sara Sara II (SW), Cordillera Ampato C. Huanipaco/ Cocauro/Allcc. (NW), Cord. Ampato C. Huanipaco/ Cocauro/Allcc. (SW), Cord. Ampato C. Huanipaco/ Cocauro/Allcc. (SE#1), Cord. Ampato C. Huanipaco/ Cocauro/Allcc. (SE#2), Cord. Ampato Cordillera Vilcanota Jalacocha Valley, Cordillera Vilcanota 10 Huancane 11 Nevado Sara Sara 8 Nevado Huaytapallana 4800 GT (+ altitude modern glacier 9 Upismayo Valley, 14 Rı 13 Rı Site LGM snowline locality Modern 6,7 Cerros Cuchpanga 4900 Map of 1967 based on air ARTICLE IN PRESS 154 J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 37, 50 : : 0 0 ¼ ¼ Zo5 THAR 4600–4700 2:1 method; moraine4800 group 2.5:1 method; moraine Ck7   ; ; ; Glacier type LGM ELA (m) LGM ELA method Argollo, 1980, 1982 Servant and Fontes, 1984 Lauer and Rafiqpoor, 1986 Argollo, 1980, 1982 Seltzer, 1992 Argollo, 1980, 1982 Seltzer, 1992 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Dornbusch, 2000, 2002 Terminus altitude (m) 5800? 4100–4140 Valley  Headwall altitude (m) altitude (m) C2 2 7 C2 2 7 Cka 2 2 7 14 14 14 C137 14 10,460 10,460 33–34 8812 4 o 4 4 68.17 SSW 6088 5730 4240 Valley 4800–4980 THAR 67.24 W 5515 5400 4325 Valley 68.12 NE 6088 1984 À À À 1962 1962 19551955 No dates1955 No dates1955 0 No dates1955 0 No dates 51955 0 No dates 51955 8 0 No dates 5 No 8 dates 0 5 8 0 5 0 8 5 8 5 8 8  37&0.5 (ave.) 37&0.5 (ave.) : : 77&0.6 (ave.); 77&0.6 (ave.); 0 0 : : 0 0 ¼ ¼ ¼ ¼ 16.32 17.06 16.20 À À À THAR THAR Ames et al. (1988) Ames et al. (1988) Ames et al. (1988) Ames et al. (1988) Ames et al. (1988) Ames et al. (1988) Ames et al. (1988) Bolivia Bolivia 5085 AAR ?NA NA 5085 AAR NA5588 Average, glacier5588 inventory of Average, glacier5588 inventory of Average, glacier5413 inventory of 1955 Average, glacier5413 inventory of Average, glacier5432 inventory of No dates5558 Average, glacier inventory of Average, glacierNA inventory of 0NA 5NANA 8 1955 1955 No dates 1955 No dates 1955 0 No dates 0 No dates 5 0 5 8 0 5 8 5 8 8 5300 Not stated explicitly ) continued o Palcoco, Cordillera o San Francisco, o Palcoco, Cordillera ´ ´ ´ Milluni Valley, Cordillera Real Cordillera Real Real Cordillera Real Rı Real Nevado Solimana (N#1), Cordillera Ampato Nevado Solimana (N#2), Cordillera Ampato Nevado Solimana (N#3), Cordillera Ampato Nevado Solimana (SW#1), Cordillera Ampato Nevado Solimana (SW#2), Cordillera Ampato Nevado Solimana (SE), Cordillera Ampato Nevado Coropuna (SW), Cordillera Ampato Cerros Jollpa/ Yanahuara (SW), Cordillera Ampato Cerros Jollpa/ Yanahuara (S#1), Cordillera Ampato Cerros Jollpa/ Yanahuara (S#2), Cordillera Ampato Cerros Jollpa/ Yanahuara (E), Cordillera Ampato C. Huanipaco/ Cocauro/Allcc. (SE#3) Cordillera Apolobamba 16 Bolivia 15 Zongo Valley, 14 Rı 13 Rı Site LGM snowline locality Country Latitude Longitude Aspect Summit Table 1 ( 12 Nevado Ulla Khaya, ARTICLE IN PRESS J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 155 , 1: ¼ ain range. 37 : 0 ¼ Mark et al. (this volume) 4: Date is less than 3000 yr ¼ pect relative to climate gradients; 4600 3:1 method; moraine Ck10 4700 2.7:1 method; moraine Ck8   ; ; 7: Date is greater than 5000 yr fromthe target ; ; ¼ ; Seltzer et Seltzer, Seltzer, Seltzer, Seltzer et ; ; ; ; ; Heine, 1996 Heine, 1996 ; ; Gouze, 1987 Gouze, 1987 Gouze et al., Gouze et al., % % % ; ; a a a ; ; ller, 1985 ller, 1985 ller, 1985 ller, 1985 ¨ ¨ ¨ ¨ Wagnon et al., 1999 Wagnon et al., 1999 1986 1986 Seltzer, 1994a, b Seltzer et al., 1995 Mu Mu Mu al., 1995 1994 1994 Mu 1994 Seltzer, 1992 al., 1995 Servant et al., 1981 Servant and Fontes, 1984 Servant et al., 1981 Servant and Fontes, 1984 3: Date is less than 2000 yr fromthe target interval; DC ¼ 5: Chronology based on correlation with a generalized or global glaciation scheme; DC ¼ Dates DMC DC References ] 6: Date is less than 5000 yr fromthe target interval; DC 2: Chronology based on geomorphologic correlation of terminus position with radiometrically dated feature ¼ ¼ C227 14 C127 C127 C127 C127 C 223 C 227 14 14 14 14 14 14 10,970 21 cal kyr BP 3 (basal) 2 1 8420 9790 8420 8420 4 4 4 4 LGM date 4 o 5). ¼ 67.13 W 4560 4560 4400 Cirque 4460 THAR 67.24 W65.78 ? 5515 5400 ? 4000 ? Valley ? Valley? ? No ELA reported 65.78 ? ? ? ? Valley? ? No ELA reported 67.24 W 5515 5400 4280 Valley 1993 1982 1993 date À À À À À 2: Date is less than 1000 yr fromthe target interval; DC ¼ . Column DMC refers to dating method control and column DC refers to dating control, and follows the definitions given by 77; extrapolated— 77 1982 77 1982 77 1982 : : : : 0 0 0 0 ¼ ¼ ¼ ¼ Fig. 1 17.43 17.06 17.35 17.35 17.06 of Zongo Glacier Cord. Quimsa Cruz of Zongo Glacier Modern ELA method Modern ELA À À À À À 3: Chronology based on geomorphic correlation with radiometrically dated feature within region, where region may be an individual mountain or mount 100 AAR 100 AAR 100 AAR ¼ 5: Date is less than 4000 yr fromthe target interval; DC Æ Æ Æ ¼ 5050 5150 Observation, instrumentation 5050 5050 5150 Observation, instrumentation ELA (m) Bolivia Bolivia a ? No ELA reported NA 27,000 a ? No ELA reported NA 16,610 a Bolivia a Bolivia 8: Site is not associated with radiometric date (DMC ˜ ˜ ˜ ˜ 1: Chronology based on radiometric dating of terminus position; DMC ¼ ¼ 4: Chronology based on correlation with a radiometrically dated regional sequence; DMC o Kollpan o Kollpan o Kollpan o Kollpan ´ ´ ´ ´ ¼ Rı Choco Kkota Valley, Cordillera Quimsa Cruz Milluni Valley, Cordillera Real Choco Kkota Valley, Cordillera Quimsa Cruz Cordillera Quimsa Cruz Cordillera Real Rı Choco Kkota Valley, Cordillera Quimsa Cruz Choco Kkota Valley, Cordillera Quimsa Cruz Choco Kkota Valley, Cordillera Quimsa Cruz 18 Laguna Kollpa Kkota 5100 AAR 17 Rı 16 Choco Kkota Valley, 15 Zongo Valley, Site LGM snowline locality Modern 18 Laguna Kollpa Kkota Bolivia 17 Rı where DMC Site numbers correspond to numbers on Date is less than 500 yr fromthe target interval; DC within the glacier valley; DMC fromthe target interval; DC interval; DC In the case ofDMC isolated mountains, the dated feature must be within 50 km; in case of a mountain range, the feature must be within 200 km and have the same as ARTICLE IN PRESS 156 J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167

Fig. 2. Graphical representation of estimates of snowline depression at the LGM in the tropical Andes of South America. The size of the circle denotes the amount of snowline depression; the color of the circle ranks the dating associated with the feature used to make the estimate (ranking is relative to 21 cal kyr BP). Sites with no published estimates of snowline depression at the LGM are symbolized by squares. Thin gray lines are 3000-m contour lines; thick black lines mark political boundaries. graphic evidence of previous occupation by valley not older than 30 14C kyr BP, as it terminated above the glaciers. They identified the older Sucus advance and dated organic material underlying tills at 3500 m. the younger Potrerillos advance, which terminated at Chronological control for the Potrerillos advance 3850 and 3950 m, respectively. They speculated that is provided by 11 maximum-limiting radiocarbon the paleo-ELA must have been close to 4000–4100 m ‘‘in ages averaging 10,855 14CyrBP (12.8 cal kyr BP) and order to generate glacier ice’’ for the Potrerillos advance five minimum-limiting radiocarbon ages averaging (Fig. 2), but did not make an estimate for the Sucus 10,035 14CyrBP (11.3 cal kyr BP). The Potrerillos advance. The Potrerillos ELA estimate (suggesting an advance thus clearly postdates the LGM. ELA depression of 900 m) does not seem to be based on an explicit method. 3.3. Chimborazo-Carihuairazo Massif, Western Chronological control for the Sucus advance is Cordillera, 11 300 S, 781 500 W provided by seven minimum-limiting radiocarbon ages averaging 13,070 14CyrBP (15.6 cal kyr BP) on The Chimborazo-Carihuairazo Massif (Fig. 1, Site 3) plant material and peaty organic matter in sedi- is an ice-capped volcanic complex some 20–30 km in ments overlying till between two Sucus lateral moraines. diameter located near the southern end of the Western Six minimum-limiting radiocarbon ages averaging Cordillera of the Ecuadorean Andes. Geomorphic 11,720 14CyrBP (13.7 cal kyr BP) fromsedimentsun- evidence on Chimborazo (6310 m) and Carihuairazo derlying the Potrerillos advance date the deglaciation of (5020 m) suggests a complicated history of volcanic and the plateau after the Sucus advance. There are no glacial activity (Clapperton, 1990). Clapperton (1987a, maximum-limiting ages, so the Sucus advance may be b, 1990) identified four generations of glacial deposits on younger or older than 21 cal kyr BP, though probably the basis of field characteristics, obtained radiocarbon ARTICLE IN PRESS J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 157 dates that broadly distinguish Neoglacial, late-glacial, No moraines in the Peruvian Andes have been full-glacial, and older deposits, and calculated paleo- definitively dated to the LGM. Careful mapping in the ELAs and ELA depressions for each generation of Cordillera Oriental and Cordillera Blanca (Rodbell, moraines. 1991–1993) lacks conclusive bracketing ages to confirm Clapperton and McEwan (1985) identified three sets that the moraines date to the local LGM. Wright Jr. of moraines in the Rı´ o Mocha valley between Chimbor- (1983) obtained bracketing ages of 12 14C kyr BP azo and Carihuairazo. They assigned the moraines to (14 cal kyr BP) and 24 14C kyr BP for clayey sediments the LGM (Group 3), late glacial (Group 2), and in a core fromLaguna Junin, which he interpreted to Neoglacial (Group 1) stages based on location, mor- constrain the age of outwash sediments from LGM phological characteristics, and depth of volcanic ash glaciation. This has been updated by Seltzer et al. cover. Group 3 moraines extend to just below 3600 m (2000), who showed the LGM to be bracketed between altitude, Group 2 moraines to 4050 and 3900 m, and 21 cal kyr BP and 30 14C kyr BP. Smith et al. (2001, Group 1 moraines to 4300–4400 m. Clapperton (1987a) 2002a, b) have used cosmogenic dating techniques to placed the modern ELA on Chimborazo at approxi- identify moraines of the local LGM in valleys bordering mately 4800 m(eastern slope) and 4900 m(western the Junin Plain. Preliminary results indicate that these slope). Clapperton (1987a), using the median-altitude moraines are older than 21 cal kyr BP. A maximum age method (THAR ¼ 0:5), estimated full-glacial (LGM) of about 28 14C kyr BP reported by Mercer and Palacios ELAs on Chimborazo at 3880 m (eastern slope) and (1977) for moraines at 4100–4450 min the Upismayo 4090 m(western slope), indicating an ELA depression of Valley on the north side of the Cordillera Vilcanota 820–920 m. offered the prospect of bracketing ages for LGM Chronological control for the moraine sequences moraines, but Mercer’s later work (Mercer, 1982, in the Chimborazo-Carihuairazo Massif is minimal. 1984) resulted in a revision of the maximum age of the Clapperton and McEwan (1985) obtained ages moraines to about 14 14C kyr BP (16.8 cal kyr BP). of 10.6–11.4 14C kyr BP (12.7–13.4 cal kyr BP) from peat layers froma drained glacial lake basin located at 4.1. Cordillera Oriental, North-central Peru, 71 32– 480 an altitude of 3900–4000 mbetween the two volcanic S, 771 28– 340 W peaks and upvalley of the Group 2 moraines. Clapper- ton and McEwan concluded that the lake developed The Cordillera Oriental (Fig. 1, Site 4) is located in when glacial ice advanced and formed a dam across the the Amazon drainage basin and has also appeared in the Rı´ o Mocha valley. Clapperton and McEwan (1985) did literature as the Cordillera Central (e.g., Birkeland et al., not find any datable material associated with the Group 1989). The Cordillera has maximum summit elevations 3 (full-glacial) moraines, but they correlated those of about 4500 mand is not currently glaciated. Part of moraines with deposits overlying compacted peat on the section of the Cordillera Oriental discussed in the northern flanks of Carihuairazo (their site 3a), which Rodbell (1991–1993) contains two divides: a NW–SE they dated at 35,4407680/630 14C yr BP. trending main divide and a minor local divide to the west of the main divide. Rodbell interpreted moraines with steep proximal and 4. Peru distal slopes (25–351) as LGM moraines. In valleys of the Cordillera Oriental, the LGM terminal moraine North of about 101 S, the Peruvian Andes consist of marks a distinct change in valley morphology, from two northeast–southwest-trending, near-parallel chains, shallow and U-shaped upvalley to steep, deeply incised, the Eastern Cordillera (Cordillera Oriental, locally and V-shaped downvalley. Cordillera Blanca) and the Western Cordillera (Cordil- Topographic map coverage is lacking for much of the lera Occidental, locally Cordillera Negra), which are Cordillera Oriental, precluding the use of AAR and GT separated by incised valleys. South of about 101 S, the methods for ELA reconstruction (Porter, 2001). Rodbell two cordillera of the Peruvian Andes shift closer to (1992) estimated LGM ELAs using the THAR method. east–west-trending and are more commonly separated Where LGM terminal moraines were absent, he by high-altitude plateaus that increase in width toward estimated their location from the change in valley the south, terminating in the plateau that hosts Lago morphology. He used the elevation ‘‘at the base of the Titicaca, the Altiplano (3800 m). Unlike the Andes in steep slopes at the heads of cirque basins’’ as the Ecuador, the Peruvian Andes are largely non-volcanic; headwall elevation. In cases where multiple cirques fed volcanic peaks reappear south of 151 S. The highest LGM glaciers, Rodbell used the average headwall peaks in the Peruvian Andes include ice-covered Nevado elevation of all the major cirques. Where topographic Huascara´ n (6768 m) in the Cordillera Blanca (91 100 S, map coverage was absent, he measured altitudes in 771 350 W) and Nevado Ausangate (6384 m) in the the field with an altimeter, with an estimated accuracy Cordillera Vilcanota (131 450 S, 711 150 W). of 750 m. ARTICLE IN PRESS 158 J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167

Rodbell calculated LGM ELAs for the Cordillera Rodbell calculated LGM ELAs for the Cordillera Oriental using THAR values of both 0.2 and 0.4. His Blanca using THAR values of both 0.2 and 0.4. He results indicated that average ELAs at the LGM were estimated average ELAs at the LGM of about 3850785–3900770 mfor nine glaciers west of the local 42507110–44007100 mfor thirteen glaciers west of divide, 3540780–3640770 mfor nine glaciers west of the divide, and 42007170–43507150 mfor nine glaciers the main divide, and 3150740–3300780 mfor two east of the divide (Fig. 2). Rodbell found that the S–N glaciers east of the main divide. Rodbell calculated a and W–E slopes of the ELAs in the Cordillera Blanca S–N slope of 24 m/km and a W–E slope of 45 m/km were not significantly different fromzero. Rodbell for ELA altitude at the LGM. estimated ELA depressions at the LGM of 400–900 m Rodbell estimated ELA depression in the Cordillera west of the divide and 530–970 meast of the divide. Oriental at the LGM by comparing his calculated LGM Chronological control on the western side of the ELAs with an estimated modern glaciation threshold of Cordillera Blanca is provided by a minimum-limiting 4620 m( Seltzer, 1987). This comparison yielded ELA radiocarbon date of 13,2807190 14CyrBP (15.8 cal depression at the LGM of 750–950 mwest of the local kyr BP) on peat beneath gravel at about 6 mdepth in divide, 900–1150 mwest of the maindivide, and the Breque Valley (Rodbell, 1992, 1993; Rodbell 1100–1350 meast of the maindivide ( Fig. 2). and Seltzer, 2000). There are no maximum-limiting Chronological control in the Cordillera Oriental dates for the LGM moraines. east of the main divide is provided by a minimum- limiting radiocarbon date of 12,1007190 14CyrBP 4.3. Junin Plain/Cerros Cuchpanga/Cordillera Callejon, (14–15 cal kyr BP) on the basal 8 cmof a 428-cm ca. 101 400—111 000 S, 76– 771 W section of lake sediments on top of till in Laguna Baja in the Manachaque Valley (Birkeland et al., 1989; Rodbell, In the Andean Highlands of central Peru between 1992). This date provides a minimum date for initial about 101 300 and 111 100, a plateau known as the Junin deglaciation of Manachaque Valley. There are no Plain (Fig. 1, Site 7) separates cordillera to the west and maximum-limiting dates for the LGM moraines. east. The Junin Plain has an average altitude of 4100 m and is dominated by Laguna Junin, the second largest 4.2. Cordillera Blanca, North-central Peru, 91 28– 540 S, lake in Peru. The higher altitude Western Cordillera 771 13– 280 W currently has a far greater number of glaciers than the lower Eastern Cordillera, although both cordillera have The Cordillera Blanca (Fig. 1, Site 5) contains been extensively glaciated in the past. Wright Jr. (1983) numerous peaks above 6000 m, including the highest estimated the altitude of the snowline at approximately peak in Peru (Nevado Huascara´ n Sur, 6768 m), and is 4900 min the Western Cordillera and 4800 min the extensively glaciated. It forms the Continental Divide in Eastern Cordillera. this section of the Andes. Rodbell (1992) estimated the The Cerros Cuchpanga and the Cordillera Callejon modern ELA at 49857120 mfor twelve glaciers west of (ca. 101 450 S, 761 350 W; Fig. 1, Site 6) are two ridges in the Continental Divide and 50307110 mfor five glaciers the Western Cordillera that support modern glaciers. east of the divide. The Cerros Cuchpanga is the farther east and north of In the Cordillera Blanca, Rodbell (1991–1993) identi- the two ridges, while the Cordillera Callejon to the fied the LGM moraines (‘‘Laguna Baja’’) as those lying southwest has the steeper peaks. Maximum peak between numerous Holocene and late-Quaternary mor- altitudes in the Cerros Cuchpanga are about aines upvalley and two sets of older moraines beyond 5100–5200 m, including existing ice caps. The crest of the LGM ice limit. LGM moraines are characterized by the Cordillera Callejon is at an altitude of about steep proximal and distal slopes (25–351) and moderate 5000–5200 m( Instituto Geogra´ fico Militar, 1969). development of weathering posts on granite boulders. Wright Jr. (1983, 1984) identified deposits of two Rodbell (1991–1993) estimated LGM ELAs using the glaciations in the Junin region, largely on the basis of THAR method as constrained by the upvalley limit of morphostratigraphy of moraines and outwash: the lateral moraines that could be traced in the field or on younger Punrun phase and the older Rı´ o Blanco phase. 1:25,000 aerial photos. Terminus and headwall altitudes He viewed the Western Cordillera as the source region of LGM paleoglaciers were estimated from topographic for both phases. Wright dated basal lake sediments in maps. Rodbell used the elevation at the base of the steep sediment cores and obtained four radiocarbon ages slopes at the heads of cirque basins as the headwall ranging from 10 to 13.5 14C kyr BP (11.5–16.2 cal elevation of deglaciated cirques, or the base of the near- kyr BP), which he interpreted as minimum-limiting ages vertical ice walls located above modern cirque glaciers. for the time of recession of the last (Punrun) glaciation In cases where multiple cirques fed LGM glaciers, fromthe Junin Plain. Wright interpreted radiocarbon Rodbell used the average headwall elevation of all the dates of 24 14C kyr BP at the base and 12 14C kyr BP major cirques. (14.2 cal kyr BP) at the top of 9 mof clay in a long core ARTICLE IN PRESS J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 159 fromLaguna Junin as marking the beginning and analysis of topographic maps and aerial photographs to end of the Punrun glacial phase. Wright obtained a develop a glacial history for the region, Seltzer (1987) radiocarbon age of 442 14C kyr BP on organic lake concluded that a late-Pleistocene ice cap extended from sediment beneath the Punrun till, from which he the Nevado Huaytapallana onto the plateau to the west inferred that the Rı´ o Blanco glaciation is older than (ca. 4200–4600 m; Instituto Geogra´ fico Nacional, 1983) 42,000 14C yr. and down to elevations as low as 3400 mto the east, Wright calculated ELAs for the LGM by identifying which is some 1400 m lower than the modern ice margin cirques containing lakes on aerial photos and topo- (4800 min 1989). Wright Jr. et al. (1989) cited a graphic maps and using the cirque altitude as an modern snowline estimate of 4700–4800 mbased on estimate of the ELA at the LGM. He estimated ELAs the glaciation threshold method (Seltzer, 1987) for the of about 4600 min the Western Cordillera and about portion of the Eastern Cordillera that includes Nevado 4300 min the Eastern Cordillera, suggesting ELA Huaytapallana. depressions of 300 and 500 m, respectively (Fig. 2). Chronological control for the study was provided Wright estimated an ELA of 4400 m from a cirque on a by radiocarbon dating of basal lake sediments at bedrock hill on the Junin Plain (Cerro Quicay), from sites upvalley of late-Pleistocene terminal moraines which he inferred an ELA depression of 400 m. Wright’s (Fig. 2; Seltzer, 1987, 1990). Radiocarbon ages of 10,9607 estimates of ELA depression at the LGM are not 390 14CyrBP (13 cal kyr BP) fromLaguna Jero ´ nimo constrained by radiometric dating. Moreover, the (4450–4500 m) and 9,8207130 14CyrBP (11.2 cal estimates should be considered minimum depressions, kyr BP) from Laguna Pomacocha (4450–4500 m) pro- as the lip of the cirque may have been above the ELA at vided minimum-limiting ages for recession from the the LGM. LGM moraines (Seltzer, 1987, 1990; Instituto Geogra´ - Seltzer et al. (2000) obtained a 19-msedimentcore fico Nacional, 1983). There are no maximum-limiting fromLaguna Junin (11 1S, 761W). Based on magnetic dates for LGM moraines. susceptibility and radiocarbon dating of lacustrine sediments in the core, they concluded that the LGM 4.5. Cordillera Vilcanota/Quelccaya Ice Cap, ca. 131 occurred between 30 14C kyr BP and 21 cal kyr BP. 300–141 000 S, 701 500 W Radiocarbon dating on mollusks in the sediment indicated that the first drop in magnetic susceptibility The Cordillera Vilcanota (Fig. 1, Site 9) and occurred at about 21 cal kyr BP, which the authors Quelccaya Ice Cap (Fig. 1, Site 10) region of south- interpreted as the point at which glaciers retreated eastern Peru is located in the Eastern Cordillera of the behind their terminal moraines. The authors inferred a Peruvian Andes, about 100 kmeast of the city of Cusco. minor readvance between 21 and 16 cal kyr BP, followed The Cordillera Vilcanota and Quelccaya Ice Cap both by extensive glacial retreat after 16 cal kyr BP. Mollusks support modern glaciers, including the largest tropical near the base of the core gave a radiocarbon age of ice cap in the world. The Cordillera Vilcanota ex- 39,02071045 14C yr BP. tends approximately east–west for some 50–60 km. The Work by Smith et al. (2001, 2002a, b, 2003a, b, in highest peak in the Cordillera Vilcanota is Nevado press) in deglaciated valleys bordering the Junin Plain Ausangate (6384 m), located near the western end of the will provide direct dating of moraines by cosmogenic cordillera. The Quelccaya Ice Cap is located about dating techniques (10Be and 26Al). The valleys are all 10 kmsouth of the eastern end of the cordillera and relatively shallow in profile (o700 mfrombottomto about 40–50 kmeast–southeast of Nevado Ausangate. highest peak) and base level is fixed by the elevation of The Quelccaya Ice Cap has a summit altitude of 5743 m the Junin Plain (4100 m). Results to date (10Be) indicate (Nevado Joyllor Pun˜ una). There is evidence suggesting that terminal moraines of the LGM lie at altitudes of that the two massifs were covered by an expanded and 4250–4400 min three valleys on the eastern edge of the continuous ice cap during the LGM (e.g., Mercer and Junin Plain. The ELA calculated by the THAR method Palacios, 1977). for the LGM moraine in the longest valley is 4500–4600 m(THAR ¼ 0:5), indicating an ELA de- 4.5.1. Cordillera Vilcanota, Upismayo and Jalacocha pression of 200–300 m, based on a modern ELA of Valleys, 131 440 S, 711 170 W 4800 m( Wright Jr., 1983). On the north side of the Cordillera Vilcanota (Fig. 1, Site 9), Mercer and Palacios (1977) found evidence of 4.4. Nevado Huaytapallana, ca. 111 550 S, 751 030 W glaciation down to 3600 m, more than 1000 m below the termini of existing glaciers. In the Upismayo Valley, Nevado Huaytapallana (5557 m; Fig. 1, Site 8) rises seven sharp-crested moraines are grouped between above the dissected plateau east of the city of Jauja and 4150 and 4350 m, about midway between the limit of the northern Rı´ o Mantaro Valley, approximately glaciation and the modern termini. Mercer and Palacios 300 kmeast of Lima,Peru. Based on field work and (1977) obtained radiocarbon ages of 28,650 (+700/ ARTICLE IN PRESS 160 J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167

À770) 14C yr BP and 31,170 (+1330/À1600) 14CyrBP Mercer and Palacios (1977) estimated the modern on samples of a 10-m-thick peat layer buried by the ELA at about 5100 mon the north side of the Cordillera outermost moraine of the group of seven moraines. Vilcanota, where existing glaciers terminate at about The peat samples were collected at 4450 m directly 4600 m. They did not specify how they arrived at beneath glacial sediments and were interpreted as a that estimate. Mark et al. (2002) calculated an ELA maximum age for the moraine (Mercer and Palacios, depression (relative to modern) of 170 m for the 1977). maximum ice extent at the local LGM and 560 m at Mercer (1982, 1984) reported radiocarbon dates the Cenozoic maximum in the Upismayo Valley (Fig. 2). ranging fromabout 22 to 27.5 14C kyr frompeat located They used the THAR method (THAR ¼ 0:45) to beyond the outermost moraine (but apparently contin- calculate ELAs. uous with the peat buried by the moraine) in Upismayo Valley and a date of 20,7807250 14Cyr on peat 4.5.2. Quelccaya Ice Cap, Huancane´ Valley, 131 550 S, interbedded with sediment presumed to have eroded 701 500 W fromthe moraine surface. The latter date was originally The presence of sandy till and outwash above 4500 m thought to approximate the age of the moraine, but on the plain between Cordillera Vilcanota and the subsequent excavation and sampling of the original Quelccaya Ice Cap (Fig. 1, Site 10) suggests that the two surface of the peat layer within the front of the moraine massifs were covered by a continuous mass of ice during yielded several radiocarbon ages of 14 14C kyr BP the LGM (Mercer and Palacios, 1977; Mark et al., (16.8 cal kyr BP; Mercer, 1982, 1984). The younger 2002). Mercer and Palacios (1977) identified three end- ages caused Mercer to revise downward the original moraine belts in the Huancane´ Valley on the west side of estimate of the age of the moraine by at least 6000 yr. the massif that postdate the retreat of ice from the plain This revised age for the outermost moraine of the between the Cordillera Vilcanota and the Quelccaya Ice group of seven sharp-crested moraines in the Upismayo Cap. Mercer and Palacios referred to the belts as Valley is in accordance with a radiocarbon age of Huancane´ III, II, and I, in order of decreasing distance 14 14C kyr BP (16.8 cal kyr BP) on a peat lens located from the present ice margin (8, 4, and 1 km, respec- between till layers at 4020 min the adjacent Jalacocha tively). Radiocarbon dating provided a minimum-limit- Valley (Mercer and Palacios, 1977). ing age for the outermost moraine of 12,2407170 14Cyr Mark et al. (2002) completed additional radiocarbon (14.3 cal kyr BP) at 4750 m, but no maximum-limiting dating on the 10-m-thick peat layer that was overridden age (Mercer and Palacios, 1977). by the outermost moraine of the group of seven nested Lake records have supplied minimum-limiting ages moraines in the Upismayo Valley. They reported a but no maximum-limiting ages for the Huancane´ radiocarbon date of 41,52074430 yr BP on a sample advances. Rodbell and Seltzer (2000) reported an age collected at 4450 mfromthe bottomof the peat layer; of 10,870770 14CyrBP (12.8 cal kyr BP) frombasal this date provides a minimum age for the outer limit of organic material in Laguna Paco Cocha (4940 m), which glaciation farther downvalley (ca. 3600 m). Mark et al. is located 1 km downvalley from the modern ice limit (2002) dated the upper section of the peat layer at and is impounded by a Huancane´ II moraine. Mark 13,8807150 14CyrBP (16.7 cal kyr BP), which is a et al. (2002) reported an age of 11,1837109 14CyrBP maximum age for the group of nested moraines. Peat (13.1 cal kyr BP) frombasal organic material in accumulating over glacial silts in a bog 0.8 km upvalley Laguna Aconcancha (4780 m), which is located in a fromthe terminusof the local LGM moraines was dated tributary valley to Huancane´ Valley and shares the at 10,362773 14CyrBP(12.3 cal kyr BP). Huancane´ III terminus. Mark et al. (2002) cored Laguna Casercocha, which The modern snowline at the Quelccaya Ice Cap has is located at 4010 mon the northwestern side of been estimated at 5250 m (Thompson, 1979)to5300m Cordillera Vilcanota in a tributary valley northeast (Mercer and Palacios, 1977). Mark et al. (2002) of Upismayo Valley. The lake is not dammed by a calculated an ELA depression (relative to modern) of terminal moraine but lies downvalley of a number of 230 mat the Huancane ´ III ice extent and 360 mat the large, cross-cutting moraines. Mark et al. (2002) dated Cenozoic maximum in the Huancane´ Valley (Fig. 2). organic material overlying glacial silts in the core at They used the THAR method ðTHAR ¼ 0:45Þ to 15,6407100 14CyrBP (18.5 cal kyr BP), indicating a calculate ELAs. transition fromglacial to non-glacial sedimentation beginning shortly after 20,000 cal yr BP. Mark et al. 4.6. Cordillera Ampato, Western Cordillera, 151 f150–450 (2002) also cored moraine-dammed Laguna Comerco- S, 721 150–731 300 W cha, which is located about 6 kmeast of the Upismayo Valley at 4580 m. They dated basal lacustrine organic The Cordillera Ampato (Fig. 1, Site 11) is located in material from the core at 14,5007220 14CyrBP the Western Cordillera of southern Peru and includes (17.4 cal kyr BP). several glaciated volcanoes that are extinct or dormant. ARTICLE IN PRESS J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 161

Dornbusch (2002) reported recent (AD 1955) mean 5.1. Cordillera Apolobamba (Bolivia), 141 450–151 150 S, ELAs for three glaciated peaks, Nevado Sara Sara 681 450–691 150 W (altitude 5505 m; ELA 5200 m), Nevado Solimana (altitude 6093 m; ELA 5430 m), and Nevado Coropuna The section of the Eastern Cordillera known as the (altitude 6377 m; ELA 5640 m), based on averages of Cordillera Apolobamba (Fig. 1, Site 12) spans the data for individual glaciers taken fromthe glacier Peru–Bolivia border north of Lago Titicaca. The inventory prepared by Ames et al. (1988). Cordillera Apolobamba is separated from the Cordillera Dornbusch (2002) used aerial photographs, topo- Real to the southeast by the lower-altitude Cordillera graphic maps, and limited fieldwork to distinguish Mun˜ ecas and the valley of the eastward-flowing Rı´ o four sets of moraines on peaks in the Cordillera Conzata. The three cordillera formthe watershed Ampato. Dornbusch estimated Pleistocene ELAs between the Altiplano to the west and the Amazon ranging from4300 to 5400 mon the peaks that he Basin to the east (Lauer and Rafiqpoor, 1986). Ice- studied. This implies ELA depressions of 200–800 m covered peaks in the Cordillera Apolobamba include (Fig. 2). However, as Dornbusch reported no Nevado de Apolobamba (5999 m) and Nevado Ulla radiometric dating information for these peaks, Khaya (5617 m). Lauer and Rafiqpoor (1986) reported chronological control for these moraines is limited to the modern snowline as 5300 m, but did not state how relative dating among sets of moraines and comparison this was determined. with moraine sequences of similarly uncertain Lauer and Rafiqpoor (1986) conducted a glaciomor- age elsewhere in the southern Peruvian Andes (e.g., phologic study in several valleys in the western Dornbusch, 2000). foreland of the Cordillera Apolobamba between Nevado Ulla Khaya and the Rı´ o Suches to the west. They classified groups of moraines as middle or young Pleistocene on the basis of morphological criteria. 5. Bolivia Their middle Pleistocene advance reached the base of the foreland of the cordillera (3200 m). They distin- The Bolivian Andes consist of two northwest– guished three young Pleistocene advances that were southeast-trending, near-parallel mountain chains, the confined to valleys and did not extend below Eastern Cordillera (Cordillera Oriental, locally Cordil- 3700–4000 m. lera Apolobamba, Cordillera Real, and Cordillera Chronological control for the Lauer and Rafiqpoor Quimsa Cruz) and the Western Cordillera (Cordillera study (Fig. 2) was limited to radiocarbon ages that were Occidental), which are separated by a high-altitude o9 14C kyr BP (10.2 cal kyr BP). A sample of fossil soil plateau referred to as the Altiplano (3800 m). The collected at 4460 min the Jankho Khala valley (down- Western Cordillera of the Bolivian Andes, which is valley fromLaguna Jankho Khala) gave an age of volcanic, includes the tallest peaks in Bolivia (46500 m). 8,812745 yr BP (presumably 14C yr BP) for a fossil soil The Eastern Cordillera, which borders the Amazon layer in a late-glacial fluvial terrace deposit bordering Basin to the east and receives more precipitation morainal material of their Canlaya stade (which they (Johnson, 1976), is generally lower in altitude and more refer to as ‘‘Hochglaziel’’). All other radiocarbon dates dissected than the Western Cordillera. Extreme aridity were younger than 8.8 14C kyr BP. south of about 181S has limited the development of glaciers to peaks in excess of 6000 maltitude 5.2. Cordillera Real, 151 450–161 400 S, 671 400–681 350 W (Clapperton, 1993). No moraines in the Bolivian Andes have been 5.2.1. Overview definitively dated to the LGM. Inferred maximum- The Cordillera Real extends approximately 100 km limiting radiocarbon ages of 33–34 14C kyr BP from northwest fromthe city of La Paz, terminating at the the Rı´ o San Francisco drainage in the northern Rı´ o Sorata/Rı´ o Conzata drainage basin. The Cordillera Cordillera Real (e.g., Argollo, 1980) need to be Real is bordered on the southwest by the Altiplano and confirmed. Bracketing dates of 16.6 14CkyrBP Lago Titicaca (3810 m) and on the northeast by the (19.8 cal kyr BP) and 27 14C kyr BP fromRı ´ o Kollpan˜ a forested Yungas region perched above the Beni lowlands (e.g., Servant et al., 1981; Gouze, 1987) are difficult at the western edge of the Amazon Basin. Summit to evaluate because of the lack of information altitudes in the Cordillera Real exceed 6000 mand much about the sample locations, geomorphic setting, and of the range is currently glaciated. Ice-covered peaks analytical procedures. Seltzer (1994a) dated basal in the Cordillera Real include Nevado Ankohuma sediments in a core from moraine-dammed Laguna (6388 m) and Nevado Huayna Potosı´ (6088 m). Jordan Kollpa Kkota in the Eastern Cordillera and concluded and Finsterwalder (1992) mapped glaciers and estimated that the lake had not been glaciated since at least modern ELAs ranging from 5040 m (east side) to 5550 m 20 cal kyr BP. (west side) for the Illampu-Ancohuma region of the ARTICLE IN PRESS 162 J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 northern Cordillera Real. Seltzer (1992) calculated an and the comment by Argollo (1980) suggesting that average modern ELA of 5100 min the Rı ´ o Palcoco existing dates for the deposit are not adequate] valley on the western side of the Cordillera Real. suggest that additional sampling of the peat deposits Francou et al. (1995) estimated a modern ELA of would increase confidence in these dates as 5300 min 1991–1992 [El Nin ˜ o Southern Oscillation definitive maximum-limiting ages for the Choqueyapu (ENSO) year] and 5100–5150 min 1992–1993 (non- II phase. ENSO year) for the Zongo Glacier on the eastern side of Nevado Huayna Potosı´ ; the altitude of the ELA under steady-state conditions is 5150 m( Wagnon et al., 1999). 5.2.3. Rı´o Palcoco, 161 100 S, 681 200 W Early workers in the Cordillera Real identified four Argollo (1980, 1982) and Seltzer (1992) worked in the major glaciations in the vicinity of La Paz (Servant and Rı´ o Palcoco valley (161 100 S, 681 200 W; Fig. 1, Site 14), Fontes, 1978), fromoldest to youngest: Calvario, which has an extensive moraine system in its lower Kaluyo, Sorata, and Choqueyapu, for which two reaches. Argollo divided the moraines into two groups, advances (I and II) were identified (Troll, 1929; Troll Sorata and Choqueyapu. He assigned a mid-Pleistocene and Finsterwalder, 1935; Dobrovolny, 1962; Servant, age to the lower, rounded, more weathered Sorata 1977). The oldest moraines descend to 3800–3900 m, moraines, largely on the basis of morphostratigraphic approximately 1000 m below modern glacier termini characteristics, and a late-Pleistocene age to the young- (Servant and Fontes, 1978). er, sharp-crested Choqueyapu moraines, based on a radiocarbon age of 16.6 14C kyr BP (19.8 cal kyr BP) 5.2.2. Rı´o San Francisco, 151 510 S, 681 360 W on peat in Choqueyapu moraines from the Rı´ o The Rı´ o San Francisco (Fig. 1, Site 13) is located Kollpan˜ a valley (see separate discussion below; e.g., near Nevado Illampu (6382 m) at the northern end of Servant et al., 1981). the Cordillera Real. Argollo (1980) reported radio- Seltzer (1992) mapped glacial limits in the Rı´ o carbon ages of 33,5207460 14C yr BP and 33,6507500 Palcoco drainage and in several other valleys on the 14C yr BP (shown on the cross-section of the valley as western side of the Cordillera Real. He calculated the 35,6507500) on samples of peat in the valley of the Rı´ o modern and late-Pleistocene ELAs using the THAR San Francisco (Fig. 2). Argollo (1980) described the and AAR methods. He calculated an average modern samples as peat reworked by a glacial deposit, which he ELA of 5100740 m(AAR ¼ 0:6) to 5140740 m classified as a moraine or mudflow, and commented that (THAR ¼ 0:5), based on the dimensions of four existing ‘‘at any rate we still do not have sufficient dates with small glaciers in the valley. He used the upper limit of respect to the age of this deposit’’ [translated here from lateral moraines (4700 m) as a means of making a the original Spanish]. Argollo (1982) reported the direct estimate of paleo-ELAs. He reconstructed a late- same radiocarbon ages with additional details about Pleistocene paleoglacier terminating 0.4 kmdown- the sample materials. Sample ]453 (reported as valley of Lago Taypi Chaka Kkota (4300 m) and 35,6507500 14C yr BP in the text, 35,6207500 in the calculated an ELA of 4880 m(AAR ¼ 0:6) to 4860 m Appendix) was a fragment of reworked peat from within (THAR ¼ 0:5). These calculations indicate a late- a moraine. Sample ]458 (33,5207460 14C yr BP) was Pleistocene ELA depression of 220–280 m, based on collected froma peat layer between two clay layers ELAs above the upper limit of lateral moraines (Fig. 2). overlain by the moraine. Using THAR and AAR values of 0.37 and 0.77, Argollo (1980, 1982) provided only latitude and respectively, the paleo-ELA estimates approach 4700 m longitude for the sample locations. Servant and Fontes and the calculated late-Pleistocene ELA depression (1984) included Rı´ o San Francisco ages of 33,5207460 increases to about 340–360 m. and 35,6507500 14C yr BP in a compilation table and Seltzer (1992) cored sediments in five lakes and provided a sample altitude of 4020 m for both samples. collected seven peat samples within the Choqueyapu It seems likely that these are the same samples as those moraine limits. Chronological control for the Rı´ o reported by Argollo (1980, 1982), although both the Palcoco valley moraines was provided by radiocarbon latitude and longitude in Servant and Fontes’ dates on material from basal lake sediments in cores table differ fromthose in Argollo (1982) by 1’, the fromfour lakes. The oldest radiocarbon age sample ID for the age of 33,5207460 14C yr BP was (10,4607140 14C yr BP, 12.5 cal kyr BP) was on sedi- listed as 558 instead of 458, and the sampler was listed as ments from the lake located farthest downvalley (Lago Servant. Taypi Chaka Kkota), which provided a minimum- Argollo (1980) interpreted the radiocarbon ages of limiting age for the Choqueyapu moraines. There are 33–35 14C kyr BP as maximum-limiting ages for the currently no maximum-limiting ages for LGM moraines Choqueyapu II phase of glaciation. Several factors [the in the Rı´ o Palcoco valley. No moraines corresponding lack of detail about the sample settings, the slight to the LGM age of 21 cal kyr have been identified in the confusion over the radiocarbon age of the older sample, Rı´ o Palcoco valley. ARTICLE IN PRESS J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 163

5.2.4. Milluni and Zongo Valleys, 161 12– 210 S, 681 Smith et al. (2003a, b, in press) have obtained 7– 100 W preliminary cosmogenic dating results (10Be) for mor- The Milluni and Zongo Valleys (Fig. 1, Site 15) are aines in the Milluni and Zongo Valleys. Moraines located 10–40 kmnorth of the city of La Paz in the located about 5 kmsouth of Lago Milluni in the Milluni Cordillera Real. Mu¨ ller (1985) completed a detailed Valley have been sampled at 4600 mand dated to map of moraines in Zongo Valley and tributary valleys. 34–23 10Be kyr BP. Moraines located near Laguna She assigned moraines in Zongo Valley to nine groups, Jankho Kkota at 4650 min the Milluni Valley have Zo1–Zo9, in order of increasing distance downvalley. been dated to 13–10 10Be kyr BP. Moraines located As shown on Mu¨ ller’s moraine map for Zongo near Laguna Viscachani at 3800–4100 min the Zongo Valley, moraines located between altitudes of 4500 and Valley have been dated to 15–11 10Be kyr BP, which is 4000 mwere assigned to groups Zo3–Zo5; moraines consistent with the basal age of the peat in the lake located between 4000 and 3000 mwere assigned to (11 cal kyr BP; Seltzer et al., 1995). The cosmogenic groups Zo6–Zo9. Mu¨ ller calculated snowline depres- dating results for Zongo Valley (Smith et al., 2003b, in sions for groups Zo3–Zo6 and group Zo9 using the ‘‘2:1 press) suggest that the LGM glacier terminus extended method’’, relative to a modern snowline of 5050–5110 m farther downvalley than previous authors (e.g., Mu¨ ller, that she determined using geomorphic features: 195 m 1985; Heine, 1995b, 1996) have suggested. (Zo3), 270 m(Zo4 and Zo5), 360 m(Zo6), and 520 m (Zo9). Mu¨ ller considered the group Zo5 moraines, 5.3. Cordillera Quimsa Cruz, 161 470–171 060 S, 671 which terminate at 4100–4140 m( Instituto Geogra´ fico 120–671 350 W Militar, 1996) to be the LGM moraines (Heine, 1995b). Mu¨ ller (1985) included a figure illustrating the extent of Mu¨ ller (1985) mapped moraines over a large area of the glacier that produced the Zo5 moraines. The the Cordillera Quimsa Cruz (Eastern Cordillera; Fig. 1, snowline for the glacier is shown lying between the Site 16), including the glaciated Choco Kkota Valley 4600-mand 4700-mcontour lines. (161 550 1600,671 290 3800 W) on the southwest side of the Seltzer (1992) estimated a late-Pleistocene ELA of cordillera. Mu¨ ller listed modern snowline in the Choco 4800 m(THAR ¼ 0:37) to 4980 m(THAR ¼ 0:50) for Kkota Valley as 5050 m, with the headwall at approxi- Milluni Valley (Fig. 2). Seltzer calculated ELA depres- mately 5400 m and the terminus at 4620 m. She noted, sions of 300–400 mrelative to his calculated modern however, that the lateral moraines extended more than ELA of 5200–5300 m. Seltzer’s late-Pleistocene ELA 100 mhigher than the snowline calculated by the ‘‘2:1 estimates indicate a smaller ELA depression of method’’. Mu¨ ller presented the altitudes of ten older 200–350 mrelative to the modern steady-state ELA terminal moraines, including those of a sharp-crested of 5150 mbased on glaciological observations of moraine (Ck7, 4325 m) about 6 km from the modern Zongo Glacier (Wagnon et al., 1999). glacier and two older moraines (Ck8, 4280 m, and Ck10, Heine (1996) mapped moraines in both Milluni Valley 4000 m) located farther downvalley. Mu¨ ller calculated a and Zongo Valley and assigned themto seven age snowline depression of 250 mfor moraine Ck7 groups based on morphostratigraphy and periglacial (4800 m; ‘‘2.5:1 method’’) and snowline depressions features: M I (Little Ice Age) through M VII (older than of 345 m( 4700 m; ‘‘2.7:1 method’’) and 455 m marine isotope stage 5); Heine had previously presented (4600 m; ‘‘3:1 method’’) for the two older moraines the age groups in the reverse order (i.e., M I oldest, M downvalley (Fig. 2). VII youngest; Heine, 1995b). Heine (1996) assigned the Chronological control for Mu¨ ller’s study was pro- moraines that dam Lago Jankho Kkota (altitude vided by radiocarbon dating. The oldest radiocarbon 4570 m) in Milluni Valley, multiple small moraines at age obtained in the Choco Kkota Valley was reported as altitudes of 4100–4200 min the axis of Zongo Valley 84207130 yr BP (presumably 14C yr BP) on peat from [group Zo5 of Mu¨ ller (1985)], and moraines damming an altitude of 4335 m. The sample was collected from a Laguna Viscachani at altitudes of 3700–3800 min peat layer exposed in a streamcut on the downvalley Zongo Valley to group M IV (LGM). side of moraine Ck7. This date is a maximum age for Seltzer et al. (1995) reported radiocarbon ages for moraine Ck7 and a minimum age for moraines Ck8 and three sites close to the modern ice front in Milluni Ck10, but there are no bracketing ages for the older and Zongo Valleys. The basal age of peat beside moraines. Lago Milluni (4540 m, Milluni Valley) was 10,9707 230 14CyrBP (13 cal kyr BP). The base of Charquini 5.4. Rı´o Kollpan˜a, 171 210 S, 651 470 W peat bog (4700 m, Milluni Valley) farther upvalley near Laguna Jankho Kkota was 9,5607120 14CyrBP A compilation table in Servant et al. (1981) included (11 cal kyr BP). The basal age of peat in Laguna an age of 16,6107130 14CyrBP(19.8 cal kyr BP) for a Viscachani (3760 m, Zongo Valley) was 97907 sample (sample number MS-79-2A) collected in the Rı´ o 70 14CyrBP(11.2 cal kyr BP). Kollpan˜ a valley at 171 210 S, 651 470 W(Fig. 2). The ARTICLE IN PRESS 164 J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 stratigraphic setting of the 16.6 14C kyr sample was LGM in Bolivia. Seltzer calculated an ELA depression described as ‘‘peat reworked (or overrun) at the base of of about 600 mfor the glaciation that produced the moraines of the last full-glacial’’ [translated here from moraine that dams Laguna Kollpa Kkota at 4400 m the original French]. The sample altitude was not more than 20,000 cal yr BP (Fig. 2). given, nor was the sample discussed in the text. A compilation table in Servant and Fontes (1984) included ages of 16,6107130 14C yr BP (MS-79-2A) and 6. Discussion and conclusions 27,00071200 14C yr BP (MS-79-5) for samples collected at 3700 min the Rı ´ o Kollpan˜ a valley. Different, The modern glaciers of the tropical Andes are a small probably erroneous, coordinates were given: 171 210 S, remnant of the ice that occupied the mountain chain 681 480 W, which placed the samples on the Altiplano. during past glacial periods. Glacial ice has descended The site was not discussed in the paper; a note indicated more than a kilometer in altitude from present ice limits only that the samples were collected by Servant and that in many locations at least once during the Quaternary they consisted of peat or organic silt. A compilation (e.g., Clapperton, 1993). We know of no moraines in table in Gouze et al. (1986) again included the 16.6 and tropical South America that have been definitively dated 27 14C kyr BP ages, but gave the same coordinates as in to 21 cal kyr BP. Although rare, there are examples of Servant and Fontes (1984). Gouze et al. noted that the moraines that can be bracketed between about 16.6 14C kyr age required confirmation. Gouze (1987) 10 14C kyr and 30 14C kyr BP. Typically, only mini- included the 16.6 and 27 14C kyr BP ages [also with the mum-limiting ages are available. Many moraines have Servant and Fontes (1984) coordinates] in a compilation been associated with minimum-limiting ages of about table in his dissertation and again noted that the 9–12 14C kyr BP (10.2–14 cal kyr BP). 16.6 14C kyr age required confirmation. Servant et al. The extent of the LGM in the equatorial Andes of (1995) provided coordinates close to those published in Ecuador is loosely constrained. Radiocarbon dates 1981 (171 180 S, 651 450 N[sic]) in a discussion of work in suggest that LGM terminal moraines were deposited progress in Rı´ o Kollpan˜ a. The lack of published below 4200 mon deglaciated Volca´ n Pichincha (4784 information about the correct sample locations, geo- m; Heine, 1995), at least 750 m below modern glacier morphic setting, and analytical procedures reduces the termini near Papallacta Pass northwest of Volca´ n utility of these radiocarbon ages, as do the cautionary Antisana (Clapperton et al., 1997), and at least 550 m statements of the authors themselves. below modern glacial termini in the Rı´ o Mocha valley between Chimborazo and Carihuairazo (Clapperton 5.5. Laguna Kollpa Kkota, 171 260 S, 671 080 W and McEwan, 1985). Many workers have concluded that the most extensive Laguna Kollpa Kkota (Fig. 1, Site 18) is a cirque lake glacial features in the Peruvian Andes were deposited located at 4400 mon the western slope of the Eastern before the LGM (e.g., Wright Jr., 1983, 1984; Rodbell, Cordillera of the Bolivian Andes, about 60 kmsoutheast 1991; Smith et al., 2001; Dornbusch, 2002), but no single of the Choco Kkota Valley in the Cordillera Quimsa value for snowline depression at the LGM emerges from Cruz (Mu¨ ller, 1985). Laguna Kollpa Kkota is dammed the literature. In the Junin region, cosmogenic dating of by a moraine, but there are no moraines between the moraines has demonstrated that the local LGM was a lake and the headwall of the valley (4560 m) or below the relatively minor event in which glaciers descended lake-damming moraine (o4400 m). The snowline during 400–500 m below the terminus of the one remaining the late Pleistocene (12–14 kyr BP; extrapolated from small glacier in the neighboring crest and only about the Cordillera Quimsa Cruz; Mu¨ ller, 1985) was about half as far downvalley as previous glaciers (Smith et al., 4620 m, which is above the headwall of the Kollpa 2001, 2002a, b). Workers relying on minimum-limiting Kkota valley. Modern snowline, also extrapolated from radiocarbon ages have concluded that LGM snowline the Cordillera Quimsa Cruz (Mu¨ ller, 1985), is approxi- depression may have been as small as 300 m (Wright Jr., mately 5100 m. 1983, 1984) and as large as 1350 m( Rodbell, Seltzer (1994a) dated basal lacustrine sediments from 1991–1993), suggesting that local conditions affected cores collected in Laguna Kollpa Kkota. Seltzer glacier expansion. interpreted dates of 17,6707120, 17,5807170, and As in the Peruvian Andes, the most extensive 17,6907780 14C yr BP as minimum dates for the glacial glaciations in the Bolivian Andes are widely assumed advance that predated the late Pleistocene advance of to predate the LGM (e.g., Servant and Fontes, 1978; 12–14 ka BP seen in the Cordillera Quimsa Cruz. Lauer and Rafiqpoor, 1986; Heine, 1996). Direct dating Calibrated ages for these dated sediments are of moraines in the Milluni and Zongo valleys (Cordillera 420,000 cal yr BP. Seltzer concluded that the coring site Real) using cosmogenic isotopes suggests that LGM had not been glaciated since at least 20,000 cal yr BP. ice extended below 4650 min the Milluni Valley At present this may be the closest limiting age for the and below 3800 min the Zongo Valley ( Smith et al., ARTICLE IN PRESS J.A. Smith et al. / Quaternary International 138– 139 (2005) 145–167 165

2003a, b). Minimum-limiting radiocarbon ages place the Snowline Workshop in Glasgow, Scotland, 19–22 terminus of the LGM glacier below 4300 m in Rı´ o September, 2002, which provided the impetus for this Palcoco valley (Cordillera Real), suggesting that the paper. We thank D. Sugden, S. Harrison, and an LGM snowline depression was probably greater than anonymous reviewer for careful reviews of the manu- 220 m( Seltzer, 1992). Minimum-limiting radiocarbon script. dating in the Choco Kkota valley (Cordillera Quimsa Cruz) suggests that the LGM glacier terminated below 4300 mand that the LGM snowline depression was References greater than 250 m( Mu¨ ller, 1985). About 60 kmsouth- east of the Cordillera Quimsa Cruz, minimum-limiting Ames, A., Dolores, S., Valvederre, A., Evangelista, P., Corcino, D., radiocarbon dating at Laguna Kollpa Kkota indicates Ganvini, W., Zu´ n˜ iga, Z., Gomez, V., 1988. Inventario de glaciares that the maximum glaciation prior to 20 cal ka del Peru´ . Unidad de Glaciologı´ a e Hidrologia, Huaraz, Peru, 173pp terminated at 4400 m, suggesting a snowline depres- (in Spanish). Argollo, J., 1980. Los Pie de Montes de la Cordillera Real entre los sion of 600 m( Seltzer, 1994a). Valles de La Paz y de Tuni: Estudio Geolo´ gico, Evolucio´ n Plio- Two things emerge from this review of the LGM Cuaternaria: Tesis de Grado, Departamento de Geosciencias, snowline literature for tropical South America. First, Facultad de Ciencias Puras y Naturales, Universidad Mayor de there is considerable variation in the magnitude of LGM San Andre´ s, La Paz, Bolivia, 100pp (in Spanish). ´ snowline depression in the tropical Andes. Estimates of Argollo, J., 1982. Evolution du Piedmont Ouest de la Cordille´ re Royale (Bolivie) au Quaternaire. The`se 3e`me Cycle d’Enseignement snowline depression at individual locations vary by Supe´ rieur, l’Universite´ d’Aix—Marseille II, Faculte´ des Sciences de about a factor of four. Both precipitation gradients and Luminy, 116pp (in French). local factors such as topography, debris cover, cloudi- Benn, D.I., Owen, L.A., Osmaston, H.A., Seltzer, G.O., Porter, S.C., ness and shading probably played significant roles in Mark, B., 2005. Reconstruction of equilibrium-line altitudes for determining LGM glacier extent, as they do today tropical and subtropical glaciers. Quarternary International, this volume, doi:10.1016/j.quaint.2005.02.003. (Kaser and Osmaston, 2002). Second, there is still no Birkeland, P.W., Rodbell, D.T., Short, S.K., 1989. Radiocarbon dates robust radiometric chronology for the LGM in the on deglaciation, Cordillera Central, northern Peruvian Andes. tropical Andes. We must generally rely on minimum- Quaternary Research 32, 111–113. limiting radiocarbon dating and a small but growing Clapperton, C.M., 1987a. Glacial geomorphology, Quaternary glacial number of cosmogenic ages. sequence and palaeoclimatic inferences in the Ecuadorian Andes. In: Gardiner, V. (Ed.), International Geomorphology 1986: Cosmogenic dating of moraines may be able to Proceedings of the First International Conference on Geomor- provide absolute dating with sufficient accuracy to phology, Part II. Wiley, Chichester, pp. 843–870. identify deposits of the local LGM. Ongoing work in Clapperton, C.M., 1987b. Maximal extent of late Wisconsin glaciation Peru and Bolivia by Smith et al. (2001, 2002a, b, 2003a, in the Ecuadorian Andes. Quaternary of South America and b) demonstrates the utility of cosmogenic dating in Antarctic Peninsula 5, 165–179. Clapperton, C.M., 1990. Glacial and volcanic geomorphology of the expanding the existing glacial chronologies. Results to Chimborazo-Carihuairazo Massif, Ecuadorian Andes. Transac- date suggest that the local LGM may have occurred late tions of the Royal Society of Edinburgh: Earth Sciences 81, 91–116. in marine isotope stage 3 (30–35 cal kyr BP) rather Clapperton, C.M., 1993. Quaternary Geology and Geomorphology of than at 21 cal kyr BP (Smith et al., in press). South America. Elsevier, Amsterdam 779pp. Extensive areas of the tropical Andes that once hosted Clapperton, C.M., McEwan, C., 1985. Late Quaternary moraines in the Chimborazo area, Ecuador. Arctic and Alpine Research 17, glaciers are now completely deglaciated. As a result, 135–142. modern snowline estimates for much of the Andes must Clapperton, C.M., Hall, M., Mothes, P., Hole, M.J., Still, J.W., rely on extrapolation froma few locations in which Helmens, K.F., Kuhry, P., Gemmell, A.M.D., 1997. A Younger existing glaciers have been observed. Reliance on Dryas icecap in the equatorial Andes. Quaternary Research 47, information from remote glaciers increases the uncer- 13–28. Dobrovolny, E., 1962. Geologı´ a del Valle de La Paz. Ministerio de tainty associated with paleosnowline estimates. In the Minas y Petro´ leo, Departamento Nacional de Geologı´ a, Boletı´ n absence of reliable dating and consistent methodology, No. 3, La Paz, Bolivia. 153pp (in Spanish). use of paleosnowline estimates in climate modeling Dornbusch, U., 1998. Current large-scale climatic conditions in efforts and comparison of snowline estimates should be southern Peru and their influence on snowline altitudes. Erdkunde undertaken with caution. Additional research efforts are 52, 41–54. Dornbusch, U., 2000. Pleistocene glaciation of the dry western needed to augment the inventory of paleosnowline Cordillera in southern Peru (141250–151300 South). Glacial Geology estimates and their paleoclimate implications. and Geomorphology, http://boris.qub.ac.uk/ggg/papers/full/2000/ rp012000/rp01.html. Dornbusch, U., 2001. Correspondence on: Klein et al., 1999, Modern Acknowledgements and last local glacial maximum snowlines in the central Andes of Peru, Bolivia, and northern Chile. 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