Late Triassic to Early Jurassic climatic change, northern North Sea region: impact on alluvial architecture, palaeosols and clay mineralogy - From Depositional Systems to Sedimentary Successions on the Norwegian Continental Margin - page 71

Statfjord
33/12-2

CDP, Snorre Field
(Based on 18 cored wells)

Gullfaks H.
34/10-13

850

800

ULF1 Top

ULF1 Top

750

700

MLF Top 650

MLF Top

600

550

500

450

400

350

LLF Top

L LF Top

300

250

200

150

100

50

ALKE Top

A LKE Top 0

0 0.2 0.4 0.6 0.8 1

Channel sandstone fraction

More than 75% of ch. sandstone

A/S rise

40%-75% of ch. sandstone Gamma log

A/S fall

Less than 40% of ch. sandstone

Fig. 4. Channel deposit proportion (CDP) in the Lunde Formation from the Snorre Field, compared with well logs from the
Statfjord and Gullfaks H fields. The CDP trend line illustrates the general fining upward in the Lunde Formation and how
the rate of accommodation (A) versus rate of sedimentation (S) (A/S) can be inferred to have changed during deposition of
all the allostratigraphic units in the Lunde Formation.

of individual channel infill successions, frequent
internal erosional surfaces and pebble beds. They
are interpreted to have been formed in highly
mobile braided stream channels and channel
belts, forming sheet-like multi-storey and multi-
lateral composite sandstone units with lateral
extents of several kilometres (Table 5, Figs 3 and 6).
Channel infill successions floored by extrabasinal
pebble beds are inferred to represent high-energy

flood events and internal erosional surfaces as
cut-and-fill structures caused by fluctuating flow
energy. Occasional distinct fining-upward chan-
nel infill successions may indicate periodical dis-
section of the floodplain by single, narrow stream
channels. Coal fragments probably represent plant
debris that has been coalified during periods with
high groundwater level in parts of the alluvial
basin.