Unravelling the nature of deep-marine sandstones through the linkage of seismic geomorphologies to sedimentary facies; the Hermod Fan, Norwegian North Sea - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 654

(A)

Channels
Splays

Branching

Lateral splay

'Scallops'

Feeder
channel

Avulsion

Frontal splay

0 2.5 km

(B)

5

1

3

2

4

Forward stepping

0 2.5 km

Fig. 6. Un-interpreted (left) and interpreted (right) RGB-blend time slices (10 Hz, 11 Hz and 13Hz). (a) Key stratigraphic
elements in a channel-splay complex and (B) a series of basinward stepping transient fans. a dashed line annotated on
channels indicates segments that have become abandoned due to avulsion. Repeated sediment blocking in the frontal splay
region may have set the scene for a series of avulsions followed by new elongation of channels along a different path. The
inferred youngest avulsion point occurred further up-stream and resulted in a lateral fan switch.

some 4 to 6 km. Both channels then turn 90°
towards the right (i.e. back to the original orienta-
tion) and terminate more or less at the fault loca-
tion. C1N follows a similar pattern on encountering
a substratum fault, but the channel segment with a
north-eastward orientation has a length of more
than 10 km (Fig. 5). The frontal splays are charac-
terised by a braided zone where the channels
branch into narrower distributary channels down-
stream to a point where they approach the scale of
seismic resolution and fringe out in a radial pat-
tern (Fig. 6a). The length from the onset of chan-
nel branching to the point where the terminal
splays thin to a scale below seismic resolution is
typically less than 3 km.

The characteristic patterns described for the
branches of C1S can be related to temporary devi-
ations from the overall south-eastward fan pro-
gradation, due to subtle north-eastward oriented
sea floor depressions. The fault structuration of
sea floor morphology was probably negligible by
the time the youngest and most distal branches
re-gained their south-eastward orientation and
spilled towards the south-east. a similar interpre-
tation of a gradual south-eastward progradation of
the Hermod Fan, interrupted by temporary fault-
influenced deviations towards the northeast, can
also apply to the C1N channel. The smaller scale
channel branching within the frontal splay zones
probably resulted from aggradation of sediments