Slope Turbidite Reservoir Development along a Tectonically Active Margin (Part II) — An Up-System Perspective from the Upper Cretaceous, Offshore Norway
The composition, volume and stratigraphic organisation of
slope systems deposited along continental margins are expected to reflect the
landscape from which the sediment was derived. During the Late Cretaceous, the Møre-Trøndelag margin, northern Norwegian North Sea was dominated
by the deposition of deep-marine mudstones; regional supply of sand-rich turbidites only occurred during a c. 3 Myr period in the Turonian. This
mudstone-dominated succession has generally been interpreted to reflect the
existence of low onshore topography and the absence of efficient, high-energy
sediment transport systems onshore at this time. In this talk we focus on the
characteristics of the routing system associated with the so-called
‘Turonian sediment pulse’, and we build on our companion talk where
we established that the Turonian sediment pulse was associated with the
deposition of 11 closely spaced submarine fan systems. The 11 fan systems were
fed by sediment that was routed through a number of submarine canyons incised
into the eastern basin margin. The areal extent of the onshore drainage
catchments that supplied sediment to the fans has been estimated based on
scaling relationships derived from modern source-to-sink systems. In addition,
sediment volumes have been calculated and compared to expected sediment loads
from modern drainage catchments of similar extent. The results of our study
suggest that the Turonian fans were sourced by drainage catchments that were up
to 2200 km2 and which extended up to 140 km from the shoreline. The estimated
inboard extent of the catchments correlates to the innermost structures of a
large fault complex, which is thought to have defined the position of the
regional drainage divide in this region since the Devonian. Based on our
analysis we conclude that increased sediment supply to the Turonian fan systems
reflect tectonic rejuvenation of the landscape, rather than eustatic sea-level
or climate fluctuations. The duration of fan deposition is thus interpreted to
reflect the ‘relaxation time’ of the landscape following tectonic
perturbation, and fan system retrogradation and final abandonment is
interpreted to reflect the eventual depletion of the onshore sediment source.
We have demonstrated that a better understanding of the stratigraphic
variability of deepwater depositional systems, and the volume of potential
reservoir units, can be gained by taking a complete source-to-sink view of
ancient sediment dispersal systems.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California