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The Younger Dryas (YD) impact hypothesis posits that fragments of a large, disintegrating asteroid/comet struck North America, South America, Europe, and western Asia ~12,800 years ago. Multiple airbursts/impacts produced the YD boundary layer (YDB), depositing peak concentrations of platinum, high-temperature spherules, meltglass, and nanodiamonds, forming an isochronous datum at >50 sites across ~50 million km² of Earth’s surface. This proposed event triggered extensive biomass burning, brief impact winter, YD climate change, and contributed to extinctions of late Pleistocene megafauna. In the most extensive investigation south of the equator, we report on a ~12,800-year-old sequence at Pilauco, Chile (~40°S), that exhibits peak YD boundary concentrations of platinum, gold, high-temperature iron- and chromium-rich spherules, and native iron particles rarely found in nature. A major peak in charcoal abundance marks an intense biomass-burning episode, synchronous with dramatic changes in vegetation, including a high-disturbance regime, seasonality in precipitation, and warmer conditions. This is anti-phased with northern-hemispheric cooling at the YD onset, whose rapidity suggests atmospheric linkage. The sudden disappearance of megafaunal remains and dung fungi in the YDB layer at Pilauco correlates with megafaunal extinctions across the Americas. The Pilauco record appears consistent with YDB impact evidence found at sites on four continents.

The site Los Notros, located just 60 m west of the site Pilauco in Osorno (Chile), was discovered in 2008, with excavations beginning in April 2016. The geology of Los Notros is similar to that of the Pilauco site where strata LN-1 and LN-2 are equivalent to layers PB-7 and PB-8 from Pilauco. However, Los Notros includes an additional stratum (LN-3) of prominent black color, finer texture, and similar age as the discordance between PB-8/PB-9, whereas layer LN-4 is equivalent to PB-9. Additionally, a chronostratigraphic relationship between both sites is suggested based on concordant radiocarbon ages. Excavations at the Los Notros have provided 15 fossil specimens from layers LN-1 and LN-2, 11 of which were taxonomically determined at least up to order level. A rich dental record represents the families Equidae, Gomphotheriidae, and Cervidae, whereas a nearly complete gomphothere tusk lacking torsion and enamel strips allowed its assignment to Notiomastodon platensis. Thus, the presence of N. platensis in northern Patagonia—the southern limit of the species range—is confirmed together with the identification of Equus (A.) sp., and the extension of the distributional range for the extinct genus Antifer from Cervidae.

Pilauco shows two distinct layers containing remains of Pleistocene mammals (PB-7 and PB-8). The site is spatially divided into two sectors, East (45 m2) and West (27 m2). The current study is centered in the Western sector, where the majority of the materials come from layer PB-7 (%NISP = 92.5). Overall, this layer does not show signs of weathering, exhibiting instead trampling marks, and in a lesser quantity, large carnivore tooth marks. The fragmentation level is low, particularly for the fossils of Gomphotheriidae, for which most of the fractures occurred when the fossils were not fresh. No human marks of any kind were identified. The impact of these distinct factors in the formation of the record of PB-7 was evaluated using the available data and concluded in an in situ death of a gomphothere, to which would have been added anatomical elements of other taxa, redeposited coluvially and/or through vertical migration as a result of trampling. Carnivores would have been primarily responsible for the alteration and possibly subtraction of skeletal remains; as of now there is no evidence of human impact in this process. The materials recovered in PB-8 layer could also have been deposited by colluvial processes, although the sample is very small to discuss the taphonomic processes that have occurred in this layer.

Rallidae, which includes coots, crakes and moorhens, is one of the most speciose families among the Gruiformes. This family exhibits a pattern of diversification that has involved significant episodes of regional expansion and speciation resulting in the presence of members of this group in every continent with the exception of Antarctica. In this work, we describe the diversity of fossil rallids from late Pleistocene-early Holocene deposits of the Laguna de Tagua Tagua Formation located in central Chile. We report the presence of the extant taxa, Fulica armillata, Fulica rufifrons, Fulica cf. F. rufifrons, Fulica cf. F. ardesiaca and Pardirallus sanguinolentus, and also identify a large new extinct coot, Fulica montanei sp. nov. represented by three left tarsometatarsi. Fulica montanei corresponds to the first extinct rallid recorded in the Quaternary of South America. The most remarkable feature of the tarsometatarsus of Fulica montanei is their large size, which falls in the range of the extant Andean species Fulica cornuta and the extinct Fulica prisca from New Zealand. An autapomorphic combination of characters observed in the tarsometatarsi also supports the erection of a new species. These rails coexisted with extinct megafauna, as well as small and medium-sized vertebrates and, presumably, with humans, constituting a faunal assemblage with no analogous today. Fulica montanei probably became extinct during the late Pleistocene-early Holocene.

The Laguna de Tagua Tagua has yielded two important late Pleistocene archaeological sites, Taguatagua 1 and Taguatagua 2, in which a clear early human exploitation of megafauna has been recorded. Particularly in Taguatagua 1 (TT-1), here re-dated around 12,600 cal yr BP, an abundant small faunal assemblage was also recovered, which had not been previously studied in detail. Here we report the first comprehensive taxonomic and taphonomic analysis of this site. We identified 28 different taxa, including mollusks, fish, anurans, reptiles, birds, marsupials, rodents, carnivores, gomphotheres, horses and cervids, making this the richest late Pleistocene site in Chile so far. Among these, sixteen taxa are new for the Chilean late Pleistocene. Birds are the richest group, with ten taxa, followed by rodents with eight taxa. Most of the species currently inhabit the area, but we identified some locally extirpated taxa, together with extinct taxa (exclusively megamammals). Taphonomic analysis suggests a very complex depositional scenario, mostly related to lake-level oscillations which covered and exposed a mainly natural deposited small faunal assemblage. So far, we detected human-made modifications exclusively in horse and cervid bones. Current habitat requirements of the extant fauna, as well as dietary reconstruction of extinct fauna, suggest a highly variable climate and vegetation during the formation of TT-1 since taxa with preferences from semiarid to humid/wooded environments were identified. These results can be related to the changes from cold/wet to dry/warm conditions documented during the Pleistocene - Holocene transition.

The archaeo-paleontological site of Pilauco (southern Chile) has one of the richest Late Pleistocene mammal records of the northern Chilean Patagonia, with at least nine forms dominated by gomphothere remains. This site has a complex taphonomic history due to postdepositional processes that affected the integrity, frequency, and distribution of the fossil bones. One of these processes is the action of large carnivores, indicated by tooth marks recorded exclusively in gomphothere bones. In this paper, we describe Gomphotheriidae fossil remains and give a detailed description of carnivore tooth marks detected in the sample. The absence of diagnostic fossil specimens does not allow genus or species assignment. The type, location, intensity, and dimensions of the tooth marks are compatible at least with a large felid, which probably scavenged a partially exposed carcass. The record of this taphonomic feature is important in order to understand the postdepositacional history of the Pilauco site, in which natural and cultural agents are involved.

Paleontological and archaeological sites have frequently been found in open locations of the Intermediate Depression of south-central Chile. This paper presents the results of two field sampling seasons carried out at the Pilauco Site (ca. 39°S) and compares them with those of three well known sites in Chile: Quereo, Tagua-Tagua and Monte Verde, ca. 32°, 34° and 41°S, respectively. Stratigraphic data collected at Pilauco and the resulting radiocarbon age model suggest that before 12,540 ± 90 BP the old Damas River eroded an older volcaniclastic hill, which was followed by a bog formation in an ox-bow lake. The site was developing up to 11,004 ± 186 BP, the date of the youngest vertebrate fossil. Two younger peat beds seal the site. As in Tagua-Tagua and Monte Verde, Gomphotheres are the most represented megafauna. Fossils of Equidae, Camelidae, Cervidae, Mephitidae, Muridae, Myocastoridae and Xenarthra are also found in Pilauco. As a whole, 718 bones, 30 teeth and 11 coprolites represent the extinct and extant vertebrates. Preliminary taphonomic results suggest action of various agents in the bones, i.e. trampling, root etching, abrasion, and carnivore gnawing. The spatial analysis suggests the transfer of smaller anatomical units (e.g. bones of camelids and horses) and the rearrangement of some pieces comparatively large (e.g. gomphothere bones). Similar to the present day north Patagonian landscape, the area where Pilauco site is located had a variety of animal resources, plants and stones in an ecotone between hills, floodplains and wetlands. A total of 101 lithics were recorded: basalt and quartzite were collected from nearby fluvial deposits and dacitic obsidian from the local volcaniclastic deposits. Debitage is the most represented lithic item (75%); cores and marginal edge-trimmed artifacts represented 12 and 13%, respectively. Artifacts and flakes are spatially and temporality associated in the same PB-7 bed with high bone concentrations in some specific areas, between 361 and 424 cm of local altitude. This industry is characterized by a recurrent lithic expedite technology with production of flakes and chips which mastered marginal retouches over the bifacial trimming. This seems to be connected to strategic conditions of high resource diversity, especially of human groups with a high or medium mobility across land. Pilauco represents a site contemporaneous to Monte Verde related as well to the first human occupation in the southern cone of South America, but with higher mammal diversity.

El presente trabajo discute el estatus taxonomico de la especie Antifer niemeyeri Casamiquela, 1984, definida a partir de astas completas procedentes de la laguna Taguatagua y la quebrada de Quereo (Pleistoceno tardio-Holoceno temprano), en Chile central (30-35°S). Se concluye, a partir de un estudio morfologico y morfometrico detallado, que Antifer niemeyeri debe ser considerado sinonimo de Antifer ultra Ameghino, 1889 dados los caracteres anatomicos compartidos con esta especie. Los resultados amplian la distribucion geografica del taxon, que previamente se registraba en Argentina, Uruguay y sur de Brasil, y confirman su biocron para el Pleistoceno tardio-Holoceno temprano (edad Lujanense), aun cuando las fechas radiocarbonicas de Chile central (ca. 9.900 anos 14C AP) corresponden a las mas tardias para la especie. A la luz de la evidencia paleoclimatica disponible, se vincula A. ultra durante el Pleistoceno de Chile central a ambientes calidos y abiertos. Considerando estos requerimientos, se discute su posible via de ingreso al actual territorio chileno a traves de corredores ubicados hacia el sur del macizo andino, y su coexistencia con Hippocamelus bisulcus Molina, 1782. De acuerdo a la informacion estratigrafica y paleoambiental, se postula que ambas especies habrian sido alopatridas, por lo menos en el area de estudio.

Newly described outcrops, excavations and sediment cores from the region of Ultima Esperanza, Magallanes, contain tephra derived from the large late-glacial explosive R1 eruption of the Reclus volcano in the Andean Austral Volcanic Zone. New radiocarbon dates associated to these deposits refine previous estimates of the age, to 14.9 cal kyrs BP (12,670±240 14C yrs BP), and volume, to >5 km3, of this tephra. The geographic and stratigraphic distribution of R1 also place constraints on the evolution of the ice-dammed proglacial lake that existed east of the cordillera in this area between the termination of the Last Glacial Maximum (LGM) and the Holocene. This proglacial lake generated wavecut terraces, and also caves, such as the Cueva de Milodon, along the highest prominent terrace. The current elevation of these terraces depends on the total amount of post-glacial isostatic rebound, which is unknown. Due to differential rebound, the highest prominent lake terraces decrease in height from west-to-east, from ~170 m a.s.l. on Peninsula Antonio Varas west of Seno Ultima Esperanza, to ~150 m a.s.l. around Lago Sofia, and down to ~125 m a.s.l. along their easternmost margin. The presence of thick deposits of R1 tephra in some of the caves around Lago Sofia implies that the proglacial lake had already dropped below its highest level prior to the time of this eruption, and, in fact, even earlier, prior to 16.1 cal kyrs BP (13,560±180 14C yrs BP), when land mammals first occupied these caves. The depositional environment of R1 in a core from Dumestre bog suggests that the lake level was in fact 70 m a.s.l. until 12.8 cal kyrs BP (10,695±40 14C yrs BP). However, a 14.2 cal kyrs BP (12,125±85 14C yrs BP) Mylodon pelvis from a nearby site, located at only ~7 m a.s.l., suggests that the lake could have emptied, for at least a brief period, to this low level at this time. This latter datum, combined with the lack of any prominent terraces between the highest ones (170-125 m a.s.l.) and much lower ones (at only 30 m a.s.l. on Peninsula Antonio Varas and 20 m a.s.l. along the coast north and south of Puerto Natales), suggests abrupt changes in the lake level after the R1 eruption. The likely mechanism for producing these changes in Ultima Esperanza was the catastrophic failure and subsequent re-sealing of an ice dam in Paso Kirke, the only below sea-level pathway west to the Pacific north of Fjordo Obstruccion. The final stage of lake drainage, from the lower terrace level (20-30 m a.s.l.) occurred at 10.3 cal kyrs BP.