Coupled natural and human induced environmental history during the Holocene in Utica (Tunisia): Lipid biomarkers and metal pollution

The coastal palaeoenvironmental conditions of Utica ancient gulf area during the Holocene were reconstructed after a multidisciplinary study to identify natural variations and the influence of anthropic processes in the environmental evolution of this coastal area. For this purpose, a ca. 15 m-deep sedimentary core formerly drilled in the surroundings were studied. Amino acid racemization in ostracode valves and previously published radiocarbon ( 14 C) datings of plant debris and charcoal were used for constructing the chronological scale using a bayesian age-model. Based on the sedimentological characteristics, lipid biomarkers and trace elements quantification both natural and anthropogenic variations were identified. The results reveal a chronological period ranging between the present and 8200 cal yr BP, in which marine and continental inputs occurred marking variations in the palaeoenvironmental conditions, being able to differentiate 2 units each one with 3 subunits (A1–A3; B1–B3). The human influence since the Chalcolithic, being noticeable during Phoenician and Roman times was also observed in the geological record. Lead, copper, zinc and silver concentrations along the sedimentary record revealed that the influence of anthropogenic factors predominated over lithogenic processes in the last three millennia, particularly linked to mining activities in the area especially in Phoenician times, with an important decrease after the conquest by Romans. In addition, the presence of faecal stanols, such as coprostanol, revealed the presence of human populations in the area since ca. 4200 cal yr BP, before the city of Utica was founded.