The late Pleistocene and Holocene in the Lourdes Basin, Western Pyrénées, France: new pollen analytical and chronological data

In the Lourdes Basin, pollen analytical results and 41 14C dates from three sites (four profiles, 538 spectra) have enabled a coherent biostratigraphy to be established from the last Pleniglacial to the present. The end of the Würm Pleniglacial is characterised by a long phase dominated by Poaceae that extended from ca. 20 000 to ca. 15 000 B.P. Another phase with Poaceae, in the context of a treeless environment, is recorded during the late-glacial between the Juniperus optimum (ca. 13 000 B.P.) and the Betula optimum (after ca. 12 500 B.P.). A marked decline in Betula and a rise in Artemisia values suggest a significant cooling of the climate during the Younger Dryas, an event which is now clearly recorded at several sites in southern Europe. The beginning of the Holocene is characterized by the minor role of Pinus and the early arrival of Quercus which achieves an absolute maximum before the arrival of Ulmus and Corylus. A critical assessment of previously published data is made in the light of these new results.