NGU-BULL 436, 2000 - PAGE 14 7

Depositional environment and apparent age of the Fauske carbonate conglomerate, North Norwegian Caledonides

VICTOR A. MELEZHIK, TOM HELDAL, DAVID ROB ERTS, IGOR M. GOROKHOV& ANTHONY E. FALLlCK

Melezhik, V.A., Heldal, T., Roberts, D., Gorokhov, I.M. & Fallick, A.E. 2000: Depositio nal environment and apparent age of th e Fauske carbonate cong lomerate, North Norwegian Caledonides. Norges geologiske uridersekelse Bulletin 436, 147-168.

The Fauske conglomerate represents a rather rare case of a monomi ct carbo nate conglo merate in the Late Neoprot erozoic to 5i1 urian, Iithostratigraphic successions of t he Norwegian Caledo nides.Lith ological variet ies of thi s conglomerate unit fro m th e Lovgavlen quarry have a highly decorative quality and are well known in both dom estic and interna tional market s under t radin g names such as 'Norwegian Rose', 'Jaune Rose','Norwegian Green', 'Antique Fence' and 'Hermelin'. The Fauske conglomerate is a 60 m-t hick unit which rests on either dark grey ('blue') calcite marbles or white do lomite marbles. The latter are joi nted and fragm ent ed, and also appear as sedimentary collapse­ breccia and debris where they are in direct contact wit h th e conglom erate. Althoug h t he Fauske cong lomerate has been involved in two main pulsesof Caledonian tecto nic deform ation, which prod uced an early, syn-metamorphic flatt ening of th e c1 asts and a later folding or rot ation of c1 astsint o a spaced cleavage, the overall sedimentary featu res are st ill remarkably well preserved. The Fauske cong lomerate unit consists of 25 beds (5 cm to 3 metres t hick) comprising landslide, carbonat e debris and carbonate breccia- conglom ero-breccias- greywacke lithofacies. Blocks,fragm ent s, cobbles, pebb lesand smaller c1 asts are mainly of white dolostone and pink, beige, white and 'blue' calcite marbles. The mat rix has a granob lastic texture and similar range in lit hology wit h variable amo unts of quartz, fuchsite, sericite, muscovite and chlorite. With in the unit, an upward finin g of th e c1 astsisfollowed by th e gradual developm ent of calcareous greywacke layers which show both cross beddin g and channelling. The depositional model involves: (i) a locally develop ed, tecton ically unstable carbonate shelf-margin , (ii) a temporary lowering of sea level, (iii) formation of a high-relief, shore-to -basin fault scarp followed by (iv) th e development of a channel, with (v) subsequent, long -distance transport of c1 asts of pink carbonates from the conti nent-basin margin, which were (vi) redepos ited togeth er wit h a carbonate debris (white dolom ite and 'blue' calcite marbles) on t he tectoni cally fragment ing edge of a carbon ate shelf. Bot h matrix and peb bles show a similar range in isotopi c values: -1.9 to +0.6%0 (vs. PDB) for Ol3Cea rb and 0.70896 to 0.70946 for 875r/865r.The least altered 875r/865r (0.70896) isotopic value plotted on the calibration curve is consistent with a seawater composition corresponding to ages of 470 -475 , 505-510 and 520, wh ereas the least altered Ol3Cearb (-0.6%0) value matches only 520 Ma.

Victor A. Melezhik, Tom Heldal & David Rob erts, Geolog ical Survey of Norway, N-7491 Trondheim, Nor way; Igor M. Gorokhov, Instituteof Precambrian Geologyand Geochro no logy, nab . Ma karo va 2, 199034 St. Petersburq , Russia; Anthony E. Fall ick, Scottish Univ ersities Envir onmental Research Centre, G75 OQF East Kilb ride, Glasgow, Scotland.

(Heldal 1996) such as 'Norwegian Rose' (pink and w hite), Introduction 'Jaune Rose' (pale pink and w hite), 'Norwegian Green' (white Polymi ct carbo nate-silicate cong lomerates are abundant wit h green patches), 'Antique Fence' (grey wit h w hite veins) rocks in th e Late Neoproterozoic to Siluria n, lith ostrati­ and 'Hermelin' (whi te w ith grey veins). As the se different grap hic successions of the Norwegi an Caledon ides, includ­ types of cong lomerate have an economic significance, th ere ing th ose know n in t he Fauske area (Fig. 1). The conglomer­ isa practical reason for carrying out research on their deposi­ ates occur either as clast- or matr ix-supp ort ed varieties (Fig. tional enviro nme nt and age. Results of such a study should 2a, b). Many of t hem have clasts of schist, qu artzite, vein help to provide better t heore tic al groundsfor future explora­ quartz and white do loston e, and some may contain large tio n of th is and similar deposits. cobb les of vo lcanites (Fig. 2c) or rare fragments of pink mar­ bles (Fig. 2d). Mon omict carbo nate conglomerates, however, represent a rat her rare case. In one unit of carbonate con­ Geological setting glo merate exposed near Fauske, in Nordl and, nor thern Nor­ The Fauske conglomerate constitu tes a c. 60 m-thick lensoid way - th e Fauske conglomera te - predominant ly carbonate unit (Fig. 1) within a formation known from earlier literat ure material composes both t he clast sand t he matrix.This part ic­ as the Fau ske lim eston e (Vogt 1927, Strand 1972) or th e ular cong lomerate has been exploited asa dimensional stone Fauske m arbl es (Rutland & Nicholson 1965). These carbon­ since 1870 from t he Lovgavlen qu arry, and each of t he main ates, both banded calcit e marbl es and do lomite marb les, lithological varieti es is well known und er commercial names were considered to form part of the middle unit (t he Fau ske NGU- BULL 436,2000 - PAG E 148 VICTOR A. M ELEZHIK, TOM HELDAL , DAVID ROBERTS, IGOR M. GOROKHOV & ANTHONY E. FALLlCK

\ \ \ \ \ \

15° 30 '

1000 1000 o Ji--;r-U~..,.-,.-7:-;-;'hnir--===!--.:jS o -1000~/ ~="----"-'tL.-__-'IU«:l'-'------'-_L.-.-~=--"--~ -1000

LEGEND Quaternary dep osit s GASAK :,\,\I'I'E Calcareou s D Mor ai ne mi ca schist • Mica schist Grey, banded, calcite • Cal c-silicute schist Caledo nian units marble IlEUR:,\ :'\AI'I'E • Mic a schis t with • Mica schist and gne iss do lost one boulders t· ~/~ 8 ~lica schist and ~n('iss Binti te-h ornblend e­ SEn:-KOLl • :,\,\PI'E CO'lPLEX D sra uro lite-mica schist IVDI:'\ GS F.L\LLET :'\AI'I'E CO ~ I I' LEX D Qu artzite • Calcite ma r ble Amphibolit e !:::: :',:i Qu artz-mlcu schist • Grey calcite marble Garnet-mi ca sc hist D Schist and gnei ss • LOWE R :,\,\PPES Calcite marble v / Mica schist • wit h bands of Leivset marble Mic a schisl a nd mctu-arkose Fuu ske co nu lomerure H:::::I Ba nded mct a- arkose Dolomite marble Polvm ict o 0 n n n n n l\1ica schist and gneiss cOllglOl11cl"ute + + + Granite gndss

Fig. 1. Location map (a) and simplified geological map (b) of the Fauske area, modified afte r Gustavson (1996). VICTOR A. MELEZHIK, TOM HELDAL, DAVID ROBERTS, NGU-BULL 436,2000 - PAGE 149 IGORM. GOROKHOV& ANTHONY E. FALLlCK

Fig. 2. Photographs of natura l exposures showi ng typical polymict cong lomerates of the Rognan Group : (a) Matr ix-suppo rted conglomerate interbed­ ded wi th gritty and silty greywacke; unso rted and uneven ly distributed c1a sts are represented by arkosic and quartzitic sandstones (pale grey) and do­ lostones (pale bro wn ). In this and the next photo, the c1a sts are flattened and elongat ed within a schistosity at a low angle to the beddi ng.(b) Clast­ suppo rted cong lomerate; c1a sts are quartzitic sandsto nes (palegrey) and dolo stone s (pale brown) in greywacke matr ix.(c) (last-support ed conglomer­ ate; unsort ed c1 astsare quartzitic sandston es (pale grey), int ermediate volcanites(darkgreyl and dolostones (pale brown) in a greywacke matrix. (d) Clast­ supp orted conglomerate; c1 asts are quartzitic sand sto nes (pale grey), amphibolites (black) and pink calcite marbles in an arkosic sandsto ne matrix. The photog raphs were taken along the shore of Saltd alsfjorden, east of 0ynes (Fig. 2). Scale bars = 10 cm.

Marble Group of Nicholson & Rutla nd (1969)) of t hree main rated in th e Upperm ost Allochthon. Later mapp ing showed, st ruct ural eleme nts in t he metamorphic allochtho n of th e however, th at th e Fauske carbo nates we re more likely corre ­ Nordl and Caledo nides. The two main carbo nate fo rmatio ns latable wit h rocks of simi lar metamorphic grade in, e.g., t he we re later placed togeth er under th e name Rogna n Group Hatt fjelld al and Jofjallet Napp es farther south, l.e., t he high ­ (Kollung & Gustavson 1995). Nicholson (1974, p. 184) intro­ est tectoni c units in t he Upper Koli Napp es, part of the Upper duced th e term Fauske Nappefor the mediu m-g rade, marble­ Allocht ho n. Subsequent map compilations have favou red rich successions lyi ng structurally above th e high-grade t his affiliatio n (e.g. Gustavson 1996, Roberts et al. 1998). Gasak Nappe and below rocks of th e Rodlnqsfja llet Nappe As no fossils have been found in t he carbonate forma ­ Complex (including th e Beiarn Nappe). The designation tions of the Rognan Grou p, t he actual ages of the un its are Fauske Nappe 1 has been retained in most recent map compi­ unknown. Earlier workers, e.g. Vogt (1927). considered that lations (Gustavson et al. 1995, 1999, Kollung & Gustavson th e Fauske limestones cou ld be fo llowed sout hw ards and 1995, Gustavson 1996). t hen eastwards along the margin of t he Nasafje llet tectonic In a compilation of tectonostratigraphic units in th e Scan­ window into th e Pieske limestone of Sweden, which Kulling dinavian Caledonides carried out in the early 1980s (Gee et al. (1972, p. 263) con sidered to be of Middle Ordovician age. 1985, Robert s & Gee 1985). the Fauske Napp e was incorpo- Nicho lson & Rutland (1969) did not believe in thi scorrelation, and it has not been verified by later mapping. In another, longer distance correlation, Strand (1972) suggested that the 1. Alt hough use of the same geographical name for differ ent geolog i­ cal units is gen erally not acceptable (Norwegian Commi ttee on Fauske carbonate and its structurally overlying 0ynes con ­ St ratigr aphy; Nystuen 1989), we retain th e name Fauske here pend­ glomerate may be equiva lent to t he Evenes limestone and ing a future decision on revision of nomen clatur e. Evenskjee r conglom erate, respecti vely, of the Ofoten district NGU-BUL L 436.2000 - PAGE 150 VICTOR A. M ELEZHIK, TOM HELDAL. DAVID ROBERTS, IGOR M. GOROKHO V & ANTHONYE.FALLlC K

a

s 50 m

LEGE TO Carbonate brcccia - congtomero-brcccla Dolomite (loc al 'basement') - greywa cJ.:e sandsto ne lith ofaci es c::=J .. c:=J Unexposed area Carbonate debris lithofacies .. Predominantl y 'blue' calcite marble Sy mbols c=J Predominantly white dolomite marble ~ Elevation curves (contour interval I m) i20 ~ .. Pink and wh ite. dolom ite & calcite marb le Strike & dip of bedding

Fig. 3. (a) Three-dimens ion al model show ing locatio n of th e studied sections and channels. (b) Simpl ified geological map of the Lovgavlen quarry. VICTORA. MELEZHIK,TOM HELDAL, DAVID ROBERTS, NGU-BULL 436 ,2000 - PAGE 151 IGORM. GOROKHOV & ANTHONY E.FALLlCK of southern Trams. The possible equiva lence of the Fauske craps,the lateral extension ofthe FClens is at least 500 m, but and Evenes carbonates was also suggested by Nicholson & its tru e dim ensions are unknown. Rutland (1969). In general, the Fe dips at low to moderate angles to th e In this paper, our use of th e name Fauske cong lomerate southeast, which contrasts with th e steep to intermediate (FC) or Fauske carbonate conglomerate is strictly informal. northwesterly dips of most rocks within the Fauske Nappe in The lithofacial and bed-to -bed variations are such that we this particular district (Gustavson 1996). In the quarry, the will also occasionally use th e plura l form, Fauske conglo mer­ lower parts of the FCtend to dip at 20-300 to the SSEwhereas ates (FCs), when referring collectiv ely to this intraformation al the highest exposed beds dip at 35-450 to the SE. The clasts diversity. in th e conglomerates show clear signs of tectonic deforma­ tion , yet there are interesting differences depending on the c1as t lithology. White dolomite c1asts appear to have been Local geology and tectonic largely mechanically rotated into a prominent, tightly spaced deformation cleavage dipping at low angles to th e NW, whereas pink, cal­ The Rognan Group carbonate rocks are comp aratively poor ly cite marble c1 asts are in many cases tightly folded (Fig. 4a) expo sed in th e wide valley imme diately north of Fauske. In with th e spaced cleavage functioning as the axial plane to the l.evqavlen quarry, only the lower contact of the Fauske these mesoscopic folds . Pebble elongation lineat ions plunge conglomerate is exposed, against subjacent dolomite marble at very low angles to the southwest. (Fig. 3). Judging from the quarry exposures and nearby out- In addition to th is quite penetrative spaced cleavage, it is clear th at th e more ductile calcite marb le clasts show th e

Fig. 4. Photog raphs of sawn surfaces in th e Lovgavlen quarry (Section 5, Fig. 3. Plate 5) showing th e typical style of tectonic defor­ mation in the Fauske conglomerate. (a) Tightly folded c1a sts of beige- to red-col­ oured, calcit e marble. Widt h of the photo­ graph is 0.5 m. (b) An inner corner of two walls of the quarry demonstratin g X:Z ra­ tios of ca.10:1 in calcite marble c1 asts com­ pared wit h only ca. 6:1 in dolomite c1 asts (left watt; In th e right wall, norm al to th e c1 ast elongation trend , many of the white dolomi te c1 asts appear to have been large­ ly mechanically rotated into th e second phase cleavage (top right to bottom left) whereas c1a sts of pin k, calcite marble are in many casesfo lded .Height of walls=2.5 m. NGU-BULL 436,2000 - PAGE 152 V/GOR A. M ELEZHIK, TOM HELDA L, DAVID ROBERTS, IGOR M. GOROKHO V &ANTHONY E. FALLlCK

effect of an earlier defo rmat ion which has had only a mini­ mu m effect on t he mu ch more com pete nt dolom ite clast material. In one bed, X:Z ratios of 13:1 in calcite marble clasts comp are w it h only 6.5:1 in dolomite clasts (Fig. 4b). More important ly, t he flatt ened calcite marble c1 asts dip at j ust a slightly greater angle to that of beddi ng; and th e plane of flatt ening parallels t he prin cipal metamorph ic fabric in th e rock.This syn-metamorph ic flatte ning deform ation is t hus presumed to represent t he earliest Caledo nian defo rmation in the Rognan Group. The age of this earlier deformation is not known . While one might infer it to be Scand ian, i.e. Late Silurian to Early Devon ian, a possible Ordo vician age cannot be dismissed at the present time. No pre-pebb le metamor­ phic fabrics could be detect ed in t he pebbles and cobbles. The prominent spaced cleavage wit h folded marble clasts is considered to belong to a second main deformation phase. In addit ion to t hese struct ures, excellent examples of NW­ directed, meso-scale, ramp -and-flat th rusting can be seen in the Lovgavlen quarry; and t hese th rusts and th e earlier fab­ rics pre-date the spaced cleavage. The th rusts are also cut by a few NW-dipp ing mafic dykes and subparallel, t hin quartz veins. The struct ural and dyke-intr usive history of t he FCs is thus a fascinati ng top ic in it self, but wi ll not be considered further in this cont ribu ti on.

The Levqavlen quarry In t he Lovgavlen quarry, 25 beds w ith t hicknesses of 5 cm to 3 metres have been recorded in th e Fauske carbo nate con­ glomerate unit. The FC is character ised by rapid facies Fig. 5. The substrate to the Fauske conglomerate. (a) Banded, whi te to changes, bot h vertically and laterally. Four man-made chan­ pale grey, dolomite marble wi th an irregular upper surface overlain by nels wit h near-vert ical smooth walls cut through t he con­ pink congl om erate s. Note that the irregu lar palaeorelief beneath the cong lome rate is stro ng ly affected by the tectonic deformation, l.e., fold ­ glomerates provide excellent sectio ns t hrough the litho­ ing w it h a spaced cleavage forming t he axial planes to mesoscopic folds . stratigraphy and Iit hofacies.These are here numbered from 1 (b) An 'open' space between two large blocks of white dolomite marb le to 4.ln add itio n, th ere are long, near-vertical quarry faces cut filled with fragments of the same dolomite marble .The do lomi te marble approximately at righ t-angles to th ese channels. forms the substrate to th e Fauske conglomerates. The photograph is taken 6 m below the contact w ith the cong lomera tes. Width of photo­ graph s = 2.5 m. Photogr aph staken from Channel 1, east face. Verticallithofacies change The vert ical facies change described below relates to one of the profiles st retching from Channel 1 towa rds Channe l 3 filled with angular fragme nts of the same dolomite (Fig. Sb). (Fig. 3). These two channels (Plates 1 and 21* ), and partly Foreign clasts have not been observed here. The detach ed Channel 2 (Plat e 3) have been used as the basis for th e blocks of th e basement dolostones may be assigned to a description. landslide facies. Fragmentation of the substrate was appar­ ent ly caused by instability along th e edge of a carbonate Local basement shelf, with the blocks movi ng under the force of gravity. The 'basement' or local substra te to th e FC unit in Channe l 1 Jointing, fragmentation, det achment and initial mov emen ts is composed of white dolomite marbles (Plate 1). These occur red when th e dolostone s were lithified but sti ll rath er massive rocks becom e jo inted close to t he contac t remained uncovered by other sediments/rocks as indicated with t he conglomerates (Fig. Sa).In places, th e dolo mite mar­ by th e lack of foreign c1 asts amo ng fragments filling joint s, ble has been broken into blocks. Som e of th e blocks (up to 6 cavities and open spaces. x 4 m in size) immediately beneat h the carbon ate cong lom ­ erate-breccia sequence have been prized apart or are com­ Carbo nate debris litho facies pletely detached as a result of gravitat ional instability on a The fi rst input of carbonate clasts overlying the landslide steep slope, and t he open spaces between the blocks are facies appears in th e form of carbo nate debris which consti­ tutes Beds 2 to 5 (Plate 1). Each bed in the carbonate debris

1. The follo wing abbreviat ions are used in Plates 1-5: PCM - pin k cal­ lithofacies is characterised by rath er sharp boundaries due to cite marble, WDM - white dolomite mar ble, GDM - grey dolomite difference s in th e mat rix and in th e sizes of clasts. The thick­ marble, BCM- 'blue' calcite marb le. nesses of all the se beds are high ly variable. The carbona te VICTOR A. MELEZHIK, TOM HELDAL, DAVID ROBER TS, NGU-BULL 436, 2000 - PAGE 153 IGORM. GOROKHOV &ANTHONY E.FALL/CK

Fig. 6. Chaot ically deposited, unsort ed blocks and ang ular fragm ent s of pi nk and pale pink calcite marble s and w hite do lomi te marbles in a dark calcareou sschist matrix. Bed 5, carbo nate debris, mass-flow facies.Width of photo graph =2.5 m. Photograph taken from Channel 1, west face. debris facies at the base of the FC is only locally developed and it is rapidly replaced by carbo nate brecciasand conglom­ erates. The beds of carbonate debri s are composed of angular, unsorted blocksand fragme nts of carbonate rocks. The c1a sts are represented by whi te dolostones, whi te and pink calcite marbl es and sing le blocks of w hite-rim med, dark calcite mar­ bles ('blue' marbl es). The clasts range in size from less th an 1 cm to 3 m. Alth ough th e majority of th e white dolo ston e and 'blue' calcite marb les appear as angular fragments, some of t he pink marbles are rounded. In general, t he carbonate debris is composed of large chaotically organised fragm ent s (Fig. 6). However, a few channels filled wit h medium-size, mod erately sorted c1asts have also been recognised in Chan­ nel 1 (Plate l ). The majority of t he 'blue' marble c1 asts and Fig. 7. Photographs illustra ting different style s of bleachin g of 'blue' cal­ cite ma rble in Bed 2. (a) Large rounded blocks of 'blue' calcite marble blocks are bleached around th eir margins and along joints bleached around th eir margins. Width of phot ogr aph = 2.5 m.(b) Large (Fig. l a). The bleaching was apparently caused by oxidation angu lar block of 'blue' calcite marble bleached around it s margi ns and wit h subsequent removal of orga nic material. This might along lami nati on surfaces. Hammer head = 15 cm. Both photograph s have happened in a subaerial enviro nme nt w hen th e 'blue' taken from Channel 2, east face. carbonates were exposed to atmospheric oxygen . Alterna ­ tively, th e loss of organic material could have occurred dur­ ing fresh-water diagenesis in a phr eatic zone w here th e rocks Channell might be du e to an effect of erosion. An exte nsive might have been subjected to alterat ion by oxygen-contain­ erosion of previously deposited beds by newly transported ing fluids. A detailed isotopic study is required before we may deb ris flows migh t have caused very irreg ular contac t sur­ choose between these alternatives. faces, as such features are seen in t he carbona te debris litho­ Beds 3,4 and 5 compose th e bul k of th e carbo nate debris facies in Channels l and 2. Additional effects mig ht also have lith ofacies in Channell . At the same time Bed 2, consist ing of been caused by syn-dep ositi onal deformati on. large blocks of white dolomi te marble and w hite-rimmed The overall sedimento logical features ofth is rock assem­ 'blue' marble, occurs in Channe ll in a very abbr eviated fo rm. blage indicate trans port in and depos ition from a massflow, In contra st, th e same Bed 2 appears in Channel 2 (80 m east in which ill-sorted masses of sediment moved down-slope of Channell , Fig. 3) as th e major unit in th e carbonate debr is du e to a loss of inte rnal stre ngt h of th e sediment mass. At lith ofacies (Plate 3). There, it is compose d of large blocks (:::;5 least two major pul ses of mass flow have been recogni sed in x 1 m in size) of strong ly jointed, white-rimmed, 'blue' mar­ t he carbo nate debris lithofacies. The first is represented by bles (Fig. Zb) and w hite and pale grey dolos tones in a 'blue' Bed 2.The second phase resulte d in partia l erosion of Bed 2 calcite matrix. Beds 3 and 4 are not present in Channel 2 and depositi on of Beds 3-5. Oast material was transport ed (Plate 3). Bed 5 mechanically 'intruded' int o Bed 2 from it s from different sources. White dolostone and 'blue' calcite surface and deformed it. Based on thi s relatio nship, and marbles are derived from a local source which has been iden­ giv en the condition that Beds 3-5 and 2 are almo st mutually tified immediately beneath t he carbona te debris . Clasts of exclusive, it is suggested th at th e attenuation of Bed 2 in pink marble s, on the other hand, are comparatively long NGU-BU LL 436, 2000 - PAGE 154 VICTOR A. M ELEZHIK, TOM HELDAL, DAVID ROBERTS, IGOR M . GORO KHOV s ANTHONY E. FALLlC K

Fig. 8. Upward fin ing of clam within individual beds.(a) Bed 14 exhibits four dist inctive units whi ch correspond to the A, B, Cand D units of a typ ­ ical Bouma sequence. The bed starts with a th ick unit of conglomero­ breccia overlain progr essively by a fine-pebble cong lomerate with paral­ lellamination , a thin unit of current-bedded gritstones, and at the top by a silty greywacke wi th plane-parallel lamination . Height of photograph = 1.2 m.(b) Lower part of Bed 18 (above the dark grey greywacke layer) ex­ hibiting graded bedd ing accompanied by the development of an inter­ nal planar lamination .Height of photograph = 2.5 m. Both photographs taken from Channel 3, east face.

Fig. 9. Originally horizonta lly bedded carbonate breccia showing a grad­ ual upward decrease in fragment size accompanied by the gradual de­ velopment of an internal planar lamination; Beds 8-12. Note that Beds 9 and 11 are distingu ished in the conglomerate sequence by their paler colours caused by a dominance of wh ite dolostone fragmen ts in a pale grey calcarenite matr ix. The c1asts are here (re)orientated with in the D2 (52) schistosity . Fault-related, proximal, submarine channel facies. Height of photograph =2.5 m. Photographs taken from Channel 1, east face. VICTOR A. MELEZHIK, TOM HELDAL, DAVID ROBERTS, NGU-BULL 436, 2000 - PAGE 155 IGORM. GOROKHOV&ANTHONYE.FALLlCK

Fig. 10. Upwar d fining of t he c1as ts within Beds 4­ 12 accompanied by th e gradual development of an internal planar lamination. Heigh t of pho to ­ graph =8.5m. Photographs taken from Channel 1, west face.

Fig. 11. Combination of planar and cross-lamination in Bed 17. (a) Cross­ lamination in the channel filled w ith coarser greywacke sandsto ne (pale brown ) appearing in th e upp erm ost part of Bed 17; note that t he channel t hickness gradually inc reases down dip, and the cross-laminated sand­ sto ne is th en abru ptly replaced by silty greywacke (to the right) which ex­ hib it s no visibl e lamination. Height of pho tograph = 0.6 m.(b) Cross­ laminated sandsto ne channel deve loped in the middle part of Bed 17. Height of photogr aph = 0.75 m. (cl Erosional chann el in laminated dark grey greywacke of Bed 17. The former is composed of current-bedded, pi nk, carbonate gritsto nes and fine-pebble conglomerate; note that the cross-bedding is emp hasised by a rhythmic repetition of cross-bedded calcarenite-greywacke couplets. Fault -related, distal , submarine channel fades . Height of photograph =0.7 m. All photographs taken from Chan­ nel 3, east face.

Fig. 12. The 0.5 m-th ick Bed 7 (middle part ofpho tograph) showing a lat­ eral Bouma sequence; th e bed begins as a bedded, fine-pebble, carbon­ ate conglomerate which is gradually rep laced down-dip by carbona te gritstones, carbonate grit ston es interbedded wi th laminated greywacke, and th en by plane-laminated greywacke and siltstone wi th a massive ap­ pearance. Height of phot ogr aph = 1.7 m. Phot ograph taken from Chan­ tr ansported, as indicated primarily by the ir more round ed nel 2, east face. shapes and the absence of any definite source rock in the vicinity of Fauske (see discussion of geochemical data). observed in Bed 6 as indicated by the imbricated distribution Carbonate breccia-conglomero-breccia-greywacke of predominantly white dolostone fragments (Plate 1). In th e lithofacies upper part of Channel 1, Bed 6 has a thickness of 2 m which The carbonate debris lithofacies is overlain with a sharp, increasesto 4 m dow n-dip within a distance of 12metres.The straigh t contact by fragment-supported carbo nate breccias breccias are comp osed of fragments of the same rocks as represented by Bed 6. High-angle cross-bedd ing has been described in th e deb ris lithofacies. The fragme nts, however, NGU-BULL 43 6, 2000 - PAGE 156 VICTOR A. M ELEZHIK, TOM HELDA L, DAVID ROBE.'nS, IGO R M. GO ROKHO V &ANTHONY E.FALLlCK

Fig. 13. Photograph s illustrati ng different scales of channelling. (a) White, pale grey and pink, small-pebble conglomerates interbedded with dark grey greywackes, the latt er becoming an essential com po nent of the up per part of t he Fauske conglomerate unit; not e that carbonate grit stone s and grey­ wackes usually for m couplets, and that channelling and low-amplit ude, long-wavelength curre nt ripp lesare very characteri stic featuresof the conglo m­ ero-breccia-greywacke Iithofacies. Bed 18, fault-related, distal, subm arine channel facies.Width of photograph = 5 m. Phot ograph taken from Channel 3, east face. (b) Channel (right ofmeasuring tape ) developed in small-pebble congl omerate beds and infilled wi th coarser material. Width of photograph = 2 m. Phot ograph taken from Section 7, Fig. 3, Plate 5. (c) Large-pebble cong lomerates of Bed 2f erode d and channelled, with a subsequent infill of the channel consisting of finely dispersed material (black and dark grey sil ty greywacke) of Beds8-1O. Height of pho tograph = 2.7 m. Photograph taken from Section 2, Fig. 3, Plate 4.

are generally much smaller and 'blue' marbles have never almost uniform down dip, from 1.5 to 2.5 m. In general, the been ob served among the c1as ts. Alth oug h the c1 asts are bed th icknesses in the conglomero-breccia sequence poorly sorted and angular, many ofthe pink marb les are rep­ become rath er constant down dip as compa red to the lower resent ed by well rounded pebbles.Clast size rangesfrom 0.5­ debris lith ofacies. However, th e greywacke beds still exhibit 12 cm in the lower part of Bed 6 to 0.2-7 cm in it s upp er part. highly variable th icknesses. Upward fin ing is evident from systematic measurement s. Conglo mero-breccias are both matr ix- and clast-sup­ Howeve r, th is is almost a cryptic gradation as it is difficult to ported. Fragment s, cobb les, pebbles and smaller c1a sts are detect visually. The breccias are capp ed by a 1-20 cm-t hick main ly of whi te dolostone and pink, beig e and white calcite Bed 7 consisting of laminated, silty greywacke. This is com ­ marb les. The majority of t he clasts are angular or poorly posed of muscovite, biotlte. quartz, plagioclase and calcit e. round ed. However, clasts of pink calcite marbl e as well as a The breccia-grey wacke couplet is overlain by a series of few of the w hite dolomite marbl e are represented by well­ conglomero-breccia beds (8 to 12 in Channel 1, Plate 1; 12 to round ed pebb les. Alt hough c1asts are poorly sorted , graded 15 in Channel 3, Plate 2) containing medium- to small-size bedd ing has been observed in several beds (Fig. 8a, b). Two fragments. The cong lomero-breccias are interbed ded wi th laterally cont inu ous beds (9 and 11) are readily dist ingu ished thin beds and layers of w hite and pink calcarenit e. The con­ in the conglomerate sequence by their paler colours caused glomero-breccia beds (12, 14 and 15) are capped by beds of by a dominance of w hite dolostone fragment s in a pale grey silty greywacke (Plate 2). The thic knesses of indi vidual con­ calcarenite matr ix (Fig. 9). In other cases, the matrix is com­ glomero-br eccia beds range from 0.3 m to more than 2.5 m posed of calcareous schist. Although the matri x shows a sim­ (e.g., Bed 12) whereas calcarenite lenses are usually less t han ilar range in lithology, fuchsite, sericite, muscovite, quar tz 0.2 m in thickness. The th icknesses of Beds 12, 14 and 15 are and chlor ite may be present in variable proportions in addi- VICTORA. MELEZHIK, TOM HELDAL, DAVID ROBERTS, NGU-BULL 436,2000 - PAGE 157 IGO R M. GORO KHOV & ANTHONY E. FALLlCK tion to fine carbonate clasts, a feature which giv es the differ­ distance of 8 m by carbon ategritstones,carbonate gritstones ent beds th eir slightly variable coloration. interbedded wit h laminated greywacke, and th en by plane­ A series of changes in terms of rock structure and litho­ laminated greywacke and siltsto ne wit h a massive appear­ logy can be detected in mov ing upwards in th e stratigraphy ance (Fig. 12, Plate 3). within th e cong lom ero-breccia sequence exposed in Chan­ Overall, the sedimentological features of th e breccia­ nel 1. An upward fining of th e c1 asts is clearly visible within conglomero-breccia-greywacke lit hofacies are comparable both a sequence of beds (Beds 8-12, Fig. 9, Fig. 10) and indi ­ to those found in sequences deposited from debris flow fol­ vid ual beds (e.g., Bed 14, Fig. 8a). This is accompanied by th e lowed by turbidity currents. Available data demon strate that gradual development of an interna l planar lamination in th e many of the conglomero-breccia beds and all th e conglom­ conglomero-breccia. ero-bre ccia-silty greywacke couple ts were deposited from The structure of the silty greywacke, which overlies th e a single debris flow -turbid ity current pulse. The general conglomero-breccia beds, changes upwards in th e stratigra­ upward fin ing of the c1 asts indicates either th at th e c1asts phy.The lowe r silty greywacke, Bed 7, hasan indi stinct planar were transport ed from a greater distance as compared with lamination whereas th e up permost and the thickest Bed 17 is th e clasts from th e carbonate debris lith ofacies or that there characterised by a combination of planar and cross-lamina­ was a rise in sealevel.We suggest that the first option wasthe tion (Fig. 11 a). Cross-lamination appears in channels filled more likely as it is consistent with the observed increased wit h coarser greywacke. These 1 to 15 cm-thick channels are degree of round ness of th e transported c1asts. less than 1.5 m in length and have low-angle erosional con­ tacts with th e silty greywacke. In th e cross-sections, th e rear Conglomero-breccia-greywacke lithofacies parts of th e channels are only 1-2 cm in thic kness and are This lith ofacies lies with a rather subdued erosional contact composed of massive pale grey sandsto ne, but th e channel on top of the channelled and cross-lamina ted greywacke s of th ickness gradually increases down dip. The thic kness Bed 17. The Iithofacies is com posed of pale pink carbonate increase is fol lowed by th e development of visible cross-lam­ grit stones irregularly interbedded with dark grey greywackes ination due to a heterogeneity in lithology resulting from an and subordinate white calcarenit es. Carbonate gritstones alternation of sand- and silt-rich laminae (Fig. 11a). Further and greywackes usually form couplets (Fig. 13a), which start down dip, cross-laminated sandstone is abruptly, though with a 0.2-1.5 m-th ick gritstone layer and end with a 0.1-0.5 confo rmably replaced by silty greywacke which exhibits no m-th ick greywacke layer. The contact between these two visible laminatio n. This channel-greywacke th en becom es lithologies is commonly gradati onal within a distance of 1-2 ind istinguishable from the main greywacke body, both con­ cm. Both gritstones and greywackes exhibit planar and low­ sisting of muscovite, biotite, quartz, plagioclase and calcite angle cross-lamination. Planar and cross-lamin ation is (Fig. 11a). Cross-lami nated sandstone channels have been expressed by th e develop ment of lamin ae with eit her coarse observed mainl y in th e upp ermost parts of silty greywacke or finer c1 astsaswell as by the appearan ce of th in greywacke beds thoug h in a few cases they have been detected in the laminae in the gritty framework. Each carbonate gritstone­ lower and middle parts (Fig. 11 b). greywacke coupl et exposes an erosional relationship with The appearance of cross-laminated sandstone channels th e und erlying one. Clasts of round ed pink calcite marble in th e silty greywacke of Bed 17 is accompanied by the devel­ and semi-ro unded white dolomite marble are poorly sorted. opmen t of numerous 0.5-10 cm-thick layers of white and They exhibit no gradatio n in size within layers. Small-scale pink, cross-bedded carbonate gritstones and fine-pebble channels and pockets of fine-pebble conglomerate in the congl omerate lenses. These layers and lenses are irregu larly gritty framewo rk are com mon phenome na of this lit hofacies. spaced in th e silty greywackesaswell asin the subjacent con­ Some beds at th e base of th e conglomero-breccia- grey­ glomero-breccias.ln places, th e cross-bedding isemphasised wacke lithofacies exhibit graded bedding resembling th at in by a rhythmic repetiti on of cross-bedded conglo merate-ca1­ Bouma sequences. carenite and calcarenite-greywacke couplets (Fig. 11 c). Sedimentological featu res of th e conglo mero-b reccia­ The upper parts of the carbona te breccia-conglomero­ greywacke sandstone lith ofacies indicate that both the clas­ breccia-greywacke lit hofacies exhibi t a sequence of sedi­ tic material and th e finer sediments were transported in and ment ary str uctureswhich are typical of th oseobserved in tu r­ deposited from low-energy currents on a gently inclined bidity current deposits. Bed 14, for example, exhibits four dis­ slope. tinctiv e units (Fig. 8a). The bed starts with a thick unit of massive or graded conglomero-breccia which is overlain pro­ Lateral thickness, c1ast size gressively by a fine-pebble conglomerate with parallel lami­ and lithological variations nation, a th in unit of current-bedded gritstones, and is All the 25 beds recorded in the Lovgavlen quarry show a cer­ capped by a silty greywacke with plane-parallel lamination. tain degr ee of lateral variation in lithology, clast size and These four units appear to correspond to th e A, B, C and D thi ckness. Bed thi ckness has been affected by tectonic strain units of a typical Bouma sequence. While Bed 17 demon­ producing a general th innin g of th e sequence. However, strates a vertical Bouma sequence, Bed 7 in Channel 2 signs of differential tecton ic thi nning of different lithologies, appears to show a lateral Bouma sequence (Fig. 12). The 0.5 such as pinch-and-swell and boud inage, have on ly been m-thick Bed 7 begi ns as a bedded, fine-pebble, carbonate detected in a few, th in (2 to 10 cm th ick), silty greywacke lay­ conglomerate and thi s is gradually replaced down -dip over a ers. Most ot her beds seem to have been similarly affected by NGU -BULL 436, 2000 - PAGE 158 VICTO R A. M ELEZ HIK, TOM HELDAI., DAVID ROBERTS, IGOR M. GOROKHO V s ANTHONY E. FALLlCK

Fig. 14. Substantial chang es in both lithology and clast size docu ­ mented in t he carbonate cong lomerates. (a) Fining in clast size ac­ compa nied by the deve lopment of numerous layersof greywacke (black and dark grey) in Beds 8, 10, 13 and 18. (b) Lateral fining in c1ast size accompan ied by the development of graded bedding. Blocks, ang ular and rounded fragm ent sof 'blue' and w hite calcite marbles (Bed 2e) followed by cobbles of white and grey calcite and dolomite marbles (Bed Zf), wh ich are in turn overlain by the cong lomerates(Beds 8-10) showi ng well-deve loped graded bed­ din g. The graded -bedd ed conglomerates were deposited from a sing le tu rbidit y current. Height of pho tograph (a) = 4.5 m, height of phot ograph (b) =2.5 m.Photograph (a) taken fro m Section 4, Fig. 3, Plate 4; phot ograph (b) taken from Section 1, Fig. 3, Plate 4. VICTORA. MELEZHIK, TOM HELDAL, DAVID RO BERTS, NGU-BULL 43 6, 200 0 - PAGE 159 IGOR M. GO ROKHOV& ANTHONY E.FALLlCK an overall tectonic thi nning. This is also clearly indicated by cong lom erate beds (9 and 11 ). w hich are only 0.1 -0.5 m th ick, very well preserved sedime ntary features such as sedimen­ are distinguishable in th e cong lomerate sequence by t heir tary layering, graded bedd ing, cross-lami nation, erosiona l compara tively pale colour pattern. Alt hough these beds are channels, etc. The measured thickness variations should thin t hey are easy to detect and can be traced both along therefore largely remain comparable wit h the origi nal values. strike and down dip (e.g., Plate 4). The pale coloration is Pronoun ced t hickness variations of primary origin may expressed by a dominance of white do losto ne fragmen ts in a be observed in anyone bed over distances of 10 to 100 m. pale grey calcarenite matrix. The most remarkab le change in thickness,wit h th e complete The examp les described above serve to demonstrate that disappearance of bedsin three direc tions within a distance of the high degree ofvariability in lithology, c1ast size and thic k­ lessthan 100 m, is characteristic of Beds3-6.This can be dem­ nessis a gene ral characterist ic of th e FCs. This implies unsta­ onstrated by comparing the cross-sections recorded in Chan­ ble depositio nal environments.The thickne ssvariation s have nels 1 and 2 (Plates 1 and 3). Beds 3 and 4 are observed in apparently been caused by a number of factors, including

Channel 1t but th ey do not reappear in Channel 2, over a dis­ erosional effects and channellin g, an irreg ular palaeorelief of tance ofonly 90 m. On t he cont rary, Bed 2 is a prom inent unit t he depositional surface and a lateral restriction of turbidity in Channel 2 but reappears in Channel 1 in a considera bly currents. Tectonic factors have also played the ir part in mod­ att enuated form . ifying bed thickness and, as noted earlier, in causing flatten­ Less dramatic though substan tial thi ckness changes w it h ing of the calcite marble clasts in partic ular. associated wedging-out eit her in two or three direct ions have been docum ent ed in Beds 5-7, 9, 11-13, 16 and 25. This Clast composition is demonstrated in th e longit udinal lith ological sections (e.g., Lit hologically, the FCs consist of blocks, fragments, cobbles, Plates 4 and 5). Fine-c1ast cong lomerate of Bed 16 and large­ pebbles and smaller clasts mainly of wh ite dolostone and c1ast cong lomerate of Bed 25 for m med ium-scale erosional pink, beige, white and dark grey ('blue') calcite marbl es (Fig. channels. Bed 25 has a th ickness of 7 m whereas t he lateral 16a). Clasts of quartzites and vein quartz are subordinate. A exte nsion of th e channel is lessth an 50 m.Channelling on dif­ quan titative estimate of c1 ast composition shows th at th e ferent scales isa common featur e of many beds and layers. In clasts of 'blue' calcite marblesare exclusively assigned to Bed th e most common cases, channelsw hich developed in small­ 2 (Figs. 15, 16b) and t hey have never been observed in any pebb le conglomerate beds were infi lled with coarser mate­ ot her bed. Clasts of quartzitesand vein quartz are also prefer­ rial (Fig. 13b). Large-pebbl e conglomerates have also been entia lly concentrated in Bed 2. On t he ot her hand, clasts of ob served to be eroded and channelled, with a subsequent pin k calcit e marble have never been recorded in Bed 2. The infi ll of t he channel consist ing of finely dispersed material fragm ent s of white and grey dolostone, and white calcite (silty greywacke) (Fig. 13c). This impliesth e existence of high ­ marbles are distributed th rough out t he entire sequence and energ y water current s developed on a steep submarine neithe r the vertical nor the lateral dist ribution shows any vis­ slope. Gradually progressing down -slope erosion of grey­ ible regularity (Fig. 15). The main mineral in the matrix is cal­ wacke and fin e-pebbl e conglomera te beds marked by chan­ cite, with minor qu artz and muscovite. The matrix is charac­ nelling and low-amplitude, long -w ave current rippl es are terised by a granob lastic texture and retains no prim ary very characteristic featur es of the conglomero-breccia­ sedimentary featur es. Measured clast-matrix ratios range greywacke lithofacies (Fig. 13a). between 0.3 and 4.6 with an average value at 1.5 (n=30). This A considerable lateral variati on in c1ast size is commo nly indicates the presence of both c1ast-sup ported and matrix­ observed in those bedswhich demonstrate well -pronou nced support ed conglomerates where t he former are predomi­ th ickness variation s. A positive correlat ion between bed nant . However, th e data obtained mu st be t reated with care th ickness and clast size is a common rule for Beds 6, 12 and as some clast-matrix boundaries exhibit a diffu se, unclear 14. These three beds exhibit great lateral variation in c1 ast appearance due to recrystallisation. Alth ou gh the matrix has size and thicknesses w hereas th eir lithological comp osition s a similar range in lith olo gy, fuch site, sericite, muscovite and remain unchanged. In Bed 6, c1ast size rangesfrom 10 x 30 cm chlorite may be present in variable proportions as minor (Section 10, Plate 4) to 2 x 5 cm (Channel 2, Plate 3) wit hin a components in additi on to fine carbo nate c1asts. distance of 100 m. Chemically, all th e carbonate c1asts can be divid ed into Substantial changes in both lithology and clast size have two groups, namely dolomite and calcite marbles (Table 1). been docum ent ed in th e carbonate conglom eratesof Beds8, Dolomite marbles from th e local 'basement' and in th e c1a sts 10, 13 and 18. In th ese casesthe fining in c1ast size is accom­ are ident ical in ter ms of major and t race element abu n­ panie d by the development of numerous layersof greywacke dances. On various diagramst hey are clustered together (Fig. (Fig 14a). As a result, in some casescarbon ate conglom erates 17). clearly ind icating th at th e c1 asts derived from th e under­ are complete ly replaced by greywacke (Bed 13, Sect ion 2, lying dolomite marbl e unit. The Mg/Ca rati o for th e under­ Plate 3; Bed 18, Channel 3, Plate 2). Lateral fining in clast size lying do loston es ranges from 0.58 to 0.64 which is close to has also been observed to be accompanied by th e develop ­ stoichiomet ric dolomite (0.62) w hereas th e average Mg/Ca ment of graded bedd ing (Fig. 14b). ratio fo r all th e c1a sts is 0.53. This apparent ly poi nts to a proc­ Variation s in lithology and c1a st size hamper correlatio n ess of dedolomitisatio n du ring the course of transportation between sect ions separated by unexposed ground . Some and redeposition. beds, however, may serve as a marker. Two white-pebble The overa ll bul k chemical compo sition of ot her carbo n- NGU- BULL 436, 2000 - PAGE 160 VICTOR A. MELEZHIK, TOM HELDAL, DAVI D R0 8ERTS, IGORM. GOROKHOV &ANTHONY E. FALLlCK

Cnl, Xl Bed12

Bed11

Bed10

Beds 8+9+10

Bed8

Cnl, VI Bed6

Cnl, III Cnl, VII Bed5 ~ . J

LS2, X Bed2f I

Bed2e

CLAST·MATRIX DISTRIBUTION

Bed2d I White dolomite marble I Grey dolomite marble White calcite marble Bed2c i Pink calcite marble

'Blue' calcite marble Bed2b I I Mica-rich calcite marble I Amphibole-rich calcite marble Bed2a Quartzite I Vein quartz Bed1 I Matrix

Fig. 15. Composition of c1a sts and matric es measured from different beds. The following abbreviation s are used in the fig ure: Ch1 - Channe l 1, Ch2 - Channel 2, LS1- Longitudinal Section 1, LS2 - Longitudinal Section 2. Roman numerals indica te the section number w hich was used to cou nt pebb le composit ion; th ese sections are marked on Plates 1 and 2. Detailed log s of LS1 and LS2are not presented in th e article but th ey may be obta ined from th e first aut ho r on requ est. VICTOR A. MELEZHIK, TOM HELDAL, DAVID ROBERTS, NGU-BULL436, 2000 - PAGE 161 IGOR M . GOROKHOVs ANTHONY E.FALLlCK

, . ~ 00 ~ (j • ... I 0 r/1 o --::: ~~- o ::E ------_. ~ .~ 0.1 • , • 0.1 ,: .' •

O ~ rnJo ut , , , re ' U 0.1 . 0.1 • C, 60 o :/: .. .. ::2: • Cl ~ -.' q. () / . ~ 0.01 =t----.---r--""l'---"-+--i'--, ·2 -1 0 20 21 22 23 13.' 6180 (SMOW) 6 C (PDB) 24 60

:;: ~ o . • ~ • ::2: 22 e W·/]o. ~ 6 40 0 0+-0 re o , 0 u 00 () o : o ~ fu , 20 -+----.-- ,----.--t---r---, 20 -+--,--.-.-----.----, ·2 -1 0 o 10 20 613C (PDB) MgO, wt% Key Fig. 16. Photog raphs illustrating the variable c1 ast composit ion of the FCs. (a)Carbon ate breccia composed of angu lar fragments and sub­ Clasts round ed pebbl es of pink, calcite marble, white, calcite marble with pink ~ Wh ite calcite marble + White dolomite marble, rim s, and white dolomit e marble in a dark calcarenite matrix. The initial basement flatte ning and elongat ion of c1a sts is a Caledonian D1 fabric. Clast reori­ • Pale calcite marble entatio n and/or folding relates to D2 deformation . Bed 10. Channel 1, o White dolomitemarble Matrix east face.(b) Clasts of 'blue' calcite marbles. These are exclusively as­ e White calcite marble signed to Bed 2. Width of phot ographs = 0.8 m. o Pinkcalcite marble • 'Blue' calcite marble • 'Blue' calcite marble ate c1asts approximates to that of a sandy calcite marble. The Fig. 17.Cross-plotsshowing th e compos ition of different c1 ast lith ologies main siliciclastic component is quartz though variable and matrix. Samples in the shaded areas are considered to have been amou nts of muscovit e may also be present. On a CaO-MgO subjected to alterat ion, l.e., wit h a Mn/Sr ratio > 0.2. Arrows ind icate al­ diagram all t he calcit e marbles plot along a do lomite-calcite teration trend caused by dolomit isation. mixture line (Fig. 17) indicati ng varyi ng degree of do lomitisa­ tion. The various calcite marb le lit hologies are not disti n­ guished by major and t race element geoc hemistry. Even bon and oxygen isotope ratios in carbonate constituent s of tho ugh th is is the case,the clast provenance has to be differ­ t he who le-rock samples were measured on a VG SIRA 10 ent for th e 'blue', white and pink calcite marbles. Whereasth e mass spectro mete r. Calibration to internati onal reference source for t he 'blue' marbles has been identified, th e prove­ materi al was th roug h NBS 19 and precision (1o) for both iso­ nance of t he whi te, and in partic ular, of th e pin k calcite mar­ to pe ratios is better than ±0.20/00 . Oxygen isoto pe data were bles remains enigmatic. corrected using the fractionation factor 1.00913 recom ­ mended by Rosenbaum & Sheppard (1986) for dolomites. Isotope geochemistry The o13C data are reported in per mil (%0) relative to V-PDB and indirect age constraints and th e 0180 data in %0 relativ e to V-SMOW. Rb-Sranalyseswere carried out at th e Instit ute of Precam­ Methods brian Geology and Geochronology of the Russian Academy Oxygen and carbon isotope analyses were carried out at the of Sciences (St. Petersburg ) as specified in detail in Gorokhov Scottish Universities Environment al Research Centre using et al. (1995). Prior to Rb-Sr isotope analysis, all t he samples the pho sphoric acid method of McCrea (1950) as modified by were tr eated by 1N NH40Ac to remove loosely bou nd chem­ Rosenbaum & Sheppard (1986) for operatio n at 100 "C.Car- ical elements from the silicate components of th e rock. The NGU-BULL436, 2000 - PAGE 162 V/UOR A.M ELEZ H/K, TOMHELDAL, DAV/D ROBERTS, /GORM. GOROKHO V s ANTHONY E. FALLlCK

Tab le 1. Carbo n, oxyge n isoto pe and elem ental composition of marbles from the Fauske conglomerate s.

Sample Lithology No. wt%

Uppermost conglomerate, Bed 25 An1 White dolostone, pebble 9.50 0.68 0.78 0.037 18.37 29.79 0.213 0,01 5 0.05 12.00 166 0.52 0.70 0.5 20.9 An2 Whitedolostone, pebble 7.11 0.39 0.49 0.01 9 19.1 6 30.62 0.120 0.021 0.06 12.30 171 0.53 0.95 0.3 21.5 An3 White dolostone, pebble 9.93 0.56 0.57 0.026 18.50 29.66 0.177 0.010 0.04 11.90 172 0.53 0.45 0.2 20.8 An4 White dolostone withpink 22.75 1.00 1.05 0.035 15.99 25.48 0.289 0.018 0.03 10.00 144 0.53 0.96 0.6 21.2 stripes, pebble An5 Pinkcalcite marble,S cm- 5.81 0.56 0.33 0.031 4.26 49.23 0.184 0.013 0.07 11.90 342 0.07 0.29 0.03 22.4 thicklayer An6 Pink, banded calcite mar­ 6.94 0.76 0.51 0.048 4.64 46.82 0.16 0.258 0.01 5 0.06 11.60 328 0.08 035 0.2 22.3 ble, cobble An 7 Pa lecalcite marble,pebble 1.50 0.15 0.14 0.009 0.50 55.13 0.011 0.005 0.09 12.30 478 0.01 0.08 0.6 22.4 An8 Pa lecalcite marble,pebble 0.97 0.11 0.004 2.26 54.10 0.011 0.005 0.08 12.30 479 0.04 0.08 -0.2 22.4 with pinkrim An9 Pinkcalcite marble,6cm­ 3.02 0.26 0.27 0.022 1.56 53.25 0.091 0.007 0.08 12.20 380 0.02 0.14 -0.06 22.1 thick layer An 15a Greywacke 52.02 11.10 5.47 0.81 4.99 11.80 0.15 1.88 0.06 0.22 2.70 216 n.d. n.d. An16a Greywacke 44.75 10.39 5.56 0.82 4.54 15.90 1.42 0.07 0.24 3.70 298 n.d. n.d.

Mass-flow Iithofacies, Beds 3-5 An1 1 White,coarse-grained, cal- 0.52 0.02 0.43 55.92 0.004 0.08 12.40 391 0.01 0.08 -0.5 -20.6 cite marbl e, large cobble An12 Light, medium-grained 4.83 0.27 0.1 2 0.023 1.41 52.63 0.046 0.006 0.08 12.00 363 0.02 0.13 -1.2 22.1 calcite marble, matrixfor An11 EX13 Pinkcalcite mar ble, 7cm- 2.44 0.56 0.30 0.043 3.47 50.44 0.095 0.022 0.10 12.94 175 0.06 0.97 0.6 20.8 thick layer EX16 Whitecalcite marble,thin 0.64 0.06 0.03 0.007 0.65 54.93 0.013 0.006 0.11 13.07 426 0.01 0.11 -0.6 22.2 outerrim ofcobbleofblue calcite marble EX17 Whitedolostone, pebble 1.74 0.04 0.13 20.26 32.09 0.008 0.007 0.06 13.95 172 0.53 0.31 -0.4 21.6 EX1 8c Pinkcalcitemarble, coreof 0.34 0.1 2 0.09 0.008 0.79 55.14 0.24 0.015 0.010 0.11 13.18 295 0.01 0.26 -0.2 20.9 pebble EX1 8r Pinkcalcite marble, rim of 1.12 0.44 0.21 0.032 2.08 53.1 6 0.19 0.108 0.026 0.10 13.04 227 0.03 0.88 -0.1 21.5 pebble

'Blue' marbles, Bed 2

An13 'Blue' calci te marble, cob- 1.69 0.18 0.15 0.021 2.98 52.33 0.044 0.005 0.06 12.40 467 0.05 0.08 -1.9 22.8 ble

An14 Pale calcite marble, peb- 6.1 9 1.09 0.79 0.11 7 6.36 46.48 0.277 0.028 0.07 11.80 200 0.1 2 1.08 -0.4 223 ble

An1 5 'Blue' calcite marble, 1.97 0.28 0.15 0.024 2.99 52.80 - 0.068 0.008 0.08 12.30 483 0.05 0.13 -0.8 22.9 matrixwith small frag- ments

An 16 Greycalci te marble, 1.01 0.06 0.05 0.009 3.40 53.06 - 0.030 0.002 0.07 12.40 374 0.05 0.04 -0.7 22.1 matrix

EX12 'Blue'calcite marble, 5.38 0.25 0.14 0.020 2.72 50.75 0.11 0.057 0.005 0.09 12.60 376 0.05 0.10 -0.6 223 matrixfrom 1m-thicklayer

EX15 'Blue' calcite marble, cob- 0.80 0.05 0.02 0.005 0.67 54.74 - 0.008 0.005 0.10 13.09 422 0.01 0.09 -0.7 223 ble

Local 'basement' for conglomerates

EX14 Whitedolomite marble 0.17 0.09 0.14 23.15 30.55 0.022 0.006 0.06 14.26 88 0.64 0.53 n.d. n.d.

An10 Whitedolomite marble 1.30 0.80 0.31 0.049 21.61 31.52 0.11 6 0.006 0.06 13.1 0 11 9 0.58 0.39 0.06 21.6

'Dashes' - be low detection limits: 0.1% for AI20 3, and Na20; 0.02% for S; 0.003% for K20 ; 0.004% for Ti0 2. 'n.d.' - not determined. VICTOR A.MELEZHIK, TOM HELDAL, DAVID ROBERTS, NGU-BULL 436, 2000 - PAGE 163 IGORM. GOROKHOV& ANTHONY E.FALLlCK

Rb and Sr concentra ti ons we re determined by isoto pe dilu­ been devised. Hudson (1977) fo und th at oxyge n isotopes tion . The Rb isotopic composition was measured on a MI may be a sensiti ve indica tor of diagenetic alterati on. Diagen­ 1320 mass spect rometer. Strontium isotope analyses were esis and metamorphism commonly cause a decrease in 8180 carried out in stat ic mode on a Finnigan MAT-261 mass spec­ values and th e alte ration effe ct can be revealed by a 8' 3C and trometer. All 87 Sr/ 86Srratio s we re norm alised to a 86Sr/88Sr of 8180 cross-pl ot . Oxygen isotopes are commo nly much more 0.1194. During th e course of th e st udy th e valu e obtained for easily affected by exchangeable oxyge n derived from either the 87Sr/ 86Sr rati o of the NBS SRM-987 standard average d meteor ic water or interstit ial fluids at elevated temperatures 13C 0.710238±0.000012 (10 mean, n=2). (e.g., Fairchild et al. 1990) whereas 8 may be buffered by The major and trace elements we re analysed by X-ray flu­ pre-existing carbonate. In general, depletion in bo th oxygen orescence spect romet ry at NGU using a Philip s PW 1480 X­ and carbon isotope values may be considerable du ring late ray spectrometer. The accuracy (1o) is typically around 2% of diagene sis as well as in th e course of low-grade metamor­ the oxide present (Si0 2, AIP3' MgO, CaO), even at the level phi sm accompanied by deformation (Guerrera et al. 1997). In of0.05 wt %, and th e precision is almo st inv ariably better th an t he stu died case no significant covariation has been th e accuracy. observed between oxyge n and carbon isotopes . However, t he covariations between 8180 and Mg/Ca, and 813C and Mg/ Data Ca obse rved in the pink marbles can be attributed to th e Twenty-four samples represent ing carbonate c1 asts, matr ix do lomitisation. Thus, we suggest that slight ly elevated 813C and th e immediate local 'basement' rocks (white dolomite and 8180 values in some pink marbles were caused by diage­ marble) we re coll ected from th e quarry. The complete sam­ neti c dolomitising fluids. The least alte red sample is charac­ ple collection was analysed for major and trace elements, terised by 813C and 8180 values of- 0.2%0and 20.9%0, respec­ twenty-three for oxygen and carbon isotopes, and nine sam­ tively. ples for strontium isotope composition (Tables 1 and 2). The Mn/Sr rat io may serve as a tool to discri mi nate The 0 and C isoto pe measurements are summarised in between the altered and th e least altered samples . Fluids Figs. 17 and 18.The spread of oxygen and carbon isotop e val­ genera ted durin g th e course of diagenesis and metamor­ ues in th e data set is about 20.6-22.9.0%0and -1.9 to +0.6%0, phism commonly introduce manganese and radio genic respectively. A 813C-8180 cross-plot reveals no statistically strontium, and decrease th e Sr content in carbo nate rocks significant covari ation between oxygen and carbon isotopes (Brand & Veizer 1980, Derry et al. 1992, Kaufman & Knoll (Fig. 17). However, all dolomite samples with one except ion 1995). Samples having a Mn/Sr rat io above 0.2 should be exhibit positive 813C values, th e pink calcite marble s all plot treated as severely altere d and must not be used for recon­ around zero, wh ereas th e 'blue' and wh it e calcite marbl es st ructi on of seawate r composi tion (e.g., Kusnetzov et al. have slight ly negative values (Fig. 17). The 'blue' marbl es are 1997). These samples wo uld normally have lost Sr and t heir characterised by th e highe st 8180 values, wh ile oth er litholo­ Rb-Sr isotope systems were disturbed. Based on the Mn/Sr gies have variable values. The pin k marbl es exhibit covaria ­ ratios the majority of th e pink marbles and, apparently, all tion between 813C and Mn/Sr (r=0.53), 8180 and Mg/Ca dolomite marbl es (Figs. 17 and 18) should be excluded from (r=0.45), 813C and Mg/Ca (r=0.56), and a negative corr elation further discu ssion. between 8180 and Mn/Sr (r=-0.56) (Fig. 17). No covariations Based on th e limitati on criterion , which includes Mn and are observed for other lithologies. No reliable difference in Sr geochemistry, a 813c vs. 8180 cross-plot and Mg/Ca ratio s, elemental conc entration and isotopic ratios has been we suggest th at t he best preserved Sr and oxygen isotope detected between the c1 asts and their matrix (Fig. 17). values for t he carbonates studied are 0.70897 and 22.9%0, The initial 87Sr/86Sr ratios in carbonate constituents range respectively (Fig. 18b, Tables 1 and 2). Both values have been between 0.70896 and 0.70946, with th e least radiogenic measured from 'blue' marb le c1 asts. As far as th e carbon iso­ value measured from the 'blue' marbl e c1 ast (Fig. 18). The tope composition isconc erned it is not clear which ofth e val­ 'blue' calcite matrix and the clasts of the same rock are seen ues reflect a primary signal. The least altered 813Ccarb value to overlap on the 87Sr/86Sr diagram (Fig. 18). for th e 'blue' marbles is -0.5%0 (Fig. 18a). However, as even non -di scriminated 813 Ccarbvalues fo r all th e c1asts and matri ­ Evaluation of diagenesis and metamorphism and ces of calcite marbles are closely clustered between -1.9 and c1ast provenance +0.6%0, we may assume th at th e sou rce rocks were isotopi­ Dolomite is gen erally considered as essentially a diagenetic cally homogeneou s and apparently represent carbonates of mineral. However, th ere is gro wing evidence th at precipita­ the same age precipitated from a norm al seawater. tion of dolomite in the Precambrian was eit her coeval with calcite, or that dolomitisation was an early diagenetic phe­ Implication for depositional age nomenon caused by waters isotopically comparable to that In general, dating of non -fossiliferous carbon ates provides of seawater (e.g. Veizer & Hoefs 1976; Veizer et al. 1992a, b). many problems regardle ss of th eir act ual age. In order to How ever, in th is study, for reasons of precaut ion, we exclude obtain an app arent deposition al age for t he FC, t he meas­ dolomite samples from exercises applied to th e reconstruc­ ured 813Ccarband Srisotopic data have been used along wit h t ion of the primary composition of seawater. 813Cca rb and 87Sr/86Sr calibration curve s. We exclude th e Several geoch em ical screening methods for providing dolostone samples from our consideration as isotopic values evidence of diagenetic and metamorphic alteration have measured for dol oston es may not reflect th e isotopic compo- NGU-BULL 436,2 000 - PAGE 164 VICTOR A.M ELEZHIK, TOM HELDAL, DA VID ROBERTS, IGOR M. GOROKHOV &ANTHONY E. FALLlCK

Table 2. Strontium isoto pe and elemental composition of marbles from th e Fauske conglom erates.

Insoluble Minerals in Sample residue Rb Sr* 87Sr/86Sr 87Sr/8 6Sr ins o lu b le No. Lithology Mg/Ca M n /S r wt% ppm ppm m easured initial** re sid u e

Uppermost conglome ra t e, Bed 25 An7 Paleca lcite marble, 1.7 0.031 481 0.01 0.08 0.70941 0.70941 Qu pebble An8 Palecalcitemarble, 1.5 0.080 484 0.04 0.08 0.70947 0.70946 n.d. pebblewith pinkrim

Mass-flow lithofacies, Beds 3-5 An11 White, coarse- 1.1 0.031 401 0.01 0.08 0.709 16 0.70916 n.d. grained,calcite mar- ble, largecobble EX13 Pink calcitemarble, 7 1.8 0.124 171 0.06 0.97 0.70944 0.70943 Qu, Ms, Ch i cm-thicklayer EX17 White dolomitemar- 1.8 0.032 168 0.53 0.31 0.70921 0.7092 1 Qu ble, pebble

' Blu e' marb les, Bed 2 An13 'Blue'calcitemarble, 2.0 0.085 475 0.05 0.08 0.70922 0.70922 QU,Ms cobble An1 6 Greycalcitemarble, 2.6 0.050 379 0.05 0.04 0.70930 0.70929 Qu, Ms matrix EX12 'Blue'ca lcitemarble, 5.5 0.323 433 0.05 0.10 0.70910 0.70908 QU,Ms matrixfrom 1m-thick layer EX15 'Blue' calcitemarble, 0.6 0.104 408 0.01 0.09 0.70897 0.70896 n.d. cobble

* Acid-soluble Sr analysed by standard isotope dilu tion and solid-source mass spectrometry.

** The initi al 87 Sr/86Sr ratios are calculated under the assumption that the age of these rocks is equ al to 520 Ma. 'n.d,' - not determined .

Abbreviations used: Ms- muscovite,Qu - qu artz, Chl - chlorite.

sit ion of co ev al seawa t er. If we treat all th e carbonat e c1 ast s as least alt ered 813Ccarb va lue of -0.5%0 to get her wi t h the 87Sr/ if th ey have derive d from carbo na te roc ks of a sim ilar age, 86Sr of 0.70916 o btain ed fo r th e clasts o f w hite calcite m ar­ then t he best-preserve d 87Sr/86Sr va lue of0.70896, w hich has bl es w o uld g ive an ap parent age w hich is ind ist inguishable been obtain ed for the clasts of 'b lue' m arb les, is co nsistent fro m th at of t he 'b lue' marbles. The pin k and pale pin k car ­ w it h ap pa re nt d ep osit ion al ag es of470-475 , 505-510 and 520 bon at es cann ot b e used for t hese exercises as even the least M a (Fig. 19). How ever, th e least alter ed 813Ccarb va lue of ­ altered Sr isotope values measured from th em (0.70944 an d 0.6%0 m atc hes on ly 520 Ma . St rict ly sp eak in g, t he recon ­ 0.709 41, respectively) are highly rad iogenic, and on the dia­ st ructe d age s sho uld relat e to the fo rm at ion of t he carbo nat e gram t hey p lo t above t he 87Sr/86Sr reference cu rve w it hin ro cks bef o re they w ere inco rporat ed into conglomerat e any ap p ropriate t im e int erval (Fig. 19). c1 asts. However, availab le da ta sug gest that th e co ng lomer­ ates are intraform ati on al, and t herefo re their ti m e of dep osi­ ti on sho u ld b e close to the ag e of car bonates from w hich Depositional model th ey formed. If t h is w as t he case, then th e obtained ag e of Wil son (1975) defined th ree types o f carbon at e pl at form mar­ 520 Ma, Early Cambrian, indicate s the lo w er limit for the gi n corresponding t o (1) ene rge t ical ly q uiet,(2) moderate appa rent dep o siti on al age of the Fau ske co ng lo m erat e. and (3) ro ug h seas. All t hr ee types of env ironment usual ly An other assum pt io n w h ich can been made is that the car­ produce tal us on a foreslo pe to th e carbonate plat form ma r­ b onat es inco rp or at ed into t he clasts w ere of differe nt age s. gin. Ho w ever, typ e 3 margin s are ch aract er ised in particular Then , the least alte red 813Ccarb and 87Sr/86Sr va lu es have t o by the develo p m ent of wi de spread g ian t talus bl ocks, d ebris be selecte d separat ely for di ff erent lit ho log ical groups of car­ flow s and t urbid it es on fo reslo pes and in deep-shelf settings bon at es rep resented by the stu d ied clasts. In t h is case, t he (Wi lso n 1975, Leeder 198 2). Although t he sedi m entol o gi cal VICTOR A. MELEZHIK, TOM HELD AL, DAVID ROBERTS, NGU-BULL 436,2000 - PAGE 165 IGOR M . GOROKHOV & ANTHONY E. FALLlC K

feat ur es of the FCs are supe rficially co nsist ent wi t h a type 3 margin, th e geological d ata do not match th is type of envi­ 0 c ) ronment as th e Fauske co ng lo m erate is only loc ally devel­ op ed . Such a local d evelopment require s th at a loc al fact or 0.1 should be involved in the formation of the conglomerates, • ro U + + + 0 breccias and debris. Moreover, th e pre sence of foreign c1asts, Cl • i.e. fragments of t he pink calcite marbles, req uires a syst em ::2: t hat could have transported such material to th e carbonate (a) 0.01 platform/ shelf margin . Based on this, w e suggest that the depositional mod el should involve (Fig. 20): (i) a loc ally devel­ ~ op ed , tecton ically un stable, carbon at e she lf margin, (ii) a ~ t emporary low ering of sea level, (iit) formation of a high­ en... ~'" c: ~o relief, sho re-t o-basi n fault scar p, fo llowed by (iv) th e develop­ ::2: - ~ ------~ ment of a channel w it h (v) subseq ue nt, long-distance tr ans­ 0.1 ~. + port of c1asts of pink carbonates f ro m th e contin en t-b asin ~+ •• margin, w hich we re (vi) redeposited t og ether with a car bo n­ + (d) ate debris (w hite dolomite and 'b lue' calcite ma rb les) on the 20 (g (g t ecto nically fragmenting edge of a shallow ing carbonate ~ 0 N gj ~ 0 N gj .....0 8..... 8...... 8...... 0 8..... 8...... 8..... shelf. 6 6 6 6 6 6 6 6 6 6 A hig h-relief fault scarp appa rent ly played an important 87Sr/86Sr 87Sr/86Sr ro le both in exposing previously deposited carbonat es Key (w hit e dolomite and 'blue' calcite carbonate rocks) and in the Glast development of a channel. The latter is cons id ered as an ~ White calcite marble o Pink calcitemarble essential feature fo r transport ation of th e rela t ive ly far-trav­ elled (from th e shoreli ne?) c1 asts of pink carb on at es. • Pale calcite marble + 'Blue' calcite marble o White dolomite marble 'Blue' calcitemarble, Matrix Depositional model and its application • the leastaltered sample + 'Blue' calcite marble for exploitation and exploration Fig. 18. Cross-plots showing 87S r/86S r ratios in different c1 ast lithologies The depositional model has several implications. First of all, and matrix.Sa mplesin the shaded area areconsidered to have beensub­ th e data obtained may be used to qua ntify th e commerc ial jected to alteration, i.e., with a Mn/Sr ratio> 0.2. Arrows indicate altera­ quality ofthe marbles in the quarry. Thi s ap plies espe cially for tion trend. the pink and w hite cong lomero-brecc ias, w hich are clearly

o.reso l····..·..·······...·· 813 Ccarb, average spread 0.7085 m +8 0.7080 -co I +4 0 ~ 0.7075 U 0 M 0.7070 t-O ·4 0.7065 0.7060 7055 0. 1.,,,,' t~lt---.----.---.------.--~.----.----~----,-----,---.----.-~.------.--~----,---,--,--,--,--,--r-r-,.---,= Ma 400 450 500 550 600 650 700 750 800 850

~L--_.l..--_o C .l..-- Neoproterozoi c _

The least altered strontium isotope value from Fauske conglomerate The least altered carbon isotope value f rom Fauske conglomerate

Fig. 19. Apparent depositional ageof the Fauske conglomerates(indicated by black arro w). The Sr- and C-isotope calibration curvesare based on data from Veizeret al. (1983), Asmeron et al.(1991), Derry et al.(1992, 1993), Gorokhov et al.(199S), Kaufman & Knoll (1995) and Azmy et al. (1998). NGU -BULL 436.2000 - PAGE 166 VIGOR A. MELEZHIK, TOM HELDAL, DAVID ROBERTS, IGORM. GOROKHOV& ANTHONY E. FALLlCK

Fig. 20. Model for the depositional environments of the different facies of th e Fauske cong lom erates. VICTORA. M ELEZHIK, TOM HELDAL, DAVID ROBERTS, NGU-BU LL 436,2000 - PAGE 167 IGOR M. GOROKHOVs ANTHONY E.FALLlCK th e most attractive commercia l types and the basis for the Early Cambr ian age; and a special att ention shou ld be paid to com mercial value of th e deposit. To be of any value at all, th e the upper contacts of dolomite units wit h irregul ar surfaces conglomero-breccia beds should have at least a 0.5 m thick­ indicating syndepositional faulting and fragmentation. nessof uniform marble . Asshown above, there are significant lateral thickness variations of th e individual beds and, in actual fact, all exploitab le bedsare show n to thin out laterally Conclusions within the quarry area.Consequentl y, the com mercial part of The Fauske cong lomerate represents a rather rare case of a the deposit occurs as a limited number of lenticular beds monomict carbonate conglomerate in the Late Neoprotero­ onla pping each other, and separated by non-commercial zoic to Silurian, lithos tratigraphic successions of the Norwe­ beds.The vast majority oftrading blockshave in th e past, and gian Caledo nides. Lithological varieties of th is conglomerate wi ll in the futu re, come from the lower, thick, conglomero­ unit from the Levqavlen quarry have a highl y decorative breccia beds of the second lithofacies, mainly Beds8-11, 12, quality and are well known in both domestic and interna ­ 14 and 15. For the future, Bed 25 may represent an additional tional markets under trading names such as 'Norwegian pote ntial resource, altho ugh the size of the c1asts are gener­ Rose', 'Jaune Rose', 'Norwegian Green', 'Antique Fence' and ally larger than in th e currently exploited beds. 'Hermelin'. In addition to the th ickness variations, th e marble pro­ The Fauske conglo merate rests on dark grey ('b lue') cal­ duction is sensitive to the variations of quality within the cite marb les and white dolomite marbles. The latter are beds. The pricing of marble depends tota lly on customer jointed and fragmented, and also appear as sedimentary col­ tastes, and in th e caseof th e Fauske quarry th ese tastes have lapse-breccia and debris where th ey are in direct contact developed towards th e conglomerate sub-facies with small, with the conglomerate. Alth ough th e Fauske conglomerate sorted pebblesas th e prime quality material. These types are has been invo lved in two main pulsesof Caledonian tectonic essentially found in distal (thin) parts of the beds and in the deformation, the overall sedimentary features are still upper part of upward-finin g beds.The pink conglomero-bre­ remarkably well preserved. ccias with large, sorted pebbl es are considered to be some­ The Fauske conglom erate is a 60 m-thick unit consisting what lessatt ractive in th e market than th e small-peb ble con­ of 25 beds which are from 3 to 5 metresth ick.The unit is com­ glomerate, but still of considerable interest. Coarse, poorly posed of landslide, carbonate debris and carbonate breccia­ sorted breccia (such as Bed 25) is, at the present time, not of cong lomero-breccias - greywacke lithofacies. An upward fin­ any commercial value, but it might be used in th e future asa ing of th e clasts is followed by th e gradual development of separate sorting. The pricing of blocks is also dependent on calcareous greywacke layers which show both cross beddi ng th e compositio n of the matrix . A pure carbonate matrix is and channelli ng. Blocks, fragments, cob bles, pebb les and preferable, whilst the value dro ps significantly and propor­ smaller c1asts are mainly of white dolostone and pink, beige, tio nally with an increasein volume of dark silicate minera ls.In white and 'blue' calcite marbles. The matrix has a similar general, the commercial value of th e FC s is str ongly linked to range in lith ology with variable amo unts of quartz, fuchsite, even minor variations in lith ofaciesand depositional environ­ sericite, muscovite and chlorite. ment. Therefore, th e depositional model wi ll clearly contrib­ Both matri x and pebbles show a similar range in isotopic ute to our further understanding of such variations, and th us values: -1.9 to +0.6%0 (vs. V-PDB) for 1) 13Ccarb and 0.70896 to help in th e estimation of th e future reserves within th e 0.70946 for 87Sr/86Sr.The least altered 87 Sr/86Sr (0.70897) iso­ deposit. topic value plotted on th e calibration curve is consistent with Anoth er app licatio n of th e model is th at of a prospecting apparent deposit ional ages of 470-47 5, 505- 510 and 520 Ma philosophy for deposits of similar quality. Two major compo­ 520 Ma, whe reas th e least altered 1)13Ccarb (-0.6%0) value nents, namely pink and white marbles, make the FCs com­ matches only 520 Ma. mercially att racti ve. These two compo nents derive from two The conglomerates were deposited on a tecto nically different sources.The white do lomite marblesare from a very unstable carbon ate shelf margin .Clast of white do lomite and local source, whereas the pink marbles were transported 'blue' calcite marbles were locally derived. Clasts of pink car­ from an unknown distant source. Moreover, for a commer­ bonates were transported from the continent - basin margin cially attractive rock, th e amou nt of ot her foreign c1asts must to the shelf margin through th e channel formed by a high ­ be very limited.Thiscombinatio n of factors highlights several relief, shore-to- basin fault sca rp. Both local and foreign clasts strict limitations on depositiona l environmen ts: (l) a Fauske­ were locally redeposited together with a carbo nate deb ris type cong lomerate may only form on the relative ly steep (white dolomite and 'blue' calcite marbles) on the tectoni­ slope of a carbonate shelf;(2) a direct contact with whi te do l­ cally fragmenti ng edge of a carbonate shelf. om ite is essential; (3) a high-relief fault scarp is considered to The depositional model may by used to quant ify th e com­ play an important role both in exposing and fragm enting mercial quality of the marbles in the quarry. A search for new white dolomite and in the develop ment of a channe l; (4) the Fauske-type deposit s should be areally lim ited to th e devel­ channel is an essential feature for transportation of far-trav­ opment of relati vely thick units of white dolomite marbles of elled clastsof pink carbonates.Thus, we suggest that a search Early Cambrian age with an upper contact marked by irregu­ for new deposits should be areally limited to the develop­ lar surfaces indicatin g syndepositional faulting and fragmen­ ment of relatively th ick units of white dolomite marbles of tation. NGU-BULL 436, 2000 - PAGE 168 vicrc« A. MELEZHIK, TOM HELDAL, DAVID ROBERTS, IGORM. GOROKHOV s ANTHONYE.FALLlCK

Acknowledgements Kaufman , AJ ., Knoll, A.H. & Awrami , S.M. 1992: Biostratigraphic and che­ Access to rnininq property and the core material of the Ankerske N S is mos tratigra ph ic correlation of eoproterozoic sedimentary succes­ acknowledged wi th thanks. The field and laboratory work has been sup' sions: Upper Tindir Group, nor thwestern Canada, as a test case. Geol­ ported by th e Geological Survey of Norway, Project 270509 . The carbon, ogy20, 181-185. oxygen and strontium isotope analyses were carried out at and partly Kollung, S. & Gustavson, M. 1995: Berggrunns kart ROGNAN 2129 Ill, M supported by the Scottish Universi ties Environmental Research Centre, 1:50 000. Norgesgeologiske undetsokelse. Glasgow, Scotland, and by the Institute of Precambrian Geology & Geo­ Kulling , O. 1972: The Swedish Caledonides. In Strand, T. & Kulling. O. chronology, St. Petersburg, Russia (Grant 99-05-65181) . Leif Furuhaug (eds.) Scandinavian Caledonides. Wiley Interscience, New York, 147­ partly assisted w ith drawings. We appreciate the critical reading of th e 285. manuscript and suggested improvements by the referees, Knut Bjor­ Kuznetsov, A.B., Goro khov, I.M., Semikha tov, Mel'n ikov ,. .&Kozlov,V.1. Iykke and Robin Nicholson. 1997: Stront ium isotope composition in limestones of the Inzer For­ mat ion, Upper Riphean type section, Southern Urals. Transaction of References the Russian Academy ofSciences, Section Geochemistry 353,319-324. Leeder , M.R. 1982: Sedimentology. Process and Product. George Alien & Asmeron, Y., Jacobsen, S.B. Knoll, A.H., Butterfield, NJ . & Swett, K. 1991: Unwin, London, 344 pp . Strontium isotopic variation s of eoproterozoic seawater : Irnplica ­ McCrea, J.M. 1950: On the isotopic chem istry of carbonates and a paleo­ tions for crustal evolut ion . Geochimica et Cosmochimica Acta SS, temperatu re scale. Journal ofChemical Physics 18, 849-857. 2883-2894. Melezhik, V.A, Roberts, D., Pokrovsky , B.G., Gorokhov, I.M. & Ovchinn ik­ Azmy, K., Veizer, J., Bassett, M.G.& Cooper, P. 1998. Oxygen and carb on ova G.v. 1997: Primary isoto pic features in metamorphosed Caledo­ isotopic composition of Silurian brach iopods: Implication for coeval nian carb onates: impli cations for depositional age. (Extended seawater and glaciation. Geological Society of America Bulletin I /O, abstract). Norgesgeologiske undersokelseBulletin 433,22-23. 1499-1512. Nicho lson, R. 1974:The Scand inavian Caledonides. In Nairn, A. E. M. & Brand, U. & Veizer, J. 1980. Chem ical diagenesis of multicomponent car­ Stehli, F. G. (eds.) The Ocean Basins and Margins, Vol. 2. The North bonate system - 1. Trace elements. Journal ofSedimentary Petrology Atlantic. Plenu s Press, New York, London, 161-203. 50, 1219-1250. Nicholson, R. & Rutland, R. W. R. 1969: A section across the orweg ian Derry, L.A., Kaufman, AJ. & Jacobsen, S.B.1992: Sedimentary cycling and Caledon ides; Bodo to Sulitje lma. Norgesgeologis eunderso else260, environment al chang es in the Late Proterozoic: evide nce from sta­ 86 pp . ble and radiogenic isoto pes. Geochimica et Cosmochimica Acta 56, ystuen. J. P. 1989: Rules and recommendations for nam ing geo log ical 1379-1329. un its in Norway. Norsk Geologisk Tidsskriit 69, Supplement 2, 111 pp . Fairch ild, I.J., Marshall , J.D. Bertrand-Sarafat i, J. 1990: Strat igraphic & Robert s, D., Gje lle, S. & Solli, A. 1998: Tektonostratigrafiske enheter i den shifts in carbon isotopes from Proterozoic stromatolit ic carbonates kaled onske fjellkjeden. Nordl and fylk e. (Digitised map). Norgesgeol­ (Mauritania): Influences of primary miner alogy and diagenesis. ogiske undersokelse. American Journal ofScience 290-A, 46-79. Robert s, D. & Gee, D. 1985: An introduction to the struc ture of the Scan­ Gee, D.G., Kumpulainen , R., Roberts, D., Stephens, M.B., Thon , A. & dinavian Caledonides. ln Gee, D.G. & Sturt, BA (eds.):TheCaledonide Zachr isson, E. 1985: Scandinavian Caledonides, Tectonostrat i­ Orogen - Scandinavia and Related Areas. John Wiley & Sons Ltd., graphic map, 1:2 million . In Gee, D. G. & Sturt, B. A. (eds.) TheCaledo­ Chichester, 55-68. nide orogen - Scandinavia and related areas. John Wiley & Sons Ltd ., Rosenbaum, J. M. & Sheppard, S.M.F. 1986: An isotopic study of sider ites, Chichester , England . dolomites and ankerites at high temperatures. Geochimica et Cos­ Gorokhov, I.M., Semikhatov, MA, Baskakov, A.B.,Kutyavin, E.P., mochimica Acta 50,1147 -1159. Mel 'n ikov , N.N., Sochava, AV. & Turchenko, T.L. 1995: Strontium iso­ Rut land, R.W. R.& Nicholson, R. 1965: Tectonics of the Caledon ides of tope composit ion in Riphean, Vend ian and Lower Cambrian carbo n­ part of Nordland , Norway, Quarterly Journal of the Geological Society ates. Stratigraph y and Geological Correlation 3, 3-33. ofLondon /2/, 73-109. 18 Guerrera, A., Peacock, S.M. & Knauth, L.P. 1997: Large 0 and 13C deple­ Strand, T. 1972: The Norwegian Caledonides. ln Strand , T. & Kulli ng, O. tion in greenschist facies carbonate rocks, western Arizona . Geology (ed s.). Scandinavian Caledonides. Wiley Interscience, ew York, 1­ 25, 943-946. 145. Gustavson ,M. 1996: Geologisk kart over Norge. Berggrunnskart 16 12 Veizer, J. & Hoefs, J., 1976: The nature of 0 /180 and 13(f C secular SULlTJELMA, M 1:250 000. Norgesgeologiske undersokelse. trends in sedimentary carbona te rocks. Geochimica et Cosmochimica Gustavson , M., Cooper, M. A., Kollung, S. & Tragh eim, D. G. 1995: Fauske Acta 40, 1387-1395. 21291V. Berggrunnskart M 1:50 000. Forelopig utgave. Norgesqeoio­ Veizer, J., Clayton, R.N. & Hint on, RW . 1992a: Geochemistry of Precam­ giskeundersokelse. brian carbon ates: IV. Early Paleop rot erozoic (2.25 ± 0.25 Ga) seawa­ Gustavson , M., Cooper , M. A., Kollung, S. &Traghe im , D. G. 1999: Bergg ­ ter, Geochimica et Cosmochimica Acta 56, 875-885. runnskart Fauske 2129 IV, M 1:50 000. Norges geologiske under­ Veizer, J., Plumb , K.A., Clayton , R.N., Hinton, RW. & Grotzinger, J.P. 1992b: sokelse. Geochemistry of Precambrian carbonates: V. Late Paleoproterozoic Heldal, T. 1996: Geolog isk un dersokel se av Lov gavlen marmorbrudd , seawater (1.8±0.25 Ga). Geochimica et Cosmochimica Acta 56, 2487­ Fauske. Norgesgeologiske undersoketseRapport 96.022, 36 pp. 2501. Hudson, J.D. 1977: Stable isotopes and limeston e lithifi cati on. Journal of Veizer, J., Compston, W., C1auer, N. & Schidlowski, M. 1983: 87Sr/86Sr in the Geological Society of London 133,637-660. Late Protero zoic carbona tes: evidence for a 'mant le' event at - 900 Kaufman , AJ . & Knoll, A.H. 1995: Neoproterozoic variat ions in the Cv iso­ Ma ago. Geochimica et Cosmochimica Acta 47,295-302. topic composit ion of seawater: stratigraphic and biogeochemical Vogt , T. 1927: Sulitj elmafeltets geologi og petrografi. Norges geologiske implicati ons. Precambrian Research 73, 27-49. undersokelse 12/, 560 pp . Kaufman , AJ ., Jacobsen, S.B. & Knoll, A.H. 1993: The Vend ian record of Sr Wilson , J.L. 1975: Carbonate facies in geological history. Springer-Verlag , and C isotopic variatio ns in seawater: Impli cati ons for tec to nics and Berlin, 471 pp. paleocl imate. Earth & Planetary Science Letters /20, 409-430. Lithological cross-suction, channull, Bast facB Melezhik et al. - Plate 1 NW Srn SE

8 an -- -...... ~ ~ ~ ~

--- ? -' ~ ~ ,,- ~ ~

- ~ -

"'-,- ...... /---.J ( - ) r \

11 11L...- . ---l1 L...I ---l Basement, 'Landslide', Carbonate Carbonate white dolostone white dolostone debris breccia

@

11 I CID

Carbonate conglomerate Carbonate debris Basement Bed 5a Bed 3 Bed 12 Bed lOa Bed 7 C ha nncl of' mc di um -slze, Unsort ed, " neul"rclas ts ofW» ;\( and ro unded u ns ort ed , " neul"r clasts nsort cd cla sts of PC M, clasts of PC"I iu e ''l.'~' Banded en'~'wnl' kl' of PC"I " n d W»:\I in dark gl'l'y m a tri x and W»I\I in pink matrix I\lnssiw WDM U and pink matrix Pink calca rcnlte nnd sllty sa nds to ne o r: Bed 2 Bed 11 Bed 9 Carbonate breccia Bed 5 Symbols - IJnsortcd clas ts of PCM, blocks W»M und light PCM in WI)i\1 and light PCM in Bed 6 Blocks uud un so rt ed , "neul",' of\V»M and whitc-rlmmed white cnlcarenlte matrix white cnlcarcnite matrix Hrecciu co ns isti nj; of In"gl', clas ts of PC I\I a nd W I)I\I BC "I in pal e e '''~ ' matrix (marker layer) (ma rk er laye r) un sorted, nn guln,' clust s in dark g "l'~ ' matrix [@J Bed number o of PC"1 and WI)I\I Bed 10 Bed 8 ~ in pink matrlx Bed .. ,Landslide' Unsort ed, nn en1nr clas ts of W »M und rounded Unsort ed, nne u1nr clas ts of Unso rt ed nng ulm' clas ts of C lnst co un t sec tion clasts of I' C I\I in en'\' \V»I\I a nd rounded clnsts PC M a nd W»I\I Deta ched a nd prl zerl a nd its numbe r re ferred mat ri x; la yers of pnl'l- of PC I\I in e rl.'~ · matrix in d ark gn'~' ma tri x blocks of W »:\I t o in Fie, 15 Melezhik et al. - Plate 2 NW Uthological cross-section,channel 3,east face 5rn

SE

@

Legend

Bed 24 Bed 17 Sllty planar-lami na ted an d Bed 12 Bed 8 Bed 2e cross-bedded gr~~'",ack~ , ;\It-,lIum- tu sma ll-pebble ;\" 'dium,pl-bbll'l'u ngluml'mll-: Lar~ , un sorted , an gul a r a nd cha nne ls of cross -bedded l'ung lonll'mlt·: u nso rt ed , llllf ula r u n54111 ..1. angular clasts uf rou nded clnsts a nd blocks of carbonate gril slo n~ a nd clusts uf \\'I):\llInd round ... cla st s \\'I);\l lllld 1'(MIIIl"'" .-Iasl s GI);\llllld whi le -ri m med n CM con g lo m~m l~ of I'C;\ I in pink -grvy matri x ~ ofl'C;\1 in g r(' ~ ' malrix in gre~' ca lcite ma t rix

Car bo na te cong lomerate with Beds 22-23 Unsort ed ro unded clnsts Bed 15 lavers of'wh ltc calcarcnltc: Bed 11 Bed 7 Symbols - urisurt ed round...1clas ts Small-pebble cong lomemle: un sort ed, _ of PC \ l lllld a ng ular a nd rounded clnsts ofW I);\1 ofl'CM and a ng ular a nd ang ula l' cla sts of \\'1);\1 a nd ro und ...1 in pink , IIghl aud dark gre ~ . rounded clas ts of WI);\I clusts uf I'C;\I in whit e ca lca renitc matr i x CI;] in pin k m ntrlx mutrlx (ma rk erlaye r) o ~"SJ Dyk e Bed 6 Bed 19 Bed 14 Unsort ed rounded clas ts of Bed 10 l'o nslsti n~ Silty lumlnut ed gn-~ ·wlI l· kt·, PC;\I and an gulal' a nd i\ll-d iu m- to small-pe bble Hrec cln of' u nsorted cha nnels of'c ross-bedde d l'u ng lo m~m te: un sort ed , anorular rounded clasts ot I'CM and round...1 clasts ofWI);\1 a ng ula r Q ua rtz vein ca r bonate conglomerutc in pink mat ri x; layers of clasts uf \\'I):\1 and round... clas ts clusts ufWI):\ t gritsto n~ gl'e~ ' in pink mnt ri x ca a nd while ca lcarenlte of I'C;\I in marrix

Small-pebble carbona te [S] T h rust Bed 18 conglome m tc with laye rs of Bed 13 Bed 9 . Bed 2f l'O ng l()J ue l ~tll' : Sma ll-pc hhle l'llng lunu'mlt' silty g~~~"ac kt- , white culca renlte I Sma ll-pe bble un sorted, CJ gr-ullng inl o cnrhona te gri l slo n~ : aug ula l' clasts of \\'1);\1 and rounded with la vers uf si lh ' gl'evwal'kt·: clasts ofW I);\ 1 and I'C;\I in d a rk clnsts uf lighl of I'Ci\1 in white 11llllllll:d pchhl e»;,fW1>:\ l a nd mat rix Silty gre-yw acke ca learenite matrix (m a rk er laye r) qu artz [®~ Hed number Melezhik et al. - Plate 3 Lithological cross-sBction,channBI 2, east facB NW Ca rbonate breccia 5m SE

Carbonate conglomerates

Car bonate debris

Legend

Car bonate breccia Symbols Layer 9 Layel' 6 Layer 21' Unsort ed, sma ll an gul ar clas ts ofWDM and WDM and light PCM in Unsorted, sma ll angulat, ro unded clas ts of PCM in white ca lca renl tc matri x clasts of rCM and W DM Angula r; unsort ed d asts of gn~y and pink m at ri x .. (market' layer) in pin k and gt'l.'J' matrix G DM in pall' gl'l'y matri x Layer number Carbonate debris Conglomera te Clas t count sectio n Layer 11 Layer 8 and its number Layer 5 Layer I referred to in Fig, 15 WD M and light PCM in Unsort ed , ang ular c1asts of white cnlca renlte matrix \VDM and ro unde d c1asts Unsort ed, ro unded clasts (marke r layer) of PCM in grey matri x ofWDM an d PCM in Unsort ed, r'OIIIIIled c1 asts of r. pink matri x PC;\! in pale gre y matrix Layer 7 Layel' 2c-e Layer la Unsorted, an gula r cla sts ofWDM and rounded Carbona te gritsto ne ~~-~ Blocks and un sorted, ang ular Unso rt ed, rounded clasts clasts of r CM in grey gra ding into silty .. clasts of white-rimmed BCM ofWDM and light PCM matrix greywacke tfL-D -4 an d W DM in dark grey matrix in dar k gn.'y matri x Me lezhik et al. -Plate 4 Longitudinallithological section NE Section 4 Section 3

Section 2 Section 1 sw Section 2b \6 Section la Section I b Section 12 Section 2a

Section 11 Section 10 12

- ::.::-:-. -

2c

Srn

2 ---:-

Legend

Car bonate breccia and conglom erate Bed 16 Bed 13 Bed 10 Brec cla /:l1l1l1ng in to fine- Bed 7 Bed 2e Bed 2b Unsort ed ro unded c1asts or Fine-pe bble conelomc rn te peb ble conglome rute: La .'gl.', un sort ed , ang ular Small, un sort ed , rounded ('C\\ and an/:ular and gr.lding int o ca rbunate lIIlS0I1 l'( l , a ng ula r'dasts of c1asts and blocks orGI>M clas ts orWI>;'; I, G I>~[ and ro unded clasts orWI>~ \ in gritsto ne and laminat ed silt)' W I>;'; [ a nd rounded c1asts and IIC;';[ in dark g l"(,~' qu art z in pale /:I"cn pink and dark /: 1"(')' matr i x greywacke E;J of PCi\[ in gre)"matrix .. La m ina te d silty gn')'w;'H:k e• culcit..• m at ri x D calcite -sillciclas tic m at ri x Dyke Bed 15 Bed 12 ~ [e di u m - pe b b lc hreccia Bed 9 Bed 6 Bed 2d Bed 2a Symbols Unsort ed rounded clasts /:m di ng into sma ll-gcbbl" Small-pcbbl,' con/:lmncmtc: Brcccia : la q.~ (· , UIlSOI1 1.'d, L," '/:c, un sorted , 'lII/:ular La rge , un sort ed , all 'iu hu' or('CM and ang ular and cOlI/:lomcmt,'S wit I chan ne ls W I>1\ [ a nd II/:ht PC1\[ in ang ulal ' c1 ast s of W 1>;';[ clas ts :tI1l1 block s or GI>M clasts and blocks or ; 1>1\[ orWI>~ [ 11 111 ," I,'d clasts and beds or lam inat ed sill)' white caleurcn ltc matr i x and ro unde d ('Iasts and IICM in pale /:1" )' ;...;;:.,,-... :.:::::. " and IIC M in dark /:1"(')' in pin k matrix (ma rker laye r) ~ of PC;';[ in pin k mall'" ~§f~ ~ Bed num her gre,Ywarkc D calcltemutrlx "------ca lcite m atri x 0 Bed Bed 11 Large to small, un sort ed , Bed H M edi um -peh ble h re ccia Bed 2f i'h'llium to sm all, un sort ed , Bed 2c Bed 1 Small-pcbblc conlilomc m t',: /:l':lIl1ng int o snmll-gcbblc I,a r ge-, un sorted , a ng ula r round ed clasts or PCM WDM and light I C M ill an ~' lal ' c1 asts of(; Ul\[, Large, un so rt ed , rounded conglomcmtes wi t I BC l [ and small, ro u nded clas ts and block s or GI>l\[ and '1II11" lar clas ts or white cal carenite matrix /: I"~' clasts ofl'CM and " 'C M I }~ cha nne ls and beds of clas ts or ,)",,, 't,, ill pa le and I\ C\[ ill dark ..~ ~ W I>M m pink matr t x (mu ..kcr layer) s ilt~ ' ~ m ~l tl " i x ~ in da rk /: I "(, ~ ' mat rix lam inated /:re-ywackc gn') ' ('a l('lh' m at l"ix calcit..• Melezhik et al. - Plate 5 Longitudinallithological suction

Section 13a sw NE Section 13 24 24 Section 7 Section 6 22-23

20 19

5rn

18

Section 5

17

Legend

Bed 24 Bed 20 Bed 17 Bed 14a Fine-pebble COntlOmerate Small pebble conglomerate Greywacke sandstone with grading into car onate Silty laminated greywacke, with layers of siltyAVtrvacke: layers and channels of carbonate gritstone: rounded and angular, channels of cross-bedded rounded pebbles 0 M and small-pebble conglomerate sorted cIasts ofWDM and PCM carbonate gritstone G quartz 14a Beds 22-23 Unsorted rounded cIasts Bed 19 Bed 16 of PCM and angular and Silty laminated greywacke, Unsorted rounded cIasts of rounded cIasts of WDM channels of cross-bedded PCM and angular and carbonate conglomerate in pink, pale and dark rounded cIasts of WDM in ~ Dyke Lm grey matrix and gritstone pink and dark grey matrix Bed 21 Bed 18 Small-pebble carbonate Carbonate conglomerate, large - Bed 15 Symbols conglomerate with layers of Unsorted rounded cIasts to small unsorted, rounded silt); greywacke gradmg into of PCM and angular and cIasts ofPCM and angular cIasts car onate ~itstone: cIasts of rounded cIasts of WDM ofWDM in pink matnx WDM and CM in dark matrix in pink matrix Bed number - CJ-~ - 0