Marine palynology: potentials for onshore—offshore correlation of Pleistocene—Holocene records

Abstract

A review of marine pollen-spore distributions reveals regional variations in primary transport pathways. Fluvial transport prevails on the mountainous margins of the eastern Pacific and off maj,or river deltas, including Arctic estuaries. Elsewhere, wind and sea ice are the main transport agents, and pollen concentration corresponds to dust influx. Redeposition of Quaternary palynomorphs is also important near emergent continental ice sheet centres where fine-grained sediment is being eroded. Pre-Quaternary palynomorphs can indicate sources of ice-rafted debris. Preservation and transport of pollen in marine sediments is not well understood. Laboratory processing with acetolysis shows damage of bisaccate grains, and copepod feeding experiments show some pollen damage of grains within the faecal pellet membranes.A multi-box model shows the relative importance of rivers, wind and ocean currents in pollen transport to shelves of Atlantic Canada: most pollen is wind-transported, but large storms may indirectly increase influx. In the Arctic, sea ice scouring and sediment transport are important in addition to northeasterly winds. These glacial processes would impact a third of the planet during glaciations. Pleistocene cores from NW Atlantic and Pacific Oceans show that glacial stage transport differed from that during Holocene and other interglacials because glacioeustatic lowstands exposed the continental shelves, and wind strength and direction changed following ice sheet growth. Pollen influxes and ice-volume records show variable leads and lags of palaeometerological events at glacialhnterglacial boundaries, with a major decline in terrigenous organics after -0.4 Ma (MIS 13-11).

Climate variability and long-term expansion of peatlands in Arctic Norway during the late Pliocene (ODP Site 642, Norwegian Sea)

“…Both fossil pollen grains are generally overrepresented in marine sediments. This effect becomes more pronounced with increasing distance from the shore due to their preferential transportation over long distances (see, e.g., Heusser, 1983;Mudie and McCarthy, 2006). Nevertheless, percentages of Pinus pollen generally reflect its relative proportion in the vegetation community, and proportions of Sphagnum spores are highest where extensive peatlands are found onshore (see, e.g., Heusser, 1983;Mudie and McCarthy, 1994;Mudie, 1982).…”

“…Nevertheless, percentages of Pinus pollen generally reflect its relative proportion in the vegetation community, and proportions of Sphagnum spores are highest where extensive peatlands are found onshore (see, e.g., Heusser, 1983;Mudie and McCarthy, 1994;Mudie, 1982). In contrast, pollen from deciduous trees is underrepresented in marine sediments as this pollen is deposited closer to the source area (< 200 km), as a result of their small size and high density (Mudie and McCarthy, 2006). With ODP Hole 642B being located ∼ 400 km offshore, the contrast between the relative abundance of Pinus and deciduous tree pollen is especially pronounced.…”

River inflow and salinity changes in the Caspian Sea during the last 5500 years

“…Most of the pollen grains are windtransported from a large area around the CS (Hooghiemstra et al, 2006;Mudie and McCarthy, 2006). To identify more clearly where from the windtransported pollen originated, present-day meteorological data have been used (Fig.…”

L’étude du pollen des séquences sédimentaires marines pour la compréhension du climat : l’exemple des périodes chaudes passées

“…Le pollen produit par la végétation du proche continent arrive à l'océan par les vents et les fleuves. Il est alors ingéré par les organismes planctoniques et par ce biais intégré dans des pelotes fécales, ou bien aggloméré avec les argiles (Mudie & McCarthy, 2006). Grâce à ces processus, la flottabilité du pollen diminue et il est peu influencé par les courants océaniques.…”