Mesozoic and Cenozoic basin configurations in the North Sea - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 444

during tilting of the Horda Platform, forced by ver-
tical uplift of southern Norway. The tilting of the
basin strata also explains the pinch-out of the
Early Oligocene CSS-3 sequence along the eastern
margin in the northern part of the North Sea Basin
(Faleide et al ., 2002). The uplift is here suggested
to have been most pronounced in western parts of
South Norway, thus explaining major sediment
contribution to the eastern and central North Sea
Basin and very limited sediments in the northern-
most North Sea area. The sediments were proba-
bly transported along established topographic
lineaments and faults (Fig. 15D), as has also been
proposed by Eidvin et al . (2010).
Phases of tectonic uplift of the hinterland con-
tinued throughout the Oligocene, indicated by the
presence of coarse-grained sediments in the Upper
Oligocene succession, deposited simultaneously
with major subsidence in the Norwegian-Danish
Basin (Jarsve et al ., submitted).
The progradational Miocene CSS-5 to CSS-7
sequences in the central North Sea reflect a pro-
longed existence of a source area in Scandinavia.
This is substantiated by observations of truncation
at the Fjerrislev Fault Zone of Upper Oligocene
strata in Late Oligocene to Early Miocene time
(e.g. Rasmussen, 2009) and hence indicates
renewed phases of uplift of the hinterland. The
thinning of the Miocene CSS-5, CSS-6 and CSS-7
sequences across the Norwegian-Danish Basin
indicates that the accommodation space here was
filled during Oligocene time. Incision of Miocene
channels into Oligocene strata in the northern
North Sea has been allocated to a drop in rela-
tive sea-level in Early Miocene time (Rundberg
et al ., 1995; Gregersen, 1998; Faleide et al ., 2002).
However, the presence of sequence CSS-5 depo-
centre in the southern parts of the study area indi-
cates uplift of parts of the northern North Sea as
well. If this erosion had been caused by a eustatic
drop in sea-level, then it is also probable that cen-
tral parts of the North Sea would have been
exposed for erosion.
The major Late Miocene sediment accumula-
tion (CSS-7) in the Central Graben area was
deposited during rapid subsidence of the basin.
Although this phenomenon occurred simultane-
ously with increased sediment input from the
Baltic river system in the east and south-east
(Bijlsma, 1981; Gibbard, 1988; Cameron et al .,
1993) and a potential global cooling (Zachos et al .,
2001), it is difficult by these processes alone to
explain the subsidence which was created to

accommodate for the vast quantities of sediments
deposited during Late Miocene time. Therefore,
tectonic subsidence, although non-fault related, is
suggested here to have occurred in Miocene time.
This was also strengthened from observation of a
regional unconformity at the base of Pliocene in
the eastern North Sea by Japsen et al . (2007), who
proposed that the Norwegian-Danish Basin was
exhumed in Late Miocene and Early Pliocene
times. This indicates that sediments belonging to
sequence CSS-7 in the Central Graben area include
re-worked sediments.
The truncation of the Pliocene and Early
Pleistocene sequences (CSS-8 and CSS-9) across
the Norwegian-Danish Basin to the Ringkøbing
Fyn High and the Stavanger Platform indicates
that glaciers reached the north-eastern margin of
the Central Graben area at the glacial maximum.
This was also proposed by Sejrup et al . (2005).
This is also observed in the Norwegian Sea
(Stuevold & Eldholm, 1996), where more exten-
sive glaciers of Pleistocene age reached the shore-
line and eroded the earlier Mesozoic and Cenozoic
sedimentary layers (Jansen & Sjøholm, 1991).
The sub-parallel configuration of the seismic
reflections of sequence CSS-10 relative to seabed
indicates that the sequence was deposited after
most of the uplift of southern Norway, both tec-
tonic uplift and uplift related to isostatic rebound
from glacial erosion of the hinterland. The main
tilting therefore occurred during deposition of
sequences CSS-8 and CSS-9, due to isostatic
rebound from glacial erosion and tectonic uplift of
southern Norway.

Coupled source-to-sink dynamics

As described above, there appears to be a direct
relationship between creation of accommodation
space in the North Sea area and influx of silici-
clastic debris from hinterlands at the basin mar-
gins. We suggest that this can be best explained by
a geodynamic model in which crustal uplifts in
the hinterlands are linked to basin formation and
subsidence in the North Sea area.
A coupled source-to-sink model is established
for basin configuration 1; the prograding sequences
filled the accommodation space that developed
during the active stretching phase in the Late
Jurassic to earliest Cretaceous. The creation of the
accommodation space by basin subsidence can
thus be linked to uplift of parts of southern
Norway and increased rates of erosion and