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 364

sanding and coarsening-upward

100

Top

90

80

70

60

50

40

30

20

10

Base

0 cm

Fig. 11. Facies associations FA2 and FA3: Sanding and coarsening-upward, sand-dominated distributary-mouth bars.
Example taken from reservoir zone Tilje 1.1.1 (T1.1.1).

sand-dominated heterolithics with abundant bipo-
lar ripple cross-lamination and double mud drapes
(F5.1). Individual sandstone layers tend to increase
in thickness vertically in the succession (from 2 cm
to 5 cm), alternating with thick (3 cm) fluid-mud
layers. Seasonal indicators similar to those seen in
FA3 are present, but they are less common in FA4.
Combined-flow/wave-generated structures are also
present; however, structures indicative of tidal cur-
rents (e.g. single and double mud drapes, bipolar
ripple cross lamination) are pervasive. The tidal
indicators are commonly found associated with
fine-grained sandstone layers and thick homogene-
ous mudstones. These thick mudstone layers
formed by deposition from high suspended-sedi-
ment concentrations during one slack-water period,
or amalgamation of fluid muds formed during sev-
eral slack-water periods. The high suspended-
sediment concentrations and water turbidity formed

during river flood events, as indicated by the
thicker tidal drapes associated with the coarser
sand layers, caused the suppression of suspension
feeders from the Skolithos ichnofacies (MacEachern
et al ., 2005). Due to the lack of channelised facies
and the overall thickening, sanding and coarsening
upward trends, FA4 is interpreted to have formed
in low-relief, proximal to medial delta-front pro-
grading lobes, probably in a more distal location
than, or laterally adjacent to, FA3.

Facies association 5 (FA5): Proximal prodelta

FA5 (Fig. 14) is overall mud dominated. However, it
shows sanding-upward and coarsening-upward suc-
cessions that attain a maximum thickness of 4 metres.
The basal pinstripe-laminated mudstones (F7) com-
monly alternate or are overlain by lenticularly-bedded
wave- and/or current-dominated heterolithics (F5.4