Late Holocene landscape and climate evolution in the Sierra de Santa Victoria (NW Argentina, Jujuy) deduced from a high-Andean peat record

KARSTEN SCHITECK; ANNE NIEMEYER; FABIO F. FLORES; LILIANA C. LUPO

Mendoza

Conferencia; 4th Southern Deserts Conference; 2014

Laboratorio de Paleoecologia Humana. Universidad Nacional de Cuyo

High-Andean cushion peatlands are a valuable natural archive for palaeoenvironmental research. They have the quality to be very sensitive towards environmental changes and are well-suited for the application of a variety of methods that can be used for the reconstruction of palaeoclimates. The strengths of these geoarchives are their comparability over climatic gradients, their high accumulation rates and the high quality of their peat deposits to be precisely 14C-dated.   The study area lies at the northeastern margin of the arid diagonal of South America. For the reconstruction of Holocene environmental changes, a multi-proxy approach (pollen, fossil charcoal, fossil macroremains and geochemical analysis) was applied, based on extracted peat cores from a cushion peatland at 4400 m a.s.l. in the Eastern Cordillera of northwest Argentina (22° S, 65° W). The development of a pollen-vegetation dispersion model, which covers the principal phytogeographical provinces (High-Andean, Puna, Prepuna, Yungas, Chaco), is based on soil surface samples within latitudinal and altitudinal transects. The data permits the separation of representative regional, local and extralocal pollen spectra, featuring the interpretative value of ecological indicator species.   Fire has played an important role in the ecology of high-altitude Andean grassland vegetation during the past millennia. The macroscopical analysis of charred particles within the sedimentary records provided important information about changes in local past fire regimes, and hence, offered insights into reorganizations of climate and high-Andean vegetation. Prevailing cooler conditions in high-mountain areas result in a down-slope shift of vegetation belts, depending on the degree of temperature decrease and the duration and stability of the cold period.   The palaeoecologic data reflects several prominent Late Holocene climate anomalies and provides evidence that Northern Hemisphere temperature oscillations were extensive and, at the same time, affected the southward extension of moisture flux in the South American summer monsoon belt.