Tracing holocene paleoenvironmental changes along the northern Tyrrhenian coast (Cornia and Pecora coastal plains, Tuscany, Italy): data from geochemical and sedimentological proxies

Abstract

In this paper, sedimentological and geochemical data from six cores are presented and discussed in order to better understand the Holocene palaeoenvironmental evolution of the coastal plains of the Pecora and Cornia Rivers (southern Tuscany, Italy). Overall, the stratigraphies show a general upward trend in the evolution of the sedimentary succession of lagoonal environments (low Zr/Rb, high EC values) connected or partially connected to the sea (low EC values), to a seaward progradation of marshy-swampy environments (Mn/Ti, high TOC values) and finally to continental environments with the progradation of distal alluvial plains (high Zr/Rb, low EC values) influenced by runoff phenomena or local water stagnation. This trend is closely related to the increasing input of sediments from inland due to soil erosion processes and, especially in the last two centuries, land reclamation works. In the Cornia coastal plain, the chronologies indicate that lagoonal environments were already present before ca. 8.2ka BC and started receding seaward at around 3.7ka BC. On the other hand, chronologies from ca. 0.5ka BC to ca. 0.6ka AD point to a persistence of lagoonal environments only in areas very close to those already identified as such in historical cartography. In the Pecora coastal plain, the chronologies show that the lagoon environments had already disappeared before ca. 3.3ka BC, whilst the peripheral environments were characterised by abundant vegetation. The latter gradually degraded in favour of the development of shallow to very deep, unvegetated marshlands, which persisted until ca. 1ka AD.