The Ormen Lange turbidite systems: sedimentary architectures and sequence structure of sandy slope fans in a sediment-starved basin - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 630

(D) (C)

Late Danian Danian

(B) (A)

Maastrichtian

Earliest Danian
to latest Maastrichtian

Fig. 13. Conceptual depositional settings for (A) the Upper Maastrichtian Springar sandstones, (B) the uppermost
Maastrichtian to lowermost Danian Springar and basal Tang Formation sandstones (or Våle heteroliths), (C) the Danian Egga
sandstones; and (D) the uppermost part of the Danian Egga sandstones. The bulk of the Springar and Egga sandstones form
a series of organised sandy fan lobe complexes developed on several slope minibasins and terraces with an overall out-
building of the fan systems from the Maastrichtian to the Danian. The uppermost part of the two fan systems formed during
phases of basin margin structuring and tilting and represent a more disorganised style of sandy slope deposition.

background sandy fan units, whereas the same unit is
represented by an erosional surface with overlying
lag deposits in the intermediate slope area.
Stratigraphic development: The lower part of
the Springar sandstones shows an early stage of
fan arrival and outbuilding in the Ormen Lange
area, probably via fill-spill from the upslope mini-
basins such as the Slørebotn Subbasin (Fig. 13A).
Thicknesses of turbidite beds suggest that only the
larger flows were able to overspill from upslope
mini-basins. The interbedded and thinner distal
turbidite beds probably represent smaller-scale
event beds, in turn suggesting upslope capture of
the main body of the flow. The resultant geometry
of the lobe storeys is therefore probably a broad,
low-relief mounded to pseudo-sheet-like features
(e.g. see Remacha & Fernandez, 2003). Deposition
occurred as a series of compensational lobe-build-
ing events at the base-of-slope to inner basin
floor, separated by intervals of predominantly
hemipelagic deposition. The latter is related to
lobe avulsion or upslope capture of active lobe
deposition. Gross sedimentation rate was relatively
low, suggesting that prolonged time intervals are

represented by the hemipelagic-pelagic lobe sto-
rey caps. This well-organised style of terminal fan
deposition was relatively abruptly replaced by a
more disorganised style of deposition in the
Ormen Lange subbasin, represented by the upper
part of the Springar and the basal Tang Formation
sandstones ('Våle heteroliths').
This subsequent (i.e. upper Springar and basal
Tang) depositional stage involved upslope mass
wasting with the downslope formation of 'clastic
collapse wedges' constructed of slump or mass
transport units and sandy debris flow deposits,
herein jointly referred to as 'Mass Transport
Deposits' or 'MTDs'. Concomitantly, there was a
marked basinward shift in the channel facies and
lobe facies tracts, with inner or proximal fan
channel-belts placed upon outer fan lobes without
or with only thin development of mid-fan
channelised lobe deposits (Fig. 13B). Notably, the
channel-belt seems to have been forced away
laterally from the lower slope mass-transport
deposits, feeding more localised, coarser-grained
and potentially more elongate (Deptuck et al .,
2008) channel-mouth lobes or splays.