Adriatic-Dinaridic Carbonate Platform Research Articles

Dinosaur footprints in the Upper Hauterivian deposits of the Palud Bay in Istria, Croatia

Sixteen dinosaur footprints are exposed along the upper-bedding plane of a single Upper Hauterivian limestone layer in the Palud bay (western Istria, Croatia). This distinct footprint-bearing horizon is part of the thick Mesozoic Adriatic-Dinaridic Carbonate Platform stratal succession. Strata at the Palud site are characterized by peritidal (shallow subtidal to intertidal) limestone with several shallowing-upward cycles composed of mudstone, peloidal wackestone/packstone, peloidal packstone/grainstone and fenestral mudstone/wackestone with common geopetal infill. The Late Hauterivian age of these deposits is determined from their microfossil assemblage, which is dominated by ostracods, benthic foraminifera and calcareous green algae Dasycladales. The Palud site dinosaur footprints are circular to elliptical in shape, with no clearly visible digit impressions (except for one questionable example), and are rather large with average length of 30 cm. Most footprints have a well-defined expulsion rim that represents displacement and compression of soft, waterlogged sediment substrate by the weight of the dinosaur. All of the footprints are of nearly same shape and size, which indicates that they were produced by the same kind of tracemaker – likely a sauropod dinosaur. These animals left their footprints on top of a shallowing-upward succession of an intertidal environment during a short subaerial exposure of fine-grained carbonate sediment.

Stable isotopic (δ13C and δ18O) signatures of biogenic calcretes marking discontinuity surfaces: a case study from Upper Cretaceous carbonates of central Dalmatia and eastern Istria, Croatia

Biogenic calcretes associated with a regional Cretaceous to Paleogene subaerial unconformity and an intraformational composite (polygenic) surface in Upper Cretaceous intra-platform peritidal successions in central Dalmatia and eastern Istria, Croatia (Adriatic-Dinaridic Carbonate Platform), were analyzed for their δ13C and δ18O signatures in order to provide insight into the conditions of subaerial exposure and calcrete development. The distinctly negative δ13C signatures of biogenic calcretes marking the regional subaerial unconformity differ considerably from the δ13C values of the host marine limestones. This indicates carbon isotope exchange of primary marine CaCO3 with CO2 released by root and rhizomicrobial respiration and subsequent precipitation of pedogenic calcrete. The range of δ13C (from −13.1 to −8.2 ‰ Vienna PeeDee Belemnite standard, VPDB) and δ18O (from −10.1 to −6.1 ‰ VPDB) values of calcretes are similar to those reported from calcretes elsewhere, and the δ13C values of biogenic calcretes with typical Microcodium aggregates (−13.1 to −12.3 ‰ VPDB) at the Sibenik locality are very close to, or at the lower limit of, values for soil carbonates formed in isotopic equilibrium with soil CO2. These values are expected for authigenic pedogenic carbonates formed under the influence of C3 plant communities, without influence from heavier carbon from pre-existing carbonate and lack of input of atmospheric CO2. Such low δ13C values support the interpretation of Microcodium aggregates as being precipitated under a direct biological control within the soil, although the relationship between formation mechanisms and stable isotope signatures of Microcodium needs further investigation. The δ13C values (−4.4 to −3.6 ‰ VPDB) of rhizogenic calcretes formed inside firmground Thalassinoides burrows of the composite surface at the Sibenik locality are more negative than the δ13C values of the host marine limestones, which confirms that the composite surface went through a phase of meteoric pedo(dia)genesis. However, the overall δ13C values of calcretes are less negative than expected, which might reflect contamination from associated primary marine carbonate. This study represents the first detailed stable isotope investigation of calcretes from carbonate successions of the External Dinarides, and the results may be applied to discontinuities present in other shallow-water carbonate rock successions.

Discontinuity surfaces in Upper Cretaceous to Paleogene carbonates of central Dalmatia (Croatia): Glossifungites ichnofacies, biogenic calcretes, and stratigraphic implications

Substrate-controlled ichnofacies and biogenic calcretes represent key features for identification and interpretation of discontinuities in the carbonate rock record, which are of great significance for stratigraphic interpretations and correlations. Intraformational firmground and composite surfaces, as well as a regional Cretaceous to Paleogene (K–Pg) subaerial unconformity, developed in Upper Cretaceous to Paleogene intra-platform peritidal successions in central Dalmatia, Croatia (Adriatic-Dinaridic Carbonate Platform, ADCP), were analyzed for their trace fossil and subaerial exposure features. Thalassinoides (probably T. paradoxicus) box-work burrow systems of the substrate-controlled Glossifungites ichnofacies characterize the two documented firmgrounds and one composite (polygenic) surface. Rhizogenic laminar calcretes developed subsequently inside burrows of the composite surface through diagenetic overprint of marine sediment that passively infilled the burrows. While the formation of the two firmgrounds was probably caused by cessation of precipitation and/or deposition of calcium carbonate due to relative sea-level fall, the recorded trace fossils associated with the composite surface indicate that this surface developed through both submarine firmground and subaerial exposure stages probably caused by several episodes of regression and transgression, and exemplifies the general complexity of hiatal surfaces in shallow-marine carbonate successions. The regional K–Pg subaerial unconformity is characterized by biogenic (beta microfabric) calcretes with rhizoliths including Microcodium aggregates, root tubules, as well as alveolar-septal structures. Laminar calcretes and pisoids, together with in situ and resedimented speleothems, and bauxitic deposits, were also recorded. The unconformity developed due to formation of a forebulge in front of the approaching Dinaridic orogen. Ichnological and subaerial exposure features, together with stratigraphic implications derived from the analyzed discontinuities, serve as examples that can be applied to discontinuities present in carbonate successions elsewhere.

Stratigraphic framework, discontinuity surfaces, and regional significance of Campanian slope to ramp carbonates from central Dalmatia, Croatia

The sedimentology, microfacies, and stratigraphic age (from planktonic and benthic foraminifera and strontium-isotope stratigraphy) of a 300-m-thick Upper Cretaceous carbonate succession from the Island of Čiovo (central Dalmatia, Croatia) were analyzed in order to determine the lithostratigraphic, depositional, and chronostratigraphic framework. The Cretaceous strata were deposited in the southern part of the long-lasting (Late Triassic to Paleogene) Adriatic-Dinaridic Carbonate Platform (ADCP), one of a few late Mesozoic, intra-Tethyan, peri-Adriatic (sub)tropical archipelagos. The succession is separated by a firmground formational boundary into two lithostratigraphic units: the underlying Middle to Upper Campanian Dol Formation consisting of slope pelagic limestone with intercalated turbidites and debrites, and the overlying Upper Campanian Čiovo Formation composed of outer-ramp bioclastic-lithoclastic and echinoderm-dominated packstone. Age, lithology, and depositional settings of the Čiovo Formation are different from other penecontemporaneous, regionally important inner-platform carbonate successions within the ADCP domain. Therefore, the Čiovo Formation is proposed here as a new lithostratigraphic unit. Regionally important condensed intervals in the form of at least two firmground surfaces, characterized by Thalassinoides burrows (with phosphatic mineralization) that belong to the Glossifungites ichnofacies, occur in the lowermost part of the Čiovo Formation. Abrupt shallowing of depositional environments at the boundary between the Dol and the Čiovo Formation, and the generation of the formational boundary firmground, likely correlate with the regionally recorded Upper Campanian Event that represents a global eustatic sea-level fall. A regionally important subaerial exposure surface with nodular calcrete, rhizoliths, and Microcodium aggregates in the upper part of the Čiovo Formation represents a regional subaerial unconformity that was recorded across the ADCP domain and was interpreted as a consequence of diachronous and differential uplift of various parts of the platform in response to the formation of a forebulge in front of the approaching Dinaridic orogen.

Integrated biostratigraphy and carbon isotope stratigraphy of the Lower Cretaceous (Barremian to Albian) Adriatic-Dinaridic carbonate platform deposits in Istria, Croatia

The Adriatic-Dinaridic carbonate platform (ADCP) was one of the largest and relatively well preserved Mesozoic platforms in the Mediterranean region (central Tethys). The peninsula Istria, in the northwestern part of the ADCP, is built up predominantly of shallow-water carbonates of the Middle Jurassic (Dogger) to Eocene age and, to a lesser extent, of Paleogene clastic deposits (flysch and calcareous breccia). This study focuses on a Lower Cretaceous (Barremian to Albian) succession of strata at five localities in western Istria. Stratigraphic determinations are based on identification of nine microfossil assemblages (benthic foraminifera and calcareous algae Dasycladales) and on using their taxa as index fossils. The age of strata with these microfossil assemblages, however, is questionable. Most of the age uncertainties are associated with a regional emersion, which occurred on the ADCP during the Aptian or close to the Aptian–Albian transition. It is unclear what portions of the Upper Aptian and/or Lower Albian are missing along this unconformity. A stable isotope study was conducted on homogenous micritic matrix samples in an attempt to resolve some of these uncertainties. Variations in carbon isotope compositions proved useful for stratigraphic correlation between the examined successions of strata, for improving their age determination, and for relating them to other coeval successions that span an important time interval of major oceanographic changes and carbon-cycle perturbations associated with the Early Aptian oceanic anoxic event (OAE 1a).

Stable isotope analysis of Upper Tithonian limestones with dinosaur footprints from Kirmenjak quarry (Istria, Croatia)

The Kirmenjak locality of western Istria, Croatia, represents the oldest evidence of a dinosaur presence on the Adriatic- Dinaridic Carbonate Platform (ADCP). In a quarry at this locality, almost a thousand sauropod footprints are recognized in one distinctive trackbearing horizon within the Upper Tithonian limestones. The stable isotopes of oxygen and carbon, in conjunction with microfacies analysis of carbonate rocks exposed in this quarry, unravel details about the marginal marine or coastal environments in which sauropods left their footprints. Rocks from the trackbearing horizon, and laterally adjacent area, represent intertidal fenestral mudstones that form the top of a shallowing- upward succession, capped with a thin peloidal packstone/grainstone layer and overlain by subtidal mudstone. The formation and preservation of footprints was favoured by short-duration exposure of muddy sediment and its rapid burial beneath more mud. The isotopic composition of the sample from the trackbearing horizon is not substantially different from those of an adjacent area without footprints and from the overlying mudstone. Stable isotope analysis supports petrographic observations that the conditions on the carbonate tidal fl at during formation of rocks with dinosaur footprints were not unique. Documented variations in stable isotope compositions refl ect minor differences in the depositional and diagenetic history of the Kirmenjak quarry succession.

A NEW DINOSAUR TRACKSITE IN THE LATE ALBIAN OF ISTRIA, CROATIA

A new site with dinosaur footprints has been found in the upper Albian sediments of Istria, Croatia. The site was discovered near the city of Pula, at the Zlatne Stijene locality. The carbonate succession of the Zlatne Stijene locality is characterized by thin bedded limestones deposited in peritidal and foreshore environments. The microfossil assemblage found at the site indicates a late Albian age. One clearly distinguishable footprint and four indeterminate rounded tracks were discovered at the investigated outcrop. The footprint is tridactyl and belongs to a medium-sized bipedal theropod dinosaur of approximately 3 meter in length. Regarding dimensions and morphology it is closely related to the other late Albian theropod footprints from the Adriatic-Dinaridic carbonate platform (ADCP). The Zlatne Stijene locality fits with the Brontopodus ichnofacies concept.

FIRST RECORD OF DINOSAURS IN THE LATE JURASSIC OF THE ADRIATIC-DINARIDIC CARBONATE PLATFORM (CROATIA)

Abstract All previously known dinosaur remains on the Adriatic-Dinaridic carbonate platform (ADCP) were described from Cretaceous deposits. A new trackbearing locality is late Tithonian in age and represents the oldest evidence of dinosaurs on the ADCP. The site is in an active quarry near the village of Kirmenjak in western Istria. Almost a thousand sauropod footprints including 23 single trackways have been found on the outcrop. Oval impressions represent pes prints, and horseshoe-shaped impressions represent manus prints; pes prints are 23 to 52 cm long. Calculated heights at the hip range from 153 to 306 cm. The main direction of dinosaur movement was toward the northeast, and some of the individuals were moving together. The trackways show a characteristic narrow gauge, and pace and stride lengths indicate a slow walk. The footprints are similar to Parabrontopodus ichnogenus, and the ichnocoenosis could be assigned to the Brontopodus ichnofacies. The presence of the sauropods on the Adriatic-Dinaridi...

Interaction between Permo-Triassic rifting, magmatism and initiation of the Adriatic-Dinaridic carbonate platform (ADCP)

Permo-Triassic rift-related magmatism in the Dinarides produced an intrusive gabbro-diorite-syenite-granite formation and an extrusive basalt-andesite-dacite formation with abundant pyroclastic rocks. They are spatially and genetically related to Late Permian to Norian rift-related sedimentary formations of the Adriatic-Dinaridic carbonate platform (ADCP). The volcanic and pyroclastic rocks are interlayered with fossiliferous sediments that range between the Late Permian and Middle Norian; the plutonic rocks, which are intrusive into Late Paleozoic and Scythian-Anisian sediments, have radiometric ages ranging between 262 and 212 Ma. Based on major and trace element contents, rocks of the Permo-Triassic magmatic association originated by fractional crystallization from primitive alkalic basalt to olivine tholeiite melts. Volcanic rocks were affected by strong ocean-hydrothermal metamorphism. Initial 87Sr/86Sr ratio of 0.703 and d18O of 5.6‰ of the most primitive rocks indicate an upper mantle origin. Most ...

Outline of the geology of Slovenia

Taking into consideration the Alps/Dinarides connection, the western part of the Zagorje-Mid-Transdanubian (or Sava) Zone (ZMTZ) in Slovenia, which is located between the Eastern and Southern Alps, includes disconnected outcrops of the northwesternmost Internal Dinaridic units. The northern part of the ZMTZ in Slovenia, which is close to the Periadriatic Lineament, is mainly composed of an Albian-Cenomanian to Late Cretaceous flysch sequence, underlain by Jurassic basinal sediments, which can be correlated to the Sava-Vardar Flysch. The outcrops are located in frontal parts of the Julian-Savinja Nappe. The southern part of the ZMTZ in Slovenia includes the Sava Nappe (or the Slovenian Trough), which is thrust upon the northern margin of the Adriatic-Dinaridic carbonate platform, e.g. the External Dinarides and Southern Alps, respectively. It is composed of Aptian to Cenomanian clastics and carbonates, disconformably overlain by Late Cretaceous carbonate flysch. It can be correlated to the Bosnian Fysch in the Central Dinarides. Both the Northern and Southern Zones can be followed westward up to Italian frontier. All presented data indicate a spatial connection between the northwesternmost Dinarides and the easternmost Alps during Alpine geodynamic evolution. Their apparent lack of connection in the present structure of the Dinarides and Alps is the result of the postorogenic indenting of Adria or of the African promontory, and related strike-slip faulting.

Facies variability in Lower Liassic carbonate successions of the Western Dinarides (Croatia)

In the Western Dinarides the Lower Liassic carbonates are underlain by Upper Triassic “Hauptdolomit”, whereas the first appearance of the foraminiferOrbitopsella praecursor (Gumbel) marks the beginning of the Middle Liassic. Their composition, observed at several localities in Western Croatia, shows a correlation of sedimentation events, which took place during Early Liassic on the Adriatic-Dinaridic carbonate platform. Facies variability is interpreted as result of autocyclic sedimentary processes on which the carbonate platform reacted by periodical oscillations of sea-bottom near the fair-weather wavebase. As a consequence, the Lower Liassic carbonate successions in the Dinarides is characterized by stacking of two main types of coarsening-upward parasequences: (1) the basal part of the Lower Liassic succession is represented by parasequences composed of mudstones or pelletal-bioclastic wackestones as their lower members, and peloidal-bioclastic wackestone/packstones to grain-stones as their upper members; and (2) the upper part of the Lower Liassic succession with parasequences consisting of mudstones or pelletal-bioclastic wackestones overlain by ooid grainstones. Judging from the composition of parasequences and thickness relations of their members, the first type is interpreted to comprise late transgressive system tract (ITST) and/or early highstand system tract (eHST), while the second type corresponds to a late highstand system tract (1HST) and/or early lowstand system tract (eLST) of a third-order sequence.

Geodynamic evolution of the Central Dinarides

The central part of the Dinarides, unlike the northwestern and southeastern Dinarides, shows a consistent pattern in the distribution of the large tectonostratigraphic units. From southwest (Apulia) to northeast, the following five main units originating in different parts of the Mesozoic Tethys, can be distinguished: (1) Adriatic–Dinaridic carbonate platform formations; (2) carbonate–clastic units (`flysch bosniaque') of the passive continental margin; (3) ophiolite-bearing formations of the Dinaridic Ophiolite Zone, also containing radiolarites, greywackes and shales, including mélange formations, and overstepped Late Jurassic to Cretaceous cover sequences; (4) active continental margin units represented by Upper Cretaceous–Palaeogene trench sediments with blueschists, tectonized ophiolite mélange, Alpine medium-pressure metamorphic rocks originated from Upper Cretaceous–Palaeogene sediments, and Alpine synkinematic granitoids; (5) a nappe consisting of allochthonous Palaeozoic–Triassic formations which is thrust onto the ophiolites and genetically related sedimentary formations. The frontal parts of this nappe directly overlie the northeastern margin of the Adriatic–Dinaridic carbonate platform, i.e. the External Dinarides. The evolution of the Central Dinarides was controlled by a sequence of tectonic events which took place within the Alpine cycle: (1) Rifting processes lasting some 40–50 Ma which started in the Late Permian and ended in the Norian. (2) Opening of the oceanic Dinaridic Tethys commenced in the Late Triassic and persisted for some 70–80 Ma until the end of the Jurassic. (3) Subduction processes and emplacement of ophiolites started in Late Jurassic–Early Cretaceous times; during the closing phase of the `Dinaridic Ocean' (or Dinaridic Tethys) the Palaeozoic–Triassic nappe was emplaced on the ophiolites. The thrusting was accompanied by Alpine metamorphism (120–100 Ma). (4) The main Alpine deformational event and medium-pressure metamorphism with synkinematic granite plutonism took place in Late Eocene–Early Oligocene times when the ophiolite and Palaeozoic–Triassic nappes were emplaced on the Adriatic–Dinaridic carbonate platform which, at the same time, was deformed resulting in the development of the External Dinarides fold-and-thrust belt.