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 76

34/7-3

40 240

0.45

DT

0
6

GR 120

NPHI -0.15

CALI 16

1.95 RHOB

2.95

Sand

Clay

Amundsen Fm

2410

2420

Braided stream
channel belts

S1

2430

2440

S2

Braided stream
channel belt

2450

2460

S3

Braided stream
channel belts

2470

2480

2490

S4

2500

Braided stream
channel belt

2510

Fig. 9. Sedimentary log from well 34/7-3,
Snorre Field, showing characteristic strati-
graphic organisation of fluvial sandstone
assemblages FSA5 in S5 and S4 and FSA6 in
S3 to S1, in the Statfjord Group. Allostratigraphic
unit S1 is overlain by a marine transgressive
ravinement conglomerate at the base of the
Amundsen Formation in the Dunlin Group.
Gr = Gamma ray, CALIP = Caliper, DT = Velocity,
NPHI = Neutron porosity, RHOB = Density.

2520

S5

Clay Sand

Channel deposits

Crevasse channel deposits
Floodplain deposits, red
Floodplain deposits, green/grey

Tr ansgressive lag
Open marine shelf

beds in the Eiriksson Formation in other parts of
the northern North Sea area (Ryseth, 2001).
The fluvial sandstone bodies of USG are attrib-
uted to high-energy braided streams. The braided
channel style was most likely triggered by the
influx of coarse-clastic debris (cf. Schumm, 1981);
an increase in precipitation and river discharge
combined with overall low accommodation space

could have resulted in high transport capacity and
enhanced stream competency during flood events.
Cross-stratified sandstone beds are inferred to
represent 3D sand dunes and massive and paral-
lel-stratified beds formed during high discharge
floods (Nystuen & Fält, 1995; Ryseth, 2001).
These sandstone bodies provide high quality oil
reservoirs and their wide lateral extent, proposed