48 Abstracts

Lower Cretaceous shallow-water carbonate rocks in Romania: an overview

Ioan L BucurI lBabes-Bolyai University, Department of geology, str. M. Kogalniceanu nr.l, 400084 Cluj-Napoea, Romania, e-mail: ibueur@bioge.ubbcluj.ro

Key words: Lower Cretaceous, Berriasian-Valanginian, Urgonian facies, Limestone, Romania

The Lower Cretaceous (Berriasian-Aptian) carbonates from Romanian belong to several tectonic-structural units ofthe Carpathian area and its foreland: (l) the Bucovinian and Transylvanian Nappes ofthe Eastern Carpathians (Trasylvanides and Median Dacides, in SĂNDULESCU, 1984), with Berriasian-Valanginian and/or Barremian-Aptian (Urgonian) limestones occuring in the Rarău, Hăghimaş andPerşani mountains; (2) the Danubian domain and the Getic Nappe ofthe Southern Carpathians (Marginal Dacides and Median Dacides, respectively, in SĂNDULESCU, 1984), with Lower Cretaceous shallow-water limestones present in the Southern Vălcan Mountains (Danubian domain) and in the Dâmbovicioara, Vânturariţa, Haţeg-Pui and Reşiţa zones (within the Getic Nappe); (3) theAutochthonous ofthe NorthernApuseni Mountains (lnternal Dacides, in SĂNDULESCU, 1984) (Bihor-Pădurea Craiului Unit),and (4) Moesian Platform and Southern Dobrogea.

Additionally, Lower Cretaceous (mainly Urgonian) limestone olistolithes (klippes), sometimes ofremarkable sizes, are embedded in flysch or wildflysch deposits in the Eastern Carpathians (Ceahlău, Ciucaş, Bucegi; PATRULIUS, 1969), or in the SouthernApuseni Mountains (IANOVICI et al., 1976). Sonie ofthese units are still scarcely studied, especially concerning their micropaleontological content and their facies (e.g. Rarău, Perşani, Vânturariţa, Haţeg-Pui and Southern Vălcan zones).

The limestones from Rarău belong to the Transylvanian Nappe (MUTIHAC, 1968; SĂNDULESCU, 1984). From these limestones, MUTIHAC, 1968 mentioned rudists (Requienia ammonia), and orbitolinids (Palorbitolina lentieularis). The Urgonian limestones from Rarău, developed during Late Barremian-Early Aptian within a predominantly external carbonate platform. The age of these limestones is indicated by the two orbitolinids frequently identified in thin sections, Montseeiella arabica (HENSON) andPalorbitolina lentieularis (BLUMENBACH).

The bioclasts consist of fragments of corals, chaetetids, bivalves, gastropods, brachiopodes, echinoderms, anellid tubes, problematic microorganisms (Baeinella irregularis RADOICIC and Lithoeodium aggregatum ELLIOTT), calcareous algae [(Salpingoporella pygmaea (GUEMBEL), Terquemella sp., Sporolithon rude (LEMOINE), rivulariacean cyanobacteria], foraminifera [Lentieulina sp., Montseeiella arabica (HENSON), Palorbitolina lentieularis (BLUMENBACH), Coscinophragma cribrosa (REUSS), Haplophragmoides sp., Dobrogelina sp., Neotrocholina jribourgensis GUILLAUME & REICHEL].

The red algae, some foraminifera and the microproblematica (Baeinella-Lithoeodium, Koskinobulina socialis CHERCHI & SCHROEDER) frequently formed successive crusts on corals and sponges. At some levels, corals are numerous and diverse, but generaly badly preserved.

The following taxa were identified: Calamophylliopsis spp. including cf. Calamophylliopsis Jotisaltensis (BENDUKIDZE); Microsolenina: Mierosolena sp., or similar genera (numerous) Latiastraea sp.; ? Latusastraea sp. ? Heterocoenia sp, Eohydnophora spp. ar related genera hydnophoroide-meandroide (numerous); cf. Columnocoenia ksiazkiewiezi MORYCOWA; Clausastraea spp. including Clausastraea alloiteaui MORYCOWA; Thecosmilia sp. The microsolenid fragments are frequent even ifthey don1t form platy-coral assemblages.

The Urgonian limestones from the Perşani Mountains crop out in Gărbova Hill and the adjacent areas. They belong to the Neoautochtonous cover ofthe Transylvanian nappe (post-tectonic, sensu SĂNDULESCU, 1976) orto Paleoautochtonous (cf. Patruliusetal.,1966).

These limestones are generally massive, frequently reddish in colour and contain requienid rudists, together with other bivalves, gastropods, corals, orbitolinids and other foraminifera, and calcareous algae.

The microfacies are predominantly micri tic (bioclastic wackestone and wackestone/packstone, coarse bioclastic packstone, coral-bearing floatstone) . Less frequent are bioclastic grainstone-packstone and coarse bioclastic grainstone /rudstone. The bioclasts are very diverse: sponges, corals, rudists and other bivalves, gastropods, annelid worms, echinoderms, foraminifera

Geodiversity 49

and calcareous algae. They developed in a relatively low energy carbonate platform environment (inner platform). The patch-reefs with corals and the coarse bioc1astic grainstone-rudstone developed, most probably, in a more external

environment. The micropaleontological assemblage consist offoraminifera and ca1careous algae. The foraminifera are represented by:

Charentia cuvi/lieri NEUMANN, Coscinophragma cribrosa REUSS, Everticyc/ammina hedbergi (MYNC), Sabaudia minuta (HOFKER), Nezzazatinella sp., Vercorsella sp., small textulariids, Mesorbitolina minuta DOUGLASS and Mesorbitolina texana (ROEMER). Among ca1careous algae we identified frequent dasyc1adales [(Griphoporella cretacea (DRAGASTAN), Triploporella carpatica BUCUR, Triploporella cf. marsicana PRATURLON, ?Triploporella sp., Neomer.is cretacea STEINMANN, Neomeris sp., Terquemella sp.)] and red algae [("Solenopora"-Parachaetetes sp., Polystrata alba (pFENDER), Sporolithon rude (LEMOINE)]. The microproblematica Carpathoporella occidentalis DRAGASTAN, Lithocodium aggregatus ELLIOTT andBacinella irregularis RADOICIC are also present.

The two orbitolinid foraminifera (Mesorbitolina minuta and Mesorbitolina texana) indicate the Late Aptian age for the Urgonian limestones of Perşani Mountains. In the Aptian limestones from Perşani, DRAGASTAN (1980) has identified Toucasia carinata, Praeorbitolina cormyi, Mesorbitolina texana, andNeomeris cretacea.

Vânturariţa area (also contains urgonian limestones cropping out on small areas. According to DRAGASTAN (1980), these limestones contain corals (Mesomorpha ornata), stromatoporoids, and chaetettids (Actinostromaria sp. and Chaetetopsis crinita), forarninifers (Palaeodictyoconus sp., Sabaudia minuta), and ca1careous algae (Salpingoporella urladanasi, Salpingoporella muehlbergii)

In the Haţeg-Pui zone, the knowledge of the Lower Cretaceous limestones is even more limited. Practically, a comprehensive Tithonian-Lower Aptian series was separated (STILLA, 1985). From the Urgonian limestones STILLA (1985) mentioned the following macro- and micropaleontological assembalge: Requienia ammonia, Requienia scalaris, Toucasia carinata, Vercorsella scarsellai, and Urgonina alpillensis.

Our research in the last years tried to separate the Upper Jurassic from Lower Cretaceous deposits following the microfacies and the micropaleontological content. The Lower Cretaeous deposits contain a large variety of microfacies, from mudstone, bioc1astic mudstone/wackestone, fenestral wackestone to intrac1astic-bioc1astic packstone, intrac1astic-bioc1astic packstone/grainstpne or peloidal grainstone. The bioc1asts consist of coral fragments (less frequent) bivalve, gastropod and echinoderm fragments, benthic foraminifera ca1careous algae, microproblematica (Bacinella-Lithocodium) and rivulariacean­type cyanobacteria. The micropaleontologic assemblage contain foraminifera [Paracoskinolina? jourdanensis (FOURY & MOULLADE), Paracoskinolina cf. sunnulandensis (MAYNC) , Palaeodictyoconus sp., Charentia cuvillieri NEUMANN, Andersenolina sagittaria (ARNAUD-VANNEAU & BOISSEAU), Andersenolina sp., Nautiloculina sp., Ammobaculites sp., Vercorsella sp. , Verneulina p. , Bellorusiella sp., Commaliama sp., Dobrogelina sp.], calcareous algae [Suppiluliumaella atI. praebalkanica BAKALOVA, Salpingoporella pygmaea (GUEMBEL), Boueina cf. pygmaea PIA], problematica (Lithocodium aggregatum ELLIOTT, Bacinella irregularis RADOICIC) and rivulariacean-type cyanobacteria. The orbitolinid foramnifera (Paracoskinolina? jourdanensis andP. cf. sunnilandensis) are important arguments for the Barremian-Early Apţian age of a part of these limestones. Also, the dasyc1ad alga Suppiluliumaella praebalkanica is known from the same stratigraphic interval. Unfortunately, at this time is impossible to separate cartographically the Upper Jurassic limestones from the Lower Cretaceous ones. Also, it is hard to say ifthe whole succession contains also Neocomian (Berriasian-Hauterivian) deposits marking a possible continuity between Upper Jurassic and Barremian-Aptian.

Finally, the Southern Vălcan area is another case were little is known on the biostratigr'Y'hy and facies ofthe Lower Cretaceous limestones. BUCUR & POP (2001) presented some preliminary data on their micropaleontological content. The foraminifera and algae association consists of Montseciella arabica (as paleodictioconus arabicus), lVeotrocholinajribourgensis, Neomeris cretacea, S. pygmaea (as S. exi/is) and S. patruliusi.

Recent research brings more details on the microfacies and the age of these limestones. Above the Upper Jurassic limestones, a sequence of about 40 m develops of Neocomian (Berriasian-Valanginian) limestones, followed by the Izvama formation (Barremian - Aptian), the last carbonate succes sion in the region. The Berriasian-Valanginian assemblage consist of forarninifera [Andrersenolina cherchiae ARNAUD-VANNEAU & BOISSEAU, Mohlerina basiliensis (Mohler), Nautiloculina broennimanni Amaud-Vanneau & Peybernes, Mayncina sp.] and calcareous algae [Clypeina parasolkani FARINACCI & RADOICIC . The Urgonian facies ofthis sequence is indicated by the presence of rudist fragments. Paracoskinolina? jourdanesis FOURY & MOULLADE and Montseciella arabica (HENSON) are two orbitolinid foraminifera pointing to the Barremian-Early Aptian age ofthe Izvama Formation.

The areas best studied for their biostratigraphy and micropaleontology are represented by Hăghimaş Mountains, Dâmbovicioara, and Reşiţa zones, the Bihor-Pădurea Craiului unit, and Southern Dobrogea (see details in BUCUR, 1994, 1997, 2000a, 2000b, 2001; BUCUR & COCIUBA, 1996, 2001; COCIUBA, 2000; DRAGASTAN 1967, 1975, 1980, 1981, 1989; DRAGASTAN etal., 1998;MANTEA, 1985;PATRULIUS, 1969, 1976; PATRULIUS inIANOVICletal. , 1976),.

Some ofthese regions contain both Neocomian (Berriasian-Valanginian, sometime also Hauterivian) and Barremian­Aptian (Urgonian) shallow-water deposits. Berriasian-Valanginian shallow-water limestones are well described from South Dobrogea (DRAGASTAN et al. , 1998), Haghimaş Mountains (DRAGASTAN, 1975), Resiţa-Moldova Nouă zone (BUCUR, 1997), and are also documented by recent reserch in Pădurea Craiului and Dâmbovicioara (piatra Craiului Mountains).

50 Abstracts

References

BUCUR LI., 1994: Algues calcaires de la zone de Reşiţa-Moldova Nouă (Carpathes Meridionales, Rournanie). Revue de paleobiologie, 1112: 147-209. BUCUR 1.1., 1997: Formaţiunile mezozoice din zona Reşiţa-Moldova Nouă (Munţii Aninei şi estul Munţilor Locvei). Presa Universitară Clujeană, Cluj-Napoca, 214 pp. BUCUR LI,. 2000a: LowerCretaceous dasyc1ad algae from the Pădurea Craiului massif(NorthernApuseni Mountains, Romania). Acta Palqeontologica Romaniae, 2 (1999): 53-72 BUCUR 1.1., 2000b: Provincialism of some Lower Cretaceous dasyc1ad algae from Mid- and Eastem Europe; paleogeographic significance. 31" International Geological Congress, Rio de Janeiro Brazii (CD RomAbastract). BUCUR 1.1.,2001 : Lower Cretaceous algae ofthe Reşiţa-Moldova Nouă zone. In: BUCUR 1.1. et al. (eds.), Algae and carbonate platforms in western part of Romania. Field Trip Guidebook, 137-166, Cluj University Press, Cluj-Napoca. BUCUR 1.1. and COCIUBA 1. , 1996: Microbiostratigraphic markers in the Lower Cretaceous deposits from Pădurea Craiului (Northern Apuseni Mountains). Anuarul Institutului de Geologie şi Geojizică al României., 69, suppl.l (90th Aniv. Conf. GIR): 40-43 . BUCUR 1.1. and COCIUBA 1., 2001: Upper Jurassic-Lower Cretaceous deposits from Pădurea Craiului. In : BUCUR I.l.et al. (eds.), Algae and carbonate platforms in the western part of Romania, Field trip guidebook, 43-52, Cluj University Press, Cluj­Napoca COCIUBA 1., 2000: Upper Jurassic-Lower Cretaceous deposits in the soth-western part of Pădurea Craiului. Formal lithostratigraphic units. Studia Universitatis Babeş-Bolyai, Geologia, XL V/2: 33-61. DRAGASTAN O., 1967: Alge calcaroase in Jurasicu1 superior si Cretacicul inferior din Muntii Apuseni. Studii si Cercetari de Geologie, Geograjie, Geojizica, Geologie, 12/2: 441-454 DRAGASTAN O., 1975: Upper Jurassic and Lower Creatceous microfacies from the Bicaz Valley basin (East Carpathians). Institut de Geologie et Geophysique, Memoires , XXI: 1-87. DRAGASTAN O., 1980: Alge calcaroase in Mezozoicul si Terţiarul României. Cu o introducere privind reconstituirea paleomediilor sedimentare. Editura Academiei RSR, Bucuresti, 169 pp. DRAGASTAN O,. 1981 : Mesozoic dasyc1adaceae from Romania: distribution and biostratigraphical importance. Facies, 4: 165-196 DRAGASTAN O,. 1989: Calcareous algae (new and revised), Microproblematicae and Foraminiferida of Jurassic-Lower Cretaceous deposits from the Carpathians area. Revista Espanola de Micropaleontologia, XXIII: 5-65. DRAGASTAN O., MARINESCU M., GHEORGHE D. and TINTEANU c., 1989: Upper bauxite sensu D. Patrulius and some new algae of Pădurea Craiului Mts. (NorthernApuseni). Revue Roumaine de Geologie, Geographie et Geophysique, Geologie, 33: 55-67. DRAGASTAN O., NEAGU TH., BARBULESCU A. and PANA 1., 1998: Jurasicul şi Cretacicul din Dobrogea centrală şi de Sud (Paleontologie şi stratigrafie), 249 p., 54 pls., Bucureşti IANOVICI v., BORCOŞ M., BLEAHU M., PATRULIUS D., LUPU M., DIMITRESCU R. and SAVU H. , 1976: Geologia Munţilor Apuseni. EdituraAcademiei RSR, Bucureşti, 631 pp. MANTEA G,. 1985: Geological studies in the Upper basin of the Someşul Cald Valley and the Seacă Valley region (Bihor­VIădeasa Mountains). Anuarul Institutului de Geologie şi Geojizică, 66: 5-89 MUTIHAC v., 1968: Structura geologică a compartimentului nordic din Sinc1inalul Marginal Extern. Editura Academiei RSR, Bucureşti, 127 pp. PATRULIUS D., POPA-DAMIOAN E., & DIMITRIU-POPESCU 1. 1966: Seriile mezozoice autohtone şi pânza de decolare Transilvană în împrejurimile Comanei (Munţii Perşani). Anuarul Comitetului Geologic, XXXV, 397-434. PATRULIUS D., 1969: GeologiaMasivului Bucegi şi a Culoarului Dâmbovicioara. Editura Academiei RSR, Bucureşti, 321 pp. PATRULIUS D., 1976: Upper Jurassic-Lower Cretaceous carbonate rocks in the eastern part ofthe Getic carbonate platform and the adjacent flysch troughs. In: PATRULIUS D. DRĂGĂNESCU A, BALTRES A, POPESCU B. & RĂDAN S., Carbonate rocks and evaporites guidebook, 71-82, Institute ofGeology and Geophysics, Bucharest POP G. & BUCUR 1.1.,2001: Upper Jurassic and Lower Cretaceous sedimentary formations from the Vâlcan Mountains (South Carpathians). Studia Universitatis Babeş-Bolyai, series Geologia , XLVII2: 77-94 SĂNDULESCU M., 1976: La correlation du troncon oriental avec celui meridional des Carpates rournaines. Dări de Seamă, Institutul de Geologie şi Geojizică, LXIII5, 177-194. SĂNDULESCU M., 1984: Geotectonica României, Editura tehnică, Bucureşti, 356 pp. STILLA AL., 1985: Geologie de la region de Haţeg-Cioc1ovina-Pui-Băniţa (Carpathes Meridionales). Anuarul Institutului de Geologie şi geojizică: .91-179.