3D forward modelling of the impact of sediment transport and base level cycles on continental margins and incised valleys - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 458

(A) Dip section through the XES 02 flume experiment

1 m

3

2

1

(B) Dip section through the Dionisos simulation

Contours of the XES 02 experiment

10 m

3

Incised valley

2

1

Fig. 2. Comparison of (A) a dip section through the XES 02 flume experiment (from Strong & Paola, 2008) and (B) a dip
section through the 3D numerical passive-margin model.

A first, huge, sedimentary unit was deposited
during the slow cycle (unit 1 on Fig. 2). A second,
smaller, unit exhibited erosional surface, toplap
truncation and steep downlap onto unit 1 (unit 2
on Fig. 2). A composite and complex third unit was
composed of a series of smaller units similar to the
second unit (unit 3 on Fig. 2). In more detail, dur-
ing the initial steady phase (0 ka to 26 ka, Fig. 3A-1),
despite all parameters being constant and accom-
modation rate being higher than sediment supply, a
long-term progradation of the sedimentary system
was recorded. This initial progradation corre-
sponds to a transitory phase characterised by a
widespread fluvial plain and numerous channels
(Fig. 3A-1), a fast downward movement of the
shoreline and centroid (Fig. 4, 0 ka to 26 ka).
Sedimentary systems progressively reached equi-
librium during this transitory phase. During the
slow sea-level cycle (26 ka to 78 ka, Fig. 3A-2), sub-
sidence was lower than sea-level fall on the west
side of the basin. Accommodation was decreasing
and a small incised valley was formed. The falling
rate was not fast enough to maintain channel at the
same location and the small incised valley gave
birth to multiple fluvial channels (Fig. 4). Despite
a nearly constant accommodation and supply,
autogenic cycles were characterised by channel

1 ∂

∂

h
t xydxdy t

∫∫

δ

(4)

H = (, )

A

Ω

1 ∂

∂

h
t

( )

∫∫

X = x xy dxdy t , δ

AH

Ω

1 ∂

∂

h
t

( )

∫∫

Y = y xy dxdy t , δ

AH

Ω

Equation 4: definition of the average thickness, H,
of a sedimentary layer and the centroid location,
(X,Y) (m), where A is the simulated area (m 2 )
and Ω the simulated domain; ∂h/∂t is the local
sedimentation rate, which could be positive
(deposition of sediment), or negative (erosion),
measured at the time of the deposition (m); δt is
the duration of the sedimentary layer.

RESULTS

Passive margin model

The first numerical simulation was performed to
simulate the evolution of a passive margin. The
simulated geometry and stratigraphy are in good
agreement with the flume experiment results
(Fig. 2). The numerical model reproduced the
large-scale architecture of this XES 02 experiment.