Lithostratigraphy, Geochronology and Early Humans: The evolution of Quaternary volcanic successions and their impact on archaeological sites in the north-western edge of the Ararat Depression, Armenia

Abstract

This paper explores the geological context of Dalarik-1 Cave, located in the Mastarahegheghat River Gorge within the Aragats Volcanic Province (AVP) in Armenia. By integrating lithostratigraphy, geochronology, and geomorphology, we examine the processes that shaped the cave and its associated terrace sequence, establishing chronological constraints on the cave's bedrock and its development within the broader fluvial landscape. Volcanic rocks in the studied area exhibit geochemical evidence suggesting a subduction-modified mantle source, potentially influenced by slab-derived fluids or melts. Geochronological data from ⁴⁰Ar/³⁹Ar dating indicate that volcanic activity in the study area occurred between approximately 900 and 660 ka, encompassing the first and second AVP eruption stages. The formation of the cave is linked to river incision that followed the deposition of the youngest volcanic unit of the local plateau, dated to 656.6 ± 40.0 ka. This incision is associated with the development of four fluvial terraces (T1 to T4), with the lower terraces (T3 and T4) dated between ∼35 and 9 ka, reflecting intervals of climatic variability and/or tectonic activity. The cave is interpreted to have formed during a relatively stable phase of river activity, coinciding with the formation of the T2 terrace. It developed through both chemical and mechanical erosion within the volcanic bedrock. Based on these relationships, the formation of the cave likely occurred after the incision of the gorge (post-656.6 ± 40.0 ka) and prior to the deposition of the T3 terrace, dated by optically stimulated luminescence (OSL) to 32.5 ± 2.3 ka. The cave site of Dalarik-1 contains Lower Paleolithic artifacts indicating human occupation after the cave's formation and provides rare insights into early human activities in the region. The study of the regional landscape evolution and the interplay between volcanic, fluvial, and climatic processes contributes to the broader understanding of the cave formation mechanisms in volcanic landscapes, offering valuable insights for future studies of Paleolithic sites in the Armenian Highlands.