IN THE PYHATUNTURI AREA,

sedimentology of the Precambrian
Precambrian formations in eastern
Sedimentology
eastern and northern Finland.
Finland. 1986
19g6
Edited by Kauko Laajoki
Laajoki and
and Juhani
Juhani Paakkola
Paakkola
Geological Survey of Finland, Special
Paper
5:
239-254,
1988
Special
5:239-254, 1988
EARLY PROTEROZOIC
PROTIEROZOTC FLUVIAL DEPOSITS
IN THE PYHÄTUNTURI
PYHATUNTURI AREA,
NORTHERN FINLAND
FINLAND
by
J.
Räsänen
and
J. Räsänen and Merja Mäkelä
Räsänen, J.
J. & Mäkelä, Merja,
Proterozoic fluvial
fluvial deposits
Merja, 1988. Early Proterozoic
in the Pyhätunturi area, northern
northern Finland. Geological Survey 01
of Finland,
Special Paper 5.
5. 239-254, 15ligures.
15 figures.
In the Pyhätunturi
Pyhätunturi area, northern Finland, there is a well-preserved early
Proterozoic
Proterozoic metasedimentary
metasedimentary succession, more than 3 km thick, that also
ineludes
includes metavoIcanics.
metavolcanics. In the study
study area the rocks of this succession, collectively known as Jatulian,
Jatulian, form the lowermost part of the Karelia Supergroup, which overlies the older
group,
Lapponia
older supracrustal succession of the Lapponia
Supergroup.
In the study
formations,
study area the Jatulian succession
succession is divided into four formations,
(2) Pyhätunturi Formapreliminarity
(l) Isokuru Formation, (2)
preliminarity called the (1)
(3) Kiimaselkä Formation and (4) Kallioaapa
tion, (3)
Kallioaapa Formation, of which
the first two are described in this paper. The Isokuru Formation is characterized
well-rounded quartzite
acterized by elast-supported
clast-supported conglomerates
with well-rounded
conglomerates with
elasts.
clasts. The Pyhätunturi Formation is
is characterized by the high mineralogical maturity and
and homogeneity of quartzites.
On the basis of grain size and sedimentary structures both formations
are interpreted as
as fluvial deposits.
deposits. The fluviatile succession in the Pyhätunturi
er ranking fluvial system, which extends distunturi area is part of a high
higher
continuously
continuously for hundreds
hundreds of kilometres across the Central Lapland Schist
Belt.
paleoKey words: metasedimentary
metasedimentary rocks, quartzites, metaconglomerate, paIeosedimentology, fluvial
fluvial features,
features, Proterozoic,
Proterozoic, Jatulian, Pyhätunturi, Pelkosenniemi,
Finland.
kosenniemi. Finland.
Jorma
P. O. Box 77,
77, SF-96101
Jorma Räsänen,
Rtisänen, Geological Survey 01
of Finland, P.O.
Rovaniemi.
Merja Mäkelä,
Department 01
P. O. Box
Geology, University 01
of Helsinki, P.O.
Mdkelti, Department
of Geology,
115,
I 15. SF-00171
SF-0017 I Helsinki.
INTRODUCTION
The Pyhätunturi area is situated in central
central Lapland, northern Finland, about 100 km northeast
of Rovaniemi
l). The stratigraphy
stratigraphy of
of the area
Rovaniemi (Fig. 1).
was first described by Hackman
(1910,
1914,
1918,
Hackman
(1937,
1927)
by Mikkola
l94l).
Mikkola (1937, 1941).
1927) and later by
On the basis of re
cent mapping by the Geologirecent
cal Survey of Finland, the supracrustal rocks of
central Lapland are divided into fOUf
four supergroups,
in stratigraphie
l) Tuntsa, 2) Lapponia, 3)
stratigraphic order:
order: 1)
Karelia
4) Svecofennia
Karelia and 4)
Svecofennia supergroups.
supergroups.
The Archaean Tuntsa
Tuntso Supergroup
Supergroup has an indistinct relation
relation to its base.
base. It consists of granitized
paragneisses associated with
orthogneisses
and
orthogneisses and paragneisses
tholeiitic and komatiitie
metavolcanics (Juopperi
komatiitic metavolcanies
and Veki 1986, Räsänen et al.
al. 1986). An acid volcanie
canic rock associated with paragneisses has a zir239
239
Geological
Geological Survey of Finland, Special Paper 55
Räsänen and M
erja Mäkelä
Jorma Rdsdnen
Mtikelti
Merjo
T' ,'
t:."
t"".
(."
/^
I'ITILA=
o
O
o ()
o
(.)
Y
:.)
;^l+:.::
:::\.
st ö9ll:::
i-ni
>u'....::
rt
ell
Pel ;rohl9
~~
I~
ooo
Plutonic
Pluton
ic rocks
rocks
.um
Svecofenn
io Supergroup
Supergroup
Svecofennio
V» I
Korelio
Koretio Supergroup
ffiläilIil
r:rr.:::l
f.".....-..1
ö
^\
o\
25 30
zo'1
.
NORWAY
~
Tuntso Supergroup
mmHf}
Hiltilt]Il Tuntso
F-::::::::-
o
o
Lopponio
Lopponio Supergroup
Supergroup
FINLAND
2
ffi
ft)
.il-l
tl
li)
() () l
Archoeon
Gronitoid Comple
A rchoeon Gronitoid
Complexx
Fig.
Fig. 1.
l. Geological
Geological map o
off the central Lapland area
area,, showing the major lithostratigraphic units and the study area
area.. Modified
after Silvennoinen et al.
al. 1980.
granitizacon age of 2.8 Ga (Räsänen 1986). The granitizapresumably took place
ti
on of these supracrustals presumably
place
tion
(Räsänen
about
2.6
Ga
aga
(Räsänen
1984,
Silvennoinen
about 2.6 Ga ago
1984, Silvennoinen
1985)
1985)..
The Lapponia
Lapponio Supergroup,
Supergroup, which deposited on
granitic gneisses
gneisses and metavolcanic rocks,
Archaean granitic
consists
consists mainly
mainly of quartzites in its lower part and
metavo1canics
part. It is regarded as
metavolcanics in its upper part.
(Gaäl et al.
either Archaean (Gaal
al. 1978, Silvennoinen
Silvennoinen et
el
(Simonen
al.
1980)
or
Proterozoic
(Sirnonen
1980).
Accord1980\
Proterozoic
ol.
According to the latest observations,
observations, the quartzitic, lower
part of this
basal conthis supergroup starts with
with aa basal
glomerate and is
is intruded by aa layered intrusion
dated at 2.4 Ga (Räsänen 1986). It also seems high-
240
ly probable that the Tuntsa Supergroup was folded
before the formation of the Lapponia Supergroup
(Juopperi &
(Juopperi
Veki 1986).
1986).
& Veki
In northern
northern Finland the Karelia
Karelia Supergroup conconquartzites (Silvennoinen
(Silvennoinen 1985).
sists principally of quartzites
1985).
In the Central Lapland Schist Belt the quartzites
rest unconformably on the
the schists
schists and metavolcanics of the Lapponia Supergroup (Lehtonen et
e/
al.
1985, Kortelainen
ol.1985,
Kortelainen et al.
al. 1986, Lehtonen 1986)
and extend discontinuously
discontinuouslv from Salla via Sodankylä to
to Kittilä
Kittilä..
In the Peräpohja Schist Belt the Karelia Supergroup unconformably overlies layered gabbro in-
Geological Survey of Finland, Special
Special Paper 55
Early Proterozoic
Proterozoic fluvial
fluvial deposits
deposits in
in the
the Pyhätunturi area,
area, northern Finland
Finland
(Perttunen 1985).
trusions (perttunen
trusions
1985). A
A conglomerate, dep. 24),
scribed by Härme (1949, p.
24\, containing
containing gabquartzites and thus
bro pebbles underlies
underlies the lowest quartzites
indicates a hiatus. The gabbro intrusions have been
indicates
dated at 2.4 Ga (Kouvo; in Alapieti 1982, p.
p. 11).
I 1).
Accordingly, this
this is
is the
the lower age
age limit for
for the
Karelia
Karelia Supergroup.
Supergroup.
Granites of the Haparanda suite,
suite, 1.9 Ga (Welin
al. 1970),
1970), intrude the thick turbidite sequence
et al.
of the Svecofennia
Svecofennia Supergroup overlying
overlying the Ka(Perttunen 1985).
relia Supergroup (perttunen
The large Central Lapland Granite Complex
Complex includes remnants of granitoids, metasediments
eludes
metasediments and
metavolcanics. Obviously
metavolcanics.
Obviously this
this Granite Complex
was regenerated from Archaean basement rocks
was
(e.g. Lauerma
ab
out 1.8
about
1.8 Ga
Ga ago
ago (e.g.
Lauerma 1982).
OUTLINES OF THE STRA
TIGRAPHY IN THE PYHÄ
TUNTURI AREA
STRATIGRAPHY
PYHATUNTUNI
In the
In
the Pyhätunturi
Pyhätunturi area
area aa well-preserved
well-preserved sesequence of the Karelia Supergroup is surrounded
by a supracrustal sequence of the Lapponia Supergroup (Fig.
(Fig. 1).
group
l). South of pyhätunturi,
Pyhätunturi, the
the Lapponian
ponian supracrustal
supracrustal sequence
sequence ineluding
including mica
schist, mafic metavolcanics
metavolcanics and quartzite is overlain by
(Fig. 2)
lain
by the conglomerate (Fig.
2) that starts
starts the
Karelia Supergroup in
in the
the study area.
The Karelian sequence is divided into four formations called, in stratigraphie
stratigraphic order: Isokuru Formation,
motion, Pyhätunturi
Pyhätunturi Formation, Kiimaselkä
Kiimaselk(i ForFormation. They are
mation
mation and
and Kallioaapa Formotion.
are all
upward-facing
upward-facing and only slightly folded
(Fig. 3).
folded (Fig.
The intruding metadiabases have a zircon age of
2.0
2.0 Ga.
Ga.
The Isokuru Formation
Formotion is
is composed of polypolymictic orthoconglomerates and
modal
modal and
and polymictic
paraconglomerates with
paraconglomerates
with arkosite interbeds. The
v
lowest part of the formation and its contact with
the basement
basement are not exposed. The elasts
clasts are principally derived from the
Lapponian
rocks.
the
The Pyhätunturi
Formation overlying
Pyhritunturi Formation
overlying the Isokuru Formation has
basal contact,
has aa sharp
sharp basal
contact, suggesting that the conditions
conditions during sedimentation
changed abruptly. However, no unconformity
unconformity has
been observed. The most characteristic
characteristic features of
quartzitic comthis formation
formation are its homogeneous
homogeneous quartzitic
position and the
lack
of
muddy
rocks.
the lack
The
The overlying
overlying Kiimaselkä
Kiimaselkä Formation
Formatlon consists
consists
mostly of lava flows. All the lavas are massive and
homogeneous with amygdale-rich
amygdale-rich flow tops. They
are
are associated with minor
minor tuffites.
The Kallioaapa
Kalliosapa Formation,
Formotion, overlying
overlying the Kiimaselkä Formation, consists of muddy siItstones,
siltstones,
quartzites. Horizontal bedding,
dolomites and quartzites.
bedding, ineluding
ion and micro-crosslaminacluding thin
thin laminat
lamination
v
v
3 km
v
Fig.
(1979).
Fig. 2.
2. Geological map of the
the Pyhätunturi area. Simplified after Mielikäinen
Mielikliinen (1979).
16
241
241
Geological Survey of Finland, Special
Special Paper 55
Jorma
Räsänen and Merja Mäkelä
Mdkelti
Jorma Rdsdnen
FORMATION
FORMATION
VERTICAL
YEBr-lctL
I rrHntrac.rES
LlTHOFACIES
PROFI
PROF I LE
SEDIMENTARY
SEDIMENTARY STRUCTURES
STRUCTURES
INTERPRETATION
I NTERPRETATION
Sr
horizontallamination
horizonto[ [ominotion
morks
and
ripple marks
ond ripple
fluvial
fluviot environment
environment
distal
distot
( minor )
St
St (minor)
Sp,
sh
sp, Sh
slumping
ond sliding
stiding
slumping and
St,
St, Sp
SP
trough
trough cross-bedding
Sp
plan
ar cross- bedding
plonor
bedding
Gm
planar
ptonor cross- bedding
trough
cross- bedding
trough cross-
Kallioaapa
Kotliooopo Fm
Kiimasel
kä Fm
Kiimoselkö
Pyhä
tunturi
Pyhötuniuri
Fm
1600 -1900
- 1900 m
Sp,
sp, St
Isokuru
I sokuru
Fm
700 -1000
m
-1000 m
Sh
G~s
Gms
horizontal
horizonlol bedding
bedding
normal
groding
Inverse grading
normol and
ond inverse
(minor)
Sr
Sr (minor)
ripple
rippte marks
morks
Gm
+
proxrmol
prox
i mal
Sp
Gms
0ms
BASEMENT UNKNOWN
Fig,
3. Schematic
section of the Karelia Supergroup in the Pyhätunturi area, showing the characteristic sedimentary structures, lithofacies
Fig.3.
SchematicsectionoftheKareliaSupergroupinthePyhätunturiarea,showingthecharacteristicsedimentarystructures,lithofacies
and interpreted
refer to MiaU
Miall (1978).
interpreted sedimentary environment.
environment. Letters refer
graded-beds, with
tion, is common. Crossbeds and graded-beds,
alternating
muddy layers
layers capped
capped by
silty and
and muddy
alternating silty
mudcracks, are
are usually met with.
In the following, the Isokuru and Pyhätunturi
pyhätunturi
(1977,
formations are described applying Miall's (1977,
1978,
1978, 1985)
1985) facies
facies elassification.
classification.
THE ISOKURU FORMATION
Geological setting and description
South of Pyhätunturi the Isokuru
Isokuru Formation
Formation is
700-1000 m thick, but it thins
thins northwestwards.
As a result of deformation the primary sedimentary
been locally
have been
locally destroyed.
destroyed. The
tary features
features have
part of the
scanty
scanty outcrops show
show that
that the lower part
formation consists
matrix-supported conglomconsists of matrix-supported
(Gms) with mica-rich arkosite matrix.
erate
matrix. The
erate (Gms)
elasts
clasts are angular or subrounded
subrounded and mainly
mainly consist of pebble- and cobble-size
cobble-size granitoids, gneisses,
242
vo1canics,
volcanics, red jasper, laminated iron-formation,
iron-formation,
schists
schists and quartzites.
Quartzitic
(S-), 1-10
l-10
Quartzitic interbeds of sand facies (S-),
m
m thick,
thick, showing
weak stratification
showing weak
stratification and
and containing pebbly
pebbly layers
layers with
with normal- and
and inversegrading and cross-stratification
cross-stratification also
also occur.
occur. Bedforms
forms are commonly
commonly planar and the contacts of
the beds
beds are
are often
often sharp.
The better exposed upper-part of the formation
Geological Survey of Finland,
Finland, Special
Special Paper 55
Proterozoic fluvial
fluvial deposits
Early Proterozoic
deposits in
in the
the Pyhätunturi area,
area, northern Finland
Finland
is characterized by upward-coarsening
upward-coarsening cyeles
cycles often
tens of metres thick (Fig. 4). They start with massive or weakly stratified
stratified units of conglomerate
conglomerate bed(SG + GB) that contain boulders, cobbles and
sets (SG
pebbles and are overlain by units of arkosite bed(SB). Contacts between the cyeles
sets
sets (SB).
cycles are
are often
sharp and erosion
al (Fig. 5).
erosional
5). Normal and inverse
graded beds with transitional contacts appear inside the
the cyeles.
side
cycles. Clast-supported conglomerates
conglomerates
(Gm) dominate but matrix-supported
matrix-supported conglomerconglomerates (Gms) are also found. Tabular, horizontally
stratified beds (GB) 50 cm to 5 m thick and conprobably hundreds of
laterally for tens or probably
tinuing laterally
metres are common, but massive beds up to 20 m
thick also exist. The arkosic interbeds between the
conglomerate
conglomerate cyeles
cycles are
washed out
are often
often washed
out or
present only
only as
as remnants.
remnants.
The matrix of the conglomerates
camicaconglomerates is often mi
rich mediummedium- or coarse-grained arkose. The diamphenoelasts is commonly
eter of the phenoclasts
commonly 5-15 cm (Fig.
6)
6) but
but ranges
ranges from
from some
some centimetres
centimetres to
to half a
phenoclast material
metre. The phenoelast
principally
material consists principally
quartzites (80(80-90
of
90 0/0),
9o), but
but vein
of dissimilar
dissimilar quartzites
jaspilite,
quartz, jaspilite, granitoids and volcanics are also
common.
common elasts
clasts throughout the
common. The most common
quartzite
formation are those of greenish coloured quartzite
of the
the Lapponia Supergroup. All the
the elasts
clasts are
*""t4.V
LlTHOLITHO FACIES
FAC IE S
INTERPRETATION
I NTERPRETATI ON
Gm
Sr
FI
Q.n,/t
I
rtr.
G
m [;Q~~?::5=tt
Gm
Sr
Sp
Gm
\n / I
"Y" / t
Sp
~~~~~
^
mlnor
mtnor
channel
chonnel
Gm
t.^.
bar-edge
^,.t^^
wur - sugv
superimposed
supen mposeo
bars
bors
Sn
Gm
100
Sr
Sh,zp
debris
ftow
debris flow
donncitq
deposits
Gm
Sn
superlmposed
superimposed
no rq,
bars
Gm
Sn
m
o0
debris
flow
debrrs
ftow
)^^^-,+deposits
ugpv>rL>
Gms
Fig. 4.
4. Schematic
Schematic section
interpreted lithofacies
lithofacies and sedimensection with interpreted
sedimentary process across the
the fluvial
fluvial Isokuru Formation. Karelia
Karelia SuperSupergroup, Pyhätunturi area.
(1978)..
area. Letters refer to
to Miall
MiaU (1978)
W\
r'
,"W&
major
mojor
channel
chonneI
"''ry'
t*gfl'
*"
'
Fig. 5.
bases (broken
(broken lines)
lines).. Top towards
towards left. Upper part of Isokuru Formation,
Upward-fining sequences
sequences with erosional bases
5. Upward-fining
Karelia
Karelia Supergroup, Pyhätunturi area. Photo by authors.
243
Geological Survey of Finland, Special
Special Paper 5
Jorma Räsänen
Mdkelö
Rtistinen and Merja Mäkelä
Jorma
quartzite belonging
Fig. 6.
6. A partly elast-supported
clast-supported conglomerate
conglomerate.. The elasts
clasts within the arkosic matrix mainly consist of quartzite
to the Lapponia
Photo by authors.
Lapponia Supergroup. Upper part of Isokuru Formation, Karelia Supergroup
Supergroup,, Pyhätunturi area
area.. Photo
(Fig.. 7). They are comrounded or well-rounded (Fig
monly strongly lineated, especially the flat elasts
clasts
of
of mica
mica schist,
schist, the
the amount
amount of
which decreases
of which
decreases
upwards.
upwards.
The conglomerates contain interbeds of arkosite
bedsets (SB), which usually occupy the upper parts
of the conglomerate cyeles
cycles whose tops are often
eroded.
eroded. Composite bedsets up to
to 15-20
l5-20 m thick
Fig.
Fig. 7.
7. A stratified conglomerate
quartzite. Upper part of Isokuru
conglomerate consisting of well-rounded
well-rounded pebbles of the Lapponian quartzite.
Formation, Karelia
Karelia Supergroup, Pyhätunturi area. Photo by authors
authors..
244
Geological
Geological Survey
Survey of
of Finland,
Finland, Special
Special Paper
Paper 55
Early Proterozoic
Proterozoic f1uvial
fluvial deposits
yhät unturi area,
Early
deposits in
in the
the PPyhätunturi
area, northern
northern Finland
are found
found only
locally. Massive,
are
only 10caIly.
Massive, horizontaIly
horizontally
stratified beds (Sh), up to 5 m thick, are common
stratified
graded, laminated
and may
may contain
contain graded,
and
laminated layers
layers with
(Sr)
ripple marks (Sr) on the
the top.
top. The
The thickness
thickness of aa
graded stratum
stratum commonly varies
single graded
varies between
and 10
l0 cm
cm.. Crossbeds
Crossbeds display both planar (Sp)
22 and
(St). The
and trough crossbedding
and
crossbedding (St).
The most
most typical
sedimentary structures are gently sloping crossbeds
(Ss/Se)
erosional
(Ss/
Se) with erosion
al basal contacts. The trough
pebbles that
crossbedded units (St) often contain pebbles
may form
form layers
layers up
may
up to
to 30
30 cm
cm thick
thick and
and some
(FllFsc).
muddy
muddy flasers
flasers (FIIFsc).
The
The elastic
clastic texture of the
the cross-stratified interpreserved with
is weIl
beds
beds is
well preserved
with subangular
subangular or
or subrounded,
rounded, medium- to
quartz and
to coarse-grained
coarse-grained quartz
and
feldspar elasts.
clasts. The matrix is often biotite-rich and
may contain smaIl
small schist fragments
fragments.. The horizontaIly
tally stratified beds are better sorted than the crossstratified ones. They contain weIl-rounded
well-rounded elasts,
clasts,
quartz,
mostly quartz, which are usuaIly
usually fine- to mediumgrained and
and occur in
in aa mica-bearing matrix.
Interpretation
Interpretation
part of
The lower
lower part
The
of the
the Isokuru
Isokuru Formation
Formation is
mainly composed of matrix-supported
matrix-supported conglomerates (Gms) and arkosite interbeds (S-), which are
often strictly
strictly local.
often
sediments are characterized by the maAlluvial sediments
trix-supported conglomerates
conglomerates regarded as
as debris
(Collinson
flow deposits
deposits (CoIlinson 1978). Other
flow
Other principal
fan deposits are rapid downfeatures of alluvial fan
facies changes
slope
slope facies
changes together
together with
with debris
debris flows
(Miall 1970).
l97O). The
The debris
(Miall
debris flows
flows commonly lack
internal stratification,
but inverse
internal
stratification, but
inverse and
and normal
grading are typicaIly
(Nielsen
grading
present (Ni
elsen 1982).
typically present
1982).
debris flows
flows associated
In paraglacial fans the debris
associated
glaciers, and
and derived from
from earlier glacially
with glaciers,
detritus, are relatively
relatively abundant and may
eroded detritus,
(e.g. Ryder
show
beds (e.g.
b, Rust
show stratified beds
Ryder 1917a,
l9l7a, b,
r97s).
1975).
In proximal environments, debris
In
debris flows commonly
monly form thick,
thick, often
often upward-coarsening sequences. The subcycles
quences.
subcyeles ranging from
from 10 to 25
25 m
may be overlain by a thinner upward-fining subal. 1977,
sequence (Steel et ol.
1977, Heward 1978).
The upper
The
upper part
part of the
the Isokuru
Isokuru Formation is
characterized
elast-supported
conglomerates,
char acterized by clast-s
upported conglomerates,
interbedded with quartzites
quartzites
which, in general, are interbedded
and
are
interpreted
as
ancient
river
deposits
river deposits in
and are interpreted as
1978).
origin (Collinson 1978).
Most typical
typical of
of the study
study area are the cyclic
cyelic deMost
posits composed of conglomerate (GB or SG
SG +
(SB) units. These features
features are
GB) and arkosite (SB)
common in large
large trunk
trunk rivers, where tabular
tabular bodies
common
(GB} are commonly interbedded with
of gravels (GB)
lenses, sheets, blankets or wedges of sandy units
(SB) (Miall 1985).
conglomerates (Gm or Gm
Gm + Gms) with
The conglomerates
contacts at the base of the cycles
cyeles
erosional basal contacts
overlain by arkosites
arkosites (St, Sp, Sr, Se, Ss) conconare overlain
(Fsc/FI) (Fig. a).
4). By analanaltaining muddy flasers (Fsc/Fl)
ogy with Miall (1985), these are typical features
channel-fill deposits.
of channel-fill
elast-supported conconThe great majority of the clast-supported
glomerates (Gm) in the upper part of the ConglomConglomerate Formation refer to bar deposits of proximal
(e.g. MiaIlI977,
braided rivers (e.g.
Miall 1977, 1978, Rust
Rust 1972,
generally longi1978a, b).
b). These gravel bars
bars are generaIly
tudinal (Boothroyd and Ashley
Ashley 1975) and horizontally
bedded,
but
thick
tally bedded,
thick massive
massive bedding is
is also
common, as verified by several authors e.g. Rust
(1975) and
and Rust and Koster
Koster (1984).
The horizontally stratified, tabular
tabular conglomerate
beds that
that probably extend
extend for
for hundreds
hundreds of
ate beds
met
res are interpreted as longitudinal bars
metres
bars.. They
are most common among gravel bars
bars (e.g.
(e.g. Rust
1972, Smith 1974)
1974) and
and may be hundreds of metres
(Miall 1977). They are stable bedforms
long (MiallI977).
bedforms at the
flood stage when the wh
oIe bedload is in motion
whole
(Rust 1978b).
(Rust
The arkosite beds (Sh, Sp, St) at the top of each
upward-fining cyc1es
cycles inc1ude
include planar cross-stratified
(Sp)
horizontally
stratified
(Sp) and
(Sh) sands
horizontally
and
stratified (Sh)
sands with
so
me muddy flasers (Fig. 4).
some
a). They are interpreted
as
products of downstream progressions resting
as products
on gravels (Gm) (e.g. Miall
Miall1978,
1978, Brady 1984), and
even the coarsest
coarsest gravel successions contain sand
facies whereas mud facies is only sporadically
sporadically pre(Miall 1985). Hence, these arkosite
served (MiaU
arkosite beds are
indicative
of
slack
water
deposits,
being either barindicative
deposits, being
Rust 1972,
1972,
edge sand wedges or microdeltas (cf. Rust
Miall
1977).
Miall 1977).
scarcity of
of muddy flasers (Fsc/Fl)
(Fsc/FI) in these
The scarcity
cyeles indicates the rarity of mud
conglomerate cycles
facies (F-).
(F-). In the present study area the flasers
facies
arkosites
are always associated with crossbedded arkosites
(Se + Ss) at the top of
of cycles
cyeles and are interpreted
interpreted
(Se
as scour fills. This is a common feature of proxiassociated
mal rivers, too, where mud layers are associated
only with abandoned
abandoned channels, which commonly
commonly
only
have multistorey fills (e.g. Miall 1985).
summary, the lower part
part of
of the Isokuru
Isokuru ForIn summary,
mation mainly containing debris
debris flow
flow deposits
mation
interbeds (S-) refers to proxi(Gms) and arkosite interbeds
mal alluvial fan deposits. It also indicates an as245
24s
Geological Survey of Finland, Special
Special Paper 5
Jorma
Räsänen and
Mäkelti
and Merja Mäkelä
Jorma Rristinen
paraglacial alluvium
with ancient
sociation
sociation of
of paraglacial
alluvium with
glaciofluvial
glaciofluvial deposits
by Rust
Rust and
deposits as
as described
described by
(1984).
Koster (1984).
The upper parts of the lsokuru
Isokuru Formation, composed mainly
mainly of clast-supported gravels (Gm) overlain by sandy bedsets (Sp, St,
St, Sr) exhibit features
similar to
those
observed
by
Rust (1975) in
in the
to those
by Rust
gravelly
braided river
gravelly braided
river deposits
modern paradeposits of modern
glacial environments. They also resemble the deposits
posits typical
very large
large streams,
typical of
of very
streams, e.g.
e.g. trunk
rivers,
Rust and Koster
Koster (1984).
rivers, as
as described by
by Rust
(1977, 1978,
According to
to Miall
Miall (1977,
1978, 1985),
1985), most
gravelly rivers tend to
to show aa proximal to distal
gradation of fluvial styles.
gradation
PYHÄ
TUNTURI FORMATION
PYHATUNTURI
Geological setting and
and description
The 1600-1900
Pyhätunturi Formation
1600-1900 m thick pyhätunturi
rests on the lsokuru
Isokuru Formation without observed
unconformity (Fig.
(Fig. 8)
8).. The lowermost part conunconformity
sists of arkosic quartzite only 5-6
thick. The
5-6 m thick.
rock
rarely contains wellrock is
and rarely
is coarse-grained
coarse-grained and
qüartzrounded quartzitic
pebbles . The bulk of
quartzitic pebbles.
the quartzof the
ites
medium to
to coarseites are
homogeneous and
and medium
are homogeneous
grained (diameter 0.2-1.0 mm).
grained
mm). They
They are
are very
pure, pink to white in colour and contain detrital,
detrital,
well-rounded
well-rounded tourmaline, zircon and opaque grains
as accessory minerals. Feldspars are rare and the
clastic texture is well-preserved
well-preserved.. The matrix (15 to
20
20 070)
Vo) consists mostly of quartz and
and sericite.
A highly peculiar feature throughout
throughout the Pyhä-
tunturi
Formation is
is the
the alternation of
of planar
tunturi Formation
cross-stratified beds (Sp) and horizontal
horizontal stratified
stratified
beds (Sh) with ripple marks (Sr) (Fig. 9).
9). What is
more the tabular beds (SB) commonly
commonly continue for
more than aa hundred metres laterally.
laterally.
The cross-stratified sets are between 20 cm and
160
being 75
75 cm
160 cm thick, being
cm on
on average, and
and disboth angular
play both
play
angular and
and tangential
tangential cross-bedding
cross-bedding
(Fig.
(Fig. 10).
l0). The cross-stratified sets are commonly
commonly
overlain
overlain by
by simple sandy
sandy bedsets
bedsets showing hori(Sh +
zontal
marks (Sh
zontal lamination and
and ripple marks
+ Sr).
Their thickness varies between
between 0.5 cm and
l5 cm,
and 15
cm.
and that of single beds between 1I mm and 5 mm.
Both symmetrical and asymmetrical ripple marks
;i!'
Fig.
pyhätunturi Formation (right). Karelia
Isokuru Formation (left) and the Pyhätunturi
Fig. 8.
8. Contact
Contact between the Isokuru
Karelia Supergroup, PyhätunPyhätunturi area.
area. Photo by authors.
authors.
246
Geological
nd , Special
Geological Survey
Survey of
of Finla
Finland,
Special Paper
Paper 55
Early Proterozoic
Early
Proterozoic fluvial
fluvial deposits
deposits in
in the
the Pyhätunturi area,
northern Finland
area, northern
Finland
?:A
't:'#:
*rj
Fig.. 9.
9. Cross-stratified
Cross-stratified and horizontally stratified
Fig
stratified tabular, sandy
sandy bedforms.
bedforms. Note thin
thin., shallow scour
fill in the centre. Length
Length of white
white scale bar
bar 1.5
part of P
yhätunturi Formation, Karelia
1.5 m
m.. Lower part
Pyhätunturi
Supergroup
Supergroup,, Pyhätunturi area. Photo by authors.
LITHOFACII ES
FAC
Sp
+ St
sP*si
Sh+Sr
Sh
+ Sr
Sp
II NTERPRETA
TION
NTERPR ETATI
ON
~~
'-
Sh
So
Sh
-- ---
PLANAR
AND RIPPLES
PLANAR BED
BED FLOW
FLOW AND
~~
Sp
Sh
Q.t
Sn
St ++ vF
Sp
vr
Sh+ Sr
Sp
r-...."""- """-."-...",,,,-
SUPERIMPOSED TRANSVERSE
SUPERIMPOSED
AND
AND L1NGUOID
LINGUOID BARS
BARS
~
SCOUR
SCOUR FILL
,..... ' - ' - ........
................ ----...
SUPERIMPOSED TRANSVERSE
TRANSVERSE
SUPERIMPOSED
AND
AND L1NGUOID
BARS
LINGUOID BARS
Sh + Sr
Sh+Sr
10
Sp
Sh+ Sr
Sh*Sr
......
,..... ...... ,..... '-
Sp
Sh
"-'r-......'r-......"--. '-
Sp
::..----............-...............
~
/
, ...... "
PLANAR BED
BED FLOW
FLOW AND
AND RIPPLES
RI PPLES
PLANAR
SUPERIMPOSED TRANSVERSE
SUPERIMPOSED
AND LINGUOID
L1NGUOID BARS
BARS
AND
Sh+ Sr
Sh*
m
m
00
Sh
r-
10. Detailed
Detailed cross-section of the lower part of the Pyhätunturi
Pyhätunturi Formation
Formation showing
showing the lithoFig. 10.
fades and interpreted
interpreted sedimentary
sedimentary process.
process . Note the association of horizontally
horizontally stratified
stratified (Sh) and
facies
cross-stratified beds (Sp). Karelia Supergroup,
Supergroup, Pyhätunturi
pyhätunturi area. Letters
Letters refer to Miall (1978).
(1978).
cross-stratified
247
247
Ceological Survey
Survey of
of Finland,
Finland, Special
Special Paper
Paper 55
Geologieal
Jorma Räsänen
Röscinen and
Merja Mäkelä
Mdkelö
and Merja
Jorma
. Asymmetrie
Fig.
Fig. 11
11.
Asymmetric eurrent
current ripples on
on top of
of a horizontal, laminated bed. Lower
part of Pyhätunturi Formation, Karelia Supergroup,
Pyhätunturi area. Photo by
Supergroup, pyhätunturi
authors.
authors.
(Fig. 11).
met with
with (Fig.
are
are met
I l). According to
to the
the ripple
p.59),
(Collinson and Thomson
Thomson 1982,
1982, p.
index (CoUinson
59), cur: 7.5-16.8)
(RI =
7.5-16.8) dominate, but wave
rent ripples (RI
ripples (RI < 6)
6) occur,
too. SmaU-scale
ripples
occur, too.
Small-scale trough
(Se,
crossbeds
rare
Ss) are
are rare and
and solitary.
crossbeds (Se, Ss)
(Sp) and mascrossbeds (Sp)
Consisting of planar crossbeds
(Sh), some large slumping and
sive beds
sive
beds (Sh),
and sliding
structures (Fig. 12),
l2), associated
structures
associated with primary slips
and highly
highly deformed
deformed sandy
sandy bedsets
and
bedsets are
are found.
l3) there are bedBetween the deformed units (Fig. 13)
sets, 10-150
l0-150 cm thick, consisting of cross-straticross-stratisets,
fied beds (St/Sp) overlain by horizontal stratified
(Sh). Some
beds (Sh) in the
beds
beds (Sh).
Some wavy stratified beds
upper part of the Pyhätunturi
Pyhätunturi Formation
(Fig. 14)
Formation (Fig.
l4)
include tangential, very low-angle
low-angle cross-stratified
beds (St) commonly associated
plan ar crossassociated with planar
beds (Sp).
beds
The crossbeds indicate aa unimodal palaeocurpalaeocurrent direction
direction to the north-northwest
north-northwest (Fig.
(Fig. 15).
l5). The
current
ripples suggest
the same
current ripples
suggest almost
almost the
same main
palaeocurrent direction.
direction.
Interpretation
The Pyhätunturi
pyhätunturi Formation
Formation is characterized
characterized by
tabular beds (SB), which are a common
common feature
feature
in distal braided
braided river
river deposits
deposits where
where tabular sandy
bedlbrms
bedforms (SB) are dominant (Miall
(MiaU 1985).
1985). FurtherFurthermore, in this formation the planar
plan ar cross-stratified
cross-stratified
beds (Sp) are often associated with horizontally
horizontaUy
stratified
Sr). According to Miall
MiaU
stratified beds
beds (Sh
(Sh + Sr).
(1977,
(1977, 1978), this is a typical feature of deposits
of
of sandy rivers, as is the association
association of
of wavy
wavy strastra(Sh)
tified
beds
with
low-angle
tified beds (Sh) with low-angle stratified
stratified beds (St).
(St).
planar
The
The plan ar cross-stratified
cross-stratified beds (Sp)
(Sp) have
have been
been
interpreted
trans verse and linguoid
linguoid bars, which
interpreted as transverse
are the most typical deposits of sandy braided
rivers (e.g. Smith 1971,1972,
1971, 1972, Miall
MiaU 1977). These
These
planar
planar beds,
beds, with
with aa thickness
thickness of
of 20-160
20-160 cm,
cm, concontinue
metres laterally
lateraUy - which
which is
is anantinue for tens
tens of metres
-transverse and
other
other characteristic
characteristic feature
feature of
of transverse
and
linguoid
linguoid sand
sand bars
bars (Miall
(MiaU 1977).
1977). Hence
Hence sandy
sandy rivers
rivers
differ from
from gravelly
graveUy rivers,
rivers, where
where longitudinal
longitudinal
gravel
gravel bars
bars dominate
dominate (Rust 1972).
1972).
Requirements
Requirements for
for the
the formation
formation of
of bar
bar deposits
deposits
248
are a continuous supply of sedimentary material
moderate depth of
of water (Smith l974,Miall
1974, MiaU
and a moderate
According to Miall
MiaU (1981), transverse bars
1977). According
Therehave straighter crests than linguoid ones. Theredomifore it is likely that transverse bars are the domiPyhätunturi. FineFinenant type in the quartizites of Pyhätunturi.
grained, sorted sedimentary
sedimentary material
material favours the
formation of
of transverse bars with
with peculiar
peculiar downformation
stream structures (Smith 1970). However, without
study of
of palaeocurrents
palaeocurrents (Miall
(MiaU 1977),
detailed study
a detailed
lg77), irit
distinguish between these
these two bar
is difficult to distinguish
types.
horizontal stratified beds (Sh) wirh
with ripple
ripple
The horizontal
lamination
lamination (Sr) commonly
commonly overlie
overlie the
the cross-straticross-stratito Miall
MiaU (1977),
(1977), when
fied beds (Sp). According to
the water
water level
level is falling
faUing and the
the current
current abating,
abating,
the
bar deposits
deposits are
are followed
foUowed by
by horizontal
horizontal beds
beds (Sh)
(Sh)
bar
and ripples
ripples (Sr)
(Sr) indicating
indicating aa lower
lower flow regime.
regime.
and
have been
been described
described by
by Miall
MiaU
Similar structures have
(1981)
(1981) and Smith (1971)
(1971) from the
the top
top of bars.
bars.
The
The wavy
wavy stratified
stratified beds
beds (Sh)
(Sh) containing
containing lowlow-
Geological Survey of Finland, Special paper 5
Early Proterozoic fluvial deposits in the pyhätunturi area, northern Finland
rn
~
-<
:,0
~
~
o
N
o
;:;.
:::l
c::
<:
a
0.
.g
o
~.
M
'"
5·
::r
0
'"
0
Ö
(JQ
(SO
'" .,
"CVl
c::
:r ....
'<
s::.,l:
<
M
c::
'"
'<
g 0
c:: ....,
:!. "T1
~ [
'" .,:l
.,
0.
:l
o
,l
.i
a
a
ö0
o
c/)
o
M
B
o
-.1
6
o
o
>
u
{
-
b0
o
o
'
o0
a
a
N^
Fig. 12. A large synsedimentary sliding structure with deformed beds. Sliding towards right. Length of white scale bar 1.5 m. Lower part of Pyhätunturi Formation, Karelia Supergroup, Pyhätunturi area.
Photo by authors .
o Vl
::l
"0
'" e.._.
:r'"
....
(")
:l
_. .,
., '"
'Tl "C
249
N
~
'Cl
=-"0
:l ....
0. v.
Paper 55
Geological Survey
Finland,, Special
Special Paper
Survey of
of Finland
Mtikeki
Rdsdnen and Merja Mäkelä
Jorma
Jormo Räsänen
-
LlTHOLITHO
FACIES
FACIES
INTERPRETATION
;NTERpRETAT;ON
Sh
Jrl
Sh+Sp
Sh
Sp
Sh
Sh*Sp ä>i
shSp F€
Sh =----_l
SU
BAOUEOUS DEFORMATION
SUBAOUEOUS
DEFORMATION
TRANSVERSE
TRANSVERSE AND
AND LlNGUOID
LINGUOID BARS
PLAN
AR
BED
BED FLOW
FL.W
PLANAR
Sp SS==
Sp
N
Sr
RI
PPLES
RIPPLES
Sr
Sp
Sh +Si
Sh+Sr
'o I
10
TRANSVERSE AND
NGUOI D BARS
AND LI
LINGUOID
SP R<<== TRANSVERSE
LAG
DEPOSTT
lno DEPOSIT
E*#
Sh+Sp
Sh *SP f-<i--.+1 SUBAOUEOUS
DEFORMATION
SUBAOUEOUS DEFORMATION
Sp
Gm
Gm
ch
Sh
vvj
l-
PLAN
AR BED
PLANAR
BED FLOW
Sh +Sp
Sh+Sp
äJ
o
m
PLANAR BED
PLANAR
PPLES
BED FLOW
FLOW AND
AND RI
RIPPLES
Sh+ Sr
Fig.
Fig. 13.
13. Detailed cross-section
cross-section of the middle part of the Pyhätunturi Formation showing the lithofacies and interpreted
structures, Karelia
Karelia SuperSuperinterpreted sedimentary process. Note occurrence of deformed structures.
group, pyhätunturi
Pyhätunturi area.
LITHO LITHOFACI E S
FACIES
Sp
Sh
st
St
Sh
Sh+Sr
Sh +Sr
Sp
Sh+Sp
Sh
Sp
Sh+St
Sh+Si
INTERPRETATION
INTERPRETATION
~
---'-
:--=
---
~::::::-.....
-.....
:::::
~
---
SUPERIMPOSED
SUPERIMPOSED TRANSVERSE
AND LlNGUOID
AND
LINGUOID BARS
DUNES
PLANAR BED
BED FLOW
FLOW AND
PLANAR
AND RIPPLES
SAND
SAND
WAVES
WAVES
~
~
PLANAR
PLANAR BED
BED FLOW
Sh
Sp
~:::z:
st
St
10
DUNES
DUNES
.~-.............~-.....
Sp ~"'"""~~
~
Sh
Sp
SUPERIMPOSED TRANSVERSE
TRANSVERSE
SUPERIMPOSED
AND
AND LINGUOID
LlNGUOID BARS
BARS
.::----.....
"'---- :::::--=
*sh
Sp+Sh
sp
Sh
--
PLANAR
PL AN AR BED
BED FLOW
FLOW
m
m
00
14. Detailed
Detailed cross-section of the upper
upper part of the Pyhätunturi
Pyhätunturi Formation showing the lithoFig. 14.
process. Note association between linguoid
linguoid and planar bedforms. Karelia
facies and interpreted process.
Supergroup, Pyhätunturi
Pyhätunturi area.
area.
Supergroup,
250
Geological
Geological Survey
Survey of
of Finland,
Finland, Special
Special Paper
Paper 55
pyhätunturi area,
Early Proterozoic
Proterozoic fluvial
fluvial deposits
Early
deposits in
in the
the Pyhätunturi
area, northern
northern Finland
N
PYHATUNTURI
PYHÄTUNTURI
PALEOCURRENT
n:55
sS
pyhä15.
Fig. 15
. Palaeocurrent rose of
the Pyhäofthe
tunturi Formation, showing
tunturi
showing broad
broad unimodal direction towards northwest. Karelia Supergroup, Pyhätunturi area
lia
area..
angle cross-stratified beds (St) in association
association with
planar cross-stratified beds
(Fig. 14)
(Sp)
(Fig.
beds
l4) are indunes.. They are common features of
terpreted as dunes
(Miall 1985),
sandy streams (MiaU
1985), and usuaUy
usually occur in
the shaUower
shallower parts of channels
channels in association with
transverse bars or sand waves as described by Blod(1980).. The rare smaU-scale
gett and Stanley (1980)
small-scale trough
crossbeds (Se, Ss) in the Pyhätunturi
Pyhätunturi quartzites are
interpreted as
interpreted
as scour fills.
bars are
are frequent deTransverse and linguoid bars
posits in braided rivers. They are found particularly in a sandy, exceptionaUy
exceptionally broad and shallow
river type lacking weU-defined
well-defined topographic differentation
(MiaU
ferentation between active and inactive areas (Miall
1977,1981,
1970,1971,
1977, 1981, Smith 1970, 1971, Asquith & Cramer
1975). They are
1975).
aU dominated by Sp
Sp lithofacies
lithofacies
are all
and
and have
have little or
or no
no internal
internal cyclicity.
The Sp
cyclicity. The
lithofacies
superimposed sets
sets of sand
lithofacies consists of superimposed
waves and transverse and
/ or linguoid bars, many
and,/or
of which are capped by Sr and Fllithofacies.
Fl lithofacies. These
are represented by the migration of fields
fields of sand
waves and bars with bar top facies deposited durdur(Smith 1970,
ing falling water level (Smith
1970, 1971
l97l and
and 1972).
1972\.
The
The St
lithofacies is
St lithofacies
is sparse,
sparse, reflecting
reflecting the
the rarity
(Miall 1982).
of deep
deep channels (MiaU
1982).
The slumping structures and deformed bedsets
of the
the Sp
Sp and
and Sh
Sh lithofacies
lithofacies suggest subaqueous
subaqueous
deformation.
deformation. If
If the
the sediments
sediments deposited
deposited very
rapidly,
rapidly, the
the sedimentary
sedimentary structures
structures might
might have
been
been disturbed. However, these
these features are not
common
common in
in aa braided
(Miall
braided river
river environment
environment (MiaU
1984). In contrast, slumps, slides and extensional
extensional
faults are more common
common in river-dominated deltas
(Coleman et al.
al. 1983, Winkler
Winkler and Edwards 1983).
This is attributed to the instability and oversteepening
ing caused by aa high input of sedimentary
sedimentary material into the
rial
the basin.
The deformed bedsets at pyhätunturi
Pyhätunturi are always
overlain
by horizontal stratified beds, including
overlain by
some cross-stratified beds. They fill ancient, un(Fig. 12)
even surfaces (Fig.
gravel lag
12) and
and at least one gravellag
(Fig. 13).
is
is associated with them (Fig.
l3). These
These features
indicate channel-fill
channel-fill deposits (Hopkins 1985), but
because other characteristic features
features of channel
structures
structures are not found they are regarded as disturbed, layered bar structures probably associated
with the
the channels.
The Pyhätunturi Formation
Formation has many similariti
es to
recent braided
braided river
ties
to recent
river deposits,
deposits, especially
those studied by Smith (1970 and 1971)
l97l) and Blodgett and Stanley (1980). The vertical profiles
profiles suggest
gest the
the Platte type
type of MiaU
Miall (1977 and
and 1978) in
which bar deposits are dominant.
dominant. On the basis of
architectural-element analysis
the architectural-element
analysis of Miall (1985),
resemble a sandy
sandy type with sandy
these quartzites resemble
bedforms, SB, as the dominant
dominant element. The Pyhätunturi Formation
Formation has many
many features similar to
the model of broad and
and shallow,
shaUow, low-sinuosity
low-sinuosity
the
an abundant
abundant sand bedload destreams carrying an
(1985).
scribed by Crowley (1983) and MiaU
Miall (1985).
DISCUSSION
DISCUSSION
In the present work the models of fluvial deposits
posits are based on
on modern analogies.
analogies. The behaviour
of Proterozoic
Proterozoic fluvial systems may, howhaviour of
drastically different
different from that of
ever, have been drastically
present-day ones (Long
(Long 1978). The lack of land
vegetation
vegetation alone during
during the Proterozoic
Proterozoic may
may have
have
made conditions different from what thev
they have
have
been more recently.
recently.
interpreThe palaeoanalyses are based on the interpresedimentary structures
structures and vertical
vertical and
tation of sedimentary
lateral profiles. Although
Although the Pyhätunturi area
area is
lateral
weU exposed, extensive areas are covered,
covered,
rather well
the lateral
lateral continuity of large
large sedimentary
sedimentary
and the
structures can seldom
seldom be observed. On rare occastructures
complete
sions, outcrops offer opportunities for complete
three-dimensional analyses. As Miall
MiaU (1985)
(1985) warns,
wams,
three-dimensional
251
Geological Survey of Finland, Special
Special Paper 5
Jorma Rdsdnen
Räsänen and Merja Mäkeki
Mäke/ä
small-scale
from limited
limited outcrops
small-scale observations from
may lead to classification
classification of aa facies assemblage
as a small- or medium-scale
medium-scale structure, whereas it
is
is in
in reality part of aa higher ranking structure.
In the
the Pyhätunturi area aa conglomerate over(Mielikainen 1979). The lowermost
lies mica schists (Mielikäinen
lowermost
part of this conglomerate, the lower part
part of the
part
Isokuru Formation, is, however, poorly exposed
and the contact is
is covered.
covered. The topmost part of
the
is also
the pyhätunturi
Pyhätunturi Formation is
also covered,
covered, and
its contact with the Kiimaselkä Formation is seen
only in a drill core.
core. Despite these drawbacks, the
sedimentology
sedimentology of the supracrustal
supracrustal rocks can be interpreted.
Alluvial conglomerates,
which the
conglomerates, of which
the Isokuru
Formation is
regarded as
is an
an example,
example, are
are regarded
as indicators
relief resulting
resulting from
cators of
of sharp
sharp terrestrial
terrestrial relief
lithospheric
lithospheric uplift. Many of these successions are
thick, suggesting
suggesting their formation in a tectonically
tectonically
(e.g. Miall
influenced
influenced setting
setting (e.g.
Miall 1970,
1970, Steel
Steel et
et al.
1977). Most ancient fan successions show distinct
cyclicity, ascribed to periodic tectonism, and the
ancient
braidplains also owe their origin to tectonic
ancient braidplains
causes
l98l). Migration of the active and
causes (Miall 1981).
inactive tracts can result in cyclic sedimentary
sedimentary sequences
quences (Rust and
Koster 1984).
1984).
and Koster
Alluvial fan deposits are usually formed
formed adjacent to fault scarps or to regions of high relief and
hence they are more local accumulations than the
widespread braidplain
braidplain deposits, which, according
according
to Rust and Koster (1984), are formed in response
to
to major
major tectonic
tectonic uplift.
As in
in the
the Pyhätunturi Formation, fluvial distributary
tributary channels in fluvial-dominated delta plains
(Elliot 1978) are
by unidirectional
are characterized
characterized by
flow with periodic
periodic stage fluctuations and are therefore similar to channels in strictly alluvial systems.
systems.
These channel-fill
channel-fill deposits are frequently upwardfining sequences,
sequences, which, however, are uncommon
in
in the
the quartzites of Pyhätunturi.
Pyhätunturi. Upward-coarUpward-coarsening cycles or sequences - the most charactercharacteristic feature of river-dominated
river-dominated deltaic sediments
sediments
(Miall 1976) or delta front sediments
sediments (Elliot 1978)
- are also alm
ost entirely
almost
entirely lacking in the Pyhätun- area. The
turi
characteristic
characteristic features of tide-dominated delta plains, including
bimodality in the flow
including bimodality
direction
direction and a frequency of small-scale facies variations
ations in a vertical sense (Elliot
@lliot 1978), are also lacking in
the
Pyhätunturi
Formation.
in the
All the
atulian formations north of the
the JJatulian
the Central Lapland Granite Complex, which runs from
Salla to Kittilä
Kittilä (Fig. 1),
l), are sedimentologically
sedimentologically very
(Kortelainen et
similar
to each
similar to
each other
other (Kortelainen
et al.
al. 1986).
They are characteristically
characteristically very thick and mainly
consist
of fluvial
fluvial conglomerates
consist of
conglomerates and
and quartzites
parts of them
overlain
by siltstones.
me parts
overlain by
siltstones. So
Some
them are
(Räsänen
thought
be deltaic
thought to
to be
deltaic accumulations
accumulations (Räsänen
1977,
1977, Haimi
Haimi 1977
1977 and
Kortelainen 1983).
and Kortelainen
1983). They
often exhibit
exhibit unimodal
unimodal palaeocurrent distributions,
with the main
main mode to the north
north or west-northwest. Therefore,
Therefore, they differ distinctly from the underlying Lapponian quartzites, which show a considerable
variation in
in facies
facies assemblages and
siderable variation
and a
palaeocurrent distribution,
rough bimodal-bipolar
bimodal-bipolar palaeocurrent
distribution,
suggesting
provenance was in the north
suggesting that their provenance
(Editors'note:
(Nikula 1985, Räsänen 1986).
note: see
1986). (Editors'
see
also
also Nikula, this volume)
The JJatulian
atulian formations in the Central
Central Lapland
Belt form
Schist
Schist Belt
form aa long
long and
and narrow
narrow zone.
zone. The
underlying Lapponia Supergroup
Supergroup contains terrestrial metasediments overlain by aa thick sequence
metavolcanics, suggesting formation in an
of metavolcanics,
an inatulian
rift system
tracontinental rift
system setting.
setting. The
The JJatulian
formations in this area overlie unconformably
unconformably the
Lapponian sequence and
be associated
and seem
seem to
to be
associated
with
with ancient failed
failed rifts.
The JJatulian
atulian successions
successions in the Kuusamo
Kuusamo Schist
Belt
Belt also
also mainly
mainly rest
rest on
on the
the Lapponian supracrustal sequence but in the south they deposited
directly on the Archaean Basement
Basement Complex (Silvennoinen 1972,
1973, 1985). The existence
1972,1973,1985).
existence of Lapponian supracrustal rocks has
ponian
has not yet been verified in
in the
fied
the Peräpohja
Peräpohja Schist
Schist Belt,
Belt, where
where in
in the
south of the area, the Jatulian formations partly
lie on the Archaean basement and partly
partlyon
on layered
(Perttunen 1985).
intrusions
intrusions (perttunen
1985).
CONCLUSIONS
Early Proterozoic JJatulian
atulian conglomerates
conglomerates and
the
overlying
quartzites
in
the
in the Pyhätunturi area
the
represent ancient fluvial deposits. On the basis of
the main lithofacies associations
associations the fluviatile succession is divided into the Isokuru Formation
Formation with
aa lower and upper member
member and
and the pyhätunturi
Pyhätunturi
Formation.
252
The poorly sorted
sorted lower member of the Isokuru
Formation consists
Formation
matrix-supported, polyconsists of
of matrix-supported,
mictic conglomerates and mica-rich arkosite interbeds. It displays features suggestive of alluvial fan
deposits with
with debris
deposits
debris flows
flows and
and water-laid
water-laid sediments.
Distinct interbedding
Distinct
interbedding of clast-supported con-
Geological
Ceological Survey
Survey of
Finland, Special
of Finland,
Special Paper
Paper 55
Early Proterozoic
Proterozoic fluvial
Early
fluvial deposits
deposits in
in the
the Pyhätunturi area,
area, northern
northern Finland
glomerates with
with arkosite
arkosite beds
glomerates
beds characterizes
characterizes the
upper member of the Isokuru
lsokuru Formation. The beds
form upward-fining cyelic
form
cyclic sequences
sequences often with
bases. Tabular gravelly beds
erosional bases.
beds are
are dominant in
in the
the formation.
formation. On
nant
On the
the basis
basis of its
its composition
and
sedimentary
position and sedimentary structures,
structures, the
the upper
member is interpreted as a proximal, gravelly river
deposit. The
The abundance
quartzite elasts
abundance of
of quartzite
deposit.
clasts and
their roundness indicate moderate
moderate maturity
their
maturitv and
previously reworked material.
The Isokuru Formation is
is overlain by the mamature, homogeneous Pyhätunturi Formation. The
ture,
The
contact between the formations is sharp and probably erosional. The most common features of the
quartzites are
quartzites
are tabular
tabular sandy
sandy bedforms.
bedforms. Crossbedded
bedded sheets
sheets are
are dominant
dominant and
and alternate
alternate with
horizontal-bedded
horizontal-bedded sheets
sheets and
and wavy-Iaminated
wavy-laminated
sheets. The fairly stratified sequences, principalsheets.
ly consisting of mediummedium- to fine-grained
fine-grained and wellquartz elasts,
rounded
rounded quartz
clasts, refer to the
the uniformity of
the stream and the high maturity of the
the sedimentary material.
material. The
The Pyhätunturi Formation is
is interpreted as a distal deposit of an ancient braided
river.
ACKNOWLEDGEMENTS
ACKNOWLEDGEMENTS
impetus to this work was given by the sediThe impetus
mentological studies carried out by Professor Kaumentological
ko Laajoki, who also visited the study area and
ko
encouraged us with his good advice and ideas. We
encouraged
are also grateful to colleagues Esko Korkiakoski
and
Vesa Perttunen
Perttunen for
and Vesa
for critically
reading the
critically reading
manuscript. The figures were drawn by Ms. Marjatta
jatta Kanste.
REFERENCES
REFERENCES
1982. The
Alapieti, T.,
T., 1982.
The Koillismaa layered igneous
igneous compgeochemistlex, Finland - its structure,
structure, mineralogy
mineralogy and geochemist- on the distribution
ry, with emphasis
distribution of chromium. Geol.
Surv. Finland, Bull. 319,
Surv.
319, 116
l16 p.
Asquit, G.B.
G.ß. & Cramer,
Cramer, S.L., 1975. Transverse
Transverse braid bars
in the Upper Triassie
Triassic Trujillo
Trujillo Sandstone of the Texas
Texas panhandle.
handle . J.
Geo!. 83,
657-661.
J. Geol.
83,657-661.
Blodgett,
ßlodgett, R.H. &
& Stanley, K.O., 1980. Stratification,
Stratification, bedforms and discharge
discharge relations of the Platte braided river
system, Nebraska. J.
J. Sedim. Petrol. 50,
system,
50, 139-148
139-148..
Boothroyd,
ßoothroyd, J.C.
J.c. & Ashley, G.M., 1975. Processes,
Processes, bar
bar mormorphology and sedimentary structures on braided outwash
fans,
fan s, northeastern Gulf of Alaska. In Jopling, A.V.
A.V . and
McDonald, B.D.,
B.D., eds., Glaciofluvial
Glaciofluvial and glaciolacustrine
glaciolacustrine
sedimentation. Soc. Econ. Paleontol. Mineral. Spec. Publ.
sedimentation.
23, 193-222.
t93-222.
23,
Brady,
1984. Neogene
ßrady, R.H.
R.H. 1984.
Neogene stratigraphy of the Avawatz
Avawatz
Mountains between the Garlock and
and Death
Death Valley fault
zones, southern Death Valley, California:
California: implications
implications as
38, 127-158
to Late Cenozoic tectonism. Sedim. Geol. 38.
127-158..
Coleman,
Coleman, J.M., Prior, D.B,
D.ß. & Lindsay,
Lindsay, J.F., 1983. Deltaic
Deltaic
influences on shelfedge
shelfedge instability
instability processes.
processes . SEMP Spec.
Spec.
Publ.
Pub!. 33.
33, l2l-137.
121-137.
J.D., 197E.
1978. Alluvial
Alluvial Sediments.
Sediments. Pp.
Pp. l5-60
15-60 ln
in
Collinson, J.D.,
Sedimentary
Sedimentary Environments
Environments and
and Facies,
Facies, ed.
ed . by
by H.G.
H .G.
Reading, Blackwell Sci.
Sei. Publ. Oxford.
Oxford .
Collinson,
J.D. &
& Thompson, D.8.,
D.B., 19E2.
1982. Sedimentary
Collinson, J.D.
London, 194 p.
George Allen & Unwin, London,
Structures. George
Crowley, K.D., 1983.
1983. Large-scale bed configurations
configurations (macro(macroCrowley,
Platte River Basin, Colorado and Nebraska: PriPriforms), Platte
mary
mary structures
structures and formative
formative processes. Geol. Soc. Am.
Bull. 94.
94,117-133.
ll7-133.
Elliot, T., 1978.
197E. Deltas. Pp.
Pp. 97-142 in
in Sedimentary EnviReading. Blackwell Sei.
ronments and Facies, ed. by H.G. Reading.
Sci.
Publ. Oxford
Oxford..
ß., 1978.
Gaal, G., Mikkola, A. & Söderholm,
Söderholm,8.,
197E. Evolution of
Gaä|,
the Archean
Archean crust in
Prec. Res.
Res. 6,
in Finland. Prec.
6, 199-215.
Hackman,
Pre-Quarternary rocks. Sheet C6, RoHackman, V., 1910. Pre-Quarternary
vaniemi. General
of Finland. 1I :: 400 000.
geological map of
General geological
- , 1914,
till bergartkartan
bergartkartan C6-85-86,
C6-B5-B6,
1914, ßeskrivningen
Beskrivningen till
-, Rovaniemi-Torneä-Övertorneä.
Rovaniemi-Torneä-Övertorneä . General geological
geological map of
Finland, 1I ::400
400 000.
Finland.
- , 1918. Vuorilajikartan selitys. Lehdet C6-B5-B6, Rova-, niemi-Tornio-Ylitornio.
niemi-Tornio-Ylitornio . Suomen
Suomen geologinen yleiskartta,
yleiskartta,
: 400 000.
I1 :400
- , 1927. Studien
Studien über den Gesteinsaufbau
Gesteinsaufbau der Kittilä-LappKittilä-Lapp-,1927.
mark . Bull. Comm. göol.
geol. Finlande
Finlande 79,
79, 106
p.
mark.
lO6 p.
M., 1977. Luoston
Luoston alueen
alueen geologia. Manuscript, Dept.
Dept.
Haimi, M,,1917.
Geol. Univ.
Univ . Helsinki.
Geol.
M., 1949.
On the
the Stratigraphical and
and Structural
Structural
Härme, M.,
1949. On
Geology of
of the Kemi
Kemi area,
area, Northern
Northern Finland,
Finland, Bull.
Bull. Comm.
Comm .
Geology
geol. Finlande
Finlande 147, 60 p.
p.
göol.
Heward, A.P., 1978. Alluvial
Alluvial fan sequence and megasequence
megasequence
Heward,4.P.,
models: with
with examples from Westphalian
Westphalian D - Stephanian
Stephanian
models:
sedimentology,
coalfields , Northern Spain. In Fluvial sedimentology,
B coalfields,
A .D. Miall. Can. Soc. Pet. Geol.
Geol. Mem. 5,669-702.
5, 669-702.
ed. by A.D.
1985. Channel-fill
Channe1-fill deposits formed by agHopkins, J.C., 1985.
deeply scoured, superimposed
superimposed distributaries
distributaries
gradation in deeply
of the Lower
Lower Kootenai
Kootenai Formation
Formation (Cretaceous).
(Cretaceous). J. Sedim.
Sedim.
of
Petrol. 55,
Petrol.
55. 42-52.
Juopperi, H. &
& Veki, 4.,
A., 1986.
1986. On
On the
the Archean
Archean Tuntsa
Tuntsa SuperSupergroup in the Nuolusvaara
Nuolusvaara area,
Northern Finland. AbAbarea, Northern
stracts, l7e
17e Nordiska Geologmötet,
Geologmötet, Helsingfors, p. 66.
66.
stracts,
ja LevituntuLevituntuKortelainen, V., 1983. Sirkka-konglomeraatin
Sirkka-konglomeraatin ja
Kortelainen,
253
Finland, Special
Paper 55
Geological
Geological Survey
Survey of
of Finland,
Special Paper
Jorma
Jorma Räsänen
Rdstinen and Merja Mäkelä
Mökelö
rin
Kittilässä. Manuscript, Dept.
rin kvartsiitin sedimentologia
sedimentologia Kittilässä.
Helsinki.
Geol.
Geol. Univ.
Univ. Helsinki.
M., RasLehtonen, M.,
Kortelainen, V., Mäkelä, M., Nikula, R., Lehtonen,
19E6. latul-formationernas
tas,
P. &
Räsänen, J., 1986.
Jatul-formationernas sedimentas, P.
& Räsänen,
l7e Nordiska
tologi i Finska Central Lappland. Abstracts, 17e
p. 76.
Geologmötet,
Helsingfors, p.
Geologmötet, Helsingfors,
granitoid and schist
Lauerma, R., 1982. On the ages of some granitoid
Finland. Bull. Geol. Soc.
Soc. Finland,
complexes in
in northern Finland.
54. 85-100.
54,85-100.
Proterozoic volcano - sediLehtonen, M., 1986. An Early Proterozoie
mentary
mentary succession in Central Lapland, Northern Finland.
p. 96.
l7e Nordiska Geologmötet,
Ceologmötet, Helsingfors, p.
Abstracts, 17e
Rastas, P.,
P., Väänänen,
Väänänen, J.,
Lehtonen, M.,
M., Manninen,
Manninen, T.,
T., Rastas,
Lehtonen,
19E5. Keski-Lapin
Keski-Lapin geologisen
Roos, S.1.
S.I. &
& Pelkonen, R., 1985.
Explanation to
kartan
and discussion:
discussion: Explanation
kartan selitys.
selitys. Summary and
Lapland. Geol. Surv.
the
map of Central Lapland.
Surv. Finthe geological map
71, 56
land, Rep
Rep.. Invest.
Invest. 71,
56 p.
land,
Long, D.G.F., 1978. Proterozoic stream deposits: some problems
lems of
of recognition
recognition and
and interpretation of ancient sandy
ed. by
by A.D.
nuvial
In Fluvial
fluvial systems. 1n
Fluvial Sedimentology, ed.
Miall.
Pet. Geol.
Mem. 5,
5. 313-341.
Miall. Can
Can.. Soc.
Soc. Pet.
Ceol. Mem.
fans, Prince of Wales
Miall, A.D., 1970. Devonian alluvial fans,
Petrol. 40,
40, 556-571.
Island, Arctic Canada. 1.
J. Sedim
Sedim.. Petrol.
556-571.
lsland,
-,1976. Facies Models
Models 4. Deltas. Geosci. Can
Can.. 3, 215-227
215-227 ..
-,1976.
A Review
Review of the
the braided river deposition
depositional
- , 1977. A
al envi-, ronment.
Rev. 13,
13, 1-62.
l-62.
Sci. Rev.
ronment. Earth Sei.
- , 1978.
1978. Lithofacies types
types and
vertical profile models
models in
and vertical
-, braided
rivers
rivers:: a summary. In
1r Fluvial Sedimentology, ed
ed..
A.D. Miall. Can. Soc. Pet. Geol. Mem
Mem.. 5,
by A.D.
5,597-604.
597-604.
- , 1981. Alluvial sedimentary basins:
basins: tectonic setting and
-, basin
In Sedimentation and
basin architecture.
architecture. In
and Tectonics
Tectonics in
Alluvial Basins, with Examples
Examples from North America,
America, ed
ed..
by A.D.
A.D. Miall. Geol. Assoe
Assoc.. Can. Spec.
Spec. Pap. 23,
23,l-33.
1-33.
AAPG
- , 1982. Analysis of Fluvial Depositional
Depositional Systems. AAPG
-, Education
Education Course Note Serie,
75 p.
Serie, 75
- , 1984. Principles
Principles of Sedimentary
Sedimentary Basin Analysis
Analysis.. SpringerSpringer-,19E4.
Verlag, New
New York, 490
490 p.
19E5. Architectural-element
Architectural-element analysis:
analysis: aa new method of
- , 1985.
-, facies
analysis applied to fluvial deposits.
deposits. Earth Sei.
Sci. Rev.
22,
26r-308.
22, 261-308.
Mielikäinen,
Mielikäinen, P. 1979. Pre-Quaternary rocks. Sheet
-3642-PelSheet-3642-Pelkosenniemi.
kosennierni. Geological map of Finland,
Finland , 1I : 100 000.
000 .
Mikkola,
Mikkola, E., 1937. Pre-Quarternary rocks. Sheet C7, Sodankylä.
kylä . General geological map of Finland,
Finland, 1I : 400 000.
7941. Kivilajikartan
-C7 -D7 ,,
-,1941.
Kivilajikartan selitys.
B7-C7-D7
selitys. Lehdet - Sheets B7
-, Muonio-Sodankylä-Tuntsajoki.
Muonio-Sodankylä-Tuntsajoki . English summary: Explanations to the
rocks, 286
286 p.
the map of rocks,
Nielsen, T.H., 1982. Alluvial fan deposits.
deposits. 1n
In Sandstone
Sandstone depositional
& D.R.
position al environments
ed. by
by P.A.
P .A. Scholle &
environments,, ed.
Spearing.
Spearing. Am.
Am . Assoc.
Assoe . Petroleum Geol. Mem.
Mem . 31
, 49-86.
31,49-86.
Nikula,
Nikula, R., 1985. Sodankylän VirttiöVirttiö- ja
ja Värttiövaaran metasedimenttien
tasedimenttien paleosedimentaatioympäristöt.
paleosedimentaatioympäristöt. Manuscript,
Dept. Geol.
Geol. Univ.
Univ. Oulu.
Oulu.
Perttunen, V., 1985.
19E5. On
On the
the Proterozoic stratigraphy and
exogenic
of the Peräpohja
Peräpohja area.
area . 1n
In Proterozoic
Proterozoic
exogenic evolution of
exogenic processes and related metallogeny,
metallogeny, ed. by K. LaaLaajoki
joki & J.
1. Paakkola.
Paakkola . Geol. Surv.
Surv . Finland, Bull. 331, l3l131l4l.
141.
Räsänen,
J., 1977. Kaarestunturi-muodostuma
Kaarestunturi-muodostuma ja
ja sen straRäsänen, J.,1977.
tigrafinen
tigrafinen sijainti Keski-Lapin
Keski-Lapin liuskejaksossa.
liuskejaksossa. Manuscripr,
Manuscript,
Dept.
Dept. Geol. Univ. Helsinki.
- , 19E4.
1984. On the Archean and Proterozoic
Proterozoic komatiites
komatiites in the
-, Savukoski
Savukoski area,
area, NE-Finland.
NE-Finland . Abstracts,
Abstracts, l6e
16e Nordiska
Nordiska
Geol.
Geol. Vintermötet, Stockholm, p.
p. 189.
19E6.
1986. On
On the
the Lapponia Quartzites
Quartzites in
in the
the SodankyläSodankylä-- Savukoski
17e Nordiska
Savukoski area, Northern
Northern Finland.
Finland . Abstracts.
Abstracts, l7e
Geologmötet,
1986,
Geologmötet, Helsingfors
Helsingfors Universitetet
Universitetet 12.-15. 5. 1986,
p.
p. 166.
166.
2s4
254
Räsänen, J.,
Hanski, E.
E. &
& Lehtonen, M.,
M., 1986.
19E6. Komatiites
J., Hanski,
and tholeiites in
in the Möykkelmä area,
area, Northern
Northern Finland.
Abstracts,
l7e Nordiska
Nordiska Geologmötet, Helsingfors UniAbstracts, 17e
p. 167.
versitetet, p.
167.
Rust,
process in
Rust, B.R.,
8.R., 1972.
1972. Structure
Structure and
and process
in aa braided river.
Sedimentology, 18,221-245.
18, 221-245.
gravels. In
- , 1975.
1975, Fabric
Fabric and
and structure
structure in
in glaciofluvial gravels.
1n
-, Glaciofluvial
and
and glaciolacustrine sedimentation, ed.
ed. by
A.V.
A.V. 10pling,
B.C. McDonald. Soc.
Jopling, and
and B.C.
Soc. Econ.
Econ. Paleontol.
238-248.
tol. and
and Mineral.
Mineral. Spec.
Publ. 23,
23,238-248.
Spec. Publ.
- , 1978a.
l91Ea, A
A c1assification
classification of
of alluvial channel
channel systems.
systems. In
In
-, Fluvial
sedimentology, ed.
ed. by Miall. Can. Soc.
Pet. Geol.
Soc. Pet.
Mem.
Mem. 5,
5, 187-198.
- , 1978b.
1978b. Depositional
Depositional models
models for
for braided
braided alluvium.
alluvium. In
-, Fluvial sedimentology,
ed.
ed. by Miall
Miall.. Can.
Can. Soc. Petroleum
Geol.
605-625.
Geol. Mem.
Mem. 5,
5,605-625.
Rust, B.R. &
19E4. Coarse Alluvial Deposits.
& Koster, E.H., 1984.
Deposits.
In Facies Models,
In
Models, ed.
Walker. Second Edition.
ed. by
by R.G.
R.G. Walker.
Geosci.
Geosci. Can.
Can. Repr.
Repr. Ser.
l, 53-69.
Ser. I,
Ryder,
Ryder, J.M.,
J.M., 1971a. The
The stratigraphy
stratigraphy and
and morphology
morphology of
paraglacial alluvial fans
fans in
in south-central British Colum279-298.
bia.
bia. Can.
Earth Sei.
Can. 1.
J. Earth
Sci. 8,
8,279-298.
- , 1971b. Some aspects
aspects of the morphology of paraglacial
-, fans in
in south-central British Columbia.
Columbia. Can. 1.
J. Earth Sei.
Sci.
8,
8. 1252-1264.
t252-1264.
4.,1972.
Silvennoinen,
1972. On the stratigraphie
Sifvennoinen, A.,
stratigraphic and
and structural
structural
geology of the
the Rukatunturi area,
area, northeastern Finland.
Finland.
Geol.
Geol. Surv.
Surv. Finland, Bull.
Bull. 257,
257, 48
48 p.
- . A.,
1973. Pre-Quarternary
Pre-Quarternary rocks.
rocks. Sheet - 4524+4542
4524+4542
-. - 4.,Kuusamo.
Geological Map of Finland,
Finland,- II : 100 000.
- , 1985. On the Proterozoic
Proterozoic Stratigraphy
Stratigraphy of Northern Fin-, land.
land,. In Proterozoie
Proterozoic exogenic processes and related metallogeny, ed. by K. Laajoki &
& 1.
J. Paakkola. Geol. Surv. Finland, Bull.
land,
Bull. 331,
331, 107-116.
107-116.
Silvennoinen, A.,
4., Honkamo, M., Juopperi, H., Lehtonen,
Lehtonen,
M., Mielikäinen, P., Perttunen,
PerUunen, V., Rastas, P., Räsänen,
J. &
Väänänen, J., 1980. Main features of the stratigraphy
& Väänänen,
of north Finland.
Finland. Pp
Pp.. 153-162
153-162 in
ln latulian
Jatulian Geology
Ceology in the
Eastern Part of the Baltic
Baltic Shield, ed. by A. Silvennoinen
Silvennoinen..
Proceedings of aa Finnish-Soviet
Proceedings
Finnish-Soviet Symposium held in Finland
land 21st-26th
2lst-26th August, 1979.
for Scientific
1979. Committee
Committee for
Scientific
and
and Tecnical Co-operation
between Finland and
Co-operation between
and Soviet
Soviet
153-162 .
Union. Rovaniemi.
Rovaniemi. 153-162.
Union.
Simonen,
Simonen, A.,
4., 1980. The Precambrian
Precambrian in Finland. Geol. Surv.
304, 58 p.
Finland, Bull. 304,
Smith, N.T., 1970.
1970. The braided stream deposition
al environdepositional
ment: comparison of
Silurian
of the Platte River with some Silurian
c1astic
North-Central Appalachians. Geol. Soc.
Soc. Am.
clastic rocks, North-Central
81,2993-3013
Bull. 81,
2993-3013..
- , 1971. Transverse
Transverse bars and braiding in the Lower Platte
-,1971.
River, Nebraska. Geol. Soc. Am.
Am . Bull.
Bull . 82,
82,3407-3419.
3407-3419.
- , 1972.
Some sedimentological aspects
aspects of planar cross1912, Some
-, stratification
stratification in a sandy braided river.
river. 1.
Sedim . Petrol.
Petrol.
J. Sedim.
42,
42, 624-634
624-634..
- , 1914,
1974. Sedimentology
Sedimentology and
and bar
bar formation
formation in the upper
-, Kicking
J. Geol.
Horse River, a braided outwash stream. i.
205-223.
82, 20s-223.
82.
Spinnangr,
Steel, R.J., Maehle, S., Nilsen, H., Roe, S.L. & Spinnangr,
A., 1971
1977.. Coarsening-upward
Coarsening-upward cycles in the alluvium of
4.,
Hornelen
Hornelen Basin (Devonian), Norway: sedimentary
sedimentary response
response
to tectonic
tee tonic events. Geol. Soc. Am. Bull. 88,
88, 1124-1134.
WeHn, E., Christiansson,
Christiansson, K. & Nilsson, Ö., t970.
1970. Rb-Sr age
age
Welin,
dating of intrusive
intrusive rocks of
of the Haaparanda
Haaparanda suite. Geol.
Fören . Stockholm Förh.
Förh . 92,
92, 336-346.
Fören.
Winkler, C.D. &
& Edwards,
Edwards, M.B. 1983. Unstable progradaprogradaSEMP Spec. Publ. 33, 139c1astic shelf margins. SEMP
tional clastic
157 ..
t57