Geochemistry and Sedimentology of a Minerotrophic Peat in a Western Mediterranean Mountain Wilderness Area

Abstract

Sedimentological and biogeochemical measurements were conducted on minerotrophic peat in a wilderness area on a granitic plateau to reconstruct the local ecosystem’s history and clarify the peat’s response to local and global changes. The peat is less than 1900 years old. Its clay and iron (Fe) concentration profiles revealed an increasing atmospheric influx over time, whereas the levels of its nutrients (P, K, Ca, Mg) have increased since the 19th century. Additionally, changes in the relative abundance of amorphous aluminium indicated a gradual decrease in soil weathering. The dominant metallic trace elements were cadmium during the Roman epoch and early Middle Ages, then lead and mercury during the modern and the industrial eras. Unexpectedly, the peat proved to be sub-modern and lacks wildfire proxies, probably indicating an absence of nearby woodlands over the last 1900 years. Its concentrations of Ca and Mg indicate that airborne transport of particles released by soil erosion in lowland agricultural plains has strongly affected the peat’s composition since the 18th–19th century. The site has also been heavily influenced by metallic contamination due to regional metallurgy and agriculture, producing a peat that has been modified by social imprints over several centuries.