Revisiting the Holocene tephrochronology of northwestern Argentina: Insights from geochemical characterization of the tephras from the Tafí valley

Abstract

In the southernmost sector of the Central Volcanic Zone (CVZ), spanning from 23° to 28°S, there is an estimated count of 30–40 potentially active volcanoes. Due to its remote location, the primary volcanic threat in this area during explosive eruptions is the dispersal and fallout of tephra. Among various approaches, tephrochronological studies have proven to be the most effective in compiling a comprehensive record of recent explosive eruptions in this region. The intermontane valleys nestled at the eastern foothills of the Andes, situated around 200–300 km from the volcanic arc, harbor a Holocene stratigraphic record containing multiple layers of tephra. These layers are evidence of the recurrence of substantial volcanic eruptions (VEI ≥4) during recent times, particularly within the last 10,000 years. Improving the tephrochronological knowledge of the southernmost edge of the CVZ constitutes a crucial initial step in evaluating the ash-fall hazard of this region. In this context, the Tafí valley emerges as a prominent candidate for serving as a dependable tephrochronological “anchor point” for regional correlations. Its strength lies in its conspicuous record of Holocene tephras and its well-documented morpho-stratigraphic setting, which has been rigorously constrained by absolute age dating. Despite these advantages, some of the Holocene tephras found within Tafí valley remain uncharacterized in terms of both glass shard and mineral geochemistry. This limitation has consequently hindered their utility in facilitating regional correlations. Thus, we present the glass shard and mineral composition of these uncharacterized Holocene tephras previously identified within Tafí valley. Our findings have not only enhanced regional correlations beyond the Tafí valley but have also provided more precise source constraints. Ultimately, our work represents an upgrade of the Holocene tephrochronological framework of Northwestern Argentina and a stride toward a more reliable assessment of volcanic hazard and risk within the region.