Early to middle Holocene environmental variations in the Gobero basin.

Palynological and geological studies carried out at Gobero allowed to reconstruct the main palaeoenvironmental and climatic changes that occurred in the early and middle Holocene. The geological data of the area surrounding the perilacustrine ar- chaeological sites showed that four aeolian (arid) sedimentary units (from the earliest to the latest aeolian unit, a.u. 2, 3, 4 and 5) alternated with four lacustrine (wet) sedimentary units (lacustrine units, l.u. 3, 4, 5 and 6). The earliest Holocene lacustrine unit, l.u. 3, dated 10,000–8160 cal BP, represents the time when the Gobero lake reached its maximum expansion and depth. The pollen data showed a complex environmental scenario including xerophilous and hygrophilous plant associations. The floristic changes and the lacustrine units in the Gobero basin match the general wet and dry climate oscillations. The early Holocene humid phase was interrupted by a dry spell ca 8200 BP. Then, a major dry phase, which was also evident in many other lake records, took place at, or just after, 6000 BP with a shift towards more permanent aridity. Nevertheless, the persistence of well-developed wet environments, even in the most recent l.u. 6 (ca 3800 cal BP), suggested that a grassland-type of vegetation continued to develop during late Holocene wet oscillations, following the increase of a lacustrine level.