Glacial morphology and dynamics with till geochemical explorGLACationIAL MORP in HOLtheOGY ribbed AND DY moraineNAMICS WITH are TILLa of GEOCHEMICAL Peräpohjola, EXPLORATION IN THE RIBBED MORAINE AREA OF PERÄPOHJOLA, FINNISH FinnishLAPL LaANDpland

by

Pertti Sarala

ACADEMIC DISSERTATION

To be presented with the permission of the Faculty of Science of the University of Oulu, for public criticism in the Auditorium GO 101, Linnanmaa, on 14th October, 2005, at 12 o’clock noon Supervised by

Prof.Emeritus Risto Aario Department of Geosciences University of Oulu,

Prof.Vesa Peuraniemi Department of Geosciences University of Oulu, Finland

Reviewed by

Dr.Keijo Nenonen Geological Survey of Finland Espoo, Finland

Prof.Emeritus Raimo Kujansuu Ikaalinen, Finland

Cover: Gravelly till with sandy layers in test pit M64 in the Sihtuuna village,Tervola. Photo by Pertti Sarala Back: Sihtuuna moraine ridges in the Sihtuuna village,Tervola. Glacial flow has been from the west (left to right in photograph). Photo by Risto Aario Pertti Sarala, 2005. Glacial morphology and dynamics with till geochemical exploration in the ribbed moraine area of Peräpohjola, Finnish . Geological Survey of Finland, Espoo. 17 pages with 6 original papers.

An aerial-photo and elevation model interpretation with detailed field surveys were used to study glacial morphology and stratigraphy in the Peräpohjola area, in southern Finnish Lapland. Test pit surveys with earlier and present till sampling were carried out in the seven test sites for investigating the glacial dispersal of elements and mineralized material in till.The results were presented in six papers dealing with the geochemical prospecting for Au,ribbed moraine formation and the glacial stratigraphy in the study area. The till stratigraphy of the Peräpohjola area consists of three till beds, of which the oldest is an age of Saalian glaciation and the others of an age of the Weichselian glaciation. The glacial morphology depicts only two Weichselian glacial phases demonstrated by an assemblage of active-ice morainic landforms including ribbed moraines, drumlins and flutings. These forms are dominating landform types in the area of Kuusamo ice lobe. The interlobate area with the north-northwest to south-southeast oriented drumlin field, instead, is a relic of the older glacial phase and has preserved under cold-based, central area of the last glaciation. The glacial phase, when the old drumlin field was formed was the first one to cover the area during the Weichselian glaciation, probably at the beginning of the Middle Weichselian. The characteristics of ribbed moraines were studied carefully to found out the composition, structure and stratigraphy of the ridges, and also to estimate glacial dispersal of till and surficial boulders. Ribbed moraines in the Peräpohjola area consist of three subtypes: hummocky ribbed moraines, Rogen moraines and minor ribbed moraines. The Sihtuuna moraine, a new morainic landform type, is introduced as a result of present study and can be classified as a minor ribbed moraine. The formation of ribbed moraines is re-examined and a new hypothesis has been presented. The formation of the ridges was a two-step process where at the first stage fractured ice-sediment blocks were moved under ice sheet to form rib-like morphology. At the second stage, the sediments and the bedrock surface in the areas between the ribs were intensively quarried due to freeze-thaw process to become re-deposited to the next ridges. Thus, the transport distance of local bedrock fragments in the uppermost part of the ribbed moraine ridges is only a few tens or hundreds of metres. The most suitable conditions for ribbed moraine formation existed during the Late Weichselian deglaciation, after the Younger Dryas, when the climate warmed very quickly leading to an imbalance between warm glacier’s surface and cold bottom. The characteristics of ribbed moraines have been utilized in prospecting for Au and its pathfinder elements in the test areas. The short glacial transportation of mineralized material has become emphasised in many areas, especially in the Petäjävaara area, where Au-Cu-bearing, hydrothermally altered contact zone between diabase and quartzite in the bedrock was found. Also in other test sites, where ribbed moraine ridges occurred, the promising source areas were pointed out, although needing for future studies. The observations in the study area proved that the study of glacial flow directions and transport distances of till with distinguishing moraine formations and their genetic background is essential to succeed in ore prospecting.

Key words (GeoRef Thesaurus, AGI): glacial geology, ribbed moraine, till, geochemistry, ore prospecting, stratigraphy,subglacial environment, glaciation, deglaciation, Weichselian, Quaternary, Peräpohjola, Finland

Pertti Sarala Geological Survey of Finland, P. O. Box 77, FI-96101 , FINLAND E-mail: pertti.sarala@gtk.fi

ISBN 951-690-934-5

Vammalan Kirjapaino Oy 2005 4Pertti Sarala

Preface

The doctoral thesis comprises the following papers:

I Aario, R., Peuraniemi, V. & Sarala, P. 1997. The Sihtuuna moraine at Tervola, southern Lapland. Sedimentary Geology 111, 135–145.

II Sarala, P. , Peuraniemi, V. & Aario, R. 1998. Glacial geology and till geochemistry in ore exploration studies in the Tervola area, southern Finnish Lapland. Bulletin of the Geological Society of Finland 70, 19–41.

III Sarala, P. & Rossi, S. 2000. The application of till geochemistry in exploration in the Rogen moraine area at Petäjävaara, northern Finland. Journal of Geochemical Exploration 68, 87–104.

IV Sarala, P. 2005. Till geochemistry in the ribbed moraine area of Peräpohjola, Finland. Applied Geochemistry 20, 1714–1736.

V Sarala, P. 2005. Ribbed moraine stratigraphy and formation in southern Finnish Lapland. Journal of Quaternary Science. (submitted)

VI Sarala, P. 2005. Weichselian stratigraphy, geomorphology and glacial dynamics in southern Finnish Lapland. Bulletin of the Geological Society of Finland 77, Part 2, xxx–yyy. (accepted) Geological Survey of Finland 5 Introduction

This doctoral thesis summarizes data collected dur- interlobate areas, which were not able to erode or ing the exploration studies in 1990’s in the Rovanie- deform underlying bedrock and sediments (cf. Kle- mi-Tervola area, southern Finnish Lapland. The area man, 1994; Kleman and Borgström, 1996, Punka- was glaciated several times during the Quaternary pe- ri, 1997). The interpretation of those subglacial envi- riod and was affected by glacial erosion frequently. ronments and moraine formations can be used to re- Due to glacial deposition processes, eroded materi- construct glacial cycles and dynamics of former gla- al is covering bedrock as a till sheet composed of dif- ciations (e.g. Kleman et al., 1997; Clark et al., 2000; ferent moraine formations. The till and moraine for- Jansson, 2002; Paper VI). mations act as a medium reflecting glacial conditions In the present study, attention was paid to the char- and dynamics during the glacial erosion, transporta- acteristics of special glacial morphology called ribbed tion and deposition. By examining all of the features moraine. It is a group of moraine ridges perpendicu- together the transportation of mineralized material in lar to the last glacial flow direction in the central are- till can be estimated. as of the former glaciations in Northern Hemisphere. The bedrock of the studyareaismainly com- The term Rogen moraine has been commonly used as posed of an association of sedimentary and volcan- a synonym for these forms in Finland. In Fennoscan- ic rocks of the Peräpohja Schist Belt (Perttunen and dia ribbed moraines are common particularly in the Hanski, 2003). The rocks have proven to be potential central or northern areas of Finland and Sweden and for ore prospecting, because of many observed Au- also in Norway, in interior part of the Late Weichse- Cu- and Fe-mineralization (Eilu, 1999 and the ref- lian glaciation (cf. Hättestrand and Kleman, 1999). erences within) and of numerous mineralized boul- A lot of studies concerning their existence, composi- der observations (Papers II, III, IV and V). High met- tion, structure and formation hypothesis were pub- al anomalies in till are also a sign of the existence of lished during their hundred-year study history (Pa- mineralized sources in the bedrock. Those observa- pers III, IV and V). Especially the works of Lundqvist tions were done mostly during the earlier prospect- (1969, 1989, 1997) and Aario (1977, 1990), where ing studies but also in the course of the present field they depicted the formation processes of those mo- works. However, the Quaternary geology of the area raine ridges relating to special subglacial conditions, was poorly known before the present study and that can be mentioned. is why the results to clear out the bedrock sources for In the latest hypothesis presented by Hättestrand the mineralized material in till were minor. (1997), many of those earlier theories were conclud- The glacial morphology of northern Finland is a ed. Hättestrand presented on the basis of literature composition of moraine and glaciofluvial formations and mappings in Sweden that the formation of ribbed of active and passive glaciers. Several works (e.g. Ku- moraines was occurred at the retreating boundary be- jansuu, 1967; Glückert, 1974; Aario 1977, 1990; Ku- tween frozen- and thawed-bed conditions under ex- rimo, 1974, 1977; Aario and Forsström, 1979; Ham- tensional, moving ice sheet, which caused the frac- borg, 1986; Sutinen, 1992; Johansson et al., 2000; turing of pre-existing till sheet. He also presented a Johansson and Kujansuu, 2005) were done to classi- classification for ribbed moraines including four sub- fy the formation types and their existence in the area. types: Rogen moraine, hummocky ribbed moraine, The active-ice formations composed of an assemblage minor ribbed moraine and Blattnick moraine. This of hummocky moraines, ribbed moraines, drumlins classification is also used in present study (Papers IV and flutings (e.g. Lundqvist, 1969; Aario, 1977; Pa- and V) and is proposed to use in Finland in future (cf. per II), were formed under the ice lobes. In places, be- Sarala, 2003). tween the active ice lobes existed passive, cold-based The deposition processes of moraine formations 6Pertti Sarala and till within were studied in seven test sites on the stage was occurre dinFennoscandia (e.g.Nenonen study area for estimating transport distances of min- and Eriksson, 2004; Saarnisto and Lunkka, 2004; eralized boulders and debris (Papers I, II, III, IV). Be- Svenden et al., 2004). Same type of age estimations cause the ribbed moraine morphology was dominant has been presented also from northern Finland (e.g. in the area, the characteristics of their formation proc- Mäkinen, 1999; Helmens et al., 2001), leading to a esses were essential to study for succeed in prospect- re-examination of the timing of the Weichselian gla- ing. The use of ribbed moraines in ore prospecting is ciation (Paper VI). only a little investigated earlier and only a few surveys The aims of this thesis, in the first place, were to have been published (Peuraniemi, 1982; Aario, 1990; study glacial morphology and till stratigraphy in the Aario and Peuraniemi, 1992). In those studies, the Peräpohjola area with an estimation of transport dis- uppermost part of the ridges was proven to be indic- tances of mineralized material in till at seven test sites. ative of local bedrock composition and also the exist- Special attention was paid on occurrence, structural ence of surficial mineralized occurrences in the bed- features and the till geochemistry of ribbed moraines. rock. Short transport distances came out as the anom- On the basis of observations the formation hypoth- alous metal contents of fine fraction of till on the dis- esis of ridges was re-examined. In the second place, tal side of mineralized occurrences in bedrock. Also, the development of glacial morphology and stratig- local rock fragments and boulders in the surficial part raphy was used to reconstruct glacial dynamics of the of ridges were indicative of short glacial dispersal. An glaciers in the study area during the Weichselian gla- average transport distance of surface boulders was the ciation. Furthermore, the observations made during shortest in the case of ribbed moraines when compar- present study were used as a reference for the exami- ing different moraine formations (cf. Salonen, 1986; nation of regional glacial morphology and dynamics Bouchard and Salonen, 1989). in southern Finnish Lapland. As a comparison of the The development of glacial morphology and results with literature and present knowledge of dat- stratigraphyduringthe Weichselianglaciationhas ing, the glacial evolution of the Weichselian glacial been along studied and debated i nFinland. The phases was modelled. works of Kujansuu (1967), Korpela (1969), Aario and Forsström (1979) and Hirvas (1991) have been bases for the construction of general till stratigra- Presentation of papers phy with glacial flow patterns in northern Finland. A chronology of different glacial phases has been based Paper I: Aario, R., Peuraniemi, V. & Sarala, P. 1997. on the correlation of microfossil contents and radio- The Sihtuuna moraine at Tervola, southern Lapland. carbon ages of organic intermediate layers. An inter- Sedimentary Geology 111, 135–145. pretation of the results has lead to the thought that all In this paper we review a new moraine type, Sih- interstadial phases were dated to the Early Weichse- tuuna moraine found northwest of the village of Ter- lian period. Because the determination limit for radio- vola, southern Finnish Lapland. The area of this mo- carbon ages is about 40–50 ka, the reliability of age raine type covers about 10 km2 . Sihtuuna moraines estimations is debatable. Since the implementation are formed of ridges perpendicular to the latest west- of thermoluminescense (TL) and optically stimulated east oriented glacial flow. Ridges are quite small in luminescence (OSL) methods in dating the variation scale; commonly several hundreds of meters long, of ages has been increased and many determinations some tens of metres wide and from three to five me- have given much younger ages than the Early Weich- tres high. They are formed of two till beds with strati- selian. Forexample, lately studies in the northwest fied sands and gravels in between. The surface of ridg- Russia have pointed out that after the Middle Weich- es is covered with large and angular boulders trans- selian glaciation, quite warm and almost ice-free ported only a very short distance. Geological Survey of Finland 7

As a conclusion, we presented that the origin of is why the material released from the ice has mainly the Sihtuuna moraine was a two-step process. Initial- deposited as waterlain till or washed sediments above ly plenty of streaming water together with subglacial the pre-existing till sheet. mass-flowage existed. The second stage was related to The test sites of Petäjävaara and Vammavaara were bouldery surface of the ridges and represents strong two of the most interesting and detailed studied ar- quarrying activity of the glacier during the forma- eas during the present investigation in the Tervo- tion process. la area. Many Au-Cu mineralized boulders of which Till geochemistry proves that till in the upper part source(s) was unknown were found at the surface of of ridges is consisted of high contents of Au,Cu, the moraine ridges in the sites. The ridges perpendic- Ni and Co particularly in afine fraction of till (< ular to the latest glacial flow direction were formed of 0.06 mm). Especially the distribution of Au is high- two till units in Petäjävaara and of three till units in ly anomalous in the fine fraction but also in a heavy Vammavaara. Geochemistry of different till fractions mineral concentrate of till in many test pits. Because (< 0.06, 0.06–0.5 and > 2 mm) and heavy mineral the high Au contents occur in the uppermost till unit, concentrate with boulder observations reflected short characteristically depicting shortglacial transporta- glacial dispersal of elements in ribbed moraine ridges. tion and local phenomenon in bedrock, the possibil- Particularly, the uppermost till unit is useful in trac- ity for an occurrence of Au mineralization(s) in the ing potential sources in the bedrock. bedrock is great. Clear indicationoflocal bedrock The study of glacial flowdirections, till struc- composition in the surficial part of ridges is also the tures and stratigraphy of moraine formations with till feature that makes ore prospecting quite easy in the geochemistry proved to be a powerful means in locat- Sihtuuna area. ing source rock of glacially transported, mineralized boulders and metal anomalies in till in the area. For Paper II: Sarala, P. , Peuraniemi, V. & Aario, R. 1998. prospecting Au, the most useful indicator elements Glacial geology and till geochemistry in ore explo- in till geochemistry were among Au itself Cu, Te and ration studies in the Tervola area, southern Finnish Co. As a result of the study, Cu-Au mineralization Lapland. Bulletin of the Geological Society of Fin- was found at the Petäjävaara site. land 70, 19–41. The general glacial morphology of northern part Paper III: Sarala, P. & Rossi, S. 2000. The application of the study area and the detailed exploration surveys of till geochemistry in exploration in the Rogen mo- in the test sites of Petäjävaara and Vammavaara was raine area at Petäjävaara, northern Finland. Journal of presented in this paper. Furthermore, some charac- Geochemical Exploration 68, 87–104. teristics of ribbed moraines for ore exploration were Detailed studies for prospecting Au and Cu were pointed out. done in the Petäjävaara test site. The studies were The glacial morphology is mainly composed of concentrated on tracing the transportdistance of the landforms deposited subglacially under the active rock fragments in till and defining structural and ge- ice sheet. An assemblage of active-ice landforms like ochemical features of ribbed moraines. The methods ribbed moraines and drumlins is dominant. Ground used were the test pit surveys with till sampling, geo- moraine areas having no indication of glacial flow physical ground surveys and bedrock mapping with direction are also common in lowland areas, in the deep drillings. For examining the distribution of Au Kemijoki basin. Instead, only two esker chains as a and its pathfinder elements earlier percussion drilling mark of glacial meltwater streams are found, but no samples were also used. marginal formations. The later is due to glacier end- Glacial morphology is composed of Rogen mo- ing to the proglacial Ancylus Lake, the pre-existing raine-like ridges in the main study area. Cover mo- phase of the Baltic Seaduring the deglaciation. That raine with quite thin till sheet is common in northern 8Pertti Sarala parts. In the east, the slope of Petäjävaara hill is cov- the bedrock, high metal contents can be traced in a ered with shore deposits of Ancylus Lake. wide area by taking samples from the uppermost till The study shows that the uppermost unit of the unit but also from the lower, commonly distantly de- two existing till units is indicative of local bedrock rived till units. composition. Glacial dispersal of Au and other met- The use of lightweight percussion drill was esti- als like for example Cu, Co and Te, the best pathfind- mated in the test sites of Petäjävaara, Vammavaara er elements, are short due to strong quarrying during and Kivimaa. The examination was done both in hor- the deposition of ribbed moraine ridges. Particularly, izontal and vertical dimensions. In Petäjävaara and Au contents are high on a distal side of mineralized Vammavaara, main study areas were composed of zone in the bedrock, but steeply decreasing to the gla- ribbed moraines and in Kivimaa of cover moraine. cial flow direction. High Au contents exist in every In the case of ribbed moraine ridges the penetration till size fraction (< 0.06, 0.06–0.5 and > 2 mm), but of percussion drill was low due to the surface and the the coarsest fractions have the clearest indication of uppermost till unit rich of boulders. In Kivimaa and close vicinity of the mineralized bedrock. This is also Vammavaara the stony, brecciated weathered bedrock seen in fresh pyrite and chalcopyrite grains in heavy at the bottommost or intermediate layer in till stratig- mineral concentrate. These minerals aretypical for raphy was also the limit for percussion drilling. hydrothermally altered Au-Cu mineralizations in the All of the cases clearly prove that till composition Peräpohja Schist Belt. and stratigraphy with the deposition processes of dif- In this paper we have also presented Au-Cu min- ferent moraine formations must be known before ex- eralized zone with quartz veins in the contact of dia- amining the distribution of metals and their path- base and quartzite in the bedrock as a result of present finder elements. These things should be also noticed exploration studies. As a conclusion we have stated when interpreting the results of different sampling that in the Petäjävaara area several Au-Cu mineralized scales (e.g. regional, local and prospect scales). An in- zones must be existed in the bedrock because of the terpretation of glacial morphology together with test high Au and Cu concentrations in till also on eastern pit surveys are in this context a key to choose best side of the localized mineralization. equipment for sampling, to estimate sampling effec- tiveness and also to compare the results between dif- Paper IV:Sarala, P. 2005. Till geochemistryinthe ferent formation types. ribbed moraine area of Peräpohjola, Finland. Applied Geochemistry 20, 1714–1736. Paper V: Sarala, P. 2005. Ribbed moraine stratigraphy Ribbed moraines havemany features that make and formation in southern Finnish Lapland. Journal prospecting for Au and other metals easy. The best of Quaternary Science. (submitted) featureistheir good indication of local bedrock In this paper, the formation process of ribbed mo- composition in the uppermost part of ridges, which raine ridges was re-examined. The observations made comes out as high metal contents in everytill size from the study area proved that the formation proc- fractions (< 0.06, 0.06–0.5 and > 2 mm), in heavy ess was two-step. During the early stage of deglacia- mineral concentrate and in the composition of sur- tion, on the retreating zone of subglacial frozen- and face boulders on the distal side of mineralization in thawed-bed, pre-existing sediments and the bottom- the bedrock. Glacial dispersal for the elements is very most part of the ice sheet formed a stagnant, stacked sharp in a close vicinity to the mineralization with mass. Duetopressureand tension caused by the small outcrop, which is at the same time the bene- moving ice sheet, featherlike cracks were formed and fit because the source(s) is easy to find out but also the stagnant mass was fractured. When the zero-de- the restriction due to need of dense grid during sam- gree boundary was crossed the surface of bedrock or pling. In the case of large mineralized occurrence in other weakness zone (e.g. till unit boundary, strati- Geological Survey of Finland 9

fied layer, boulder pavement), fractured blocks were of two separate glacial advance of the Weichselian age moved along the ice sheet forming rib-like morphol- in southern Finnish Lapland. The first one depict- ogy.Because of the prevailing cold conditions, fol- ed as drumlin field, was deposited during the glacial lowed freeze-thaw process was caused the quarrying flowtowards the south-southeast and was dated to in between the newborn ribs and a bit later, after the the Early or the Middle Weichselian glaciation. The pressure increased on the proximal contact, the dep- second advance, when the ribbed moraine-drumlin- osition of material (released from the ice bottom) on flutings association deposited, existed during the gla- the surface of the ribs. cial flow mainly from the west to the east at the end of Quick and strong decrease of the air temperature the Late Weichselian glaciation. As a result, two mod- and the subsequent imbalance between the surface els of stadial-interstadial cycles of the Weichselian gla- and the basis of the ice sheet might be the most suit- ciation in southern Finnish Lapland were presented. able moment for the beginning of ribbed moraine formation at the end of Younger Dryas, on the early Ribbed moraine formation stage of deglaciation. The climate change during that time has been aglobal phenomenon and thus, ex- The composition and structure of ribbed moraines in plains the occurrence of ribbed moraines in the cen- the study area led to a re-examination for the forma- tral areas of the former glaciated areas. tion processes of the ridges. Short transportation of till and rock fragments in the surface of ridges and in Paper VI: Sarala, P. 2005. Weichselian stratigraphy, surficial boulders (on Papers I, II, III, IV and V), were geomorphology and glacial dynamics in southern the features of which deposition process is explained Finnish Lapland. Bulletin of the Geological Society in anew way.Based on the observ ations, two-step of Finland 77, Part 2, xxx–yyy. ( accepted) formation of ribbed moraines was presented (Fig. 1). A detailed description of the glacial morphology, At the first phase, under cold-based conditions dur- till composition and stratigraphy in each of the seven ing the early deglaciation stage, subglacial sediments test sites with earlier published observations was used together with the base of ice sheet formed a stagnant to compile the glacial stratigraphy in the study area. mass, while the upper part of the glacier moved. Due It includes four to fiveseparate till units reflecting to movement, pressureand tension elevated at the three different till beds deposited during the different base of the ice sheet causing featherlike fracturing of glacial advances. The whole sequence is proposed to stagnant mass. By this way, the blocks/fragments of call as the Peräpohja Group. The lowest, Saarenkylä subglacial sediment and ice formed. Contemporary, Till is an age of the Saalian glaciation and other two, an elevation of zero-degree boundary, i.e. the pres- the Kemijoki Till and the Tervola Till, are an age of sure-melting isotherm (cf. Hättestrand, 1997) from the Weichselian glaciation. The uppermost till bed the bedrock to a boundary between the bedrock sur- particularly in ribbed moraine ridges are composed face and the sediments, or within the sediments, to- of two till units named as till members of the Vam- gether with moving glacier intensified the block tran- mavaara Till and Korttelivaara Till representing both portation and finally,the forming of rib morphology. advancing and melting phases of the single glaciation At the second phase, after the tension was relaxed period. Between them is situated the Petäjävaara Till due to collapse of the featherlike cracks and the move- Member formed on early stage of deglaciation, dur- ment of ice-sediment blocks, the freeze-thaw process ing the ribbed moraine formation in the contact zone begun at the base of the moving glacier. This led to of cold- and thawed-bed glacier. a quarrying activity in the areas between the ridges Based on the glacial morphology, stratigraphy and and the deposition of quarried material on the sur- the present knowledge of dating the comparison with face of newborn ribs. As movement of the ice sheet literature have been done. The evidences indicate only continued, bedrock surface was also quarried and the 10 Pertti Sarala

Fig. 1. Atwo-step model of ribbed moraine formation in the boundarybetween the frozen and thawed bed glacier.After the development of featherlike cracks and movem ent of ice-substrate blocks under ten- sional glacial flow, the followedquarrying and redeposition due to freeze-thaw process under prevailing frozen conditions havecaused the formation of rip-like morphology and the deposition of localized, short- transported till material and boulders on the surficial partofribbed moraine ridges. From Paper V. Geological Survey of Finland 11 boulders with good indication of local bedrock were deposited on the surface of ribbed moraine ridges. When the glacier’s movement stopped, the passive ice sheet just melted away leaving the morphology as it was, but when the movement continued and the subglacial condition changed to thawed-bed, drum- linized and fluted morphology formed superimpos- ing the ridges. Even if the bouldery surface is a characteristic fea- ture for ribbed moraines in Finland, it can be missed in places.Ifpre-existingtill and sediment sheetis thick enough, the quarrying process do not reach the bedrock surface. In those cases, the benefit of short glacial dispersal of the upper till in ribbed moraines is also lost in ore prospecting. In this thesis, the beginning of the ribbed moraine formation is presented to be a consequence of rapid climatic change during the last deglaciation. The in- crease of mean temperature of about 10°C over a few Fig. 2. Generalized model of the distribution of Au in till in hundred years at the end of Younger Dryas (about the ribbed moraine ridges, wheretwo till units arepresent 11.8–11.5 ka ago) could have been caused the tem- and: a) one Au-rich vein; or,b) larger Au-rich shear zone perature (and followed mass) imbalance between the with several veins. (cf.Paper III) glaciers bottom and top. Followed increase of melt- ing at the glacier’s margin and surface together with the separation of margin to fast flowing ice lobes and interlobate areas was the major effect causing the in- underlying bedrock. Shortglacial transportdis- crease of tension and finally,the fragmentation of tance of the till is seen in a sharp and anomalous cold-based glacier’s bottom. dispersal of Au and its pathfinder elements in both horizontaland vertical dimensions. Boulders on Ribbed moraines in ore prospecting the surface and in the upper till represent the lo- cal, quarrying activity of the ice during the forma- Ribbed moraines have many features that are useful tion of ribbed moraines (Fig. 2). in ore prospecting. The examples of prospecting for 3. Different till sizefractions indicate shortglacial Au and its pathfinder elements in Peräpohjola em- dispersal. Quarrying activity during the formation phasize the phenomenon: of ridges lift fresh mineralized material from the 1. Ribbed moraines are common morainic landform bedrock surface to the surficial parts of the ridges. type on the large areas in northern and western Thus, ore indicators – mineralized boulders, heavy Finland. An identification of this moraine type or other ore minerals and metal-rich till size frac- is easy if aerial photo interpretation or elevation tions (< 0.06, 0.06–0.5 and > 2 mm) are useful in- models with high resolution are used. Prospecting dicators of the mineralized bedrock. strategy and sampling methods can be the same 4. Till sampling in the ribbed moraine areas can be even if the ribbed moraine subtypes change. easy,fast and cost-effective, because the samples 2. The features of the upper till unit and the surficial can be taken only from the upper till unit. How- boulders indicate strongly the variation of local, ever, in the Peräpohjola area, it is important to dis- 12 Pertti Sarala

tinguish the till from the shore deposits to succeed be correlated with Till Bed IV after the nomencla- in sampling. ture of Hirvas (1991) (Table 2). Above that exists the Local bedrock indication of the surface boulders Saarenkylä Gytja, which has deposited during the can also be usable in other purposes than ore pros- Eemian Interglacial (Sutinen 1992) and maybe also pecting.Especially in theareas,whereglacial drift during the Early Weichselian Interstadial. The sec- sheet is uniform and the bedrock outcrops are minor ond, Kemijoki Till unit is known as dark till in litera- surface boulders can be used for bedrock mapping. ture and is correlative with Till Bed III. It has deposit- ed during the first Weichselian glaciation that covered Glacial morphology and stratigra- the southern Finnish Lapland area. The Sihtuuna phy as an indicator for the timing of Sands follows it in stratigraphy and represents the ice- Weichselian glacial phases free Interstadial stage of the Middle Weichselian. The Tervola Till Formation including members of Vam- The Quaternary lithostratigraphy of southern Finn- mavaara Till, Petäjävaara Till and Korttelivaara Till ish Lapland is composed of three till beds and two represents the Late Weichselian glaciation including inter-till, stratified minerogenic sediment layers con- the till units from advancing phase to melting phase taining sometimes organic material, and is proposed with the redeposited unit related to ribbed moraine to call as the Peräpohja Group. The descriptions, for- formation in between. The Korttelivaara Till is rare mal names and type sections of the units are also pre- and has seldom preserved, because the upper parts sented (Table 1). of morainic landforms were washed during the later The bottommost till unit, Saarenkylä Till, is in- Ancylus Lake and Litorina Sea stages and changed to terpreted to be an age of Saalian glaciation and can shore deposits of the Suolijoki Formation.

Table 1. Quaternarylithostratigraphy,unit descriptions and formal names in Rovaniemi-Tervola area. Awhole strati- graphic sequence is proposed to n ame as the Peräpohja Group.From Paper VI. Geological Survey of Finland 13

Table 2. The correlation of Quaternarylithostratigraphy with earlier studies in the area of southern Finnish Lapland. From Paper VI.

The development of glacial morphology and till tering to 40–55 ka are correct and supported with stratigraphy over the two Weichselian glacial phases the latest TL and OSL age determinations includ- was reconstructed by modelling different scenarios. ing age estimations of the Sihtuuna Sand (Paper Two models were presented: VI). Finally, the interstadial was followed by the 1. In the first model, the initial phase occurred during relatively short but very intensive and large Late the Early Weichselian (Fig. 3a), in oxygen isotope Weichselian glaciation. stage (OIS) 5b and the second one from the begin- ning of the Middle Weichselian to the end of Late Conclusions Weichselian (OIS 4–2) (Fig. 3b). The interstadi- al phase occurred at the end of the Early Weichse- The glacial morphology of the Peräpohjola area, in lian (OIS 5a). southern Finnish Lapland, is dominantly composed 2. In the second model, the first Weichselian glacial of ribbed moraines, drumlins and flutings, the assem- advance was quite modest in extent and covered blage of active-ice morainic landforms of an age of only the area of northernmost Finland (Fig. 4a). the Late Weichselian glaciation. The Ranua interlo- The glacier reached southern Finnish Lapland for bate area with the north-northwest to south-south- the first time during the Middle Weichselian (Fig. east oriented drumlin field is arelic from the old- 4b). Furthermore, the glacier may have also cov- er,probably Middle Weichselian glacial phase and ered southernFinland. The marginal formations has preservedunder cold-based, central area of the in the Pudasjärvi area and from there to northeast last glaciation. The glacial phase during the Middle deposited during the melting phase. An interstadi- Weichselian was obviously the first one to cover the al phase was followed the first glacial phase in OIS southern Finnish Lapland area. 3, meaning that most of the radiocarbon ages clus- Ribbed moraines arethe most detailed studied 14 Pertti Sarala

Fig. 3. Model 1: The glacial morphological and stratigraphical development during the Weichselian in southern Finnish Lapland, when a) the first extensiveglaciation phase occurred during the Early Weichselian, and b) the second during the Middle Weichselian, probably continuing without abreak to the end of Late Weichselian. From Paper VI.

Fig. 4. Model 2: The second interpretation wherea)southern Finnish Lapland stayed ice-free during the Early Weichselian glaciation phase and was b) initially glaciated not until the Middle Weichselian. Icemargin reached at least to the level of southern Finland (cf.Svendsen et al., 2004) and marginal formations in northern Finland were formed during the melting phase of that glacier,beforethe fol- lowing interstadial stage at the end of Middle Weichselian. From Paper VI. Geological Survey of Finland 15 landform types in the area. They consist of three sub- Acknowledgements types: hummocky ribbed moraines, Rogen moraines and minor ribbed moraines. The Sihtuuna moraine, First of all I would like to express my gratitude to Pro- a new morainic landform type in northern Finland, fessor Risto Aario and Professor Vesa Peuraniemi, my is introduced as a result of present study and can be supervisors during the work. Their encouragement classified as a minor ribbed moraine. and guidance were necessary to accompany young re- The formation of ribbed moraines was a two-step searcher to right way during the study. I am especial- process whereatthe first stage, fractured ice-sedi- ly grateful to Risto for making me familiar with nu- ment blocks were moved under ice sheet to form rib- merous morainic landform types here in Finland and like morphology and at the second stage, the sedi- introducing me the world of aerial photo interpreta- ments and the bedrock surface in the areas between tion. The experience of which Vesa has in exploring the ribs were intensively quarried as a consequence of the sources of metals and minerals in till, analysing freeze-thaw process. Quarried material was re-depos- till geochemistry and preparing and studying heavy ited to the next ridges. Thus, the transport distanc- mineral samples were helpful during the work. Also, es of local bedrock fragments (from boulders to fine many discussions on various geomorphological and fraction of till) in the uppermost part of the ribbed till geochemical topics in office and in the field with moraine ridges are only a few tens or hundreds of me- them and constructive criticismtomywritings in- tres. The most suitable conditions for the ribbed mo- spired me in the course of years. raine formation existed during the Late Weichselian This workwas impossible without the support deglaciation, after the Younger Dryas, when the cli- that Igot from the Geological Survey of Finland mate warmed very quickly leading to an imbalance (GTK). The financial support was of course neces- between warm glacier’s surface and cold bottom. sary, but most of all the mental support and guidance The characteristics of ribbed moraines have been that I got from the Mr. Seppo Rossi during the study. utilized in prospecting for Au and its pathfinder el- He was a representative of GTK in this project, but ements in the test areas. The shorttransportation above all a colleague in a journey to amazing world of of mineralized material has become emphasised in ribbed moraines in the Tervola area. I never forgot- many areas, especially in the Petäjävaara area, where ten his patience during the numerous discussions we Au-Cu-bearing, hydrothermally altered contact zone have while I was searching the answers – and maybe between diabase and quartzite in the bedrock was the questions, too. Seppo was also the person, who found after shorttracing of mineralized boulders. encouraged me all the time and believed my ambi- Also in other test sites, if not counting the Kortte- tious target to finalize this thesis. Also, the support I livaara site, the promising source areas were pointed got from Dr. Peter Johansson during the late stage of out, although requiring future studies. work with fruitful discussions and comments on the The observations in the area of Peräpohjola, in manuscripts were helpful when finalizing thesis. Also, southern Finnish Lapland, underlie the importance many advices and discussions during the fieldwork of the investigations of moraine formations and their and writing phase with for example Mr. Jari Nenonen genetic background to succeed in ore prospecting. An and Mr. Vesa Perttunen were encouraging. interpretation of glacial morphology together with I also acknowledge with gratitude Research Direc- test pit surveys are the keys to choose the best equip- tor, Dr. Keijo Nenonen for criticism and comments ment for sampling, to estimate the possibility to suc- for the last manuscripts and for accepting this the- ceed in sampling and also to give a basis for the com- sis for publication in a special publications of GTK. parison of results between different formation types. Also, I thank the head of the Regional Office of the Geological Survey forNorthernFinland,professor Ahti Silvennoinen and his successor Mr. Risto Pie- 16 Pertti Sarala tilä, the head of the Land Use and Environment Mr. References Pasi Lehmuspelto, the early head of the Bedrock and Mineral Resources Dr. Erkki Vanhanen and his suc- Aario,R., 1977. Classification and terminologyofmo rain- cessors, the head of the IT and Information Services ic landforms in Finland.Boreas 6, 87–100. Aario,R., (Editor)1990. Glacial heritage of Northern Fin- Mr. Hannu Kairakari, for giving me to opportunity land; an excursionguide. Nordia tiedonantoja, Sarja A: to carry out this project. 1, 96 p. Many people like Mr. Mikko Kvist, Mr. Antti Pa- Aario,R., Forsström, L., 1979.Glacial stratigraphyofKoil- lismaaand NorthKainuu,Finland. Fennia 157: 2, 1– konen, Mr.Kalevi Tolppi, Mr.Lasse Rauhala, Mr. 49. Mauri Vitikka and Mr. Matti Kantola have contrib- Aario,R., Peuraniemi, V.,1992. Glacial dispersal of till con- uted to the fieldwork. Mrs. Anne Petäjä-Ronkainen, stituents in morainic landforms of different types. In: Mrs. Seija Roman and Mr. Kauko Holappa give me Aario, R., Heikkinen, O. (Eds.), Proceedings of Third International Drumlin Symposium. Geomorphology 6, an introduction to laboratory work. Dr. Teuvo Pernu 9–25. and Mr. Pekka Puhakka helped during the geophysi- Bouchard,M.A., Salonen, V.-P., 1989. Boulder transportin cal measurements. Professor Högne Jungner and Mr. shield areas. In:Kujansuu, R., Saarnisto, M. (Eds.), Gla- cial indicator tracing. Balkema, Rotterdam, 87–107. Kari O. Eskola from the Dating Laboratory of Uni- Clark, C.D., Knight, J.K., Gray,J.T., 2000. Geomorpho- versity of Helsinki supported this work with the anal- logical reconstruction of the Labrador sector of the Lau- ysis of dating samples. I would express my most grate- rentide IceSheet. QuaternaryScience Reviews 19, 1343– ful thanks to all these people. 1366. Eilu, P. ,1999. FINGOLD –apublic database on gold de- I would also like to thank the official referees of the posits in Finland. Tiivistelmä: FINGOLD –julkinen tie- manuscript Professor Raimo Kujansuu and Dr. Kei- tokanta Suomen kultaesiintymistä. Geological Survey of jo Nenonen for suggesting valuableimprovements Finland, ReportofInvestigations 146, 224 p. Glückert, G., 1974. The Kuusamo d rumlin field, north- to the synopsis, Mrs. Carrie Turunen for checking ern Finland. Bulletin of the Geological Society of Fin- the English of the manuscript,Mr. Mika Palosaari land 46, 37–42. for giving linguistic advices and Mrs. Terttu Aalto- Hamborg, M., Hirvas, H., Lagerbäck, R., Mäkinen, K., nen and Mrs. Helena Murtovaara for helping on lit- Nenonen, K., Olsen, L., Rodhe, L., Sutinen, R. &Tho- resen, M., 1986. MapofQuaternarygeology,sheet 2: erature retrieve. Glacial geomorphologyand paleohydrography,Northern Finally, my warmest thanks go to my wife Anna- Fennoscandia 1: 1000 000. Espoo : Trondheim :Upp- Maija and to my wonderful daughter Hanna and sons sala: Geological Survey of Finland :Geological Survey of Norway :Geological Survey of Sweden. Jouni and Olli. You have suffered much in the course Helmens, K. F. ,Räsänen, M. E., Johansson, P. W.,Jung- of years and particularly, during the final stage of fi- ner,H., Korjonen, K., 2000. The Last Interglacial-Gla- nalizing this thesis, when I spend a lot of holidays and cial cycle in NE Fennoscandia: anearly continuous re- evenings over my computer. I am also deeply indebt- cordfromSokli (Finnish Lapland). QuaternaryScience Reviews 19, 1605–1623. ed to my parents Anneli and Risto and my siblings of Hirvas, H., 1991. Pleistocene stratigraphy of Finnish Lap- the interest and encouragement during the work. land. Geological Survey of Finland, Bulletin 354, 123 This work was supported by the Geological Survey p. Hättestrand, C., 1997. Ribbed moraines in Sweden –distri- of Finland, the University of Oulu and the Founda- bution pattern and paleoglaciological implications. Sedi- tion of Research of Natural Resources in Finland. mentarygeology 111, 41–56. Hättestrand, C., Kleman, J., 1999. Ribbed moraine forma- tion. QuaternaryScience Reviews 18, 43–61. 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tion to the maps of Quaternarydeposits 1:400 000. Es- sion guide, 1p.National Committee for Permafrost Re- poo: Geological Survey of Finland. 236 p. search and Technics. Johansson, P. ,Sahala, L., Virtanen, K., 2000. Rantamer- Nenonen, K., Eriksson, B., 2004. Veiksel-jääkausi. In: kit, tuulikerrostumat ja moreenimuodostumat geolo- Koivisto, M. (ed.) Jääkaudet. Porvoo: WSOY, pp.53– gisina luontokohteina. Summary: The most significant 57. raised beaches, aeolian and morainic landforms in Fin- Perttunen, V.,Hanski, E., 2003. TörmäsjärvenjaKoivun land. Geological Survey of Finland, ReportofInvestiga- kartta-alueiden kallioperä. Summary: Pre-Quaterna- tion 151. 76 p. ry rocks of the Törmäsjärvi and Koivu map-sheet ar- Kleman, J., 1994.Preservation of landforms under ice sheets eas. Geological MapofFinland 1:100 000. Explanation and ice caps. Geomorphology 9, 19–32. to the maps of Pre-Quaternaryrocks, Sheets 2631 and Kleman,J., Borgström, I., 1996. Reconstruction on palaeo- 2633. Espoo: Geological Survey of Finland, 88 p. icesheets: The use of geomorphological data. Earth Sur- Peuraniemi, V.,1982. Geochemistryoftill and mode of oc- face Processes and Landforms 21, 893–909. currence of metals in some moraine types in Finland. Ge- Kleman, J., Hättestrand,C., Borgström, I., Stroeven, A., ological Survey of Finland, Bulletin 322, 75 p. 1997. Fennoscandian palaeoglaciology reconstructed us- Punkari, M., 1997. Glacial and glaciofluvial deposits in the ing aglacial geological inversion model. Journal of Gla- interlobate areas of the Scandinavian ice sheet. Quater- ciology 43, 283–289. naryScience Reviews 16, 741–753. Korpela, K., 1969. DieWeichsel-Eiszeit und ihr Intersta- Saarnisto, M., Lunkka, J.P., 2004. Climate variability during dial in Peräpohjola (nördliches Nordfinnland) im Licht the last interglacial-glacial cycle in NW Eurasia. In:Bat- vonsubmoränen Sedimenten. Annales Academiae Sci- tarbee, R.W., Gasse, F. ,Stickley, C.E.(eds.),Past climate entiarum Fennicae AIII: 99, 1–108. variability through Europe and Africa. Developments in Kujansuu, R., 1967. On the deglaciation of western Finn- Paleoenvironmental Research 6, 443–464. ish Lapland. Bulletin de la Commission Géologique de Salonen, V.-P., 1986. Glacial transportdistance distributions Finlande 232, 98 p. of surface boulders in Finland. Geological Survey of Fin- Kurimo, H., 1974. Virtaviivaiset muodot jään liikuntojen land, Bulletin 338, 57 p. kuvastajina Posion-Kuusamon alueella. (Streamline fea- Sarala, P. ,2003. Ribbed-moreenit –jäätikön liikesuunnan tures as indications of ice movements in the -Kuusa- poikittaiset indikaattorit. Summary: Ribbed moraines – mo area, NE-Finland). Terra 86:2, 52–61. transversal indicators of the ice flowdirection. Geologi Kurimo, H., 1977. Pattern of dead-ice deglaciation forms 55 (9–10), 250–253. in western Kemijärvi, Northern Finland. Fennia 153, Sutinen, R., 1992. Glacial deposits, their electrical proper- 43–56. ties and surveying by image interpretation and ground Lundqvist, J., 1969. Problems of the so-called Rogen mo- penetrating radar.Geological Survey of Finland, Bulle- raine. Sveriges Geologiska Undersökning C648, 1–32. tin 359, 123 p. Lundqvist, J., 1989. Rogen (ribbed) moraine –identifi- Svendsen, J., Alexanderson, H., A stakhov, V.,Demidov, cation and possible origin. SedimentaryGeology 62:2, I., Dowdeswell, J., Funder, S., Gataullin, V.,Henrik- 281–292. sen, M., Hjort, C., Houmark-Nielsen, M., Hubberten, Lundqvist, J., 1997. Rogen moraine –anexample of two- H., Ingolfsson, O., Jakobsson, M., Kjær,K., Larsen, step formation of glacial landscapes. SedimentaryGeol- E.,Lokrantz, H., Lunkka, J.-P., Lyså, A., Mangerud, ogy 111, 27–40. J., Matiouchkov, A., Murray,A., Möller,P., Niessen, F. , Mäkinen, K., 1999. Icewedge casts in Finnish Lapland. In: Nikolskaya, O., Polyak, L., Saarnisto, M., Siegert, C., Seppälä, M., Eerola, M. (comps.), Nordic symposium Siegert, M., Spielhagen, R., Stein, R., 2004. Late Qua- on changesinpermafrost and periglacial environment : ternaryice sheet historyofnorthern Eurasia. Quaterna- scientific and technical approach, Kevo,Finland, 2–24 ry Science Reviews 23, 1229–1271. August 1999 :programme, participants, abstracts, excur-