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Abstract A comprehensive study, including geological mapping, structural and thermochronological analysis, has been carried out on Ivanščica Mountain (NW Croatia), with the aim to reconstruct the tectonic history of the Dinarides, Southern/Eastern Alps and Pannonian Basin transitional zone. Implementation of structural and thermochronological methods enabled a subdivision of Ivanščica Mt. into two structural domains (from bottom to top): Ivanščica Parautochthon and Ivanščica Imbricate Fan and Cenozoic sedimentary cover. In addition, a sequence of deformational events in tectonic history of this transitional zone is proposed, comprising three extensional and four contractional events starting from Middle Triassic until present times. The two oldest deformational events indicate Middle Triassic (D1) and Early Jurassic (D2) extensional pulses and only occur in volcano-sedimentary successions of the Ivanščica Mt. The oldest contractional event (D3) is related to the obduction of a Neotethyan ophiolitic mélange over an Upper Triassic to Lower Cretaceous succession of the eastern margin of the Adriatic microplate, which resulted in thermal overprint of the Ivanščica Imbricate Fan structural domain in Berriasian—Valanginian times (~ 140 Ma). This event was soon followed by a second contractional event (D4), which resulted in thrusting and imbrication of the Adriatic passive margin successions together with previously emplaced ophiolitic mélange, thermal overprint of the footwall successions, fast exhumation and erosion. Apatite fission track data together with syn-tectonic deposits indicate an Hauterivian to Albian age of this D4 event (~ 133–100 Ma). These Mesozoic structures were dextrally rotated in post-Oligocene times and brought from the initially typically Dinaridic SE striking and SW verging structures to the recent SW striking and NW verging structures. The following extensional event (D5) is associated with the formation of SE striking and mostly NE dipping normal listric faults, and ENE striking dextral faults accommodating top-NE extension in the Pannonian Basin. Deformations were coupled with hanging wall sedimentation of Ottnangian to middle Badenian (middle Burdigalian to upper Langhian; ~ 18–14 Ma) syn-rift deposit as observed from the reflection seismic and well data. A short-lasting contraction (D6) was registered in the late Sarmatian (late Serravallian; ~ 12 Ma). The youngest documented deformational event (D7) resulted in reactivation of ENE striking dextral faults, formation of SE striking dextral faults as well as the formation of E to ENE trending folds and reverse faults. This event corresponds to late Pannonian (late Messinian; ~ 6 Ma) to Present NNW-SSE contraction driven by the indentation and counterclockwise rotation of Adriatic microplate. Recognized tectonic events and their timings indicate that Ivanščica was mainly affected by deformational phases related to the Mesozoic evolution of the Neotethys Ocean as well as Cenozoic opening and inversion of the Pannonian Basin. Therefore, the Mesozoic tectono-sedimentary evolution of Ivanščica Mountain proves the paleogeographic affiliation of its non-ophiolitic Mesozoic structural-stratigraphic entities to the Pre-Karst unit of the Dinarides.

Abstract During the Middle Triassic, intensive volcanic activity took place along the eastern margin of Pangea, including the Greater Adria promontory, due to the Neotethyan oceanization. This resulted in the formation of various volcanic and volcaniclastic rock types. The region of NW Croatia, acting as a transition zone between the Southern Alps and the Dinarides, showcases the outcrops of these rocks. The present study investigates the facies of volcaniclastic rocks, the distribution of those facies, formation processes, as well as the genesis of the primary magma to gain a better understanding of the complex geodynamics of this region during the Middle Triassic. Six profiles across the Vudelja quarry front were surveyed using drone imaging and samples were collected for detailed petrographic and geochemical analyses. Two groups of volcaniclastic rocks were identified—mafic and intermediate/felsic. The former is represented by (I) autoclastic effusive facies and (II) resedimented autoclastic facies, while the latter is represented by (III) secondary pyroclastic facies. Mafic volcaniclastics were generated through basaltic effusions in marine environments, fragmentation in contact with seawater, mixing with shallow marine carbonate clasts, and subsequent redeposition in deeper marine areas. The secondary pyroclastic facies (III) consists of a regionally distributed felsic Pietra Verde tuff whose deposits may be related to pyroclastic density currents and syn-eruptive resedimentation by turbidite-like currents. Geochemical data indicate that parental magmas responsible for generating the mafic volcaniclastics had a calc-alkaline composition and originated in ensialic and mature arc settings of an active continental margin. The observed chemical composition is likely inherited from older, arc-related lithologies, associated with the subduction of the Paleotethys Ocean. Parental magmas are thought to have formed during continental rifting of the passive Middle Triassic margins of the Greater Adria through (i) partial melting of the heterogeneous lithospheric mantle, which had been metasomatized during an earlier Hercynian subduction, and (ii) subordinate processes related to the melting of the upper continental crust and subsequent fractionation. Ar/Ar dating on plagioclase separates yielded an age of 244.5 ± 2.8 Ma for mafic volcaniclastics. This aligns well with biostratigraphic ages of felsic tuffs which crop out on a broader regional scale of the Dinarides, the Southern Alps, and the Transdanubian Range. The overlapping ages obtained from radiometric dating of mafic volcaniclastics and biostratigraphic ages of the felsic Pietra Verde tuffs strongly suggest that the Greater Adria region experienced concurrent bimodal volcanism during the Middle Triassic.

Two new species of dasycladal algae are described from the Anisian limestones of the Lika region in Croatia. Griphoporella? speleoluka n. sp. is characterized by very small cylindrical thallus and vesiculiform laterals arranged in close whorls. In consecutive whorls, laterals are positioned one above the other. It differs from other species by smaller dimensions and the arrangement of the laterals. Palaeodasycladus primus n. sp. has cylindrical thallus with whorls of inclined laterals up to the third order. Primary laterals are not completely calcified, producing so-called intusannulation. Trichoform or tubular secondary laterals bear bundles of thin, probably trichoform, tertiary laterals. Both of the new species have been found within typical Anisian microfossil assemblage.

Emended diagnosis of the genus Selliporella and its type-species, S. donzellii SARTONI & CRESCENTI is proposed, based on the definitely proven existence of non-ramified branches in the older (basal) part of thallus and their ramifying in its higher (younger) parts. Based on the differences in the morphological characteristics of branches in the upper thallus parts, the type-species has been split into two varieties: S. donzellii var. donzellii SARTONI & CRESCENTI and S. donzellii var. galaeformis n. comb. Selliporella cornutuformis n. sp. is proposed, characterized by distinctly articulated (segmented) and spiky thallus, with each primary branch bearing a bundle of several trichophorous secondaries. Generic attribution of species originally described as Diplopora johnsoni PRATURLON and Triploporella neocomiensis RADOIČIĆ has been reviewed, resulting in their being unified as the same species, which, according to its newly observed morphological characters, has been ascribed to the genus Pseudoclypeina. Because Diplopora johnsoni has been validly described, Triploporella neocomiensis becomes, taxonomically, the younger synonym of Pseudoclypeina johnsoni (PRATURLON) n. comb.

This paper presents results of fractal analysis of fracture systems in upper Triassic dolomites in Žumberak Mountain, Croatia. Mechanical rock characteristics together with structural and diagenetic processes results with fracture systems that can be considered as fractals. They are scale-invariant in specific range of scales. Distribution of fractures can be than described with power law distribution and fractal dimension. Fractal dimension is a measure of how fractures fill the space. Fractal dimension can be estimated form photographs of outcrops by converting photographs to binary photographs. In binary photo there is only black (rock or fractures) and white (fractures or rock). Fractal dimension is then estimated based on box-counting method. In this paper we present results of fractal analysis from three outcrops. Results are very similar to previous published results from outcrops of dolomites in Slovenia. Obtained fractal dimensions are in range 2,69-2,78 and it depends on how fracture systems are distributed in the outcrop. Lower values indicate smaller number of fractures and higher significance of larger fractures. Higher values indicate distribution of more similar sized fractures throughout whole outcrop. Fractal dimension is very significant parameter in rock fracture system characterisation sense it describes how fractures are distributed in the outcrop. It can be used in discrete fracture network modelling if spatial distribution of fractures is represented with power law distribution.

Montegrella? gracilis n.sp. (Dasycladales) is characterized by thick calcareous envelope and narrow central cavity. Bipartite branches are arranged alternately in consecutive whorls. The primaries are visibly differentiated into a thin, tendril-like stalk in the proximal part and a club-shaped or ellipsoidal inflated swelling in the distal part. The secondaries are poorly visible, of unclear shape and number, with a supposedly common starting point. On the type-locality, the alga occurs within a rich, typically Upper Barremian, algal assemblage. The validity of the genus Montenegrella, being disputed by BARATTOLO (1983), is commented upon by showing the generic attribution of the same or different species either to Suppiluliumaella or to Montenegrella by different authors.

Clypeina lagustensis n.sp. has been found in the Lower Tithonian deposits of the Lastovo Island (Dalmatia, Croatia). It is visually similar, obviously related and in some sections appearing almost identical, to Clypeina jurassica FAVRE, from which it differs by visible swellings and thinning of the central cavity, more pronounced distance between neighbouring whorls of fertile branches, and shape and structure of the interverticillate thallus parts, characterized by having well developed, hairy, sterile branches. These, after emerging from the exit pore, divide into several bundles which form a common turf with a calcareous envelope in the proximal part.

A rich algal assemblage at the Kozica locality, in the northern foothills of Mt. Biokovo, contains, among other forms, Praturlonella salernitana BARATTOLO. In addition, the descriptions of Clypeina bucuri BARATTOLO & ROMANO and C. lucana BARATTOLO & ROMANO are updated, and the originally described Clypeina teakolarae RADOIČIĆ et al., has been tentatively transferred to the genus Falsolikanella GRANIER; hence Falsolikanella? teakolarae n. comb. Falsolikanella? macropora n. sp. is described, characterized by probable metaspondyle growth of clearly phloiophorous branches, differentiated individually into a narrow stalk and very long, markedly widened, outer part. Based on the algal assemblage as a whole, together with benthic and planktonic foraminifers, the stratigraphic position of the algal-bearing level has been defined as Ypresian (lowermost Eocene).

Dissocladella bystrickyi n.sp. occurs in early diagenetic Upper Triassic dolomites, that were deposited in tidal flat and tidal channel environments in the carbonate platform interior. The new alga, assigned to the genus Dissocladella, is characterized by verticillate and distally flattened primary ramifications which give rectangular pores and each bear 5-7 club-shaped secondaries. Its stratigraphic position is probably within the Norian-Rhaetian.

The beginning of Prof. Herak's scientific career was linked to theproblems of the Triass ic stratigraphy. He resolved the Triassic stratigraphyof some parts of the Croatian Dinaridcs by using dasycladalgae.

In the Upper Triassic dolomite deposits of the Žumberak region(west of Zagreb, Croatia) the following local biostratigraphic zonesare distinguished: Clypeina besici Taxon-range zone (Carnian). Aulotortus sinuosus.Interval-zone (Norian), and Triasina hantkeni Taxonrangezone (Rhaetian). Dasycladal algae Clipeina besici (PANTIĆ), Griphoporella curvata (GUEMBEL), Physoporella jomdalensis FLUEGEL & MU and Acciulella sp. are accurately described.

Travertines and calcareous tufa are porous deposits formed by interactions between ambient precipitation of calcium carbonate and resident organisms under different temperature regimes. The distinctions between travertine as thermal spring deposits and calcareous tufa (Kalktuff) as deposits in the springs and rivers at ambient temperatures are fluid. Both represent end points in bio- and physico-chemical calcification processes across a broad gradient of temperature, mineral composition and ion saturation levels. Ecological preferences of micro- and macroorganisms in travertine depositional systems result in the re-distribution of water flow, modification of the landscape and its ecology. The resulting sedimentary structures include new environmental settings with different and diversified biota. They also include different microenvironments of diagenesis with different timings of the processes involved. Conditions in modern ambient temperature travertines of the Plitvice system of lakes and waterfalls are compared with the similar, ancient system of Rocchetta a Volturno, in the central Apennines. Diagenetic alterations are described and illustrated starting with biologically identified primary deposits.

The fossil coralline flora of the Badenian bioclastic limestone outcropping in Northern Croatia is known by the name “Litavac”, shortened from “Lithothamnium Limestone”. The name was given to indicate that unidentified coralline algae are the major component. In this first contribution to the knowledge of the coralline flora of the Litavac, Lithothamnion valens seems to be the most common species, with an unattached, branched growth-form. Small rhodoliths composed of Phymatolithon calcareum and Mesophyllum roveretoi also occur. The Badenian benthic association is dominated by melobesioid corallines, thus it can be compared with the modern maërl facies of the Atlantic Ocean and Mediterranean Sea. Since L. valens still survives in the present-day Mediterranean, an analogy between the Badenian Litavac and the living L. valens facies of the Mediterranean is suggested.

In this paper a new species Salpingoporella tari n.sp. is established, found in a sample of Barremian intraclastic grainstone. It is similar to S. annulata (LORENZ) and S. grudii (RADOI?I?), but visibly more robust. It has few branches per whorl, and the whorls being spaced far apart. The branches are laterally compressed at their distal ends, therefore being vertically elongated. New finding of Salpingoporella cemi (RADOI?I?) gave the new data on the variability of the shape of its branches, and on the precise stratigraphic position of the investigated localities. Besides, Salpingoporella patruliusi BUCUR is illustrated, this being its first find outside Monti Apuseni (south Carpathians) and its geographic range thus encompassing also the Dinarides. Also, a large observed number of specimens of Salpingoporella muehlbergii (LORENZ) with ramified thallus makes that feature both its species-specific and generic characteristic. Quite strongly varying values of various biometric parameters, depending on the position on the thallus in one and the same specimen, raises serious questions as to their reliability and usefulness as a distinguishing factor in comparing both the specimens of one and the same species and of species of the same genus.

Investigations of fossil algae in Croatia began in 1907 with the very first description of the Permian dasyclad Mizzia velebitana from Mt. Velebit by Austrian geologist Richard Schubert. This was followed by Julius Pia’s investigations (1920, 1925), on material given to him by Schubert. The first Croatian researcher on fossil algae was Milan Herak, Pia’s PhD student, with his first paper on Ladinian dasyclads published in 1950. He cooperated with a colleague from the Faculty of Science, Vanda Kochansky-Devidé, who published her first papers together with Herak on Permian and Carboniferous dasyclads in 1959 and 1960. While Herak focused on Triassic algae, Kochansky-Devidé investigated mostly Upper Palaeozoic algae and fusulinid foraminifera. Ivan Guši? comes from the same faculty, and his first paper was published in 1966. Mom?ilo Milanovi?, from the Institute of Geology (the present day Croatian Geological Survey), published his first paper in 1962, focusing mainly on Permian algae. The most prolific researcher Branko Soka? also came from the Institute of Geology; his first papers dated from 1964, and he is still an active researcher. Over time, papers originating from the “Zagreb Algological School” become distinguished by rich and well illustrated fossil material, making numerous contributions to the better understanding of fossil benthic algae from younger Palaeozoic and Mesozoic strata. This was possible not only because of the diligence of the authors, but was also the result of the very thick and well exposed carbonate sequence of the Croatian Dinarides Mts. Rajka Radoi?i? from Beograd (Serbia) also described some taxa from Croatia. Almost all the research refers to dasycladal algae, while other algae are only rarely investigated. Complete references to all papers are given.

The present work enlists as comprehensively as possible the Permian and Triassic Dasyclad algae. For each species, localities and stratigraphic positions attached to the quoted specimens are detailed within the synonymy list .