Adriatic Carbonate Platform Research Articles

Pachycolumella nov. gen., shallow-water benthic imperforate foraminifera and its species from the Maastrichtian and Paleocene of Iran

A new pfenderinid taxon is described as Pachycolumella nov. gen. with the two species P. elongata n. sp. (type-species), and P. acuta n. sp. The type material comes from the upper Maastrichtian Tarbur Formation of the Zagros Zone, SW Iran. Areconstruction of Pachycolumella nov. gen is presented including allmorpho-structural elements such as a conspicuous central columella. The wall of the elongate and triserially coiled test is microgranular-agglutinated displaying a pseudokeriothecal texture. Pachycolumella species are also reported from the Paleocene (Danian–early Thanetian) of Turkey,Oman, Iran (this paper), India, and Pakistan, thus representing aK–Pg survivor taxon. In Iran Pachycolumella is reported from various localities belonging to both the former northern and the southern Neo-Tethyan margin. In the western Neo-Tethyan realm (e.g., Adriatic Carbonate Platform), Pachycolumella seems to be absent.

UPPER TRIASSIC TO LOWER JURASSIC SHALLOW-WATER CARBONATES NORTH OF LAKE SHKODRA (NW ALBANIA, ALBANIAN ALPS ZONE): PART OF THE ADRIATIC CARBONATE PLATFORM BASEMENT

The palaeogeographic reconstruction of the Adriatic Carbonate Platform and its continuation to the south represents a helpful tool to understand the Mesozoic palaeogeography of the Dinarides–Albanides–Hellenides oro-genic system. In the present paper poorly known Upper Triassic to Lower Jurassic (Toarcian) shallow-water car-bonates from the Shkodra area in northwest Albania (external Albanides; Albanian Alps zone) were investigated, dat-ed mainly by larger benthic foraminifera. The microfossil associations as well as litho- and microfacies characteristics are equivalent to contemporaneous shallow-water carbonate successions of the Adriatic Carbonate Platform basement to the NW (in the High Karst zone). As a result of our study we clearly see a continuation of the Adriatic Carbonate Platform from the Dinarides to the Albanides. In the area north of Lake Shkodra no Upper Triassic to Lower Jurassic hemipelagic sedimentary rocks, which could be a possible connection between the Budva Unit to the NW and the Cukali Unit to the SW, were detected.

Late Cretaceous geodynamics of the northern sector of the Adriatic Carbonate Platform (W Slovenia)

Late Cretaceous geodynamics of the northern sector of the Adriatic Carbonate Platform (W Slovenia)

A visual determination method for uniaxial compressive strength estimation based on Croatian carbonate rock materials

To identify visually detectable elements that influence carbonate rock strength, a detailed inspection of 231 samples, mainly from the Adriatic Carbonate Platform in Croatia, was conducted prior to laboratory testing. ANOVA was used to detect statistically significant carbonate rock material parameters that influence UCS: Lithology, Fabric, Defects and Porosity (LFDP) and their optimal classes. ANOVA was also used to find a statistically significant model that contains four major effects on the strength of carbonate rock (LFDP) with three two-way interactions: lithology*fabric, fabric*defects and defects*porosity. According to four basic influential parameters, the new procedure is coined LFDP determination and is described in detail.The presented results indicate that the LFDP determination method is reliable enough for use in engineering geological practice on Croatian carbonate rocks but also for use in other regions. While the presented method may be applied to other regions worldwide, its suitability to local conditions should be tested.The LFDP determination method is simple, efficient, inexpensive and versatile. It can be applied to outcrops, cuts, quarries, tunnels, borehole cores and similar. However, it is important to note that this method cannot replace laboratory testing and should be only used to collect preliminary information on carbonate rock material properties and possible ranges in UCS values.

The Cenomanian–Turonian boundary in the northwestern part of the Adriatic Carbonate Platform (Ćićarija Mtn., Istria, Croatia): characteristics and implications

The Cenomanian–Turonian boundary (CTB) in the Cicarija Mountain region (northern Istria, Croatia) is characterized by calcisphere limestone successions with a firmground and glauconite horizon, bioturbated intervals, tempestites, and slumped structures as well as microbially laminated and organic-rich interbeds deposited in the northwestern part of the intra-Tethyan Adriatic Carbonate Platform (AdCP). Compilation of the results from three studied sections (Vodice–Jelovica, Martinjak and Planik) of litho-, bio-, and microfacies analyses, X-ray diffraction, SEM, EDS, and stable isotope analyses allowed reconstruction of marine paleoenvironmental conditions during this time period. Shallow-marine carbonate deposits of the Milna Formation underlie a drowned-platform succession of the Sveti (Sv.) Duh Formation. The contact between these two formations is sharp and commonly marked by slumped deposits. The Sv. Duh Formation consists of about 100 m of calcisphere wackestone enriched in organic matter. The results of preliminary δ13C and δ18O stable isotope analyses indicate the influence of the global Oceanic Anoxic Event (OAE2) on the deposition of this carbonate succession. Anoxic and hypoxic conditions in the water column lead to major changes in the shallow-marine carbonate system of the AdCP. Numerous benthic foraminifera declined during that time, but planktonic foraminifera and calcareous dinoflagellates diversified and expanded greatly. The results of this research provide new insights into the character of the CTB interval in this part of the Tethyan realm. Local and regional synsedimentary tectonics combined with global upper Cretaceous sea-level dynamics allows the correlation of the investigated deeper-marine lithostratigraphic units with OAE2.

Post‐impact event bed (tsunamite) at the Cretaceous–Palaeogene boundary deposited on a distal carbonate platform interior

AbstractWe show crucial evidence for the Cretaceous–Palaeogene (K–Pg) boundary event recorded within a rare succession deposited in an inner‐platform lagoon on top of a Mesozoic, tropical, intra‐oceanic (western Tethys) Adriatic carbonate platform, which is exposed at Likva cove on the island of Brač (Croatia). The last terminal Maastrichtian fossils appear within a distinct 10–12 cm thick event bed that is characterised by soft‐sediment bioturbation and rare shocked‐quartz grains, and is interpreted as a distal tsunamite. Directly overlying this is a 2 cm thick reddish‐brown clayey mudstone containing planktonic foraminifera typical of the basal Danian, and with elevated platinum‐group elements in chondritic proportions indicating a clear link to the Chicxulub asteroid impact. These results strongly support the first discovery of a “potential” K–Pg boundary tsunamite on the neighbouring island of Hvar, and these two complementary sections represent probably the most complete record of the event among known distal shallow‐marine successions.

Early Eocene evolution of carbonate depositional environments recorded in the Čikola Canyon (North Dalmatian Foreland Basin, Croatia)

The stratigraphic succession in the Cikola Canyon (part of the North Dalmatian Foreland Basin) was studied in detail to describe both the sedimentological characteristics and fossil assemblages of the Lower Eocene deposits during the initial stage of the foreland basin formation. The North Dalmatian Basin now represents a part of the Outer Dinarides, and was developed in front of the evolving Dinaric structures by tectonic deformation and marine transgression of an emerged and denuded Mesozoic Adriatic Carbonate Platform (AdCP). During the initial phase, a distal ramp of a foreland basin was formed, characterised by carbonate sedimentation, lasting until the Middle Eocene. In a studied section more than 300 m thick, porcelaneous foraminifera, Alveolina, Orbitolitesand complex miliolids (Idalina, Periloculina) prevail, associated with conical agglutinated forms, nummulitids and red algae. These samples belong to the SBZ 11–12 (Ypresian), according to occurrences of Alveolina decastroi, Alveolina cremae, Alveolina multicanalifera and Coskinolina liburnica. Two main lithological units have been described: 1) mudstones to wackestones with sporadic occurrences of ostracods and charophyceae, deposited in restricted lagoonalsettings with several episodes of freshwater influences, and 2) foraminiferal packstones to grainstones with complex miliolids, alveolinids, corallinacean algae and nummulitids, deposited within inner and middle ramp settings. Palaeogene deposition of ramp carbonates in the Outer Dinarides area was mainly controlled by the continuous compressional tectonics, and the deposits today appear in more or less discontinuous outcrops. Palaeogene transgression occurred at different times over various parts of the former carbonate platform area, and subsequent carbonate sedimentation was characterised by deposition in similar environments during different time intervals over spatially restricted carbonate ramps controlled by synsedimentary tectonics.

A wing metacarpal from Italy and its implications for latest Cretaceous pterosaur diversity

Abstract An incomplete bone from the latest Cretaceous dinosaur site of Villaggio del Pescatore (Trieste Province, Italy) is definitely a wing metacarpal of a pterodactyloid pterosaur. It represents the only Italian Cretaceous pterosaur remains known, as well as the only pterosaur from the Adriatic Carbonate Platform. With an estimated minimum length of 136 mm, it belongs to a relatively small individual relative to the standard of latest Cretaceous pterodactyloids. It is not as elongated and gracile as azhdarchid wing metacarpals and shows a mix of features found in Pteranodon and some more basal pterodactyloids. It is one of the very few remains of putative non-azhdarchid pterosaurs from the upper Campanian–Maastrichtian worldwide and supports the view that the Azhdarchidae were not the only pterosaur clade existing during latest Cretaceous times.

Late Cretaceous palynoflora from the central part of the Adriatic Carbonate Platform (Islands of Hvar and Šćedro), southern Croatia

This paper provides the first palynological data from four Upper Cretaceous localities from the Islands of Hvar and Šćedro (southern Croatia), in the central part of the Adriatic Carbonate Platform. Studied material represents palynomorphs produced by coastal vegetation and transported to the shallow marine platform areas. Determined vegetation includes diverse hygrophilous, understory vegetation, range of evergreen needle trees attributable to Pinaceae and Podocarpaceae, as well as Araucarian conifers; ginkgo, cycads and/or bennettites. Flowering plants were likely represented by herbaceous forms. The palynoflora is generally indicative of a temperate, warm and humid climate. The occurrence of the Normapolles group with the presence of Plicapollis sp. and Pseudoculopollis sp. point to Turonian or probable Turonian–Coniacian age, and represent the southernmost record of occurrence within the Normapolles palynological province. Dominance of angiosperms and low abundance of ferns suggests an early-Late Cretaceous age. These findings are supported by the micropaleontological analyses and previously determined age of the sauropod dinosaur footprints described on the Island of Hvar. Based on the paleobotanical and palynological data, the dinosaur diet probably included araucarian conifers, ginkgo and angiosperms, and ferns to a lesser extent.

Authigenic siliceous-carbonate concretions in Cenomanian–Turonian carbonates of southern Croatia; geochemical and biotic record

Numerous regular and irregularly shaped concretions were discovered in southern Croatia within the Upper Cretaceous carbonate deposits, which consist mostly of bioclastic wackestones and packstones. The size of the concretions varies from 2 to 25 cm in diameter for the regular, and up to 40 cm in length for the irregular ones. The concretions have different internal structures and compositions, which vary from those of the host rocks. Some concretions are entirely siliceous, while others exhibit alternating opal silica and carbonate-rich zones. Silica is derived from opal-A secreting marine biota, mostly sponges, whose spicules can be found within the concretions and in the surrounding limestones. The regular shape and alterations of zones are the result of the diffusive supply and fast “consummation” of silica at the growth site. Determined fossil community and bitumen found in the surrounding limestones indicate deposition in the oxygen-depleted deep-marine environment of the Adriatic Carbonate Platform, which belongs to the Sveti Duh Formation (latest Cenomanian–Early Turonian). The carbon isotope composition of the concretions corresponds to the globally known Cenomanian–Turonian ‘Oceanic Anoxic Event’ (OAE 2).

Correlation of Carbonate Strata in Gorski Kotar Area (Karst Dinarides, Croatia), An Example of Adriatic Carbonate Platform Environmental Diveristy During the Late Jurassic

Adriatic Carbonate platform environmental diveristy as observed within the carbonate strata in Gorski kotar area (Karst Dinarides, Croatia) was caused by synsedimentary tectonics when the hitherto uniform platform area was partly differentiated into two different sedimentary environments. In Jasvina zone an uninterrupted shallow-water platform succession occur, indicating shallow subtidal and peritidal environmental conditions. On the other hand, the Breze zone is characterised by the presence of deeperwater pelagic influenced carbonate succession, clearly evidencing the sunken intraplatform trough of unknown dimensions, which was possibly connected with the open basin area. Correlation of carbonate strata of the studied sections allows the reconstruction of sedimentary dynamics and events that led to such diversified environment which represent the inner part of the Adriatic Carbonate Platform.

Jurassic Sequences of Sosice and Rovinj Localities (Karst Dinarides, Croatia) as Examples of Long-Distance Tectonic-Controlled Deposition on the Adriatic-Dinaric Carbonate Platform

During the Late Jurrasic Adriatic carbonate platform was characterized by complex palaeogeographical and depositional relationships. A major part of the platform remained within restricted lagoonal settings, but some areas of the platform were uplifted, emerged and karstified, characterised by local deposition of bauxites. However, the NE margin of the platform was contemporaneously partially drowned. Facies correlation from two choosen localities in Karst Dinarides, Croatia; Sošice and Rovinj, reveals that during the Late Jurassic increased accommodation loss on Sošice locality coincided with increased accommodation gain on Rovinj locality. This suggests tectonic movements that were synchronous but of different style consequently enabling the relative uplift on one side of the platform but subsidence on its opposite side. Therefore, it is assumed that the extensive drowning event induced by progressive block faulting on the NE Adriatic carbonate platform margin (where present-day Sošice locality is situated) caused a relative uplift on its SE area (where present-day Rovinj locality is situated) resulting in long term emersion event there.

Microfacies characteristics of the Lower Jurassic lithiotid limestone from northern Adriatic Carbonate Platform (central Slovenia)

Microfacies characteristics of the Lower Jurassic lithiotid limestone from northern Adriatic Carbonate Platform (central Slovenia)

Thermal maturity of Carboniferous to Eocene Sediments of the Alpine–Dinaric Transition Zone (Slovenia)

The Alpine–Dinaric Transition Zone in Slovenia comprises the fold and thrust belt of the Southern Alps (South Karawanken Range, Julian Alps), Slovenian Basin and the Dinarides. The Slovenian Basin located between the Julian and Dinaric carbonate platforms evolved during Middle Triassic time and remained in a deep marine setting till the Late Cretaceous. The thermal history of Carboniferous to Eocene rocks in that area was investigated using vitrinite reflectance (VR) data, apatite fission track analysis and numeric 1D basin modeling. The study shows that maturity patterns are mainly controlled by the thickness of Upper Cretaceous to Eocene flysch deposits, filling the accommodation space. Therefore the thermal overprint reaches a maximum (>4%Rr) in Triassic to Cretaceous sediments of the Slovenian Basin and decreases towards the north and south. Minor sedimentary burial of the Adriatic Carbonate Platform and the Julian Alps results in a lower thermal overprint (<1.5%Rr). The thickness of flysch sediments was about 5km in the area of the Sava Folds, but significantly higher in the central part of the Slovenian Basin. Heat flow during maximum burial in Eocene time was in the order of the global average (60mW/m2). Cooling of Paleozoic and Mesozoic sediments below 110°C occurred between Late Eocene and Early Oligocene times in different parts of the study area. Nappe stacking due to Early (Dinaric) and Late Cenozoic (Alpine) compressional tectonics did not influence the thermal maturity of the sediments.

Potential Cretaceous-Paleogene boundary tsunami deposit in the intra-Tethyan Adriatic carbonate platform section of Hvar (Croatia)

An exceptional 47-m-thick succession of Maastrichtian to Paleocene inner-platform carbonates is exposed on the Dalmatian island of Hvar (Adriatic Sea, Croatia) in a seaside locality called Majerovica. The middle part of this succession is an ~5-m-thick intraformational massive deposit, which is underlain by well-bedded peritidal inner-platform limestones containing latest Maastrichtian rudists and shallow-water benthic foraminifera. This deposit includes a polygenic, matrix-supported carbonate breccia characterized by ripped-up platform limestone lithoclasts, up to boulder sized, and polygenic microbreccia in a muddy matrix. The microbreccia contains rare small intraclasts of pelagic mudstone containing terminal Maastrichtian planktonic foraminifera. The deposit is overlain in turn by mudstone containing a planktonic foraminiferal association belonging to the P0 and Pα zones of the basal Paleogene, and by shallow-water muddy limestones containing planktonic foraminifera belonging to the P1 zone. While facies suggest that the deposit was emplaced over the inner platform by a single large tsunami, the biostratigraphic assessment of this section and the presence of enhanced concentrations of platinum group elements, such as iridium, in the topmost part of the massive deposit lend support to the hypothesis that this tsunamite is related to the Chicxulub impact in Yucatan. This is potentially the first case of a tropical carbonate platform sedimentary succession recording the Cretaceous-Paleogene boundary event, which provides a new constraint for modeling both the western Tethyan paleogeography and the catastrophic aftermaths of the Chicxulub impact at the end of the Mesozoic Era.

Dinaride evaporite mélange: Diagenesis of the Kosovo polje evaporites

Permian to Triassic age and floored by the various Adriatic carbonate platform units. The tectonic history of the Dinaridic evaporite melange is related to long term burial and Palaeogene to Neogene exhumation processes. Evaporiterocks of the Kosovo polje deposits are associated with carbonates, clastic and minor albitized, subvolcanic, neutralto basic rocks. They are capped by a clayey Quaternary cover of variable thickness, and a several metres thick cavernouscarbonate breccia – rauhwacke. Evaporite rocks show two distinct facies: laminated evaporite-carbonate, composed of evaporite and dolomicrite (± organic matter, pyrite, halite) intercalations, and evaporite-carbonate breccia, composed of fragments of laminated evaporites, carbonate and siltite, cemented by massive gypsum ± sulfur, occurringat the shallower levels and related to the emplacement. The Quaternary cover is composed of 47-88% clayey material, comprising illite, kaolinite and most likely vermiculite, 9-49 % carbonate and 3-4% evaporite minerals. The thickness of the evaporite rehydration zone correlates negatively with the thickness of the overlying Quater nary cover and with the amount of clayey material within it. Rauhwacke are composed of partly dedolomitized dolostone and leachedgypsum fragments, cemented with late stage calcite. Diagenetic processes are related to early diagenesis and the burialphase began with the formation of diagenetic halite from an oversaturated subsurface or surface (lagoon) brine, and was followed by the biochemical reduction of evaporite sulphate to sulfide and formation of pyrite within organic-richcarbonate laminae. These processes triggered early dolomitization (in a shallow burial realm), and the formation of idiomorphic planar-e type of dolomite crystals at temperatures below 50-60°C. Planar dolomite suppressed diagenetichalite. With an increase in burial depth, gypsum dehydrates to anhydrite and when temperatures exceed ~50 °C, precipitation of fine grained non-planar –a type of dolomite began. Halite molds are partly replaced with non-planar-atype of dolomite. During regional uplift and exhumation, anhydrite rehydrated to gypsum under the influence of low-temperature undersaturated fluid (meteoric water), whereas hydrogen-sulfide oxi dized to elementary sulfur, observed as cement in the evaporite-carbonate breccia. Rauhwacke at the uppermost part of the deposit are formed by severe tectonic movements associated with the gypsum-driven dedolomitization process.

Carbon-isotope record and palaeoenvironmental changes during the early Toarcian oceanic anoxic event in shallow-marine carbonates of the Adriatic Carbonate Platform in Croatia

AbstractGeochemical (δ13C, δ18O and Mn) compositions of Lower Jurassic shallow-water carbonates cropping out in Croatia were analyzed to elucidate the impact of the early Toarcian oceanic anoxic event (T-OAE) on the Adriatic Carbonate Platform (AdCP). The bulk-rock carbon-isotope records through the studied sections (Velebit-A, Velebit-B and Gornje Jelenje) are characterized by two significant excursions: (i) an initial positive trend interrupted by a pronounced negative shift (c. 2.5‰) that is followed by (ii) an increasing trend of positive values (up to 4.5‰). A comparison with δ13C trends obtained from well-calibrated sections from other localities in Europe shows that the overall character of the early Toarcian negative excursion is clearly reproduced in the curves derived from Croatian shallow-water deposits, which helps to date the sequences and reinforces the global character of the carbon-cycle perturbation. Lower Jurassic sedimentary successions in the studied area show a gradual deepening trend corresponding to deposition of the Toarcian spotted limestones. Assuming that the distinctive negative excursion in the carbon-isotope curves is synchronous across the AdCP, the contact between the spotted limestones and the underlying beds rich in lithiotid bivalves appears to be diachronous within the study area. The Mn record through the Croatian Velebit-A section and, in particular, the rise in concentration (up to 100 ppm) coinciding with the beginning of the δ13Ccarbpositive shift, reflects a change in the redox conditions in seawater that allowed diagenetic incorporation of reduced manganese into the calcite structure of the carbonate sediment during the onset of the T-OAE.

Upper Turonian–Santonian slope limestones of the Islands of Premuda, Ist and Silba (Adriatic Coast, Croatia)

Upper Turonian-Santonian limestones at three island locations (Ist, Silba and Premuda) in the southwestern part of the Adriatic carbonate platform, record slope deposition based on their sedimentological and palaeontological characteristics.These Upper Cretaceous successions consist of three vertically superimposed lithotypes: (1) pelagic mudstonespackstones, (2) laminated pelagic wackestones-packstones, and (3) bioclastic floatstones-rudstones to packstonesgrainstones with fossils of shallow marine organisms.According to the proximity of the shallow water carbonate platform interior the depositional setting of the slope deposits could be identified as relatively more proximal or distal. The proximal part is characterized by non laminated pelagic limestones with resedimented bioclastic limestones, while the more distal parts have both laminated and nonlaminated pelagic limestones with rare resedimented bioclastic limestones. The resedimented bioclastic limestones represent slope apron deposits. Locally, at Premuda Island, the slope apron includes blocks of laminated pelagic limestones. The depositional environments of the Ist and Premuda profiles could be interpreted as of more distal origin, while those of the Silba profile represents a more proximal part of the slope.

Robustoconus tisljari n. gen., n. sp., a new larger benthic foraminifer from the Middle Jurassic (Early Bajocian) of the Adriatic Carbonate Platform of Croatia

The new larger benthic foraminifer Robustoconus tisljari n. gen., n. sp. is described from Middle Jurassic (Early Bajocian) high-energy shallow-water limestones of the Dubrovnik area in the south-eastern part of the Adriatic Carbonate Platform. Robustoconus represents a large dimorphic agglutinated foraminiferan with a coarse exoskeleton typical of representatives of the Family Hauraniidae. Differences to the allied genera Spiraloconulus ALLEMANN & SCHROEDER and Bostia BASSOULLET are discussed. The occurrence of a further new genus of larger foraminifera provides additional evidence for a high origination rate in the Middle Jurassic. The restriction of Robustoconus tisljari to the Timodonella sarda taxon-range zone highlights its biostratigraphic interest.

Permian deposits and the Permian–Triassic boundary in Croatia: palaeoclimatic implications based on palaeontological and geochemical data

Abstract The Late Palaeozoic deposits in Croatia were derived from the Palaeotethyan shelf areas along the northern Gondwana passive continental margin and consist of mixed carbonate–clastic facies. These sedimentary rocks accumulated in the equatorial area along northern Gondwana under a dominantly hot climate and laid the foundations for the future Adriatic Carbonate Platform (AdCP). Detailed classification and geochemical studies of the Permian and Permian–Triassic deposits in most parts of Croatia are still in progress, especially concerning palaeoclimate and regional palaeogeography. The best preserved Permian outcrops can be found in the Velebit mountain area, including continuous Permian–Triassic sections. Stable isotopes of carbon and oxygen from carbonates, with characteristic positive δ 13 C carb excursion during the Late Permian and negative δ 13 C carb excursion at the Permian–Triassic transition combined with palaeontological and sedimentological data, helped in palaeoclimate estimations and the positioning of the chemostratigraphical Permian–Triassic Boundary (PTB). Sedimentological, palaeontological and geochemical data indicate that deposition in the Permian took place mainly in shallow-water tropical areas under oligotrophic conditions. High carbon isotope ratios in Capitanian carbonate rocks (+4 to +6‰ VPDB) mark the ‘Kamura event’ characterized by temporary cooling, high productivity and burial rate. Evaporites in the central part of the Karst Dinarides and red beds of the ‘Gröden type’ indicate a warm and mostly arid climate. Calculations based on the oxygen isotopic compositions of whole-rock carbonate and fossil samples estimate latest Permian temperatures up to 26 °C.