Hydrological Variability In Chilean Altiplano Lakes during the Last Millennia

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A multi-dating approach to age-modelling long continental records: The 135 ka El Cañizar de Villarquemado sequence (NE Spain)

We present the multidisciplinary dating approach - including radiocarbon, Uranium/Thorium series (U/Th), paleomagnetism, single-grain Optical Stimulated Luminescence (OSL), Infrared Stimulated Luminescence (IRSL) and tephrochronology - used for the development of an age model for the Cañizar de Villarquemado sequence (VIL) for the last ca. 135 ka. We describe the protocols used for each technique and discuss the positive and negative results, as well as their implications for interpreting the VIL sequence and for dating similar terrestrial records. In spite of the negative results of some techniques, particularly due to the absence of adequate sample material or inaccurate analytical precision, the multi-technique strategy employed here is essential to maximize the chances of obtaining robust age models in terrestrial sequences. The final Bayesian age model for VIL sequence includes 16 AMS 14C ages, 9 OSL ages and 5 previously published IRSL ages, and the accuracy and resolution of the model are improved by incorporating information related to changes in accumulation rate, as revealed by detailed sedimentological analyses. The main paleohydrological and vegetation changes in the sequence are coherent with global Marine Isotope Stage (MIS) 6 to 1 transitions since the penultimate Termination, although some regional idiosyncrasies are evident, such as higher moisture variability than expected, an abrupt inception of the last glacial cycle and a resilient response of vegetation in Mediterranean continental Iberia in both Terminations

Volcanism and climate change as drivers in Holocene depositional dynamic of Laguna del Maule (Andes of central Chile – 36° S)

Late Quaternary volcanic basins are active landscapes from which detailed archives of past climate and seismic and volcanic activity can be obtained. A multidisciplinary study performed on a transect of sediment cores was used to reconstruct the depositional evolution of the high-elevation Laguna del Maule (LdM) (36∘ S, 2180 m a.s.l., Chilean Andes). The recovered 5 m composite sediment sequence includes two thick turbidite units (LT1 and LT2) and numerous tephra layers (23 ash and 6 lapilli). We produced an age model based on nine new 14C AMS dates, existing 210Pb and 137Cs data, and the Quizapú ash horizon (1932 CE). According to this age model, the relatively drier Early Holocene was followed by a phase of increased productivity during the mid-Holocene and higher lake levels after 4.0 ka cal BP. Major hydroclimate transitions occurred at ca. 11, 8.0, 4.0 and 0.5 ka cal BP. Decreased summer insolation and winter precipitation due to a southward shift in the southern westerly winds and a strengthened Pacific Subtropical High could explain Early Holocene lower lake levels. Increased biological productivity during the mid-Holocene (∼8.0 to 6.0 ka cal BP) is coeval with a warm–dry phase described for much of southern South America. Periods of higher lake productivity are synchronous to a higher frequency of volcanic events. During the Late Holocene, the tephra layers show compositional changes suggesting a transition from silica-rich to silica-poor magmas at around 4.0 ka cal BP. This transition was synchronous with increased variability of sedimentary facies and geochemical proxies, indicating higher lake levels and increased moisture at LdM after 4.0 ka cal BP, most likely caused by the inception of current El Niño–Southern Oscillation and Pacific Decadal Oscillation (ENSO–PDO) dynamics in central Chile.Postprin

Receding ice drove parallel expansions in Southern Ocean penguins

International audienceClimate shifts are key drivers of ecosystem change. Despite the critical importance of Antarctica and the Southern Ocean for global climate, the extent of climate-driven ecological change in this region remains controversial. In particular, the biological effects of changing sea ice conditions are poorly understood. We hypothesize that rapid postglacial reductions in sea ice drove biological shifts across multiple widespread Southern Ocean species. We test for demographic shifts driven by climate events over recent millennia by analyzing population genomic datasets spanning 3 penguin genera ( Eudyptes , Pygoscelis , and Aptenodytes ). Demographic analyses for multiple species (macaroni/royal, eastern rockhopper, Adélie, gentoo, king, and emperor) currently inhabiting southern coastlines affected by heavy sea ice conditions during the Last Glacial Maximum (LGM) yielded genetic signatures of near-simultaneous population expansions associated with postglacial warming. Populations of the ice-adapted emperor penguin are inferred to have expanded slightly earlier than those of species requiring ice-free terrain. These concerted high-latitude expansion events contrast with relatively stable or declining demographic histories inferred for 4 penguin species (northern rockhopper, western rockhopper, Fiordland crested, and Snares crested) that apparently persisted throughout the LGM in ice-free habitats. Limited genetic structure detected in all ice-affected species across the vast Southern Ocean may reflect both rapid postglacial colonization of subantarctic and Antarctic shores, in addition to recent genetic exchange among populations. Together, these analyses highlight dramatic, ecosystem-wide responses to past Southern Ocean climate change and suggest potential for further shifts as warming continues

Contrasting phylogeographic pattern among Eudyptes penguins around the Southern Ocean

Since at least the middle-Miocene, the Antarctic Polar Front (APF) and the Subtropical Front (STF) appear to have been the main drivers of diversification of marine biota in the Southern Ocean. However, highly migratory marine birds and mammals challenge this paradigm and the importance of oceanographic barriers. Eudyptes penguins range from the Antarctic Peninsula to subantarctic islands and some of the southernmost subtropical islands. Because of recent diversification, the number of species remains uncertain. Here we analyze two mtDNA (HVRI, COI) and two nuclear (ODC, AK1) markers from 13 locations of five putative Eudyptes species: rockhopper (E. filholi, E. chrysocome, and E. moseleyi), macaroni (E. chrysolophus) and royal penguins (E. schlegeli). Our results show a strong phylogeographic structure among rockhopper penguins from South America, subantarctic and subtropical islands supporting the recognition of three separated species of rockhopper penguins. Although genetic divergence was neither observed among macaroni penguins from the Antarctic Peninsula and sub-Antarctic islands nor between macaroni and royal penguins, population genetic analyses revealed population genetic structure in both cases. We suggest that the APF and STF can act as barriers for these species. While the geographic distance between colonies might play a role, their impact/incidence on gene flow may vary between species and colonies

Aproximaciones Paleoambientales a la problemática de cambio climático en zonas áridas y semiaridas de Chile

19 páginas. Presentación elaborada para las II Jornadas IPErinas, celebradas el 12 de diciembre de 2013.Peer reviewe

A 7000-year high-resolution lake sediment record from coastal central Chile (Lago Vichuquén, 34°S): Implications for past sea level and environmental variability

Frugone-Alvarez, M. et. al.We present a 7-ka environmental reconstruction based on sedimentological and geochemical data from Lago Vichuquén, a coastal eutrophic lake in central Chile (34°48'S, 72°03' W, 4m a.s.l.). A relatively shallow and restricted marine environment with low productivity, high detrital input and dominant anoxic conditions in the Vichuquén Basin occurred from 7.0 to 6.5cal ka BP. Rapid onset of a Holocene marine transgression at 6.5cal ka BP favoured deeper and more biologically productive environments that existed until 2.8 cal ka BP. Bioproductivity changes during the mid-Holocene (6.5-4.2cal ka BP) were related to upwelling dynamics controlled by the intensity of the South-east Pacific Anticyclone (SPA). Periods with lower organic productivity and dominant anoxic conditions reflect an increased intensity of SPA (increased upwelling) and decreased precipitation. A shift at ∼4.0cal ka BP reflects the onset of modern Southern Westerly Winds and El Niño-Southern Oscillation patterns. Tectonic uplifting and geormorphological activity (dune advancement) are possible reasons behind the Vichuquén Basin closure at ∼1.2cal ka BP, leading to a low bioproductivity lacustrine environment which has developed until the present. © 2017 John Wiley & Sons, Ltd.This is a contribution of the HOLOCHILL project (CGL2012-32501). Additional funding was provided by the Laboratorio Internacional de Cambio Global (LINCGlobal PUC-CSIC). We thank R. Lopez, E. Royo, C. Alcaino, Escutia C. and A. Salabarnada for help with sample analysis; H. Orellana, Fernando, P. Tarrats and A. L Herrera for their help and logistical support in the field. C.L. acknowledges support from the IEB (grants ICM P05-002 and PFB23) and grants FONDECYT 1150763 and ICM NC120066. A.M. acknowledges support from grant FONDECYT 1140837. J.P-M.was funded by a BasqueGovernment postdoctoral fellowship (No. Ref. POS_2015_1_0006).Peer reviewe

A 700-year record of climate and environmental change from a high Andean lake: Laguna del Maule, central Chile (36°S)

Central Chile is heavily exploited for mineral and water resources, with agriculture and large urban populations all creating intensive landscape use. Few records of past environmental and climate change are available that afford a broader context. To aid in this assessment, we present a 700-year reconstruction from Laguna del Maule (LdM) in the high Andes of central Chile based on sedimentological, geochemical, diatom and pollen analyses. The age model is based on 210Pb/137Cs and 14C dating tied into known volcanic eruptions. Sedimentology consists of organic-rich sediments and diatom oozes with several interspersed volcanic-rich facies and two tephra deposits. Sediment geochemistry exhibits increased productivity (high Br/Ti, biosilica) and more dominant oxic conditions (high Fe/Mn) from AD 1300 to 1400 and from AD 1650 to 1850, likely during periods of relatively lower lake levels and better development of littoral environments. However, during this later period, high elevation vegetation was dominant, indicative of regional cooler/wetter conditions. In contrast, sediments deposited from AD 1850 to 1930 evidence decreased productivity and increased anoxic lake bottom conditions. The ‘Little Ice Age’ (LIA) in LdM is characterized by significant variations in lake dynamics and hydrology with cooler/wetter conditions (AD 1570–1700), major environmental changes in the 18th century and ending at ca. AD 1850. LdM record documents the impact of the LIA in the southern hemisphere and stresses the global nature of this climate period. Large changes in lake dynamics and diatoms assemblages during the 20th century could be related to anthropogenic impacts, but recent changes in climate patterns cannot be excluded. © The Author(s) 2015We thank A.L. Herrera for help with diatom samples, H. Orellana, F. Barreiro Lostres, F.P. Díaz and L. Torres (the “Alcalde de Mar” at Laguna del Maule) for their help and logistical support in the field; M. Soto-Herrera (SEM Lab.), N. Serrano (Dirección de Obras Hidráulicas) and P. Zavala (curator, PUC) for technical help. This work was supported by FONDECYT (Chile) [Grant No. 3120012], the Ministry of Economy and Competitiveness (Spain) [Grant No. CGL2012-32501] to HOLOCHILL and the Institute of Ecology and Biodiversity (Chile) through [grants ICM P05-002 and PFB-23].Peer Reviewe