Biostratigrafija Zgornjekrednih Pelagi~Nih Apnencev Okolice Bovca V Julijskih Alpah

GEOLOGIJA 47/2, 151–177, Ljubljana 2004 doi:10.5474/geologija.2004.012

Biostratigrafija zgornjekrednih pelagi~nih apnencev okolice Bovca v Julijskih Alpah

Biostratigraphy of Late Cretaceous pelagic limestones from surroundigns of Bovec in the Julian Alps (Slovenia)

Rajka RADOI^I]1 & Stanko BUSER2 1Kralja Petra I, 38, 11000 Beograd, Srbija i Crna gora 2Oddelek za geologijo NTF, Univerza v Ljubljani, A{ker~eva 12, 1000 Ljubljana, Slovenija

Klju~ne besede: biostratigrafija, foraminifere, zgornja kreda, turonij–campanij, stratigrafski hiatus, paleogeografija, Julijske Alpe, Slovenija Key words: biostratigraphy, Foraminifera, Late Cretaceous, Turonian–Campanian, stratigraphic hiatus, paleogeography, Julian Alps, Slovenia Kratka vsebina

V zahodnem delu Julijskih Alp so na mnogih mestih ohranjeni majhni erozijski ostanki zgornjekrednih pelagi~nih svetlo sivih in rde~kastih apnencev ter laporjev (scaglia). Ti apnenci in laporji, ki vsebujejo izredno {tevilne globotrunkane, le‘ijo jugozahodno od Bovca s hiatusom na spodnjejurskem pliensbachijskem oolitnem in biosparitnem apnencu. Med obema apnencema je zna~ilna kotna diskordanca. Celokupna debelina zgornjekrednega apnenca in laporja je 8,80 m. Detajlno smo vzor~evali spodnjih 6,20 metrov profila. V komaj 6,20 m debelem profilu smo odkrili tri globotrunkanske cone: Helvetotruncana helvetica (3-5 cm), Dicarinella concavata (120 cm) in Dicarinella asymetrica (490 cm). Cona H. helvetica ni razvita v popolni debelini, ker je pod njo hiatus. Sedimentacija zgornjekrednih pelagi~nih apnencev je pri~ela v turoniju in segala navzgor v campanij. Nad obravnavanimi plastmi le‘ijo v Bov{ki kotlini campanijsko–maastrichtijske fli{ne kamnine. Abstract

In the western part of Julian Alps in many places small erosion remains of Late Cretaceous pelagic, light grey and reddish limestones and marls (scaglia) are preserved. These limestones and marls that contain very numerous globotruncanas overlie southwest of Bovec after a hiatus the Lower Jurassic Pliensbachian oolitic and biospariotic limestone. Between the two limestones appears an angular disconformity. Total thickness of the Upper Cretaceous limestone and marl is 8.80 m. The lower 6.20 m of the column were sampled in detail. In the scarcely 6.20 m thick section three globotruncana zones were established: Helvetotruncana helvetica (3-5 cm), Dicarinella concavata (120 cm) and Di- carinella asymetrica (490 cm). The H. helvetica zone is not developed in its entire thickness owing to the hiatus below. Deposition of the Late Cretaceous pelagic limestones started in Turonian and lasted into Campanian. The considered beds in Bovec basin are overlain by Campanian-Maastrichtian flysch beds. 152 Rajka Radoi~i} & Stanko Buser

Uvod plasti, ki prehajajo navzgor v zgornjesenon- ski fli{, pa je menil, da pripadajo spodnjemu Na {ir{em prostoru zahodnega dela Julij- santoniju. skih Alp, posebno {e v {ir{i okolici Bovca, se Leta 1954 (objavljeno 1957) je tudi N e - pojavljajo {tevilni majhni erozijski ostanki dela Devidé v okolici Bovca v rde~ih la- zgornjekrednih rde~ih in svetlo sivih pela- porjih ugotovila {tevilne globotrunkane gi~nih apnencev in laporjev. Ti leìjo s stra- spodnjega senona in santonija. Globotrun- tigrafskim hiatusom neposredno na oolitnem kane je na{la tudi v plo{~astih vol~anskih in biosparitnem spodnjejurskem pliensbac- apnencih pri Tolminu in je s tem prva doka- hijskem ali celo na zgornjetriasnem dach- zala, da so spodnjesenonske in ne spodnje- steinskem apnencu. kredne starosti kot so menili do takrat. Leta 1976 smo pri geolo{kih raziskavah Ku{~er in njegovi sodelavci (1974) so Kaninskega pogorja odkrili blizu kra{kega med Kobaridom in Bovcem zgornjekredne izvira Glijun jugozahodno od Bovca manj{i sedimente lo~ili na dve facialni obmo~ji. V izdanek svetlo sivega do ro`natega zgornje- okolici Bovca so te prikazali tudi na geolo- krednega pelagi~nega apnenca in laporja {ki karti v dolini Slatenika, ju`no od êzso- (scaglia), ki sta s hiatusom odloèna neposre- ~e, pri Glijunu in severno od Bovca. Izdvojili dno na spodnjejurski plitvomorski apnenec. so jih kot rde~e laporaste apnence in laporje Na podlagi predhodnih najdb globotrun- z roèncem (scaglia). V njih so na{li v Slate- kan v obravnavanih kamninah, smo leta niku globotrunkane, ki kaèjo na turonijsko 1977 posneli detajlni profil in ga vzor~evali in spodnjesenonsko starost. za dolo~itev globotrunkan v zbruskih apnen- Pri raziskavah nanoplanktona okolice cev in laporjev. Celokupna debelina na povr- Bovca je Pav{i~ (1979) v fli{u ugotovil bio- {ini odkritih plasti je 8,80 m. Detajlno smo cono Tetralithus trifidus, ki obsega najvi{ji vzor~evali spodnjih 6,20 m profila. V komaj del campanija in maastrichitija. Na podlagi 6,20 m posnetega profila so bile odkrite kar tega je sklepal, da je nastal rde~i laporasti tri globotrunske cone. Sedimentacija zgor- apnenec, ki leì pod fli{em v ~asu santonija njekrednih plasti je pri~ela v turoniju in se- do ni`jega dela zgornjega campanija. gala navzgor neprekinjeno v campanij. V tolma~u h geolo{ki karti lista Tolmin je Podatke smo dopolnjevali vse do leta Buser (1986) navedel ve~ podatkov o staro- 1998. Vendar jih zaradi razli~nih razlogov sti pela{kih rde~kastih apnencev in laporjev doslej nismo objavili. Rezultati na{ih raz- v Krnskem pogorju in iz okolice Bovca. Bli- iskav pa so po nekaj letih {e vedno pomemb- zu planine Predoline na Polovniku je na{el ni in aktualni za objavo. enake kamnine iste starosti kot jih dobimo na obravnavani lokaliteti pri Bovcu. Na geolo{ki karti lista Tolmin (Buser, Dosedanje raziskave zgornjekrednih plasti 1987) so prikazani vsi erozijski ostanki kre- v Julijskih Alpah

Pelagi~ne zgornjekredne rde~kaste apnence in laporje je na {ir{em prostoru Bovca, Krna in Kobarida v Julijskih Alpah prvi za- sledil Kossmat (1908) in jih pod imenom scaglia uvrstil v zgornji senon. Winkler (1921, 1924) je poro~al o teh plasteh iz Krn- skega pogorja in okolice Bovca, v nasprotju s Kossmatom je menil, da so jurske starosti. [ele z najdbo globotrunkan v teh kamninah v dolini So~e, jih je 1936 pri{tel spodnjemu senonu. Selli (1953) je v zgornjem delu So{ke doline opravil pionirsko delo pri detajlni raz- Sl. 1. Polo‘aj golice zgornjekrednih plasti pri iskavi globotrunkan v scaglijskih laporjih in Bovcu apnencih. Ugotovil je, da pripadajo obdobju Fig. 1. Detailed location map of the outcrop in zgornji cenomanij-coniacij. Za vrhnji del teh the Late Cretaceous beds at Bovec Biostratigrafija zgornjekrednih pelagi~nih apnencev okolice Bovca v Julijskih Alpah 153

Sl. 2. Kontakt med spodnjejurskim (J) in zgornjekrednim apnencem (K) pri Bovcu Fig. 2. Contact between Lower Jurassic (J) and Late Cretaceous limestones (K) at Bovec

dnih pela{kih plasti v ju`nem delu Julijskih Geolo{ki opis vzor~evanega profila Alp in s tem tudi v okolici Bovca. Te plasti so na raznih mestih razli~ne starosti in so uvr- Vidni hiatusni stik med plitvomorskim {~ene v obdobje turonij-campanij. spodnjejurskim biosparitnim in oolitnim ter Jurkov{ek in sodelavci (1990) so raz- zgornjekrednim pelagi~nim apnencem je vi- iskali zgornjekredne pelagi~ne plasti v raz- den na dolìni 7 metrov (sl. 2). Je neraven s voju scaglije na Mangartskem sedlu, Ple{iv- plitvim mikroreliefom v spodnjejurskem cu, îstem vrhu, v Vrsniku in Bav{ici. apnencu, ki ga nakazujejo plitvej{e vdolbi- Ve~inoma so v tektonskem stiku z ostalimi ne. V spodnjejurskem apnencu ni opaziti raz- kamninami in pripadajo senonu. Le na Ple- pok, katere bi zapolnjeval zgornjekredni {ivcu leìjo transgresivno na zgornjejursko- apnenec v obliki neptunskih dajkov. Kon- spodnjekrednem biancone apnencu. Na pod- takt med obema apnencema vpada pod ko- lagi globotrunkan pripadajo zgornjemu tom 40° proti severovzhodu. Enak vpad ima- turoniju in spodnjemu senonu. jo tudi pelagi~ni kredni apnenci (50/40). Kredne plasti vpadajo v severnem delu golice proti jugovzhodu. Tako sestavljajo te pla- Geografska lega vzor~evanega profila sti manj{o skledasto sinklinalno oziroma brahisinklinalno strukturo. Mo`no je, da je Obravnavane zgornjekredne pelagi~ne bil kredni apnenec sprva odloèn v ve~jo plasti se nahajajo na vzhodnem pobo~ju hri- paleokra{ko vrta~o v jurskem apnencu in so ba Poljanica ju`no od vasi Plu`na oziroma 3 se plo{~asti kredni apnenci zaradi kompak- km zra~ne ~rte jugozahodno od Bovca (sl. 1). cije skledasto upognili. Podoben pojav je Razkrite so ob dovodnem pokritem kanalu, Buser (1986) opisal iz Predoline na Polov- po katerem je voda speljana iz kra{kega iz- niku. Plasti spodnjejurskega apnenca, ki le- vira Glijun preko majhnega akumulacijske- ìjo pod zgornjekrednimi pela{kimi apnen- ga bazena do hidroelektrarne Plu`na. Od- ci, so vodoravne. Tako je izraèna med krite so med dvema predoroma, skozi katera apnencema razli~ne starosti jasna kotna dis- je speljan del kanala. Povr{inski izdanek ob- kordanca. Na nekaterih mestih so plasti jur- sega okoli 200 m2. Detajlni profil v zgornje- skega apnenca rahlo nagnjene proti jugo- krednih plasteh je bil posnet na ju`ni strani vzhodu in zaklju~ujejo zahodno krilo Bov{ke njihovega izdanka. sinklinale oziroma brahisinklinale. 154 Rajka Radoi~i} & Stanko Buser

Spodnjejurski svetlosivi apnenci so skla- zgornji pliensbachij (Buser & Debeljak, dnati z debelino plasti 50 do 100 cm. Vsebu- 1996). Na ve~ mestih so bile v apnencu naj- jejo {tevilne majhne megalodontide. Neda- dene alge vrste Palaeodasycladus barrabei le~ od obravnavanega profila so bile v (Buser,1986). apnencu najdene velike litiotidne {koljke vr- Ni`ji del zgornjekrednih plasti za~enja s ste Lithiotis problematica, ki jih uvr{~ajo v 4,80 m debelo skladovnico svetlo sivega do zelenkastega apnenca. [ele vi{je leì nad tem apnencem ro`nati do rde~i apnenec in lapor. Najni`ji del zgornjekrednega apnenca debe- line 75 cm, ki leì na spodnjejurskem plast- natem apnencu, je masiven, zato se makro- skopsko te`ko lo~i od jurskega apnenca. Mikroskopsko je mejo lahko dolo~iti, saj vse- buje pelagi~ni zgornjekredni apnenec ‘e v najni`jem delu prav kamnotvorne globotrunkane. V zbruskih najni`je leè~ega apnenca so vidni apnen~evi odlomki, ki ka- èjo na odna{anje s strujanjem ali podvodno plazenje na globljemorskem dnu. Ti procesi so povzro~ili horizontalno odebelitev ali izklinjanje najni`jega dela cone Helvetoglobo- truncana helvetica, ki je tukaj debela komaj 3–5 cm. Nad masivnim zgornjekrednim apnencem sledi 4,05 m svetlosivega in zelenkastega plo{~astega apnenca z debelino plasti 2 do 5 cm. Navzgor sledi okoli 4 m rde~e- ga plo{~astega lapornatega apnenca in laporja, ki postane v vrhnjem delu masiven. Meja med svetlosivim in rde~im apnencem je ostra, vendar ne predstavlja stratigrafske meje, saj se v rde~em apnencu navzgor na- daljuje cona Dicarinella asymetrica. Avtorja pri~ujo~ega ~lanka ne uporablja- va termina “scaglia”, ker je preve~ splo{en. Pelagi~ne zgornjekredne plasti opisujeva z litolo{kimi izrazi. Ime “scaglia” uporablja- va le pri citatih dosedanjih raziskovalcev in za mo`nost primerjave teh plasti s podobni- mi kamninami v sosednji Italiji. Na rde~em lapornatem apnencu in la- porju so v Bov{ki kotlini normalno odloè- ne zgornjecampanijske in maastrichtijske

Sl. 3. Stratigrafski stolpec v zgornjekrednih plasteh pri Bovcu 1 rde~i lapor, 2 rde~i plo{~asti apnenec, 3 svetlo sivi in zelenkasti plo{~asti apnenec, 4 svetlo sivi masivni apnenec, 5 debeloplastnat spodnjejurski apnenec, 6 hiatus. Fig. 3. Stratigraphic column of Late Cretaceous beds at Bovec 1 red marl, 2 red platy limestone, 3 light-grey and green platy limestone, 4 light-grey massive limestone, 5 thick-bedded Lower Jurassic limestone, 6 hiatus. Biostratigrafija zgornjekrednih pelagi~nih apnencev okolice Bovca v Julijskih Alpah 155 fli{ne plasti. Na posnetem profilu zaradi pogorju je zapolnila paleokra{ka brezna pi- pokritosti s pobo~nim gru{~em tega stika sana apnen~eva bre~a. ne vidimo. Na{li pa smo ga severno od Bov- Predeli na Mangartskem sedlu, v okolici ca in ju`no od vasi êzso~a. Lateralno se Bovca in Krnskega pogorja so ostali kot ko- lahko obravnavani zgornjekredni apnenci pne grude vse do zgornje krede oziroma in laporji izklinjajo. V tem primeru leì spodnjega turonija. Takrat so tudi te potoni- zgornjekredni fli{ s hiatusom neposredno le v globje pelagi~no morje. Na platformske na spodnjejurskem apnencu, kar smo zasle- plitvomorske spodnjeliasne ali celo zgornje- dili v potoku Slatenik jugovzhodno od êz- triasne apnence so bili s hiatusom odloèni so~e. najprej svetlo sivi pela{ki biomikritni, nato pa {e rde~i lapornati apnenci in laporji z globotrunkanami. Nekateri predeli pa so Paleogeografske razmere med spodnjo ju- ostali kopni do zgornjega campanija, ko je ro in zgornjo kredo na obmo~ju zahodne- bilo kon~no poplavljeno celotno ozemlje da- ga dela Julijskih Alp na{njih zahodnih Julijskih Alp. Zgornjekre- dne pelagi~ne plasti so verjetno pokrivale Julijska karbonatna platforma, na kateri prete`ni zahodni del Julijskih Alp. Koncem so nastali plitvomorski spodnjejurski biospa- maastrichtija so bile Ju`ne Alpe in s tem ritni in oolitni apnenci, je nastala v spodnjem tudi Julijske Alpe docela dvignjene kot ko- delu zgornjega triasa. Proti zahodu se je na- pno. Dolgotrajna erozija je odstranila ve~ji daljevala v Italiji v Trento karbonanto plat- del tako jurskih kot krednih pelagi~nih pla- formo. Ju`neje leè~i Slovenski bazen, ki je sti, ki jih dobimo danes le {e v obliki manj- lo~il na severu leè~o Julijsko od ju`neje le- {ih erozijskih krp (Jurkov{ek et al., 1990). è~e Dinarske karbonatne platforme, se je pri Podobne pelagi~ne rde~e lapornate Srpenici v dolini So~e izklinil. Po mnenju apnence in laporje (scaglia) z globotrunka- Buserja (1996) je koncem pliensbachija na- nami dobimo {e mnogo ju`neje v osrednji stopila faza intenzivnega razlamljanja kar- Sloveniji in sicer v Gori{kih Brdih, na Banj- bonatne platforme, ki je razpadla na ve~je {icah, Colu, pod Nanosom, pri Studenem, na grude. [muc (2004) meni, da se je to dogo- Kalcah pri Logatcu, Hinjah, Starem Bregu dilo ‘e v spodnjem pliensbachiju. Grude so in Riglju. Te apnence in laporje sta D r obne se ve~inoma dvignile kot kopno. Na dvignje- in Pavlovec (1969) imenovala po vasi Pod- nih grudah je pri~el jurski apnenec zakrase- sabotin v Gori{kih Brdih podsabotinske pla- vati. Ob tem je bil del jurskih apnencev ko- sti. Vendar so te plasti mlaj{e od onih, ki jih rodiran oziroma erodiran. Ponekod je erozija obravnavamo v pri~ujo~em ~lanku iz okoli- segla celo do dachsteinskega apnenca. V ce Bovca. Pripadajo namre~ vrhnjemu delu Krnskem pogorju so nastala v jurskem in zgornje krede in segajo navzgor {e v spodnji zgornjetriasnem apnencu velika paleokra- del terciarja oziroma v paleocen. Da bi mo- {ka brezna. Na Kaninskem pogorju pa dobi- gli razlikovati podsabotinske plasti, ki so mo ve~ sto metrov dolge odprte prelomne mlaj{e in delno druga~ne litolo{ke sestave razpoke, ki so bile kasneje zapolnjene s pe- od plasti, ki jih obravnavamo v pri~ujo~em lagi~nim krinoidnim jurskim apnencem s ~lanku iz okolice Bovca, predlagamo, da po- {tevilnimi brahiopodi. [muc (2004) poro~a, imenujemo te pelagi~ne sive in rde~e zgor- da so se apnen~eve grude na obmo~ju Man- njekredne apnence ter laporje v Julijskih Al- garta (Travni{ka strukturna enota) v spod- pah po Bovcu kot bov{ke plasti. njem pliensbachiju pogreznile najgloblje in na njih so pri~eli nastajati pelagi~ni sedimenti. Ostali ve~ji predel dana{njega zaho- Biostratigrafija zgornjekrednih plasti v dnega dela Julijskih Alp, to je obmo~je Man- posnetem profilu gartskega sedla, Triglavskih jezer, Krnskega pogorja in Bovca naj bi se pogreznil kot pod- Globotrunkane so v vseh vzorcih izredno morska planota {ele v bathoniju. Na njem so pogostne, vendar v nekaterih primerih slabo bili na spodnjejurskem ali celo dachstein- ohranjene in te`ko dolo~ljive. V profilu so skem apnencu odloèni kondenzirani apnen- bile v debelini 6,20 metrov ugotovljene na- ci tipa ammonitico rosso, ki v ni`jem delu slednje PF cone (cone planktonskih forami- vsebujejo manganove gomolje. V Krnskem nifer): 156 Rajka Radoi~i} & Stanko Buser

Cona (Zone): Helvetoglobotruncana hel- Marginotruncana renzi (Gandolfi) vetica Marginotruncana schneegansi (Sigal) Debelina (Thickness): 3–5 cm; Vzorec Marginotruncana sigali (Reichel) (Sample): 1 Marginotruncana sinuosa Porthault Tabla 1 (Plate 1) Marginotruncana tarfayaensis (Lehmann) Zdru`ba (Assemblage): Marginotruncana undulata (Lehmann) Marginotruncana spp. Dicarinella algeriana (Caron) Whiteinella spp. Dicarinella hagni (Scheibnerova) Pogost droben plankton, {e posebej Cal- Dicarinella imbricata (Mornod) cisphaerulidae, mestoma pravi »Pithonella« Dicarinella sp. apnenec, zelo redki fragmenti rodu Saccoco- Globotrunkanida (Globotruncanid) aff. ma. (Abundance of minute planctonics, espe- Falsotruncana maslakovae Caron cially Calcisphaerulidae, here and there true Helvetoglobotruncana helvetica (Bolli) »Pithonella« limestone, very rare Saccoco- Marginotruncana cf. M. sigali (Reichel) ma fragments.) Marginotruncana schneegansi (Sigal) Marginotruncana sp. Cona (Zone): Dicarinella asymetrica Praeglobotruncana gibba Klaus Debelina (Thickness): 490 cm; Vzorci Praeglobotruncana stephani (Gandolfi) (Samples): 9–17 Whiteinella cf. W. aumalensis (Sigal) Table 8–10 (Plates 8–10) Whiteinella praehelvetica (Trujillo) Zdru`be (Assemblages): Pogost droben plankton (Abundance of minute planctonics): Whiteinella-Hedbergel- Contusotruncana fornicata (Plummer) la, Calcisphaerulidae. Contusotruncana sp. Dicarinella asymetrica (Sigal) Cona (Zone): Dicarinella concavata Dicarinella cf. D. canaliculata (Reuss) Debelina (Thickness): 120 cm; Vzorci Dicarinella concavata (Brotzen) (Samples): 2–8 Dicarinella aff. D. concavata (Brotzen) Table 2–7 (Plates 2–7) Dicarinella imbricata (Mornod) Zdru`be (Assemblages): Dicarinella? sp. Globotruncana arca (Cushman), zelo red- Contusotruncana fornicata (Plummer) ka (very rare) Contusotruncana cf. C. fornicata (Plum- Globotruncana bulloides Vogler, zelo red- mer) ka (very rare) Dicarinella canaliculata (Reuss) Globotruncana hilli Pessagno Dicarinella cf. D. canaliculata (Reuss) Globotruncana aff. G. hilli Pessagno Dicarinella concavata (Brotzen) Globotruncana leupoldi Bolli Dicarinella aff. D. concavata (Brotzen) Globotruncana linneiana (d’Orbigny) in Dicarinella hagni (Scheibnerova) (and) “gr. linnneiana” Dicarinella imbricata (Mornod) Globotruncana sp. aff. G. orientalis El Dicarinella primitiva (Dalbiez) Naggar Dicarinella sp. Globotruncana spp. Globotruncana cf. G. bulloides Vogler Globotruncanita elevata (Brotzen) Globotruncana hilli Pessagno Globotruncanita stuartiformis (Dalbiez), Globotruncana aff. G. hilli Pessagno zelo redka (very rare) Globotruncana linneiana (d’Orbigny) in Marginotruncana coronata (Bolli) (and) “gr. linnneiana” Marginotruncana marginata (Reuss) Globotruncana spp. Marginotruncana paraconcavata Portha- Helvetoglobotruncana? sp. ult Marginotruncana coronata (Bolli) Marginotruncana pseudolinneiana Pessa- Marginotruncana marginata (Reuss) gno Marginotruncana paraconcavata Portha- Marginotruncana renzi (Gandolfi) ult Marginotruncana schneegansi (Sigal) Marginotruncana pseudolinneiana Pessa- Marginotruncana sigali (Reichel) gno Marginotruncana sinuosa Porthault Biostratigrafija zgornjekrednih pelagi~nih apnencev okolice Bovca v Julijskih Alpah 157

Sl. 4. Razli~na pogostnost planktonskih foraminifer v primarnem apnencu in litoklastu. Fig. 4. Different frequency of planktonic framinifers in the primary limestone and in the lithoclast.

Marginotruncana undulata (Lehmann) vladujejo velike marginotrunkanide (coro- Rugotruncana? sp. (le v vzorcu 17; only in nata, undulata, sinuosa, tarfayaensis). ?Mar- the sample 17) ginotruncana sigali in Marginotruncana Globigerinelloides, Gublerina, Sigalia, schneegansi sta prav tako zelo pogosti. Po Heterohelix, Whiteinella, Cercidina supra- temu sode~, kaèjo te zdru`be ve~jo podob- cretacea Vogler, Saccocoma. nost s cono Marginotruncana sigali kot s cono Dicarinella concavata iz profila Bot- 3–5 cm debela plast z vrsto Helvetoglobo- taccione (P r emoli-Silva & Sliter, 1994, truncana helvetica, ki smo jo opazili v profilu 12). Samo en primerek vrste Dicarinella con- jugozahodno od Bovca in ki leì nad apnenci cavata je bil v profilu najden v najni`jem s paleodazikladusi, se bo~no izklinja (pod- delu 60 cm debele plasti, pribli`no 10 cm morska erozija). H. helvetica, ki ozna~uje co- nad plastjo z vrsto Helvetoglobotruncana no, je pogosta. Hkratna prisotnost vrste Whi- helvetica. V tem delu je bilo opaènih nekaj teinella praehelvetica in marginotrunkanid litoklastov – preostankov uni~ene plasti z kaè, da gre za spodnji del te cone. rodovoma Dicarinella in Marginotruncana Nadaljnih 1,45 m (oz. najve~ 1,80 m, ker (sl. 4). Ta podatek in pa izklinjanje plasti z je med vzorcema 8 in 9 za 40 cm razlike) vrsto H. helvetica (ki predstavlja samo sta- ustreza coni Dicarinella concavata. Za cono rej{i del cone H. helvetica) kaèjo na strati- zna~ilna vrsta je redka, zastopana le z nekaj grafsko praznino kot posledico podvodne primerki. V spodnjem delu cone so pogoste erozije. Glede na dobljene podatke manjka- planktonske foraminifere. Za ta del so zna- jo sedimenti, ki bi ustrezali zgornjemu delu ~ilne pogoste Calcisphaerulidae, ki jih je pro- cone H. helvetica in, kot kaè, celotni coni ti vrhu cone vse manj. V foraminifernih Marginotruncana sigali. zdru`bah ({e posebej v prvi, 60 cm debeli, Cona Dicarinella asymetrica je bila ugo- plasti takoj nad plastmi s H. helvetica) pre- tovljena v nadajlnjih 490 cm profila. Spod- 158 Rajka Radoi~i} & Stanko Buser nja meja cone sovpada s pri~etkom tanko- be filled by Upper Cretaceous limestone in plastnatega dela profila. Vrsta, ki ozna~uje form of neptunic dikes. The contact plane cono, je stalno prisotna, ~eprav ne pogostna. between the two limestones dips 40° towards Zdru`be planktonskih foraminifer v coni D. northeast. About the same is the dip of pela- concavata so v spodnjem delu cone razmero- gic Cretaceous limestones (50°/40°). In the ma nespremenljive (M. sigali, M. schneegan- northern part of exposure the Cretaceous si, D. imbricata, Whiteinellae, velike margi- beds dip southeast. In this way the beds form notrunkanide). Podobno kot v profilu a small synclinal or brachisynclinal structu- Bottaccione se v srednjem delu cone pojav- re. It is possible that the Cretaceous limesto- ljata Globotruncanita elevata (pogosta) in ne first deposited in a larger paleokarstic Globotruncanita stuartiformis (zelo redka). doline in the Jurassic limestone, and the V tem delu pride do spremembe v pogostno- platy Cretaceous limestones during compac- sti kalcisferulid; globigerineloidide, hetero- tion became dishlike tilted. A similar phe- helicide in druge majhne planktonske fora- nomenon was descrided by Buser (1986) at minifere so v zgornjem delu cone bolj pogoste Predolina on Mt. Polovnik. The Lower Ju- kot prej. rassic limestone beds below the Upper Cre- Nad omenjenimi foraminifernimi conami taceous pelagic limestones are horizontal. In sledijo rde~i lapornati apnenci, debeli okoli this way appears between the limestones of 240 cm. various ages a clear angular disconformity. At several places the Jurassic limestone beds are slightly tilted towards southeast, termi- Biostratigraphy of Late Cretaceous nating the western limb of the Bovec syncli- pelagic limestones from surroundigns ne, respectively brachisyncline. of Bovec in the Julian Alps (Slovenia) The Lower Jurassic light grey limestones are layered with bed thicknesses from 50 to Geologic description of sampled section 100 cm. They contain numerous small mega- lodontids. Not far from the considered secti- The observable hiatus contact between the on in limestone large lithiotid bivalves of shallow marine Lower Jurassic biosparitic species Lithiotis problematica were found; and oolitic limestone and the Upper Creta- they are attributed to Upper Pliensbachian ceous pelagic limestone extends for 7 meters (Buser & Debeljak, 1996). At a few pla- (fig. 2). It is uneven, with shallow microreli- ces in limestone algae of species Palaeodasy- ef in the Lower Jurassic limestone, indica- cladus barrabei were found (Buser, 1986). ted by shallow hollows. In the Lower Juras- The lower part of Upper Cretaceous beds sic limestone no fissures appear that could starts with a 4.80 m thick sequence of light

TABLA 1 - PLATE 1

Cona – Zone: Helvetoglobotruncana helvetica Vzorec 1, Sample 1 1 Whiteinella praehelvetica (Trujillo), x100 2, 3 Helvetoglobotruncana helvetica (Bolli), x100 4, 5 Praeglobotruncana gibba Klaus, x100, x125 6 Dicarinella algeriana (Caron), x100 7 Globotrunkanida aff. Falsotruncana maslakovae Caron, x100 8 Dicarinella hagni (Scheibnerova), x125 9, 10 Marginotruncana cf. M. sigali (Reichel), x110 11 Marginotruncana sp., x110 12 Marginotruncana schneegansi (Sigal), x125 Biostratigrafija zgornjekrednih pelagi~nih apnencev okolice Bovca v Julijskih Alpah 159 160 Rajka Radoi~i} & Stanko Buser grey to greenish limestone. Only higher abo- when referring to earlier authors and for ve it follow rosy to red limestone and marl. comparisons of these beds with similar rocks The lowermost part of Upper Cretaceous li- in neighboring Italy. mestone of 75 cm thickness that overlies the On red marly limestone and marl in the Lower Jurassic layered limestone is massi- Bovec basin the Upper Campanian and Ma- ve, and therefore not easily distiguished from astrichtian flysch beds were deposited. This the Jurassic limestone. The boundary is eas- contact is not visible in the studied section ily determined microscopically, as the pela- because it is covered by the talus material. It gic Cretaceous limestone contains already in was found north of Bovec and south of the the lowermost part the rockbuilding globo- ^ezso~a village. The considered Upper Cre- truncanas. In thin sections of the lowest part taceous limestones and marls may laterally of limestone calcareous fragments are visi- pinch out. In such instances the Upper Cre- ble. They indicate removal by currents or taceous flysch overlies with hiatus directly slumping on the deeper sea bottom. These the Lower Jurassic limestone, as observed in processes led to horizontal thickening or the Slatenik brook southwest of ^ezso~a. pinching out of the lowermost part of the Helvetoglobotruncana helvetica zone that is here scarcely 3–5 cm thick. Above the massi- Paleogeographic conditions between Lo- ve Upper Cretaceous limestone follow 4.05 wer Jurassic and Upper Cretaceous in the m of light grey and greenish platy limestone western part of the Julian Alps area consisting of 2 to 5 cm thick layers. Up- wards lie about 4 m of red platy marly lime- The Julian carbonate platform on which stone and marl that become massive in the shallow marine Lower Jurassic biosparitic upper part. The boundary between light grey and oolitic limestones were deposited was and red limestone is sharp; however, it does formed in the lower part of Upper Triassic. not reprersent a stratigraphic boundary, sin- Westwards it continued to the Trento carbo- ce the Dicarinella asymetrica zone continu- nate platform in Italy. The southerly lying es upwards also in the red limestone. Slovenian basin that separated the Julian The authors of the present paper do not platform in the north from the Dinaric car- use the term “scaglia” because they consider bonate platform in the south pinched out at it too general. We prefer to describe the pe- Srpenica in the So~a valley. According to B u - lagic Upper Cretaceous beds with lithologic s e r (1998), at the end of Pliensbachian be- terms. The term “scaglia” is used by us only gan a stage of intense fracturing of the car-

TABLA 2 - PLATE 2

Cona – Zone: Dicarinella concavata, najni‘ji del (lowermost part) Vzorec 2, Sample 2 1 Marginotruncana sigali (Reichel), x100 2 Whiteinella sp., x100 3, 5 Marginotruncana coronata (Bolli), x110 4 Globotruncana hilli Pessagno, x100 6 Dicarinella aff. D. concavata (Brotzen), po{even presek, (oblique section) x100 7 Globotruncana linneiana (d’Orbigny), Marginotruncana marginata (Reuss) in Marginotruncana coronata (Bolli), x1008 Hedbergella? sp., x100 9 Globotruncana hilli Pessagno, x100 10 Marginotruncana schneegansi (Sigal), x100 11 Globotruncana sp., x110 Biostratigrafija zgornjekrednih pelagi~nih apnencev okolice Bovca v Julijskih Alpah 161 162 Rajka Radoi~i} & Stanko Buser bonate platform that disintegrated into se- sank deeper into the pelagic sea. On the plat- veral parts. [muc (2004) considers this to form shallow marine Lower Lias or even have happened already in the Lower Pliens- Upper Triassic limestones after hiatus first bachian. Blocks were mostly uplifted to be- the light grey pelagic biomicritic limestones, come dry land. On uplifted blocks the Juras- and later the red marly limestones and marls sic limestone became karstified. Along with with globotruncanas were deposited . Certa- this a part of the Jurassic limestones was in areas remained dry land as long as to corroded and eroded. In places the erosion Upper Campanian when finally the entire attained even the Dachastein limestone. In territory of the present western Julian Alps the Krn mountains in Jurassic and Upper became inundated. The Upper Cretaceous Triassic limestone large paleokarstic ponors pelagic beds probably covered the larger part formed. In zhe Kanin mountains several of the western Julian Alps. End of Ma- hunderd meters long open fault fissures are astrichtian the Southern Alps, and also the found that were later filled with pelagic cri- Julian Alps were uplifted above the sea le- noidal Jurassic limestone containing nume- vel. Long lasting erosion removed most of rous brachiopods. [muc (2004) reports that the Jurassic and Cretaceous pelagic beds that limestone blocks in the Mangart area (the could be found at present only in small ero- Travnik structural unit) in Lower Pliens- sion remains (Jurkov{ek et al., 1990). bachian subsided the deepest, and that pela- Similar pelagic red marly limestones and gic sediments were deposited on them. The marls (scaglia) with globotruncanas can be remaining larger area of the present western found also much more to the south in central Julian Alps, i.e. the area of the Mangart pass, Slovenia, as in the Gori{ka Brda, on Banj{i- Triglav lakes, Krn mountains and Bovec, ce, Col, below Mt. Nanos, at Studeno, Kalce subsided as a submarine plain not earlier near Logatec, Hinje, Stari Breg and Rigelj. than in Bathonian. In it sedimented on the These limestones were named by D r obne Lower Jurassic or even Dachstein limestone and Pavlovec (1969) after the Podsabotin the condensed limestones of the ammonitico village in Gori{ka Brda the Podsabotin beds. rosso type that contain in their lower part They belong to upper part of the Upper Cre- manganese nodules. In the Krn mountains taceous, and they reach upwards into the the paleokarstic ponors were filled with va- lower part of Tertiary resp. into the Paleoce- riegated calcareous breccia. ne. To distinguish the Podsabotin beds that Areas at the Mangart pass, in Bovec sur- are younger and partly of different litholo- roundings and in Krn mountains remained gic composition from the beds in the Bovec as dry land blocks until the Upper Cretace- surroundings considered in the present pa- ous resp. Lower Turonian. Then also they per, we propose to name these pelagic grey

TABLA 3 - PLATE 3

Cona - Zone: Dicarinella concavata, najni‘ji del (lowermost part) Vzorca ?2 in 3, Samples ?2 and 3 1 Marginotruncana undulata (Lehmann), x110 2 Dicarinella concavata (Brotzen), rahlo deformirana, (slightly deformed) x110 3 Whiteinella sp., x125 4 Dicarinella imbricata (Monord) in Whiteinella sp., x110 5 Globotruncanita? sp., x100 6 Marginotruncana paraconcavata Porthault, x100 7 Marginotruncana renzi (Gandolfi), x125 8 Contusotruncana cf. C. fornicata (Plummer), x125 Biostratigrafija zgornjekrednih pelagi~nih apnencev okolice Bovca v Julijskih Alpah 163 164 Rajka Radoi~i} & Stanko Buser and red Upper Cretaceous limestones and zone planktonic foraminifers are frequent. marls in Julian Alps the Bovec beds, after Typical for this part are frequent Calcispha- the town of Bovec. erulidae that upwards become rarer. In foraminiferal assemblages (especially in the first, 60 cm thick bed just above the beds with H. Biostratigraphy of Upper Cretaceous beds helvetica) prevail large marginotruncanidas in the studied section (coronata, undulata, sinuosa, tarfayaensis). ?Marginotruncana sigali and Marginotrun- Globotruncanas are extremely numerous cana schneegansi are very frequent as well. in all samples, but in some of them they are Accordingly, these assemblages show more poorly preserved and hardly determinable. likelyhood with the Marginotruncana sigali In the section of 6.20 m thickness three PF zone than with the Dicarinella concavata zones (planktonic foraminifers zones) were zone from the Bottaccione section (P r emo- established: Helvetoglobotruncana helveti- li-Silva & Sliter, 1994, 12). A single in- ca, Dicarinella concavata and Dicarinella dividual of species Dicarinella concavata asymetrica zone. The zones are described in was found in the section, in the lowermost English along with the Slovenian text. part of the 60 cm thick bed, about 10 cm A 3 to 5 cm thick layer containing the above the bed with species Helvetoglobo- species Helvetoglobotruncana helvetica, ob- truncana helvetica. In this part several lit- served in the section southeast of Bovec, hoclasts – remnants of a destroyed bed – overlying the limestones with paleodasycla- with genera Dicarinella and Marginotrun- duses, pinches out laterally (submarine ero- cana were observed (fig. 4). This data and sion). H. helvetica, designating the zone, is pinching out of the bed with species H. hel- frequent. Simultaneous presence of species vetica (which represents only the oldest part Whiteinella concavata and of marginotrun- of H. helvetica zone) indicate a stratigraphic canidas indicates the lower part of this zone. gap as a result of submatrine erosion. With The next 1.45 m (resp. at most 1.80 m, respect to comparable data the sediments since between samples 8 and 9 occurs a dif- corresponding to the upper part of H. helve- ference of 40 cm) correspond to the Dicari- tica zone are missing and, as it looks like, nella concavata zone. The species characte- also the entire Marginotruncana sigali zone. ristic for the zone is rare, represented by The Dicarinella asymetrica zone was reco- only a few individuals. In the lower part of gnized in the following 490 cm of the section.

TABLA 4 - PLATE 4

Cona – Zone: Dicarinella concavata, najni‘ji del (lowermost part) Vzorec 2, Sample 2 1 Dicarinella primitiva (Dalbiez), x125 2 Marginotruncana schneegansi (Sigal), x100 3 Whiteinella sp. in Dicarinella hagni (Scheibnerova), x100 4 Marginotruncana sigali (Reichel), x100 5 Marginotruncana cf. M. sigali (Reichel), x110 6 Dicarinella sp. aff. D. canaliculata (Reuss), x100 7 Marginotruncana paraconcavata Porthault, x100 8 Marginotruncana? sp., x110 9 Whiteinella sp., x100 10 Dicarinella sp. cf. D. imbricata (Monord), x100 Biostratigrafija zgornjekrednih pelagi~nih apnencev okolice Bovca v Julijskih Alpah 165 166 Rajka Radoi~i} & Stanko Buser

The lower zone boundary coincides with the Buser, S. & Debeljak, I. 1996: Lower Ju- rassic beds with bivalves in south Slovenia. – Geo- start of the finer layered part of the section. logija, 37/38 (1994/95), 23–62, Ljubljana. The species characteristic for this zone is con- Drobne, K. & Pavlovec, R. 1969: Le Faciès sistently present, although not frequent. As- paléocènes en Slovénie. – 3. simpozij Dinarske semblages of planktonic foraminifers in the asociacije, 27–33, Zagreb. Jurkov{ek, B., [ribar, L., Ogorelec, B. D. concavata zone are relatively constant in & Kolar-Jurkov{ek, T. 1990: Pelagi~ne jurske the lower part of zone (M. sigali, M. schne- in kredne plasti v zahodnem delu Julijskih Alp. – egansi, D. imbricata, Whiteinellae, large mar- Geologija 31/32 (1988/89), 285–328, Ljubljana. Kossmat, F. 1908: Beobachtungen über Ge- ginotruncanidas). Similarly as in the Bottac- birgsbau des mittleren Isonzogebietes. – Verh. Ge- cione section, in the middle part of the zone ol. R. A., 69–94, Wien. appear Globotruncanita elevata (frequent) Ku{~er, D., Grad, K., Nosan, A. & Ogo- relec, B. 1974: Geolo{ke razmere so{ke doline and Globotruncanita stuartiformis (very ra- med Bovcem in Kobaridom. – Geologija 17, 425– re). In this part the frequency of calcispha- 476, Ljubljana. erulidas changes; globigerineloididas, hete- Nedela-Devidé, D. 1957: Zna~enje globotrunkanida za rje{avanje nekih stratigrafskih pro- rohelicidas and other small planktonic blema u Jugoslaviji. – 2. kongres geologa Jugosla- foraminifers become more frequent in the up- vije. Savez. geol. dru{tava SFRJ, Sarajevo. per part of the zone than below. Pav{i~, J. 1979: Zgornjekredni in paleocen- ski nanoplankton v Poso~ju. – Geologija 22/2, 225– Above the mentioned foraminifer zones fol- 276, Ljubljana. low red marly limestones, about 240 cm thick. S e l l i , R. 1953: La geologica dell’alto bacino Isonzo (Stratigrafia e tettonica). – Gionale di Ge- ol. 2a, 19, 153 str., 8 tab., Bologna. [muc, A. 2004: Sedimentolo{ke in stratigraf- Literatura ske raziskave jurskih in krednih plasti Julijskih Alp. Doktorska disertacija. – NTF, Oddelek za geo- Buser, S. 1986: Tolma~ listov Tolmin in Videm logijo, Rokopis 167 str. 10, tabl., Ljubljana. (Udine). Osnovna geolo{ka karta SFRJ 1:100.000. Premoli Silva, I. & Sliter, W. V. 1994: – Zvezni geolo{ki zavod Beograd, 103 str., Be- Cretaceous planctonic foraminiferal biostrati- ograd. graphy and evolutionary trends from the Bottac- Buser, S. 1987: Osnovna geolo{ka karta SFRJ, cione section, Gubbie, Italy. – Paleontolographia list Tolmin in Videm. – Zvezni geolo{ki zavod Be- Italica, 82, 1–89, tab. 1–26, Pisa. ograd, Beograd. Winkler, A. 1921: Das mittlere Isonsogebiet. Buser, S. 1996: Geology of western Slovenia – Jahrb. geol. Staatsanstalt, 70, 11–124, Wien. and its paleogeographic evolution. V: D r obne, Winkler, A. 1924: Ueber den Bau der östlic- K., Gori~an, [. & Kotnik, B. (uredniki): – The hen Südalpen-Mitt. Geol. Ges., 2–272, Wien. role of Impact Processes in the Geological and Winkler-Hermaden, A. 1936: Geologische Biological Evolution of Planet Earth. Internatio- Studien in den inneren Julischen Alpen. – Zen- nal Workshop, ZRC SAZU, 111–132, Ljubljana. tralbl. Min. Geol. Pal., B, 54–68, Stuttgart.

TABLA 5 - PLATE 5

Cona – Zone: Dicarinella concavata, ni‘ji del (lower part) Vzorca 4 in 6, Samples 4 and 6 1, 2 Saccocoma sp., Calcisphaerulidae, x90, x100 3 Dicarinella imbricata (Monord), x100 4 Globotruncana sp. aff. bulloides Vogler, x100 5 Marginotruncana renzi (Gandolfi), x110 6, 7 Whiteinella spp., x100 8 Dicarinella canaliculata (Reuss), x110 9 Marginotruncana sigali (Reichel), x100 10 Marginotruncana undulata (Lehmann), x110 11 Whiteinella sp., x110 12 Globotruncana sp., x110 13 Marginotruncana schneegansi (Sigal), x110 Biostratigrafija zgornjekrednih pelagi~nih apnencev okolice Bovca v Julijskih Alpah 167 168 Rajka Radoi~i} & Stanko Buser

TABLA 6 - PLATE 6

Cona – Zone: Dicarinella concavata, ni‘ji del (lower part) Vzorca 5 in 6, Samples 5 and 6 1 Dicarinella imbricata (Monord) in Globotruncana linneiana (d’Orbigny), x100 2 Marginotruncana schneegansi (Sigal), x100 3 Marginotruncana pseudolinneiana Pessagno, x100 4 Globotruncana sp., x100 5 Marginotruncana marginata (Reuss) in Marginotruncana cf. M. renzi (Gandolfi), x100 6 Dicarinella cf. D. canaliculata (Reuss), x100 7 Marginotruncana sigali (Reichel), x125 8 Calcisphaerulidae 9 Globotruncana cf. G. linneiana (d’Orbigny) in Dicarinella imbricata (Monord), x110 Biostratigrafija zgornjekrednih pelagi~nih apnencev okolice Bovca v Julijskih Alpah 169 170 Rajka Radoi~i} & Stanko Buser

TABLA 7 - PLATE 7

Cona – Zona: Dicarinella concavata, zgornji del (upper part) Vzorca 7 in 8, Samples 7 and 8 1 Globotruncana sp. in Whiteinella sp., x110 2 Globotruncana aff. G. hilli Pessagno, x110 3 Marginotruncana marginata (Reuss), x100 4 Helvetoglobotruncana sp. aff. H. achensis, x110 5 Marginotruncana sigali (Reichel), x110 6 Dicarinella imbricata (Monord), x110 7 Contusotruncana fornicata (Plummer) in Globotruncana sp., x110 8 Marginotruncana coronata (Bolli), x120 9 Globotruncana hilli Pessagno, x100

Cona – Zona: Dicarinella asymetrica Vzorec 10, Sample 10 10 Globotruncana? (aff. G. hilli Pessagno), x100 Biostratigrafija zgornjekrednih pelagi~nih apnencev okolice Bovca v Julijskih Alpah 171 172 Rajka Radoi~i} & Stanko Buser

TABLA 8 - PLATE 8

Cona – Zone: Dicarinella asymetrica Vzorec 10, Sample 10 1-3 Dicarinella asymetrica (Sigal), x100, x100, x110 4 Contusotruncana fornicata (Plummer), x100 5 Marginotruncana schneegansi (Sigal), x110 6 Marginotruncana renzi (Gandolfi), x110 7 Marginotruncana cf. M. tarfayaensis (Lehmann), x110 8 Dicarinella imbricata (Monord), x100 9 Globotruncana sp. aff. G. orientalis El Naggar, x110 10 Globotruncana leupoldi Bolli, x100 Biostratigrafija zgornjekrednih pelagi~nih apnencev okolice Bovca v Julijskih Alpah 173 174 Rajka Radoi~i} & Stanko Buser

TABLA 9 - PLATE 9

Cona – Zone: Dicarinella asymetrica Vzorca 10 in 11, Samples 10 and 11 1 Dicarinella concavata (Brotzen), x100 2 Marginotruncana schneegansi (Sigal), x110 3 Marginotruncana sigali (Reichel), x110 4 Dicarinella asymetrica (Sigal), x110 5 Marginotruncana sinuosa Porthault, x110 6 Saccocoma sp., x100 7 Whiteinella sp., x110 8 Marginotruncana pseudolinneiana Pessagno, x100 9, 10 Dicarinella? sp., x100 Biostratigrafija zgornjekrednih pelagi~nih apnencev okolice Bovca v Julijskih Alpah 175 176 Rajka Radoi~i} & Stanko Buser

TABLA 10 - PLATE 10

Cona – Zone: Dicarinella asymetrica (iz dogodka G. Elevata, from G. elevata event) Vzorci 13-17, Samples 13-17 1, 3, 5, 6 Globotruncanita elevata (Brotzen), x100 4 Dicarinella concavata (Brotzen), x100 5 Contusotruncana sp., x110 7 Dicarinella cf. D. asymetrica (Sigal), x110 8 Rugotruncana? sp., x110 (vzorec 17) Biostratigrafija zgornjekrednih pelagi~nih apnencev okolice Bovca v Julijskih Alpah 177