Oxygen-isotope records from Greenland ice cores 1,2 indicate numerous rapid climate¯uctuations during the last glacial period. North Atlantic marine sediment cores show comparable variability in sea surface temperature and the deposition of icerafted debris 3±5 . In contrast, very few continental records of this time period provide the temporal resolution and environmental sensitivity necessary to reveal the extent and effects of these environmental¯uctuations on the continents. Here we present high-resolution geochemical, physical and pollen data from lake sediments in Italy and from a Mediterranean sediment core, linked by a common tephrochronology. Our lacustrine sequence extends to the past 102,000 years. Many of its features correlate well with the Greenland ice-core records, demonstrating that the closely coupled ocean±atmosphere system of the Northern Hemisphere during the last glacial 4 extended its in¯uence at least as far as the central Mediterranean region. Numerous vegetation changes were rapid, frequently occurring in less than 200 years, showing that the terrestrial biosphere participated fully in lastglacial climate variability. Earlier than 65,000 years ago, our record shows more climate¯uctuations than are apparent in the Greenland ice cores. Together, the multi-proxy data from the continental and marine records reveal differences in the seasonal character of climate during successive interstadials, and provide a step towards determining the underlying mechanisms of the centennial±millennial-scale variability.A series of four sediment cores (B, D, J and L) obtained from Lago Grande di Monticchio (408 569 N, 158 359 E, 656 m above sea level), a maar lake in Basilicata, southern Italy, extends to a depth of 72.5 m. Sedimentation rates, estimated from annually laminated sections of a composite of these cores, provide a chronology 6,7 that gives a date of 101.7 kyr ago for the base of the record (Fig. 1). This calendaryear chronology, based solely upon Monticchio sedimentation rates, is independent of palynostratigraphic (that is, pollen-based), marine d 18 O event or ice-core interstadial correlations. It is complemented by a tephrochronology and a series of radioisotopic ages.

Pollen and plant macrofossil studies at 11 sites in New Jersey, southern and eastern Pennsylvania, West Virginia, and Virginia, USA reveal the character of the stable vegetation of the unglaciated eastern United States while the Wisconsin ice sheet was still at its outer limit. Grass—dominated tundra with dwarf shrubs was present 60 km south of the ice front at Longswamp, Pennsylvania. Sedge tundra covered the higher mountains of central Appalachia. In southern Pennsylvania, New Jersey (including the Pine Barrens), and northern Virginia, Picea (black or white spruce) was common, with Betula glandulosa (dwarf birch) and tall herbs, especially Sanguisorba canadensis (burnet). This is interpreted as forest tundra. In North and South Carolina and in northwest Georgia, forests of Picea and Pinus banksiana (jack pine) were present, with few deciduous trees. No site is yet known where broad—leaved trees formed the predominant vegetation cover anywhere on the Coastal Plain or in the Florida peninsula. With climatic warming, dwarf birch and spruce expanded into the tundra in unglaciated Pennsylvania. At Crider's Pond in southern Pennsylvania a Picea/Betula glandulosa assemblage with tall herbs was present from 15 000 to 13 000 yr BP. The associated aquatic flora was species poor. About 13 000 yr BP Abies balsamea (fir), Pinus banksiana, and Alnus cf. rugosa (speckled alder) invaded, together with diverse tree and shrub species, an assemblage like the southern boreal forest today. Betula populifolia (grey birch) occurs in this assemblage at Longswamp; there the aquatic flora is species rich. The increase in species diversity is evidence of marked climatic warming about 13 000 yr BP in southern and eastern Pennsylvania. Picea rubens (red spruce) arrived at Crider's Pond shortly before 11 500 yr BP, followed soon after by Pinus strobus (white pine). At Tannersville in glaciated eastern Pennsylvania an invasion series Picea—Abies—Pinus banksiana—Betula papyrifera (paper birch)—Larix laricina (tamarack)—Pinus strobus—Betula populifolia—Pinus rigida (pitch pine) can be demonstrated between 13 000 and 9000 yr BP. The stable flora of the periglacial region was different from the pioneer flora of the deglaciated area and from the vegetation of the modern tundra. As the ice withdrew, Tsuga (hemlock) and other tree species for which there is little or no fossil record at the height of the glaciation appeared in large populations in central Appalachia and the northern coastal plain, from which they invaded the deglaciated region at different rates. Castanea (chestnut), a slow migrant, took 5000 yr to reach southern New England from central Appalachia. Persistent tundra made the higher mountains of central Appalachia an important phytogeographical barrier to tree migration until about 12 500 yr BP. It explains differences in forest history west and east of the mountains. Tamarack seems to have migrated eastward from a glacial refuge south of the Great Lakes region. The distinctive modern vegetation of the Pine Barrens was assembled aft...

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