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_________________________________________________________________________________________________________ Kölner Forum Geol. Paläont., 19 (2011) M. ARETZ, S. DELCULÉE, J. DENAYER & E. POTY (Eds.) Abstracts, 11th Symposium on Fossil Cnidaria and Sponges, Liège, August 19-29, 2011 _________________________________________________________________________________________________________ area. Dense microbial encrustation (automicrites) (Fig. 1B) on corals are common, while Lithocodium/Bacinella are very rare. That suggests higher nutrient level as one of the main controlling factor because the moderate development of Lithocodium/Bacinella encrustations (as on corals in the lower part of the studied section) is commonly assumed as the indicator of oligotrophic/mildly mesotrophic environment. By contrast, Late Jurassic phaceloid pachythecaliines are known to occur within diversified coral assemblages, and are commonly associated by Lithocodium/Bacinella. These studies were supported by a research grant from the Polish Ministry of Science and Higher Education (No. 2P04D 028 29). BARON-SZABO, R.C. (2002): Scleractinian Corals of the Cretaceous. A guide to Cretaceous forms with Descriptions, Illustrations, and Remarks on Their Systematic Position. - Baron- Szabo, Knoxville, 539 pp. BARON-SZABO, R.C. & STEUBER, T. (1996): Korallen und Rudisten aus dem Apt im tertiären Flysch des Parnass-Gebirges bei Delphi-Arachova (Mittelgriechenland). - Berliner Geowissenschaften Abhandlungen E, 18: 3–75. ELIÁŠOVÁ, H. (1978): La rédefinition de l'ordre Hexanthiniaria Montanaro-Gallitelli, 1975 (Zoantharia). - Vestník Ústredního Ústavu Geologického, 53: 89–101. FENERCI-MASSE, M., MASSE, J.-P., KOŁODZIEJ, B., IVANOV, M. & IDAKIEVA V. (2011): Mathesia darderi (Astre) (Bivalvia, Hippuritoidea, Monopleuridae): morphological, biogeographical and ecological changes in the Mediterranean domain during the late Barremian–Albian. - Cretaceous Research. doi: 10.1016/j.cretres.2010.10.005 IDAKIEVA, V. (2003): Lower Cretaceous Scleractinia in a part of Central Fore-Balkan (taxonomy and buildups). PhD Thesis, Sofia University, 327 pp. (in Bulgarian) KOŁODZIEJ, B. (2003): Scleractinian corals of suborders Pachythecaliina and Rhipidogyrina: Discussion on similarities and description of species from Štramberk-type limestones, Polish Outer Carpathians. - Annales Societatis Geologorum Poloniae, 73: 193–217. RONIEWICZ, E. (2008): Kimmeridgian–Valanginian reef corals from the western Moesian Carbonate Platform from Bulgaria. - Annales Societatis Geologorum Poloniae, 78: 91–134. RONIEWICZ, E. & STOLARSKI, J. (2001): Triassic roots of the amphiastraeid scleractinian corals. - Journal of Palaeontology, 75: 34–45. Fig. 1: (previous page): A, B. Dense aggregation of individuals of small rudist Mathesia darderi (ASTRE) and pachythecaliine corals. On B arrows show dense microbial crusts (automicrite). C. Aulastraea sp. D. Pleurophyllia sp. E. Carolastraea graeca BARON-SZABO. F. Gen. nov. 1. sp. nov. 1. G–H. Gen. nov. 2. sp. nov. 1. Upper Barremian. 82
_________________________________________________________________________________________________________ Kölner Forum Geol. Paläont., 19 (2011) M. ARETZ, S. DELCULÉE, J. DENAYER & E. POTY (Eds.) Abstracts, 11th Symposium on Fossil Cnidaria and Sponges, Liège, August 19-29, 2011 _________________________________________________________________________________________________________ Clear- and turbid-water coral assemblages from Barremian–Lower Aptian of Bulgaria Bogusław KOŁODZIEJ 1 , Vyara IDAKIEVA 2 , Marin IVANOV 2 & Vassil ZLATARSKI 3 1 Institute of Geological Sciences, Jagiellonian University, Oleandry str., 2a, 30-063 Kraków, Poland; boguslaw.kolodziej@uj.edu.pl 2 Department of Geology, Paleontology and Fossil Fuels, Sofia University, Sofia, Bulgaria; idakieva@gea.uni-sofia.bg, mivanov@gea.uni-sofia.bg, 3 131 Fales Rd., Bristol, RI 02809, USA, vzlatarski@yahoo.com During Barremian–Early Aptian times several carbonate platforms existed on the northern Tethyan margin in Bulgaria. In particular the Lovech Urgonian Group (Fig. 1A) in the Central Fore-Balkan contains abundant and diversified corals (about 120 species). Occurrence of turbid- and clear-water environment is a characteristic feature of this mixed siliciclastic-carbonate Urgonian system. Taxonomy of corals from turbid-water environments (mainly from marls) where studied already in the 19 th century (F. TOULA), but mostly since the 1960s (V. ZLATARSKI, V. TCHECHMEDJIEVA, V. IDAKIEVA). Recent studies were particularly focused on corals from carbonate units (clear-water environments), coral palaeoecology and palaeoenvironmental factors controlling development of coral assemblages. Turbid-water coral assemblages form segment or cluster (matrix-supported) reefs and level-bottom assemblages, rarely small frame (skeleton-supported) reefs. Usually massive colonies formed the core of the isolated patch reefs, whereas phaceloid, dendroid or ramose corals grew on the periphery of the buildups (IDAKIEVA & IVANOV 2002). These later, often still in life position, indicate constratal growth fabric (low syndepositional relief). Corals are represented mainly by stylininans, cyathophorids, actinastreids, faviids (Eugyra, Hydnophora, Felixygyra), clausastreids and microsolenines (e.g, IDAKIEVA 2003). Coral skeletons show features typical for turbid-water and soft-substratum environments, such as growth anomalies due to partial colony mortality, reorientation of growth direction (Fig. 1F), and the presence of colony and corallite morphologies adapted to stressful factors of turbid-water settings (Fig. 1E, F; cf. Sanders & Baron-Szabo 2005). Platy and low domal colonies dominate as possible response to a soft, unstable substrate and decrease in light intensity. Among them clausastreids (Fig. 1E) and Amphiaulastraea attain the largest size suggesting their high resistance to sedimentation. Some corals as hydnophoroid-meandroid faviids show significant morphological plasticity (from platy to branching growth forms). Small-sized colonies, common encrustations by heterotrophic organisms (very rare microbial crusts) on the lower parts of coral colonies (Fig. 1D), and rare on the upper ones indicate changes in sedimentation rate with intermittent rapid sedimentation events of lethal or sublethal effects. Some localities show diversified coral assemblages and high coral density, as result of low sediment input. Level-bottom coral assemblages are dominated by solitary forms: Montlivaltia multiformis TOULA, Axosmilia spp., Actinoseris alloiteaui BEAUVAIS & ZLATARSKI (Fig. 1J). An interesting assemblage is dominated by abundant small fungiform colonies of the endemic species Dimorphocoeniopsis beauvaisorum ZLATARSKI (ZLATARSKI 1967) (Fig. 1G–I), recently discovered also in the Vratsa Urgonian Group. Clear-water coral bioconstructions (mainly biostromes) differ in significance of microbialites, presence or absence of microencrusters, particularly phototrophic ones (Lithocodium aggregatum, Bacinella irregularis), as well as in bioerosion rate, what were presumably controlled by sedimentation rate and trophic regime (Fig. 1K–M). Chaetetids and other calcified sponges locally participate in frame construction. Rudists cooccur with corals; however they usually form biostromes without or with rare corals. The Emen Fm, in localities NW of Veliko Tarnovo, contains abundant and diversified corals of the suborder Pachythecaliina associated with small rudists (Fig. 1M; KOŁODZIEJ et al., this volume). Lithocodium–Bacinella-dominated facies (with rare corals) facies is poorly developed. Microbialite-dominated reefs do not occur. Growth and demise of clear- and turbid water coral assemblages occurred in various eustatic, tectonic and climatic contexts, which resulted in such environmental factors as water depth, nutrient and siliciclastic input, oxygenation or hydrodynamics. The depositional pattern was controlled mainly by 83
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