The Neogene stratigraphy of the glaciated European margin from Lofoten to Porcupine
WP1 - NORTH SEA-FAN-VØRING
The high-resolution stratigraphy of the Mid-Norwegian continental margin has been divided into a northern and southern region comprising the Vøring margin and the North Sea–Møre margin, respectively. A number of middle–upper Pleistocene seismic-stratigraphic units have been identified (Fig. 24a); these are described in detail elsewhere (Hjelstuen et al. 2002). These units have been deposited in response to the fluctuating glacial–interglacial climatic regime which prevailed in the Northern Hemisphere during the Pleistocene. The most recent significant input of sediment was associated with the Last Glacial Maximum in the late Weichselian, marine oxygen isotope stage (MIS) 2 (Mangerud et al. 1996; Sejrup et al. 2000; Dahlgren 2002) (Fig. 24e).
On both the Vøring and North Sea–Møre margins, the seismic-stratigraphic units display a variable acoustic response ranging from transparent to well stratified, and commonly have a lobate form (Fig. 24b, Fig. 24c and Fig. 24d). On the North Sea–Møre margin, the major prograding wedge of the North Sea Fan has been severely dissected and eroded by sliding associated with the Storegga Slide Complex (Fig. 24d: see distribution map). Consequently, the seismic correlation along this part of the continental margin remains poorly defined due to the large area affected by mass movements. Seismic correlation is also inhibited in the upper slope–shelfbreak region, which has been subjected to repeated glacial erosion. Nevertheless, a provisional correlation of the seismic-stratigraphic units to MIS 1–14 has been established on the basis of a number of commercial geotechnical borings, DSDP and ODP sites (Fig. 24e: see distribution map). These sample sites also provide lithological information for calibration with the seismic-stratigraphic units.
Glacigenic units — The glacigenic units identified are generally characterized as acoustically homogeneous and show large variations in thickness and distribution along the margin (Fig. 24b and Fig. 24c). Sediment samples reveal that these units are composed of diamicton and muddy sand with gravel and pebbles (Dahlgren 2002; Haflidason et al. 1998). The glacigenic sediments that have been dated by seismic correlation to shallow cores and geotechnical borings on the margin were deposited when Fennoscandia and the adjacent continental shelf were covered by extensive ice-sheets (Dahlgren 2002; Hjelstuen et al. 2002).
Hemipelagic units — The hemipelagic units display a well-layered, parallel, medium-to-high-amplitude reflection pattern, as well as an acoustically transparent configuration (Hjelstuen et al. 2002). The boundaries of the units are commonly defined by continuous, medium-to-high-amplitude reflections. During the deposition of these units, the southernmost part of the Vøring Margin was the main depocentre.
Sediment drifts — Two contourite sediment drifts, the Nyk and Lofoten drifts, have been identified (Laberg et al. 1999; Laberg et al. 2002) (see distribution map). A continuously layered, parallel to slightly divergent internal reflection pattern characterizes both drifts. The drifts have a muddy composition (Laberg et al. In press). Whereas the Lofoten Drift is a result of increased ocean circulation from the Miocene to the present day, the Nyk Drift has been developed from northeastward flowing surface and intermediate water masses during the late Saalian–late Weichselian interval, MIS 2–6 (Fig. 24e).
NORTH SEA–MØRE MARGIN
Glacigenic debris flow units — Several of the units identified along this margin are composed predominantly of glacigenic debris-flow deposits (King et al. 1996; Sejrup et al. 1996). The individual flows, which are lensoid in cross-section, are acoustically homogeneous and are commonly separated from each other by low-to-medium-amplitude reflectors. Large variation in sediment distribution and thickness characterize these units (Fig. 24d), which have been sourced from glacigenic diamicton deposited at the grounding line when the Norwegian Channel Ice Stream reached the shelf edge (Sejrup et al. 1996; King et al. 1998; Nygård et al. In press ).
Hemipelagic/gravity-flow units — These units are acoustically transparent or are characterized by discontinuous, but coherent reflectors. Sampling of one of the units revealed a clay and sandy silt composition. The seismic pattern indicates that the units are composed of slide material and gravity flows, in addition to the hemipelagic sediments.
Slide units — Two slides units, the Tampen and Møre slides, have been identified within the North Sea Fan (Fig. 24a and Fig. 24d). These units reach a maximum thickness of 170ms TWTT, and display a homogenous to transparent acoustic seismic pattern. The Tampen Slide event occurred sometime between the Saalian and Weichselian glaciations (MIS 4–6?), whereas the Møre Slide unit is older, occurring between MIS 6 and MIS 8–10.
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This page was Last updated 20 September 2002