TY - JOUR

T1 - Upper Jurassic–lowermost Cretaceous hybrid build-ups of the Western Tethys Realm: Cement-rich microencruster-microbialite-calcified sponge framework

AU - Ples, George

AU - Schlagintweit, Felix

AU - Kołodziej, Bogusław

AU - Bucur, Ioan I.

AU - Gawlick, Hans-Jürgen

AU - Mircescu, Cristian Victor

AU - Sasaran, Emanoil

AU - Lazar, Juliana

PY - 2024

Y1 - 2024

N2 - This study summarizes and provides new data concerning the composition, fabrics, depositional environmentand palaeogeographic distribution of Upper Jurassic–lowermost Cretaceous (Kimmeridgian–Berriasian) upperslope build-ups with complex microencruster-microbialite-calcified sponge frameworks associated with largeamount of early marine cement crusts. The focus is on reef carbonates from the ˇStramberk-type limestones fromthe Carpathians (Getic Carbonate Platform) and Apuseni Mountains in Romania, with additional data from thePlassen Carbonate Platform (Northern Calcareous Alps, Austria) and the ˇStramberk Carbonate Platform (WesternCarpathians, Czech Republic and Poland). The microencrusters, often of problematic biological affinity, aremainly Crescentiella morronensis (Crescenti 1969), Labes atramentosa Eli´aˇsov´a 1986 and Radiomura cauticaSenowbari-Daryan & Sch¨afer 1979. Specialized encrusting calcified sponges are also common, with Perturbatacrustaleini Schlagintweit & Gawlick 2011 as the most abundant and characteristic form. Light-dependentmicroencrusters (e.g., “Lithocodium-Bacinella”) that are abundant in coeval overlying coral-dominated reefs,are rare, as are corals (microsolenids adapted to low-light level). Three dominant types of fabric-based frameworkvarieties are considered for the studied build-ups. The main differences between these types reflect abathymetric zonation in their development. The abundance of Crescentiella, microbialites, massive radiaxialfibrous cement crusts, and poorly diversified microencruster/sponge assemblages, are all suggesting that Type Iframework variety is characteristic for build-ups formed in the deepest parts of an upper slope environment. TypeII most probably developed at slightly lower depths than Type I, as revealed by its main features (clusters ofcalcified sponges and microencrusters associated with less extensive cement crusts) and distribution between theother two types in the sedimentary sequences. Type III, the most common, characterizes build-ups formed at theshallowest depths of the upper slope environment and is composed of alternating layers of diverse microencrusters(including several light-dependent species), calcified sponges, rare microsolenid corals, microbialitesand early marine cement crusts. The distribution patterns of these framework varieties (Type I to Type III)together with their associated facies, strengthen this depositional interpretation. From a process-basedperspective, these upper slope build-ups exemplify triple hybrid carbonates which are intimate combinationsof microbial and skeletal components (microencrusters/microbialites and calcified sponges), associated withabiotic precipitates (early marine cement crusts). Their palaeogeographic importance is reflected in their formationon the slopes of rimmed carbonate platform systems facing open oceanic domains, predominantly withinthe central Western Tethys Realm. Such hybrid build-ups appear to have been absent on the southern Europeanshelf where other reef frameworks commonly developed on carbonate ramps and ramp-type carbonate platforms.

AB - This study summarizes and provides new data concerning the composition, fabrics, depositional environmentand palaeogeographic distribution of Upper Jurassic–lowermost Cretaceous (Kimmeridgian–Berriasian) upperslope build-ups with complex microencruster-microbialite-calcified sponge frameworks associated with largeamount of early marine cement crusts. The focus is on reef carbonates from the ˇStramberk-type limestones fromthe Carpathians (Getic Carbonate Platform) and Apuseni Mountains in Romania, with additional data from thePlassen Carbonate Platform (Northern Calcareous Alps, Austria) and the ˇStramberk Carbonate Platform (WesternCarpathians, Czech Republic and Poland). The microencrusters, often of problematic biological affinity, aremainly Crescentiella morronensis (Crescenti 1969), Labes atramentosa Eli´aˇsov´a 1986 and Radiomura cauticaSenowbari-Daryan & Sch¨afer 1979. Specialized encrusting calcified sponges are also common, with Perturbatacrustaleini Schlagintweit & Gawlick 2011 as the most abundant and characteristic form. Light-dependentmicroencrusters (e.g., “Lithocodium-Bacinella”) that are abundant in coeval overlying coral-dominated reefs,are rare, as are corals (microsolenids adapted to low-light level). Three dominant types of fabric-based frameworkvarieties are considered for the studied build-ups. The main differences between these types reflect abathymetric zonation in their development. The abundance of Crescentiella, microbialites, massive radiaxialfibrous cement crusts, and poorly diversified microencruster/sponge assemblages, are all suggesting that Type Iframework variety is characteristic for build-ups formed in the deepest parts of an upper slope environment. TypeII most probably developed at slightly lower depths than Type I, as revealed by its main features (clusters ofcalcified sponges and microencrusters associated with less extensive cement crusts) and distribution between theother two types in the sedimentary sequences. Type III, the most common, characterizes build-ups formed at theshallowest depths of the upper slope environment and is composed of alternating layers of diverse microencrusters(including several light-dependent species), calcified sponges, rare microsolenid corals, microbialitesand early marine cement crusts. The distribution patterns of these framework varieties (Type I to Type III)together with their associated facies, strengthen this depositional interpretation. From a process-basedperspective, these upper slope build-ups exemplify triple hybrid carbonates which are intimate combinationsof microbial and skeletal components (microencrusters/microbialites and calcified sponges), associated withabiotic precipitates (early marine cement crusts). Their palaeogeographic importance is reflected in their formationon the slopes of rimmed carbonate platform systems facing open oceanic domains, predominantly withinthe central Western Tethys Realm. Such hybrid build-ups appear to have been absent on the southern Europeanshelf where other reef frameworks commonly developed on carbonate ramps and ramp-type carbonate platforms.

KW - Microencrusters

KW - Calcified sponges

KW - Upper slope build-ups

KW - Synsedimentary cements

KW - Hybrid Carbonates Western Tethys Realm

M3 - Article

JO - Upper Jurassic–lowermost Cretaceous hybrid build-ups of the Western Tethys Realm: Cement-rich microencruster-microbialite-calcified sponge framework

JF - Upper Jurassic–lowermost Cretaceous hybrid build-ups of the Western Tethys Realm: Cement-rich microencruster-microbialite-calcified sponge framework

ER -