LATE WEICHSELIAN AND HOLOCENE SEDIMENT FLUXES OF THE NORTHERN NORTH-SEA MARGIN

An event chronology has been determined for temporal and lateral magni tudes of material fluxes across the northern North Sea Margin, includi ng the Norwegian Channel and the North Sea Fan. This has allowed the g overning factors for the sediment processes on the margin to be estima ted. The chronological model of selected cores is based on C-14 AMS da tes, regional tephra layers and planktonic foraminiferal stratigraphy. Based on this chronological framework the core sediments across the N orth Sea Margin have been divided into four main climatostratigraphic intervals: (a) Oldest Dryas (15-13 ka); Cb) Bolling-Allerod (13-11 ka) ; (c) Younger Dryas (11-10 ka); and (d) Holocene (10-0 ka). Further, t he Holocene period has also been divided into two subperiods, the Preb oreal (10-9 ka) and the Holocene interglacial (9-0 ka), creating five well-defined Lithological units (deposition phases), in all of which t he deglaciation units (15-9 ka) usually constitute 90% of the sediment budget. The recognition of an almost identical lithological successio n both in the records on the fan and in the high-resolution record of the channel suggests that sedimentation on the North Sea Margin must b e governed dominantly by regional sedimentary processes. For each time interval the sedimentation rate in the Norwegian Channel is, on avera ge, an order of magnitude higher than on the North Sea Fan diminishing distally from the shelf edge. Sedimentation under the Holocene interg lacial period (9-0 ka) contrasts totally from the deglaciation pattern , controlled dominantly by pelagic productivity in the area. Close to 50% of the hemipelagic sediments on the North Sea Margin are of Bollin g-Allerod age (15-13 ka). This extreme sedimentation resulted from a c ombination of a rapid sea-level rise, constantly exposing new areas fo r marine erosion/winnowing, and aggressive surface ocean current activ ity. Surface ocean currents and the associated bottom currents provide the dominant control on the pattern of deglacial sedimentation on the North Sea Margin (15-9 ka). This is especially apparent during the Ol dest Dryas and the Bolling-Allerod periods where the distribution patt ern across the margin is essentially hydrodynamically controlled. Only during the Younger Dryas period are the surface ocean processes overp rinted by sedimentary processes from melting icebergs. The high-resolu tion records reveal that the shifts in the lithological style of sedim entation are directly linked to the rapid reorganisation of the surfac e ocean system frequently taking place during the deglacial and Holoce ne time period, suggesting a fairly regional type of sedimentation pat tern. As the shift between the different lithological styles of sedime nts is both abrupt and regional, they should be detectable on the seis mic high-frequency records. (C) 1998 Elsevier Science B.V. All rights reserved.