Jukka Marmo

The Early Proterozoic glaciogenic anddeep weathering geologic record in northern Karelia,

eastern Finland

Espoo 1993

Jukka Marmo

The Early Proterozoie glaeiogenie and deep weathering geologie reeord in northern Karelia,

eastern Finland

Espoo 1993

The Early Proterozoic glaciogenic and deep weathering

geologic rccord in northern Karelia, eastern Finland.

Jukka Marmo

Division of Geology and MineralogyDepartment of GeologyUniversity of Helsinki

ro be presented, *,,0")!j#,,::;::;-.ty orscience ortheUniversity of Heßi*i, for public criticism in l*cture

Room I of the Depamnent of Geology,on May l4th, 1993, at noon

Geologian tutki muskeskusEspoo 1993

The Early Proterozoie glaciogenie and deep weathering

geologie record in northern Karelia, eastern Finland.

Jukka Marmo

Division of Geology and Mineralogy Department of Geology University of Helsinki

Academic Dissenation

To be presented, with the pennission of the Faculty of Science of the University of Helsinki , for public criticism in Lecture

Room 1 of the Depanment of Geology, on May 14th, 1993, at noon

Geologian tutkimuskeskus Espoo 1993

Cover: Koli National Park, core of the study area. In front: typical white aluminousquartzite et Ukko-Koli. Photo: the author.

rsBN 951-69G5084Helsinki 1993Yliopistopaino

Cover: Koli National Park, core of the study area. In front: typical white aluminous quartzite at Ukko-Koli . Photo: the author .

ISBN 951-690-508-0 Helsinki 1993 Yliopistopaino

To Sinikka, Saara and AnttiTa Sinikka, Saara and Antti

Marmo, J. 1993. The Early Proterozoic glaciogenic and deep weathering geologic record in NorthemKarelia, Eastem Finland. Academic dissmaüon, Universiry of Helsinki, Finlatd.

Early Proterozoic Seriola and Jatuli Groups have been studied in the Koli-Keltimo area that forms the

northeastern part of the North Karelia Schist Belt in eastem Finland. The age of the studied sequence

can be bracketed between 2.5 - 2.2 Ga. The study confirms the presence of Prejatulian deposits in the

aree, and, reporrs glaciel deposits and ancient soil formation. In sddition, the origin of quartzites,

oxidation-reduction of the paleoatmosphere, ceuses for drastic climate changes and regional correlations

have been studied.

Separated from the Archeen Basement by a nonconformity, the Sariola Group (thickness 330m) consists

of poorly to moderately sorted arkose and conglomerate, with minor siltstone and argillite. The basal

units were deposited in alluvial conditions. These were followed by glaciomarine diamictons, silts and

muds with dropstones, turbidites, and finelly, by glaciofluvial outwash plain deposits. The wholesequence is correlated with the volcanic-sedimentary rocks ofKainuu, northem Finland and Karelis ofRussia that formed during the 2.45 Ga rifting. A peneconlemponaeous major glaciation for the KareliaCraton is suggested.

The Jatuli sandstone and conglomerate are generslly moderately to well sorted varying in theircompositional maturity. The basal units (maximum thickness 30Om) underlain by quartz-sericite schistconsist of a lower aluminous quartzile, an upper conglomerete and quartz conglomerate end quartzite.

The quartz-sericite schist (thickness 80m) is interpreted as a paleosol. The original soil developed onboth Archean granitoids and Early Proterozoic glaciogenic rock. Relative to its parents, the paleosol isconsistently depleted in ferrous iron, sodium, calcium and magnesium. In the upper most throughlyweathered portions, ferric iron and potassium decrease, in some profiles consirerably. Silica and aluminaconstitute nearly all of the uppermost paleosol; alumina reaches 30 %. Chemical reduction characterizedthe weathering, until shortly before the soil became partially eroded and buried.

The overlying aluminous sediments were derived from paleosol and deposited in braided rivers as

proximal poorly sorted aluminous detritus and more distal braidplain sediments. The chemicel maturityand great thickness of the paleosol and associated sediments record intense chemical weathering underwarm and humid climate, comparable to a modem tropical climate. The deep weathering generatedenonnous amounts of soil consisting of residual quartz and clay that were reworked and deposited as

aluminous sediment. Presented evidence strongly favours a single cycle origin for the quartzite. Thedeep weathering probably spanned the entire area of the Karelia Craton, beceuse other paleosolsassociated with quartzite in similar stratigraphic position are scattered across eastem part of theFennoscandian Shield.

The preserved geologic record indicates a drastic climate change, that is, given climatic mning, inaccordance with recent paleomagnetic studies. Also global climate change may have been involvedassuming a causal connection between 2.45 Ga magmatic event, major glaciation and green house effect-type deep chemical weathering. The weathering apparently acted as a sink for carbondioxide and otherreactive aerosols released into the atmosphere during magmatic activity.

Key words (GeoRef Thesaurus, AGI): metasedimentary rocks, lithostratigraphy, paleosedirrenüology,deposition, chemical weathering, glaciation, paleosols, chemical composition, Proterozoic, Koli,Kaltimo, Finland.

Jukl<a Marmo, Geological Survey of Finland, SF42|5O Espoo, Finland

ISBN 951-690-508-0

Manno, J. 1993. The Early Proterowic glaciogenic and deep weathering geologie record in Northem Karelia, Eastem Finland. Academic dissertation, University 0/ Helsinki, Finland.

Early Proterozoie Sariola and Jatuli Groups have been studied in the Koli-Kaltimo area that forms the northeastem part of the North Karelia Schist Belt in eastem Finland. The age of the studied sequence can be bracketed between 2.5 - 2 .2 Ga. The study confirms the presence of Prejatulian deposits in the area, and, reports glacial deposits and ancient soil formation. In addition, the origin of quartzites, oxidation-reduction of the paleoatmosphere, causes for drastic c\imate changes and regional correlations have been studied.

Separated from the Archean Basement by a nonconformity , the Sariola Group (thickness 330m) consists of poorly to moderately sorted arkose and conglomerate, with minor siltstone and argillite. The basal units were deposited in alluvial conditions. These were followed by glaciomarine diamictons, silts and muds with dropstones, turbidites, and finally, by glaciofluvial outwash plain deposits . The whole sequence is correlated with the volcanic-sedimentary rocks of Kainuu, northem Finland and Karelia of Russia that formed during the 2.45 Ga rifting . A penecontemponaeous major glaciation for the Karelia Craton is suggested '

The Jatuli sandstone and conglomerate are generally moderately to weil sorted varying in their compositional maturity. The basal units (maximum thickness 300m) underlain by quartz-sericite schist consist of a lower aluminous quartzite, an upper conglomerate and quartz conglomerate and quartzite. The quartz-sericite schist (thickness 80m) is interpreted as a paleosol. The original soil developed on both Archean granitoids and Early Proterozoie glaciogenic rock. Relative to its parents , the paleosol is consistently depleted in ferrous iron, sodium, calcium and magnesium. In the upper most throughly weathered portions, ferric iron and potassium decrease, in some profiles consirerably. Silica and alumina constitutenearly all ofthe uppermost paleosol ; alumina reaches 30%. Chemical reduction characterized the weathering , until shortly before the soil became partially eroded and buried.

The overlying aluminous sediments were derived from paleosol and deposited in braided rivers as proximal poorly sorted aluminous detritus and more distal braidplain sediments. The chemical maturity and great thickness of the paleosol and associated sediments record intense chemieal weathering under warm and humid c\imate, comparable to a modem tropical c\imate. The deep weathering generated enormous amounts of soil consisting of residual quartz and c\ay that were reworked and deposited as aluminous sediment. Presented evidence strongly favours a single cyc\e origin for the quartzite . The deep weathering probably spanned the entire area of the Karelia Craton, because other paleosols associated with quartzite in similar stratigraphie position are scattered ac ross eastem part of the Fennoscandian Shield.

The preserved geologie record indicates a drastic c\imate change, that is, given c\imatic zoning, in accordance with recent paleomagnetic studies. Also global c\imate change may have been involved assuming a causal eonnection between 2.45 Ga magmatie event, major glaeiation and green house effect­type deep chemical weathering. The weathering apparently aeted as a sink for earbondioxide and other reaetive aerosols released into the atmosphere during magmatie aetivity.

Key words (GeoRef Thesaurus, AGI) : metasedimentary rocks, lithostratigraphy, paleosedimentology, deposition, ehemieal weathering, glaeiation, paleosols, ehemieal eomposition, Proterozoie, Koli, Kaltimo, Finland .

Jukka Manna, Geological Survey 0/ Finland, SF-02J50 Espoo, Finland

ISBN 951-690-508-0

INTRODUCTION

The study area is called Koli-Kaltimo area and located in the north-eastem part of the

Early Proterozoic North karelia Schist Belt. The two lowermost associations of the

craton cover sequence have been studied; the Sariola Group, and, the Hokkalampi

Paleosol and the related aluminous, quartzitic metasediments of the Jatuli Group. The

age of these units can be bracketed between 2500 ma and 2200 ma, which are the U-

Pb ages for the I:te Archean granitoids and mafic intrusions in the metasediments,

respectively.

This study is based on fieldwork and exploration carried out in the study area during

1980 - 1987. Between 1980 - 1984 the Geological Survey of Finland (GSF)

investigated a huge aluminum silicate deposit of the Hokkalampi area. This work was

followed by a GSF project for evaluation of paleoplacer gold potential (1985 - 1987)

of the study area, and, a simultaneous GSF and University of Oulu joint project related

to economic geology.

Sedimentological work was mainly carried out as detailed mapping along profiles

across the sedimentary sequences. Despite of deformation and metamorphism the

primary features of the excellently exposed rocks are generally well preserved.

Environmental interpretations for the sedimentary rocks are based on lithofacies

associations, whereas for the paleosol, geological setting, and, mineral and chemical

compositions of its profiles were the decisive factors.

The study has been presented in the following papers, which papers deal with

stratigraphy, sedimentology, composition and environmental interpretations of the

lower Proterozoic Sariola and Jatuli Groups in North Karelia, eastem Finland:

1. Marmo, JS., Ojakangas, R.W. (1984) Lower Proterozoic glaciogenic deposits,

eastern Finland. Geol. Soc Am Bull95. 1055-1062.

INTRODUCTION

The study area is called Koli-Kaltimo area and located in the north-eastern part of the

Early Proterozoie North karelia Schist Belt. The two lowermost associations of the

craton cover sequence have been studied; the Sariola Group, and, the Hokkalampi

Paleosol and the related aluminous, quartzitic metasediments of the Jatuli Group. The

age of these units can be bracketed between 2500 ma and 2200 ma, which are the U­

Pb ages for the Late Archean granitoids and mafic intrusions in the metasediments,

respectively.

This study is based on fieldwork and exploration carried out in the study area during

1980 - 1987. Between 1980 - 1984 the Geological Survey of Finland (GSF)

investigated a huge aluminum silicate deposit of the Hokkalampi area . This work was

followed by a GSF project for evaluation of paleoplacer gold potential (1985 - 1987)

of the study area, and, a simultaneous GSF and University of Oulu joint project related

to economic geology.

Sedimentological work was mainly carried out as detailed mapping along profiles

across the sedimentary sequences. Despite of deformation and metamorphism the

primary features of the excellently exposed rocks are generally weil preserved.

Environmental interpretations for the sedimentary rocks are based on lithofacies

associations, whereas for the paleosol, geological setting, and, mineral and chemical

compositions of its profiles were the decisive factors.

The study has been presented in the following papers, which papers deal with

stratigraphy, sedimentology, composition and environmental interpretations of the

lower Proterozoie Sariola and Jatuli Groups in North Karelia, eastern Finland:

1. Manno, JS., Ojakangas, R. W. (1984) Lower Proterozoic glaciogenic deposits,

eastern Finland. Geol. Soc Am BuH 95, 1055-1062.

t

2. Marmo, JS. (198O Sariolan stratigraphy and sedimentation in the

Koli-Kaltimo area, North Karelia, eastern Finland. In.' Shokolov V (ed) Proc.

Symp. Lower Proterozoic formations in the eastern part of the Baltic Shield.

Petrozavodsk, 1985, pp. 149-190.

3. Marmo, JS., Kohonen, JJ., Sarapää, O., Aikäs, O. (19tt) Sedimentology and

stratigraphy of the Lower Proterozoic Sariola and Jatuli Groups in the

Koli-Kaltimo area, eastern Finland. GSF Spec Pap 5: 11-28.

4. Marmo, JS. (1992) The Lower Proterozoic llokkalampi Paleosol in North

Karelia, eastern Finland. In.' Schidlowsky, M., Golubic, S., Kimberley, MM.,

Trudinger, P.A. (eds) Early Organic Evolution: Implications for Mineral and

Energy Resources, Spinger-Verlag, Berlin Heidelberg: 4l-66.

REVIEW OF THE PAPERS

Paper I is the f,rrst description of Early Proterozoic glaciogenic deposits on the

Fennoscandian Shield. The interpretion was based on presence of the association of

diamictite and dropstone bearing siltstone-argillite having a gradational contact with

eachother. The unit was named the Urkkavaara Formation, and, as the formation is

overlain by a metaregolith which in turn underlies the Jatuli quartzite, the existence

of Prejatulian rocks in the area was confirmed. In the previous studies the lowermost

(Ga^ 1964, Piirainen 1968) quartzite had been interpreted as basal proterozoic

sedimentary unit.

Within the Urkkavaara Formation, four informal members that grade into eachother

were described consisting of three depositional facies, as follows: lower siltstone-

argillite member, graded sandstone member, upper siltstone-argillite member and

diamictite member.

The up to 60 meters thick Urkkavaara Formation was interpreted as glaciomarine

sediments and the model of deposition including the interpreted glacial advance and

retreat, was presented. Sedimentation was probably the result of suspension fallout,

2

2. Manno, JS. (1986) Sariolan stratigraphy and sedimentation in the

Koli-KaItimo area, North Karelia, eastern Finland. In: Shokolov V (ed) Proc.

Symp. Lower Proterozoic fonnations in the eastern part of the Baltic Sbield.

Petrozavodsk, 1985, pp. 149-190.

3. Manno, JS., Kohonen, JJ., Sarapää, 0., Äikäs, O. (1988) Sedimentology and

stratigraphy of the Lower Proterozoic Sariola and Jatuli Groups in tbe

Koli-Kaltimo area, eastern Finland. GSF Spec Pap 5: 11-28.

4. Manno, JS. (1992) The Lower Proterozoic Hokkalampi Paleosol in North

Karelia, eastern Finland. In: Schidlowsky, M., Golubic, S., Kimberley, MM.,

Trudinger, P.A. (eds) Early Organic Evolution: Implications for Mineral and

Energy Resources, Spinger-Verlag, Berlin Heidelberg: 41-66.

REVIEW OF THE PAPERS

Paper 1 is the first description of Early Proterozoic glaciogenic deposits on the

Fennoscandian Shield . The interpretion was based on presence of the association of

diamictite and dropstone bearing siltstone-argillite having a gradational contact with

eachother. The unit was named the Urkkavaara Fonnation, and, as the formation is

overlain by a metaregolith which in turn underlies the Jatuli quartzite, the existence

of Prejatulian rocks in the area was confirmed. In the previous studies the lowermost

(GaaI 1964, Piirainen 1968) quartzite had been interpreted as basal Proterozoic

sedimentary unit.

Within the Urkkavaara Formation , four informal members that grade into eachother

were described consisting of three deposition al facies, as follows : lower siltstone­

argillite member, graded sandstone member, upper siltstone-argillite member and

diamictite member.

The up to 60 meters thick Urkkavaara Formation was interpreted as glaciomarine

sediments and the model of deposition including the interpreted glacial advance and

retreat , was presented. Sedimentation was probab1y the result of suspension fallout,

3

turbidity currents, and iceberg rafting in front ofa grounded or floating glacier. It was

tentatively suggested, that if all of the lonestone-bearing units associated with

diamictites in Soviet Karelia, that occur in similar stratigraphic position, prove to be

glaciogenic deposits, they may indicate an Farly proterozoic, continent scale

glaciation.

In Paper 2, the immature metasediments enveloping the Kontiolahti dome in the north

were all interpreted as prejatulian, because the rocks were observed to grade upwards

into the metaregolith. The rocks were described, the Sariola Group several hundreds

of meters thick was established, through defining the formations included. The lower

contact of the Sariola group is a well-defined nonconformity. In addition, the

metaregolith was reported, preliminary described and named as the Hokkalampi

Formation.

The sporadically exposed basal arkoses and conglomerates overlain by the rocks ofthe

Url&avaara Formation, were named as the Ilvesvaara Formation. The upper contact

is poorly exposed and the thickness of the unit is estimated not to exceei 30 metres.

The sediments were interpreted as alluvial deposits related to faulting. The mineral

composition sediments of the Ilvesvaara resembles that of the local Archean granitoid,

and inferred from sedimentological features and contact relations, the rocks of the

Ilvesvaara Formation were deposited proximal to their source.

Three new members deposited on the top of the previously described Urkkavaara

Formation were defined and included in the formation. The members total up to 200

meters in thickness. The diamictite member was observed to wedge out towards the

north through grading into the upper siltstone-argillite member. In the south, the

diamictite member and in the north the upper siltstone argillite member were overlain

by the upward coarsening upper graded sandstone member, that gradually tumed

into the parallel-bedded conglomerate member characterized by inverse to normal

grading.

3

turbidity currents, and iceberg rafting in front of a grounded or floating glacier. It was

tentatively suggested , that if all of the lonestone-bearing units associated with

diamictites in Soviet Karelia, that occur in similar stratigraphie position, prove to be

glaciogenic deposits, they may indicate an Early Proterozoic, continent sca1e

glaciation.

In Paper 2, the immature metasediments enveloping the Kontiolahti dome in the north

were all interpreted as prejatulian, because the rocks were observed to grade upwards

into the metaregolith. The rocks were described, the Sariola Group several hundreds

of meters thick was established, through defining the formations included. The lower

contact of the Sariola group is a well-defined nonconformity. In addition, the

metaregolith was reported , preliminary described and named as the Hokkalampi

Formation.

The sporadically exposed basal arkoses and conglomerates overlain by the rocks of the

Urkkavaara Formation , were named as the Ilvesvaara Formation. The upper contact

is poorly exposed and the thickness of the unit is estimated not to exceed 30 metres.

The sediments were interpreted as alluvial deposits related to faulting . The mineral

composition sediments of the Ilvesvaara resembles that of the local Archean granitoid ,

and inferred from sedimentological features and contact relations, the rocks of the

Ilvesvaara Formation were deposited proximal to their source.

Three new members deposited on the top of the previously described Urkkavaara

Formation were defined and included in the formation . The members total up to 200

meters in thickness . The diamictite member was observed to wedge out towards the

north through grading into the upper siltstone-argillite member. In the south, the

diamictite member and in the north the upper siltstone argillite member were overlain

by the upward coarsening upper graded sandstone member, that gradually turned

into the parallel-bedded conglomerate member characterized by inverse to normal

grading.

4

Separated by erosional features at its base, the upward fining crossbedded

conglomerate member terminated the glaciogenic sequence. The upper graded

sandstone and parallel-bedded conglomerate with abundant subaqueus debris flow

deposits were interpreted as turbiditic sediments deposits, whereas the crossbedded unit

was deposited as glacial outwash during deglaciation. The clasts in the rocks of the

Urkkavaara Formation and the chemical composition of the matrix of the diamictite

member suggest a source area consisting of felsic plutonic rocks. The previous model

of deposition was complemented to be consistent with the presented new observations.

The sedimentary rocks of the Sariola Group grade upwards over 10 to 15 meters into

the quartz-sericite schist lacking internal features. The unit is present throughout the

study area and invariably underlies the quartzitic rocks of the Jatuli Group. In the main

part of the study area where the Sariola sediments are absent, the quartz-sericite schist

grade downward also into the Archean Basement. The thickness of the unit varies from

less than ten meters in the north to several tens of meters in the south. When thickest,

abundance of aluminum silicates features the upper part. In addition to stratigraphic

control, the gradual base due to chemical alteration, clear internal zoning reflected by

an upward depletion of alkalies and alkaline earths, upward increase of aluminium and

high values for the cIA in its upper part, evidenced in favour of soil origin for the

quartz-sericite schist.

The paleosol was interpreted to record an intense chemical weathering in warm and

humid climatic conditions corresponding to those prevailing today on low latitudes.

Thus the succession in the study area implies a drastic climate change. A tentative

correlation of the paleosol with other paleosols of similar stratigraphic position on the

Fennoscandian Shield was suggested. Excluding a quite similar paleosol in Kainuu, the

other paleosols are generally thin, and, show low to medium values for the cIA.

Paper 3 is a summary of lithostratigraphy and sedimentation of the Jatuli and Sariola

Groups in the study area. Relevant for the present paper are the provenance and

paleocurrent study, and, the defining of a new, sedimenary unit belonging to the

Sariola Group in the northern part of the study area.

4

Separated by erosional features at its base, the upward fining crossbedded

conglomerate member terminated the glaciogenic sequence. The upper graded

sandstone and parallel-bedded conglomerate with abundant subaqueus debris flow

deposits were interpreted as turbiditic sediments deposits, whereas the crossbedded unit

was deposited as glacial outwash during deglaciation. The elasts in the rocks of the

Urkkavaara Formation and the chemica1 composition of the matrix of the diamictite

member suggest a source area consisting of felsic plutonic rocks. The previous model

of deposition was complemented to be consistent with the presented new observations.

The sedimentary rocks of the Sariola Group grade upwards over 10 to 15 meters into

the quartz-sericite schist lacking internal features. The unit is present throughout the

study area and invariably underlies the quartzitic rocks of the Jatuli Group. In the main

part of the study area where the Sariola sediments are absent, the quartz-sericite schist

grade down ward also into the Archean Basement. The thickness of the unit varies from

less than ten meters in the north to several tens of meters in the south. When thickest,

abundance of aluminum silicates features the upper part. In addition to stratigraphie

control, the gradual base due to chemical alteration, elear internal zoning reflected by

an upward depletion of alkalies and alkaline earths, upward increase of aluminium and

high values for the CIA in its upper part, evidenced in favour of soil origin for the

quartz-sericite schist.

The paleosol was interpreted to record an intense chemica1 weathering in warm and

humid elimatic conditions corresponding to those prevailing today on low latitudes.

Thus the succession in the study area implies a drastic elimate change. A tentative

correlation of the paleosol with other paleosols of similar stratigraphie position on the

Fennoscandian Shield was suggested. Exeluding a quite similar paleosol in Kainuu, the

other paleosols are generally thin , and , show low to medium values for the CIA.

Paper 3 is a summary of lithostratigraphy and sedimentation of the Jatuli and Sariola

Groups in the study area. Relevant for the present paper are the provenance and

paleocurrent study, and, the defining of a new, sedimentary unit belonging to the

Sariola Group in the northern part of the study area.

5

The new unit, the Hattusaari Formation was correlated with the Sariola rocks in the

south. The correlation based on the observation that it grades upward through

alteration into the quartz-sericite schist of the paleosol. This 100m thick immature

formation consists of a lower matrix-supported conglomerate with abundant pebbles

from the adjacent Archean greenschists, a middle orthoconglomerate, and an upper

cross-bedded arkosic unit, that grades upward into the paleosol. Within the

conglomeratic unit, the pebbles of felsic plutonic rocks become more abundant upward

and, finally, in the middle part of the formation, dominant. For the Hattusaari

Formation, a proximal alluvial environment related to faulting was suggested. The

relation of the Hattusaari Formation to the Urkkavaara Formation in the south is

unresolved. However, the upper crossbedded paft of the formation resembles in

primary features that of the Urkkavaara Formation.

Paleocurrents indicated a general westward transport for the detritus allthough

considerable variation within the solitary units was observed. For the Sariola

sediments, a single cycle origin and a source area consisting mainly of felsic plutonic

rocks were suggested. A crucial result regarding the origin of the lower Jatuli

sediments, the aluminous. conglomeratic Vesivaara and quartzitic Koli Formations,

was that they were interpreted to have been derived from the underlying regolith and

were deposited as continental, fluviatile deposits (see also Kohonen 1987).

Paper 4 contains a defailed description of the Hokkalampi Paleosol called the

Hokkalampi Formation in the previous papers. Interpretation was based on chemical

and mineral composition of its protoliths, profiles and relation to the overlying

aluminous and quartzitic metasedimentary rocks. In the south and north the paleosol

forms a "marker bed" separating the Jatuli and Sariola sediments'

The paleosol consists of quartz-sericite schist with an increasing proportion of kyanite

and andalusite, sometimes chloritoid toward the top. The original soil had minimum

thickness of 80 meters, but is typically much thinner due to erosion prior to burial.

The erosion resulted in the deposition of voluminous aluminous sand and gravel, now

aluminous quartzite, metaconglomerate and orthoquartzite.

5

The new unit, the Hattusaari Fonnation was correlated with the Sariola rocks in the

south. The correlation based on the observation that it grades upward through

alteration into the quartz-sericite schist of the paleosol. This 100m thick immature

formation consists of a lower matrix-supported conglomerate with abundant pebbles

from the adjacent Archean greenschists, amiddie orthoconglomerate, and an upper

cross-bedded arkosic unit, that grades upward into the paleosol. Within the

conglomeratic unit, the pebbles of felsic plutonic rocks become more abundant upward

and, finally, in the middle part of the formation, dominant. For the Hattusaari

Formation, a proximal alluvial environment related to faulting was suggested . The

relation of the Hattusaari Formation to the Urkkavaara Formation in the south is

unresolved. However, the upper crossbedded part of the formation resembles in

primary features that of the Urkkavaara Formation.

Paleocurrents indicated a general westward transport for the detritus allthough

considerable variation within the solitary units was observed. For the Sariola

sediments, a single cycle origin and a source area consisting mainly of felsic plutonic

rocks were suggested. A crucial result regarding the origin of the lower Jatuli

sediments, the aluminous. conglomeratic Vesivaara and quartzitic Koli Formations,

was that they were interpreted to have been derived from the underlying regolith and

were deposited as continental , fluviatile deposits (see also Kohonen 1987).

Paper 4 contains a detailed description of the Hokkalampi Paleosol called the

Hokkalampi Formation in the previous papers. Interpretation was based on chemical

and mineral composition of its protoliths, profiles and relation to the overlying

aluminous and quartzitic metasedimentary rocks. In the south and north the paleosol

forms a "marker bed" separating the Jatuli and Sariola sediments.

The paleosol consists of quartz-sericite schist with an increasing proportion of kyanite

and andalusite, sometimes chloritoid toward the top. The original soil had minimum

thickness of 80 meters , but is typically much thinner due to erosion prior to burial .

The erosion resulted in the deposition of voluminous aluminous sand and gravel , now

aluminous quartzite, metaconglomerate and orthoquartzite.

6

The soil developed on both the Archean granitoids (middle part of the study area) and

Sariola glaciogenic rock (in the south and north). The major protolith for the paleosol,

the Archean granitoids mainly consist of tonalitic to granodioritic rocks, with minor

green schist. The sedimentary protolith, is dominantly arkosic in composition. The

CIA values for the protoliths vary between very low and low, indicating a low degree

of chemical weathering. Given the granodiotitic-tonalitic sources for the arkosite, the

prime difference in the chemical compositions is generally less iron, calcium and

aluminum, and, more silica in the sediments.

The Hokkalampi Paleosol clearly grades upward from its parent rocks through zones

ofincreasing alteration. Relative to its parents, the paleosol is consistently depleted in

ferrous iron, sodium, calcium and magnesium. In the upper, most throughly weathered

portions, ferric iron and potassium decrease, in some profiles considerably. Silica and

alumina constitute nearly all of the uppermost paleosol; alumina reaches 30%.

Estimates of the extent of weathering, based on values for the cIA index are low near

the bottom, moderate in the middle, and very high at the top. In the overlying

sediments, the values for the cIA vary insystematically between moderate and very

high. Chemical composition of the Hokkalampi Paleosol resembles that of the modern

kaolinitic soils. The premetamolphic minerals are interpreted to have been kaolinite

and residual quartz, given the present chemical and mineral composition of both the

paleosol and overlying sedimentary rocks.

The Hokkalampi paleosol is chemically reduced where thickest but sligthly oxidized

where it became eroded near topographic highs. The overlying aluminous sediments

lack ferrous iron and contain abundant hematite. Given that hematite formed withinthe contemporaneous soil, it record oxidation. The ratio uranium/thorium is muchhigher in the protoliths than in the overlying sediments that may indicate oxidation

associated with sedimentation and chemical weathering. oxidation of primarymagmatic uranium mineral erased from the Archean basement and the subsequent

mobilization of uranium may explain the absence of uranium paleoplacers in the studyarea, the other conditions being favourable. Thus,

development cannot be ruled out.

l rrwvtItgtIrlr(rtautE{,,us oxisol

6

The soil developed on both the Archean granitoids (middle part of the study area) and

Sariola glaciogenic rock (in the south and north). The major protolith for the paleosol,

the Archean granitoids mainly consist of tonalitic to granodioritic rocks, with minor

green schist. The sedimentary protolith, is dominantly arkosic in composition. The

CIA values for the protoliths vary between very low and low, indicating a low degree

of chemical weathering. Given the granodiotitic-tonalitic sources for the arkosite, the

prime difference in the chemical compositions is generally less iron, calcium and

aluminum, and, more silica in the sediments.

The Hokkalampi Paleosol clearly grades upward from its parent rocks through zones

of increasing alteration. Relative to its parents, the paleosol is consistently depleted in

ferrous iron, sodium, calcium and magnesium. In the upper, most throughly weathered

portions, feme iron and potassium decrease, in so me profiles considerably. Silica and

alumina constitute nearly all of the uppermost paleosol; alumina reaches 30% .

Estimates of the extent of weathering, based on values for the CIA index are low near

the bottom, moderate in the middle, and very high at the top. In the overlying

sediments, the values for the CIA vary insystematically between moderate and very

high . Chemical composition of the Hokkalampi Paleosol resembles that of the modern

kaolinitic soils . The premetamorphic minerals are interpreted to have been kaolinite

and residual quartz, given the present chemical and mineral composition of both the

paleosol and overlying sedimentary rocks.

The Hokkalampi paleosol is chemically reduced where thickest but sligthly oxidized

where it became eroded near topographie highs . The overlying aluminous sediments

lack ferrous iron and contain abundant hematite. Given that hematite formed within

the contemporaneous soil , it record oxidation. The ratio uranium/thorium is much

higher in the protoliths than in the overlying sediments that may indicate oxidation

associated with sedimentation and chemical weathering. Oxidation of primary

magmatic uranium mineral erased from the Archean basement and the subsequent

mobilization of uranium may explain the absence of uranium paleoplacers in the study

area, the other conditions being favourable. Thus, penecontemporaneous oxisol

development cannot be ruled out.

7

Early Proterozoic paleosol undedies quartz-arenite in the Karelides of the Svecofennian

Shield both in Finland and in Karelia of Russia. Paleosol in Kainuu, 300 km north of

the study area, is several tens of meters thick and similady consists of quartz-sericite

schist with aluminosilicates and chloritoid-rich units. It resembles the Hokkalampi

paleosol in that it also developed on sedimentary rock (of glaciogenic features) and is

overlain by aluminous quartzite. In Russia, the paleosols are thin but are also

composed of quartz-sericite schist. If all the paleosols and associated quartzite of the

Fennoscandian Shield are contemporaneous, the entire area of the Archean Craton

(400 000 km2) must have experienced a prolonged period of intense chemical

weathering.

CONCLUSIVE DISCUSSION

The main results of this study are the reporting of the presence of almost 300 meter

thick sequence of Sariola rocks, the recognition of glacial deposits and ancient soil

horizons underlying the quartzitic rocks in the study area.

The two Eady Proterozoic, extraordinary and strikingly different platformal

associations i.e. glacial deposits followed by theproducts ofdeep chemical weathering

(paleosol and associated aluminous sediments) preserved in the geologic record have

retained, despite of greenschist facies metamorphism and deformation, their primary

features astonishingly well to allow interpretations of conditions during their

origination.

Their geological signifrcance has been approached and discussed from the following

angles:

origin of voluminous quartz sands

as key units in regional correlation and even intercontinental correlation

oxidation-reduction of the paleoatmosphere

potential causes for drastic climatic changes.

7

EarIy Proterozoie paleosol underlies quartz-arenite in the Karelides of the Svecofennian

Shield both in Finland and in Karelia of Russia. Paleosol in Kainuu, 300 km north of

the study area, is several tens of meters thick and similarly consists of quartz-sericite

schist with aluminosilicates and chloritoid-rich units . It resembles the Hokkalampi

paleosol in that it also developed on sedimentary rock (of glaciogenic features) and is

overlain by aluminous quartzite. In Russia, the paleosols are thin but are also

composed of quartz-sericite schist. If all the paleosols and associated quartzite of the

Fennoscandian Shield are contemporaneous, the entire area of the Archean Craton

(400 000 km2) must have experienced a prolonged period of intense chemical

weathering.

CONCLUSIVE DISCUSSION

The main results of this study are the reporting of the presence of almost 300 meter

thick sequence of Sariola rocks, the recognition of giacial deposits and ancient soil

horizons underlying the quartzitic rocks in the study area.

The two EarIy Proterozoic, extraordinary and strikingly different platformal

associations i.e. glacial deposits followed by the products of deep chemical weathering

(paleosol and associated aluminous sediments) preserved in the geologie record have

retained, despite of greenschist facies metamorphism and deformation , their primary

features astonishingly weil to allow interpretations of conditions during their

origination .

Their geological significance has been approached and discussed from the following

angIes:

origin of voluminous quartz sands

as key units in regional correlation and even intercontinental correlation

oxidation-reduction of the paleoatmosphere

potential causes for drastic ciimatic changes.

8

The Sariola rocks comprise a purely sedimentary sequence, the immature rocks being

first cycle sediments. Instability is recorded by fast rate of sedimentation and rapid

burial; the Ilvesvaara and Hattusaari Formations were deposited during a faulting

stage.

The Urkkavaara Formation represents a result of glacial cycle, because the lower

glaciomarine part was formed during glaciation and the upper part deposited during

glacial retreat and deglaciation. For the Urkkavaara Formation, no evidence for acontemporaneous faulting exist. However, the basal part of the Ilvesvaara Formation

shows features that may be attributed to ice shattering. Consequently, it appears that

the entire sariola sequence may have been formed in a glacially influenced

environment associated with faulting.

The thick Hokkalampi paleosol, and the associated supermature sediments record

peneplanation, i.e., stability. The prolonged stability in surficial conditions was

featured by a warm and humid climate, or, other conditions causing high rate ofweathering. Extensive soils consisting mainly of kaolinite and residual quartz were

developed. composition, textural immaturity, and geological setting of the overlying

aluminous sediments show a close genetic relationship with the paleosol. A single-

cycle origin for these quartz-rich sediments is evident, the sediments being derived

from the contemporaneous soils.

The best preserved profiles of the paleosol record chemical reduction, seen as upward

depletion of ferrous iron and even ferric iron in some profiles. on the other hand,

eroded profiles and proximal aluminous and hematite-rich sediments show oxidation.This might mean that the oxyatmoinversion may have been underway

penecontemporaneously with the deep weathering and deposition of the associated

sediments. The absence of paleoplacer uranium deposits may be explained byconditions where primary uranium minerals were chemically decomposed withsubsequent mobilization of uranium.

8

The Sariola rocks comprise a purely sedimentary sequence, the immature rocks being

first cyele sediments. Instability is recorded by fast rate of sedimentation and rapid

burial; the Ilvesvaara and Hattusaari Formations were deposited during a faulting

stage.

The Urkkavaara Formation represents a result of glacial cyele, because the lower

glaciomarine part was formed during glaciation and the upper part deposited during

glacial retreat and deglaciation. For the Urkkavaara Formation, no evidence for a

contemporaneous faulting exist. However, the basal part of the Ilvesvaara Formation

shows features that may be attributed to ice shattering. Consequently, it appears that

the entire Sariola sequence may have been formed in a glacially influenced

environment associated with faulting .

The thick Hokkalampi paleosol, and the associated supermature sediments record

peneplanation, i.e., stability. The prolonged stability in surficial conditions was

featured by a warm and humid elimate, or, other conditions causing high rate of

weathering. Extensive soils consisting mainly of kaolinite and residual quartz were

developed. Composition, textural immaturity, and geological setting of the overlying

aluminous sediments show a elose genetic relationship with the paleosol. A single­

cyele origin for these quartz-rich sediments is evident, the sediments being derived

from the contemporaneous soils.

The best preserved profiles of the paleosol record chemical reduction, seen as upward

depletion of ferrous iron and even ferric iron in some profiles. On the other hand,

eroded profiles and proximal aluminous and hematite-rich sediments show oxidation.

This might mean that the oxyatmoinversion may have been underway

penecontemporaneously with the deep weathering and deposition of the associated

sediments. The absence of paleoplacer uranium deposits may be explained by

conditions where primary uranium minerals were chemically decomposed with

subsequent mobilization of uranium .

9

The generation of quartz sands through deep, chemical weathering was intemrpted by

rifting that resulted in the deposition of the arkosite of the Jero Formation, on the tip

of the quartzitic sequence and finally, in the mafic magmatism 2.2 Ga ago (Vuollo,

Piirainen & Huhma 1992, Kohonen & Marmo, 1992). Given the minimum age of 2.5

Ga for the Archean Basement Complex in eastem Finland, the time span requited for

the glaciation, deglaciation and the deep weathering was some 300 million years.

Kohonen and Marmo also interprete that the preservation of these continental deposits

can be explained by the downfaulting of the rifted Jero Basin. For the Sariolan rocks

and the paleosol the best preserved sections occur in the south. The glacial rocks may

have also been preserved as remnants of fault bounded basin. For the paleosol, the

preferential paleosol preservation was localized in areas of relative subsidence that

became the sites of braided river plains.

Early Proterozoic glaciogenic rocks as well as numerous remnants of paleosols

associated with quartzite of similar stratigraphic position are scattered across the

eastem Fennoscandian Shield. Given that they represent, respectively,

contemporaneous deposits, the Karelia Craton underwent a period of major glaciation

and subsequent deglaciation, and then the craton experienced a prolonged period of

intense chemical weathering.

In Kainuu and Karelia of Russia, glaciogenic rocks are underlain by or associated with

volcanic-sedimentary deposits. In Finnish I-apland, glaciogenic rocks have not been

reported, the lowermost unit being dominantly magmatic. The magmatic event related

to rifting has been dated to about2.44 Ga. In Kainuu, it appears (hajoki 1991) that

glaciogenic events were associated with this rifting. Assuming that the these basal units

including those of northern Karelia are contemporaneous, the rifting was craton wide,

but in northern Karelia it apparently did not advanced to a stage of magmatism.

Ojakangas (1988) has proposed a term "megaevent" for extraordinary geologic record,

such as major glaciations, that may be useful in intracontinental or even

intercontinental correlation. The two Early Proterozoic megaevents, glaciation

succeeded by deep weathering reported from the study area also record a drastic

9

The generation of quartz sands through deep, ehemieal weathering was interrupted by

rifting that resulted in the deposition of the arkosite of the Jero Formation, on the tip

of the quartzitie sequenee and finally, in the mafie magmatism 2.2 Ga ago (Vuollo,

Piirainen & Huhma 1992, Kohonen & Marmo, 1992). Given the minimum age of 2.5

Ga for the Arehean Basement Complex in eastern Finland, the time span requited for

the glaeiation , deglaciation and the deep weathering was so me 300 million years.

Kohonen and Marmo also interprete that the preservation of these eontinental deposits

ean be explained by the downfaulting of the rifted Jero Basin . For the Sariolan rocks

and the paleosol the best preserved sections oceur in the south . The glaeial rocks may

have also been preserved as remnants of fault bounded basin. For the paleosol, the

preferential paleosol preservation was localized in areas of relative subsidence that

became the sites of braided river plains.

Early Proterozoie glaeiogenie rocks as weIl as numerous remnants of paleosols

associated with quartzite of similar stratigraphie position are scattered aeross the

eastern Fennoseandian Shield. Given that they represent, respectively,

eontemporaneous deposits , the Karelia Craton underwent aperiod of major glaciation

and subsequent deglaeiation, and then the eraton experieneed a prolonged period of

intense ehemieal weathering.

In Kainuu and Kare1ia of Russia, glaeiogenie rocks are underlain by or associated with

volcanie-sedimentary deposits. In Finnish Lapland, glaeiogenie rocks have not been

reported , the lowermost unit being dominantly magmatie. The magmatie event related

to rifting has been dated to about 2.44 Ga. In Kainuu, it appears (Laajoki 1991) that

glaeiogenie events were associated with this rifting. Assuming that the these basal units

including those of northern Kare1ia are eontemporaneous, the rifting was eraton wide,

but in northern Karelia it apparently did not advaneed to a stage of magmatism.

Ojakangas (1988) has proposed a term "megaevent" for extraordinary geologie record,

sueh as major glaeiations, that may be useful in intraeontinental or even

intereontinental eorrelation . The two Early Proterozoie megaevents, glaciation

sueeeeded by deep weathering reported from the study area also record a drastie

10

climate change. For the Fennoscandian Shield, recent paleomagnetic studies suggest

that the shield drifted toward lower, and, given a climatic zoning toward warmer

latitudes during the Early Proterozoic. This is in accordance with the studied

geological record. We do not, however, know how long time span was involved in the

change and whether the climate change was exclusively due to drifting of continent or

were also global climatic changes involved.

For the Phanerozoic, there is evidence ofglobal climate changes triggered by extensive

volcanism injecting enormous amounts of SO, and CO, into the atmosphere. Irngterm changes in the Earth's climate, with megacycles of about 30 to 300 Ma have been

proposed perhaps to be caused by variations in atmospheric CO, due to cyclic global

tectonism (Rampino 1991, Fischer 1984, Imbrie and Shackleton 1990). For the early

Proterozoic, consequently, there may be causal connection between 2.44 magmatic

event, major glaciation and "green house effect"-type accelerated deep weathering.

Green house effect and acid rain, caused by effluents from burning offossil fuels, and

their consequences comprise one of the major challenges for today's natural science.

Deep chemical weathering and associated paleosols could be seen as a carbon dioxide

sink, and may thus appear a useful research target in gathering reference data to be

utilized in climate change studies.

Acknowledgements

I thank the heads of the Exploration Department of the Geological Survey of Finland,

especially Jouko Talvitie, Pentti Ervamaa and yrjö pekkala, for financial support.

Professor Richard w. ojakangas of the university of Minnesota, Duluth made a most

valuable contribution in stimulating the research during his many visits to Finland.

This work would lie uncompleted without the support of Professor Ilmari Haapala ofthe university of Helsinki. credit also is due to my colleagues, Jarmo Kohonen, olliAikas and olli Sarapiä for fruitful discussions and to the Kyykkä base camp, whichwas built on the paleosol on a glaciogenic rock. professor Kauko hajoki, universityof oulu and Associate Professor Raimo uusinoka, Tampere university of Technology,reviewed and improved the manuscript. Aune Romberg did the typing.

10

climate change. For the Fennoscandian Shield, recent paleomagnetic studies suggest

that the shield drifted toward lower, and, given a climatic zoning toward warmer

latitudes during the Early Proterozoic. This is in accordance with the studied

geological record. We do not, however, know how long time span was involved in the

change and whether the climate change was exclusively due to drifting of continent or

were also global climatic changes involved.

For the Phanerozoic, there is evidence of global climate changes triggered by extensive

volcanism injecting enormous amounts of S02 and CO2 into the atmosphere. Long

term changes in the Earth's climate, with megacycles of about 30 to 300 Ma have been

proposed perhaps to be caused by variations in atmospheric CO2 due to cyclic global

tectonism (Rampino 1991, Fischer 1984, Imbrie and Shackleton 1990). For the early

Proterozoic, consequently, there may be causa! connection between 2.44 magmatic

event, major glaciation and "green house effect"-type accelerated deep weathering.

Green house effect and acid rain, caused by effluents from buming of fossil fuels, and

their consequences comprise one of the major challenges for today's natural science.

Deep chemical weathering and associated paleosols could be seen as a carbon dioxide

sink, and may thus appear a useful research target in gathering reference data to be

utilized in climate change studies.

Acknowledgements

I thank the heads of the Exploration Department of the Geological Survey of Finland,

especially Jouko Talvitie, Pentti Ervamaa and Yrjö Pekkala, for financial support.

Professor Richard W. Ojakangas of the University of Minnesota, Duluth made a most

valuable contribution in stimulating the research during his many visits to Finland.

This work would lie uncompleted without the support of Professor Ilmari Haapala of

the University of Helsinki . Credit also is due to my colleagues, Jarmo Kohonen, Olli

Äikäs and Olli Sarapää for fruitful discussions and to the Kyykkä base camp, which

was built on the paleosol on a glaciogenic rock. Professor Kauko Laajoki, University

of Oulu and Associate Professor Raimo Uusinoka, Tampere University of Technology,

reviewed and improved the manuscript. Aune Romberg did the typing.

1l

References

Fisher, A.G. , (f 984). The two Phanerozoic supercyclas. /n.' Berggren, W., and Van Couvering, I.,(eds.) Caustophas in Earth's history, Princetown University Press, 129-150.

Gadl, G., (1964). Jatul und karelische Molasse im S-Koligebiet in Nordkarelien und ihre Beziehungenzum Gebirgsbau des pfüambrishen Orogens. Bull. Comm. Geol. Finlande 213. 45 p.

Imbrie, J. , and Shackleton, N.J. , (1990). The Odrt spectrum of oceanic deep water over five decadeband. Climatic Change, Vol. 16, 211-230.

Kohonen, J., (1987). Jatulimuodostumien paleosedimentologia Herajärven slue€lla Pohjois-Ka{alassa.Pohjois-Karjalan malmiprojekti, Oulun yliopisto. Raportti n:o 6.

Kohonen,J.,andMarmo,J.,(1992). ProterozoiclithostratigraphyandsedimentationofSariolaandJatuli type rocks in the Nunnanlahti-Koli-Kaltimo area, eastem Finland; implications for regionalbasin evolution models. Geol. Surv. Finland Bull. 364. 67 pp.

Laajoki, K., (1991). Stratigraphy ofthe northem end ofthe early Proterozoic (Karelian) Kainuun SchistBelt and associated gneiss complexes, Finland. Geol. Surv. Finland Bull. 358, 105 p.

Ojal<angas, R.Iy. , (1988). Glaciation: An Uncommon 'Mega-Event" as a Key to Intracontinental andIntercontinental Correlation of Early Proterozoic Basin Fill, North American and Baltic Cratons.Iz.' Kleinspehn, K.L. and Paola, C. (eds.) New Perspectives in Basin Analysis. Springer Verlag, NewYotk. 431-444.Piirainen, L, (1968). Die Petrologie und die Uranlagerstätten des Koli-Kaltimogebiets im finnischen

Nordkarelien. Bull. Comm. Geol. Finlande 237.99 p.Rarnpino, M.R., (1991). Volcanism, climatic change, and the geologic record. Sedimentation in

Volcanic Settings, SEPM Spec. Publication No. 45, 9-18.Vuollo, J., Piirainen, T. & Huhma, H., (1992). Two Early Proterozoic tholeiitic diabase dyke swarms

in the Koli-Kaltimo area, eastern Finland - their geological significance. Geol. Surv. Finland, Bull.363.32 p.

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References

Fisher, A.G. , (1984). The two Phanerowic supercycles. In: Berggren, W., and Van Couvering, J ., (eds.) Catastophes in Earth's history , Princetown University Press, 129-150.

Gadl, G. , (1964). Jatul und karelische Molasse im S-Koligebiet in Nordkarelien und ihre Beziehungen zum Gebirgsbau des präkambrishen Orogens. BuH. Comm. Geol. Finlande 213. 45 p.

Imbrie, J., and Shackleton, N.J. , (1990). The 0 .18 spectrum of oceanic deep water over five decade band. Clirnatic Change, Vol. 16, 217-230.

Kohonen, J. , (1987). Jatulimuodostumien paleosedimentologia Herajärven alueella Pohjois-Katjalassa. Pohjois-Katjalan rnalmiprojekti , Oulun yliopisto. Raportti n :o 6.

Kohonen, J. , and Manno , J. , (1992). Proterowic lithostratigraphyand sedimentation of Sariola and Jatuli type rocks in the Nunnanlahti-Koli-Kaltimo area, eastem Finland; implications for regional basin evolution models. Geol. Surv. Finland BuH. 364. 67 pp.

Laajoki, K., (1991). Stratigraphy of the northem end of the early Proterowic (Karelian) Kainuun Schist Belt and associated gneiss complexes, Finland. Geol. Surv . Finland BuH. 358, 105 p.

Ojakangas, R. W. , (1988). Glaciation: An Uncommon "Mega-Event" as a Key to Intracontinental and Intercontinental Correlation of Early Proterowic Basin FiH, North American and Baltic Cratons. In: Kleinspehn , K.L. and Paola, C. (eds.) New Perspectives in Basin Analysis. Springer Verlag, New York, 431-444. Piirainen, T. , (1968). Die Petrologie und die Uranlagerstätten des Koli-Kaltimogebiets im fmnischen

Nordkarelien. BuH. Comm. Geol. Finlande 237 . 99 p. Rampino , M.R. , (1991 ). Vo1canism, clirnatic change, and the geologie record. Sedimentation in

Vo1canic Settings, SE PM Spec. Publication No. 45, 9-18. Vuollo, J., Piirainen, T. & Huhma, H., (1992) . Two Early Proterowic tholeiitic diabase dyke swarrns

in the Koli-Kaltimoarea, eastem Finland - their geological significance. Geol. Surv. Finland, BuH. 363 . 32 p.