Figure 3. Summary of main controls on Neogene sedimentation on the Atlantic margin of NW Europe
It is becoming increasingly apparent that Neogene
sedimentation was strongly influenced by tectonics, which may have driven
changes in oceanographic circulation and climate. The potential link
between tectonics and changes in deep-water circulation pattern is
particularly significant, as the effects of the latter are commonly
expressed in the geological record as erosional unconformities. These
linkages are summarised below and the resulting regional pattern of
sedimentation is illustrated in Fig. 3.
The base of the Neogene succession on the Atlantic
margin of NW Europe is marked, for the most part, by a regional
unconformity (see Fig. 6 and Fig.
7) that was formed by deep-water erosion.
It may be no coincidence that a major change in oceanographic circulation
occurred in the North Atlantic region during late Palaeogene–early
Neogene time as deep-water pathways were established linking the Arctic
and North Atlantic oceans, via the Greenland and Norwegian basins (Tucholke
& Mountain 1986). It is the plate-tectonic evolution of the region
that strongly influenced the development of deep-ocean connections, which
led to the present-day intermediate and deep-water circulation pattern (Fig.
3). Specifically, the opening of the Fram Strait (the Northern
Gateway), and the subsidence of the Greenland-Scotland Ridge (the Southern
Gateway), which includes the Iceland-Faroe Rise and Wyville-Thomson Ridge
(Jansen & Raymo 1996; Thiede & Myhre 1996).
It has been suggested that deep-water circulation in the
Norwegian–Greenland region may have been initiated during late
Eocene–early Oligocene time (Berggren & Schnitker 1983; Ziegler
1988; Davies et al. 2001). However, a fully established pattern of
deep-water exchange may be a Neogene phenomenon, initiated in the Miocene
as the Fram Strait developed a true deep connection, and the
Greenland-Scotland Ridge became fully submerged (Eldholm 1990; Jansen
& Raymo 1996). This is supported by this study. The widespread
influence of deep-water circulation is evident on Fig.
3, which shows that
the entire area of the continental margin has accumulated sediment-drift
deposits. The base of the Neogene succession is at its most irregular and
erosive at the highly constricted, southwest end of the Faroe-Shetland
Channel, which represents the deepest passageway across the southern
gateway. This is an area where Oligocene inversion domes may have
triggered turbulent eddies in the flow path within the channel, causing
extreme erosion and sculpting of the sea bed (Smallwood In press).
The most significant intra-Neogene event, marked by the
early 'mid' Pliocene unconformity (Fig. 6 and Fig.
7), may have been
triggered by late Neogene uplift along the margin. Whilst the Plio-Pleistocene
prograding wedges are the most distinct expression of this event (Fig.
sea-bed erosion in the adjacent basins, commonly accompanied by a shift in
the focus of sediment-drift accumulation, indicates a plate-wide response
to change that also affected the deep-water circulation pattern. Although
this phenomenon has affected continental margins bordering a large part of
the North Atlantic region, its cause remains unknown (Japsen &
Chalmers 2000; Lundin & Doré 2002; Doré et al. 2002). Regardless of
uplift mechanism, the areas of uplift became focal points for the
nucleation and growth of extensive snowfields and ultimately ice sheets as
Northern Hemisphere climatic deterioration intensified in the late Neogene
(Eyles 1996). Mass-wasting processes have accomplished further
modification of the margin, possibly in response to glacio-isostatic
rebound and potentially invoking reactivation of long-lived fracture
The combined effects of tectonics, deep-ocean currents and glaciation
resulted in a physically-dynamic sedimentary environment on the Atlantic
margin of NW Europe throughout the Neogene interval. The preserved record
of sedimentation (Fig. 3) documents the interaction of various
depositional processes, notably downslope, alongslope and hemipelagic
(vertical flux) processes. The main characteristics of each of these
groups of processes are detailed in Fig. 4.
Click here to view list
of all references.