Tectonic influence on the Jurassic sedimentary architecture in the northern North Sea with focus on the Brent Group - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 406

transition of progradational to more aggradational
shorelines due to increased accommodation. By
contrast, the shoreline reaches further basinward
at the footwall highs and are characterised by
progradation with low-accommodation facies as
wave-dominated strata, as indicated in Fig. 11 (see
Gawthorpe & Leeder, 2000). This explains the
observed lateral facies variability of the prograda-
tional part of the Brent Group (Fig. 12) in the pinch-
out area within such a fault-influenced context.

Well 35/4-1 is located in a hangingwall position
relative to a Permo-Triassic fault (Fig. 11) and
shows heterolithic strata (low net to gross ratio of
sand) displaying fluvial, tidal and wave influence
(Fig. 12A). Biostratigraphic analysis of the Brent
Group in this well indicates a gradual change from
freshwater influence (abundant Botryococcus ; see
Batten & Grenfell, 1996) in the lower part of well
35/4-1 (see Table 2) to brackish-water to marine
conditions towards the upper part (see Fig. 12A).

2°0 ′ 3°0 ′

33 34

34/6-1

35/4-1

34/8-1

?

?

61°0 ′ N

29

Early Bajocian

0 25 km

Offshore

Permo-Triassic faults
reactivated in Middle Jurassic

Wells

Delta front

Middle to Late Jurassic faults

Delta plain

Fig. 11. Schematic illustration of the prograding Brent Group (not progradational maximum), portrayed as an undulating
coastline where the footwall areas promote basinward deltaic extension with a relatively low shoreline trajectory and the
hangingwall areas show aggrading shoreline trajectories with a pinch-out somewhat more southwards than the footwall areas.