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Fluvial sandstone assemblage 3
(FSA3) - isolated meandering
or straight streams
34/4-9S
240
DT
40
0
10
GR
CALI
120
20
0.45
1. 95
NPHI
RHOB
-0.15
2.95
Clay
Si
Sand
The fluvial sandstone assemblage FSA3 within
the allostratigraphic units L05 to L03 in the upper
part of the Lunde Formation (ULF1) is character-
ised by a marked increase in floodplain facies,
while the average CDP ranges from about 36% in
L05 to 24% in L03 (Fig. 4). The uppermost part
of FSA3 is represented by L03 in Fig. 8. Channel
sandstone bodies generally occur as up to 7 m thick,
upward-fining units, with distinct erosional lower
boundaries towards underlying floodplain fines
and upper boundaries transitional into proximal
and distal overbank facies and overlying flood-
plain mudstone. The lower part of FSA3 sandstone
bodies commonly consists of a coarse-grained
sandstone or a granule basal bed, passing upwards
into medium-grained to fine-grained trough cross-
stratified beds and fine-grained to very fine-grained
sandstone that is parallel stratified and laminated,
or structureless and strongly bioturbated. The
bioturbation is represented by up to c. 1 cm thick
burrows of various orientation.
The internal organisation of facies, upward-
fining vertical grain-size distribution, abundance
of bioturbation and lack of stacked multi-storey
composite sandstone bodies have been interpreted
in terms of isolated single channels formed by
fluvial incision in floodplain mud, succeeded by
vertical aggradation of sediments during waning
stream energy and coalescence of the uppermost
bioturbated channel fines with the adjacent flood-
plain mud. The channels may have been straight,
or meandering with restricted lateral migration
(Fig. 3, Table 5).
20
L01
30
40
2550
60
Meandering
channel deposits
70
L02
80
Meandering
channel deposits
90
Fluvial sandstone assemblage 4
(FSA4) - meandering streams
2600
Fluvial sandstone assemblage FSA4 occurs in the
uppermost part of the Lunde Formation, ULF 2 and
is comprised of allostratigraphic units L02 and L01.
However, these two units differ markedly in their
content of channel sandstone units, with CDPs of
Meandering
channel deposits
10
L03
Meandering
channel deposits
20
Fig. 8.
Sedimentary log from well 34/4-9S, Snorre Field,
showing characteristic stratigraphic organisation of fluvial
sandstone assemblage FSA4 in the upper part of theLunde
Formation (ULF). The sandstone bodies are interpreted as
having formed in meandering rivers on mud-dominated
floodplains. Gr = Gamma ray, CALIP = Caliper, DT = Velocity,
NPHI = Neutron porosity, RHOB = Density.
Channel deposits
Crevasse splay/channel deposits
Floodplain deposits, red
Clay Si
Sand
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