LATE QUATERNARY POLLEN TRANSPORT PROCESSES, WESTERN NORTH-ATLANTIC - DATA FROM BOX MODELS, CROSS-MARGIN AND N-S TRANSECTS

Surface pollen assemblages in coastal and neritic sediments of the wes tern North Atlantic compare well with eastern North American vegetatio n zones, and late Quaternary pollen in marginal marine sediments clear ly correlate with changes in terrestrial vegetation and paleoclimates. In contrast, offshore assemblages are strongly affected by differenti al adaptation of pollen to long distance transport by wind and water. Marine pollen transport processes were studied by measuring air and wa ter inputs to a coast-shelf box model, and by study of surface samples from cross-margin transects in three different climatic and oceanogra phic regions at approximately 38-degrees, 45-degrees and 55-degrees-N latitude. The box model shows that aerial transport is the main proces s by which pollen moves across the continental margin off Nova Scotia. Two clear seabed distribution patterns were found: Betula, Quercus, a nd herb pollen decrease rapidly offshore in abundance (grains per cubi c centimetre) and in relative abundance (percentage); Pinus and Picea have abundance peaks on the continental margin, but percentages increa se further offshore. Distributions of the main pollen and spore taxa w ere compared for late Wisconsinan glacial (oxygen isotopic stage 2, 12 -28 ka), terminal Pleistocene (10-12 ka) and Holocene sediments at 5 c ontinental margin and 3 deep-sea sites. The largest changes were found in percentages of Pinus, Picea, and herb pollen during the late Wisco nsinan glacial and terminal Pleistocene intervals at subpolar latitude s. These data can be related to shifts in paleo-vegetation, -winds and -hydrology that accompany global climate change.