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

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 highresolution, multiproxy geoarchaeological study combining soil micromorphology, lipid biomarker analysis, X-ray diffraction, mu-X-ray diffraction, mu-X-ray fluorescence, Fourier transform infrared spectroscopy, and mu-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.

Automated summary

This study conducted a high-resolution, multiproxy geoarchaeological study on the archaeological site of Belmaco Cave, revealing the activities of sheep herding and the plant diet of ancient people. The research found that the ancient people mainly fed on herbaceous plants and discovered some rare minerals. This multiproxy approach shows the potential for studying fumier deposits in a volcanogenic sedimentary context.