SciELO - Scientific Electronic Library Online

 
vol.35 número1Tasas de denudación de largo tiempo en los Andes Centrales, Chile, estimadas a partir de un modelo digital de elevación usando la función 'Top Hat' por cierre y la interpolación ponderada por el inverso de la distancia: implicancias del clima Neógeno del Desierto de AtacamaEdad triásica de la Formación Pular de ambiente continental, Sierra de Almeida, Antofagasta, Norte de Chile índice de autoresíndice de materiabúsqueda de artículos
Home Pagelista alfabética de revistas  

Revista geológica de Chile

versión impresa ISSN 0716-0208

Resumen

MORATA, Diego et al. Geochronology of the Lower Cretaceous volcanism from the Coastal Range (29°20'-30°S), Chile. Rev. geol. Chile [online]. 2008, vol.35, n.1, pp. 123-145. ISSN 0716-0208.  http://dx.doi.org/10.4067/S0716-02082008000100006.

40Ar/39Ar age data (laser and furnace step heating) on plagioclase from Lower Cretaceous volcanic sequences from the Arqueros Formation in two sections of the Coastal Range at the latitude of La Serena (=29°S) have been obtained. Due to the partial alteration of plagioclase crystals, disturbed age spectra in the furnace experiments have been observed, whereas laser heating determinations involving a much smaller quantity of grains carefully selected, could display plateau ages corresponding to pure plagioclase, as demonstrated by a constant 37Ar/39ArK ratio. Plateau ages of 114.1±0.5 Ma (sample ARQ99-4), 111.3±0.9 Ma (sample TC99-5a), and 91.0±0.6 Ma (sample TC99-2) were found in lava flows, and 84.3±1.3 Ma on a dyke (sample ARQ99-7). These new 40Ar/39Ar ages, together with those previously published in central Chile, allow a constriction of the extensional magmatism during the Early Cretaceous in the Coastal Range of central and north-central Chile. All these data are in accordance with a long lived Early Cretaceous Magmatic Province (119-84 Ma), that could have started with a brief and huge magmatic event, mostly developed in the central part of the Coastal Range, followed by discrete magmatic pulses at further northern latitudes

Palabras clave : 40Ar/39Ar dating; Plagioclase; Lower Cretaceous; Volcanism; Coastal Range; Chile.

        · resumen en Español     · texto en Inglés     · pdf en Inglés