Lower Proterozoic Glaciogenic Deposits, Eastern Finland

Lower Proterozoic glaciogenic deposits, eastern Finland

JUKKA S. MARMO Geological Survey of Finland, 02150 Espoo 15, Finland RICHARD W. OJAKANGAS Department of Geology, University of Minnesota, Duluth, Minnesota 55812

ABSTRACT Urkkavaara Formation (Marmo and Ojakangas, sedimentary horizon exposed on both sides of a 1983) of the Sariolian Group in the lower part domal structure of basement rock. Interestingly, In the lower Proterozoic Sariolian Group of the Karelian Supergroup near Joensuu in Eskola as early as 1919 pointed out that glacia- of eastern Finland, the metasedimentary eastern Finland (Fig. 1). The formation crops tion could have been a process in the formation Urkkavaara Formation possesses the attri- out in several places along 2 narrow belts each of some Sariolian till-like conglomerates in East butes of a glaciogenic deposit. Within the ~6 km long. The two belts represent the same Karelia (Soviet Union). formation, four members have been estab-

lished—a lower siltstone-argillite member, KALEVIAN ROCKS [V^ URKKAVAARA FORMATION OVER THRUST a graded sandstone member, an upper silt- ARCHEAN ^ MAJOR FAULT stone-argillite member, and a diamictite |: : : ': : ] JATULIAN ROCKS BASEMENT ROCKS member. The lowest three members contain MAJOR UNCONFORMITY lonestones. The upper siltstone-argillite mem- I I SARIOLIAN ROCKS BASIC DIKES ber passes gradually over 1 m into a massive diamictite. NORWAY Many lonestones in the siltstone-argillite members are clearly dropstones. These members, and their association with diamictite, constitute strong evidence for a glaciogenic origin for the formation. The vertical transition of siltstone-argillite into diamictite indicates a similar "raining-down" mechanism of deposition for the diamictite. The thickness of the formation, 30 to 60 m (minimum), suggests deposition from icebergs, rather than from seasonal ice, for the laminated members and the diamictite. The graded sandstone member is interpreted to be a result of turbidity current deposition near a glacial terminus. A glaciomarine environment is suggested. Lonestone-bearing units and diamictites in the Soviet Union just east of Finland have recently been reinterpreted as glaciogenic deposits. There appears, therefore, to have been an early Proterozoic continental glaciation about 2,500 to 2,300 m.y. ago on the Baltic Shield, approximately the same time that early Proterozoic glaciation occurred in North America.

INTRODUCTION

Glacial deposits of early Proterozoic age have been identified in Finland for the first time. These conglomerates, sandstones, and argillites were originally identified informally as the met- aconglomerate member of the metaconglom- erate-arkose-quartzite formation, part of the Jatulian Group (Piirainen and others, 1974; Figure 1. Geologic map of the Urkkavaara area (southwest part of the Koli-Kaltimo area, Marmo, 1981), but they are here assigned to the North Karelia), eastern Finland.

Geological Society of America Bulletin, v. 95, p. 1055-1062, 11 figs., September 1984.

1055

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Figure 2. Simplified diagrammatic stratigraphic section of the Karelian Supergroup in eastern Finland, including the Sariolian, Jatulian, and Kalevian Groups. See text for ranges in thick- nesses. Diagonal line in Sariolian column illustrates variation in stratigraphy. 1. Karelian basement. 2. Basal conglomerate. 3. Conglomerate. 4. Arkosite. 5. Greenstone. 6. Orthoquartzite. phyllites and micaschists 7. Sericite quartzite. 8. Dolomite. 9. Black schist. 10. Phyllite Kalevian graded-bedded quartzite mica schist layers and mica schist. The location of the Urkkavaara Formation is conglomerate shown in the upper Sariolian Group. A. Diamictite. B. Siltstone- •2000Ma-uriconformity- greenstone argillite with abundant lonestones. C. Graded sandstone with dolomite few lonestones (after Merilainen, 1980). black schist,phyllite dolomite quartzite

URKKAVAARA FORMATION

diamictite member greenstone orthoquartzite sericite quartzite upper siltstone- conglomerate argillite member 2300Ma-unconforinity arkosite conglomerale graded sandstone member

greenstone lower siltstone- argillite member

, )ower arkosite conglomerate

2500Ma-major unconformity basement

REGIONAL SETTING, Lithologic symbols STRATIGRAPHY, AND STRUCTURE S1 IS) 3 EZ)5

• 6 Eg 8 S9 E3I0 In eastern Finland, the Presvecokarelidic basement complex of the Baltic Shield consists of schists (mainly mafic metavolcanic rocks), consists of a sequence of texturally and minera- region to the west of the relatively narrow, paragneisses, and orthogneisses. This complex logically immature to moderately mature ar- north-south-trending belt of Sariolian and Jatu- forms the basement upon which the Karelian koses and conglomerates with a middle mafic lian rocks. Supergroup was deposited (Fig. 2). U-Pb dates volcanic unit. The Sariolian Group in the Soviet The Sariolian arkoses and conglomerates for the basement rocks are 3000 to 2500 m.y. Union consists of 300 to 800 m of sedimentary have been interpreted as fluvial deposits (Pekka- B.P., but some as old as 3,500 m.y. have been rocks and as much as 1,200 m of mafic volcan- rinen, 1979), whereas the overlying Jatulian reported from the Kola Peninsula, Soviet Union, ics (Salop, 1983, p. 138). In eastern Finland, it is quartzites and related rocks appear to have been in the northeastern part of the shield (Simonen, locally as thick as 400 m but is usually 100-150 deposited during a marine transgression (Oja- 1980). m thick (Pekkarinen, 1979). kangas, 1965; Pekkarinen, 1979). The Kalevian Division of the rock sequences on the Baltic The Sariolian Group is overlain unconforma- Group has long been interpreted as a deeper Shield into groups and formations apparently bly by the much more mature Jatulian Group marine accumulation. has not been done as rigorously as the Code of that consists of orthoquartzites, sericitic ortho- The Karelian Supergroup in eastern Finland Stratigraphic Nomenclature prescribes for North quartzites, and minor conglomerates, dolomites, has been compressed eastward against the Pres- American rock sequences. and black schists (Fig. 2). The Jatulian, which vecokarelidic basement rocks, and broad, open The Karelian Supergroup (Salop, 1983, also contains mafic volcanics, overlaps the Sari- anticlines and synclines have developed; base- p. 134) to the east in Karelia, Soviet Union, olian Group and was deposited upon the pene- ment rocks are now exposed in axii.l culmina- consists of six groups of sedimentary and vol- planed Presvecokarelidic basement and upon tions (Simonen, 1980). The folding has been canic rocks, but in eastern Finland the lowest the Sariolian rocks, with regolith development complicated by thrust faulting (Vayrynen, 1954; group apparently is not present and the Sariolian at the contact (Ojakangas, 1965; Pekkarinen, Gaal, 1964; Gaal and others, 1975). and some Group (called the Arkosite Formation by Pek- 1979; Simonen, 1980; Marmo, 1981). The Jatu- structures in the study area appear to be nappes. karinen, 1979) rests directly upon the basement lian is several thousand metres thick in the So- High-angle faulting, some probably representing (Fig. 2). In Finnish Lapland, the metasedimen- viet Union (Salop, 1983, p. 138) but is < 1,000 old lineaments (Piirainen and others, 1974) that tary-metavolcanic Lapponium Group (Silven- m thick in Finland (Pekkarinen, 1979). may have been reactivated from time to time, noinen, 1972) apparently is equivalent to the The Jatulian Group is overlain by several further obscures the original stratigraphic rela- lowest group, the Tunguda-Nadvoitsa (Sumi) thousand metres of graywackes and mudstones tionships. All of the sedimentary rock units dis- Group of Salop (1983). The Sariolian Group of the Kalevian Group, which underlies a broad cussed herein have undergone polyphase low-

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grade regional metamorphism (Marmo, 1981). Group, including the Urkkavaara Formation, of Sariolian sediment. Although the area is struc- Nevertheless, original sedimentary structures are probably was deposited between 2,450 and turally complex, the upper Sariolian arkoses and generally well preserved. As this report deals 2,300 m.y. ago. conglomerates are at least several tens of metres with the original sedimentational history of the All of the rock units discussed above were thick. Urkkavaara Formation, premetamorphic rock intruded, folded, and metamorphosed about Four informal members have been distin- names generally will be used herein. 1,900 to 1,850 m.y. ago in the Svecokarelidic guished in the Urkkavaara Formation (Marmo event (Simonen, 1980). and Ojakangas, 1983) as follows, with the dia- AGE mictite at the top: ROCK DESCRIPTIONS Radiometric age determinations have not Diamictite member 1-10 m been made on rocks of the Urkkavaara Forma- Field relations show that the Urkkavaara Upper siltstone-argillite member 2-40 m tion. Based on lithostratigraphic mapping and Formation was deposited upon conglomerates Graded sandstone member 10-15 m correlations in eastern Finland, the age of the and arkoses in the lower part of the Sariolian Lower siltstone-argillite member > 15 m. Sariolian Group is between 2,500 and 2,300 Group; it is also possible that locally it rests m.y. These ages, reviewed by Merilainen upon Archean basement gneiss, but such a con- The two siltstone-argillite members, now (1980), are dates on the weathering crust on the tact has not been observed. The formation has a mica schists but still displaying some original upper Sariolian rocks and the minimum age of total thickness of 30 to 60 m and is overlain by clastic textures, are very similar. They consist of the Presvecokarelidic basement rocks (Fig. 2). unnamed parallel-bedded and cross-bedded ar- straight laminations of gray siltstone and darker Other relevant dates are as follows. In northern koses and small-pebble conglomerates of the gray argillite with variable amounts of quartz, Finland, mafic intrusions that cut the basement upper part of the Sariolian Group, as described feldspar, biotite, and sericite. Many of the silt- rocks but are older than the overlying Karelian in the region by Pekkarinen (1979). This upper stone laminae exhibit graded bedding that is sedimentary rocks have been dated at 2,450 to contact is an erosional surface, and so the Urk- clearly visible in thin sections, with grain sizes of 2,430 m.y., and diabase dikes in eastern Finland kavaara was thicker at one time. Stratigraphic 0.1 to 0.2 mm grading upward to sizes of 0.05 to that cut the Jatulian sedimentary rocks are relationships suggest that the relief on the con- 0.02 mm. Oversized clasts (lonestones) as large 2,200 to 2,000 m.y. old (U-Pb dates by Kouvo, tact could be as great as a few hundred metres, as 20 cm are scattered but common; pebbles and in Simonen, 1980). These dikes were dated at but it has not been possible to verify this in cobbles, generally of felsic plutonic rocks (Figs. 2,160 to 2,150 m.y. by Sakko (1971), who used outcrop. 3 and 4) and coarse sand grains, generally feld- the U-Th-Pb method on zircons. In the Soviet The original thickness of the overlying upper spar or quartz, are the most abundant. Also Union, the Jatulian rocks (Segozero and Onega Sariolian rocks is unknown for several reasons. present are elongated phyllitic clasts as long as Groups) were formed between 2,450 and 2,180 They grade upward into a pre-Jatulian weather- 10 cm. Another type of lonestone consists of m.y. ago, on the basis of a Pb-Pb date of 2300 ± ing crust (Fig. 2) that now is a kyanite- generally small graywacke (sand-silt-clay) grains 140 m.y. B.P. for stromatolitic dolomites in the andalusite-quartz schist (Marmo, 1981). Expo- that are now sand-silt-mica aggregates. upper Jatulian (Onega Group) and dates of sures are on the anticlinal hinge of a gently The graded sandstone member now consists 2180 to 2160 m.y. B.P. on zircons from mafic plunging antiform, and real thickness is difficult of intercalated beds of arkosic quartzite, biotitic dikes that cut the upper Jatulian rocks (Salop, to measure. After deposition of the Sariolian quartzite, and biotite-rich metasiltstone. The 1983, p. 139). Assuming the regional correla- Group, at least two tectonosedimentary episodes sandstone beds are 10 to 40 cm thick and com- tions and the dates are correct, then the Sariolian have resulted in the reworking and redeposition monly display good grading (Fig. 5). Oversized

Figure 3. Granitic lonestone in upper siltstone-argillite member. Note downwarping and slight piercement of the laminae beneath the Figure 4. Lonestones in lower siltstone-argillite member. Note stone and the draping of laminae over the stone. The coin is 24 mm in downwarping of laminae under largest granitic lonestone and varve- diameter. like, graded appearance of some laminae. Coin is 24 mm in diameter.

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Figure 5. Graded beds in graded sandstone member. Note the large lonestone; more commonly, lonestones are found in argillaceous Figure 6. Diamictite. Stratigraphie top is up. Note lack of bedding. laminae between graded beds. Coin is 25 mm in diameter. Planar feature iis foliation that is subparallel to bedding. White clast at top is 10 cm in longest dimension.

clasts (lonestones) are present but not common base (greenstone). The boundaries of the gray- torted angular slabs of thinly laminated silt- in this member. The original outlines of the wacke (sand-silt-clay) clasts with the matrix are stone-argillite similar to that making up the silt- sand-sized grains are generally visible. indistinct, partly because of original primary tex- stone-argillite members. A representative sandstone of the graded tural gradation (see Ovenshine, 1970), and sandstone member of the Urkkavaara Forma- partly because of recrystallization. The diamic- CHEMISTRY tion is composed of 45% quartz, 24% feldspar, tite lacks original internal structures but locally and 28% micas (originally clayey matrix). The contains a few sandstone lenses. The contact of Three major-element chemical analyses are quartz to feldspar to lithic fragment ratio the diamictite with the underlying sillstone- available for the Urkkavaara Formation, allow- (Q:F:L) among the sand-sized grains is 65:35:0. argillite member is clearly gradational over less ing comparisons with possible SOUK« rocks of Other sandstones of the Sariolian Group contain than 1 m (Fig. 8). Locally, the diamictite imme- the Presvecokarelidic basement complex and 40% to 71% quartz, zero to 41% feldspar, and diately overlies chaotic beds composed of dis- other units of the Sariolian Group (Fig. 9), The 14% to 40% micaceous matrix (Pekkarinen, 1979). In contrast, sandstones of the overlying Jatulian Group contain 50% to 98% quartz, zero to 18% feldspar, and 3% to 63% micaceous matrix; about one-half contain no feldspar (Oja- kangas, 1965). A small part of the micaceous matrix may be totally sericitized feldspar. The diamictite member is characterized by very poor sorting, with the grain size ranging down from boulders as large as 60 cm to silt- and clay-sized grains (Fig. 6). The matrix is a gray wacke; the amount of matrix varies between 50% and 80%, resulting in a matrix-supported framework. A representative matrix sample consists of 13% quartz, 8% feldspar, 23% rock fragments, and 55% matrix (39% micas and 16% fine quartz and feldspar), with most detrital sand grains subangular to angular (Fig. 7). The Q:F:L ratio is 30:18:52, but one-third to one-half of the lithic fragments are composed of quartz in granitic fragments, so that the quartz content is higher than the ratio indicates. The boulders, cobbles, and pebbles vary from subangular to rounded; -90% consist of basement gneiss with minor siltstone, phyllite, graywacke, and vein Figure 7. Photomicrograph of diamictite matrix. Clasts are quartz, feldspar, arid granitic quartz. Also present are rare clasts of albite dia- rock fragments in a micaceous matrix. Nicols uncrossed. The field of view is 25 mm across.

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high—for example, 88 to 98, as in lutites from the Amazon River cone—it signifies highly weathered source materials and a warm climate. The ratios for diamictite matrix and siltstone-argillite of the Urkkavaara Formation are 60.3 and 63.2, suggestive of relatively moderate weathering as in the Gowganda Formation.

ENVIRONMENTAL INTERPRETATIONS

Many of the lonestones (Figs. 3 and 4) in the siltstone-argillite members have either pierced or bent downward the laminations beneath them. The laminae above the lonestones are either hor- izontal, as in Figure 3, or gently arched, as in Figure 4. These relationships do not appear to be the result of compaction during sedimentation-burial or during tectonism, for the piercement is present only on the lower sides of the clasts. The lonestones, therefore, are interpreted to be dropstones, dropped from above into silt and clay by floating icebergs and/or shelf ice. A Figure 8. Gradational contact of upper siltstone-argillite member and overlying diamictite special type of dropstone is the sand-silt-clay member. Note total lack of bedding in the diamictite. Compass is 12 cm long. clasts described above; these are probably till pellets that formed on or in melting ice and were CaO Si02 contents of the diamictite matrix and the sedimented as soft, discrete aggregates (Oven- graded sandstone (arkosic quartzite) are high shine, 1970; Goldstein, 1983). (75% and 73%), and, together with the petro- The vertical gradual transition from the graphic data, they indicate a granitic source. The siltstone-argillite unit with dropstones into the

Ca0:Na20:K20 plot (Fig. 9) emphasizes the overlying diamictite (Fig. 8) strongly suggests potassium enrichment of the siltstone-argillite, that the diamictite was formed by the same and especially the diamictite, relative to the "raining-down" mechanism (suspension fallout basement granitic rocks, with the potassium of clay and silt—that is, rock flour—from a col- probably originally present in illitic clays that umn of water), but at a faster rate, in the ab- since have been metamorphosed to sericite. The sence of bottom currents that would have sorted Na20 K2O only other rocks with comparable ratios are two the debris to some degree. Coarser detritus is Sariolian arkosites, suggesting a possible deriva- interpreted to have been dropped directly from Figure 9. Alkali plot for Prekarelidic base- tion of some detritus from those older sediments icebergs or shelf ice. Diamictites can, of course, ment rocks, Sariolian Group arkosites, and rather than directly from Prekarelidic basement. be formed by several mechanisms, including the Urkkavaara Formation. Sample numbers Both diagenesis and metamorphism complicate subaerial or submarine slumping. Subaerial, and their sources are as follows. 1. Prekare- such interpretations, however. subglacial, or subaqueous, viscous, muddy flows lidic gneissose quartz granite (Pekkarinen, The matrix of the Urkkavaara diamictite is can deposit flow tills. These mechanisms, how- 1979, p. 52). 4. Prekarelidic granite (Pek- chemically quite unlike that of the diamictites of ever, would have resulted in the diamictite hav- karinen, 1979, p. 52). 6. Prekarelidic mica the lower Proterozoic Gowganda Formation of ing a sharp and perhaps erosional lower contact gneiss (Pekkarinen, 1979, p. 52). 8. Prekare- Ontario, which have high soda contents, but are with the underlying sediment. lidic basement rocks, approximate weighted somewhat similar chemically to two slightly The graded beds of the graded sandstone average (Pekkarinen, 1979, p. 52). 9. Aver- older Proterozoic diamictites in the same se- member are interpreted to have been deposited age of 173 Prekarelidic gneissose granites in quence in Ontario (Robertson, 1981). by turbidity currents that were moving and sort- Soviet Karelia (W. Z. Negrutsa, 1974, in A CIA Index (chemical index of alteration) ing sediment either previously deposited in a Pekkarinen, 1979, p. 52). 10. Arkosite, Sario- has been proposed by Nesbitt and Young subaqueous near-glacial environment (Boulton lian (Pekkarinen, 1979, p. 75). 11. Arkosite, (1982). If the ratio of molecular proportions of and Deynoux, 1981, p. 410) or exiting from

Sariolian (Pekkarinen, 1979, p. 75). GS. A1203 to A1203 + CaO + Na20 + K20 x 100 is tunnels beneath a grounded glacier. Several Graded sandstone (arkosic quartzite, light- low—for example, 50 to 73, as in lutites and other workers have also documented turbidites colored), Urkkavaara Formation (analysis by diamictite matrix from the Gowganda Forma- near glaciers. They are present in the proximal V. Hoffren). SA. Siltstone-argillite, Urkka- tion, or 51 to 65 for Pleistocene lutites and glacial-marine zone (within 2 to 3 km of the ice vaara Formation (analysis by V. Hoffren). D. tills—it signifies relatively unweathered source front) in Quaternary deposits along eastern Baf- Diamictite, Urkkavaara Formation (analysis materials and probably a cool climate. The fin Island (Mode and others, 1983). They consti- by V. Hoffren). index is 70-75 for average shales. If the index is tute a proximal turbidite channel facies in late

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icebergs

Figure 10. Simplified diagrammatic model of deposition of the three facies of the Urkkavaara Formation.

floating glacier in a body of water containing icebergs (Fig. 10). In this model, the lower DIAMICTITE SILTSTONE - GRADED siltstone-argillite facies would have been depos- FACIES ARGILLITE SANDSTONE ited in front of the glacier as a silt-clay rhythmite CDROPSTONE) FACIES sequence. The graded sandstone facies may have FACIES been deposited closest to the glacier front, and as Pleistocene glacial-marine sediments in the Some types of diagnostic glaciogenic charac- the glacier advanced in this area, the graded Puget Lowlands of Washington (Domack, teristics, including striated and faceted rock sandstone facies was laid down on top of pre- 1983). Turbidity currents may also be generated fragments and glacially scoured paleobedrock viously deposited siltstone-argillite. A glacial re- from slumps off delta foreslopes or from mar- surfaces, were searched for but were not ob- treat brought the return of laminated siltstone- ginal stream discharges, as observed in Alaska served in the Urkkavaara Formation. In meta- argillite deposition (Fig. 11). Grading in silt- by Powell (1983). Eyles and Eyles (1983) de- morphosed and folded rock units with nappe- stones of the two siltstone-argillite members scribed glaciolacustrine associations of turbidites type structures, however, the identification of suggests that some siltstones can be interpreted and diamictites. The presence of rare lonestones such criteria should be especially difficult. Cer- as more distal deposits of the same turbidity cur- in this unit as well indicates a continuity of the tain other distinguishing characteristics of gla- rents that deposited the thicker graded beds of rafting mechanism. ciomarine-glaciolacustrine deposits that require the graded sandstone member. Continued gla- Thin, graded, varve-like laminae in the the study of unconsolidated sediment, as sum- cial retreat resulted in a more distal aqueous siltstone-argillite units are visible despite the marized by Andrews and Matsch (1983), are environment in the study area and deposition of metamorphism. These may be the fine-grained not readily applicable to this metamorphosed the diamictite facies (Fig. 11). The diamictite basin ward equivalents of the turbidites described unit. We emphasize that the presence of abun- accumulated as a result of ari increased coarse above, but the paucity of outcrops does not dant dropstones in thinly bedded units asso- clastic to fine clastic ratio as debiis dropped allow verification of this hypothesis. If they are, ciated with diamictites (Hambrey and Harland, from numerous melting icebergs dominated over indeed, varves rather than thin, graded turbidity- 1981, p. 14) is among the best evidence that can suspension fallout debris from wateis that were current or storm-suspension deposits, they imply be found in any rock unit to support a glacio- already somewhat depleted ir suspended mate- either a glaciolacustrine or a nearshore marine genic origin. rial because of fallout closer to the glacial front, environment where melt water reduced the sa- as modeled by Boulton and Deynaux (1981, p. 408 and 410). linity and thereby inhibited flocculation of clays. DEPOSITIONAL MODEL The minor chaotic units composed of lami- This model is, admittedly, simple and preli- nated siltstone-argillite slabs are interpreted as It is presumed on the basis of paleocurrent minary, but yet solidly based upon Walther's slump deposits associated with instability in measurements in the overlying Jatulian quart- Law that states that the vertical facies reveal the areas of relatively rapid sedimentation (Boulton zites in this region that sediment was transported lateral facies changes. As we do further mapping and Deynoux, 1981, p. 410). Local grounding northwestward and southwestward (Mikkola, and study in the area, we will reappraise the of glaciers or icebergs probably could form such 1955; Ojakangas, 1965; Pekkarinen, 1979). validity of the model. Additional field data ac- chaotic units by pushing the substrate. The ab- Thus, the currents moved, in general, from the cumulated during continued work in the area sence of lithologies interpreted as outwash de- east toward the west, off the Karelian massif or undoubtedly will necessitate a reappraisal, and a posits within the Urkkavaara Formation argues "Jatulian Continent" of Vayrynen (1954). Pre- more complicated model should result. An al- against proximity to a glacial front, and iceberg liminary field observations by us of cross- ternative preliminary model would place the grounding may be a more plausible hypothesis. bedding in other rocks of the Sariolian Group graded sandstone facies (that is, turbidites) in a The thickest measured section of the Urkka- also suggest a general westward fluvial transport distal location on a flat basin floor and the dia- vaara Formation is ~60 m, but the bottom of of sediment over a gentle paleoslope that sloped mictites in a location proximal, to the glacier. On the formation is not commonly exposed, and the seaward toward the west. It seems logical to us the basis of the information now available, we lower siltstone-argillite unit may be considerably that the ice probably moved westward off the believe our model is viable and preferable; how- thicker. Furthermore, the contact of the overly- peneplaned and weathered Karelian massif. ever, the cited alternative model must be re- ing rock with the Urkkavaara Formation is ero- Glacial loading resulted in isostatic depression of tained as a possibility until additional data on sional. The formation thus may have been the area during Urkkavaara time and a marine lateral facies changes allow for reassessment. considerably thicker, probably totaling 100 m or transgression. We see no evidence for high relief The glaciogenic Urkkavaara Formation was more, with probable ice-rafted debris through- during that time, as would be expected with succeeded by cross-bedded and parallel-bedded out. The total volume of sediment argues against mountain glaciation and a fjord model. arkoses and conglomerates, and the contact is seasonal ice (shore ice or sea ice) as a major We suggest that the Urkkavaara Formation erosional. We have not fcund recognizable rafting mechanism for the dropstones. was deposited near a nearshore, grounded or clasts of the Urkkavaara in the overlying arkoses

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Also early Proterozoic in age are glaciogenic Overlying arkoses and units in the Chibougamau Formation of Quebec conglomerates J J (Long, 1981) and the Padlie Formation of the Hurwitz Group in the Northwest Territories o • west of Hudson Bay (Young and McLennan, DIAMICTITE MEMBER ^¿O . • o 1981). In the United States, the Reany Creek, O o_. Enchantment Lake, and Fern Creek Formations UPPER SILTSTONE- at the base of the Marquette Supergroup in ARGILLITE MEMBER northern Michigan have been interpreted as gla- URKKAVAARA cial deposits by several workers, including Gair GRADED SANDSTONE FORMATION g — (1981) and Ojakangas (1982). In Wyoming, the MEMBER Vagner and Headquarters Formations appear to be glaciogenic (Houston and others, 1981). All LOWER SILTSTONE- of the above cited units contain both diamictites ARGILLITE MEMBER and dropstone-bearing sequences. The Campbell Lake Formation in Wyoming (Houston and others, 1981) contains diamictites but no drop- Underlying arkoses o o o e and conglomerates o o o stone units. In the Black Hills of South Dakota, diamictites are associated with units containing Figure 11. Diagrammatic column illustrating members of the Urkkavaara Formation and lonestones that may or may not be dropstones overlying and underlying sandstones and conglomerates. Interpreted glacial advance and re- (Kurtz, 1981). treat are also shown relative to the members. The North American glaciogenic units cited above are in general poorly dated; each is be- and conglomerates, and so we assume that the and Hagar's (1965) cause and effect model is tween -2,500 m.y. and 1,800 m.y. old, on the erosion occurred prior to the lithification of the like ours for the Sariolian glaciogenic deposits; basis of the ages of Archean basement rocks and Urkkavaara, and that the erosional contact is a the marine incursion is interpreted to be the re- crosscutting igneous rocks. The best-dated are minor diastem rather than a significant uncon- sult of isostatic loading due to glaciation, and the those of the Huronian Supergroup that are cut formity. As the area was deglaciated, isostatic emergence is interpreted to be the result of iso- by the 2,150-m.y.-old Nipissing Diabase; thus, uplift in an amount greater than the accompany- static uplift that followed glacial retreat, with the these units are 2,500 to 2,150 m.y. old, and a ing eustatic sea-level rise caused a marine regres- uplift greater in magnitude than the accompany- whole-rock Rb-Sr date on quartzose graywacke sion. Erosion and deposition from late-stage ing eustatic sea-level rise. and argillite of the Gowganda Formation itself glaciofluvial melt waters of a receding and now (Fairbairn and others, 1969) yielded an age of distant glacier and/or from postglacial fluvial OTHER EARLY PROTEROZOIC 2,288 ± 87 m.y. The stratigraphically lower activity resulted in erosion of the top of the up- GLACIATIONS AND Ramsey Lake and Bruce Formations therefore lifted glacial sequence and deposition of fluvial POSSIBLE CORRELATIONS would be 2,500 to 2,300 m.y. old. It has been sediments (Fig. 11). As sedimentation ceased, assumed by some workers (Young, 1970,1973) weathering produced a thick soil profile upon When this discovery of glaciogenic rocks was that the North American examples are essen- the Sariolian Group. first published in January 1983 (Marmo and tially the products of one major ice age. This ice The Urkkavaara Formation may be bounded Ojakangas, 1983), we knew of no Proterozoic age may have included several glaciations and by unconformities. Similar relationships within diamictites in Europe that had been regarded as perhaps spanned tens of millions of years. Until a Pleistocene glacial-marine sequence in the glacial in origin. Several deposits in Soviet Kare- radiometric dates indicate otherwise, this consti- Puget Lowlands of Washington have been used lia and on the Kola Peninsula had been recog- tutes a practical working model. by Domack (1983) as evidence that the history nized as tilloids associated with lonestone- The question then arises as to whether the of the sequence included erosion related to iso- bearing units, but they were interpreted as glaciogenic rocks of the Baltic and Canadian static changes in sea level. The lack of an upper having originated by tectonosedimentary proc- (Laurentian) Shields were products of the same bounding unconformity would be evidence that esses (Negrutsa and Negrutsa, 1981a, 1981b, glaciation. Those in Finland and adjacent Soviet the sequence had remained below sea level dur- 1981c). Since then, tillites, glaciolacustrine beds Union appear to be 2,500 to 2,300 m.y. old, the ing its deposition. with dropstones, and glaciofluvial deposits have same age range as has been suggested for those This model is similar to a general model pro- been reported in the Sariolian Group in both in the Huronian Supergroup. Sparse paleomag- posed by Boulton and Deynoux (1981, p. 411) North Karelia, Soviet Union (Panajarvi Forma- netic data indicate a paleolatitude for the Huro- for the emergence of a proximal glaciomarine tion), and on the Kola Peninsula, Soviet Union nian Supergroup of 50°N (Morris, 1977) to sediment association. A Pleistocene analogue of (Lower Akhmalakhti Formation), by Salop 62°N (Symons, 1975). Pesonen and Neuvonen this stratigraphic sequence is present in the state (1983, p. 138). (1981) constructed paleolatitude curves for the of Maine (Borns and Hagar, 1965; C. L. Matsch, In the lower Proterozoic of North America, Baltic and Laurentian Shields; they showed the 1983, personal commun.). There, glaciomarine glaciogenic deposits have been known since Baltic Shield (reference point: Kajaani, Finland) sediments deposited during a marine transgres- Coleman (1907, 1908) reported them in the at latitudes of 30°N at 2,100 m.y. ago and 55°N sion are overlain by fluvial outwash sediments Huronian rocks of southern Ontario. Three gla- at 2,500 m.y. ago, and the Laurentian Shield deposited upon the eroded glaciomarine sedi- cial units in the Huronian Supergroup are the (reference point: Winnipeg, Manitoba) at lati- ments during an early postglacial emergence that Ramsey Lake, Bruce, and Gowganda Forma- tudes of 65°N at 2,100 m.y. ago and 35°N at was accompanied by a marine regression. Borns tions, as summarized by Young (1981a, 1981b). 2,500 m.y. ago. The curves coincide at 2,400

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m.y. and a paleolatitude of 50°N. These data ferred low relief of the craton suggest that the laryhman ylaosassa (Early Proterozoic Urkkavaara Formation in Kontiolahti, North Karelia—A glacigenic metasedim ;ntary sequence in suggest that the latitudes of deposition of the glaciation probably was continental in scale. the Upper Sariolan Group): Geologi, v. 35, no. 1, January, p. 3-6. Merilainen, K., 1980, On the stratigraphy of the Karelian for nations, in Silven- glaciogenic deposits discussed herein are similar 7. The time of this early Proterozoic glacia- noinen, A., ed., Jatulian geology in the eastern part of the Baltic Shield: to those of the major glaciations that occurred Proceedings of a Finnish-Soviet Symposium, Finland. 1979. p. 17-112. tion on the Baltic Shield may coincide in time Mikkola, T., 1955, Sedimentary transportation ir Karelian •juartzites: Finland during the Pleistocene, when continental glaciers with the early Proterozoic ice age on the Cana- Commission of Geology Bulletin 168, p. 27-29. Mode, W. N., Nelson, A. R., and Brigham, J. It., 1983, \ facies model of reached as far south as 39°N in North America dian Shield. Quaternary glacial-marine cyclic sedimentation aloni; eastern Baffin Is- and 50°N in Europe. These data, however im- land, Canada, in Molnia, B. F., ed.. Glacial-marine sedimentation: New York and London, Plenum Press, p. 495-533. precise, also are consistent with a model in ACKNOWLEDGMENTS Morris, W. A., 1977, Paleomagnetism of the Gowganda and Chibougamau Formations; evidence for 2200 Ma-old folding and remagnetization which both shields were glaciated at about the event of the Southern Province: Geology, v. 5, p. 13''-140. same time. Paleomagnetic data are not yet suffi- Negrutsa, T. F., and Negrutsa, V. Z., 1981a, Early Proterozo c Lammos tilloids This work was supported by the Geological of the Kola Peninsula, U.S.S.R.; in Ha/nbrey, M. J., and Harland, cient to determine the relative positions of the Survey of Finland. C. L. Matsch reviev/ed an W. B., eds., Earth's Pre-Pleistocene glacial record: Cambridge, England, Cambridge University Press, p. 678-680. two shields in early Proterozoic time. early version of the manuscript and contributed 1981b, Early Proterozoic Yanis-Yarvi tilloids, south Karelia, U.S.S.R., in Hambrey, M. J., and Harland, W. B., eds., Earth's Pre-Pleistocene several fruitful discussions. Anna Siedlecka also glacial record: Cambridge, England, Cambridge University Press, SUMMARY AND CONCLUSIONS p. 681-682. reviewed an early version. The final submitted 1981c, Early Proterozoic Sarioli tilloids in the eastern part of the Baltic manuscript was given thorough reviews by J. C. Shield, U.S.S.R., in Hambrey, M. J., and Harland, W. B„ eds.. Earth's Pre-Pleistocene glacial record: Cambridge England, Cambridge Uni- 1. Glaciogenic deposits of early Proterozoic Crowell and J. H. Stewart. We wish to thank all versity Press, p. 683-686. age, about 2,500 to 2,300 m.y. old, have been Nesbitt, H. W., and Young, G. M., 1982, Early Proterozoic climates and plate of these persons for their most valuable con- motions inferred from major element chemistry of lutites: Nature, identified in one small area in eastern Finland. structive criticisms and insights. v. 299, p. 715-717. Ojakangas, R. W., 1965, Petrography and sedimentation cf the Precambrian They constitute the 30- to 60-m-thick Urkka- Jatulian quartzites of Finland: Finland Co mmission c f Geology Bulletin REFERENCES CITED vaara Formation of the Sariolian Group of the 214, 74 p. 1982, Lower Proterozoic glaciogenic formations Marquette Super- Andrews. J. T., and Matsch, C. L., 1983, Glacial marine sedimertation: An group, Upper Peninsula, Michigan, U.S. A [abs.]: Inti mational Associa- Karelian Supergroup. annotated bibliography: Norwich, England, Geo Abstracts, Limited, tion of Sedimentologists, International tongress cn Sedimentology, 227 p. 2. The best evidence for a glaciogenic origin 11th, Hamilton, Ontario, McMaster University, Alstracts of Papers, Borns, H. W., Jr., and Hagar, D. J., 1965, Late-glacial stratigraphy of a northern p. 76. part of the Kennebec River Valley, western Maine: Geological Society is the presence of dropstones in thinly laminated Ovenshine, A. 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The transi- 1908, A lower Huronian Ice Age: Journal of Geoiojjy, v. 16, Shield—Implications for Precambrian tectonics, in Kroner, A., ed., Pre- p. 149-158. tion from a laminated dropstone-bearing unit cambrian plate tectonics: Amsterdam, Elsevier Scientific Publishing Domack, E. W., 1983, Fades of late Pleistocene glacial-marine sediments on Company, p. 623-648. Whidbey Island, Washington: An isostatic glacial-marine sequence, in to a diamictite suggests that the diamictite was Piirainen, T., Honkamo, M., and Rossi, S., 1974, A preliminary report on the Molnia, B. F., ed., Glacial-marine sedimentation: New York and Lon- geology of the Koli area: Geological Socioty of Finh.nd Bulletin, v. 46, formed farther seaward from the grounded or don, Plenum Press, p. 535-570. p. 161-166. Eskola, P. E., 1919, Hufvuddragen av Onega-Karelens geologi: Hehiingin geol. floating glacier in a zone of rapid melting of yhd. tiedonantoja 1917 u. 1918, p. 13-18, and Teknikern, 1919, Powell, R. 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J., 1969, Correla- tion of radiometric age of Nipissing diabase and metasediinents with Sakko, Matti, 1971, Varhais-Karjalaisten metidia Gaasen vadiometrisia: the Kola Peninsula (Negrutsa and Negrutsa, Proterozoic orogenic events in Ontario: Canadian Journal of Earth Zirkoni-ikia (with an English summary: Radiometric zircon ages on the 1981a, 1981b, 1981c) prove to be glaciogenic Sciences, v. 6, p. 489-497. Early Karelian metadiabases): Geologi, (Finnish Geological Society), Gaal, G., 1964, Jatul und karelische Molasse im S-Koligebiet in Nordkarelien v. 23, p. 117-118. units with dropstones, then the glaciogenic de- und ihre Beziehungen zum Gebingsbau des prakambrischen Orogens: Salop, L. J., 1983, Geological evolution of the Eirth during the Precambrian: Finland Commission of Geology Bulletin 213, 45 p. 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B., eds., Earth's Pre- ganda Formation, Ontario: Geology, v. 3, p. 303-306. Pleistocene glacial record: Cambridge, England, Cambridge University further support a glaciomarine rather than a gla- Vfiyrynen, H., 1954, Suomen Kalliopera, Sen Synty ja Gnologinen Kehitys: Press, p. 803-806. Helsinki, Otava, 260 p. ciolacustrine environment. Goldstein, R. H., 1983, Stratigraphy and sedimentology of ice-rafted and turbi- Young, G. M., 1970, An extensive early Proterozoic glaciation in North Amer- dite sediment, Canada Basin, Arctic Ocean, in Molnia, B. F., ed., ica?: Palaeogeography, Palaeoclimatology, Pala »ecology, v. 7, 4. The dominant source of detritus in the Glacial-marine sedimentation: New York and London, Pleium Press, p. 85-101. p. 367-400. Urkkavaara Formation was Presvecokarelidic 1973, Tiliites and aluminous quartzites ¡is possible time markers for Hambrey, M. J., and Harland, W. B., 1981, eds., Earth's Pre-Pleistocene glacial middle Precambrian (Aphebian) rocks of North America, in Young, record: Cambridge, England, Cambridge University Press, 1,004 p. granitic gneisses. Some sediment may have been G. M., ed., Huronian stratigraphy and sedimen ation: Geological Houston, R. S , Lanthier, L. R., Karlstrom, K. K., and Sylvester, G., 1981, Early Association of Canada Special Paper 12, p. 97-128. derived from underlying portions of the Sario- Proterozoic diamictite of southern Wyoming, in Hambrey, M. J., and 1981a, The early Proterozoic Gowganda Formation. Ontario, Canada, Harland, W. B., eds.. Earth's Pre-Pleistocene glacial record: Cambridge, lian Group, including albite diabases (green- England, Cambridge University Press, p. 795-799. in Hambrey, M. J., and Harland, W. B., eds., Earth's Pre-Pleistocene stones). Kurtz, D. D., 1981, Early Proterozoic diamictites of the Black Hills, South glacial record: Cambridge, England, Cambridge University Press, Dakota, in Hambrey, M. J., and Harland, W. B., eds.. Earth's Pre- p. 807-812. 5. The craton probably had a low relief and Pieistocene glacial record: Cambridge, England, Cambridge University 1981b, Diamictites of the early Proterozoic Ramsay Lake and Bruce Press, p. 800-802. Formations, north shore of Lake Huron, Ontario, Ca lada, in Hambrey, M. J., and Harland, W. B., eds., Earth's Pre-Pleistoc:ne glacial record: was moderately to deeply weathered, as indi- Long, D.G.F., 1981, Glaciogenic rocks in the early Proterozoic Chibougamau Cambridge, England, Cambridge University Press, p. 813-816. cated by the moderate mineralogical maturity of Formation of northern Quebec, in Hambrey, M. J., and Harhind, W. B., eds., Earth's Pre-Pleistocene glacial record: Cambridge, England, Cam- Young, G. M., and McLennan, S. M., 1981, Early ProterozDic Padlei Forma- the Sariolian sediment and the high mineralogi- bridge University Press, p. 817-820. tion, Northwest Territories, Canada, in Hambrey, fr. J., and Harland, Marmo, J. S., 1981, The Hokkalampi Kyanite occurrence in Kontolahti: On W. B., eds.. Earth's Pre-Pleistocene glacial record: Cambridge, England, cal maturity of the overlying Jatulian sediment. geology of the area and the origin of aluminium in the occurience [M.S. Cambridge University Press, p. 790-794. 6. The possible broad distribution of glacio- thesis]: Helsinki, Finland, University of Helsinki, 81 p. MANUSCRIPT RECEIVED BY THE SOCIETY JULY 7,1!>83 Marmo, J. S., and Ojakangas, R. W., 1983, Varhaisproterotsooinen Urkkavaara- REVISED MANUSCRIPT RECEIVED JANUARY 24, IS84 genic deposits on the Baltic Shield and the in- muodostuma Kontiolahdella glasigeeninen metasediment-tisaija Sario- MANUSCRIPT ACCEPTED FEBRUARY 1,1984

1 »tinted in U.S.A.

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