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into the deeper basin (cf. Stewart & Clark, 1999).
Critical to these interpretations is the assumption
that when pod grounding occurred there was
no further accommodation available in the pod
locations and that deposition was permanently
re-located to interpod areas characterised by salt
dissolution, fluvial incision and sediment by-
pass. Whilst plausible, this model does not take
into account the accommodation available due to
regional post-rift basin subsidence following Late
Permian and Early Triassic extension (Steel &
Ryseth, 1990; Müller
et al
., 2005) and Early
Permian thermal events (van Wees
et al
., 2000)
which would have been available for fluvial aggra-
dation above the crests of grounded pods. As a
result, whilst the interpod palaeovalley model is
realistic, it can only represent an end-member sce-
nario where stratigraphic base level (Muto & Steel,
2000) was permanently located at or below the
level of the grounded pod crests (Fig. 15A). In
addition to this situation it is also possible to
envisage additional scenarios in which on-going
regional subsidence sustained accommodation
creation for continuous aggradation above the
level of grounded pods (Fig. 15B) or a transitional
situation in which fluctuations in stratigraphic
base level above and below the pod crests forced
alternations between regional aggradation and
focussed incision and back-filling within interpod
palaeovalleys (Fig. 15C). Subsequent erosion of
the thinner, more elevated, successions above the
grounded pods during Middle Jurassic thermal
(A)
incision
Aggradation and incision
confined to interpod
accommodation.
Sediment bypass to
deeper basin.
(B)
Regional aggradation,
enhanced interpod
subsidence provides
locally enhanced
preservation potential.
(C)
incision
Regional aggradation,
episodic incision, with
location influenced by
areas of enhanced
interpod subsidence.
Fig. 15.
Model for the stratigraphic fill of interpod regions under varying relationships between the fluvial profile relative
to the crest of the grounded Smith Bank Formation pods and interpod salt highs. (A) Following Smith Bank Formation pod
grounding deposition was permanently relocated to interpod areas where on-going salt evacuation and/or dissolution
created the only available accommodation for accumulation of Skagerrak Formation sands. Interpod areas became conduits
for sediment supply to the deeper basin. (B) Continuous aggradation above the level of the pods and interpods due to
regional basin subsidence, with no falls in geomorphic base level. (C) On-going basin subsidence allowed continuous
aggradation above pod level, with interpod areas supplying localised zones of higher subsidence. Episodic fluvial incision
was focussed into these interpod areas during falls in geomorphic base level. Model B appears to be the most common
situation on the UK Western Platform.
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