Late Holocene environmental changes from fluvio-aeolian morpho-sedimentary sequences (Santa Maria Valley, northwest Argentina)

The Santa Maria valley is located in the northern sector of the Sierras Pampeanas in Northwest Argentina. In spite of its arid characteristics, it was a densely populated area during the Pre-hispanic period. The populations developed an agropastoral economy, taking advantage of the wetter epochs that characterized some periods. The study of fluvio-aeolian records of the El Paso and Cafayate areas yielded interesting data for regional paleoenvironmental reconstruction. Geomorphological maps, field surveys, and archaeological digs were complemented with the detailed stratigraphic record of several points, together with radiocarbon and OSL dating. Alternating wetter and drier periods were inferred for the last 2,800 years. The wetter phases generated enough stability to allow soil formation and a better plant cover, thus favouring human settlements. For the paleoenvironmental interpretation, well defined European chronozones were used because there are no South American denominations. Within the sequence, some wetter periods stand out, such as the one between 2,800-2,500 Be the intermediate Roman Period (80-280 AD), and the LALIA (Late Antique Little Ice Age) (536-660 AD), while the drier phases comprise the Roman Epoch and the Medieval Climate Anomaly. Moreover, dune active phases during the last millennium were determined for 1,000, 1,350, 1,650, and 1,770 AD approximately, separated by wetter periods recorded by the presence of a paleosoil (15th century) and historical data (17th and 18th centuries).