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studies and concluded, based on their own
observations of the well exposed Campanian
shoreface to shelf strata of Book Cliffs, Utah
that shoreface-to-shelf facies models should be
revised to incorporate turbidite-rich shelf depos-
its in some cases. Other Western interior studies
have also revised earlier turbidite interpretations
to a shallow, littoral interpretation, e.g. Cardium
Formation of the Ricinus Field (Walker 1985c;
Walker, 1995). Whilst the Cretaceous of the US
Western Interior foreland basin is a very different
tectonic setting, it indicates that the processes
for generating turbidite style deposits in shallow
water are being reinvestigated, particularly in
the light of new knowledge about modern depo-
sitional settings (also reviewed by Pattison
et al
.,
2007). These studies add confidence to the infer-
ence that the recognition of turbidite type facies
does not necessarily imply a major increase in water
depth. The observation of interfingering between
shoreface and turbidite deposition on both Elgin-
Franklin and Fulmar fields tends to suggest that
a linked mechanism of tectonically-enhanced
regressive erosion followed by transgressive
ravinement is a more probable mechanism to
explain the combination of significant erosion
and turbidite mass flow deposition observed in
these areas (Fig. 26).
To summarise, the four local structural scenar-
ios explaining the deposition of four of the best
known Oxfordian to Early Kimmeridgian age tur-
bidite deposits of the Central Graben casts some
doubt on whether there is evidence in the Central
Graben for a global eustatic sea-level mechanism
that could have introduced a widespread and
dateable phase of turbidite deposition by low-
stand incised valley formation around the basin
margin. This conclusion compares well with that
of Underhill (1991) in a study of the Late Jurassic
seismic stratigraphy of the Inner Moray Firth
which concluded that active tectonics in exten-
sional basins probably overprint any regional eus-
tatic signal due to a variety of local tectonic and
sedimentary processes documented by seismic
onlaps and downlaps.
evolving geometry of the rift, geographical
location (rift margin or rift centre) and the tim-
ing of Triassic pod grounding on the Rotliegend
due to displacement of Zechstein salt.
2
The development of significant erosion sur-
faces within Upper Jurassic age shallow marine
sandstones was linked to tectonic mechanisms.
It is also probable that these surfaces are not
basin wide sequence boundaries, rather they
are local surfaces reflecting the dynamic and
geographically varied evolution of the basin.
Maximum flooding surfaces provide a more
reliable method of correlation throughout the
basin.
3
Identification of erosive truncation has improved
the understanding of the relationships between
tectonics and sedimentation. Intra-Jurassic ero-
sion of structurally controlled highs, such as (1)
fault block crests, or (2) grounded pods, can
result in uplift and subaerial erosion or subma-
rine shoreface reworking of previously deposited
Oxfordian age shoreface sandstones.
4
Tectonic uplift has resulted in localised forced
regression with associated shoreface erosion.
The products of this erosion, produced espe-
cially during storm events, may be re-deposited
as turbidites. These turbidites are transported
short distances (a few kilometres) and are pon-
ded in depositional lows such as the hanging-
wall of major faults. Five case studies have been
presented which suggest that local structural
controls are able to explain: (1) the development
of local unconformities and (2) the local deposi-
tion of Oxfordian to Early Kimmeridgian age tur-
bidite deposits.
5
It is suggested that some aspects of Upper
Jurassic sandstone deposition as previously
presented require revision. The proposal that
many phases of incised valley development
occurred during the Upper Jurassic generating
3
rd
order sequence boundaries (Partington
et al
.,
1993b) does not appear to be backed by sedi-
mentary evidence. While turbidite sandstones
are evidently developed at various times in the
basin history, their relationship to proximal flu-
vial systems and incised valleys is unproven.
Such turbidites may have been triggered by
either: (1) local tectonic uplift promoting fault
footwall failure, or (2) storm wave erosion of
shoreface deposits due to relative sea-level fall.
6
Transgressive, retrogradationally stacked shore-
face sandstones are commonly spiculite rich.
This is related to low energy shorefaces with low
CONCLUSIONS
1
Upper Jurassic sandstone deposits of the North
Sea Central Graben can be characterised
according to three tectono-sedimentary models
termed A, B and C which depend on the
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