The special location of Lake "Specchio di Venere" on Pantelleria Island in the Sicily Channel (Mediterranean Sea) between Tunisia and Sicily offers a unique terrestrial archive recording atmospheric changes, which are otherwise difficult to decipher in the marine records from this area. The lake is an endorheic saline basin with a maximum depth of 12.5 m. As the water input depends on rainfall, precipitation variations influence changes of the lake's water chemistry. In summer 2008, Lake Venere was cored with a modified Livingstone corer revealing a composite sedimentary sequence of 10.29 m length. Two radiocarbon dates form a preliminary age model indicating a very high sedimentation rate ~80 cm/100 years. Therefore, the recovered sequence allows the analysis of the last 1,200 years in high resolution. The sedimentology of the core alternates between intervals with carbonate laminations, and sections rich in organic matter with variable amount of detrital influence. The carbonate was likely precipitated during dry climatic periods, when the ratio evaporation/precipitation was high. Carbonate content is especially high in the lower part of the core between 800 and 950 years AD. The carbonate content stays low for about 3 centuries, before several intervals of intermediate carbonate content separated by nearly carbonate free sediment occur. In the last 130 years, the carbonate content increases. The carbonate curve closely follows the general European climate evolution of the last millennium. Intervals rich in carbonate in the lower part of the Venere core coincide with the medieval warm period (WMP), whereas during the little ice age (LIA) (1250 - 1850 years AD) little or no carbonates were deposited. Pollen analysis suggests vegetation responded to the climatic changes we inferred from litho-stratigraphical properties. During the period 800-1050 AD, drought and disturbance-adapted, evergreen-broadleaved trees (e.g. Olea, Q. ilex), shrubs (e.g. Pistacia), and heliophilous herbs (e.g. Artemisia) dominated the vegetation of the island, and conifers were moderately abundant (on average 20-30% of the pollen sum). Afterwards conifers (Pinus pinaster) expanded, while Olea, Q.ilex, and open environments declined. From 1800-2000 AD Quercus ilex and Olea re-expanded and conifers became less abundant. Today dense Pinus pinaster forests are restricted to higher altitudes of the island, where moisture is more abundant. The pronounced negative correlation between evergreen broadleaved and conifers is also registered at decadal scales, with rather strong and abrupt oscillations during and after the LIA period. However, vegetational changes were certainly co-determined by land-use, which was quite intense in the past, as also shown by widespread stone-terrace constructions for crop cultivation. This initial analysis shows the potential of the Lake Venere sedimentary record as a valuable climatic and environmental archive for the Central Mediterranean.
|Numero di pagine||1|
|Stato di pubblicazione||Published - 2011|