Hidden archives in the cave: sediments, bat guano, and prehistoric footprints at the ponte di Veja complex (Verona, Italy)

Abstract

Cave A at Ponte di Veja (Verona, Italy) preserves a stratified record that links sediment dynamics, chemical alteration and Late-Pleistocene hunter-gatherer activity on the southern Alpine foreland. Integrated sedimentological, micromorphological, mineralogical and geochemical analyses show that the lowermost unit is an allochthonous loess- and soil-derived deposit emplaced at the Last Glacial Maximum by slow percolation from the karst plateau and later modified under hydromorphic conditions. It is overlain by a paleosol, whose abundant charcoal, organic matter and faunal signals indicate repeated human and large-mammal presence in addition to bat guano input. Uneven guano accumulation drives strong in-situ acidification, leaching of alkaline-earth elements and precipitation of taranakite in the wetter, more acidic cave sector, while carbonate buffering keeps isolated spots near neutral. The data support a four-stage depositional model. Quiet loess infill before the Bølling–Allerød interstadial, post-glacial runoff erosion, re-occupation by humans and bats during the Bølling–Allerød and Holocene, and mid-20th-century removal of much guano-charcoal sediment for fertiliser. Radiocarbon and anthracological evidence reveal Epigravettian exploitation that intensified with interstadial warming, contracted, but likely did not cease, during the Younger Dryas, and resumed under Holocene thermophilous woodland.