Stages of Climatic Change from Full Glacial to Holocene in Northwest Spain, Southern France and Italy: A Comparison of the Atlantic Coast and the Mediterranean Basin

Summary

From 17,000 to 11,000 years before present polar water retreated northward and westward in the North Atlantic. A brief readvance took place between 11,000 and 10,000 yr. B.P. It might be anticipated that the retreat of polar water would be reflected most strongly in the vegetation record on the Atlantic Coast of northwest Spain and less strongly in the Mediterranean region which is more distant from the climatic influence of the Atlantic. At Sanabria Marsh and Lago de Ajo in northwest Spain herb-dominated vegetation was present before 13,000 years ago. Ice in the cirque of Lago de Ajo had melted some time before 13,000 yr. B.P. and was not reconstituted. Subsequent vegetation history suggests that invasion of tree birches followed by pine and oak took place between 13,000 and 10,000 yr. B.P. There is no clear evidence for a Younger Dryas event in northwest Spain, but a regression of oak and temporary reappearance of birch and pine at Sanabria Marsh is datable to the early Holocene. Ocean cores from the Atlantic west of the Iberian Peninsula and in the Bay of Biscay appear to record a Younger Dryas event which may also be weakly recorded in the Pyrenees. More detailed comparison of the land and ocean records is required to resolve a possible conflict of evidence. In southern Italy at Lake Monticchio a full glacial herb-dominated vegetation is recorded. The transition to the Holocene is marked first by a peak of birch pollen and then by the presence of deciduous trees. Pine is insignificant in the developing vegetation at deglaciation. In southern Italy there is no evidence for climatic fluctuations during deglaciation.