Eustatic, tectonic and climatic controls on an early syn-rift mixed-energy delta, Tilje Formation (Early Jurassic, Smørbukk field, offshore mid-Norway) - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 342

of sediment bodies within these units and the
influence of major eustatic, tectonic and climatic
controls on their accumulation. This paper presents
a revision of previous sedimentologic and sequence-
stratigraphic work on the Tilje Formation carried
out by Martinius et al . (2001, 2005), building on the
recent sedimentological insights on depositional
processes, facies distribution, stratigraphic archi-
tecture and palaeoenvironmental reconstructions
for the Tilje Formation (Ichaso & Dalrymple, 2009;
Ichaso, 2012). This paper focuses specifically on the
Smørbukk field (Fig. 1C). In more general terms,
this study aims to improve our ability to reconstruct
the distribution of depositional environments in
such complex, ancient tidal, successions, with a
particular focus on the interplay between subtle tec-
tonic movements and sedimentation in a rift-basin
setting.

with several sub-units (e.g. T1.1, T1.2, etc.). This
reservoir zonation was based on the integration of
sedimentological analysis, regional correlation
using ichnofabric analysis, Sm-Nd dating and a
sequence-stratigraphic model developed in the
Halten Terrace production area (Martinius et al .,
2001). As discussed below, most reservoir zones
are interpreted here to be parasequence sets that
are bounded either by flooding surfaces and/or
sequence boundaries. They, therefore, represent
approximate chronostratigraphic units that can be
correlated throughout the study area.
The sequence-stratigraphic framework inter-
preted by Martinius et al . (2001) for the upper Åre
and Tilje formations consists of three sequences
(Fig. 3). These sequences are separated by regional
second-order hiatal surfaces (SB2 and SB3), with
several second-order to third-order, or even higher-
order, flooding surfaces (FS) forming parasequences
and parasequence sets that are metres to tens of
metres thick. Sequence 1 comprises the upper Åre
Formation (A3; Fig. 3). Sequence 2 (reservoir zones
T1 to T3.1) occupies the lower Tilje Fm., extending
from the Åre-Tilje contact (SB2) up to an inferred
sequence boundary (SB3) in the mid-Tilje Fm.
Sequence 3 (reservoir zones T3.2 to T6) extends
from SB3 in the middle of the Tilje Fm. up to the
Tilje-Ror contact.
Sm/Nd isotopic data from the Tilje Fm. support the
regional and local correlation by indicating a consist-
ent provenance. Martinius et al . (2001) suggested a
significant change of provenance ages from younger
source units within Sequence 2 (1200 Ma to 1400 Ma)
to an older source (1500 Ma to 1800 Ma) in the overly-
ing Sequence 3. Previous work had suggested that the
main source area for the Tilje Fm. is the Fennoscandian
Shield to the east (Fig. 2B; Dalland et al ., 1988).
However, dip-meter and Sm/Nd isotopic data sug-
gested that the Tilje received sediments from the
Ribban Basin structure in the north (dominated by
erosion during the entire Jurassic), the Helland-
Hansen-Bodø (Utgard) High to the northwest and
west and/or from the Nordland ridge (Fig. 2B) in the
north-east (Martinius et al ., 2001). The area could also
have received sediments from local topographic
highs associated with the propagation of local normal
faults (Marsh et al ., 2010).
Structurally, the field lies at the crest of a tilted
fault block, bounded on the west by a major nor-
mal fault (the Smørbukk fault: Fig. 1C) and on the
north by an east-west-trending graben that tran-
sects the crest of the fault block (Ehrenberg et al .,
1992). Recently, 3D seismic-reflection data were

Tilje Formation in the Smørbukk field

The Smørbukk field was discovered in 1984. It
is situated approximately 230 km west of the
Norwegian mainland (mainly in block 6506/12) in
water depths between 250 m and 300 m and is
considered to be one of the deepest hydrocarbon-
bearing structures in the area (Klefstad et al .,
2005). Hydrocarbon reserves, mainly gas-rich con-
densates of mixed marine/terrigenous source, are
contained in sandstones of four Lower to Middle
Jurassic formations (Åre, Tilje, Ile and Garn). The
most common interpretation of the Tilje Formation
is that it accumulated in a tide-dominated deltaic
environment, during a late pre-rift to early syn-rift
stage (Ehrenberg et al ., 1992; Martinius et al .,
2001; Marsh et al ., 2010). This tectono- stratigraphic
interpretation is based largely on the absence of
basin-bounding fault margins, the absence of vol-
canic rocks, relative uniformity and continuity of
stratigraphic units, the nature of the heterolithic
deposits, the large lateral extent of depositional
systems, the overall sandier upward succession
and the vertical and lateral progradational arrange-
ment of facies (Ehrenberg et al ., 1992; Martinius
et al ., 2001), especially during the lower-middle
Tilje stratigraphic interval.
The Tilje Formation (150 m to 200 m thick) was
first divided into three major reservoir units
(Ehrenberg et al ., 1992), mostly based on the inter-
well correlation of offshore shales and bioturbated
intervals. More recently (2003 to 2004), the opera-
tor, Statoil, has divided the Tilje Formation in the
Smørbukk field into six reservoir zones (T1 to T6)