Reconstructing formation processes at the Canary Islands indigenous site of Belmaco Cave (La Palma, Spain) through a multiproxy geoarchaeological approach

Abstract

The indigenous populations of La Palma (Canary Islands), who arrived on the island from Northwest Africa ca. 2000 years B.P., were predominantly pastoralists. Yet, many aspects of their subsistence economy such as the procurement, management, and use of wild plant resources remain largely unknown. To explore this, we studied the 600–1100‐year‐old archaeological site of Belmaco Cave, which comprises a stratified sedimentary deposit representative of a fumier. Here, we present a high‐resolution, multiproxy geoarchaeological study combining soil micromorphology, lipid biomarker analysis, X‐ray diffraction, μ‐X‐ray diffraction, μ‐X‐ray fluorescence, Fourier transform infrared spectroscopy, and μ‐Fourier transform infrared spectroscopy, to characterize formation processes and explore plant sources. Recurrent goat/sheep habitation and maintenance activities are represented by interstratified layers of unburned dung, charcoal‐rich sediment, and dung ash. Lipid biomarker data show a herd diet mainly composed of herbaceous plants, which is key to understanding the mobility of indigenous shepherds. Our results also revealed an unusual suite of authigenic minerals including hazenite, aragonite, and sylvite, possibly formed through diagenetic processes involving interaction between ash, dung, urine, volcanogenic components, and bacterial activity, coupled with arid and alkaline conditions. Our study shows the potential of a multiproxy approach to a fumier deposit in a volcanogenic sedimentary context.

Carbonate precipitation and phosphate trapping by microbialite isolates from an alkaline insular lake (Bagno dell'Acqua, Pantelleria Island, Italy)

“…The formation of the hazenite mineral in Mono Lake, investigated by Yang et al ( 2014 ), has been linked to the metabolic activity of cyanobacteria of the genus Lyngbya and occurs in the presence of carbonates (Yang et al, 2011 ). Hazenite has been observed for the second time at the Belmaco Cave site (La Palma, Spain) (Fernández-Palacios et al, 2023 ). Although earlier studies have suggested that cultures containing the bacterial strain Virgibacillus sp can prompt the precipitation of an ammonium analog of hazenite, specifically (NH4)NaMg 2 (PO4) 2 ·14H 2 O (Yang et al, 2014 ), for as much as we know, this is the first report of hazenite synthesis with K and Na, mediated by heterotrophic bacteria under controlled laboratory conditions.…”

“…Recent studies define hazenite as the first struvite-type compound containing two structurally distinct monovalent cations (K and Na), indicating an exclusive role of the biological activity in the mineralization process (Yang et al, 2011 ). Hazenite has been observed for the second time at the Belmaco Cave site (La Palma, Spain) (Fernández-Palacios et al, 2023 ). To date, these two sites appear to be the only ones where this biomineral has been identified.…”