STRATIGRAPHIC STUDIES ON THE PRECAMBRIAN IN FINLAND

by Ahti Simonen

Simonen, A. 1986, Stratigraphie studies on the Preeambrian in Finland. Geological Survey 01 Finland, Bulletin 336, 21-37.3 figures, one table, one appendix.

The main historieal outlines of the stratigraphie study of the Preeambrian in Finland are presented. Detailed field work and the applieation of new methods of research have steadily inereased our stratigraphie knowledge, and many reinterpretations of earlier eonelusions have therefore been neeessary.

Key words: stratigraphy, basement , Svecokarelides, Preeambrian. research, history , glossary, Finland

Prof. Ahti Simonen, Otakllja 3 D 46, 02/50 Espoo /5, Finland

CONTENTS

Introduction ." , .. " .... "" .. "" ...... , ... ",., ... ",...... 22 Main historical outlines .",."" ...... , ... .. , ... ",." ...... ""... 22 Pre-Svecokarelidic base me nt complex 27 Svecokarelides 28 Karelidic belt 29 Svecofennidic belt ,., ...... , ... "' ...... , ,, ...... , 32 Post-Svecokarelian rocks ... .. , .. ,." .. ", ...... """, . . ", 34 ConcIuding Remarks ...... , 35 References ...... , ...... , ...... , ..... ,...... 35 Appendix: Explanation of the terms (by Ahti Simonen and Carola Eklundh) Geological Survey of Finland, Bulletin 336

22 Ahti Simonen INTRODUCTION

The study of the sueeession of events and Finland. Furthermore, the methods suitable the stratigraphie cIassifieation of formations for stratigraphie interpretation of metamorphie have persistently been the essential problems Preeambrian formations are briefly eonsid­ in the geologieal study of the Preeambrian in ered. Finland. Many stratigraphie sehemes, with As an appendix to this paper, a revised modifieations and reinterpretations, new version is given of the stratigraphie lexieon of suggestions, diseussions and polemies have the Finnish Preeambrian (Simonen 1955) been presented, marking the tortuous path published by the International Geologieal followed by the stratigraphie study of the Congress in the work »Lexique Stratigraphi­ Finnish Preeambrian. que International. » Carola Eklundh has The purpose of this paper is to deseribe the taken an aetive part in the preparation of this main historical outlines of the stratigraphie appendix. The explanations of the terms are cIassifieation of the Preeambrian bedroek in deseriptive, not normative.

MAIN HISTORICAL OUTLINES

The fundamental basis for the geologieal origin was explained aeeording to the neptu­ study of Finland was laid at the end of the nistie eoneeptions of Werner prevailing at that 19th eentury. The systematie geologieal time. mapping of the eountry was started and the The cIassical investigations of Sederholm first geologieal map sheet on the seale of (1891 and 1897) proved the aetualistie or uni­ 1 : 200 000 published in 1879. Important formitarian method to be the right approach events in the progress of geologieal research to the study of metamorphie Preeambrian in Finland were: formations. The Preeambrian erystalline sehists show as relies many struetures and - The organization of the study of geology textures similar to reeent sedimentary and on the University level. The first oeeupant volcanie rocks, and they were primarily de­ of the ehair of geology at Helsinki Universi­ posited in adefinite sueeession. Sederholm ty was appointed in 1876. stressed that geology is a seienee of time and - The establishment of the Geologieal Com­ the study of a sueeession of events. Therefore, mission (now the Geologieal Survey of the stratigraphie cIassifieation of the Pre­ Finland) in 1885 for the geologieal study eambrian runs like a red thread through his and mapping of the eountry. - The founding of the Geologieal Soeiety of whole work. Sederholm developed and modified his ideas in many papers and en­ Finland in 1886 as a forum for seientifie larged his stratigraphie cIassifieation to eom­ diseussions. prise the whole Baltie or Fennoseandian When the geologieal mapping was started, Shield. His last views were presented in 1932 the granites and gneisses, whieh eompose the in the explanatory text aeeompanying the main part of the Finnish bedroek, were re­ geologieal map of Fennoseandia. The main garded as »primitive formations» and their points of this stratigraphie schema eoneerning Geologieal Survey of Finland, Bulletin 336

Stratigraphie studies on the Preeambrian in Finland 23 the Finnish Preeambrian are presented in represented by the rapakivi granites, whieh Table 1. are not assoeiated with the orogenie move­ The essential points of Sederholm's strati­ ments. Sederholm also drew special attention graphie classifieation were based on the to the eonglomerates eontaining granite peb­ ehronologieal relation of the sehists and bles, for he believed that they marked deep gneisses to the granites of different age groups. erosion and uneonformities separating dif­ Sederholm classified the Preeambrian gran­ ferent eycles of sedimentation. Besides, in ites of Finland into four groups on the assump­ some eases, the separation of the age groups tion that every eycle of deposition of the was erroneously based solelyon a differenee sedimentary rocks was assoeiated with the in the grade of metamorphism, beeause it intrusion of a eertain granite group (see Table was believed that the older rocks show a 1). The granites of the first, se co nd and third higher grade of metamorphism than younger groups were eonneeted with orogenie eycles, on es do. whereas the granites of the fourth group were Sederholm' s stratigraphie schema presented

Table I. Sederholm's (1932) stratigraphie schema of the Preeambrian in Finland.

Jotnian Olivine diabases Sands tones of Pori

IVeyele (Late Preeambrian) Uneonformity

Hoglandian Rapakivi granites Ossipites and diabases of Jaala

Great uneonformity

Lapland granites 1II eycle Post-Jatulian epoeh of Granites of Oulu river, Kajaani , ete. (Karelidie) diastrophism Granites of Onas, Bodom, Ava, ete., in southern Finland

Kalevian and Jatulian Conglomerates, quartzites and sehists in eastern and northern Finland

Great uneonformity

Post-Bothnian epoeh of Granites of eentral area in Finland diastrophism 11 eyele (Younger Archean) Bothnian Bothnian meta basalts and sedimentary sehists in southwestern Finland Ladogian Ladogian sehists NW of Lake Ladoga Lapponian Lapponian iron-bearing formations and greenstones in Finnish Lapland

Uneonformity

I eyele Post-Svionian epoeh of Gneissose granites of the Sveeofennian ( Katarchean) diastrophism range and eastern Finland

Svionian Sehists and gneis ses of the leptite formation of southern Finland

Substratum unknown Geological Survey of Finland, Bulletin 336

24 Ahri Sirnonen

in Table I and his map of Fennoseandia (1932) The first eomprehensive study on the radio­ mainly revealed his ideas about the different aetive ages of Finnish rocks and minerals epoehs of diastrophism and represented the was published by Kouvo (1958). Most of the folded areas of different ages. His first, seeond age determinations have so far been done on and third eyeles eontained many different the zireons of magmatie rocks. Thus the mappable units (formations) of metamorphie igneous rocks and their eontaet relations have rocks, but their respeetive stratigraphie posi­ risen to a new and quite important role in the tions inside the eycle were very poorly known. age c1assifieation of the Finnish Preeambrian. Sederholm's studies were the first modern New geologieal studies have brought about approach to the task of building up a general many radieal ehanges in Sederholm's strati­ pieture of the evolution of the Finnish Pre­ graphie schema (see Table 1). The first reinter­ eambrian. Sinee Sederholm's time, more pretations eoneerned the independent strati­ detailed geologieal maps and the applieation graphie position of the eomplexes belonging of the methods of struetural and sedimentary to the seeond eyele in Sederhol m' s elassifiea­ geology as weil as radioaetive age determina­ tion. tio s have augmented our knowledge of the Diseussion of the uneonformity between the sueeession of geologieal events. Svionian and Bothnian eomplexes led to the Modern methods of tectonics were first interpretation that both of them belong to the applied by Wegmann (1928 and 1931) to the Sveeofennian eomplex, whieh was folded study of the metamorphie eomplexes in Finland. and metamorphosed in the Sveeofennidie This research had a marked influenee on the orogeny. On the other hand, the Ladogian separation of the struetural units as weil as and Lapponian eomplexes of Sederholm's on the development of the magmateetonieal seeond eyele were regarded, together with c1assifieation of orogenie plutonie rocks. the Jatulian and Kalevian formations, as Sederholm (1932) assumed that every orogenie Karelian deposits , whieh were folded and eyele was assoeiated with the intrusion of a metamorphosed in the Karelidie orogeny. granite group; but at present the granitoid Furthermore, the granites of Sederholm's first rocks, emplaeed during an orogeny, are and seeond eyeles were eonsidered to be elassified into three main groups, the so­ granites belonging to the same Sveeofennidie ealled synorogenie, late orogenie and post­ orogenie eycle. Coneerning Sederholm's orogenie grani tes. stratigraphie schema (Table 1), it ean be stated Many investigations using the aspeets of that the independent stratigraphie position of sedimentary geology have been made, espe­ his seeond eycle was eliminated, beeause its eially sinee World War II, and they have eomponents were ineluded in the first and inereased our knowledge of the primary third eyeles. eharaeter and depositional history of the In the mid-eentury, it was eommonly be­ Precambrian metasediments. Special atten­ lieved that the Preeambrian metamorphie tion was paid to struetures that suggested rocks of Finland are produets of two orogenie possibilities of determining the sequenee of eyeles, Sveeofennides and Karelides. The steep or vertieal layers of metamorphites. Sveeofennidie belt in southern and western Stratigraphie investigations earried out hand Finland was eonsidered to be older than the in hand with struetural studies have opened Karelidie sehist belts in the eastern and up new vistas toward stratigraphie eonelusions northern part of the eountry. eoncerning the folded Preeambrian eom­ The relationship between the Karelidie and plexes. Sveeofennidie sehist belts was diseussed by Geologieal Survey of Finland, Bulletin 336

Stratigraphie studies on the Preeambrian in Finland 25

Time Mo GEOLOGICAL EVOLUTION OF FINLAND PLEISTOCENE GLACIATION - - - ALKALINE ROCKS AND CARBONATITES - CALEDONIDES 500- PALEOZOIC SEDIMENTS - - - - 1000- - - - POST-JOTN IAN DIA BASES JOTNIAN SEDIMENTS - 1500- { RAPAKIVI GRANITES - POST-SVECOKARELIAN IGNEOUS ROCKS aUARTZ PORPHYRIES - DIABASES - SVECOKARELIDES FOLDING AND PLUTONISM - GEOSYNCLlNAL VOLCAN IS M GEOSYNCLlNAL SEDIMENTATION 2000 - fKALEVIAN AND SVECOFENNIAN) - JATULIAN VOLCANISM - AND SEDIMENTATION -

- PRE-SVECOKARELIAN IGNEOUS ROCKS {LAYERED MAFIC I NTR USIONS 2500- (YOUNGER THAN THE BASEMENT CO MPLEX) CARBONATITE COMPLEX - PRE - SVECOKARELIDIC { GRANULITES - BASEMENT GNEISSES - BASEMENT SCHISTS - (>

Fig. I. Geologieal timetable of the Preeambrian in Finland. After Simonen (1980).

various authors (cf., Mikkola 1953 , Metzger tions of the same orogenie eyele. The Jatulian 1959 , Simonen 1960). It was pointed out that sediments of the Karelian eomplex (basal the drawing of a sharp demareation line be­ eonglomerates, quartzites, dolomites and tween the Karelidie and Sveeofennidie belts phyllites) are eharaeteristie of an evolutionary is diffieult , beeause no evidenee of a marked epieontinental transgressive group deposited uneonformity has been found. Furthermore, upon the aneient Arehean basement. On the from the sedimentary geologieal point of view, other hand , the Sveeofennian deposits show the Karelian and Sveeofennian deposits seem eharaeteristies of a graywaeke-basalt assoeia­ to represent different sedimentary assoeia- tion of a geosynelinal sequenee. The radio- Geological Survey of Finland, Bulletin 336

26 Ahri Simonen

20- 25 30· -- ,- T

.. 10 l1li Ib le -~ 2 0-- - - 3 D 4 rn 5 1;:::;:: :1 6

~ l

" ·00 ISO ~'" I l 20· 25 30· - Fig. 2. Main structural units of the Precambrian in Finland. Pre-Svecokarelidic: la, schist and paragneiss; lb, granulite; Ic, orthogneiss. Svecokarelidic: 2, Karelidie schist belt; 3, Sveco­ fennidic schist belt; 4, orogenie plutonic rocks. Postsvecokarelian: 5, rapakivi granites; 6, Jotnian sediments. After Simonen (1980). Geologieal Survey of Finland, Bulletin 336

Stratigraphie studies on the Preeambrian in Finland 27 active ages of the orogenic plutonic rocks of Two orogenic revolutions have taken place the Karelidic and Svecofennidic belts vary in the Finnish Precambrian and they produced within the same limits (1 800-1 900 Ma) , the pre-Svecokarelidic and Svecokarelidic suggesting that the plutonism of both belts folded areas 2 800-2 600 Ma and 1 900-1 800 belongs to the same orogenic cycle. Ma ago, respectively. Both of the orogenic The orogeny, including both Karelides and evolutions were followed by periods of Svecofennides, was first named »Svecofenno­ cratonization connected with lively igneous Karelides,» but later a shorter term »Sveco­ activity, which took place on a stable platform karelides» has been commonly used (cf., in the time intervals 2 400 - 2 500 Ma and Simonen 1960 and 1971). The ancient base­ 1 550-1 700 Ma ago. The oldest nonmeta­ ment, upon which the Jatulian sediments of morphic sedimentary cover of the Finnish the Karelian complex have been deposited, is Precambrian is represented by the Jotnian named the »pre-Svecokarelidic basement.» sediments (1 300-1 400 Ma). Ideas about A summary of the Precambrian evolution the development of the stratigraphy of the of Finland and the areal distribution of the main structural units are presented in the main structural units are given in Figs. 1-2. following chapters.

PRE-SVECOKARELIDIC BASEMENT COMPLEX

Extensive basement gneiss areas in eastern the plutonic rocks penetrating the schists and northern Finland, which form the floor were interpreted as orogenic plutonic rocks of the deposition of the Karelian sediments, of the Karelides. However, later age data belong to the oldest part of the Finnish Pre­ indicate that the granitoids penetrating the cambrian. Sederholm (1897) proposed the schists are 2 600- 2 800 Ma old, and thus both term »Katarchean» for this basement complex the schists and granitoids belong to the ancient and he thought that it might belong to the pre-Svecokarelidic basement. original Earth's crust. Later, Sederholm (1932) The age relations of the rocks in the base­ stated that the Katarchean gneissose granites me nt area of eastern Finland were given penetrate some metamorphic schists; and in especial attention by Väyrynen (1933, 1939 his last summary on the geology of Fenno­ and 1954). In his opinion, the schists of the scandia, he correlated the gneissose granites Suomussalmi - Kuhmo and Kiihtelysvaara­ of eastern Finland to those of the Sveco­ Ilomantsi zones are older than the gneissose fennidic belt (see Table 1). granitoids of the basement. He concluded that The basement areas in eastern and northern the basement area of eastern Finland, the so­ Finland consist mainly of gneissose granitoids, called Jatulian continent, ac ted as a floor for so-ca lied basement gneisses. In addition, the Karelian sedimentation and formed a there are some narrow schist zones consisting resistance area during the Karelidic folding. of metasediments and metavolcanics. These Moreover, he proposed the term »Ipaui schists have been penetrated by gneissose formation» for the metasediments and meta­ granitoids. Certain schist zones of the base­ vo\canics penetrated by the pre-Sveco­ ment area (for example, the Suomussalmi­ karelidic gneissose granitoids. Väyrynen Kuhmo zone) were earIier correlated with the stressed that no basal beds had been found Kalevian rocks of the Karelian complex, and to show the sedimentation floor of his Ipaui Geological Survey of Finland , Bulletin 336

28 Ahli Simoll en formation. He interpreted the »basal schists ,» - luurikkaniemi formation: conglomerate, desc:ribed by various other authors, to be silicic metavolcanics, senclte quartzite mylonites that originated by overthrusting to with interbeds of mi ca schist, black schist the east. and iron formations . Simonen (1971) proposed the name Kuh­ moidic schists for Early Precambrian, pre­ Kellojärvi group: Svecokarelidic schists. These schists are Siivikko formation: peridotitic, pyroxemtlc penetrated by granitoids of the age group and basaltic komatiites and mafic tuffites; 2 600-2 800 Ma. The Kuhmoidic schists - Pahakangas formation: tholeitic metabasalts represent the oldest known metasediments with interbeds of iron formations . and metavolcanics in Finland. Subsilicic Luoma group: metavolcanics with small bodies of ultrabasics - silicic and intermediate metavolcanics, and quartz-banded iron ores are particularly gray wacke schists, phyllites and iron characteristic of the Kuhmoidic schists. formations. Various authors have correlated the schists of the basement area to the Archean green­ A summary of the geology and stratigraphy stone belts of the other continents. of the Kuhmo schist belt has been given by The stratigraphy of the Kuhmo greenstone Taipale and Tuokko (1981) and the komatiitic belt is, according to the Kuhmo Research and tholeitic metavolcanics of the Kellojärvi Proj ct working at the University of Oulu, group have been described by Hanski (1980). from the uppermost stratigraphic unit to The schists of the Tipasjärvi- Hietajärvi area the lowest, as folIows: (Taipale 1982) have been correlated to those Ontojärvi group: of the Ontojärvi group and they represent the - Petäjäniemi formation: mafic and ultramafic upper part of the stratigraphic sequence of metavolcanis, silicic metavolcanics and the Kuhmo schist belt. mica schists;

SVECOKARELIDES

The Svecokarelidic folded formations commonly believed earlier that they belonged occupy the main area of the Finnish Pre­ to two independent orogenic cycles. Further­ cambrian, including both Karelidic and Sveco­ more, it was believed that the highly meta­ fennidic belts. The Karelides in eastern and morphic and migmatitic Svecofennidic rocks northern Finland consist of the latulian, were considerably older than those of the Kalevian, Ladogian and Lapponian com­ Karelides. However, the increase in our plexes, whereas the Svecofennides in southern knowledge of Precambrian sedimentation and and western Finland consist of Svionian and tectonics and radioactive age determinations Bothnian complexes. Many fundamental have shown that the Karelidic and Sveco­ differences occur in their lithology, tectonics fennidic zones belong to the same orogenic and metamorphism between the Karelides belt - the Svecokarelides (cf. , Simonen 1960 and the Svecofennides, and therefore it was a nd 1971) . Geologieal Survey of Finland, Bulletin 336

Stratigraphie studies on the Preeambrian in Finland 29 Karelidic heIt

The gneisses and schists of eastern Finland relations of the aforementioned formations were divided by Wiik (1874) into three groups, be ca me questionable. It soon became appar­ which were, from the oldest to the youngest: ent, however, that the Ladogian, Kalevian Laurentian gneisses, Huronian schists and and J atulian formations belong close together, Takonian quartzites and tale schists. Wiik and Eskola (1921) therefore proposed for them took the view that the Takonian quartzites a collective name »Karelian. » Karelian thus were overthrust by the mica schists. refers to all the sediments the deposition of Tigerstedt (1892) interpreted the schists of which was connected with the Karelidie northern Karelia as sediments deposited under orogenie cycle. Applying the tectonic model continuous subsidence of the basement. The of the Alpine chain, Wegmann (1928) ex­ coastal deposits (conglomerates and quartz­ plained that the rocks of the Jatulian type ites) underlie water-Iaid sediments (limestones represent deposits upon foreland and shelf­ and phyllites). Tigerstedt thought that the areas, the Kalevian rocks being flysch-type well-preserved schists of northern Karelia sediments and the Ladogian rocks deposits of are younger than the gneisses of southern the central part of the geosyncline. Finland. Sederholm took an active part in the discus­ Sederholm (1897) proposed the term »latu­ sions concerning the age relations of the lian» for the Karelian quartzites and the term Karelian formations. In his last stratigraphie »Ladogian» for the micaceous schists that schema (1932) , the Ladogian rocks were Sederholm believed to underlie the Jatulian included in his second cycle, whereas the rocks. The Ladogian schists were considered Kalevian and Jatulian rocks represented the to be sediments deposited upon the Katar­ sediments of the third cycle. Sederholm held chean gneissose granites. The age difference the view that the Ladogian deposits were between Ladogian and Jatulian was based much older than the other Karelian sediments, on the difference in their grade of meta­ but that they had been reworked by the morphism and the observation that the Jatu­ Karelidie orogenie movements. Sederholm lian was not penetrated by granites, whereas (1932) included the Lapponian rocks of the Ladogian was richly intersected by granitic Central Lapland as weil in his second cycle. vems. A detailed stratigraphy of the Jatulian group Frosterus (1902) found in Finnish Karelia was published by Metzger (1924) from the and Ramsay (1902) in Russian Karelia schists Suojärvi area, where the Jatulian sediments that were not penetrated by granites and form a basin upon the pre-Svecokarelidic that seemed to fall stratigraphically between granite gneiss. Epicontinental Jatulian (Metz­ the Ladogian and Jatulian formations. They ger' s Eo-Jatulian) conglomerates and quartz­ proposed for these deposits the name »Kale­ ites underlie the marine Jatulian (Metzger' s vtan .» Meso- and Neo-Jatulian) dolomites and pelitic Originally the Kalevian as weil as the Jatu­ schists. lian were considered to be formations that The stratigraphy of the Karelian formations were not penetrated by granites, and therefore has been discussed and summarized especially they were interpreted as being much younger by Väyrynen (1933 , 1939 and 1954), who thah the Ladogian schists. Later, it was divided the Jatulian group into three different observed that granites also penetrate Kalevian stratigraphie units: Sariolian, Kainuan and and Jatulian formations. Therefore, the age so-called marine Jatulian. The term »Sario- Geological Survey of Finland, Bulletin 336

30 Ahti Simonen lian» had been proposed by Eskola (1919) for Karelian formations. These Lapponian forma­ the tillite-like, polymict conglomerates and in­ tions, ineluded by Sederholm (1932) in his tercalated arkoses in Eastern Karelia, wh ich second cyc\e, may belong to the Karelidie were deposited upon the pre-Svecokarelidic eycle and the conglomerates and coarse­ basement and which underlie the Jatulian grained quartzites (Kumpu formation), which quartzites. The widely distributed »Kainuan» overlay the Lapponian sueeession, were formation of Väyrynen begins with sericite­ eonsidered as molasse sediments of the Kare­ bearing quartz conglomerates associated with lides (cf., Mikkola 1941 and Eskola 1941). sericite schists. With a decrease in the sericite The quartzites of the Kemi area, which content, the quartzites pass into pure quartz­ underlie greenstones and slates with inter­ ites of the upper division of the Kainuan calated dolomites (Härme 1949), ean be formation. The epicontinental Kainuan eorrelated with the Kainuan quartzites of quartzites underlie dolomites and slates, Väyrynen's standard seetion, the greenstones which have been called marine latulian are probably equivalent to the metadiabases sediments (Metzger's Meso- and Neo-latu­ penetrating the latulian group and the thick lian). Väyrynen (1933) presented from north­ aceumulation of graded-bedded slates eorre­ ern Karelia valid field evidence that shows sponds to the Kalevian type of sedimenta­ (contrary to Sederholm) that the latulian tion. rocks are older than the Kalevian. Conglo­ Sinee the early 1960s, a more detailed merates containing mainly pebbles of the geologieal remapping of the Karelidie sehist Kainuan quartzite occur as basal beds of the areas was started and many papers (e.g., Kalevian phyllites and mica schists. Further­ Piirainen 1968 , Nykänen 1971 , Silvennoinen more, metadiabases penetrating the latulian 1972, Laajoki 1973 and 1975, Mäkelä 1976 rocks oecur as pebbles in eertain eonglo­ and Pekkarinen 1979) have completed and merates separating the latulian and Kalevian partly eorrected Väyrynen's standard strati­ groups. graphie section. New investigations have The standard stratigraphic section of the pointed out that the latulian sedimentation Karelian formations In eastern Finland, was associated with contemporaneous mafic according to Väyrynen (1933), is as folIows: volcanism, wh ich took place in many pulses. Kalevian group: Volcanie interbeds of the latulian strata have phyllites and miea sehists been used as suitable key beds for the strati­ eonglomerates graphie subdivision and eorrelation. In addi­ latulian group: tion, the Sariolian eonglomerates and arkoses earbonaceous slates have been eonsidered as an independent dolomites group underlying the latulian. Reeently Mar­ quartzites mo & Ojakangas (1984) found lower Protero­ basal conglomerates and arkoses zoic glaeiogenie deposits from the upper part Great unconformity of the Sariolian group and proposed the name »Urkkavaara formation» for them. pre-Sveeokarelidic basement. Sinee 1973, latulian geology has been one The geological studies made in Finnish Lap­ of the most important geologie al programs land by Erkki Mikkola (1941) indieated that in the seientific collaboration between Finland there are sehist formations that consist mainly of and the Soviet Union. The proceedings of the quartzites, miea sehists and basic volcanics joint symposium »latulian geology in the and show eonspieuous similarities to the eastern part of the Baltic Shield» contain rich, Geologieal Survey of Finland, Bulletin 336

Stratigraphie studies on the Precambrian in Finland 31 KARELIAN FORMATIONS

phyllites and mica schists

Kalevian graded- bedded quartzite = mica schist layers => conglomerate 0 2000 Ma-unconformity- V Jatulian greenstone dolomite upper block sChist, phyllite V dolomite 000 quartzite V v v v greenstone middle quartzite 00 00

lower

Sariolian upper

greenstone middle

lower arkosite conglomerate

Fig. 3. Simplified, sehematie ftS.2t;:J:.::Q~~J;~------2500 Mo - major unconformity­ stratigraphie seetion of Kare­ Presvecokarelian lian formations. I, pre-Sveeo­ basement karelidie basement; 2, basal eonglomerate; 3, conglomer­ ate; 4, arkosite; 5, greenstone; Lithologie symbols 6, orthoquartzite; 7, sericite quartzite; 8, dolomite; 9, blaek [Sd 1 ~2 bOoOd 3 ...... 4 schist; 10, phyllite and mi ca 0 schis!. After Meriläinen (1980). 0 6 t-=-d 7 ES:5j 8 1111111 19 1 110 to some extent preliminary material on the lian formations (Fig. 3). The Survey geologists stratigraphy of the Karelides. Meriläinen working in Lapland (Silvennoinen et al. 1980) (1980) presented the newest, somewhat considered the Kumpu formation as Jatulian simplified stratigraphical section of the Kare- and the Lapponian schists (greenstones, Geological Survey of Finland, Bulletin 336

32 Ahli Simollen sericite quarzites and mica schists) as Archean samo, Salla and Central Lapland, previously formations. Subsequently, Lauerma (1982) considered as Archean, may be Proterozoic has pointed out, however, that the Archean in age. The concepts on the stratigraphie age of the Lapponian schists is disputable position of the schists in Lapland seem to and certain parts of the schist areas in Kuu- be disputable also at present.

Svecofennidic beIt

Sederholm (1893) distinguished in southern of the pre-Bothnian diorite. These were and western Finland two Precambrian rock regarded as basal beds of the Bothnian strata. units differing in age. He proposed the term In his last review of the Precambrian »Bothnian system» for the younger unit and geology of Fennoscandia, Sederholm (1932) late!" designated the older pre-Bothnian unit stressed that, in relation to the orogenie (Sederholm 1920) as the »Svionian complex.» tectonic movements, the Bothnian and Svio­ The Svionian schists and gneisses were nian rocks belong to different orogenie cycles penetrated by pre-Bothnian gneissose gran­ (see Table 1). The Bothnian rocks were ites, and the Bothnian metasediments and included in the second cycle of sedimenta­ metavo1canics were intruded by post-Bothnian tion, which was deposited on the deeply granites. Sederholm supposed that the Svio­ denuded crystalline basement, composed nian and Bothnian formations were separated of highly metamorphie supracrustal rocks by a great unconformity, the deeply eroded of the first Svionian cyc1e as weil as gneissose pre-Bothnian basement consisting of schists, granites of the first group. The Bothnian strata gneisses and gneissose granites that formed were folded and metamorphosed in the later a floor for the deposition of the Bothnian orogenie movements connected with the rocks. intrusion of the granites of the second group. The stratigraphie position of the Bothnian Sederholm 's idea concerning a great un­ has been discussed by Sederholm (1897) in conformity between the Svionian and Both­ more detail in his classical paper dealing with nian complexes has, however, been criticized the Tampere schist zone, where the Bothnian by many geologists. Mäkinen (1915) pointed metavo1canics and metasediments show many out that the granites considered to be pre­ relic:s of primary structures. Sederholm Bothnian by Sederholm penetrate the Both­ concluded that the Bothnian rocks of the Tam­ nian rocks of the Tampere area and that the pere area are separated by a great unconform­ Bothnian conglomerates do not signify a deep ity, situated along the southern margin of denudation, as supposed by Sederholm, but the schist belt, the highly metamorphie show an intraformational mode of occurrence. gneisses and gneissose granites of wh ich Many observations (cf., Eskola 1936, Wahl form the crystalline basement for the deposi­ 1936 and Simonen 1948) indicated that the tion of the Bothnian complex. As his main granitoids of Sederholm' s first group penetrate evidence for the »great unconformity,» the metamorphosed Bothnian rocks. There­ Sederholm (1897 and 1931 ) drew special fore , in regard to the intrusive contacts, atte tion to certain Bothnian conglomerates there seems to be no marked age difference with diorite boulders and to the weathering between the Bothnian and Svionian com­ breccias containing angular fragments of plexes. diorite in an arkosic matrix along the contact Considering the Bothnian conglomerates Geological Survey of Finland, Bulletin 336

Stratigraphie studies on the Precambrian in Finland 33 eontammg dioritie pebbles, Eskola (1941) The standard stratigraphie seetion of the observed that they do not show the eharaeter Tampere area is eharaeterized by thiek of real basal eonglomerates, separating two aeeumulations of immature argillaeeous and different orogenie eycles, beeause they do not arenaeeous deposits underlying mafie eontain migmatitie pebbles, indieators of voleanis. The sequenee shows eharaeteristies a deep erosion. The eonglomerates and of the graywaeke-basalt assoeiation of the weathering breeeias show only that, during geosynclinal sediments. the deposition of the Bothnian strata, the The Bothnian sehists pass in many loealities denudation had suffieed to reaeh the plutonie without uneonformity into highly meta­ rocks , whieh were intruded at an early morphie and migmatitie gneisses of the orogenie state, and that the »sub-Bothnian un­ Svionian type. Simonen (1953) eonsidered eonformity» is the result of loeal erosion that the Svionian gneisses only represent more during the orogenie evolution. metamorphie and reerystallized sehists of the All the foregoing observations on the »sub­ Bothnian type. The grade of metamorphism Bothnian uneonformity» supported the view and reerystallization varies within wide that it does not separate the formations of limits and the low-metamorphie Bothnian different orogenie eycles. Furthermore, the rocks have as counterparts the highly meta­ orogenie elassifieation of granites, developed morphie Svionian gneisses. Graywaeke­ in the 1930s , indieated that Sederholm's pre­ slates with graded bedding pass gradually Bothnian and post-Bothnian granites represent through miea sehists into miea gneisses, synorogenie and late orogenie intrusions of meta-arkoses into granoblastie leptites, and the same orogenie eycle. On the basis of metabasalts into amphibolites and hornblende these eonsiderations, both the Svionian and gneisses. Simonen (1953) proposed the term the Bothnian formations were included as »Bothnian group, » whieh ean be applied to the Sveeofennian formations in the Sveeofennidie Sveeofennian strata eharaeterized by a rieh orogenie eycle. oeeurrenee of mafie volcanies, and the term On the basis of the geologieal remapping, Svionian group to the axial portion of the Simonen (1953) di seussed the sedimentation geosynclinal sediments underlying the basic and stratigraphy of the Sveeofennian rocks volcanies. However, drawing a well-defined in southwestern Finland. A key area for the line between the groups mentioned is not exposition was the Tampere field , where the possible. relies of primary struetures are so well­ Simonen (1953) pointed out that a strati­ preserved as to enable one to determine the graphie sueeession related to that of the sequenee of the layered rocks, although the Tampere area is eommon in many parts of the beds have been folded into a steep or vertieal Sveeofennidie belt. This was proved by many position. The sequenee of the supracrustal investigations earried out in different parts rocks in the Tampere area, from the upper­ of the Sveeofennides (cf., Härme 1954 and most stratigraphie unit to the lowest is, 1980, Neuvonen 1954 , Edelman 1960, SaUi aeeording to Simonen (1953), as folIows: 1964 , Laitala 1973 , Ehlers 1978). It is eharae­ Thiekness in meters teristie of the Sveeofennian stratigraphy that Mafie voleanies > 1000 Conglomerates and as oeiated beds thiek aeeumulations of immature sediments of gray.waeke slates and arkoses 700 - 800 underlie the mafie volcanies, whieh in some Mafie and intermediate volcanies 800 - I 500 areas, espeeiall y in southern Finland, are Quartz-feldspar roeks (arkoses, graywaekes and pyroclastics) I 500 - 2 200 overlain by thin deposits of argillaeeous Graywacke slates > 3000 sediments. The Sveeofennian strata have

3 Geological Survey of Finland, Bulletin 336

34 Ahti Simonen

been tentatively divided (Sirnonen 1960 and with intercalated sediments (arkoses, 1980) into Lower, Middle and Upper Sveco­ graywackes and conglomerates) fennian subgroups, as folIows: Lower Svecofennian: immature sediments (arkoses and gray­ Up er Svecofennian: wackes) with thin interbeds of calcareous argillaceous sediments material and mature sandstones in the Middle Svecofennian: arkoses of some areas. mafic volcanics (Javas and pyroclastics)

POST-SVECOKARELIAN ROCKS

Sederholm (1897) proposed the term 10tnian posed the term »Hoglandian» to replace the for the Precambrian magmatic and sedimen­ terms Lower 10tnian and sub-lotnian. In his tary rocks that had not taken part in the last review of Fennoscandian geology, Seder­ orogenie movements. The oldest 10tnian sedi­ holm (1932) included both the Hoglandian and mentary rock was the quartzite conglomerate 10tnian formations, which were separated of Hogland (Suursaari), which underlies by an unconformity, in his fourth cycle of quartz porphyries associated with rapakivi sedimentation (see Table I). magmatism. The red arkose sandstone of Sederholm' s conclusions on lhe age rela­ Satakunta and the sandstone of Isojoki (Lau­ tions of the nonmetamorphie Precambrian havuori) represented the youngest 10tnian rocks in Finland have been proved correct sediments, which were younger than the by many later investigations. The age succes­ rapakivi magmatism. Later, Sederholm (1913) sion rapakivi granite - Jotnian sandstone - regarded the lsojoki sandstone as Cambrian post-Jotnian olivine diabase was pointed out deposit. by A. Laitakari (1925) and Kahma (1951). The 10tnian magmatic rocks are mainly A new occurrence of nonmetamorphie rapakivi granites, wh ich are associated with sandstones , siltstones and shales was found gab ro-anorthosites. diabases. mafic effusives in northem Pohjanmaa. This so-called Muhos and quartz prophyries. These magmatic rocks formation was interpreted in Brenner' s (1941) are younger than the quartzite conglomerate preliminary report as a Mesozoic sediment; from Hogland, but older than the arkose but it was subseqllently correlated to the sandstone of Satakunta. The youngest 10tnian 10tnian formations (cf., Simonen & Kouvo magmatic rock is olivine diabase, which 1955). Microfossils found in the sediments of penetrates the red arkose sandstone . Hailuoto (Tynni & Donner 1980) indicate a Later, the Jotnian formations were divided Late Precambrian (Vendian) age for the upper­ into U pper and Lower Jotnian formations. most part of the Muhos formation. Sub-lotnian The red arkose sands tones represented the or Hoglandian diabases, which are older than Upper Jotnian , whereas the rapakivi granites the rapakivi granites, have been reported from containing associated magmatic rocks and the northern side of the rapakivi areas in sediments were Lower 10tnian formations. southeastern Finland; and they continue into The term »sub-lotnian» for the Lower Jotnian the Häme region , where they ha ve been de­ rocks was commonly lIsed , especially by scribed by I. Lai takari (1969). Swedish geologists. Sederholm (1927) pro- The roof pendants in the Wiborg rapakivi Geological Survey of Finland, Bulletin 336

Stratigraphie studies on the Precambrian in Finland 35 massif consist partly of Svecokarelidic rocks which in the geologieal map sheet of Ylämaa and partly of sub-Jotnian mafie and silieie (Simonen 1979) overlies the Sveeokarelidie voleanie rocks, whieh have been thermally granitoid and underlies the sub-Jotnian mafie metamorphosed by the rapakivi granite (Vor­ volcanies and quartz porphyries. The strati­ ma 1975). Some of the roof pendants also graphie position is therefore similar to the contain a thermally metamorphosed quartzite, quartzite conglomerate of Hogland.

CONCLUDING REMARKS

The foregoing historieal outlines show that stratigraphie study of Preeambrian forma­ interpreting of the stratigraphy of the folded, tions. Preeambrian formations in Finland has been The Preeambrian in Finland is a typical diffieult and that many mistakes have been and eentral part of the Baltie, or Fennosean­ made. Many of the earlier eonclusions and dian, Shield , whieh is the broadest Shield assumptions about the stratigraphy and age area of the European eontinent, and its many relations of the Finnish Preeambrian rocks geologieal formations have counterparts in have been reinterpreted and modified by later neighboring countries. The studies of Finnish investigations. The eonstruetion of the Pre­ geologists have played an important role in cambrian stratigraphy was, to use Seder­ the elueidation of the geology and stratigraphy holm's words, like the weaving of Penelope, of the Baltie Shield , but many stratigraphie who unravelled nightly the work she had problems are still debatable. New investiga­ done during the day. However, in spite of tions and close eollaboration among geologists the many mistakes and diffieulties, our of neighboring countries are neeessary for knowledge of the stratigraphy of the Finnish a generally approved stratigraphie classifica­ Preeambrian has progressively increased with tion of the Baltie Shield and its eorrelation the advanees made in the geologieal sciences to the Precambrian stratigraphy of different and the development of new methods in the continents.

REFERENCES

Brenner. Th .• 1941. Ein ungewöhnliches Ka lk -Schlamm­ - 1921. Kidetieteen . mine ralogia n ja geologian a lkeet. stein sedime nt von Muhos in Mitte lfinnla nd . Geol. Werner Söderström Osakeyhtiö. Porvoo. 296 p. Rund scha u 32, 535 - 549. - 1936. Geologisk exkursion till sydvästra Finland . Edelman, N., 1960. The Gu llkrona region, SW Fi nl and. Nordiska naturforskarmötet i Helsingfors 1936. BuH. Comm. geol. Finlande 18 7. 87 p. 220 - 230 . Ehlers. c., 1978. Gravity tectonics a nd folding a ro und - 1941. Erkki Mikkola und der heutige Sta nd der prä• a basic volcanic centre in Kumlinge area. SW Finland . ka mbrische n Geologi in Finnland. Geol. Rundscha u Geol. Surv. Fi nl a nd . BuH . 295. 43 p. 32 , 452 - 483 . Eskola, P., 1919. Huvuddragen av Onega- Ka re li e ns Frosterus, B., 1902. Bergbyggnaden i sydöstra Finland. geologi. Meddel. geol. [ören . Helsingfors . 191 7- Bull . Comm. geol. Finlande 13 . 166 p. 1918. 13- 18. Hackman, V. , 1927. Studien über den Gesteinsaufbau der Geological Survey of Finland, Bulletin 336

36 Ahli Simonen

Kittilä-Lappmark. BuH. Comm. geol. Finlande 79. -, 1959. Svecofenniden und Kareliden. Acta Akad. 107 p. Aboensis, Mathem. Phys. 21. 27 p. Hanski, E., 1980. Komatiitic and tholeiitic metavolcanics Mikkola, E., 1941. Kivilajikartan selitys B7 - C7 - 07, of the Siivikkovaara area in the Archean Kuhmo Muonio- Sodankylä - Tuntsajoki. Suomen Geologi­ greenstone belt, eastern Finland. Geol. Soc. Finland, nen yleiskartta, 1 : 400 000. [Explanation to the map BuH. 52, 67 - 100. of rocks] 286 p. Härme, M., 1949. On the stratigraphical and structural Mikkola, T., 1953. Peruskalliogeologian näköaloja. Geo­ geology of the Kemi area, northern Finland. BuH. logi 4, 29. Comm. geol. Finlande 147. 60 p. Neuvonen, K., 1954. Stratigraphy of the schists of the 1954. Structure and stratigraphy of the Mustio area, Tammela- Kalvola area, southwestern Finland. Bull. southern Finland. BuH. Comm. geol. Finlande 166 , Comm. geol. Finlande 166, 85 - 94 . 29 - 48. Nykänen, 0., 1971. On the Karelides in the Tohmajärvi 1980. Kivil ajikartan selitys C 1-0 I, Helsinki. Suomen area, eastern Finland. Bull. Geol. Soc. Finland 43, geologinen yleiskartta, 1 : 400 000. [Explanation to 93 - 108. the map of rocks] 95 p. Pekkarinen, L., 1979. The Karelian formations and their Kahma, A., 1951. On the contact phenomena of the depositional base me nt in the Kiihtelysvaara - Värtsilä Satakunta diabase. BuH. Comm geol. Finlande 152. area, East Finland. Geol. Surv. Finland, BuB. 301. 84 p. 141 p. Kouvo, 0., 1958. Radioactive age of some Finnish Piirainen, T., 1968. Die Petrologie und die UranIager­ Precambrian minerals. BuH. Comm. geol. Finlande stätten des Koli- Kaltimogebiets im finnischen Nord­ 182. 70 p. karelien. BuH. Comm. geol. Finlande 237. 99 p. Laajoki, K. , 1973. On the geology of the South Puolanka Ramsay, W., 1902. Om de prekambriska formationerna area, Finland. Geol. Surv. Finland, BuH. 263. 54 p. och bergveckningarna iden sydöstra delen af Fen­ 1975. On the stratigraphic position of kaolin in noskandia. Geol. Fören. Stockholm Förh. 24, 28 - 36. Väyrylänkylä, South Puolanka area, Finland. Bull. Salli, 1. , 1964. The structure and stratigraphy of the Yli­ Geol. Soc. Finland 47 , 83 - 91. vieska-Himanka schist area, Finland. Bull. Comm. Laitakari, A., 1925. Über das 10tnische Gebiet von Sata­ geol. Finlande 211. 67 p. kunta. BuH. Comm. geol. Finlande 73. 43 p. Sederholm, J. , 1891. Studien über archäische Eruptiv­ Laitakari, 1., 1969. On the set of olivine diabase dikes in gesteine aus dem südwestlichen Finland. Mineral. Häme, Finland. BuH . Comm. geol. Finlande 241. Petrol. Mit!. 12 , 97-142. 65 p. 1893. Om berggrunden i södra Finland. Fennia 8. Laitala, M., 1973. On the Precambrian bedrock and its 137 p. structure in the PeHinge region , South Finland. Geol. 1897. Über eine archäische Sedimentformation im Surv. Finland, BuB. 264. 76 p. südwestlichen Finnland und ihre Bedeutung für die Lauerma, R. , 1982. On the ages of some granitoid and Erklärung der Entstehungsweise des Grundgebirges. schist complexes in northern Finland. BuH. Geol. Soc. Bull. Comm. geol. Finlande 6. 254 p. Finland 54, 85- 100. 1913. Kivilajikartan selitys B2, Tampere. Suomen Mäkelä, K., 1976. On the stratigraphy and petrography geologinen yleiskartta, 1 : 400000. 122 p. of the Tuomivaara iron ore formation in Sotkamo, 1920. Nägra huvuddrag i meBersta Fennoskandias northern Finland. BuB. Geol. Soc. Finland 48 , 71-86. urberg. Geol. Fören. Stockholm Förh . 42, 19 - 25. Mäkinen, E., 1915. Ein archäisches Konglomeratvor­ 1927.001 de jotniska och s.k. subjotniska bergarterna. kommen bei Lavia in Finland. Geol. Fören. Stock­ Geol. Fören. Stockholm Förh. 49. 397-426. holm Förh. 37, 385-421. 1931. On the sub-Bothnian unconformity and on Marmo, J. & Ojakangas, R., 1984. Lower Proterozoic Archaean rocks formed by secular weathering. Bull. glaciogenic deposits, eastern Finland. Geol. Soc .. Comm. geol. Finlande 95. 81 p. Am. BuB. 95, 1055 - 1062 . 1932. On the geology of Fennoscandia. Bull. Comm. Meriläinen, K., 1980. On the stratigraphy of the Karelian geol. Finlande 98. 30 p. formations. In: latulian geology in the eastern part Silvennoinen, A., 1972. On the stratigraphie and struc­ of the Baltic Shield. Ed . by A. Silvennoinen. The tural geology of the Rukatunturi area. northeastern Committee for Scientific and Technical Co-operation Finland. Geol. Surv. Finland, Bull. 257. 48 p. between Finland and the Soviet Union. 197 - 112. Silvcnnoincn, A., Honkamo, M., Juoppcri, H. , Lehtonen, Mt'tzger, A., 1924. Die lallilischen Bildungen von Suo­ M., Mielikäinen, P., Perilunen, V., Rastas, P., Räsä• järvi in Ostfinnland. BuH. Comm. geol. Finlande 64. nen, J. & Väänänen, J. , 1980. Main features of the 86 p. stratigraphy of North Finland. In: latulian geology Geological Survey of Finland, Bulletin 336

Stratigraphie studies on the Precambrian in Finland 37

in the eastern part of the Baltic Shield. Ed. by A. Tigerstedt, A., 1892. Om traktens mellan Höyti äi nen och Silvennoinen. The Committee for Scientific and Pielisjärvi geologiska och topografiska byggnad , samt Technical Co-operation between Finland and the nägra därstedes förekommande malmförande kvarts­ Soviet U nion , 153 - 162 . gängar. Fenni a 5. 22 p. Simonen, A., 1948. On the petrology of the Aulanko area Tynni, R. & Donner, J., 1980. A microfossil and sedi­ in southwestern Finland. Bull. Comm . geol. Finlande mentation study of the Late Precambrian formation 143. 66 p. of Hailuoto, Finland . Geol. Surv. Finl and, Bull . 31 1. 1953. Stratigraphy and sedimentation of the Sveco­ 27 p. fennidic, earl y Archean supracrustal rocks in south­ Väyrynen, H., 1933. Über die Stratigraphie der Kare­ western Finland. Bull. Comm. geol. Finl ande 160 . li schen Formationen. Bull Comm. geol. Finlande 101 , 64 p. 54-78. 1955. Lexique stratigraphique international. Europe, 1939. On the geology and tee tonics of the Outokumpu Fascicule 2b , Finlande, 89 - 10 I. ore field and region. Bull. Comm. geol. Finlande 124. 1960. Pre-Cambrian stratigraphy of Finland. XXI. Int. 91 p. Geol. Congress , Norden 1960, Section 9, 141 - 153 . 1954. Suomen kallioperä , sen synty ja geologinen 1971. Das finni sche Grundgebirge. Geol. Rundschau kehitys. Otava. Helsinki . 260 p. 60, 1406- 1421. Vorrna, A. , 1975. On two roof pendants in the Wiborg 1979. Lehti 3 133 Ylämaa, Suomen geologin en kartta rapakivi massif, southeastern Finland. Geol. Surv. I : 100000. Finland, Bull. 272. 86 p. 1980. The Precambrian in Finland. Geol. Surv. Fin­ Wahl , W. , 1936. The granites of the Finnish part of the land , Bull. 304. 58 p. Svecofennian Archaean mountain chain . Bull. Comm. Simonen, A. & Kouvo, 0 ., 1955. Sandstones in Finland. geol. Fi nl ande 11 5, 489- 505. Bull. Comm. geol. Finlande 168 , 57 - 87. Wegmann, E., 1928. Über die Tektonik der jüngeren Taipale, K., 1982. Kuhmon arkeeinen vi hreäkivigranitoi­ Faltung in Ostfinnland. Fennia 50. 1- 22. diaJue. Osa 1. Tipasjärvi - Hietajärvi. Arkeeisten alu ei­ Wegmann, E. & Kranck, H. , 1931. Beiträge zur Kenntnis den malmiprojekti . Oulun yliopisto. Raportti 4. 143 p. der Svecofenniden in Finnland. Bull. Comm. geol. Taipale, K. & Tuokko, 1., 1981. Kuhmon arkeeisen vih­ Finlande 89. 107 p. reäkivivyöhykkeen geologiasta ja malmimineralisaa­ Wiik, F., 1874. Om östra Finlands primitiva formationer. tioista. Kuhmon ja Kittilän malmiprojektit. Oulun Bidrag till kännedom af Finl ands natur och folk 2 1, yli opisto. Raportti 47 . 65 p. 231 - 295. Geological Survey of Finland , Bulletin 336

Ahti Simonen

APPENDIX

EXPLANATION OF THE TERMS

by Ahti Simonen and Car ola Eklundh

Bothnian. The name was proposed by Sederholm unconformity. The rocks of the Lower Jotnian sub­ (1893) for the rock complex regarded as intermediate division have also been named sub-Jotnian or Hoglandian. between the oldest gneissose gra nites a nd the younger Kainuan. The term was proposed by Väyrynen ( 1933) granites of the second group in southern Finland. It for the quartz conglomerates a nd quartzites that belong was thought that the 80thnia n complex was separa ted to the JalLllian formations and overli e the Sariolian a nd by 3 great unconformity from the underlying Svionia n underlie the marine Jatulian formations. See p. 30. complex. Later investiga tions have proved that the Kalevian. The name was first proposed by Ramsay gneissose granites penetrate the 80thnia n roeks and ( 1902) and Frosterus ( 1902) for the rocks that were there is no marked unconformity between the Svionian supposed to be older than the Jatulia n but younger than a nd the 80thnian . At present. the Proterozoie 80thnian the Ladogia n . . The Kalevian fl ysch-type sediments and Svionian complexes a re designated by a eollective belong to the Karelian supergroup and Väyrynen ( 1933) name, Svecofennian. See p. 33. has shown that they overlie the l atulia n deposits un­ Eo-J atulian. See: Jatulian. conformably. See pp. 29- 30. Hoglandian. The name was proposed by Sederholm Karelian. The term was proposed by Eskola ( 1921 ) ( 1927) for certain nonmetamorphie Precambria n sedi­ as a collective name for the Jatulia n, Kalevian a nd ments and rapakivi granites containing effusives, Ladogian deposits. which were eonsidered to belong which unconfo rmably underlie the Jotnia n sandstones to the same cycle of orogenie sedimentati o n. At present , in southem Finland. The names sub-Jotnian and Lower the Karelian deposit s . the subdivision of whi ch is Jotnian have also been applied to the Hoglandian. di seussed in pages 29 - 31, are regarded as sediments See p. 34. of the Svecokarelidie orogenie cyele. The Jatulian Ipa tti fo rmation. The name was proposed by Väyrynen group represents an evolutionary phase of sedimenta tion. ( 1933) for the oldest metasediments and metavolcanics whereas the Kalevia n roeks a re geosynclinal sediments in eHstern Finland. The rocks of the Ipatti formation occur of the Svecokarelides. as narrow schist zones in the gneisso e granite (base­ Karelides. The sc hi st belt trending from Lake Ladoga me nt gneiss) area of eastern Finland. which forms the across eastern Finland int o Lapland and consisting of the floor for the Karelian sedimentation. See p. 27 . metamorphie a nd folded Karelian sediments a nd Jatulian. The name was proposed by Sederholm (1897) volcanics. which a re penetrated by orogenie plutonie for the youngest Preca mbrian sedimentary deposit s in rocks. The Karelides a re part of the Svecokarelides. east,~rn Finland. Metzger ( 1924) subdivided the Jatulian See pp. 28. fr om the lowest to the uppermost formations: Eo­ Karelidic. Adjective for those rocks that have take n Jatu lia n. Meso-Ja tulia n a nd Neo-Jatulian. Väyrynen part in the orogenie movements in the Ka relidie belt of ( 1933) pointed out that the Ja tuli an rocks represent the the Svecokarelides. lowest stratigraphie unit of the Kare li a n deposits and Katarchean. The term was proposed by Sederholm that they are separated by an unconformity fro m the (1897) for the o ldest Archean pre-Bothnian basement overlying Kalevian sedime nt s. He subdivi ded the complex. See p . 27. Jatu lian into Sariolian. Kainuan and marine JalLllia n Kellojärvi group. This group overlies the Luoma group formations. Nowadays. the Sarioli an is separated from and underlies the Ontojärvi group in the Archean Kuhmo the overl yi ng Jatuli an as a n independent group a nd the greens tone bell. The group is subdivided into the lower Jatulian group is subdivided by volcani e interbeds Pa ha kangas and the upper Siivikko formations (Taipale & (Fig. 3). See p. 30. Tuokko 1981 ). See p. 28. Jotnian. The name was proposed by Sederho lm ( 1897) Kuhmoidic schists. The name was proposed by Sim onen for all those Precambria n deposits that had not undergone ( 197 1) for the Early Precambrian (Archean). pre-Sveco­ diastrophism during the Precambrian. Later. Seder­ karelidi e metasediments a nd metavolcanic s whi e h a re holm subdivi ded the Jotnian into the Upper lotnian penetrated by granitoids of the age group 2 600- 2 800 (red arkose sandstone) and Lower Jotnia n (ra pa kivi Ma . See p. 28. with effusives), which are separated by the sub-Jot ni an Kumpu formation. The term was used by Hackma n Geological Survey of Finland, Bulletin 336

Stratigraphic studies on the Precambrian in Finland

(1927) for those coarse-grained quart zites a nd conglom­ (Kuhmoidic schi sts) a nd gneissose granitoids (basement erates in La pla nd that are the youngest Preca mbrian gneisses). (probably Jatulian) metasediments of the area. According Sariolian. The term was proposed by Eskola (1919) to some geologists (Mikkola 1941 and Eskola 1941), the for the tillite-like conglomerates and arkoses that rocks of the Kumpu formation may represent the uderlie the Jatlilian sediments in East Karelia and are molasse sediments of the Karelian sedimentation. basal deposits Iying on the pre-Karelidic basemenl. Silvennoinen et al. (1980) considered the Kumpu forma­ Väyrynen (1933) designated the similar polymict con­ tion to be Jatulia n. glomerates in Finland as »Sariolian facies» of Jatulian. Ladogian. The name was proposed by Sederholm (1897) Recent investigations (cf., Pekkarinen 1979 and Meri­ for highly meta morphic schists and gneisses north of lä inen 1980) separate the Sariolian from the Jatulian !...ake Ladoga, and it was supposed that the Ladogian as an independent grollp deposited on the pre-Sveco­ rocks are older than the Jatulian. Eskola (1921) included karelidie basement and underlying the Jatulian group. the Ladogian rocks in the Karelian formation . Seder­ See p. 30. holm ( 1932) assumed that the Ladogian is older than Svecofennian. The name was used as a collective the Kalevian. However. no unconformity has been found na me for the Svionian a nd Bothnian complexes of between the Kalevian a nd the Ladogian. It is probable sOllthern Finland th at belong to the same cycle of that the Ladogian rocks only represent more meta­ orogenie sedimentation. Nowadays, the Svecofennian morphosed varieties of the Kalevian sediments. See deposits, which are subdivided into Lower, Middle a nd pp. 29. Upper Svecofennian successions, are regarded as Lapponian. The name was proposed by Sederholm geosynclinal deposils of the Svecokarelides (cf. Simonen (1932) for quartzites. mica schists and greenstones in 1960 and 1971 ). Lapland which were supposed to be older than the Svecofennides. The schist belt trending from Pohjan­ Kareli a n (Jatulian) sediments. According to Mikkola maa into southern Finland and consisting of the meta­ ( 1941 ). the Lapponian rocks seem to be deposited upon morphosed and folded Svecofennian sediments and the pre- Karelidie basement and they may belong to the volcanics that a re penetrated by orogenic plutonic rocks. Karelian cycle of sedimentation. Silvennoinen et al. The Svecofennides a re part of the Svecokarelides. (1980) considered the Lapponian schists to be Archean Svecofennidic. Adjective for the rocks that have deposits, older than the Karelian . However, Lauerma undergone the orogenic movements in the Svecofennidic ( 1982) has remarked that the Archean age of the Lappo­ belt of the Svecokarelides. nian is di sputable. Svecofenno-Karelian. First proposed by Simonen Lower Jotnian. See: Jotnian. ( 1960), it was la ter replaced by the shorter term Sveco­ Luoma group. The lowest stratigraphie group of the kareli a n. Archean Kuhmo greenstone belt (Taipale & Tuokko Svecokarelian. The term was proposed by Simonen 198 1). See p. 28. (1971) as a collective name for the Ka relian and Sveco­ Marine Jatulian. Applied to dolo mites and pelites that fennian formations that represent different types of form the upper part of the Jatulian. The marine Jatulian deposits belonging to the same Svecokarelidic orogenic includes Metzger's Meso- and Neo-Jatulian formations. cycle (Svecokarelides) . See p. 30. Svecokarelides. The a ncient Proterozoie orogenie Meso-Jatulian: See: Jatulia n. belt of metamorphosed a nd folded Karelia n a nd Sveco­ Muhos formation. Applied to the nonmetamorphie fennian sediments and volcanics that have been intruded sedimentary deposits (mainl y siltstones a nd sha le s) in by orogenic plutonic rocks. northern Pohjanmaa. Brenner (1941) assumed tentatively Svecokarelidic. Adjective for the rocks that have a Mesozoie age for the Muhos formation , but in later in­ undergone the orogenie movements of the Sveco­ vestigations (cf., Simonen & Kouvo 1955) the Muhos for­ ka relides. mation is correlated to the Precambrian, (Upper) Jotnian Svionian. The term was proposed by Sederholm ( 1920) formations. for the oldest rock comple x in southern Finland, and Neo-Jatlllian. See: Jatlllian. it was supposed that the Svionian complex was separated Ontojärvi group. The uppermost stratigraphi e groliP by a great lInconformity from the overlying Bothnian of the Archean Kuhmo greenstone bell. The grollp is complex. Later. both the Svionian a nd the Bothnian s ubdivided into the lower JlIurikkaniemi and upper complexes have been included in the collective term Petäjäniemi formations (Taipale & Tuokko 1981 ). See Svecofennian. See p. 33. p. 28. Sub-Jotnian. See: Jotnian. Pre-Svecokarelidic basement. The Archean folded area Upper Jotnian: See: Jotnian. in eastern a nd 11 0rthern Finland. consisting of the silicic. Urkkavaara formation. A glaciogenic deposit in the intermediate. mafic and 1Iitramafic metavolcani cs. upper part of the Sariolian group (Marmo & Ojakangas komatiites. graywacke schislS and iron formations 1984).