Mesozoic and Cenozoic basin configurations in the North Sea - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 420

the identification and mapping of units with
seismic stratigraphic patterns indicative of progra-
dation, aggradation and transgression, as well as
variations in reflection amplitudes and frequency
spectra. Seismic sequence stratigraphy was car-
ried out by identifying sequence stratigraphic
surfaces like subaerial unconformities (SU), trans-
gressive surfaces (TS) and maximum flooding
surfaces (MFS) from the presence of reflector ter-
minations as downlap, onlap, toplap and toplap
truncations (Mitchum et al ., 1977; Van Wagoner
et al ., 1988; Fig. 2). Sequences are defined as trans-
gressive-regressive (T-R) sequences (Embry, 1988,
1993, 1995; Embry & Johannessen, 1992) in accord-
ance with depositional geometry. The transgres-
sive systems tract is identified by retrogradational
or aggradational strata geometry above uncon-
formities defined by underlying toplap or/and
toplap truncation and regressive systems tract by
progradational geometry with clinoforms down-
lapping on maximum flooding surfaces. In some
sequences SU, TS and MFS coincide within the
present seismic resolution (Fig. 2).
Each of the seismic stratigraphic sequences was
mapped and the results are presented in the form
of time-thickness maps and examples from the
seismic lines. Particular attention was given to the
identification and mapping of positions of maxi-
mum thickness (depocentres) for each unit. The

sequences are described and discussed in terms of
their geometrical characteristics following compac-
tion and for some sequences, also formed by post-
depositional erosion. Therefore, time-thickness
maps and clinoform heights referred to in the text
must be considered as minimum values.

Regional geology

In this section we summarise the regional geology
in the North Sea Basin, with emphasis on the
Mesozoic and Cenozoic periods, as the deposi-
tional patterns presented in this study were highly
influenced by the regional tectonics throughout
the Late Mesozoic and Cenozoic.
The North Sea Basin configuration reflects two
major post-Caledonian basin-forming events,
namely the Permo-Triassic and the Late Jurassic
to earliest Cretaceous. The Permo-Triassic devel-
opment affected the entire south-west Norwegian
realm including the Skagerrak to Oslo Graben
system, whereas the Late Jurassic to earliest
Cretaceous phase mainly affected the (present)
continental shelf, including the northern, central
and eastern North Sea (Badley et al ., 1988; Ziegler
& van Hoorn, 1989; Gabrielsen et al ., 1990; Roberts
et al ., 1990; Ziegler, 1990, 1992; Yielding &
Roberts, 1992; Milton, 1993; Rattey & Hayward,
1993; Nøttvedt et al ., 1995; Færseth, 1996;

(A)

CSS-10

CSS-9

M

CSS-8

CSS-7

L

K

CSS-6

J

CSS-5

CSS-4

H

I

CSS-3

F

G

CSS-2
CSS-1
Chalk
Group

Basin
configuration 3

Basin
configuration 2

Figure 8b

K-2.1

E

D

J-2

B
and
C

Sequence unconformity
Marine flooding surface
Flooding surface

J-1

Fig. 2. (A) Schematic figure showing the various sequences recorded in this study, with emphasis on the sequence
boundaries.