Last Interglacial palaeovegetation, palaeoenvironments and chronology: a new record from Lago Grande di Monticchio, southern Italy

The sediments of Lago Grande di Monticchio, southern Italy, extend continuously from the present back to the penultimate glacial stage and have an independent lamination-based chronology of high precision and accuracy. Results are presented here from a detailed palynological investigation of that part of the sediment sequence that extends from the last millennia of the penultimate glacial stage to the first stadial following the Last Interglacial (LI). Quantitative palaeovegetation and palaeoclimate reconstructions made from the palynological data are also presented. The onset of the LI is dated to 127.20 ka BP, a date that is consistent with other recent estimates; the duration of the LI is estimated to have been 17.70 ka. The palaeovegetation record indicates a transition period of 3.35 ka at the end of the penultimate glacial stage prior to the onset of the LI; no Younger Dryas-like oscillation is recorded, although the transition was interrupted by a brief event, lasting ca 250 years, during which pollen of woody taxa was reduced in abundance. Steppe vegetation dominated during the latter part of the penultimate full-glacial stage, but was replaced progressively by wooded steppe during the transition. Although the development of forest cover marked the onset of the LI, the forests were relatively open or discontinuous during the first 2.65 ka, closing progressively thereafter and generally dominating between 123.00 and 109.50 ka BP. The end of the LI is dated to 109.50 ka BP, after which date forest cover became discontinuous and wooded steppe or steppe dominated during the 1.90 ka of the subsequent stadial. As might be expected, given the location of the lake, the composition of the LI forests differs markedly from those recorded from northern Europe, as well as from those recorded at other localities in southern Europe. The palaeoclimate reconstructions reveal complex changes in seasonality, the maximum coldest month mean temperatures being between 125.70 ka BP and 123.00 ka BP, whereas maxima for both annual temperature sum and the ratio of actual to potential evapotranspiration were between 120.60 ka BP and 115.80 ka BP. Reconstructed zonal mean values for all three climatic variables in the zones in which they peak exceed values at the locality today. Comparison with other palaeovegetation records of the LI from Europe reveals that forest cover generally opened up north of the Alpine region probably ca 115 ka BP, coinciding with a marked decrease in sea surface temperatures in the Nordic Seas; this probably corresponds to a marked shift in forest composition at Lago Grande di Monticchio at 115.80 ka BP with an associated reconstructed decrease of ca 5 °C in coldest month mean temperature. Nonetheless, forest continued to dominate at Lago Grande di Monticchio until 109.50 ka BP. Such comparisons also reveal considerable complexity in the geographical and altitudinal patterns of change in palaeovegetation during the LI; such complexity is to be expected given the parallel complexity of Holocene changes. Systematic comparisons between reconstructions of palaeoclimate are hampered by a lack of consistency in approach and in the variables reconstructed. Further insight into this complexity of palaeoclimate development during the LI requires a synthesis of the available data and application of a consistent reconstruction approach that also provides robust estimates of the uncertainty in the reconstructed values.