Geomorphological dynamic changes during the Holocene through ephemeral stream analyses from Northwest Argentina

Abstract

This paper studies the changes in the geomorphological dynamics recorded in 18 ephemeral streams located on the east side of Loma Pelada (Tafi Valley), a part of the Sierras Subandinas (Northwest Argentina). The applied methodology is based on photointerpretation, field survey, and descriptions of the Holocene alluvial fillings dated by tephras, archaeological artefacts, and absolute datings. The records show a coupled system of slope-terrace-alluvial fans resulting from the environmental changes of four alternating aggradation/degradation stages. The oldest stage (1) was generated by climatic causes and covers Early to Mid-Holocene (ca. 13,000–10,000BP to ca. 4200BP). After the incision of these accumulations, a new aggradation stage (2) was triggered by anthropogenic activity occurring from right before 2500BP to the 15th century. During that time human occupations of the Tafí Valley were intense. Two wetter events occurred around 4200 and 2800BP in the area, related to global cooling phases. Lastly, two more recent phases (3 and 4) are associated with the climatic variability of the LIA and the Present Warm Period. The results highlight the sensitivity of headwater catchments of dry subtropical mountainous areas to climate changes, anthropogenic impact, and their relationship with global climatic data.