Late quaternary pollen transport processes, western North Atlantic: Data from box models, cross-margin and N-S transects

Abstract

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