Quaternary Science Reviews 313 (2023) 108174 Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev Spatial analysis of paleoclimate variations based on proxy records in the south-central Andes (18 - 35 S) from 32 to 4 ka ctor Orellana a, b, d, *, Claudio Latorre b, c, d, **, Juan-Luis García a, d, Fabrice Lambert a, e He lica de Chile, Chile Instituto de Geografía, Pontificia Universidad Cato Instituto de Ecología & Biodiversidad (IEB), casilla 653, Santiago, Chile c lica de Chile, Chile Departamento de Ecología, Pontificia Universidad Cato d lica de Chile, Chile Centro UC Desierto de Atacama, Pontificia Universidad Cato e Center for Climate and Resilience Research, Chile a b a r t i c l e i n f o a b s t r a c t Article history: Received 8 August 2022 Received in revised form 22 May 2023 Accepted 4 June 2023 Available online xxx The long-term climate dynamics of the central Andes are part of an ongoing international research effort to reconstruct past climatic variations and sensitivity to different regional and global drivers during the last 50,000 years. The large number of diverse records, however, makes it difficult to compare results without an integrated spatial analysis that considers the nature of the record and whether they are integrating environmental conditions across a large basin (i.e., a lake record) or at a very local scale (such as a rodent midden). We compiled 92 records from the southern sector of the central Andes (SCA, 18 35 S). Recalibrated records were further compared by converting the original author's interpretation into a scale of relative moisture anomalies (compared to the present) that ranges from 2 (very dry) to very wet (þ2). Moisture anomaly maps were generated for intervals at 4, 6, 9.5, 14, 17, 21 and 32 ka BP (103 calibrated 14C years before present) using records within a 5% age uncertainty. Our compilations show a surprising degree of agreement in the extent and magnitude of past climate changes during late Pleistocene, but less spatial agreement during the Holocene. The TRACE21 transient climate model shows similar results, with better agreement during the Pleistocene compared to the Holocene. Our analyses not only reveal discrepancies between proxy record interpretations at sites from the same region but show which regions in the SCA require more study. © 2023 Elsevier Ltd. All rights reserved. Handling Editor: Dr Giovanni Zanchetta 1. Introduction The long-term climate dynamics of the South-Central Andes (or SCA, 18-35 S) is still poorly understood (Garreaud et al., 2010; Rech et al., 2010, 2019; Norton and Schlunegger., 2011; Rohrmann et al., 2016). This is due to at least two causes: 1) the lack of continuous time series that span the last Glacial- Interglacial transition and 2) the few records that do span this interval continuously are often at odds in terms of the extent and timing of dry versus wet phases (often even within the same basin, e.g., Baker et al., 2001; Fornari et al., 2001; Placzek et al., 2006, 2013). lica de * Corresponding author. Instituto de Geografía, Pontificia Universidad Cato Chile, Chile. ** Corresponding author. Departamento de Ecología, Pontificia Universidad lica de Chile, Santiago, Chile. Cato E-mail addresses: [email protected] (H. Orellana), [email protected] (C. Latorre). https://doi.org/10.1016/j.quascirev.2023.108174 0277-3791/© 2023 Elsevier Ltd. All rights reserved. Due to their latitudinal position spanning both tropical and extratropical rainfall belts, the SCA contain a large number of paleorecords used to reconstruct past environmental and climatic variability during the late Quaternary. For example, sedimentary and geomorphological records have provided evidence for lake highstands and periods of extended drought (Sylvestre et al., 1999; Grosjean et al., 1997a,b; Baker et al., 2001a; Grosjean et al., 2001; Moreno et al., 2007) and glacial advances (Zech et al., 2006; 2007; Smith et al., 2009; Aguilar, 2010; Ward et al., 2015). In contrast, paleoecological records from the Atacama Desert and semiarid central Chile have been used to infer changes in the elevation of vegetation belts as species descend or ascend the Andes driven by past wet and dry phases, respectively (Maldonado et al., 2005; 2005, 2006; Latorre et al., 2003; 2003, 2006; De Porras et al., 2017; Díaz et al., 2019). Multiproxy studies have also been used to infer paleoenvironments at archaeological sites (Gil et al., 2005; Yacobaccio and Morales, 2005; Navarro et al., 2010; Tchilinguirian et al., 2014; Grana et al., 2016). Many of these paleoclimate H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 2009). As with SC, precipitation in CC occurs during the winter months, however, mid-latitude storm fronts circulating entrenched in the Southern Westerly Winds (SWW) become increasingly frequent as the South Pacific Subtropical High (SPSH) weakens and migrates northwest (May to September) (Garreaud et al., 2003) (Fig. 2). To the east of the Andes, the NWA and Cuyo subregions (22 and 35 S) span along the eastern flank of the Andes. The NWA subregion lies above 2200 up to c. 6900 m.a.s.l., between 28 and 36 S. Average annual rainfall is 350 mm/year that drops to less than 250 mm/year below 2200 m.a.s.l. in the central plains of Argentina. The rainfall in this subregion results from tropical and subtropical moisture advected southwards from the Amazon and Chaco basins by the low-level northeast jet (NELLJ, 10 -20 S) that intensifies during the summer months associated with the formation of the Chaco Low and brings the moisture that feeds convective storms as far south as 35 S (Garreaud et al., 2003). In contrast, winter rains from the Pacific are restricted to the high Andes but are crucial in maintaining snow cover throughout the year (Masiokas et al., 2012). reconstructions are not without some controversy. For instance, the extent and timing of wet versus dry conditions during the Last Glacial Maximum (LGM) (Thompson et al., 1998; Baker et al., 2001a; Baker et al., 2001b; Fornari et al., 2001; Placzek et al., 2006) and the Middle Holocene (Northgrippian) (Betancourt et al., 2000; Grosjean et al., 2001; Quade et al., 2008; Grosjean et al., 2003). There are many issues with estimating past hydroclimate from records, spanning from potential geochronological problems (unquantified or unknown radiocarbon reservoir effects, e.g., Geyh et al., 1999), proxy interpretation, and integration of local versus regional signals (Grosjean et al., 2003). Few past studies have contrasted the different proxy records from the SCA for specific timeframes. Such an approach is needed to produce a more complete picture of past environmental conditions for any given period. Moreover, we still lack a thorough understanding of the geographic extent of specific paleoclimate events (e.g., the LGM or during the Last Termination). In this paper we reviewed 92 published paleoclimate records from the SCA with the goal of providing maps for specific time windows that span the last 32 ka BP (see Supplementary Materials). These records are diverse in terms of types (i.e., biological or geological), stratigraphic continuity (from continuous lake cores to discrete glacial deposits to rodent middens) and dating methods (radiocarbon, luminescence, cosmogenic-exposure dating, etc.). Instead of judging the quality or reviewing the interpretations of the published records, we compiled all of them into paleoclimate maps for specific time-windows that could then easily be contrasted with paleoclimate model outputs (we use the TRACE 21k transient model, Liu et al., 2009). We extracted a quantitative moisture index from each of the 92 records, which we then discuss in terms of the magnitude and direction of past climate change in the SCA. In this way, the different records can be contrasted with each other within the same time window, thus revealing any spatial gaps due to a lack of data and/or conflicting interpretations. 3. Methods We reviewed 92 paleoclimatic records from the SCA published since 2020 (see supplemantary information). Our review adds to and expands on a similar recent review (Tchilinguirian et al., 2014) that provided a regional synthesis of various proxy records dated to the Middle Holocene (the Northgrippian) for NWA and SCA. In our case, we increased the time scale to include all known terrestrial records since 32 ka BP restricted to those occurring from the subtropical latitudes to tropical latitudes (18 e35 S) and excluded other sites that are associated with the influence of the lowland east tropical in the Amazon basin (such as those from the Cordillera Oriental from Bolivia). The 92 records reviewed (numbered from 1 to 92, each site and corresponding number are in Supplementary Materials represent a diverse array of proxy records including alluvial stratigraphies, moraines, ice cores, saltpan and lake cores, plant macrofossils, paleowetland sediments, rodent middens, shoreline (paleolake) extent, paleodune sequences, pollen, paleosols and diatom records (Fig. 3). To enable comparisons across records, we converted the original author's paleoclimate interpretations into an ordinal moisture anomaly scale that spans from 2 (much drier than present) to þ2 (much wetter than present) with 0 corresponding to modern climate (or similar condition). For example, if an author states that their records are very wet relative to the present it is þ2, if it was only wetter than present then þ1, the same if the record shows more arid or arid (2; 1) and 0 if it is similar to present conditions. We also incorporated a measure that semi-quantifies into two overall categories the implicit spatial extent represented by each record in terms of their climate signal: a) the local scale or point-source signal (e.g., <25 km2 for a single rodent midden) and b) a basin-wide signal (>25 km2, e.g., a lake core from a large watershed, such as the Tagua Tagua basin, 35 S). This is graphically represented by a buffer of either 25 or 50 km, depending on whether the record represents a local or regional climatic signal. Once classified, records were then collated into a series of paleoclimate maps for seven different time windows at 4.0, 6.0, 9.5, 14, 17, 21 and 32 ka BP. These time frames were chosen because they represent available RCM simulations that have been developed by the Paleoclimate Modelling Intercomparison Project (PMIP) (Rehfeld and Brown, 2021). Time windows were further compiled into the geographic sub-regions described above. Each timewindow is a map with a snapshot of relative moisture conditions at a given moment including records that were dated to within a 5% 2. Physiography and present climate The SCA as a region lies between 18 and 35 S, which encompasses a total of eight distinct subregions within Bolivia (1 subregion), Chile (5 subregions) and Argentina (2 subregions). These are the Bolivian Altiplano, the Northern Atacama Desert, the Central Atacama Desert, the Southern Atacama Desert, Semiarid Chile, Central Chile, and Northwest Argentina and the Cuyo Region (Fig. 1). The physiography and present-day climate for each of the eight subregions are further detailed below. The Bolivian Altiplano (abbreviated BA), with an average elevation of 3800 m a.s.l., is located between the fold and thrust belt of the eastern Cordillera and the active volcanic arc of the western Cordillera (16 e23 S) (Rigsby et al., 2005; Jordan et al., 2014). For this study, we consider the southern Altiplano corresponding to the Salar de Uyuni (17 e23 S) basin where most SCA paleoclimatic records have been described. This subregion is characterized by a tropical influence and elevations that reach 5500 m a.s.l. (Tapia et al., 2019). In Chile, the region between 17 and 27 S known as the Atacama Desert is divided into three subregions: Northern Atacama (NA, 17 to 21 S), Central Atacama (CA, 21 to 24 S) and Southern Atacama (SA, 24 e27 S). At elevations higher than 3000 m a.s.l. these regions, together with the BA and Northwest Argentina (NWA) are characterized by dry and cold winters (June to August) and rainy summers (December to March) with overall rainfall decreasing from north to south. Farther south, the subregions between 27 32 S and 32 - 35 S are termed Semiarid Chile (SC) and Central Chile (CC), respectively. Precipitation in the SC is highly dependent on the Andean orography, and it varies from 25 mm/year along the coast to approximately 300 mm/year in the Andes (Falvey and Garreaud, 2 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 Fig. 1. Map of the south-central Andes showing the geographic extent of regions discussed. Coastal Range, Central Depression, Altiplano-Puna, Northern Atacama (NA), Central Atacama (CA), Southern Atacama (SA), Semiarid Chile (SC), Central Chile (CC), Northwest Argentina (NWA), and Cuyo subregions (CR). et al., 2013). We could not recalibrate cosmogenic ages as most authors did not include the necessary data in their original publications. Recalibrated 14C ages are expressed as ka BP whereas other ages (e.g., UeTh, OSL, etc.) are in ka only. All maps were drawn using ArcGIS 10.5 and the SRTM topographic base. For each site compiled into our database we discuss the evidence used by the authors in assigning our moisture anomaly category. In many cases, also included assigning rainfall seasonality (summer versus winter) suggested in publications (see Supplementary Materials). Comparisons to our time-windows were made against paleoclimate simulations that were provided by the TRaCE 21k transient simulation (Liu et al., 2009). This simulation uses a fully coupled model (National Center for Atmospheric Research Community Climate System Model version 3) that is forced by time-varying orbital parameters, greenhouse gases, time-varying ice-sheet extent and topography, and freshwater forcing to the oceans from the retreating ice sheets (Liu et al., 2009). range of that age (see Supplementary Materials). It is important to note that our maps represent a “consensus” view as they incorporate any record that falls within the defined time interval. If the same record has a date within the range of one of the temporal windows with a different climatic signal (wet or dry) then the signal closest to the target time interval was chosen. For example, if the same record shows “wet” at 21.2 ka BP and “dry” at 20.5 ka BP for the interval 21 ± 1.2 ka, the “accepted” (e.g., mapped) record is the one closest in age to the 21 ka BP date, in this case 21.2 ka BP. The qualitative nature of this analysis is based on the interpretation that each author makes of their records (we did not reinterpret records), that in some cases may not be very accurate of actual relative moisture conditions, but is nevertheless a good element to spatially compare records and to see differences with paleoclimatic models. Records that use radiocarbon chronologies were recalibrated with Calib7.0.4 (Reimer et al., 2013) and the SHCAL13 curve (Hogg 3 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 Fig. 2. Average annual precipitation over South America (Worldclim2 data, Fick and Hijmans, 2017). A) Distribution of average summer precipitation (DJF). B) Distribution of average winter precipitation (JJA). The SCA are also shown for reference (red rectangle). Major wind directions associated with extra-tropical rainfall (orange arrows) and average directions of tropical rainfall winds (black arrows) are also shown. Other major circulation features shown are the SPSH (South Pacific Subtropical High) and the NELLJ (North Easterly LowLevel Jet). del Chaco I [60] (25 S) also show the presence of taxa that today occur 700 m higher in elevation and their presence has been attributed to an increase in winter precipitation before 32 ka BP, although the ages are reported as >33.8 ka BP (Maldonado et al., 2005) and are thus infinite dates and were not considered here in our review. Increased dune formation at Llano Agua de los Burros [65] (27 S) in the SA between 41 and 28 ka BP suggests an increase in the source of fluvial sediments, as a result of increase rainfall in the Andes (Nash et al., 2018). Records from SC and CC show positive moisture anomalies at 32 ka BP. Exposure dates (10Be) on lateral moraine boulders indicative ~ a Rosa [78], a currently of extensive glaciation at Cordon Don unglaciated area with elevations over 4500 m. a.s.l, yielded ages of 32 ± 3 ka (Zech et al., 2007). The 10Be age was calculated using the Kubik and Ivo-Ochs (2004) calibration data and the scaling system of Desilets and Zreda (2003) (5.25 10Be atoms a1 g 1 SiO2 for neutron spallation and geomagnetic corrections). Further south, pollen evidence from a lake core obtained at the Tagua Tagua basin [89] shows an increase in percentages of the forest taxa Nothofagus olbiqua-type which is indicative of a much wetter environment s compared to the mediterranean environment today (Valero-Garce et al., 2005). On the eastern flank of the Andes, records from the NWA also show evidence for increased moisture, as suggested by La Poma [53]. This record suggests important mass movements during a wet phase that occurred between 40 and 25 ka BP. These mass movements dammed valleys forming paleolakes with finely laminated sediments and suggest greater inter and intra-annual fluctuations in precipitation compared to the present (Trauth and Strecker, 1999; 2000, 2003). 4. Results For each of the seven time-windows mapped based on a total of 92 paleoclimatic records (including those that were recalibrated) we explain the general trends regarding moisture anomalies. 4.1. 32 ka BP A total of ten records dated between 33.9 and 31.4 ka BP were included (Fig. 4). There are only 3 negative records from BAativeand seven with positive moisture anomalies during this interval along the SCA. Correlations of radiocarbon dated alluvial facies in sediment cores obtained in the Desaguadero valley (~18 S), which includes cores from Caquingora [4] (numbers in italics here refer to the same keyed number in Fig. 3, this is the proxy record number) and Huana Khaua [15]) are indicative of drier (or intermittently wet) conditions from 38 to 26 ka BP (Rigsby et al., 2005). This dry phase was preceded and succeeded by lacustrine facies and paleowetlands indicative of wetter climates before and after this interval in the Desaguadero valley (Rigsby et al., 2005). A different result is reported from a core obtained from the Uyuni salt flat [26] in Baker et al. (2001), where lacustrine muds suggest a wet event from 33.4 to 31.8 ka BP. In contrast, a core from the same Uyuni salt flat [25] suggests arid conditions due to the presence of salt crusts dated to the interval spanning 35e22 ka BP (Fornari et al., 2001). Several records from the Atacama Desert (CA and SA) provide evidence for positive moisture anomalies at 32 ka BP. These include a U-series dated salt core obtained from Salar de Atacama [42] and AMS 14C-dated rodent middens from Quebrada Juncal [61]. Large chevron halite crystals formed during a saline perennial lake, and show wetter conditions from 54.3 to 15.3 ka BP (Bobst et al., 2001). Extralocal taxa (Phacelia pinnatifida, Jarava frigida) found at higher elevations today occur in midden macrofloras at Quebrada Juncal [61], which can be attributed to an increase in local rainfall (Díaz et al., 2012). Pollen from rodent middens collected at Quebrada 4.2. 21 ka BP For this map, we compiled all published records from the SCA dated to the interval 22.2e20.2 ka BP spanning the Last Global 4 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 Fig. 3. Location and proxy type of the 92 records compiled in this study. See Supplementary Materials for a list of site references. during much wetter conditions in relation to the present, such as the Tauca (18.1e14.1 ka), Inca Huasi (ca. 46 ka) or Ouki (120e98 ka) cycles (Placzek et al., 2006, 2013). In contrast, three other records from elevations above 3000 m asl (SCA) have been interpreted as evidence for major increases in precipitation during the LGM. Low d18O values at Nevado Sajama [5] are interpreted as evidence for increased snow accumulation and wetter conditions between ~21 and 18 ka from a core drilled into the summit (Thompson et al., 1998) (Fig. 5). Very wet conditions have also been interpreted from much higher values of natural g-ray radiation in mud (lacustrine muds and planktonic diatoms) present in a salt core in the Uyuni basin [26] (Baker et al., 2001). This contrasts with evidence from a 121 m salt core also drilled in the Salar de Uyuni basin [25] that shows no evidence for increased lake levels during the LGM, such as mud layers with diatoms, and instead shows salt crust development from ~37.9 to ~19.2 ka BP (Fornari et al., 2001; for further discussion of these ages, see also Placzek et al., 2013). A wetter than today climate was also interpreted from the Huana Khau record [15] denoting increased accumulation of voluminous Glacial Maximum (LGM- Mix et al., 2001; Hughes et al., 2013) (Fig. 5). A total of 16 records distributed across the Bolivian Altiplano, the Central Atacama, Central Chile and the Cuyo Region provide information on past climate during the LGM. These include fluctuations of paleolake levels based on the dating of preserved shorelines in Uyuni Basin [21] (Placzek et al., 2006, 2013), salt cores from Salar de Uyuni [26] (Baker et al., 2001; Fornari et al., 2001), alluvial deposits in the Desaguadero Floodplain [15] (Rigsby et al., 2005) and ice cores from Nevado Sajama [5] (Thompson et al., 1998). The resulting proxy-based climate reconstruction during the LGM (Fig. 5) reveals a complex scenario. For example, shoreline data from the Salar de Uyuni [23] (BA) suggest only a slight increase in paleolake levels from 24 to 20.5 ka BP (ca. 5 m above the salt flat surface, the Sajsi event), (Placzek et al., 2006, 2011, 2013). The presence of a shallow paleolake during the Sajsi phase (paleolake cycles - 24 to 20.5 ka BP) has been interpreted as forming due to reduced evaporation in a much colder and relatively dry climate in relation to other paleolake cycles in the Uyuni basin, which formed 5 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 Fig. 4. Records compiled for the 32 ka BP interval. See Supplementary Materialsfor list of site numbers and references. extralocal shrub Baccharis tola, which would indicate a slight increase in mean annual precipitation at 3000 m a.s.l (~10e20 mm, Latorre et al., 2006). Rodent middens further south at Tilocalar [47] reveal the presence of a very cold, drier than present and sparsely vegetated ecosystem (Betancourt et al., 2000; Latorre et al., 2003). A lake core from Laguna Miscanti [44] points to not only much drier conditions during the LGM but also to much colder, as indicated by glaciofluvial outwash derived from the adjacent eastern cordillera in the Desaguadero floodplain (BA) that was dated using bulk radiocarbon dating on muds (Rigsby et al., 2005.). Further south, most records from higher elevations (>2800e4500 m a.s.l) in CA are indicative of negative or no moisture anomalies during the LGM. A rodent midden collected at Río n, 2985 m a.s.l.) [32] indicates the presence of the Salado (El Sifo 6 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 Fig. 5. Records compiled for the 21 ka BP (LGM) interval. See Supplementary Materials for list of site numbers and references. moraines using 10Be and 36Cl yielded 20.8 ± 1.5 to 18.2 ± 2.8 ka in the Chajnantor Plateau [39] (4585 m a.s.l.) (Ward et al., 2015), are synchronous with the exposure ages for debris flow boulders (36Cl) dated to 20.2 ka [40] in the same sector, but 2000 m a.s.l below the Chajnantor Plateau (Cesta and Ward, 2016). In both cases, expanded glaciers and enhanced alluvial activity have been interpreted as a wetter than present climate during the LGM. the complete absence of pollen from this portion of the record (Grosjean et al., 2001) which is also absent from the Lake Titicaca pollen LGM record (Bolivia) (Paduano et al., 2003). In contrast, “chevron” halite (instead of the usual efflorescent halite crust) preserved in the Salar de Atacama [42] salt core has been interpreted as evidence for wetter conditions (Bobst et al., 2001). On the other hand, cosmogenic surface-exposure dating of boulders on 7 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 versus a mud phase by Baker et al. (2001) in the same Uyuni basin [25]. Paleoecological evidence from the NA suggests very wet conditions. Abundant fossil leaf litter deposits of the willow-like Escallonia agustifolia tree were present along much of the Lluta valley [11] up to 15 m higher up on the slopes. As these slopes today are hyperarid, their presence implies a much higher groundwater table than today between 38 and 15.4 ka BP. Groundwater tables plummeted after 15.4 ka BP, most likely caused by intensified incision due to increased stream power and runoff from the Río Lluta headwaters in the Andes Cordillera (Veit et al., 2016). In situ rhizoliths and plant macrofossils occur along fluvial terraces at Sipuca [30] in the Pampa del Tamarugal basin (Nester et al., 2007; Gayo et al., 2012), which today lacks vegetation (absolute desert). These plant macrofossils and rhizoliths were dated between 17.8 and 16.9 ka BP, indicative of increased discharge at relatively low elevations (1250 m a.s.l, Central Depression). Other records from the Pampa del Tamarugal, such as Quebrada Maní [29], also suggest wetter conditions, associated with extensive paleowetlands that developed between 17.6 and 15 ka BP (Workman et al., 2020) due to elevated regional groundwater tables. Positive moisture anomalies have been established in the CA n in the Río Salado basin from rodent middens collected at El Sifo [32] with rainfall increases of at least 60 mm/yr in relation to the present day (a 75% increase) (Latorre et al., 2006). Further south, along the coastal range at Sierra el Buitre [56], a rodent midden dated to 17.3 ka BP shows the presence of extralocal Andean species (Adesmia atacamensis; Cryptantha diffusa) indicative of longdistance dispersal events that were likely facilitated by increased runoff across hyperarid sectors in the Atacama Desert (Díaz et al., 2012). Formation of crystalline halite in a saline perennial lake have also been interpreted as wet conditions between 53.4 and 15.3 ka BP in the Salar de Atacama basin [42] (Bobst et al., 2001). In contrast, pollen and sediment limnogeochemical analyses from Laguna Miscanti [44] suggest the disappearance of this freshwater lake under drier conditions than today between 22 and 14 ka BP (Grosjean et al., 2001). In the SA, much wetter conditions have also been inferred from rodent midden pollen in the higher elevations (3450 m), which show abundant steppe grasses at Quebrada del Chaco III [57]. Today, these steppe grasses occur at slightly higher elevations and dominate the landscape at 4000 m a.s.l (Maldonado et al., 2005; Latorre et al., 2005). Further south in the SC and CC, a terminal moraine in the headwaters of the Río Turbio valley [75] (>4000 m a.s.l) was dated to 17e12 ka BP and is indicative of increased moisture availability attributed to an increase in summer precipitation (Riquelme et al., 2011). Elevated moisture availability between 19.5 and 17 ka BP was also inferred from an increase in forest taxa and associated decrease in Amaranthaceae pollen in the Tagua Tagua record from central s et al., 2005). In NWA, the presence of a Chile [89] (Valero-Garce saline lake from 21 to 13.8 ka BP in the Guayatayoc Salt Flat [43], is interpreted as a climate much wetter than today. Further south, rodent midden records from the SA have been interpreted as evidence for a wetter LGM. These include rodent midden records from Cerro Tres Tetas [50] (1900 m a.s.l), which reveal the presence of considerably more diverse desert floras than those present today (Díaz et al., 2012). Pollen (especially the presence of Asteraceae- Chaethantera type) and plant macrofossils from LGM middens collected at Quebrada Chaco I [60] (2600 m a.s.l. - a hyperarid, plantless environment today) show the presence of numerous Andean taxa (>3000 m a.s.l) that included perennials and annuals as well as elevated species richness (Latorre et al., 2005; Maldonado et al., 2005). Even further south at 32 S, a wet period likely ended by ~22 ka BP, when paleosols were buried by eolian sand dunes in coastal CC indicative of a return to arid or similar to present conditions (García et al., 2019). At 34 S, a medial moraine indicative of an ice advance dated to 20.4 ka was dated in the Cachapoal valley [87] (1505 m a.s.l) suggesting cold and wet conditions in Central Chile (Charrier et al., 2019). Pollen and geolimnogeological evidence from a sediment lake core from Laguna Tagua Tagua (Central Chile) [89] are suggestive of very wet conditions between 40 and 21 ka (Fig. 5) as indicated by increases in arboreal pollen and aquatic vegetation, among other limnological proxies. This period was followed by more arid conditions than present (~21e19.5 ka BP) as inferred from the increase of Amaranthaceae pollen percentages along with s et al., 2005). evidence for a decreased lake level (Valero-Garce Increased aridity has been described for CR, where sand dune deposition occurred at ~22 ka BP near San Rafael [88] at ~34 S (Tripaldi et al., 2010). 4.3. 17 ka BP There are many records available for this time interval (n ¼ 23, Fig. 6). These are from the BA, NA, CA, SA, SC and CC and the CR. Records from BA all indicate considerably wetter climates throughout the region. These records are diverse, such as the Sajama ice core [5] which shows both low aerosol concentrations and very negative d18Oice values that resulted from increased snow accumulation and much wetter conditions (Thompson et al., 1998). A major glacial advance occurred at Tunupa volcano [24] was also determined from 3He exposure dating on pyroxene phenocrysts from boulders resting on moraines (Blard et al., 2009). Three sediment cores (with alluvial/fluvial stratigraphy) from the Desaguadero floodplain in the Bolivian Altiplano (Manquiri [1], Zambrana [2] and Huana Khaua [15]) suggest abundant discharge from large tributaries in the Desaguadero river and the formation of large lakes in the central and southern Desaguadero river floodplain, all of which have been interpreted as the prevalence of a large positive moisture anomaly (Rigsby et al., 2005). These records are also consistent with evidence for planktic diatoms (Cyclotella striata) and charophyte algae preserved in shoreline features (Pakollo Jahuira [18], Pisalaque[20] and Churacari Bajo [23]) that suggest a shoreline 27 m higher than the current Salar de Uyuni surface (Sylvestre et al., 1999). Exposed sections at Vinto [7] and Toledo [12] revealed geosols (a paleosol stratigrapically interbedded between two paleolake cycles), indicative of landscape stability which caps the lake transgressions to elevations below 3700 m. a.s.l from 95 to 17 ka (Placzek et al., 2006, 2013). Evidence for a prominent paleolake known as the Tauca phase (18.1e14.1 ka BP), is found throughout the Uyuni basin, reaching a maximum extent of 60,000 km2 and a water depth of 140 m over what today is a dry salt flat between 16.4 and 14.1 ka BP) (Placzek et al., 2006, 2013). Very wet conditions are also recorded in a salt core at Uyuni [26], which reveals alternating phases of muds (paleolake) and salt (gypsum and halite) for the last 50 ka (Baker et al., 2001). In contrast, Fornari et al. (2001) evidence a salt phase which suggests arid condition 4.4. 14 ka BP A total of 33 records with dates between 14.3 and 13.7 ka BP occur throughout the SCA (Fig. 7). 45% of these come from the BA; 15% is from the NA, 15% from the CA and 9% from the SA. 9% records are from the SC and 3% is from CC. The remainder are from NWA (3%). Records from the Bolivian Altiplano mostly show very positive moisture anomalies (þ2). For instance, planktonic diatoms and other aquatic plants in sediment cores obtained from the 8 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 Fig. 6. Records compiled for 17 ka BP interval. See Supplementary Materials for list of site numbers and references. associated with the final phase of “Tauca Paleolake”, which is dated from 18.1 to 14.1 ka BP (Placzek et al., 2006). Moreover, glaciers were advancing in the Nevado Sajama, such as Huaji Jihuata [6]at 14 ± 0.5 ka BP. These ice advances occurred between 16.9 and 11.3 ka BP (Smith et al., 2009). In contrast, a brief positive d18Oice excursion occurs in the Nevado Sajama ice core [5] from 14.3 to 14.0 ka BP indicative of very arid conditions, together with increased Desaguadero Floodplain at Tejopa [3] and Huana Khau [15] show evidence for much wetter conditions compared to today (Rigsby et al., 2005). A similar condition occurs at Salar de Uyuni based on evidence from a salt core and elevated shorelines. Shorelines ~ a [13], Salar de occurring in the northern Salar Coipasa [16], Pazn Uyuni [21], northern Salar de Uyuni [19], southern Salar de Uyuni [27], and in the southern sector of Salar de Coipasa [22] are all 9 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 Fig. 7. Records compiled for the 14 ka BP interval. See Supplementary Materials for list of site numbers and references. was originally interpreted from the presence of alluvial sands along the margins of the Coipasa and Uyuni salars deposited under generally dry conditions (Sylvestre et al., 1999). These sands contained freshwater mollusk shells reworked from preexisting Tauca lake deposits (Sylvestre et al., 1999). A few other records (Alianza [24] and Huacuyo [17]) in the Uyuni basin, however, are suggestive dust in the ice core (Thompson et al., 1998). This possibly correlates ~ a event” dated between 14.1 and 13.8 ka BP with the arid “Tican (Sylvestre et al., 1999; Baker et al., 2001; Placzek et al., 2006) ~ a [17] and in a salt core from apparent in the Uyuni basin at Tican the same basin [26]. This event occurred between the paleolake Tauca (18.1e14.1 ka BP) and Coipasa (c. 13 to 11 ka BP) phases and 10 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 short dry event occurred at c. 9.5 ka BP [10] (Moreno et al., 2007). Pollen from Andean Forest taxa at Laguna Seca [8] suggest a climate cooler and wetter than today until about 9 ka BP (Baied and Wheeler, 1993). An in-situ tree trunk found in alluvial sediments at Pampa del Tamarugal has been dated directly to 9.4 ka BP cal. BP, indicative of wet conditions at the time it grew as the hyperarid environment today has no vegetation (Nester et al., 2007). In contrast, onset of aridity is inferred in the CA. First, efflorescent halite crust began to accumulate in the Salar de Atacama salt core [42] at 9.5 ka BP (Bobst et al., 2001). Aridity also occurred along the Río San Salvador [34] where channel downcutting (which occurs during droughts) is evident between 9.8 and 6.4 ka BP (Tully et al., 2019). In the SA, paleowetlands dried out around 9.7 ka BP, with sediments deposited afterwards forming under low groundwater tables typical of a phreatic playa at Quebrada Guanaqueros [49], El Salto [51] and Punta Negra [52] (Quade et al., 2008). Further evidence for negative moisture anomalies in the CA comes from the disappearance of steppe grasses and the predominance of prepuna taxa (more arid) on open slopes and small mountain ranges from almost all published rodent midden records, including those at Cerros de Aiquina [33], Lomas de Tilocalar [48], Cordon de Tuina [35] and El Hotel- Paso Barros Arana [37] (Latorre et al., 2003; 2003). The pollen record from these same rodent middens at Cerros de Aiquina supports these conclusions (De Porras et al., 2017). In contrast, plant macrofossils from El Sifon rodent middens [32] have been identified as Andean steppe grasses, which do not exist at present at this site, implying the persistence of slightly wetter conditions (Latorre et al., 2006). Positive moisture anomalies are also inferred from geochemical and pollen evidence at Laguna Miscanti [44] (Grosjean et al., 2001). SA midden pollen records from Quebrada La Zorras [53] show pollen assemblages typical of more transitional communities, characterized by Amaranthaceae, Brassicaceae and Adesmia, all indicative of wetter conditions than present, but drier than assemblages from the Late Pleistocene (De Porras et al., 2017). Two SA records indicate arid conditions. A stratigraphic sequence of groundwater (paleowetland) deposits from Aguada Alto Varas [55] shows massive breccia layers interpreted as alluvial fan channels and the absence of organic layers at this time (which are interpreted as times of spring inactivity) due to overall arid conditions ez et al., 2016). (Sa SC records all show arid conditions. Exposure 10Be ages on boulders show that buried glacier ice at Valle Encierro [69] had disappeared by 9.3 ka BP (Zech et al., 2006). Glacier retreat and deposition of alluvial debris cones in the Río Turbio valley [73] are also interpreted as negative moisture anomalies (Riquelme et al., 2011). Local dominance of herbaceous and coastal shrubs in pollen assemblages between 9.5 and 9.0 ka BP at Santa Julia [79] also indicate drier conditions (Maldonado et al., 2005). This is further supported by geomorphological and alluvial stratigraphy at Quebrada Santa Julia [79] (Ortega et al., 2012), where the presence of clayey muds as well as scant and fine-grained alluvial deposits provide further evidence for dry conditions, concomitant with sporadic precipitation events that were able to transport very fine sands. In contrast, intense snow accumulation at high elevations accompanied by alluvial fan deposition has been interpreted as an increase of precipitation associated with the southern Westerlies, such as those present at Juntas Turbio y Seco [73] (Veit, 1996). Positive moisture anomalies are also inferred from the presence of swamp forest indicators Myrtaceae and Escallonia at the coastal n, 2006). A lake Palo Colorado site [81] (Maldonado and Villagra core from Laguna El Cepo [76], shows the start of an arid phase at 9.5 ka BP, inferred from lack of a coarse fraction and lower C/N values suggesting arid climates (Tiner et al., 2018). CC records all show negative moisture anomalies. The lack of of wetter conditions, as evidenced by the presence of lacustrine sediment at 14.1 ka BP (Sylvestre et al., 1999) before the collapse of the Tauca paleolake cycle. Records from the NA suggest wetter conditions. Sedimentary facies including diatom oozes suggest very wet conditions in a core from Lago Chungara [10] (Moreno et al., 2007). Steppe grasses and other extralocal taxa (Cumulopuntia boliviana, Oreocereus leucotrichus and Solanum sp.) occurred at lower elevations than today at 14.4e11.6 ka BP as revealed by rodent middens from Quebrada La Higuera [14] (Mujica et al., 2015). Similarly, alluvial deposits and wetland outcrops with plant macrofossils occur in the hyperarid Pampa del Tamarugal basin in places such as Lomas de la Sal [31] and Chipana [28] between 17.6 and 14.1 ka BP (Gayo et al., 2012; Pfeiffer et al., 2018). In contrast, more recent stratigraphic evidence from Quebrada Mani [29] also in the Pampa del Tamarugal basin, shows evidence for an erosive unconformity with deposition of eolian sands from to >13 - <15 ka BP (Workman et al., 2020). Abundant grass pollen together with very low Amaranthaceae percentages correlates with a major lake transgression at Laguna Miscanti [44] (Grosjean et al., 2001) in CA. Further evidence for wet conditions is inferred from extensive wetlands that formed during this interval along the western Andean piedmont at Tilomonte [45] and Salar de Punta Negra [52] (Rech et al., 2002; Quade et al., 2008). In contrast, the Salar de Atacama salt core in [42] shows the formation of subaerial halite between 16.5 and 11.4 ka BP (Bobst et al., 2001). A rodent midden from El Sifon [32] in the Río Salado basin directly dated to 14.2 ka BP shows that mean annual rainfall declined to modern conditions, as this midden lacks plant macrofossils from the Andean steppe or other wet indicator taxa (Latorre et al., 2006). Intense aridity with lowered groundwater tables has been inferred from alluvial sediment sections in Alto Varas [55] in the SA (S aez et al., 2016). The only exception is a brief wet interlude at c. ez et al., 2016). 14.5 ka BP evidenced by a black peat layer (Sa Records show wetter climates in SC and CC. Exposure ages on boulders resting on lateral moraines LM and the terminal moraine M-II B yielded an age of 14 ± 0.6 ka BP and indicate a late glacial advance in the Encierro valley [69] (Zech et al., 2006). Aguilar (2010) however, proposes that these glacial sediments were reworked (Encierro valley [67)], and the moraines were altered (moraine settlement) around 14 ka BP. Further south in the headwaters of the Turbio valley [75], a glacial advance has been dated to 17e12 ka BP based on glacial lacustrine succession (Riquelme et al., 2011). A large decrease in Amaranthaceae pollen and concomitant increase in lake levels is also interpreted as positive moisture s et al., anomalies in the Tagua Tagua basin [89] (Valero-Garce 2005). In NWA, similar wet conditions occurred at Guayatayoc [43], where evidence for a aline lake occurred from 21 to 13.8 ka BP. 4.5. 9.5 ka BP A total of 31 records distributed across the SCA (Fig. 8) comprise this interval, including records from BA, NA, CA, SA, SC, CC, NWA and CR. Overall, the records available show highly variable moisture anomalies even within the same subregions. For example, two records from BA show evidence for wetter conditions. These include a paleowetland record from Huana Khaua [15], which has been interpreted as wetter than present conditions between 10 and 7.9 ka BP (Rigsby et al., 2005). Decreased soluble anions (SO4e and Cl-) and dust remained low in the Nevado Sajama ice core [5] from 14 until 9 ka BP, indicative of wetter climates and higher paleolake levels across the BA (Thompson et al., 1998). Concomittantly with the BA, NA records also show positive moisture anomalies. A low Ca/Ti occurs in the Lago Chungara (lake core) c. 11 to 7.5 ka BP and is linked to wetter conditions, although a 11 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 Fig. 8. Records compiled for the 9.5 ka BP interval. See Supplementary Materials for list of site numbers and references. taxa almost disappeared and were replaced by grasses along with s et al., 2005). lowered lake levels (Valero-Garce NWA records all indicate positive moisture anomalies. For example, planktonic diatoms have been described from the Hornillos II [41] archaeological site (Yacobaccio and Morales, 2005) and pollen at Laguna Aculeo [86] has been attributed to more arid conditions and very low plant productivity (Jenny et al., 2002), coupled with low lake levels inferred from the presence of evaporites indicative of increased arid conditions (Jenny et al., 2002). A similar situation occurred at Tagua Tagua [89] where regional forest 12 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 broad floodplains with organic soils dominated by grasses imply an elevated and stable water table at Pasto Chicos [46] (Tchilinguirian et al., 2014). A wetter climate is also inferred from sedimentary facies changes and diatom records at Antofagasta de la Sierra [62] (Grana et al., 2016). In contrast, CR records show more arid than current conditions during the Early Holocene. Pollen evidence from a cave sediment record at the rockshelter Gruta el Indio [90] suggests a lower than present precipitation regime and higher than present temperatures between 12 and 8.5 ka BP (Gil et al., 2005). occurs in the Salar de Atacama salt core [42] suggesting a positive moisture anomaly (Bobst et al., 2001). SA records show negative moisture anomalies. These include rodent middens from the higher elevation site of Quebrada el Chaco III [57] which have low taxa richness and low levels of steppesubnival and puna taxa (Maldonado et al., 2005; Latorre et al., 2005). A lake core from Laguna Negro Francisco [63] shows abundant evaporites, indicating very arid climate (Grosjean et al., 1997a,b). A rodent midden record from Quebrada Juncal [61], however, shows no moisture anomaly (climate similar to modern) based on species richness and composition that are similar to today around 6.1 ka (Díaz et al., 2012). Three SC records all have been interpreted as more arid than today. Strong, infrequent storms and subsequent debris flows in an overall arid climate have been cited to explain the formation of down-cut alluvial fans along the Río Turbio valley [67] (Riquelme et al., 2011). A peat layer at Pabellon [71] dated to 5.9e5.5 ka BP has been interpreted as the product of very low sedimentation and strongly reduced alluvial activity, interpreted as arid conditions (Veit, 1996). A similar situation occurred at Quebrada el Transito [66], where the presence of wetland deposits and the soil formation on the alluvial fans have been interpreted as low sedimentation rates associated with arid conditions between 7 and 5.5 ka BP et al., 2017). A predominance of open vegetation and her(Cabre ~ baceous taxa documented in the Nague I pollen record [80] denotes n, increased aridity for the region also (Maldonado and Villagra 2002). “Pollen-starved” sediments with only scant presence of semiarid vegetation (only shrub taxa) have been interpreted as evidence for extremely arid climates in relation to today between 8.7 to ~5.7 ka BP at the Palo Colorado [81] swamp forest n, 2006). Just 26 km north of Palo Colorado (Maldonado and Villagra at Quebrada Santa Julia [79], geomorphological and alluvial sedimentary evidence suggest episodic and torrential rainfall events under an arid climate setting between 8.6 and 5.7 ka BP (Ortega et al., 2012). Coarser and poorly sorted grain-size distributions and higher C/N ratios occur in Laguna el Cepo [76], which implies arid conditions from 9.5 to 5.5 ka BP (Tiner et al., 2018). Paleosol, pollen and lake CC records also show negative moisture anomalies. A sparse herbaceous flora was present under warmer and drier conditions at Quintero II [83] (Villa-Martinez and Villagr an, 1997). Formation of an A-horizon (soil) near Valparaiso [84] has been interpreted as a period of aridity, where the fog is reduced in these erosive periods. The soils reflect the lack of deep water infiltration, because they are only characterized by the accumulation of organic material (A-horizons) (Veit, 1996). Elevated percentages of Amaranthaceae and low arboreal pollen also occur in a lake core from Laguna Aculeo [86] (Jenny et al., 2002). Extensive wetland surface fluctuations with relatively high and variable content of Typha (herbaceous), almost no arboreal pollen and low lake levels all occurred in the Tagua Tagua record s et al., 2005). [89], indicative of very arid conditions (Valero-Garce Across the Andes, NWA records such as Pastos Chicos [46] show an increase of shrub/steppe pollen taxa and the absence of peat sediments until downcutting suggests a decrease in vegetation cover and sediment supply, interpreted as drier climatic conditions between 6 and 4.2 ka BP (Tchilinguirian et al., 2014). Aridity may have been even more intense at Antofagasta de la Sierra where diatom assemblages at Laguna Colorado [62] exhibit a low planktonic to benthic species ratios, indicating a shallow lake from 7.2 to 3.5 ka BP. River flow at Antofagasta de la Sierra was also ephemeral rather than perennial c. 6.7e4.8 ka BP, as inferred from diatom proxies, due to increased aridity (Grana et al., 2016). Further south, CR records also show contrasting evidence. The Salinas 2 record [92] indicates wetter conditions as suggested by elevated percentages of Ephedra and the presence of lacustrine clay 4.6. 6.0 ka BP The Middle Holocene (Northgrippian) interval has a total of 30 records in the SCA which were compiled into our database (Fig. 9). A large proportion of these records agree with each other as to widespread negative moisture anomalies present throughout the SCA. Some important exceptions in the CA and CR, however, are also present. Three BA records show opposite trends. A36Cl exposure date on a ground moraine plateau on the eastern flank of Nevado Sajama [6] indicates that ice must have retreated after 6 ka BP, but the presence of glacial deposits in advanced positions indicates that it may not have been as dry and warm as current conditions (Smith et al., 2009). In contrast, the Sajama ice core shows enhanced dust deposition associated with an elevated snowline and decreased net accumulation [5] (Thompson et al., 1998). A sequence of alluvial sediments at Huana Khau [15] and a lack of lacustrine sediments in the río Desaguadero are interpreted as drier than today from 7.9 to 4.5 ka BP (Rigsby et al., 2005). NA records such as Laguna Seca [8] shows a shift from clayey silt to peat together with vegetation changes (i.e., Brassicaceae, Azorella) between 7 and 5 ka BP indicative of a lowering of the water table and negative moisture anomalies (Baied and Wheeler, 1993). Limnogeochemical evidence from Lago Chungara (lake core) [10] shows that this period was possibly the most arid during the Holocene, indicating that the lake went through an “aridity crisis” from ~8.6e6.4 ka BP which then recovered to modern levels by 6 ka BP (Moreno et al., 2007). Despite the large uncertainties of the Chungara age-depth model (Giralt et al., 2007) this arid period is further constrained by AMS 14C dates on terrestrial charcoal from nearby Hakenasa rock shelter, which shows that humans abandoned this site between ~7.9e6.9 ka BP, presumably in response to increased aridity but then reoccupied it afterwards (Moreno et al., 2009; Osorio et al., 2011). CA records disagree over whether the interval was wetter or drier than today. Lack of aquatic pollen and the presence of gypsum layers in the Laguna Miscanti core [44] are interpreted as strong negative moisture anomalies (Grosjean et al., 2001). Increased aridity is also suggested by the stratigraphy and incision (downcutting) of in-stream wetlands deposits, along a 4.3-km reach of the Río San Salvador between 6.4 and 3.5 ka BP (Tully et al., 2019). Middle Holocene fine-sediment (in-stream wetland) deposits at Quebrada de Puripica [38] have been interpreted as either having formed by side-canyon damming during very arid conditions (Grosjean et al., 1997a,b) or more recently, as evidence for elevated groundwater tables during a wetter climate (Rech et al., 2003). Slightly wetter conditions than present have also been inferred from rodent midden records at Lomas de Tilocalar [47] and Pampa Vizcachilla [36], which show evidence for the presence of sparse puna shrubs, C4 annual plants (indicative of summer rainfall) and other extralocal perennial taxa (Betancourt et al., 2000; Latorre et al., 2003; 2003). The presence of steppe grasses at Pampa Vizcachilla [36] points to a two-fold rainfall increase (Latorre et al., 2003). Further south in Quebrada La Zorra [53], rodent midden pollen shows puna taxa (Adesmia) at 6.1 ka, which could indicate a brief wetter episode (De Porras et al., 2017). Patchy primary halite 13 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 Fig. 9. Records compiled for the 6 ka BP interval. See Supplementary Materials for list of site numbers and references. 4.7. 4.0 ka BP layers in a core from a peat mound (Markgraf, 1983). Large increases in Poaceae, Larrea and Prosopis along with other Monte Desert taxa occur in Agua la Cueva [82] all indicative of a strong positive moisture anomaly (Navarro et al., 2010). In contrast, only slightly further south a pollen record from Gruta el Indio [90] suggests very arid conditions (Gil et al., 2005). A total of 29 different records across the SCA were compiled for this time interval. Interpretations are diverse, with 16 records interpreted as positive moisture anomalies, seven as negative and six showing modern climates (Fig. 10). 14 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 Fig. 10. Records compiled for the 4 ka BP interval. See Supplementary Materialsfor list of site numbers and references. the presence of increased moisture in the Desaguadero valley (Rigsby et al., 2005). Just across the border, NA records show an increase of aquatic and Andean arboreal pollen at Laguna Seca [8] interpreted as evidence for a positive moisture anomaly (Baied and Wheeler, 1993). Geolimnological proxies at Lago Chungara [10] indicate environmental conditions similar to today (Moreno et al., 2007). BA records include enhanced dust concentration associated with an elevated snowline and high concentration soluble aerosol (SO2 4 ; CI ) at Nevado Sajama [5] suggestive of arid conditions (Thompson et al., 1998). In contrast, exposure ages on moraines show a glacial advance at Huaqui Jihuata [6] in the western Cordillera between 4.7 and 3.3 ka BP (Smith et al., 2009). Lacustrine strata at Huana Khaua [15] and other localities have been argued for 15 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 core from a peat mound at Salinas 2 [92] shows clay layers that formed during a lake transgression coupled with a large decrease in Ephedra and increases in Poaceae pollen, all indicative of increased precipitation (wet condition) (Markgraf, 1983). Organic rich levels formed by wetlands dominated by Cyperaceae, Juncaceae and Poaceae are found along the distal facies of the Arroyo Bayo alluvial fan at Agua Buena [85] are associated with a highly productive environments and increased available moisture (Navarro et al., 2010). Most CA records indicate positive moisture anomalies. At Quebrada Puripica [38] the presence of perched, exposed fine-grained sediments throughout this valley have been interpreted as periods of elevated groundwater tables and increased aquifer recharge (Rech et al., 2003). Patchy primary halite occurs in Salar de Atacama [42] is also indicative of wetter conditions (Bobst et al., 2001). Slight increases of summer flowering grasses in rodent middens have been interpreted as evidence for wetter conditions at Lomas de Tilocalar [47] (Latorre et al., 2003). Elevated plant species richness and the presence of extralocal Andean species at Sierra del Buitre [58] have also been interpreted as evidence for wetter conditions in the coastal cordillera (Díaz et al., 2012). Pollen and geolimnological evidence from Laguna Miscanti [44] however, shows climate similar to today (Grosjean et al., 2001). Incision (downcutting) of in-stream wetlands deposits suggest arid conditions between 6.4 and 3.5 ka BP at Río San Salvador [35] (Tully et al., 2019). Midden pollen records of prepuna and puna taxa, characterized for Amaranthaceae, Brassicaceae and Malvaceae at Quebrada Zorras [52], are indicative of drier conditions than present (De Porras et al., 2017). In contrast, SA records show wet conditions as indicated by a black peat layer in the alluvial section at Quebrada ez et al., 2016). Geolos Sapos [55] and dated to 3.9 ka BP (Sa limnological evidence from further south at Laguna del Negro Franscisco [63] has been interpreted as indicating arid conditions (Grosjean et al., 1997a,b). SC records show increased snow cover and alluvial deposition at several sites, including Los Loros [64], Las Rojas [74] and Junta Río Toro [72], all of which are interpreted as evidence for strong positive moisture anomalies (Veit, 1996). Basal peats, which have been 14 C-dated to 4.4e3.9 ka BP in the Valeriana valley [68] have also been interpreted as evidence for increased moisture (Grosjean et al., 1998). This positive moisture anomaly is also present in the Río Turbio Valley [75], where a second paraglacial episode occurred after 7.8 ka BP, but most likely later than 5.5 cal ka BP, as dated by wood present in debris cones. This episode is characterized by increased fluvial transport capacity and reflects a change towards wetter conditions (Riquelme et al., 2011). Swamp forests appear and arboreal taxa such as Luma chequen and Escallonia revoluta ~ show that climate was similar to the present at Nague I [80] (Maldonado and Villagran, 2002) although nearby Palo Colorado [81] has been interpreted as wetter conditions, based on the ren, appearance of swamp forest taxa (Maldonado and Villagra 2006). At Laguna el Cepo [70], however, a change in mean grain size and sorting parameters occurred between 4.1 and 2.2 ka BP, suggest increased frequency of storms and relatively dry conditions as compared to present (Tiner et al., 2018). In contrast to most SC paleorecords, CC records mostly indicate negative moisture anomalies (i.e., 1). The predominance of halophytes at Quintero II [83] before the modern swamp forest vegetation appeared, suggests arid conditions (Villa-Martinez and n, 1997). An increased arboreal component and lower perVillagra centages of Amaranthaceae have been interpreted as evidence for increased moisture at Laguna Aculeo [86] but these percentages were still below those seen in more recent sediments (Jenny et al., 2002). Similar pollen assemblages have also been documented at Tagua Tagua [89] and share the same interpretation: climate became increasingly wetter, but not as wet as that inferred from s et al., 2005). more recent assemblages (Valero-Garce NWA records show negative anomalies at 26 S with positive anomalies further south. Sedimentary facies and diatom assemblages from a fluvial deposit at Antofagasta de la Sierra [60] are interpreted as very arid conditions (Grana et al., 2016). Further south, however, hygrophytic communities expanded (Asteraceae and Cyperaceae), probably linked to fluvial cutoffs and back swamp environments at La Estancada Creek [80] (Rojo et al., 2012). A short 4.8. Comparison of paleorecord time windows with the TRACE-21 model simulation The comparison of our time windows with TRACE-21 model simulations are described below (Fig. 11). There are no simulations available with this model for 32 ka BP. The simulation shows a wet LGM (21 ka BP), with higher rainfall than at present for the entire SCA. While positive precipitation anomalies occur in the BA, this contrasts with paleorecords from Laguna Miscanti in Chile and Salar de Uyuni in Bolivia which indicate arid conditions. Positive anomalies persist at 17 ka and are in agreement with most records, all of which indicate very wet conditions across the entire SCA. At 14 ka the model suggests a positive precipitation anomaly in the BA, ~ a and Salar de which disagrees with data from the Sajama, Tican Uyuni paleorecords, all of which suggest arid conditions. At 9.5 ka, modelled precipitation anomalies tend to be more positive than the moisture anomalies observed in paleorecords found south of the CA, where a clear tendency to more arid conditions is seen. The model results agree more with BA paleorecords, where a trend of positive moisture anomalies is apparent. At 6 ka, the modeling suggests similar to present conditions for the entire SCA, which disagrees with the paleorecords as these show more arid conditions in CC and NWA. In contrast, records from the Atacama and Altiplano vary between arid and wet. At 4 ka the model shows very homogeneous precipitation anomalies throughout in the SCA, versus the large spatial differences seen in the proxies. 5. Discussion By compiling records into maps for any given time interval, we provide an explicitly spatial view of past climate change across the SCA during the late Quaternary. Although such comparisons can reveal conflicting records at local spatial scales (i.e., within a same basin or watershed), they can also aid in defining multi-scale responses to drivers of the climate system, such as local summer insolation during the LGM or ENSO-like regime shifts during the Holocene. We discuss these records and the implications of these maps (temporal windows) for each of our selected intervals below. 5.1. Spatial extent and climate change drivers in the SCA between 32 and 4 ka BP Our compilation of records at 32 ka BP shows wet conditions at least as far north as 22 in the SCA. An increase in winter precipitation, either due to a northward shift of the austral winter frontal systems or to an increased frequency of cutoff lows from the Pacific, which today reach 23 S (Vuille and Ammann, 1997) is one possible explanation. BA proxies suggest dry anomalies in the Desaguadero Valley, which have been attributed to decreased summer insolation and a weakened SASM (Rigsby et al., 2005). Placzek et al. (2013) suggest that the wet and dry phases over the Bolivian Altiplano may not be directly related to astronomical forcing, at least over the last 130 ka but may be related to cold stadials in the north Atlantic during the last 100 ka. Shoreline features around the Uyuni basin are lacking for this interval (46e24 ka ) (Placzek et al., 2006, 2013), 16 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 Fig. 11. TRACE-21 model simulations for the South-Central Andes for A) 21.5e20.5 ka BP, B) 17.5e16.5 ka BP, C) 14.5e13.5 ka BP, D) 10e9 ka BP, E) 6.5e5.5 ka BP, and F) 4.5e3.5 ka BP. except for the “Minchin” phase (Minchin, 1882; Steinmann et al., 1904; Servant and Fontes, 1978; Fornari et al., 2001) dated to 73e30 ka . Using UeTh ages on 14C-dated “Minchin” deposits, Placzek et al. (2006) show that this phase is probably an artifact of radiocarbon dating of much older carbonate deposits. Positive moisture anomalies at 32 ka BP are present in records from the CA and southwards, as suggested by the Salar de Atacama salt core and Quebrada del Chaco midden pollen record. It is very likely that these are due to northward shifts of the austral winter frontal systems, which today are rare but can occur in latitudes as far north as 23 - 25 S (Vuille and Ammann, 1997). This is further supported by the fact that positive moisture anomalies are present in all records south of these latitudes and on both sides of the Andes. Our analyses show major differences in moisture anomalies throughout the SCA at 21 ka BP during the global LGM. For the high Andes (>3000 m a.s.l) between 17 and 23 S, most records suggest either very wet or wet conditions, which have partly been attributed to maximum summer insolation in the southern hemisphere (~20 ka) (Berger and Loutre., 1991; Baker et al., 2001; Rigsby et al., 2005). Greater warming caused by increased insolation would favor maximum deep convection over Central South America (e.g., the Chaco Low), intensifying the South American monsoon (Zhou and Lau, 1998; Placzek et al., 2006, 2013). However, the occurrence of major paleolake phases in the BA coupled with hydrologic budget models, were not always consistent with the maximum local summer insolation, at least over the last 130 ka BP (Placzek et al., 2013). Another proposed mechanism for explaining the increase in precipitation in the high Andes (>3000 m a.s.l) at 21 ka BP is derived from the modern synoptic circulation regime of Andean climate (Garreaud et al., 2003) and simulated for the LGM (Vizy and Cook, 2007). These studies point out that precipitation variability in the SCA is not directly controlled by moisture changes in the Amazon Basin but rather by favorable easterly advection of moisture. This could explain why previous LGM climate models show more aridity in relation to today in the Amazon while it was wetter in the high Andes (>3000 m a.s.l) (Van der Hammen and Hooghiemstra, 2000; Vizy and Cook, 2007). Increased precipitation over the Altiplano (high Andes) occurs when the absence of convection over the Amazon in the austral spring strengthens the zonal geopotential height gradient resulting in anomalous easterly flow between the Amazon and Altiplano. Instead of the low-level flow paralleling the Andes (e.g., northwesterly), the flow impinges more directly onto the eastern slopes of the Andes during the LGM, where it rises and transports moisture from the Amazon up into the mountains, enhancing convection over the Andes (Fuenzalida and Rutllant. 1987; Chaffaut et al., 1998; Garreaud, 1999; Vizy and Cook, 2007). A lake core in northern Amazonia suggests that during glacial times there was no positive correlation between precipitation in the Altiplano and western Amazonia (Cordeiro et al., 2011). Finally, PMIP3 LGM simulations suggest a reduction Amazon Basin summer rainfall (Bermanm et al., 2016) linked to colder tropical Atlantic Sea surface temperatures and a reduction in ocean to continent advection (Arraut and Satyamurty, 2009). Our LGM map also shows contrasting reconstructions for the CA with both wet and dry anomalies in the high Andes (17 e27 S, 3000e4500 m a.sl.). Such contrasting local differences could be due to the same climate mechanisms proposed for the entire Altiplano (17 -27 S) i.e., that summer precipitation extended south of 22 S along the Pacific side of the Andes, which even today occurs to 27 S (Houston, 2006). The spatial scale representation of each proxy (from local to basin-wide) could also be important in explaining these discrepancies. Rodent middens are local records of climatic variability at (sub) decadal timescales (Grosjean et al., 2003) although the duration of a depositional episode is generally 17 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 airflow across the tropics, causing a reduction of moisture availability in the tropical lowlands to the east (Garreaud et al., 2003). Another proposed mechanism is the change in aridity over the Amazon (Vizy and Cook, 2007). Several authors (Betancourt et al., 2000; Garreaud et al., 2003; Placzek et al., 2006, 2013; Gayo et al., 2012) have proposed that the Tauca phase could have been ~ a-like conditions in the equatorial due by the prevalence of La Nin Pacific between 18 and 13 ka (Palmer and Pearson, 2003). ENSO is strong driver of modern interannual variability today over the Altiplano and northern Chile (Vuille and Keimig, 2004) and wet years ~ a years in this area are often concurrent with strong La Nin (Houston, 2006) indicative of a strong link between moisture levels in the SCA and tropical Pacific SST gradients. Several researchers have proposed high-latitude drivers in phase with events in the North Atlantic (for example, Heinrich Events), and propose that these exert a first-order control over Altiplano hydroclimate over the last 130 ka (Placzek et al., 2013; Martin et al., 2018) although not all paleolake events are coeval with Heinrich events (Placzek et al., 2013). As previously mentioned, almost all Atacama Desert records (except Laguna Miscanti) show wet anomalies coeval with the Tauca phase during CAPE I. Increased summer rainfall may have reached as far south as 30 S, in the Turbio and Encierro valleys (Aguilar, 2010; Riquelme et al., 2011). This would suggest that CAPE I was a probably the most extensive period of increased summer precipitation examined here, even at subtropical latitudes. Further south in CC, the pollen record from the Tagua Tagua lake core also suggests an increase in winter precipitation between 19.5 s et al., and 17 ka BP and attributed to the local LGM (Valero-Garce 2005). Indeed, deglaciation began in southern Chile at 17.8 ka BP (Palacios et al., 2020). This would imply that temperatures as well as rainfall increased throughout the region after the global LGM. Although most BA records suggest very wet conditions attributed to the Tauca phase, there is some evidence for increased ~ a event dated from 14.1 to 13.8 aridity at 14 ka BP, such as the Tican ka BP (Sylvestre et al., 1999). This event, however, was considered restricted to the Uyuni and Coipasa basins (Sylvestre et al., 1999; Placzek et al., 2006). Records form the Atacama Desert have shown that this arid event may have been considerably more widespread and could have impacted the height of the water table in places such as Salar de Punta Negra, from 13.8 to 12.7 ka BP (Quade et al., 2008) and Alto Varas from 14.5 to 12.2 ka BP (S aez et al., 2016). This arid event likely terminated CAPE I, and prolonged conditions like ~ o phenomenon (which today weaken those of a persistent El Nin the flow of easterly moisture across the Andes) have been invoked to explain its onset (Kienast et al., 2006; Makou et al., 2010). Most records in the Atacama (18 -27 S) and NWA (Guayatayoc) suggest positive moisture anomalies at the end of the CAPE I at 14 ka BP (Grosjean et al., 2001; Moreno et al., 2007; Gayo et al., 2012; Steinmann et al., 1904; Mujica et al., 2015; Pfeiffer et al., 2018). A14C-dated rodent midden record from Río Salado (22 S) shows the presence of arid plant communities with rainfall amounts similar to today at 14.2 ka BP (Latorre et al., 2006). In contrast, midden pollen from the Quebrada del Chaco record in the SA shows a mixed regime of both summer and winter rainfall increases from 17 to 14 ka BP (Maldonado et al., 2005). This positive anomaly also occurs in Semiarid Chile, where glacial advances occurred from 15 to 14 ka BP in the headwaters of the Encierro and Turbio valleys and have been attributed to increased summer rainfall (Zech et al., 2006; Aguilar, 2010; Riquelme et al., 2011). A colder and wetter climate is suggested by an increase in forest pollen taxa, associated with a stronger influence of the westerlies at Laguna Tagua Tagua in Central Chile, which shows colder and wetter climates between ~14 s et al., 2005). and 11.5 ka BP (Valero-Garce unknown (Betancourt and Saavedra, 2002). While limited spatially, these records can be collated across a large area (several basins-see lez-Pinilla et al., 2021) and are easily 14C-dated. This is very Gonza different from the lake records, which integrate climate from decadal to sub-millennial timescales across an entire basin and therefore show low-frequency variability (Grosjean et al., 2001, 2003). And there are other known limitations associated with lake records in the Andes, such as unknown and variable reservoir effects in the Chilean altiplano (Geyh et al., 1999; Grosjean et al., 2001). Clearly, more LGM records are needed from the Central Atacama Desert to resolve these issues using different geochronological techniques such as OSL and UeTh dating. SA records all show wetter LGM climates than today. Increased runoff and higher water tables resulting from precipitation increases have been proposed to explain the presence of more diverse plant communities in the hyperarid core of Atacama Desert (Díaz et al., 2012). Just as for the 32 ka BP interval, an increase in winter rainfall associated with a northward expansion of the westerlies likely occurred at least as far north as 25 S, as suggested by Maldonado et al. (2005). Indeed, increased presence of Nothofagus dombeyi-type pollen at Tagua Tagua during the LGM has attributed to a northward shift in the westerlies (e.g., Heusser, 1990). Cosmogenic ages on glacial moraines in the Cachapoal valley provide further evidence for wet conditions, as glaciers are mostly sensitive to precipitation at these latitudes (34-35 S, Zech et al., 2008; Herrera, 2016; Charrier et al., 2019). Overall, our maps show that records with positive moisture anomalies occur throughout the SCA at 17 ka BP, perhaps the wettest interval over the last 32 ka BP discussed here. Positive moisture anomalies are so widespread throughout the SCA at this time that it has been termed the CAPE (Central Andean Pluvial Event) (Latorre et al., 2006, Quade et al., 2008; Placzek et al., 2009; Gayo et al., 2012; Workman et al., 2020; Pfeiffer et al., 2018). The term “CAPE” was originally coined for the Atacama Desert by Latorre et al. (2006) as the “Central Atacama Pluvial Event” based on rodent middens that showed two distinctive pluvials at 17.5e16.2 ka BP and 11.7e9.5 ka BP interrupted by an arid event at 14.2 ka B P (see Fig. 7). Quade et al. (2008) and Placzek et al. (2009) expanded this term to “Central Andean Pluvial Event” based on paleowetland evidence from the Salar de Punta Negra basin (3070, m a.s.l, 24.5 S), and established two phases of increased available moisture at 15.9e13.8 ka BP and 12.7e9.7 ka BP that were found throughout the SCA between 18 and 27 S. Based on evidence for positive moisture anomalies from the northern Atacama, Gayo et al. (2012) and Pfeiffer et al. (2018) revised the CAPE chronology, which were divided into CAPE I (17.5e14.2 ka BP) and CAPE II (13.8e9.7 ka BP) separated by an arid period at 14.2e13.8 ka BP. More recent evidence based on mean annual rainfall anomalies derived from rodent body size changes show that in the CA, CAPE I and II occurred from 15.9 e 14.8 and 13.0e8.6 ka BP, respectively lez-Pinilla et al., 2021). (Gonza During CAPE I, paleolake Tauca spread to cover 60,000 km2 of the southern Bolivian Altiplano (Sylvestre et al., 1999; Baker et al., 2001; Rigsby et al., 2005; Blard et al., 2009; Placzek et al., 2006, 2013) between 18.1 and 14.1 ka, and shorelines formed ~140 m above the current surface of the Uyuni basin (Placzek et al., 2006, 2013). As previously mentioned, several explanations have been proposed for the formation of this and other paleolakes over the last 130 ka, including summer insolation and links to North Atlantic stadials (Baker et al., 2001; Rowe et al., 2002; Fritz et al., 2004; Rigsby et al., 2005). Changes in global temperature have also been proposed based on climate models (Blodgett et al., 1997; Garreaud et al., 2003) that show the impacts of warming contrasts between the northern and southern hemispheres during glacial periods. Such contrasts generate moisture anomalies that increase easterly 18 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 increased moisture during the Middle Holocene (Rech et al., 2002, 2003). Further evidence for a brief interlude of increased moisture in the Central Atacama is present in the Salar de Atacama salt core (Bobst et al., 2001). A pollen record from Pastos Chicos and the absence of organic pedogenic horizons in Antofagasta de la Sierra rivers also imply negative moisture anomalies in NWA at 6 ka BP (Tchilinguirian et al., 2014; Grana et al., 2016). Pulses of increased rainfall also occurred in these records (Grana et al., 2016; Morales, 2011). MidHolocene NWA aridity has been attributed to weakening of the South American low-level jet (SALLJ) since when strengthened, it would lead to an intensification of the South Atlantic convergence zone (SACZ) and favor the penetration of cold fronts with an improved convection area ahead in the exit region from SALLJ (bringing tropical humid air masses from the Amazon to southern Brazil and northern Argentina). The SALLJ mostly occurs during the warm season south of 20 S, whereas to the north it occurs throughout the year (Marengo et al., 2004; Vera et al., 2006). SC and CC also show arid climates in our 6 ka BP maps, except for a diatomite layer in the Tagua Tagua core (Fig. 9), which indicates s et al., 2005). As with the 9.5 present-day conditions (Valero-Garce ka BP interval, a southward displacement of the westerly storm tracks and the strengthening of the SPH associated with strong La ~ a-like conditions are commonly cited explanations (Maldonado Nin n, 2002, 2006; Carre et al., et al., 2005; Maldonado and Villagra 2012; Tiner et al., 2018). In contrast, CR records suggest wet conditions (Markgraf, 1983). These conditions could be associated with increased advection of moisture from the Atlantic (Hebe, 1997; Gil et al., 2005), whereas south of 33 S frontal systems decreased in frequency (Gil et al., 2005). Finally, our 4 ka BP map shows increases in moisture throughout the SCA. For instance, ice advanced from 4.7 to 3.3 ka BP at Nevado Sajama (Smith et al., 2009), even though the Sajama ice core shows increased aridity (Thompson et al., 1998). Differential responses across west versus east facing slopes may partly explain this (Smith et al., 2009). Positive moisture anomalies at 4 ka BP have been linked to increased ENSO activity throughout the SCA, which was more pronounced compared to the Middle Holocene (Sandweiss et al., 2001; Mix et al., 2001; Donders et al., 2008). Even so, ENSO variability decreased between 4.5 and 3.5 ka BP compared to its variability after 3.5 ka BP (Sandweiss et al., 2001; Mix et al., 2001; Donders et al., 2008). Another possible explanation for increased moisture compared to the 6 ka BP has been linked to increased solar irradiance, which in turn would drive increased activity of the SASM at least on millennial timescales (Novello et al., 2016; De Porras et al., 2017). Positive moisture anomalies also prevailed in SA and CC records n, at 4 ka BP (Veit, 1996; Jenny et al., 2002; Maldonado and Villagra 2006; Riquelme et al., 2011) associated with a weakening of the n, 2002, 2006; Maldonado et al., SPH (Maldonado and Villagra 2005). CMIP5/PMIP3 simulations show that during cold periods (such as during the European Little Ice Age) the SPH contracts, with expansion occurring during warmer periods (Flores-Aqueveque et al., 2020). This implies that global temperatures drove a weakening of the SPH and increased available moisture across the region at the onset of the Late Holocene (cold period) and its expansion with increased aridity during the Middle Holocene (warm period). Some paleorecords show arid conditions, however, and these have ~ a-like conditions from ~5 to 4 ka BP (Carre been linked to La Nin et al., 2012). Paleotemperatures estimated from the marine bivalve Mesodesma donacium d18O values show colder SSTs than present, associated with increased coastal upwelling and therefore an intensified SPH and strengthened Humboldt Current system BA records at 9.5 ka BP begin to show shifts towards increased aridity, which has been attributed to a summer insolation minimum at 10 ka BP (Rigsby et al., 2005) although this was not the most arid phase in the Bolivian Altiplano (which occurs during the Middle Holocene). NA records also indicate arid conditions, evidenced by decreases in the lake levels in the Chilean altiplano ca. 9.5 to 9 ka BP (Moreno et al., 2007; Baied and Wheeler, 1993). CA and SA records show widespread aridity, with the disappearance of Andean steppe taxa and the prevalence of prepuna species in rodent midden records at Cerros de Aiquina, Lomas de Tilocalar, n de Tuina, El Hotel- Paso Barros Arana and Quebrada del Cordo Chaco III (Latorre et al., 2003; 2003; Maldonado et al., 2005). This was mostly coeval with a decrease in groundwater levels along the río San Salvador, Salar de Punta Negra and in Alto Varas, around 9.8 ka BP (Quade et al., 2008; S aez et al., 2016; Tully et al., 2019), which has been attributed to the end of CAPE II (Quade et al., 2008; Gayo ez et al., 2016; Tully et al., 2019). et al., 2012; Sa The heterogeneity in CA proxies in relation to moisture anomalies and the end of CAPE events could reflect the temporal scale preserved in each record, which can vary from centuries to millennia. As previously discussed, lacustrine proxies (lake cores) integrate climate from decades to centuries and therefore show low-frequency variability (Grosjean et al., 2001, 2003). Groundwater tables also respond more slowly to onset of drought (c. 500 yrs, Grosjean et al., 2003; Pigati et al., 2014). In contrast, rodent middens likely represent much shorter timescales, although the length of a durational episode needs to be assessed on a midden-tomidden basis. Our 9.5 ka BP map shows that SC and CC climates were clearly drier than today further south (Jenny et al., 2002; Maldonado and n, 2002; Valero-Garce s et al., 2005; Zech et al., 2006; Villagra Maldonado et al., 2005; Ortega et al., 2012; Tiner et al., 2018) (Fig. 8). Explanations for this increase in aridity involve a southward shift of winter storm tracks entrained within the southern westerlies and a strengthening of the SPH (Jenny et al., 2002; n, 2002, 2006; Valero-Garce s et al., 2005; Maldonado and Villagra Maldonado et al., 2005; Tiner et al., 2018). The onset of strong La ~ a-type conditions between 13 and 8.6 ka BP could have also Nin increased regional aridity (Vargas et al., 2006; Ortega et al., 2012). Arid conditions also prevailed east of the Andes in CR, although aridity intensified here during the Middle Holocene and has been n, 1993; attributed to the strengthening of the SPH (Villagra Yacobaccio and Morales, 2005). In contrast, NWA records all suggest wet conditions associated with increased summer rainfall (Yacobaccio and Morales, 2005; Tchilinguirian et al., 2014; Grana pez et al., 2016), possibly linked to a CAPE-type phenomenon (Lo and Galli, 2015). On the other hand, these wetter climates may have been caused by ENSO-like conditions and sea surface temperature variability across the tropical Atlantic (Trauth et al., 2000, 2003). Our 6 ka BP map reveals that two-thirds of all records show strong negative moisture anomalies across the SCA (Baied and Wheeler, 1993; Grosjean et al., 1997a,b; Thompson et al., 1998; Grosjean et al., 2001; Rigsby et al., 2005; Placzek et al., 2009; Tully et al., 2019). Widespread aridity during the Middle Holocene has ~ a-like conditions (Koutavas been attributed to a prevalence of La Nin et al., 2012; Sandweiss et al., et al., 2002; Donders et al., 2008; Carre 2020). Nevertheless, a third of all the records show positive moisture anomalies during this interval. For example, increased moisture occurred from 6.5 to 5 ka BP at Laguna Miscanti, which have been attributed to centennial-scale moisture “pulses” (Grosjean et al., 2003). Paleowetlands formed in the Puripica, Tulan and Río Salado drainages at the same time, and are cited as evidence for 19 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 et al., 2003) whereas deeper lakes (Chungar a or Miscanti) will not reflect very high-frequency changes or specific events, and therefore mostly record long-term climatic trends (Vuille and Baumgartner, 1993; Grosjean et al., 2003). Furthermore, completely opposite interpretations by different authors often arise for the same record or locality. The fine-grained diatomites, black mats and other wetland deposits at Quebrada Puripica are a good example (Grosjean et al., 1997a,b; Rech et al., 2003). These authors propose different theoretical frameworks to interpret the same record. Grosjean et al. (1997) suggest that an increase in the size and frequency of discharge events results in increased erosion of the active channel during wet periods with fine-grained sediments deposited during arid phases. This is contrary to a base level model used by Rech et al. (2003), which interprets such periods of downcutting as arid phases. Such base level models have been applied successfully to interpret paleowetlands across the Atacama Desert (Rech et al., 2002; Rech et al., 2003; ez et al., 2016; Pfeiffer et al., 2018; Tully et al., Quade et al., 2008; Sa 2019; Workman et al., 2020). Dating uncertainties remain an important issue throughout the SCA. Chronologies of glacial advances and retreat are based mostly on cosmogenic dating techniques in which sample ages can vary significantly depending on the rate of cosmogenic production considered. For example, Zech et al. (2006) considers a production rate of 5.25 10Be Atoms a1 g (Desilet and Zedra, 2003) for the Encierro valley glacial features, whereas Aguilar (2010) uses a rate of 4.5 10Be atoms a1g (based on Blaco et al., 2008). Unknown and/ or variable reservoir effects are widely known issues for radiocarbon age-depth models in the altiplano lakes (Geyh et al., 1999; Moreno et al., 2007). Many of these issues have been resolved by UeTh dating of carbonates, which for the altiplano often show that samples are much older than the corresponding radiocarbon ages (Placzek et al., 2006). Indeed, most researchers recommend that radiocarbon ages on carbonates (e.g., stromatolites, bioherm, tufas, marls, etc.) in the SCA should be considered maximum ages (Geyh et al., 1999; Grosjean et al., 2001; Pfeiffer et al., 2018). Despite these many limitations, our maps reveal overall how different regions across the SCA responded to different drivers across the last glacial-interglacial cycle (Table 1). For example, records show increased moisture throughout the southern sector of the SCA (18 -34 S), while the high Andes (17 -27 S) remained dry et al., 2012). This agrees with explanations for the presence (Carre of negative moisture anomalies in other records, such as Laguna el Cepo (Tiner et al., 2018). Positive moisture anomalies also occur throughout the CR in Argentina (Markgraf, 1983; Navarro et al., 2010; Rojo et al., 2012), although these have been linked to increased advection of moisture from the Atlantic. Such advection today is strongest in September and remains until January (Hebe, 1997), whereas tropically sourced moisture (Amazon and Chaco basins) is predominant in summer. These factors can enhance each other and lead to higher rainfall in the summer (Hebe, 1997). Increased frequency of frontal systems of Pacific origin (winter rainfall) have also been cited to explain increased Late Holocene moisture as these would be linked to a n., 1993). weakening of the SPSH (Capitanelli, 1967; Villagra 5.2. Proxy sensitivity and spatial integration Our maps show important differences between regional and local records for any given time interval (Table 1). Such differences can arise due to multiple factors, such as spatial representation, proxy sensitivity, chronological uncertainties, and record temporal resolution (e.g., Grosjean et al., 2003). For example, records that represent entire watersheds (59), such as salt or lake cores including the Salar de Atacama, Uyuni-Coipasa basin, Lago and Laguna Miscanti are often (but not always) at odds Chungara with records that are more spatially restricted, such as rodent middens (34) (Sylvestre et al., 1999; Bobst et al., 2001; Fornari et al., 2001; Grosjean et al., 2001; Placzek et al., 2006; Moreno et al., 2007) (Latorre et al., 2003; 2003, 2006; Maldonado et al., 2005; Díaz et al., 2012; Mujica et al., 2015). As previously discussed, this difference in spatial representation is also accompanied by temporal differences as well, depending on the resolution of the record which can vary from decades to centuries. Paleosols and records of groundwater table variations (i.e., paleowetlands) have inherent lags associated with system response times and therefore respond very slowly to climatic variations (Veit, 1996; Grosjean et al., 2003; Pigati et al., 2014). Such lags have been tentatively quantified for groundwater systems in the Atacama, and these systems typically respond on the order of 500 years (Rech et al., 2016). Otherwise, the same type of proxy may respond differently, as in the case of large salt flats likely respond immediately to precipitation (Grosjean Table 1 Interregional comparison of paleorecords across the South-Central Andes for all time intervals. 20 H. Orellana, C. Latorre, J.-L. García et al. Quaternary Science Reviews 313 (2023) 108174 from Central Atacama to Central Chile (35 S), unlike the NWA. Window 6 ka BP shows an extended or very arid period on both sides of the Andes. Finally, at 4 ka, we see humid conditions in the Bolivian Altiplano, Central Atacama, Southern Atacama and Cuyo Region, while Northern Atacama and Central Chile, the conditions become similar to the current ones, except in the Argentine Northwest which has arid conditions. at 32 ka. Another example is at 4 ka BP, where NA and CC records indicate conditions similar to the present, while the other records show wet conditions along the SCA. 5.3. TRACE-21 model simulation The TRACE-21 model is forced by orbital and insolation changes as well as freshwater discharges into the North Atlantic, which directly affects Atlantic Meridional Overturning Circulation (AMOC) (Liu et al., 2009; Karger et al., 2021). This discharge can be associated with Heinrich events, such as Heinrich 1, which occurred just before the 17 ka window (17.5 ka). This time window was a wet period especially in the Altiplano and the elevated areas of the Atacama (>3000 m.a.s.l) (Fig. 11), mostly because ice discharge in the North Atlantic is linked to the intensification of the South American Monsoon and its southward displacement (Placzek et al., lez-Pinilla et al., 2013; Stríkis et al., 2018; Martin et al., 2018; Gonza 2021). This mechanism generates greater transport of moisture from the tropical Atlantic and a southward shift of the Intertropical Convergence Zone (Broccoli et al., 2006), which int turn leads to greater advection of moisture to the Andes (Garreaud et al., 2003). This coincides with almost all the records in that sector (17 ka-time window). On the other hand, since the model is strongly linked to the forcings that affect the northern hemisphere (AMOC) and these are strongly represented in the Late Pleistocene, models such as TRACE-21 or PIMP do a poor job of adequately simulating Holocene lez-Pinilla et al., 2021). Adding to this records (also see Gonza problem is the fact that the models are run at a global scale and downscaling becomes more complex. Author contribution statement All authors have made substantial contributions to this submission. This manuscript was based on the creation of both a database and a state-of-the-art review of the records in the south-central ctor OrelAndes, which were carried out by the lead author (He s). Claudio Latorre and Juan Luis García collaborated in lana Corte the interpretation of the proxies and discussion of the manuscript, respectively. Fabrice Lambert carried out the paleoclimatic modeling. Claudio Latorre secured funding. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Data availability The data that has been used is confidential. 6. Conclusions Acknowledgments The meta-analysis presented here of all published records from the South-Central Andes suggest how proxies used to reconstruct past climate change have different sensitivities to climatic variability and/or different geographic representativity (record is a local or regional representation of paleoclimatic conditions). Dating issues clearly can account for some of the discrepancies seen in our maps, especially between proxies from very similar areas, most notably in the Salar de Uyuni basin. These issues include problems variable reservoir effects in 14C-dated records or evolving parameter estimation with cosmogenic dating techniques. By aggregating different records with specific time intervals, our analyses may in fact compound these issues at the local scale (i.e. within a basin) but can also provide further insights into the spatial signals across a broader area, not only revealing overall regional climate responses but also how these shifts over time in intensity and direction (e.g., during the Middle and Late Holocene a drier Central Chile almost always correlates with wetter climates directly across the Andes in the Cuyo Region but not during the Late Pleistocene (in the 32e14 ka BP maps), when it was much wetter everywhere. Our maps based on specific temporal windows show that at 32 ka BP climate was more wetter than today in most of the SCA (22 35 S), except in the Desaguadero Valley and the Uyuni basin in the Bolivian Altiplano. In contrast, the 21 ka BP map shows wetter conditions in most of the Bolivian Altiplano, but other records from Northern Chile show drier climates than today. All LGM records from the Central Atacama show positive anomalies on the western side of the Andes, as opposed to the Cuyo Region in the eastern Andes. The 17 ka BP map shows very wet conditions throughout the SCA, as does the 14 ka BP map, although this presents some important exceptions to this trend, which are inferred at the sites of Quebrada Maní, Río Salado and in the Domeyko mountain range in Southern Atacama. At 9.5 ka BP, the Bolivian Altiplano and Northern Atacama show wet anomalies, which change more arid southward We thank ANID FONDECYT grants 1191568, 1201786 (Chile grants) for funding as well as ANID PIA grant FB210006 to the Institute of Ecology and Biodiversity. HO received an ANID Doctoral Fellowship used to complete this study. Additional funding was provided by ANID FSEQ210021 and Millennium Nucleus UPWELL (ANID NCN19_153) to CL. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.quascirev.2023.108174. 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