CAMBIOS CLIMÁTICOS REGISTRADOS EN LOS SEDIMENTOS DE LAS LAGUNAS DE YALA, HOLOCENO-TARDÍO-ACTUAL, JUJUY, NO DE ARGENTINA.

MARÍA CAMACHO1, LILIANA LUPO2 Y MARTÍN GROSJEAN3

Córdoba

Congreso; III Congreso Argentino de Cuaternario y Geomorfología; 2006

Universidad Nacional de Córdoba, Fac. de Ciencias Exáctas, Físicas y Naturales. Escuela de Geología

The Yala Lakes (24º06’S / 65º29’W, 2100 m asl, northwestern Argentina) host a sedimentary sequence that records environmental changes in this area since the late Middle Holocene (3755 ± 150 14C yr B.P.) up until the Present. 210Pb, 137Cs and 14C dated sediments of two late Holocene landslide lakes in the Provincial Park Lagunas de Yala (Laguna Rodeo, Laguna Comedero) reveal a high-resolution multi-proxy data set of climate change for the past ca. 2000 years. Comparison of the lake sediment data set for the 20th century show that: 1) the lake sediment data set is internally highly consistent and compares well with independent data sets; 2) the regional increase in precipitation from 1960-1970 onwards is recorded in an increase in the (MARs) sediment mass accumulation rates (L. Rodeo from 100 to 390 mg cm-2 yr-1) and in an increase in fern spores reflecting wet vegetation. The tentative paleoclimatic reconstruction is based on facies analysis (climate as a function of the lake level, i.e. P-E) and elemental ratios of Sr/Ca, Ba/Ca and Mg/Ca ratios (as a semi-quantitative proxy-indicator for temperature and salinity). It is suggested that lake levels were higher between 690 and 580 cm depth (i.e. more humid roughly between 400 to 600 AD), low lake levels (dry around 700 AD), slightly lower than today (slightly more arid between 800 and ca 1500 AD), and modern from ca 1600 AD onwards with distinct dry intervals of unknown duration during the last 400 years.