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 362

Tidal limit

FA.8 FA.9

FA.10

FA.2

FA.3

FA.1

FA.4

FA.5

FA.7

FA.6 FA.3

FA.1 Lower shoreface FA.5 Proximal prodelta FA.8 Tidal-fluvial channels

FA.2 Marginal - normal marine lags
FA.3 Distributary-mouth bars

FA.6 Storm-influenced delta front FA.9 Heterolithic tidal point bars

FA.7 Distal wave-influenced
delta front

FA.10 lnterdistributary bay

FA.4 Proximal to medial
tidally-influenced delta front

Fig. 9. Map-view representation of a mixed tidally-influenced and wave-influenced lobate deltaic system and adja-
cent shoreface, showing location of the interpreted facies associations for the upper Åre and Tilje formations in the
Smørbukk field.

expression of the Cruziana Ichnofacies. Mudstone
lenses and interrupted lamination are visible.
Locally, angular limestone grains, small shell frag-
ments and faecal pellets are present at the base.
These deposits are occasionally overlain by sharp-
based, poorly sorted, matrix-supported sandstones
that commonly display cross-bedding and floating
angular limestone grains (F2). The matrix-supported
nature of the sandstones, their homogenised texture
and the local abundance of floating angular lime-
stone grains and local shell fragments imply rework-
ing in a setting with slow to negligible sedimentation.
Low-angle cross-bedding, coupled with the pres-
ence of large vertical burrows, indicate moderate-
energy to high-energy levels of wave motion (below
fair-weather wave base but above storm base) or
tidal currents. FA2 is interpreted to represent sandy
lags deposited in a shallow, marginal to open-marine
setting. In situations where these lags are more than

ca. 1 m to 2 m thick, the possibility exists that it rep-
resents a transgressive shelf ridge or shoal, such as
those present on the US East Coast or on the outer
margin of abandoned and submerged lobes of the
Mississippi Delta (Snedden & Dalrymple, 1998).

Facies association 3 (FA3):
Distributary-mouth bars

FA3 (Figs 11 and 12) comprises both sandy and
mixed sandstone-mudstone deposits. The sandy
examples coarsen and become sandier upward in
successions 2 m to 4 m thick. The erosively and/or
sharp-based intervals of cross-bedded sandstone
(F2 and F5.1) contain fluid-mud layers (up to 3 cm
thick) and/or unconsolidated (angular) rip-up
mud clasts and are commonly overlain by stacked
cross-bedded sandstones alternating with bipolar
ripple cross-laminated sandstones containing