Caledonian and Baikalian tectonic structures on Varanger Peninsula, Finnmark, Norway, and coastal areas of Kola Peninsula, NW Russia

Caledonian and Baikalian tectonic structures on Varanger Peninsula, Finnmark, Norway, and coastal areas of Kola Peninsula, NW Russia

DAVID ROBERT5

Roberts,D.1996:Caledo nianandBaikalian tectoni c st ructuresonVarangerPeninsula,Finn mark,Norway,and coas- tal areas ofKolaPeninsula,NWRussia.Nor. geol. unders.Bull.431,59-65.

Based ondatacompiled from biostratig raphy,radiom etri cdating and palaeomagn et icst udies, contrac t ionaldefor- matio n and low-grademetamorphismintheNeop rot erozoicto earliestPalaeozoicsuccessionsofcoastalareas of NENorwayandNWRussia have beenconstra ined totwo mainstages.(1)LateVendiantoEarly Camb rianBaikalian defo rmation,with mainlyNW-5Etrendin gfolds,affected Upp erRiphean seq uenceson Rybachiand 5redniinRussia.

Thesestruct urescanbefollowedintothe eastern part ofVarange rPeninsula.(2)Late 5ilurian toEarlyDevoni an, Scandiandeforma tionand met amo rphism, wit h fold s andthrusts ofmainlyNE-5Wtrend , arerecorded principallyin western part s ofVarang er,in the Caledonianparautoc hthonandallochthon.Cross-foldsandsecond cleavagesin part s ofNEVarangermay alsobe ofCaledo nianage.

Within the succession oftheTanafj orden-Varangerfj ordenRegion of 5W VarangerPeninsula,palaeocurren tdata indicatethatin thepost-glacialMid Vendia ntoEarly Cam brianperiodan upliftingland mass in thenort heast was the major source areafor detritus.Thisisin harmon y wit hthe notion ofarisingBaikalian orogenicand topogr aph ic highduringthis same period,in and beyondtheregionnow occupiedbytheRyb achiPenin sula. Com biningall the evidence,the Varange r Penin sulathus appearsto bein thesomewhat unique situat ionofexpo singvestigesof both CaledonianandBaikalianstructuresandlow -grademetamorphic fabrics.Mut uallyinte rferingfold s and cleavages occurinthe easte rn halfof the Barents5ea Region,notheastoftheTrollfjorden-KomagelvaFaultZone.

Oavid Roberts,Norgesgeolog iskeundersekelse,p.a.Box 3006 i.ade,N-7002 Trondheim,Norway.

Introduction

In recent years, research within the Norweg ian-Russian collaboration progr amme 'Nort h Area' in Northeast Finnmark, Norway, and the Kola Peninsula, NW Russia, hasled to severalimp ortant advancesin our know ledge of the Neoproterozoic sed imentary successionsoccurr ing on the Varanger, Rybachi and Sredni Peninsulas and Kildin Island (Fig.1) along the coastal fringes of the Barents Sea (several papers in Roberts & Nordgule n 1995).Although investigati o ns of Iit host rat ig raphy and sedimentary facies have formed the backbone of the Neoproterozo ic project, research st udies have included topicssuchasstructu re,low-g rademetamorphism,isot o- pic dating and palaeomag netic investigations,some of whichare still in prog ress.

An im portant factor in thetectonothermal history of most geological terranes is the tim ing of the principal phaseof tectonic deformation.In the case of Varanger Peninsula,it has been assumed almostwit hout question that we are dealing exclusivelywith Caledonian deforma- tion,and by and large ast ruct ural architectureascribed to the Late Silurian-Early Devonian Scandian event.

Almosta centuryago, howeve r,Russianand Finn ishgeo- logistshad considered that Varange r may well form a western extension of the so-called 'Timanian mountain chain' stretching from the Timan s(Fig.2), alongthe nor- thern coast of the Kola Peninsulaand im medi ate ly off- shore (Ramsay 1899, Tscherny schev 1901). Schatsky (1935) later ascribed this Timanide deformation to the Baikalianoroge ny.

Since that time, little attention has been directed

Fig.1.Locationmap showingtheVaranger, Rybachi andSredniPeninsulas and Kildi n Island,NE Norway-NWRussia.Thepericra- tonic(TVR,Sredni,Kildin) and basinal(BSR, Ryba chi) doma ins areindicatedby different do tted orname n ts. TVR - Tan afjorden- VarangerfjordenRegion; BSR - BarentsSea Region; TKFZ - Trollfjorden-Kom age/va Fault Zone; SRFZ- Sredni-Rybachi Fault Zone;

GNC - Gaissa Nappe Complex; TN - Tanah orn Nappe. The area witho ut orna- men t is underlain by Archaean to Early Proterozoic crystallinerocks.

100 200 km

I I

60 ^{David Raberts}

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68· " \

\\

o

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P e c hora

NGU-BULL 431.1996

60·E

~--_--'!WrF

Fig.2.Location mapshowingtheTimans,KolaPenin sulaand thenorthernUrals.Theboxedarea isthatshown in moredetail in Fig s.1and3.The shad ed are- as inTim an and theUrals indicate theareas of main outcropofNeop roterazaic rocks.Principal fau ltsintheTimans:WTF- West TimanFault;UF- Centr al Tima n Fault;ETF-East TimanFault. TheNW-SEtrendingbeltdelimitedbythe WTFandCTFcorrespondstothe pericrat on ic domain ofVarange r,Sredni and Kildin.Likewise,thebasinaldoma in (eq uivalent toRybachi andthe 8SR ofVara ng er)isthat between theCTF andtheETF.VP - Varanger Peninsula;RP - RybachiPeninsula;KP- Kanin Peninsula.The structuralsubdivisionofTimanis modi fiedfrommapversions present ed by Getsen(1987), Olovyanishnikov (1995)andSiedlecka&Roberts(1995).

towards these earlyideas,althoughthey were mentioned by Siedlecka & Siedlecki (1967) and discussed by Siedlecka (1975) in hercomprehensivereview of Russian and other early literature of the Finnmark-Timan regi on . At that timethe issue could not beresolved. Specific stu- dies wit hi n part of the'Nort h Area'programme,how ever, havehelped to refi ne our constraints on the time ofthe main tectonothermal event. Comparison with st ruct ural trend s prevailing onVaranger Peninsulahas thus allowed reasoned conclusionsto be made concerning the likely regional distr ibutionof Baikalianand Caledonianstructu- res. The purpose of thisshort cont rib ut ion isto present relevant data which suggest that Baikalian st ructures almost certainlyoccur in the eastern parts of Varanger Peninsula.

Geological framewo rk

Detailsof the formal lit hostr ati g raphies of the Neopro- terozoic successions of the Varanger,Rybachiand Sredni Peninsulas and Kildin Island (Fig.1) can be found in Siedlecka&Ro bert s(1992) and Sied leckaet al.(1995a,b).

On Varanger, the polyphase NW-SE-trend ing Troll fjo r- den-Komagelva FaultZone (TKFZ) effectively divides the peninsulaint otwo region s, and canbefollow ed sout h- eastwardson to the Rybachi andSred niPeninsulas,whe- reithas been termed theSredni-Rybach iFault Zone(SRFZ) (Robert s1995) (Fig.1).

The sou t hw estern Varanger Peninsula (t he Tana- fjorden-VarangerfjordenRegion-TVR)exposesan Upper Ripheanto Cambrianrecord up to 3.5kmthick,including the Early Vendian Varangerian glacial deposits. The UpperRiphean successionalone is some 2.3km in thick-

ness.Thispericratonic realm (Siedlecka&Roberts 1995) also characterises thefluvial,deltaicand coastal marine successio nsonSredni Peninsula andKildinIsland,south- west of theSRFZ,alth ough in this case thereare noglaci- aldeposit spresent and the microfaunalevidencefavours only Late Riphean depo sition (Samuelsson 1995 and in press). InNorthea st Varanger Peninsula(t he BarentsSea Region - BSR)and on Ryb achi,submarine turbidite sys- tems c.3-4 km thick represent a distinctive basinal domain, termed the Rybach i-Vara nger Basin by Drin kwater et al.(1996).Microfaunashere also denote a Late Riphean age. Thus,Vendian and younger deposit s are apparently lacking on both the Sredni and the Rybach iPeninsulas.

Structure and metamorphism

Tectonic stru cturesand metamorphicfeat ures of the sue- cession s on VarangerPeninsulahave beendescribedina num ber of publications,to which the reader isreferred fordetails(e.g.Roberts1972,Bevinsetal. 1986,Riceetal.

1989, Sied lecka & Roberts1992,Karpuzet al.1993).In the case of theRybac hiand Sredni Peninsulas,the most rele- vantcontributionson these particular topi csare those by Negrutsa (1971), Roberts (1995) and Rice & Roberts (1995).

Thestruc turaldeformationand metamo rph ismof the- se various successions changes appreciably in crossing the majo rNW-SEfault zone(TKFZ and SRFZ). Successions in most of thepericratonic domainof SWVaranger(TVR), Sredni and Kild inin general display only lower diagene- sis-grade compactiona l fabrics.Folds,where present at

NGU-BULL431,1996 DavidRoberts 61

FINLAND

Ryba chiPeninsula

RUSSIA

Kildin Island __

/' ~ --­

/ ' ^/

/ ' / ' / '

SOKm

Fig. 3. Simp li fied map of the varanqer- Rybachi-Sredni- Kildin tract showing the principa lstructu raltrends,mostlytheaxia l surface tracesoffoldsbutpar tlythe strikeof N-toNE-dippingstratain Kild in,Sredniand southernmostVaranger.

all, are gentle upright structures, trend broadly E-W to NW-SEand lack any pervasive axial surface cleavage;and their precise age is uncertain.Towards the west in the TVR on Varanger Peninsula,however,one is passing into the Caledonian parautochthon and ultimately into the Lower Allochthon (Gaissa Nappe Complex- Fig.1 ),where folds become quite common,trend c.NE-SW (Fig.3), face southeast, and carry a penetrative axial-planar cleavage.

In contrast,in the basinal domain on Rybachi, northe- ast of the SRFZ, the turbiditic rocks show abundant NW- SE trending and SW-facing, open to tight folds (Fig.3) and an associated, penetrative, tightly spaced or slaty cleava- ge.Illite crystallinity data (illite 002 peak) record a lower anchizone grade of metamorphism in the northeast,but only upper diagenesis grade moving closer to the SRFZ (Rice et aI.1995).The age of this tectonothermal cycle on Rybachi has not yet been determined with any precision ; however,several Russian workers have assumed that it equates with the Baikalian of Timan.More information is provided below.

Some 60 km to the northwest,in the easternmost part of the Barents Sea Region of Varanger Peninsula,much the same NW-SE (t o N-S) fold-and-c1eavage trend is encountered (Fig.3), although cross-folds cause local structural complexities (Roberts 1972, Herrevold 1993).

This low-grade metamorphic phase has not yet been dated. Moving towardsthe northwest within the BSR, the fold-axialtrend gradauallysw ings through N-S to NE-SW and ultimately ENE-WSW (Fig.3), with ubiquitous SE- facing tight folds,local thrusts and the Tanahorn Nappe (Fig.1) signifying their association with the Caledonian orogenic cycle.

Timing of deformation and metamorphism

In considering the currently known constraints on the age,or ages of the fold ing and very low-grade metamor- phism outlined above, the map of principal structural trends (Fig.3) providesa useful backcloth; and one which

holds moresignificancethan might at first meet the eye.

Since the situation on the Varanger Peninsula is evidently unclear, except, as mentioned, in the far west where Caledonian structures prevail,it is more appropriate to consider first the relevant data from the Russian areas.As well as structural (fold axial)trend, biostratigraphic and isotopic constraints are clearly important, but interesting information can also be gained from palaeocurrent data and from field and laboratory studies on mafic dykes.

Rybachi, Sredni and Kildin

Biostratigraphic evidence from these three areasshow s that the successions are wholly Upper Riphean (Samuelsson 1995).Earlier,the stratigraphically highest unit on Sredni Peninsula, the Volokovaya Group (Siedlecka et al. 1995a),had been assigneda Vendian age by Russian workers, but this is nowrej ected on the basis of recent microfossil studies (Samuelsson 1995 and in press).This also accords better withthe fact that there are no Varangerian tillites on Sredni.

The diagenetic compactional fabric present in the peli- tes on Sredni and Kildin hasbeen dated using the Rb-Sr method on illite subfractions (Gorokhov et aI.1995). Early authigenic illite subfractionsfrom two separate formati- ons from the Sredni Peninsulayielded an age of 610-620 Ma.Close to the SRFZ,on Sredni,a widely spaced NW-SE trending cleavage is quite well developed.From one par- ticular formation in this subarea, within the fault zone, Gorokhov et al.(1995)separated a second,evenfiner,illite subfraction and obtained a Rb-Sr maximum age for this of 570 Ma. Thiswas considered to relate to an influxof non-marine,subsurface water arising from an episode of fault movement along the SRFZ.

On Rybachi, the common NW-SE trending, open to tight,SW-facing folds are believed to represent a stage of basin inversion (Robert s 1995) - termed epikinegenesis (Raznitsyn 1972)in Russianliterature - the folds and clea- vage gradually dying out towards,and just across,the SRFZ. Accepting that the 570 Ma maximum age noted

62 Dovid Roberts

abovetruly relatestofaultmot ion,thenthispresumab ly reflects theinversionandwidespread SW-directed com- pressional deformationrepresent ed bythe st ruct ures on RybachLAlternatively,the'maximum-s70' agemayindi- cate the end stageoftheinversion, such that the peak metamorphicage,reflectedin the pervasive cleavage on Rybachi,could be somewhere between 610(Srednidia- genesis)and 570 Ma.

In contrast,the minimumage forthe maindeform ati- onon Rybachi Peninsula ispoorly constrained.Innorth- westernareasof the peninsula,a fewdolerite dykes up to 6.5 min thickness cut through theNW-SE-tr endin gfolds and cleavageat hig hangles;i.e.,theytrend c.NE-SW.An 4°Ar_39Ar laser microprobe study gave no defi nitive emplacemen t age, suggesting only that the dykesare older than 450-400 model ages(Roberts&Onstott1995), while palaeomagnetic data favoured a Late Vendian to Cambrian age(Torsvik et al. 1995). The folding and meta- morph ismof the Rybachisuccession, which preceded the dyke intrusion,would therefore seem to fall within the time inte rval Late Vendian to Early Cambrian, with the Vendian period takento extendfrom 650 to 545 Ma.

Turning briefly to the situ ation in Timan, which has similar pericraton ic and basinal palaeoenv iron mental zones as in the Rybachi-Sredni-Varanger region (Fig.2), radiometric datingthere,mostly bythe K-Armethod,has indicated that theLate Riphean successio nwasdeform ed and metamorphosedintwo stages; (1)amain'Baikalian' tectonothe rmalevent datingto the period c.600-575Ma (Malkov 1992,recalculatedages);(2) aless prominent sta- geofdeforma tion inthe period c.505-470 Ma.Theage constraint s so far availablefrom Rybachi andSrednithus supp ort the long -standing notion that the principal Baikalian deformation alsoaffect ed theseparticular coas- tal Kola,Neoproterozoic successions.

Varanger Peninsula

Barents Sea Region:

varde

Asnoted earlie r,this easternmost partof the BSR ischa- racterised by a principal cleavage and fold axial trend whichis roug hly NNW-SSE,thoug hwit h localvariations dueto c.EN E-WSW cross-f oldin g(Ro berts1972,He r rev ol d etal., inprep.).Itwasiniti allyassumedby Roberts (1972) that all foldi ngin thisareadevelop edduringLateSilurian, Caledonian(Scandian) orog enesis.An explanationforthe anomalous,c.NW-SE struct ural trend and facing reversal was sou gh t in the likely bufferin g effect of a basem ent 'ridge' concealed beneath the sea area southeast of Varanger Peninsula. Rice et al.(1989) interpreted the same,WSW-facing stru cturesas tipfoldsassociatedwith a late-stage, backthrus t sense of movement alon g an inferredsolethrustbeneat hthe BSR,thusappealing to a lateScandianphaseofdeformation.

Mafic dykesarerareinthisparticular part of theBSR and have,as yet,offeredmeagreconst raints on the min i- mum age forthe cleavage and fold develop men t. The

NGU-BULL431. 1996

c.NE-SW-trendingdykesarecom paratively unaltered and post- date the early,NNW-SSE-trend ing spacedcleavage.

As yet,the only isotopicdating availableonthesedykes is that of K-Ardatawhich haveprovidedages of c.350Ma (Beckinsale et al. 1975).Combining the biostratigraphic and published K-Ar data,we therefo re havea meaning- less time interval of at least 300 million years (latest Riphean to earliestCarboniferous)inwhich to placethe tectonometa mo rphictransfo rmation of the host rocksto these dykes.

Despite the lack of precise radiome tricdating,sign ifi- cantclues asto thelikely age of these NNW-SSE-trend ing, syn-c1eavage folds can be sou gh t in a consideration of the structural trend(Fig.3) and thecharacter of the cleav- age,aided by an exam inat ion of satelli te images(Karpuz et al. 1993) and comparative field stud ies both on Rybachiand in thispart oftheBSR on VarangerPeninsula.

To the present author,the structures andfabrics encoun- tered intheVardedistrict are very muchremin iscent of those seen onthe RybachiPeninsula,the inference being that againwe are conceivablydealing with stru ct uresof Baikalian age(Robert s1993,1995).Ifanyt hing,thecleav- agein the eastern BSR is slig ht ly moredomainal incha- racterthan thaton Rybachi,but thisis part lybecauseof Iithological differences and the fact that the Baikalian deformat io nand metamorphism was probab ly dyingout lat erally,northwestwards.

Cross-fo ldsof ENE-WSWto NE-SW,or even E-W trend are common in thisarea,asreflectedin the dome-and- basin map pattern (Ro berts1972,Siedlecki1980,Riceet al. 1989,Aamodt et al.1996).As suchtransverse stru ctu- res are absentonRybachi(Ro bert s1995),itisreasonable to argue that the cross-folds in the eastern BSRare Caledonian fol ds which have develop ed as a result of open, SSE-directed macro-b uckling of pre-existing Baikalian st ruct ures. Aswell asthese mutu ally interfering folds of disparate age, two cleavages are also present locally (Roberts 1995), but no systematic work hasyet been done to assesstheregionalextent of these cleava- ges. In such a scenario one would expect the NW-SE, assumed 'Baikalian' cleavageto die out gradua lly west- wards; andtheNE-SW 'Caledonian'cleavage to appear andinte nsifyinthesame direct io n.

There has been only oneattempt to date a cleavage directly,that ofTaylo r &Pickering (19 8 1). Th e se authors produced an impreciseRb-Sr whole-rockdateof520±47 Mafrom cleavedpelitesin the KongsfjordFormation near Hamningberg(Fig.3).Althoughnodetailswere given,the cleavagenearthe sampling sitesisknow nto strikec.NE- SW.The sign ificance andinterpretation of thisdatehas been questio ned by Rice et al.(1989)who argued that the first Caledon ian deformation in thispart icular area was of Scand ianage.

Eastern part

of

Tectonic deformation in this particular part of the TVR

NGU-BULL431,1996

was clearly less intense than in the BSR directly northeast of the TKFZ.That the TKFZalso represents a metamorphic break isseen in the fact that the rocks in this area have yielded illite crystallinity values indicative only of diage- nesis grade (Bevins et al. 1986).There is also no trace of any regionally penetrative,steeply dipping cleavage in this southeastern part of the Tanafjorden-Varangerfjor- den Region.

A maximumage both for the diagenetic compactional fabricand for the oldest folds is set by the fact that the youngest formation here, the Stappogiedde, is of assu- med Late Vendian age.Work is in progress(Rb-Sr on illite subfract ions) in an attempt to date the diagenesis.Here, it can be noted that from the southwestern TVG, Dallmeyer& Reuter(1989) have recorded what they des- cribe as a «d iagenet ically related disturbance at c.635 Ma».

In general,the stratig raph ic succession in the eastern TVR dips at a few degrees to the north with large-scale, gentle,upright folding on c.E-Waxesappearing within10 km of the TKFZ(Fig.3).The axial trend of these folds is thus oblique to the main fault zone.In their trend and en echelon pattern these folds are comparable to post-cle- avage folds occurring close to the SRFZ on Sredni Peninsula (Ro bert s 1995),which are indicatorsof dextral strike-slip movement. Mesoscopic shear zones trending ENE-WSW and ESE-WNW, with a generally right-lateral shear sense,have also been recorded in the eastern TVR (Herrevold et al.,in prep.).Closer to the TKFZ,small-scale NW-SE-trending, SW-facingfolds and minor thrusts indi- cate a phase of SW-directed compression (Karpuz et al.

1993)or possibly transpression.Although the relations- hip of these SW-facing structuresto the E-W folds is unk- nown,asis the actual age of the folds, it is reasonable to assume that the former are older and quite likely Baikalian.

The precise age of uncommon, c.N-Strending mafic dykes occurring in two places along the southeastern coast of the TVR remainsunknown. K-Ardata have yiel- ded a figure of c.350 Ma (Beckinsale et al. 1975) while 4°Ar_39Ar pyroxene data are inconclusive (Roberts et al.

1995). One of these dykes has yielded palaeomagnetic data suggesting that its age may be Late Vendian to Early Cambrian (Torsvik et al. 1995).For the timebeing, at least, we therefore have no reliable upper constraint in this area for the timing of diagenesis or fold deformation.

The importance of hiatuses and angular unconformiti- es in providing records of distant orogenic events is well known,and theirpotential significance in this Finnmark- Kola region has been noted by Schatsky (1960) and Siedlecka (1975). Accepting that the rocks on Rybachi Peninsula and in the Vardo district of the Barents Sea Region have been affected by a Late Vendian-Early Cambrian Baikalian tectonothermal event associated with basin invers ion and uplift , then the northwestern 'tail end'of the Baikalian may conceivably be reflected in breaks in the Iithostratigraphyof the TVR. In this regard, the sedimentologicalinvestigationsof Banks et al.(1971)

Oavid Roberts 63

in the TVR are highly relevant.These authors, and also Edwards (1984), have pointed to an important change in sediment dispersal patterns which occurred shortly after the end of the Varangerian glacial epoch. During this period,Le.broadly Mid Vendian to Early Cambrian,pala- eocurrent data indicate that the major source area for Vestertana Group sedimentation lay somewhere to the present-day northeast. Banks et al.(1971)suggested that this uplifted northeasterly situated «land mass»was pro- bably located somewhere to the northeast of the Trollfjorden-Komagelva Fault Zone, or a related parallel fault.

Although not mentioned in name,the land mass refer- red to by Banks et al.(1971) assupplying the major volu- me of detritus to the Vestertana Group was almost cer- tainly the rising topographic high which resulted from the Baikalian basinal inversion, tectonic deformation and metamorphism of the Upper Riphean succession ,parts of which are now exposed on the Rybachi Peninsula.

Vendian deposits are absenton Rybachiand Sredni, and on Kildin Island, and it is morelikely than not that they were never deposited in these particular 'eastern' areas during this period of inversionand diastrophism.

Western VarangerPeninsula; BSR and TVR

The structural deformation and metamorphism of the northwestern halves of both the Barents Sea Region and the Tanafjorden-Varangerfjorden Region have been documented in many papers (full bibliography in Siedlecka & Roberts 1992).In this present contribution,it will suffice to note that the widespread folding and thrus- ting- SE-facingin the western TVR and SSE-facingin the western BSR - and related metamorphism were acqui- red as a result of Caledonian orogenesis. In the parau- tochthon of the western TVR, the youngest formation affected by this deformation is of Early Cambrian age, whereas on the nearby Digermul Peninsula Oust west of southwestern Varanger Peninsula) the deformed succes- sion, part of the Gaissa Nappe Complex,extends up into the Tremadoc.

Constraints on the precise timing of this pervasive fold- and-thrust event, however, remain poor. Radiometric data from the Gaissa Nappe Complexare not definitive, an age of c.440 Ma (K-Ar) having been suggested by Dallmeyer et al. (1989) as a maximum for slaty cleavage development.Earlier, a Rb-Sr whole-rockisochron age of c.504 Ma had been obtainedon cleaved pelites from the western TVR (Sturt et aI.1975),but the reliability of this date has been contested (Dallmeyer & Reuter 1989).

Bylund (1994) has reported palaeomagnetic data from two sites in the western most TVR, also in the Gaissa Nappe, which provide evidence of an Early Ordovician remagnetisation event in those rocks.Clearly, we are in dire need of reliable,precisedatingfrom theseareas.For the present,the general consensus is that the principal tectonometamorphic event is Scandian, in the time inter- val Late Silurian to Early Devonian.

64 ^DavidRoberts NGU-BULL431,1996

Conclusions

Based partly on constraints provided by biostratigraphic, radiometric and palaeomagnetic invest igat ions, the timing of deformation and very low-grade metamor- phism of the Neoproterozoicto earliest Palaeozoicsue- cessions on the Varanger,Rybachiand SredniPeninsulas can be deduced.A significantelement which also has a bearing on the topic is that of fold axial trend and the character ofthe associated,pervasive,axial planar cleava- ge. Palaeocurrentdata are also shown to provide crucial information bearing on the question of timing of oroge- nesis.

A principal conclusion is that the Varanger Peninsula is in the somewhat unique situation of exposing the vesti- ges of both Caledonianand Baikalian tectonic structures and low -g rade metamorphic fabrics. In the Rybachi- Sredni-Kildin area in Russia, the tectonothermal event marking the basinal inversion or epikinegen ic stage appears to fall in the period Late Vendian to Early Cambrian, correspond ingto theBaikalianorogenyof ear- lier Russian worke rs. The prominent, Baikalian, NW-SE fold-and-c1eavage trend seen on Rybachi Peninsula can be traced without difficulty into the Varde district of the eastern Barents Sea Region of Varanger Peninsula,where it is affected by common cross-folds of Caledon ian,pro- bably Scandian trend. Two cleavages occur locally.

Further northwest in the Barents Sea Region,Caledonian structures and metamorphic fabrics gradually become predominant.

The situation regarding timing of deformation in the TVR ofVaranger Peninsula is lessclear,except of coursein the Caledonianparautochthon and Lower Allochthon in the west where Scandian deformat ion and metamor- phismis dominant. In the eastern TVR,where the strati- graphy extends up into the Late Vendian,a reliable upper (mi nimum)constraint for the deformation is so far lac- king,but unconformitiesmayinst ead be providing reflec- tions of distant Baikalian movements. Sedimentological work in this part of southern Va ra ng e r Peninsu la has show n that in the post-gl acial Mid Vend ian to Early Cam brian period themajo r sourcefor thedetritu s accu- mulatin gintheVestertana Grou pwas a landmass situa- ted somewhereto the northeast.This is in good accor- dance with the conceptof a rising Baikalianorogenic welt and topographichigh in and beyond the region of pre- sent-dayRybachi Peninsula.

Acknowledgements

The author is grateful to RoyGabr ielsen,5tephen Lippard and Brian 5turt fortheirhelpfulrevie w s of themanu script;toAnna5iedlecka for comments at a later stage; and to Valery Moralev and Vsevolod Olovya nishnikov fordiscussion s onaspectsof the geology ofTima n.

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Manuscript received April-May7996;finalmanuscrip tready July 7996.