Browsing by Author "Quade, Jay"

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    Camelids in the hyperarid core of the Atacama desert 12,000-11,000 years ago? A stable isotope study and its consequences for early human settlement
    (2024) Ugalde, Paula C.; Gayo, Eugenia M.; Labarca, Rafael; Santoro, Calogero M.; Quade, Jay
    How did hunter-gatherers initially settle and move across extreme environments? We conducted a multi-disciplinary study to tackle this question, focusing on how Paleoindigenous populations inhabited the hyperarid core of the Atacama Desert. Particularly, we examined the stable isotopic values of similar to 12,000-11,200-year-old camelid and rodent bones and hair samples retrieved from low-elevation archaeological sites (Pampa del Tamarugal basin - PdT, 800-1200 masl). By integrating novel and existing data into a regional stable isotope ecology, we offer a baseline for interpreting our results. delta C-13 and delta N-15 values on archaeological remains show animals with different geographical origins. A first group includes camelids and rodents with lower delta N-15 values and delta C-13 values indicating a dominantly C-3 diet, corresponding to animals either local to the PdT or from the Andean Steppe, at least similar to 80 km away and between 4000 and 4500 masl. Most of these remains, however, come from residential sites and belong to young camelids, indicating a local origin. A second group presents a higher delta N-15 signal and delta C-13 values indicative of a mixed C-3-C-4 based diet. These animals were not local but source to the Puna at least similar to 60 km away between 3200 - 4000 masl. We hypothesize that the first would correspond to animals associated with hunter-gatherer bands settled around a wetland and grove environment in the PdT. The second group could correspond to remains brought by humans from the Puna to the PdT. Our results demonstrate that during the Late Pleistocene/Early Holocene the Atacama was very different than today, supporting life that included large and mid-size game. These results also show that the core of the Atacama attracted animals and people and counters the notion of this ecosystem as a barren passageway from the Andes to the coast.
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    Establishment and formation of fog-dependent Tillandsia landbeckii dunes in the Atacama Desert: Evidence from radiocarbon and stable isotopes
    (2011) Latorre, Claudio; Gonzalez, Angelica L.; Quade, Jay; Farina, Jose M.; Pinto, Raquel; Marquet, Pablo A.
    Extensive dune fields made up exclusively of the bromeliad Tillandsia landbeckii thrive in the Atacama Desert, one of the most extreme landscapes on earth. These plants survive by adapting exclusively to take in abundant advective fog and dew as moisture sources. Although some information has been gathered regarding their modern distribution and adaptations, very little is known about how these dune systems actually form and accumulate over time. We present evidence based on 20 radiocarbon dates for the establishment age and development of five different such dune systems located along a similar to 215 km transect in northern Chile. Using stratigraphy, geochronology and stable C and N isotopes, we (1) develop an establishment chronology of these ecosystems, (2) explain how the unique T. landbeckii dunes form, and (3) link changes in foliar delta N-15 values to moisture availability in buried fossil T. landbeckii layers. We conclude by pointing out the potential that these systems have for reconstructing past climate change along coastal northern Chile during the late Holocene.
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    High- and low-latitude forcings drive Atacama Desert rainfall variations over the past 16,000 years
    (2021) Gonzalez-Pinilla, Francisco J.; Latorre, Claudio; Rojas, Maisa; Houston, John; Ignacia Rocuant, M.; Maldonado, Antonio; Santoro, Calogero M.; Quade, Jay; Betancourt, Julio L.
    Late Quaternary precipitation dynamics in the central Andes have been linked to both high- and low-latitude atmospheric teleconnections. We use present-day relationships between fecal pellet diameters from ashy chinchilla rats (Abrocoma cinerea) and mean annual rainfall to reconstruct the timing and magnitude of pluvials (wet episodes) spanning the past 16,000 years in the Atacama Desert based on 81 C-14-dated A. cinerea paleomiddens. A transient climate simulation shows that pluvials identified at 15.9 to 14.8, 13.0 to 8.6, and 8.1 to 7.6 ka B.P. can be linked to North Atlantic (high-latitude) forcing (e. g., Heinrich Stadial 1, Younger Dryas, and Bond cold events). Holocene pluvials at 5.0 to 4.6, 3.2 to 2.1, and 1.4 to 0.7 ka B.P. are not simulated, implying low-latitude internal variability forcing (i.e., ENSO regime shifts). These results help constrain future central Andean hydroclimatic variability and hold promise for reconstructing past climates from rodent middens in desert ecosystems worldwide.
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    Mid-Holocene Climate in the South-Central Andes: Humid or Dry?
    (2001) Quade, Jay; Latorre H., Claudio
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    The first peoples of the Atacama Desert lived among the trees: A 11,600-to 11,200-year- old grove and congregation site
    (2024) Ugalde, Paula C.; Joly, Delphine; Latorre, Claudio; Gayo, Eugenia M.; Labarca, Rafael; Simunovic, Mikhaela; Mcrostie, Virginia; Holliday, Vance T.; Quade, Jay; Santoro, Calogero M.
    In deserts, water has been singled out as the most important factor for choosing where to settle, but trees were likely an important part of the landscape for hunter - gatherers beyond merely constituting an economic resource. Yet, this critical aspect has not been considered archaeologically. Here, we present the results of mapping and radiocarbon dating of a truly unique archaeological record. Over 150 preserved stumps around five Late Pleistocene/ Early Holocene archaeological campsites (12,800 to 11,200 cal BP) show that trees were key features in the creation of everyday habitats for the first inhabitants of the Atacama Desert. At two of these sites, QM12 and QM35, the spatial and chronological correlation between trees and hearths reveals that people located their homes under the tree canopy. At residential site QM35, artifact distribution coincides with a grove dated to - 11,600 to 11,200 cal BP. A third residential area (QM32) occurred along the grove margins - 12,000 to 11,200 cal BP. Based on the distinct cultural material of these two camps, we propose that two different groups intermittently shared this rich wetland - grove environment. The tree taxa suggest a preference for the native Schinus molle, a tree scarcely present on the landscape today, over the endemic, nitrogen - fixing Strombocarpa tamarugo , both for toolmaking and firewood and even though the S. tamarugo was locally more abundant. Together with the spatial and chronological coincidence of campsites, hearths, and trees, we propose that people spared the most abundant and resilient species to create their homes, in turn promoting fertility oases amid the Atacama's hyperaridity.
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    The structure and rate of late Miocene expansion of C4 plants
    (2007) Behrensmeyer, Anna K.; Quade, Jay; Cerling, Thure E.; Kappelman, John; Khan, Imran A.; Copeland, Peter; Roe, Lois; Hicks, Jason; Stubblefield, Phoebe; Willis, Brian J.; Latorre, Claudio
    This study uses stable isotope variation within individual Mio-Pliocene paleosols to investigate subkilometer-scale phytogeography of late Miocene vegetation change in southeast Asia between ca. 8.1 and 5 Ma, a time interval that coincides with dramatic global vegetation change. We examine trends through time in the distribution of low-latitude grasses (C-4 plants) and forest (C-3 plants) on Indo-Gangetic floodplains using carbon (delta C-13) and oxygen isotopic (delta C-18) values in buried soil carbonates in Siwalik Series sediments exposed in the Rohtas Anticline, north-central Pakistan. Revised, high-resolution magnetostratigraphy and a new 40Ar/39Ar date provide improved age control for the 2020 m Rohtas section. Carbon isotope results capture lateral variability of C-3 versus C-4 plants at five stratigraphic levels, R11 (8.0 Ma), R15 (6.74-6.78 Ma), R23 (5.78 Ma), R29 (4.8-4.9 Ma), and upper boundary tuff (UBT; 2.4 Ma), using detailed sampling of paleosols traceable laterally over hundreds of meters. Paleosols and the contained isotopic results can be assigned to three different depositional contexts within the fluvial sediments: channel fill, crevasse-splay, and floodplain environments. delta C-13 results show that near the beginning (8.0 Ma) and after (4.0 Ma) the period of major ecological change, vegetation was homogeneously C-3 or C-4, respectively, regardless of paleo-landscape position. In the intervening period, there is a wide range of values overall, with C-4 grasses first invading the drier portions of the system (floodplain surfaces) and C-3 plants persisting in moister settings, such as topographically lower channel swales. Although abrupt on a geologic timescale, changes in abundance of C-4 plants are modest (similar to 2% per 100,000 yr) compared to rates of vegetation turnover in response to glacial and interglacial climate changes in the Quaternary. Earlier research documented a sharply defined C-3 to C-4 transition in Pakistan between 8.1 and 5.0 Ma, based on vertical sampling, but this higher-resolution study reveals a more gradual transition between 8.0 and 4.5 Ma in which C-3 and C-4 plants occupied different subenvironments of the Siwalik alluvial plain. delta O-18 values as well as delta C-13 values of soil carbonate increase up section at Rohtas, similar to isotope trends in other paleosol records from the region. Spatially, however, there is no correlation between delta C-13 and delta O-18 values at most stratigraphic levels. This implies that the changes in soil hydrology brought about by the shift from forest to grassland (i.e., an increase in average soil evaporation) did not produce the shift through time in delta O-18 values. We interpret the trend toward heavier soil carbonate delta O-18 values as a response to changes in external climatic factors such as a net decrease in rainfall over the past 9 Ma.