Latest Pleistocene and Holocene Glacial Events in the Colonia Valley, Northern Patagonia Iceﬁeld, Southern Chile

JOURNAL OF QUATERNARY SCIENCE (2016) ISSN 0267-8179. DOI: 10.1002/jqs.2847

Latest Pleistocene and Holocene glacial events in the Colonia valley, Northern Patagonia Iceﬁeld, southern Chile

DAVID A. NIMICK,1* DANIEL MCGRATH,2 SHANNON A. MAHAN,3 BEVERLY A. FRIESEN3 and JONATHAN LEIDICH4 1U.S. Geological Survey, 3162 Bozeman Avenue, Helena, MT 59601, USA 2U.S. Geological Survey, Anchorage, AK, USA; and Geosciences Department, Colorado State University, Fort Collins, CO, USA 3U.S. Geological Survey, Lakewood, CO, USA 4Patagonia Adventure Expeditions, Cochrane, XI Region, Chile Received 15 November 2014; Revised 25 January 2016; Accepted 13 February 2016

ABSTRACT: The Northern Patagonia Icefield (NPI) is the primary glaciated terrain worldwide at its latitude (46.5–47.5˚S), and constraining its glacial history provides unique information for reconstructing Southern Hemisphere paleoclimate. The Colonia Glacier is the largest outlet glacier draining the eastern NPI. Ages were determined using dendrochronology, lichenometry, radiocarbon, cosmogenic 10Be and optically stimulated luminescence. Dated moraines in the Colonia valley defined advances at 13.2 0.95, 11.0 0.47 and 4.96 0.21 ka, with the last being the first constraint on the onset of Neoglaciation for the eastern NPI from a directly dated landform. Dating in the tributary Cachet valley, which contains an ice-dammed lake during periods of Colonia Glacier expansion, defined an advance at ca. 2.95 0.21 ka, periods of advancement at 810 49 cal a BP and 245 13 cal a BP, and retreat during the intervening periods. Recent Colonia Glacier thinning, which began in the late 1800s, opened a lower-elevation outlet channel for Lago Cachet Dos in ca. 1960. Our data provide the most comprehensive set of Latest Pleistocene and Holocene ages for a single NPI outlet glacier and expand previously developed NPI glacial chronologies. Copyright # 2016 John Wiley & Sons, Ltd.

KEYWORDS: Colonia Glacier; cosmogenic nuclide; glacial lake outburst flood; radiocarbon; Lago Cachet Dos.

Introduction Hemisphere glacial history and our ability to corroborate reconstructed temperature records. The Northern and Southern Patagonia Icefields (Fig. 1) form The Colonia valley (Figs 1 and 2) on the eastern side of the the largest continental ice mass in the world outside of NPI contains glacial features that date back ca. 13 ka and Antarctica and Greenland (Loriaux and Casassa, 2013) and thus provide an important constraint on Patagonia Icefield occupy the only terrain (except for very southern New glacial history for the period between the LGM and the late Zealand) glaciated at their latitude during the Late Pleistocene 1800s. The Colonia Glacier, with an ice area of 288 km2 in and Holocene. Changes in the volume and extent of these 2001, is the fifth largest of 24 main outlet glaciers (Fig. 1) icefields are tied closely to changes in climate (Glasser et al., draining the NPI (Rivera et al., 2007). Because it is the largest 2004), and thus mapping and dating these fluctuations offers outlet glacier on the east side of the NPI and drains the important and unique temporal information on past climatic central part of the icefield, the Colonia Glacier is probably a changes in the Southern Hemisphere. sensitive proxy of icefield changes. Glacial landforms in the Most research on the glacial geology of the Northern valley have been mapped in the field (Tanaka, 1980; Harrison Patagonia Icefield (NPI) has focused on the modern ca. and Winchester, 2000) and from visible satellite imagery 150-year period. This research has inventoried and dated the (Glasser et al., 2009, 2012), but dating has been restricted substantial reductions in volume and areal extent of ice as the to landforms younger than ca. 150 years (Harrison and NPI and its outlet glaciers retreated from late-1800s maxi- Winchester, 2000). mum positions (e.g. Harrison et al., 2007; Rivera et al., 2007; The rapid retreat of NPI outlet glaciers during the past Davies and Glasser, 2012; Loriaux and Casassa, 2013). Other century (Harrison et al., 2007; Davies and Glasser, 2012) has studies have examined the eastward extension of the icefield increased the area of proglacial lakes surrounding the NPI by almost 200 km into Argentina during the Last Glacial (Loriaux and Casassa, 2013) and, more importantly, the Maximum (LGM) (e.g. Kaplan et al., 2004; Hein et al., 2010), frequency of catastrophic glacial lake outburst floods (GLOFs) a regional advance of NPI outlet glaciers during the Latest (Harrison et al., 2006; Dussaillant et al., 2010). Most of the Pleistocene and early Holocene (Glasser et al., 2006, 2012; known GLOFs originating from the NPI during the past Harrison et al., 2012), and Neoglacial advances during the century have occurred in the Colonia valley (Tanaka, 1980; mid to late Holocene (summarized by Aniya, 2013). How- Friesen et al., 2015). GLOFs result from the sudden and ever, the history of NPI advance and retreat between LGM catastrophic drainage of supraglacial or proglacial lakes deglaciation and the late-1800s maximum generally is poorly and present a significant hazard to human populations and known (Glasser et al., 2004; Masiokas et al., 2009; Aniya, infrastructure (Richardson and Reynolds, 2000). Thus, under- 2013). This lack of knowledge limits studies which compare standing the history and mechanisms of the GLOFs in the either different parts of the NPI and its neighboring glaciers Colonia valley has both local and global implications. (e.g. Douglass et al., 2005) or the NPI with the better studied A better resolved chronology of Colonia Glacier advance and Southern Patagonia Icefield (SPI) (e.g. Strelin et al., 2014). retreat is essential to future studies of Colonia valley GLOFs. More generally, this void limits our understanding of Southern Studies in the Colonia valley were undertaken to identify glacial landforms and deposits and to collect data and Correspondence to: D. A. Nimick, as above. samples suitable for improved constraint on the post-LGM E-mail: [email protected] glacial history of the NPI. Field studies focused on moraines

Figure 1. Satellite image showing Northern Patagonia Iceﬁeld, primary outlet glaciers, location of the Colonia (Fig. 2) and Cachet (Fig. 3) valleys, and cosmogenic 10Be sampling sites (triangles) and site names from Glasser et al. (2012). NPI outline and mask are from the Global Land Ice Measurements from Space (GLIMS) glacier database (Davies, 2012). Base is from ESRI online World Imagery map ser- vice (www.arcgis.com/home/ item.html?id=10df2279f9684e4a 9f6a7f08febac2a9, accessed 16 October 2014) and is a compila- tion of satellite images taken during 1999–2011 by various sources.

in the Colonia valley proper (Fig. 2) and deposits and terminus (elevation of ca. 200 m) to the base of an icefall landforms in the tributary Cachet valley containing Lago (elevation of ca. 950 m), where this outlet glacier flows from Cachet Dos (Fig. 3), a lake currently dammed by the Colonia the NPI. Glacier. The Colonia Glacier today and in the past created ice- dammed lakes in two valleys tributary to the Colonia valley. Description of study area Both lakes have been intermittent through time depending on the position of the Colonia Glacier and its effectiveness as a The Colonia valley extends east and north-east from the NPI dam. GLOFs are (or were) a feature of both ice-dammed lakes to the Rıó Baker (Fig. 1). The eastern 19-km reach of the (Tanaka, 1980; Dussaillant et al., 2010). One of these ice- valley is drained by the Rıó de la Colonia (henceforth dammed lakes is the current Lago Cachet Dos in the Cachet abbreviated to Rıó Colonia), a braided glacial outwash river valley (Fig. 2). The second lake formed in the Arco valley on with a wide (3 km), largely unvegetated floodplain com- the south side of the Colonia valley (Fig. 5G) when the posed of fluvio-glacial sediment. The center reach of the Colonia Glacier abutted the north flank of Cerro Colonia. valley contains Lago Colonia, an 8-km-long moraine- This paleo Lago Arco existed during much of the 20th century dammed lake (Fig. 4A). The 5-km reach upstream of the lake and was larger than the present-day moraine-dammed Lago contains a sparsely vegetated outwash plain with the eroded Arco shown in Fig. 2 (Tanaka, 1980). GLOFs from paleo Lago remains of moraines (Fig. 4B) formed during the past ca. Arco occurred from before 1930 to 1968 (Tanaka, 1980), 150 years (Harrison and Winchester, 2000) and a proglacial while GLOFs from Lago Cachet Dos started in 2008 (Dussail- lake at the terminus of the Colonia Glacier (Fig. 5G). lant et al., 2010). Our field studies included the Cachet valley The Colonia Glacier extends north-west 18 km from its because determining previous fluctuations in the size and

Figure 2. Satellite image of Col- onia valley showing sampling sites and glacial landforms and deposits. Image produced from Landsat8 data collected on 18 January 2014. Topographic con- tour lines were derived from ASTER Global Digital Elevation Model (GDEM) v2. Elevations are referenced to the 1984 World Geodetic System (WGS84)/1996 Earth Gravitational Model (EGM96) geoid. Lacustrine trimline and 2007 Lago Cachet Dos boundary are from Friesen et al. (2015). ARCO, CLARO and LCM are Cerro Colonia lateral moraine, Rı´o Claro lateral moraine and Lago Colonia terminal moraine, respectively. Locations of sampled boulders are within the circle marking the location of each cosmogenic sampling site.

extent of Lago Cachet Dos provides one way to constrain the to be 11.7 cm a 1 and 26 a, respectively, based on previous chronology of Colonia Glacier advance and retreat. work in the Colonia valley (Winchester and Harrison, 2000). Lichenometric ages (Table 1) were determined at six sites Methods near a cored live tree. The longest diameter of 3–5 of the largest individual lichens (Placopsis perrugosa) on boulders at Field studies were conducted during austral summers 2011/12 each site were measured (Fig. 5E). A lichen growth rate of and 2012/13. Sample sites were located using a hand-held 4.7 mm a 1 (which incorporates the colonization period) was GPS with stated accuracy of <15 m using Universal Transverse assumed based on previous work in the Colonia valley Mercator projection, zone18S World Geodetic System of (Winchester and Harrison, 2000). The mean age for the three 1984 (WGS84). Dendrochronology and lichenometry ages are largest lichens at each live-tree site was used for the site. reported as calendar ages. Terrestrial cosmogenic nuclide 10Be surface-exposure ages (Table 2) were determined for (10Be) and optically stimulated luminescence (OSL) ages are samples collected from the top of upward-facing surfaces of reported as calendar years before publication date. Radiocar- boulders (with a b-axis >1 m where possible) on lightly bon ages are reported as calendar-calibrated years before vegetated moraine crests using hammer and chisel (Fig. 4C) present (BP, with present ¼ 1950) calculated from the conven- according to techniques from Gosse and Phillips (2001). tional radiocarbon age, the SHCAL13 database (Hogg et al., Some boulders had a thin layer of moss or lichen, which was 2013), and the 1-sigma error band. removed before sampling. Topographic shielding was esti- Dendrochronological ages (Table 1) were determined from mated from skyline measurements made with an Abney level. cores collected from live trees using an increment borer. Physical preparation, quartz puriﬁcation, dissolution and Cores were mounted in the laboratory, and tree rings were conversion into beryllium oxide, and 10Be analyses were counted using a stereoscopic microscope. Missing rings for performed by the Purdue Rare Isotope Measurement cores not containing the tree center were estimated using the Laboratory (West Lafayette, IN, USA). All 10Be/9Be ratios methodology of Duncan (1989). The growth rate for each tree were measured against the revised ICN standard of for the section below coring height and ecesis were assumed Nishiizumi et al. (2007), which assumes a half-life of

Figure 3. Satellite image of Cachet valley showing trimlines, deltaic deposits and sampling sites. Ages shown in parentheses are from either dendrochronology or dendrochronology/lichenometry (Table 1). Trimlines and 2007 Lago Cachet Dos boundary are from Friesen et al. (2015). Elevation of lacustrine trimline is ca. 500 m. Image produced from Digital- Globe WorldView-2 data collected on 13 Febru- ary 2014, 12 days after a GLOF emptied Lago Cachet Dos.

1.36 Ma. The 10Be/9Be ratio (2.84 10 15 0.57 10 15)of corrections for erosion rate or snow shielding (Gosse and the processing blank prepared with the samples was sub- Phillips, 2001), and these assumptions should not affect our tracted from the 10Be/9Be ratios of the samples. 10Be exposure conclusions. Similarly, use of alternative scaling schemes ages were calculated with the CRONUS-Earth calculator (Balco et al., 2008) resulted in age differences of <3% and (Balco et al., 2008) using a quartz density of 2.73 gcm 3, therefore would not affect our conclusions. To facilitate topographic shielding listed in Table 2, the Dunai time- comparisons, we recalculated the ages reported by Glasser dependent scaling scheme and production rates from Lago et al. (2012) for nearby sites (Fig. 1) using the same scaling Argentino in Patagonia (Kaplan et al., 2011). We applied no scheme, production rates and erosion rate listed above.

Table 1. Ages for live trees and lichens sampled on the east side of Lago Cachet Dos in October 2011. The age of individual trees (Nothofagus sp.) and the mean age of the three largest lichens (Placopsis perrugosa) at each site are reported.

Age (AD) Elevation Tree Sample number Latitude (˚S) Longitude (˚W) (m) diameter (cm) Tree species Tree Lichen

Sites below lacustrine trimline Ltree1 47.12101 73.28293 497 coigue€ † 1945 Ltree 2 47.14917 73.25912 421 30 coigue€ 1957 Ltree 3 47.14896 73.25845 463 29 coigue€ 1948 Ltree 4 47.14861 73.25761 492 29 coigue€ 1950 Ltree 6 47.17070 73.25750 432 15 coigue€ 1964 1965 Ltree 7 47.17048 73.25708 453 27 coigue€ 1963 1957 Ltree 8 47.17049 73.25687 459 25 coigue€ 1957 Ltree 10 47.17785 73.25525 440 17 lenga‡ 1955 1960 Ltree 11 47.17679 73.25439 478 14 lenga 1948 1963 Ltree 13 47.18653 73.25117 452 18 coigue€ 1959 1958 Ltree 14 47.18657 73.24949 479 18 nirre~ § 1953 Ltree 16 47.19241 73.24306 486 15 nirre~ 1947 Ltree 17 47.19448 73.24134 479 21 coigue€ 1964 Sites above lacustrine trimline Ltree 5 47.14851 73.25735 493 49 lenga 1905 Ltree 9 47.17092 73.25612 507 34 lenga 1902 Ltree 12 47.17630 73.25414 507 26 lenga 1864 Ltree 15 47.18772 73.24834 502 25 coigue€ 1921 1915

No data. †Nothofagus betuloides. ‡Nothofagus pumilio. §Nothofagus antarctica.

Burial ages based on optical dating (Table 3) were diameters of ca. 1 m and are composed of fine- to coarse- determined for sediment samples collected in 5-cm-diameter grained granite or gneiss (Fig. 5H). by 15-cm-long PVC core tubes inserted horizontally into shaded and freshly excavated vertical surfaces. Quartz and Lago Colonia terminal moraine and outwash terraces potassium feldspar grains (180–250 mm) were analysed by single aliquot regeneration (Murray and Wintle, 2000, 2003) The Lago Colonia terminal moraine that dams Lago Colonia using continuous-wave OSL and continuous-wave infrared (Figs 2 and 4A) was first identified by Tanaka (1980), who stimulated luminescence (IRSL), respectively. Luminescence named it Colonia Moraine No. 1 and estimated it to be data were subject to community standard quality-control tests 2.8 km long, 1.5 km wide and as much as 85 m in height including the recycling-ratio and dose-recovery tests (Rhodes, above Lago Colonia. The moraine crest ranges in elevation 2011). Additional information on OSL dating is given in between ca. 190 and 210 m. Numerous granitic boulders supplementary Appendix S1. 2–5 m in length litter the moraine surface (Fig. 4C). Based on Radiocarbon ages (Table 4) were determined for samples of observation of the expansive north-facing slope cut through outer tree rings collected using a handsaw from eight in situ the moraine by the Rıó Colonia (Fig. 4E), the moraine is dead trees exposed on the Cachet valley floor during post- underlain by massive diamicton. Several outwash terraces, GLOF periods. In addition, one sample was collected from the which are at successively lower elevations and underlain center of one of the trees and another from a paleo-soil primarily by coarse-grained gravel and sand, extend down- excavated beneath an in situ tree. Radiocarbon analyses were stream from the moraine (Figs 2 and 4E). OSL samples were performed by Beta Analytical (Miami, FL, USA) using gas collected from a loess deposit of silt and fine-to-coarse sand proportional counting for tree-ring samples and accelerator near the top of the moraine (Fig. 4D) and from a medium mass spectrometry for the soil sample. Samples were pre-treated sand lens near the top of the uppermost terrace (Fig. 4F). using sequential acid/alkali/acid washes. Calendar-calibrated ages were calculated using OxCal 4.2.4 software (Bronk ´ Ramsey, 2009) and SHCAL13 database (Hogg et al., 2013). Rıo Claro lateral moraine The lateral moraine at the mouth of the Rıó Claro valley Results (Figs 2 and 4G) was first identified by Tanaka (1980), who named it Colonia Moraine No. 2. The moraine is ca. 200 m Glacial landforms and deposits high, and its crest, which is more rounded than the crest of the Lago Colonia terminal moraine, ranges in elevation Cerro Colonia lateral moraine between ca. 350 and 380 m. Semi-rounded granitic boulders A lateral moraine on the northern flank of Cerro Colonia (Figs 2 on the moraine crest are as large as 2 m in diameter (Fig. 4H). and 5G) probably records the confluence of large glaciers descending the Arco and Colonia valleys. The moraine is ca. Cachet valley 300 m long, 40 m wide and 10 m high. The rounded moraine crest slopes down valley and ranges in elevation between ca. The Cachet valley is a hanging valley on the Colonia valley’s 910 and 930 m, far above the modern Colonia Glacier terminus north-east side, and its topographic configuration has allowed at ca. 200 m. Sparse rounded boulders on or near the crest have preservation of dateable materials that record Colonia Glacier

Figure 4. Photographs of Colonia valley. (A) View from Rıó Claro lateral moraine looking north-west up the Colonia valley. Rıó Colonia cuts through Lago Colonia terminal moraine and flows east towards right side of photograph. Rıó Claro is in foreground. (B) View looking south-east down the Colonia valley on 9 March 2013. Rıó Colonia drains from proglacial lake (on right side of photograph) and crosses outwash plain before entering Lago Colonia. Remnants of late-1800s and younger Colonia Glacier moraines, all eroded by numerous GLOFs, are visible in center and right side of photograph. (C) Collection of sample LCM8 for 10Be dating from boulder on crest of Lago Colonia terminal moraine. (D) Preparation for collection of sample OSL5 for OSL dating from loess deposit near top of Lago Colonia terminal moraine. (E) View from near crest of Lago Colonia terminal moraine looking east down the Rıó Colonia. (F) Sand lens within glacial outwash and collection site for sample OSL6. (G) View looking south-west across Rıó Colonia towards Rıó Claro lateral moraine. (H) Boulder located on crest of Rıó Claro lateral moraine and sampled for 10Be dating (CLARO5). advances and retreats. A lower outlet at the south-east corner Glacier to the modern boundary of Lago Cachet Uno. of the lake (Fig. 3) limits the lake’s maximum level to an Downstream and near the south-east corner of Lago Cachet elevation of ca. 420 m. A trimline at an elevation of ca. Dos, this lacustrine trimline extends to an abandoned upper 500 m on both sides of the Cachet valley (Figs 3 and 5C) is outlet channel (ca. 500 m) that controlled the former 500-m demarcated by a dense and mature forest above the trimline level of Lago Cachet Dos. Near the south-west end of the and an immature and openly spaced forest of smaller lake, the lacustrine trimline grades into a glacial trimline that diameter trees below the trimline (Friesen et al., 2015). The extends to the west up the Colonia valley (Figs 2 and 3). In lateral extent and horizontal nature of this trimline indicate the upper Cachet valley, the lacustrine trimline grades into that it was formed during a high stand of Lago Cachet Dos another glacial trimline (Fig. 3), which rises up-valley on both and that, at that time, the lake extended from the Colonia sides of Lago Cachet Uno (Friesen et al., 2015). Based on

Figure 5. Photographs of Cachet and Colonia valleys. Photographs in A–D and F were taken ca. 2 weeks after GLOF emptied Lago Cachet Dos on 26 January 2012. (A) View of west side of the Cachet valley showing deltaic sand deposits and 500-m lacustrine trimline. (B) Foreset beds of deltaic deposits and sampling site for OSL1. (C) View of upper Cachet valley. Trees in middle and foreground of photograph occupied a forested valley floor before 245 13 cal a BP, when the Colonia Glacier dammed the Cachet valley and formed Lago Cachet Dos. Before onset of GLOFs from Lago Cachet Dos in 2008, the land surface across the valley was at an elevation of the light brown hill on the right side of the photograph. The nine GLOFs between April 2008 and January 2012 eroded the valley-fill deposits and exposed the former forested valley floor. The 500-m lacustrine trimline is visible on both sides of the valley. Cachet Glacier is at the far end of the valley. (D) Group of ancient trees exposed on Lago Cachet Dos lake bed. Radiocarbon sampling sites are indicated. (E) Measuring diameter of a lichen near the 500-m lacustrine trimline. (F) Paleosoil located beneath the tree shown in D and sampled for radiocarbon dating (Soil11). (G) View looking south-west across Colonia valley and into Arco valley on 9 March 2013. Terminus of Colonia Glacier (center of photograph) separates the two parts of the proglacial lake, which drains to the left across the outwash plain into Lago Colonia (off photograph). The glacial trimline slopes down valley to terminal moraine remnants that are poorly visible on the outwash plain; both indicate late-1800s maximum of Colonia Glacier (Harrison and Winchester, 2000). Abutment of Colonia Glacier against the lower flank of Cerro Colonia created historical ice-dammed Lago Arco from which GLOFs emanated during the 20th century (Tanaka, 1980). Cerro Colonia lateral moraine is indicated. (H) Boulder located on crest of Cerro Colonia lateral moraine and sampled for 10Be dating (ARCO3). age-dating of similar trimlines in and near the Arco valley Before the onset of GLOFs in 2008, the Cachet valley (Fig. 5G; Harrison and Winchester, 2000), these glacial between Lago Cachet Uno and the Colonia Glacier contained trimlines probably demarcate the maximum late-1800s a flat valley floor and the braid plain of the Rıó Cachet over extent and thickness of the Colonia and Cachet Glaciers, its upstream half while Lago Cachet Dos, at its 420-m level, respectively. filled the downstream half (Friesen et al., 2015). Large-scale

Table 2. 10 Be surface-exposure ages calculated using the CRONUS-Earth webcalculator (Balco et al., 2008) for boulders sampled in March 2013.

Sample Quartz 10 Be 10Be Internal External § Sample Elevation thickness Topo-graphic sample carrier 10Be/9Be 10 Be (105 exposure uncertainty uncertainty¶ no. Latitude (˚S) Longitude (˚W) (m) (cm) shielding mass (g) (mg) (10 15 ) atoms g 1 ) age†‡ (a) (a) (a)

Lago Colonia terminal moraine LCM5 47.34680 73.12182 189 1 0.9852 134.097 0.26255 187.49 4.90 0.242 5130 140 220 LCM6 47.34743 73.12151 212 1 0.9824 37.797 0.26319 50.81 3.10 0.223 4650 310 340

LCM7 47.34809 73.12068 206 1 0.9813 124.976 0.26607 170.20 5.62 0.238 4990 170 240 SCIENCE QUATERNARY OF JOURNAL LCM8 47.34545 73.11213 194 1 0.9911 42.799 0.26618 60.93 3.67 0.241 5060 320 370 4960 210 Rı´o Claro lateral moraine CLARO1 47.36277 73.11806 368 1 0.9783 35.896 0.26650 126.00 4.12 0.611 11 100 380 520 CLARO2 47.36309 73.11732 375 1 0.9886 20.732 0.26276 71.61 2.57 0.582 10 300 400 530 CLARO3 47.36292 73.11726 370 2 0.9893 45.080 0.26468 164.42 4.69 0.634 11 400 340 510 CLARO5 47.36301 73.11698 349 1 0.9815 33.586 0.26736 116.16 5.30 0.603 11 100 520 640 11 000 470 Cerro Colonia lateral moraine ARCO1 47.28038 73.21937 926 1.5 0.9922 37.479 0.26511 241.88 6.62 1.13 12 400 350 540 ARCO3 47.27999 73.21903 922 0.8 0.9723 30.175 0.26490 220.09 6.39 1.27 14 100 430 630 ARCO4 47.27951 73.21852 914 2 0.9922 38.888 0.26073 268.16 8.79 1.19 13 200 450 620 13 200 950

10 Be isotope ratios normalized to 10 Be standards prepared by Nishiizumi et al. (2007). †A blank value of 10 Be/9Be ¼ 2.84 10 15 0.57 10 15 used to correct for background. ‡Using 0 mm ka 1 steady-state erosion, time-dependent scaling scheme (Dunai, 2001) and Kaplan et al. (2011) production rate in the CRONUS-Earth calculator (Wrapper script 2.2; Main calculator 2.1; constants 2.2.1; muons 1.1). The mean one standard deviation of ages for all samples is shown for each site. §One sigma analytical uncertainty. ¶One sigma analytical uncertainty plus the uncertainty of the production rate. .Qaenr c.(2016) Sci. Quaternary J. GLACIAL EVENTS IN THE NORTHERN PATAGONIA ICEFIELD

Table 3. Single aliquot regeneration quartz OSL and potassium feldspar IRSL data and ages for samples collected in March 2012.

Sample number OSL1 OSL5 OSL6

Sample description Deltaic sand from Lago Loess from near top of Lago Fluvial sand from near top of highest outwash terrace Cachet Dos lakebed Colonia terminal moraine downstream of Lago Colonia terminal moraine Latitude (oS) 47.15723 47.34314 47.34218 Longitude (oW) 73.25925 73.10860 73.10301 Elevation (masl) 423 187 127 Water content (%) 3 (15) 4 (19) 7 (27) † K (%) 3.33 0.07 2.75 0.06 2.28 0.05 † U (ppm) 1.21 0.16 2.58 0.28 1.88 0.28 † Th (ppm) 6.54 0.37 12.3 0.61 11.2 0.40 ‡ Cosmic dose (Gy/ka) 0.18 0.01 0.17 0.01 0.18 0.01 Total dose rate (Gy/ka) 3.97 0.11 5.74 0.19 4.56 0.13 †† ‡‡ ‡‡ Equivalent dose (Gy) 11.7 0.75 27.0 1.1 12.7 1.5 § †† ‡‡ ‡‡ n 9 (37) 12 (46) 10 (35) ¶ †† ‡‡ ‡‡ Scatter (%) 42 92 122 †† ‡‡ ‡‡ Age (a) 2,950 210 4,700 230 2,790 340

Field moisture, with figures in parentheses indicating the complete sample saturation percentage. Dose rate calculated using 50% of the saturated moisture [i.e. 3 (15) ¼ 15 0.50 ¼ 7.5]. † Analyses obtained using high-purity germanium gamma spectrometry. Errors obtained with calibration standards. ‡ Cosmic doses and attenuation with depth were calculated using the methods of Prescott and Hutton (1994). § Number of replicated equivalent dose (DE) estimates usedto calculate the overall DE. Figures in parentheses indicate total number of measurements used for the minimum age model of RadialPlotter and a sigma-b value of 0.2 (Vermeesch, 2014; Galbraith, 2010). ¶ Obtained from RadialPlotter (Vermeesch, 2014). Samples with values >35% are considered to be poorly bleached. Dose rate and age for 180–250 mm grains using single aliquot regeneration (Murray and Wintle, 2000, 2003). Exponential fit used on equivalent dose; errors to one sigma. ††Equivalent dose measurements obtained using continuous wave OSL (Murray and Wintle, 2000) on quartz grains. ‡‡ Equivalent dose measurements obtained using continuous-wave on potassium feldspar grains as post-IR IRSL (Kars et al., 2012). erosion of the Cachet valley floor during and after each of the moraine were grouped fairly closely with no apparent out- 15 GLOFs that occurred in 2008–2014 removed a substantial liers. Ages for the four boulders from the Lago Colonia volume of sediment from the valley floor (Friesen et al., terminal moraine overlap within 1-sigma uncertainties and 2015). This erosion exposed the stratigraphy of the valley fill ranged from 4.65 0.34 to 5.13 0.22 ka. The four ages for (e.g. Fig. 5A) and unearthed hundreds of in situ, upright trees the Rıó Claro lateral moraine were grouped almost as closely (Fig. 5C, D) that presumably grew on the valley floor during and ranged from 10.3 0.53 to 11.4 0.51 ka. For the Cerro periods when the Colonia Glacier was not large enough to Colonia lateral moraine, the three ages were within 2-sigma dam the Cachet valley and create a Lago Cachet Dos. Trees uncertainties and ranged from 12.4 0.54 to 14.1 0.63 ka. in the mid portion of the valley tend to be short (<2 m) and Overall, the mean age and standard deviation for each site show signs of abrasion (Fig. 5D), while trees in the upper half were 4.96 0.21 ka for the Lago Colonia terminal moraine, of the valley are taller (8 m) and much less abraded 11.0 0.47 ka for the Rıó Claro lateral moraine and (Fig. 5C). A paleo-soil 14C sample excavated directly beneath 13.2 0.95 ka for the Cerro Colonia lateral moraine. an in situ tree (Fig. 5D) came from a 5-cm-thick organic-rich (‘A’ horizon) layer located below a 10-cm-thick brown clayey OSL burial ages coarse sand and above a >20-cm-thick medium brown, The burial age for the deltaic sand sample (OSL1) from the pebbly, fine-to-coarse sand (Fig. 5F). Cachet valley (2.95 0.21 ka; Table 3) suggests an earlier The valley fill in the Cachet valley is a combination of episode of delta formation in a paleo Lago Cachet Dos. IRSL fluvial deposits consisting of cross-bedded, poorly to moder- ages were 4.70 0.23 ka for the loess sample (OSL5) from ately sorted silt to sandy gravel and cobbles, lakebed deposits the Lago Colonia terminal moraine and 2.79 0.34 ka for the consisting of horizontally bedded gray clayey silts, and fluvial sample (OSL6) from the outwash plain. deltaic lake deposits. Much of this valley fill probably is outwash sediment that first came from the Cachet Glacier Radiocarbon ages from Lago Cachet Dos lake bed itself and then from streams that eroded the moraine that now dams Lago Cachet Uno. This drainage fed an extensive sandy Ages (Table 4) for the paleo-soil (995 38 cal a BP; sample delta, including fluvial topset beds of the delta plain that Soil11) and outer rings from Tree 18 and Tree 11 (830 50 prograded into Lago Cachet Dos. These deltaic deposits and 790 47 cal a BP, respectively) indicate that the Cachet (Fig. 5A, B) occur most prominently near the northern end of valley had terrestrial vegetation and no lake over a multi- the 2007 Lago Cachet Dos (Fig. 3) and consist of thinly century period ca. 0.85–1.1 ka ago. Potential causes for the bedded and steeply dipping delta foreset strata composed of death for these two trees include inundation by lake water or well-sorted, fine-to-coarse sand. Samples were collected at burial by fluvial or colluvial sediment. If a paleo Lago Cachet three locations for OSL dating. Dos had formed and killed the trees by inundation, the lake had disappeared by 410 55 cal a BP, the age of sample Ages Tree 10B collected from the center of Tree 10. Outer tree-ring samples from six in situ trees provided 10Be surface-exposure ages for moraines conventional radiocarbon ages ranging from 90 to 210 14Ca 10Be ages and associated uncertainties for individual boulders BP (Table 4) and, due to the non-linearity of the radiocarbon are listed in Table 2. Ages for the sampled boulders for each calibration curve, a wide but largely overlapping range of

Table 4. Radiocarbon ages for wood and soil samples collected in October 2011 or February 2012. Data for samples Tree 10 to Tree 1 are shown in downstream-to-upstream order in the Cachet valley. Tree samples were collected from outer rings except sample Tree 10B, which was collected from the center of Tree 10.

Sample no. Lab. no. Latitude (˚S) Longitude (˚W) Conventional radiocarbon 2-sigma calendar Mean age†‡ age (14C a BP) calibrated age† (cal a BP)

Soil11 Beta-323914 47.15896 73.26090 1130 30 BP AD 890–1020 995 38 Tree11 Beta-323917 47.15896 73.26090 920 30 BP AD 1045–1090 790 47 AD 1130–1225 Tree18 Beta-388185 47.15860 73.26083 950 30 BP AD 1040–1210 830 50 Tree10B Beta-323916 47.16277 73.25856 400 30 BP AD 1450–1630 410 55 Tree10 Beta-323915 47.16277 73.25856 120 30 BP AD 1695–1725 240 12§ AD 1805–1950 Tree15 Beta-323920 47.15463 73.26070 90 30 BP AD 1695–1725 240 10§ AD 1805–1870 AD 1875–1950 Tree14 Beta-323919 47.15031 73.26047 190 30 BP AD 1665–1815 –¶ AD 1830–1895 AD 1920–1950 Tree13 Beta-323918 47.14608 73.26327 170 30 BP AD 1670–1745 245 19§ AD 1760–1780 AD 1795–1950 Tree6 Beta-309533 47.13951 73.26810 90 30 BP AD 1695–1725 240 10§ AD 1805–1870 AD 1875–1950 Tree1 Beta-309531 47.13400 73.27161 210 30 BP AD 1650–1710 270 13§ AD 1720–1815 AD 1835–1850 AD 1855–1880 AD 1925–1950

Radiocarbon years before present with ‘present’ ¼ 1950. The conventional radiocarbon age represents the measured radiocarbon age corrected for isotopic fractionation calculated using the measured 13C/12C ratio. †Calculated using OxCal 4.2.4 software (Bronk Ramsey, 2009) and SHCAL13 database (Hogg et al., 2013) from the conventional radiocarbon age. ‡Arithmetic mean and 1-sigma error in calendar-calibrated years before 1950. §Mean age calculated for only the earliest calendar-calibrated age range. ¶Mean age not calculated. calibrated ages (AD 1650–1950, or 0–300 cal a BP). Owing based on the 1: 50 000 Cordon Soler quadrangle (published to this age overlap and the large spatial spread of the sampled in 1982 by the Instituto Geografico Militar de Chile and trees along much of the longitudinal axis of the Cachet valley based on 1975 aerial photographs). Based on our dendro- (Fig. 3), these trees were probably killed nearly simulta- chronological and lichenometric ages, the lake level dropped neously by inundation when Lago Cachet Dos last formed, to its current 420-m position in ca. 1960. Tree-ring cores probably as the Colonia Glacier thickened en route to its late- from 13 live trees located below the lacustrine trimline 1800s maximum. The possible age of these tress can be provided ages between 1945 and 1964, with a mean of 1955 narrowed to the earliest part of the 1650–1950 period by (Table 1). Ages based on the mean of the three largest lichens assuming that Lago Cachet Dos was probably created at the five live-tree sites where lichens were measured ranged >100 years before the late-1800s maximum. This assumption from 1957 to 1965, with a mean of 1961 (Table 1). is reasonable considering that the lake has continued to exist > for 100 years after the late-1800s maximum even in the Discussion face of substantial post-late-1800s retreat of the Colonia Glacier (Harrison and Winchester, 2000; Davies and Glasser, Chronology of Colonia Glacier advance and retreat 2012). Five of the six trees have a distinct calibrated age During the LGM, the Colonia Glacier filled the Colonia range before 1750 (100 years before the late-1800s maxi- valley, coalesced with other NPI outlet glaciers, flowed mum); the mean of these ranges (245 13 cal a BP) is eastward and formed moraine systems in Argentina (Kaplan considered the most plausible age for the formation of Lago et al., 2004; Singer et al., 2004). The LGM occurred at Cachet Dos. 27–25 ka with subsequent advances at 23–22, 20–18 and ca. 18–17 ka; rapid deglaciation from the LGM moraines began Dendrochronology and lichenometry ages for Lago Cachet after 18–17 ka (Hein et al., 2010; Boex et al., 2013). During Dos trimline deglaciation but while the Rıó Baker’s path to the Pacific The age of the lacustrine trimline that encircles much of Lago Ocean was still dammed by the retreating outlet glaciers, Cachet Dos at an elevation of ca. 500 m was bracketed from paleo lakes formed with surface elevations of ca. 489–512 m its appearance in aerial photographs and estimated using and later at ca. 375–397 m near the Nef and Colonia valleys; dendrochronology and lichenometry. The 500-m lake was at the Rıó Baker finally drained to the Pacific Ocean at ca. this trimline elevation in 1945, based on a map compiled by 12.8 ka (Turner et al., 2005). Lliboutry (1998, fig. 27) from aerial photographs. By 1975, The earliest evidence for a post-LGM ice position of the Lago Cachet Dos had lowered to the 420-m level (Fig. 2) Colonia Glacier is the Cerro Colonia lateral moraine high on

Copyright # 2016 John Wiley & Sons, Ltd. J. Quaternary Sci. (2016) GLACIAL EVENTS IN THE NORTHERN PATAGONIA ICEFIELD the north flank of this mountain. Dated to 13.2 0.95 ka presumably because retreat of the Colonia Glacier away from (Table 2), this moraine records the most extensive Colonia the northern flank of Cerro Colonia removed the dam. Glacier position that has been found within the Colonia By ca. 1960, retreat of the Colonia Glacier from the Cachet valley proper and the position held just before the initiation valley uncovered the lower outlet channel for Lago Cachet of westward Rıó Baker drainage at ca. 12.8 ka (Turner et al., Dos at ca. 420 m, and the lake abandoned its previous 500-m 2005). The Rıó Claro lateral moraine also records a distant level. Between 1996 and 2013, the Colonia Glacier terminus downvalley advance or perhaps stabilization during post- retreated another ca. 1.5 km, and the individual proglacial LGM retreat of the Colonia Glacier at 11.0 0.47 ka. No lakes in the Arco and Colonia valleys (Fig. 5G) joined to form terminal moraine associated with either the Cerro Colonia or a single larger proglacial lake in 2014 (Fig. 2). GLOFs from the Rıó Claro lateral moraines has been identified, but the Lago Cachet Dos started in 2008 probably due to thinning moraine mounds at Lago Esmeralda (site LE, Fig. 1) dated by and weakening of the Colonia Glacier, thus allowing the lake 10Be at 12.0 0.75 ka (Glasser et al., 2012) may indicate an to drain catastrophically via meltwater channel(s) within or approximately contemporaneous downstream limit. beneath the 8-km terminal reach of the glacier (Dussaillant Although we found no evidence for early Holocene activity et al., 2010). for the Colonia Glacier, evidence for advance and retreat during the Neoglacial (Porter and Denton, 1967) is relatively Post-LGM glacial chronology for the NPI abundant. In the early Neoglacial, the Colonia Glacier advanced and created the terminal moraine at Lago Colonia Combining the Colonia record reported here with previous at 4.96 0.21 ka. The IRSL age (4.70 0.23 ka, sample OSL5, work on other NPI outlet glaciers (Fig. 6) provides a clearer Table 3) for the loess from the top of the Lago Colonia post-LGM glacial chronology for the NPI as a whole and terminal moraine is a minimum age for formation of this allows a better comparison with the more thoroughly studied moraine and is consistent with the 10Be age. SPI. However, as recently noted by Strelin et al. (2014) Information on more recent Colonia Glacier activity comes and Aniya (2013), who reviewed Neoglacial advances for the from the Cachet valley, which has a multi-millennia record of SPI and the combined icefields (Table 5), respectively, alternating periods of the valley either containing a lake attempts to find regional patterns in Holocene glacial during periods of an advanced and thickened Colonia Glacier chronology for the Patagonia Icefields can be elusive with or being forested during periods of stable fluvial drainage, existing data. As discussed in this section, the most regionally probably when the glacier was smaller than it is today. The consistent data for the NPI document advances at the oldest deltaic-sand sample (OSL1, Table 3) indicates a beginning of the Holocene and in the late-1880s (Fig. 6). The Colonia Glacier advance that created a paleo Lago Cachet questions of what happened before and between these two Dos at or before 2.95 0.21 ka. No terminal moraine periods and if advances in this intervening period were associated with this advance has been identified. However, synchronous have not yet been completely resolved. the fluvial sand from the upper outwash terrace of the Lago During the Late Pleistocene, the NPI remained close to Colonia terminal moraine (2.79 0.34 ka, sample OSL6, LGM positions until ca. 18 ka, when the extensive ice lobes Table 3) also dates to this period and suggests that the of the ice sheet quickly shrank and separated into the discrete Colonia Glacier may have readvanced as far down valley as outlet glaciers found today in valleys draining all sides of the this moraine. Sometime after 2.95 0.21 ka, but before icefield (Boex et al., 2013). Erratic boulders on the Rıó Bayo 995 38 cal a BP, the glacier retreated and the paleo Lago valley floor (Fig. 1) ca. 40 km downstream from the present Cachet Dos disappeared, allowing soil development (sample Exploradores Glacier indicate a minimum ice extent Soil11) on the valley floor. However, the lake may have been [13.8 0.9 ka; recalculated from Glasser et al. (2006) by re-dammed at 810 49 cal a BP (mean of ages for outer-ring Glasser et al. (2012)]. The earliest dated record of a maximum samples from Tree 18 and Tree 11, Table 4) assuming these ice position within any NPI valley is for the Cerro Colonia two trees were killed by inundation. If a paleo Lago Cachet lateral moraine (13.2 0.95 ka, Table 2) in the Colonia Dos did form at 810 49 cal a BP, it had disappeared by valley. 410 55 cal a BP based on the radiocarbon sample from the At the beginning of the Holocene (10 000 14C a BP or 11 center of Tree 10, and the valley floor was again forested. 360 cal a BP), outlet glaciers in four valleys (Fig. 6) extended At 245 13 cal a BP (Fig. 5C), thickening of the Colonia as much as 50 km eastward forming terminal moraines in the Glacier dammed the Cachet valley forming a lake, presum- Nef, Soler and Leones valleys (sites RC, LPB and MLV, ably with a water level of ca. 420 m controlled by the current respectively, in Fig. 1) and lateral moraines in the Colonia outlet channel for Lago Cachet Dos. Sometime later but and Nef valleys (sites NEF in Fig. 1 and CLARO in Fig. 2), all probably before the late-1800s maximum, continued advance dated by 10Be at 10.4–11.2 ka (Table 2; Glasser et al., 2012). of the Colonia Glacier into the Cachet valley sealed the lower Whether these moraines represent stabilization of the NPI outlet channel. This event allowed the lake level to rise to the during ongoing retreat from LGM positions or regional elevation of the upper outlet channel at ca. 500 m. This expansion of NPI outlet glaciers is not clear (Glasser et al., continued advancement of the Colonia Glacier reached a 2012), but overall this advance is one of the best documented maximum, recorded by glacial trimlines (Fig. 5G) and for the NPI. remnants of a terminal moraine (Fig. 4B) ca. 5 km down- Evidence for NPI advances during the first half of the stream from the current terminus, dated to 1850–1880 Holocene is scant. Harrison et al. (2012) dated advances at (Harrison and Winchester, 2000). 9.7–9.3 1.2 and 7.7 1.1 ka (Fig. 6) for the San Rafael Between the late-1880s maximum and 1996, the Colonia Glacier (Fig. 1), and Douglass et al. (2005) dated advances at Glacier terminus retreated ca. 1.5 km (Harrison and Winches- >10 and ca. 7 1 ka [recalculated by Strelin et al. (2014) ter, 2000; Fig. 2). Only small and isolated remnants of the using Kaplan et al. (2011) production rates] in the Rıó Aviles late-1800s terminal moraine and post-late-1800s recessional valley ca. 25 km east of the NPI. As noted by Aniya (2013), moraines remain downstream of the current Colonia Glacier more data are necessary to determine whether any of these terminus, probably because of erosion by numerous GLOFs advances was regionally synchronous. during the past century from the Arco and Cachet valleys. The onset of Neoglaciation for the NPI appears to be GLOFs from the Arco valley stopped occurring in 1968 indicated by terminal moraines of the San Rafael Glacier

advances dated to 1500–1100 and ca. 700 cal a BP (Strelin et al., 2014) and the Aniya (2013) age for Neoglacial IV (1450–750 cal a BP, Table 5). These advances of the NPI are recorded by moraines dated at 814–657 cal a BP for the Exploradores Glacier (Aniya et al., 2007), 1210 cal a BP (Aniya and Naruse, 1999) and 721–507 cal a BP (Glasser et al., 2002) for the Soler Glacier, and before 580 cal a BP for the Nef Glacier (Winchester et al., 2001). In addition, radiocarbon data indicate possible inundation of trees in the Cachet valley caused by an advancing Colonia Glacier at 810 49 cal a BP (Table 2). Lastly, sedimentological and geochemical analysis of fjord sediment indicates three ad- Figure 6. Advances of outlet glaciers draining the Northern vance/retreat cycles of the Gualas Glacier at 4180–850 cal a Patagonia Icefield. Patagonia Icefield Neoglacial advances (hatched BP (Bertrand et al., 2012). areas) are from Aniya (2013) and advances from Strelin et al. (2014) The best documented regional advance of NPI outlet for the Lago Argentino area on the eastern side of the Southern glaciers occurred at 350–50 cal a BP (Aniya, 2013; Strelin Patagonia Icefield (horizontal grey bars) are shown for comparison. Ages derived from 14C (triangles), 10Be (circles), OSL (diamonds), et al., 2014), a period commonly referred to as the Little Ice dendrochronology or lichenometry (squares), or sedimentological and Age. Although advances early in this period have been geochemical analysis of fjord sediment (dashed horizontal line). reported for several SPI outlet glaciers (Strelin et al., 2014), Colored symbols are for moraines. Open symbols are for other only our 245 13 cal a BP radiocarbon age indicating an indicators of ice position. One-sigma error band is shown by a solid horizontal line (which is within the size of symbols for 14C ages). advancing Colonia Glacier provides similar temporal evi- Plotted 14C ages were recalculated using OxCal 4.2.4 software (Bronk dence. Conversely, contemporaneous advances to late-1800s Ramsey, 2009) and SHCAL13 database (Hogg et al., 2013) from maximum positions are a common feature of almost all 14 10 original data reported in C a BP. Plotted Be ages were studied NPI outlet glaciers: seven shown in Fig. 6 and five recalculated from originally reported data using CRONUS-Earth others listed in Masiokas et al. (2009). After the late-1800s, calculator (Balco et al., 2008), production rates from Kaplan et al. (2011), and no erosion. Data references: San Rafael Glacier (Win- retreat of and volume loss from all NPI outlet glaciers has chester and Harrison, 1996; Harrison et al., 2012), Gualas Glacier been comparable (Rivera et al., 2007; Masiokas et al., 2009; (Harrison and Winchester, 1998; Bertrand et al., 2012), Exploradores Davies and Glasser, 2012). Glacier (Glasser et al., 2006; Aniya et al., 2007), Leones Glacier (Harrison et al., 2008; Glasser et al., 2012), Soler Glacier (Sweda, 1987; Aniya and Naruse, 1999; Glasser et al., 2002, 20122012), Nef Conclusion Glacier (Winchester et al., 2001; Glasser et al., 2012) and Colonia Glacier (Harrison and Winchester, 2000; this study). The post-LGM glacial history of the NPI has become better known over the past 30 years owing to the many field expeditions that have studied some, but not all, of the outlet dated at 5.7 0.6 ka (Harrison et al., 2012) and the Colonia glaciers draining the NPI. Our study adds to this growing Glacier dated at 4.96 0.21 ka (Table 2) and 4.70 0.23 ka body of information by providing ages covering ca. 13 ka for (Table 3). No other glacial features on either side of the NPI the Colonia valley, where glacial history before the late- have been dated to this period. Their timing coincides with 1800s maximum had not been well known. The glacial the Strelin et al. (2014) age for an SPI advance at 5000– record for the Colonia valley developed during our study is 6000 cal a BP and is similar to the Aniya (2013) age for the most complete post-LGM record for any of the NPI outlet Neoglacial I (5130–4430 cal a BP, Table 5). glaciers and is particularly important because the Colonia The record compiled to date for the main part of the Glacier is the largest outlet glacier draining the eastside NPI. Neoglacial (Fig. 6) does not indicate broad regional patterns Possible advances of the Colonia Glacier were recognized for NPI and vicinity. The oldest advances include the at 13.2 0.95, 11.0 0.47 and 4.96 0.21 ka based on 10Be terminal moraine in the Leones valley dated to ca. 3.3–2.4 ka ages for moraines, and 2.95 0.21 ka based on an OSL age by Harrison et al. (2008) and deltaic sediment in the for deposition of deltaic sediment in an ice-dammed lake in Cachet valley indicating a Colonia Glacier advance at ca. the tributary Cachet valley. In addition, minimum ages 2.95 0.21 ka (Table 3). These events broadly coincide with (810 49 and 245 13 cal a BP) were established for the advances dated to 2500–2000 cal a BP for the SPI (Strelin start of the advances leading to maximum positions during et al., 2014) and the Aniya (2013) age for Neoglacial III Neoglacial IV and V, respectively, based on radiocarbon (2770–1910 cal a BP, Table 5). Similarly, reported ages for dates for trees presumed killed by creation of the ice-dammed advances in a few eastside NPI valleys coincide with SPI lake in the Cachet valley. Overall, this study supports and provides additional definition of the developing history of post-LGM glacial events associated with the NPI. Table 5. General Neoglacial chronology for Patagonia Icefields (Aniya, 2013). Supporting Information Neoglacial advance Timespan Timespan (cal a BP) Additional supporting information may be found in the online version of this article. 14 1 4500–4000 C a BP 5130–4430 The following appendix is available within the Wiley Online 14 2 3600–3300 C a BP 3850–3490 Library. 3 2700–2000 14C a BP 2770–1910 4 1600–900 14C a BP 1450–750 5 16th–19th century 350–50 Appendix S1. Supplementary information on luminescence dating. Calculated using OxCal 4.2.4 software (Bronk Ramsey, 2009) and SHCAL13 database (Hogg et al., 2013) from the conventional Acknowledgments. This investigation was inspired by the skillful radiocarbon age with BP ¼ before 1950. mentoring of Stephen Porter and completed with the very able field

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