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Paleoclimate of the subtropical Andes during the latest Miocene, Lauca Basin, Chile

Texto completo
Feitl, Melina [1] ; Kern, Andrea K. [2] ; Jones, Amanda [1] ; Fritz, Sherilyn C. [3] ; Baker, Paul A. [4] ; Joeckel, R. M. [5, 6] ; Salenbien, Wout [4] ; Willard, Debra [7]
Número total de Autores: 8
Afiliação do(s) autor(es):
[1] Univ Nebraska, Dept Earth & Atmospher Sci, Lincoln, NE 68588 - USA
[2] Univ Sao Paulo, Dept Sedimentary & Environm Geol, Sao Paulo, SP - Brazil
[3] Univ Nebraska, Sch Biol Sci, Dept Earth & Atmospher Sci, Lincoln, NE 68588 - USA
[4] Duke Univ, Div Earth & Ocean Sci, Durham, NC 27708 - USA
[5] Univ Nebraska, Dept Earth & Atmospher Sci, Sch Nat Resources, Conservat & Survey Div, Lincoln, NE 68588 - USA
[6] Univ Nebraska, State Museum, Lincoln, NE 68588 - USA
[7] USGS, Climate Res & Dev, Reston, VA 20192 - USA
Número total de Afiliações: 7
Tipo de documento: Artigo Científico
Citações Web of Science: 0

Uplift of the Andean Cordillera during the Miocene and Pliocene produced large-scale changes in regional atmospheric circulation that impacted local ecosystems. The Lauca Basin (northern Chilean Altiplano) contains variably fluvial and lacustrine sedimentary sequences spanning the interval from 8.7 to 2.3 Ma. Field samples were collected from paleo-lacustrine sediments in the basin. Sediments were dated using detrital zircon geochronology on volcanic tuffs, yielding an age range between similar to 5.57 and 5.44 Ma. These new age constraints provided an opportunity to evaluate changes in the Lauca Basin ecosystem across this dynamic Miocene-Pliocene transition. We employed multiple proxies (lithofacies analysis, diatoms, pollen, and oxygen stable isotopes of authigenic carbonates) to interpret ancient lacustrine and terrestrial paleoenvironments. Alternations among mudstone, carbonate, and evaporitic facies indicate lake-level variability through time. The diatom assemblage is characterized by meso- to hypersaline and alkaline-tolerant taxa typical of shallow lakes. The delta O-18 values ranged from -8.96 to -2.22 parts per thousand indicating fluctuations in water balance. Pollen taxa in the outcrop are typical of a transitional stage between seasonal cloud forest and open grassland. Together, these proxies indicate that the Lauca paleolake sediments were deposited under a wetter-than-modem climate with high temporal variability. Our results refine previous studies in the Lauca Basin and are consistent with other regional studies suggesting that the South American summer monsoon at the Miocene-Pliocene transition was more intense than it is at present. (AU)

Processo FAPESP: 12/50260-6 - Estruturação e evolução da biota amazônica e seu ambiente: uma abordagem integrativa
Beneficiário:Lúcia Garcez Lohmann
Linha de fomento: Auxílio à Pesquisa - Programa BIOTA - Temático
Processo FAPESP: 14/05582-0 - Estruturação e evolução da biota amazônica e seu ambiente: paleobotânica e palinologia da Bacia Amazônica
Beneficiário:Andrea Kern
Linha de fomento: Bolsas no Brasil - Pós-Doutorado