This study summarizes and provides new data concerning the composition, fabrics, depositional environment
and palaeogeographic distribution of Upper Jurassic–lowermost Cretaceous (Kimmeridgian–Berriasian) upper
slope build-ups with complex microencruster-microbialite-calcified sponge frameworks associated with large
amount of early marine cement crusts. The focus is on reef carbonates from the ˇStramberk-type limestones from
the Carpathians (Getic Carbonate Platform) and Apuseni Mountains in Romania, with additional data from the
Plassen Carbonate Platform (Northern Calcareous Alps, Austria) and the ˇStramberk Carbonate Platform (Western
Carpathians, Czech Republic and Poland). The microencrusters, often of problematic biological affinity, are
mainly Crescentiella morronensis (Crescenti 1969), Labes atramentosa Eli´aˇsov´a 1986 and Radiomura cautica
Senowbari-Daryan & Sch¨afer 1979. Specialized encrusting calcified sponges are also common, with Perturbatacrusta
leini Schlagintweit & Gawlick 2011 as the most abundant and characteristic form. Light-dependent
microencrusters (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 framework
varieties are considered for the studied build-ups. The main differences between these types reflect a
bathymetric zonation in their development. The abundance of Crescentiella, microbialites, massive radiaxial
fibrous cement crusts, and poorly diversified microencruster/sponge assemblages, are all suggesting that Type I
framework variety is characteristic for build-ups formed in the deepest parts of an upper slope environment. Type
II most probably developed at slightly lower depths than Type I, as revealed by its main features (clusters of
calcified sponges and microencrusters associated with less extensive cement crusts) and distribution between the
other two types in the sedimentary sequences. Type III, the most common, characterizes build-ups formed at the
shallowest 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, microbialites
and 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-based
perspective, these upper slope build-ups exemplify triple hybrid carbonates which are intimate combinations
of microbial and skeletal components (microencrusters/microbialites and calcified sponges), associated with
abiotic precipitates (early marine cement crusts). Their palaeogeographic importance is reflected in their formation
on the slopes of rimmed carbonate platform systems facing open oceanic domains, predominantly within
the central Western Tethys Realm. Such hybrid build-ups appear to have been absent on the southern European
shelf where other reef frameworks commonly developed on carbonate ramps and ramp-type carbonate platforms.