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 352

(A) Current-dominated Heterolithics

% of mudstone increases

10 Sand-dominated 40 Mixed sand/mud 60 Mud-dominated 90%

Sandstone Mudstone

60

60

60

20

20

20

20

20

40

20

40

40

40 40

cm

cm

0
cm

cm

cm

20

cm

20

20

20

20

0
cm

cm

cm

0
cm

0
cm

(B) Wave-dominated Heterolithics

% of mudstone increases

10 Mixed sand/mud 60 Mud-dominated 90%

Sandstone Mudstone

40

40 20

20

20 0

cm

cm

0
cm

Fig. 5. Heterolithic facies (Facies 5) in the Smørbukk field. All figures represent detailed sketches from core examples.
(A) Current-dominated heterolithics showing % of mudstone (dark) vs. sandstone (light). Notice the great variety of facies due
the variability of parameters used for classification (e.g. thickness, sand grain size, sedimentary structures, bioturbation).
(B) Wave-dominated heterolithics showing % of mudstone.

structures and diverse levels of bioturbation rang-
ing from sparse to abundant. The heterolithic
deposits were divided into 3 main groups based on
their sand : mud ratio (Fig. 5) and then subdivided
further based on their dominant sedimentary struc-
tures (current vs. wave influence), bedding style,
grain size and bioturbation-index value.

the presence of bidirectional dune cross-bedding,
current-ripple cross-lamination and paired, poorly
to more laminated mudstones (Figs 6B & 6C), indi-
cate that tidal currents played an important role in
its deposition. The presence of sporadic gravel and
pebble lags showing normal grading into coarse
to fine sands with thick, structureless, mudstone
layers that are interpreted as fluid muds (Ichaso &
Dalrymple, 2009) suggests that river floods were
important: the higher-than-normal discharge is
required to introduce the gravel and is also responsi-
ble for increasing the suspended-sediment concen-
tration. The sparse and low-diversity bioturbation is

5.1) Sand-dominated heterolithics

The flaser-bedded and heterolithic nature (sand-
stone : mudstone ratios between 90 : 10 and 60 : 40;
Fig. 5) of facies 5.1 (Figs 6A, 6B & 6C), coupled with