Unravelling the nature of deep-marine sandstones through the linkage of seismic geomorphologies to sedimentary facies; the Hermod Fan, Norwegian North Sea - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 647

sufficient information to mature a subsurface geo-
logical model that captured the complex geology
of these reservoirs (e.g. Bergslien, 2002).
The science of turbidite play analysis has
evolved simultaneously with the development of
the North Sea into a major petroleum province.
The rapid gathering of extensive amounts of data
resulted in a number of observations that could
only be partly understood in the framework
of existing models and several fields were
re-interpreted as the science evolved. The first
submarine fan model that related the vertical facies
successions observed in outcrops to fan positions
(Jacka et al ., 1968) was proposed one year after the
first oil discovery and the wide implementation of
such models arrived even later (Mutti & Ricci
Lucchi, 1972). The recognition of high-density tur-
bidites (Lowe, 1982) and linked debrites (Haughton
et al ., 2003) and the awareness of sand-injectites as
an important constituent in the petroleum system
(see Hurst & Cartwright, 2007 and references
therein) are other examples of advances in turbid-
ite play analysis that have occurred contempora-
neously with the production from and exploration
for, turbidite reservoirs in the North Sea.
Seismic acquisition and processing techniques
have also evolved rapidly over the last decades
and the prolific parts of the North Sea Basin are
gradually becoming blanketed with 3d seismic
data. It is now widely documented that many res-
ervoirs have a complex facies association that
has resulted not only from a variety of primary
depositional processes but also from different
types of sediment remobilisation such as slump-
ing, sliding or large-scale sand injection processes.
However, the relative importance of these various
processes may, in many cases, still be immeasur-
able due to the lack of core material and a seismic
dataset that delineates the reservoir geometries
clearly. This study targets an area in the Northern
North Sea where both depositional elements and
post-depositional sediment remobilisation can be
inferred from seismic geomorphologies in a mid to
outer submarine fan setting. The studied strati-
graphic unit is the Late Palaeocene to Early Eocene
Hermod Member of the Sele Formation ( sensu
Brunstad et al ., 2009). The Hermod Member is typ-
ically characterised in wells by thick successions
of mainly homogeneous sandstones with no appar-
ent traction structures or systematic grain size
grading and a sharp contact to both overlying and
underlying shale. This facies type is volumetri-
cally the most important constituent in the area,

but the origin of such entirely massive deep-marine
sandstone beds is still a subject of intense research.
The relevant working hypotheses include deposi-
tion under high-density turbidity currents (Lowe,
1982), debris flows (Shanmugam, 1995), or full
scale remobilisation of the entire bed leading to
obliteration of any primary vertical grain-size grad-
ing and depositional structures (Hiscott, 1979).
a turbidite interpretation of the typical massive
and non-graded sandstone tops with a sharp con-
tact to overlying shale is cryptic because turbidity
currents are expected to pass through a last waning
phase when a graded and stratified top should
form (Baas, 2004). Emplacement by sandy debris
flows is an alternative interpretation, but labora-
tory experiments indicate that run out on gentle
slopes (c. < 5 degrees) requires presence of lubricat-
ing clay minerals in the flow (Marr et al ., 2001).
The formation of massive non-graded sandstone
beds by post-depositional sediment remobilisation
is an interpretation that is particularly relevant for
the Tertiary of the North Sea (Jonk et al ., 2005), but
the fact that the occurrence of an abrupt transition
to shale above is more the rule than an exception is
still puzzling. This is a characteristic of the upper
boundary of the Hermod Member, not only in the
present study area, but throughout the Norwegian
North Sea, as described in the standard definitions
of the Hermod Member (Hardt et al ., 1989; Brunstad
et al ., 2009 and Norwegian Petroleum directorate
Fact Pages at www.npd.no ).
The combination of high-quality seismic images
from a formation buried to a depth of approxi-
mately 2 kilometres where cores are (mostly) lithi-
fied represents a unique opportunity to compare
and contrast the products of various geological
processes in a submarine fan. This has led previ-
ous researchers to use the present study area as a
case example to illustrate some key characteris-
tics of this depositional environment. Blikeng &
Fugelli (2000) identified a channel distributary
pattern with channels reaching the outermost
parts of the fan and pointed out the analogy to the
modern Mississippi Fan and the Permian Brushy
Canyon Formation, delaware Basin, USa. Hadler-
Jacobsen et al . (2005) presented data from the
same study area in a broader discussion of how
sediment delivery, gross shelf-to-basin relief, slope
gradient and basin topography control deep-
marine sedimentation. In this context, the outer
Hermod Fan was classified as a high shelf-to-
basin-relief system with a distinct slope set up by
the western Viking Graben bounding fault some