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 389

Tectonic influence on the Jurassic sedimentary architecture in the
northern North Sea with focus on the Brent Group

ATLE FOLKESTAD*, TORE ODINSEN*, HAAKON FOSSEN † , a
and MARTIN A. PEARCE ‡
* Statoil, Bergen, Box 7200, Bergen 5020, Norway (E-mail: [e-mail])
† Department of Earth Science, University of Bergen, Allégaten 41, 5007 Bergen, Norway
a Natural History Collections, University Museum of Bergen, PO Box 7800, 5020 Bergen, Norway
‡ Statoil Gulf Services LLC, 2103 CityWest Boulevard, Houston, Texas, 77042, USA

ABSTRACT

It is known from previous studies that the Middle Jurassic succession in the northern
North Sea has been influenced and controlled by syn-depositional fault activity. In this
study from the Gullfaks-Kvitebjørn area, we build upon that knowledge with seismic
cross-sections, well-correlations and cored intervals to evaluate features that can be
linked to Middle-Late Jurassic rifting in the northern North Sea. A regional east-west
transect shows an overall wedge-shaped Jurassic succession in the strike-section
between two long-lived Permo-Triassic faults, with a marked asymmetric thickness
distribution from the Ness Formation and upward. In a local section across the
Kvitebjørn Field the same pattern is identified, but here the thickness differences are
more pronounced. We suggest that the sedimentological response to this Middle
Jurassic tectonic activity is reflected by the formation of local depocentres with stacked
tidal dunes, differences in lithological characteristics along strike within stratal units
and facies variability along an irregular coast with enhancement of tidal currents in the
funnel-shaped hangingwall areas of rotated fault-blocks. These integrated data suggest
that the Middle-Late Jurassic rift phase started in the Early Bajocian (basal Ness
Formation) within the Gullfaks to Kvitebjørn transect and with flexing at the crest of
the Permo-Triassic mega-block leading to a complex stratigraphic development of the
Brent Group at that location.

Keywords: Brent Group, syn-sedimentary tectonics, Middle Jurassic, early to main
rift-phase, northern North Sea.

INTRODUCTION of studies, albeit with different focus and interpre-

tations (e.g. Helland-Hansen et al ., 1992; Steel,
1993; Johannessen et al ., 1995; Færseth, 1996;
Fjellanger et al ., 1996; Ravnås et al ., 2000; Davies
et al ., 2000; Hampson et al ., 2004).
The North Sea Basin is built upon a structural
framework of faults and shear zones formed dur-
ing the Caledonian orogeny and the subsequent
extensional collapse of this orogenic belt in the
Devonian (e.g. Fossen et al ., 2008). The basin
was affected by two post-orogenic lithospheric
rift episodes, one during the Late Permian-Early
Triassic (Beach et al ., 1987; Gabrielsen et al .,
1990; Færseth et al ., 1995a) and one during the

The Jurassic northern North Sea (Fig. 1) is one of
the best-studied extensional rift basins in the
world, due to extensive hydrocarbon exploration
and production, especially within the economi-
cally important Middle Jurassic Brent Group. The
deposition of clastic Jurassic formations in this
basin is directly or indirectly influenced by tec-
tonic activity. Accordingly, it is important to under-
stand how this activity affected the depositional
environment. The interaction between tectonics
and deposition of the Jurassic succession of the
northern North Sea has been discussed in a series