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The Dinaric Karst is a global hotspot for subterranean diversity, with two distinct peaks of species richness in the northwest and southeast, and an area of a lower species richness in the central part. In this article, we present a species list and describe the ecological conditions of the Lukina jama–Trojama cave system, located in the central part of the Dinaric Karst. This cave system is the deepest and one of the most logistically challenging cave systems sampled so far in the Dinaric Karst. Repeated sampling resulted in a list of 45 species, including 25 troglobionts, 3 troglophiles, 16 stygobionts, and 1 stygophile. Most of the recorded species are endemic to the Velebit Mountain, while three species are endemic to the Lukina jama–Trojama cave system. Within the system, species richness peaks in the deepest third of the cave, most likely reflecting the harsh ecological conditions in the upper parts, including ice, cold winds, and occasional waterfalls. Milder and more stable deeper parts of the cave contain a rich subterranean species community, part of which is associated with two very distinct aquatic habitats, the cave hygropetric and the phreatic zone. The newly recognized hotspot of subterranean biodiversity in the central Dinaric Karst, which has emerged between the two known centers of biodiversity, further highlights the species richness in large cave systems, but also challenges the diversity patterns in the Dinaric Karst overall.

The Dinaric Karst is a global hotspot for subterranean diversity, with two distinct peaks of species richness in the northwest and southeast, and an area of a lower species richness in the central part. In this article, we present a species list and describe the ecological conditions of the Lukina jama–Trojama cave system, located in the central part of the Dinaric Karst. This cave system is the deepest and one of the most logistically challenging cave systems sampled so far in the Dinaric Karst. Repeated sampling resulted in a list of 45 species, including 25 troglobionts, 3 troglophiles, 16 stygobionts, and 1 stygophile. Most of the recorded species are endemic to the Velebit Mountain, while three species are endemic to the Lukina jama–Trojama cave system. Within the system, species richness peaks in the deepest third of the cave, most likely reflecting the harsh ecological conditions in the upper parts, including ice, cold winds, and occasional waterfalls. Milder and more stable deeper parts of the cave contain a rich subterranean species community, part of which is associated with two very distinct aquatic habitats, the cave hygropetric and the phreatic zone. The newly recognized hotspot of subterranean biodiversity in the central Dinaric Karst, which has emerged between the two known centers of biodiversity, further highlights the species richness in large cave systems, but also challenges the diversity patterns in the Dinaric Karst overall.

U ovom radu provedena je kvantitativna i kvalitativna analiza šarenih Košna konglomerata koji izdanjuju na središnjem dijelu Velebita, na području Brušana, uz vrelo Košna voda. Određena je prosječna veličina čestica koje izgrađuju konglomerate i njihova zastupljenost u pojedinim kategorijama Udden-Wentworthove klasifikacije te je procijenjen postotni udio matriksa. Petrografskim mikroskopom određena je litologija čestica i matriksa, a rudnim mikroskopom identificirani su opâki minerali. Uzorci pješčenjaka klasificirani su kao litični areniti, subarkoze te feldspatski areniti, a osim pješčenjaka, konglomerat čine valutice vapnenaca, rožnjaka i kremena. Rendgenskom difrakcijskom analizom utvrđeno je da crvenu boju pješčanog matriksa konglomerata uzrokuje hematit. Temeljem provedenih analiza i terenskih opažanja, Košna konglomerati određeni su kao petromiktni klastpotporni i matrikspotporni konglomerati, mjestimično brečo-konglomerati srednjopermske starosti čiji materijal vrlo vjerojatno potječe iz izdignutog Hercinskog gorja i taložen je u marinskom okolišu. In this thesis a quantitative and qualitative analysis of multicoloured Košna conglomerates has been conducted. These conglomerates are found in the middle part of the Velebit Mt., in the Brušane area, along the “Košna voda” creek. The average particle size and their percentage in particular categories of the Udden-Wentworth classification were determined, and the percentage of matrix content was estimated. Particle and matrix lithology were determined using a petrographic microscope, while the present opaque minerals were identified using an ore microscope. Sandstone samples are classified as lithic arenites, subarkoses and feldspathic arenites. Beside sandstones, the conglomerates consist of limestone, chert and quartz pebbles. X-ray diffraction analysis showed that the red colour of conglomerate matrix is caused by hematite. Based on the conducted analysis and field observations, the Košna conglomerates are defined as Middle Permian petromict clast-supported and matrix-supported conglomerates, locally breccia-conglomerates. The material very likely originated from the uplifted Hercynian Mountains and was deposited in a marine environment.

Although several types of glacial landforms and deposits were described from different parts of the Croatian Dinarides, up to date there are no quantitative glacial chronological data. Here we present the first cosmogenic 36Cl glacial chronology from the Southern Velebit Mt. from a moraine complex known as the Rujanska Kosa. We sampled four limestone boulders and used 20 mm ka−1 erosion corrected ages, as the study area is composed of well-karstified carbonate deposits and located in one of the highest precipitation regions of Europe. The inner Rujanska Kosa ridge yielded an age of 20.7 ± 2.2 ka for the retreat of glaciers in that part of Velebit Mt. A slightly older age was measured from the outer ridge on the left-lateral part of the Rujanska Kosa, which dates back to 22.7 ± 2.7 ka ago. Whilst the ages between inner and outer ridges overlap within error, we can place an age difference between the two moraines to be between 0 and 6.9 ka, supported by the geomorphic evidence that the latter is older. Although we could not perform any geomorphological work higher up in the Rujno paleo-ice field due to the remnant minefields, our results may indicate a Late Pleistocene (i.e. la st glacial maximum) retreat of ice from the Southern Velebit Mt. Despite the small number of valid samples, acquired age data on glacial landforms in Southern Velebit Mt. are in accordance with ages from several other Mediterranean mountain ranges.

The morphostratigraphical record of paleoglaciers is an important paleoclimatological and paleoenvironmental archive in Quaternary studies. In the Mediterranean region, most of the glaciers during this period were hosted in carbonate mountains, where establishing a glacial chronology is complex. Diagenetical processes such as cementation, dissolution and increase of organic content, together with the carbonate nature of the deposits, prevents the application of most of available absolute dating method to accurately date carbonate tills. As well, processes such as percolation of water through sediment, propagation of rootlets and carbonate corrosion/surface denudation are impediments to obtain suitable glacial chronologies. Radiocarbon analyses of calcite cements are known to be inaccurate due to dead-carbon contribution from dissolved carbonate bedrock. U-series dating of carbonate cements is not applicable since: (1) cements generally have several phases of growth ranging from the time of deposition to present and (2) more importantly, a closed carbonate system is unlikely to be preserved, implying isotopic leaching. Due to lack of significant amounts of quartz and feldspars in the bedrock carbonates OSL dating is not applicable to carbonate tills. Exposure dating could be applicable to some till boulders by in situ produced cosmogenic nuclides using 36Cl, but surface weathering and denudation rate must be taken into account. For this reason, 36Cl burial dating is likely to be the best option to reproduce accurate chronologies. Here we show a study of a carbonate tills from southern part of Velebit Mt. were we evaluate their depositional environments and the diagenetical processes that affect them.

Detailed outcrop-scale analysis of fault-slip data, in combination with data presented on published geological maps, were used for a reconstruction of the structural architecture and tectonic evolution of the Velebit Mt., the most prominent geomorphological structure in the central part of the External Dinarides in Croatia. The analysis of kinematic indicators recorded by major fault planes indicates the prevalence of dip-slip and top-to-NE motions, verifying that these faults are NE-verging thrusts rather than NE-dipping normal faults as previously thought. Consequently, we challenge earlier tectonic models that interpret the Velebit Mt. structure as a SW-vergent antiformal stack or thrust duplex formed above the major NE-dipping thrust system (TARI KOVAČIĆ & MRINJEK, 1994) or as a complex transpressional structure formed during the late-orogenic escape tectonic phase along an inherited crustal fault zone (GRANDIĆ et al., 2004 ; KORBAR, 2009). Instead, we use the concept of a passive roof duplex within a triangle structure. Thereby, the Velebit structure represents a stack of NE-verging backthrusts formed above a SW-vergent compressional duplex. Our interpretation was recently tested by BALLING et al. (2017) by construction of forward modelled balanced cross sections. Additionally, we analysed a large set of fault-slip data comprising more than 1000 measurements collected in the carbonate breccia exposed along the SW mountain slope at about 60 measurement sites. Curiously, the majority of recorded fault-slip data comprise structures with a normal sense of shear indicating orogen-perpendicular (NE-SW) to orogen-parallel (NW-SE) extension. According to the very good preservation and high frequency of occurrence, these extensional structures may have played an important role in formation of the extremely voluminous carbonate breccia exposed along the SW mountain slope. Accordingly, we propose that these structures resulted from a state of stress characterised by radial extension induced by gravitational collapse and spreading as a result of the uptilting of the SW-dipping Velebit monocline. Therefore, our interpretation is only partly in accordance with KORBAR (2009) who suggested that divergent extension and gravity gliding was a major mechanism in formation of the carbonate Jelar breccia in general.

Solitary limestone blocks and groups of blocks occur on Risnjak and Velebit Mountains and on the northern Adriatic islands of Krk and Rab. Previous researchers have interpreted some of these as a) erratic blocks, b) corrosional remnants, or c) rockfalls. We have studied their mode of occurrence and composition, and revised previous interpretations of their origin in the light of transport mechanism and depositional processes. After analyzing the context of the block positions and the physical processes responsible for their emplacement, and taking into account their sedimentological context (their association with glaciogenic sediments), we herein propose a glacial origin for most of these blocks. However, some blocks are indeed shaped by sub-soil corrosion, as evidenced by their structure. The interpreted erratic blocks on the inner northern Adriatic Sea islands document the presence of middle Pleistocene glaciation of Dinaric Mountains though not its maximal extent, which is still unclear as the ice terminus was in the area that is inundated by postglacial rise of Adriatic Sea. The reconstructed ice cap area, which extended along the coastal mountains from Risnjak Mt. to south Velebit Mt. and across the range from Lika Polje to Rab Island, is conservatively estimated to be 5400 km2.

Glacial sediment is an important paleoclimatological and paleoenvironmental archive. In the Mediterranean region most of the Quaternary glaciers were hosted in carbonate mountains. Diagenetical processes in carbonate sediments tend to impact preservation of glacial features and complicate the establishment of accurate chronologies. This paper presents a sedimentological study of a paleoglacier hosted in the carbonate Velebit Mountain, Croatia. Three carbonate tills were studied in order to evaluate their depositional environments and the diagenetical processes that affect them. The tills were selected from lateral moraines of different glacial stages of the paleoglacier and they are interpreted as lodgement and melt-out tills. Diagenetical processes such as cementation, dissolution and increase in organic content were enhanced by the percolation of water through the sediment and the propagation of rootlets. This research demonstrates the importance of understanding the diagenetical processes affecting carbonate tills after their sedimentation. Studies like this are an essential research stage prior to conducting geochronological and paleoclimatological interpretations based on paleoglaciers in carbonate regions.

In the paper 21 new bryophyte species for the flora of Croatia are presented. They originate from three regions in Croatia: Papuk Mt, Velebit Mt and Gorski kotar. For each species exact localities, habitats, and other data concerning conservation status, general distribution and distribution in the Balkans are provided.

An abundant and diverse Late Carboniferous brachiopod fauna from Velebit Mt. (Croatia) comprises 63 brachiopod taxa dominated by Productida and Spiriferida. The Spiriferinida, Athyridida, Orthotethida and Rhynchonellata are less common, while the Orthida, Dictyonellida and Terebratulida occur in very small numbers. Brachiopods are mostly preserved as casts and moulds in shales, limestones and sandstones. Associated fusulinid foraminifera and calcareous algae indicate a Kasimovian to Gzhelian age for the brachiopod–bearing deposits. The global biogeographic distribution of brachiopod taxa indicates the probable seaways and brachiopod migration routes, along the Euramerican shelves.

A new finding of rare and endangered plant species Eleocharis carniolica in Croatia was reported. Older records were discussed and protection measures of the locality on Velebit Mt are presented.

The section of Middle Permian deposits on the Velebit Mt., Croatia, is located 100 km from the nearest industrial city in a mountain roadcut which exposes thick succession of shales interbedded with shallow-marine dolomitized limestones of reefal and peri-reefal origin (Fig. 1) [1]. Glass spherules [2] were found in sediments of the Neoschwagerina craticulifera biozone (Late Roadian/Early Wordian) during recent study of intra-Guadalupian ecological crisis and recovery. After the initial discovery, additional sampling and sub-sampling was done along the whole length of the outcrop to check for possible contamination and to find horizon with most spherules. Spherules were found only at 2 of 10 sampling locations ; in "basal" black shales 5.5 m below the first reefal limestone in the succession, and in a shale bed 1.5 m below the second reefal limestone (Fig. 2 in [2]). Morphology and types of spherules: The spherules are glass-transparent, essentially colorless, but few are tinted yellowish to brownish (Fig. 2). The majority of spherules are perfect spheres 180 – 620 µm in diameter, whereas ellipsoidal glass grains are fewer, but up to 1090 µm long. Teardrop-shaped glassy grains are rarest and up to 600 µm long. Some spherules are made of massive glass, but some contain small vesicles, sometimes aligned in "laminae". Some broken spherules reveal their homogenous structure, whereas some are hollow in their centers - resembling a glass balloon. Some transparent spherules are partly coated with thin white amorphous crust as a kind of "cement" (Fig. 2). The same material also occurs as larger chunks, pitted with holes which probably nested glass spherules, herein referred to as "matrix". The brownish spherules and droplets are much fewer and are not covered with the "cement" crust. A number of transparent spherules are fused together making clusters, usually composed of a larger spherule with several smaller ones attached. Research methods: Spherules and their "cement" were analyzed at the Rudjer Bošković Institute Accelerator facility using PIXE Spectroscopy in high vacuum at the ion micro-beam end-station. The 2 MeV proton beam of about 50 pA current was focused to several µm in size and positioned on selected areas on samples. X-rays from the selected areas of the samples were collected by PGT Si(Li) detector with 8.4 µm thin Be window and Al "funny filter" (75 µm thick with 2.4 % hole area). Quantitative analysis of collected PIXE spectra was performed using fundamental parameter approach with GupixWIN Software [3]. Iterated matrix solution algorithm was used assuming that all the elements are present as oxides with the option of normalization to 100%, except in the case of metallic droplet where it was assumed that invisible elements were not present. Glass standard NIST 620 was used for calibration. Chemical composition of spherules: Two types of spherules were analyzed ; a) transparent spherules and ellipsoidal glass grains, and b) brownish-tinted spherules. These were complemented by analysis of the "cement" crust, "matrix", and the teardrop grain. Composition of analysed spherules and glass grains in wt % transparent brownish "cement" "matrix" Na2O 15.1-21.27 10.68 0.00-1.13 0.73* MgO 2.69-3.43 2.02 0.00-0.65* 0.51*-1.58 Al2O3 1.13*-5.40 2.83 7.44-13.72 3.63-14.62 SiO2 71.46-83.65 69.74 4.17-6.20 1.09*-11.94 SO2 0.13*-1.88 - 0.00-0.32* 0.26* Cl 0.00-0.043 0.14* 0.00-0.14* - K2O 0.13*-0.82 - 0.58*-0.92* 0.65* CaO 10.91-14.55 20.71 5.60-72.20 62.82-74.15 TiO2 0.03*-0.16* 0.14* 18.35-78.59 15.63-21.69 MnO 0.007*-0.1* 0.35* - 0.099* Fe2O3 0.11*-0.37 - 0.84-2.83 0.86 * measured at the detection limit Discussion: The table shows quite consistent chemical composition of transparent spherules and ellipsoidal grains, regardless of their size and shape, which differs from the composition of brownish spherules, "cement" and "matrix". The chemical composition shows that majority of transparent glass spherules are made almost entirely of Si and Ca oxides, whereas brownish spherules are enriched in Ca (63%), but depleted in Na (-41%) and Mg (-34%) oxides. The "cement" crust and "matrix" have similar compositions. The "crust" has very wide range in the amount of CaO, but the highest value is similar to that of the "matrix". The "crust" and "matrix" are enriched in Ti oxides, but "cement" has significantly higher maximal concentration (78.59 %). Both "crust" and "matrix" are low in Si and Na oxides. The teardrop grain is essentially made of Fe (84 %) with small addition of Ti (3%). The chemical composition of spherules from the "basal" shale and from the higher horizon below the second reefal body [2] is within the measured range, with very small variation. The compositional uniformity of glass spherules at the studied section documents their identical origin and reworking from the "basal" shales. The stratigraphic position of spherules within the Guadalupian Neoschwagerina craticulifera zone, possibly Roadian/Wordian boundary, which is characterized by ecological crisis at the studied section, opens a question of their origin. Chemical composition of the majority of spherules indicates rather high content of Si and Ca and very low content of Ti oxides (at the detection level), which significantly differs from the composition of "cement" and "matrix" which are rich in Ca and Ti oxides and depleted in Si, and the droplet which is essentially made of Fe. Consequently, the origin of spherules and other glass grains found at the Velebit Mt. Middle Permian section is unrelated to the Emeishan flood basalts, which differ chemically and in age [4]. The presence of shocked quartz grains [2] and chemical diversity of spherules and glass grains in the studied section may be explained by an asteroidal impact into a mixed sedimentary target, possibly offshore to account for the formation of tsunami deposit. Conclusion: The difference in composition of glass grains, spherules and "matrix" indicates their condensation from melts of different chemical compositions which were immiscible in reduced gravity, and originated from melting of different source-rocks. The "matrix" is Ca-rich and Si-poor, whereas the transparent spherules are Si-rich and Ca-poor, so both inevitably originated from different source-rocks which might have been carbonates and siliciclastics, respectively. However, the Fe-rich melt which formed the teardrop grain (micro-tektite) may bear geochemical signature of a space body during its passage through the atmosphere, but for its characterization more research is still due. Reworking of spherules from the "basal" shales must have occurred during subaerial erosion of the exposed spherule-rich shales during relative sea-level falls and resedimentation of the debris in shallow anoxic lagoons. References: [1] Sremac J. & Marjanac T. (2003) in Field Trip Guidebook, 22nd IAS Meeting of Sedimentology - Opatija, 147-150. [2] Marjanac T. et al. (2015) This volume, [3] Campbell J.L. (2010) in Nuclear Instruments and Methods in Physics Research Section B – Beam Interactions with materials and atoms B 268, 3356-3363, [4] Shellnutt J. G. & Jahn B.-M. (2011) Jour. of Volcanology and Geothermal Res. 199, 85–95.

Establishing chronologies of paleoglaciers in carbonate regions is complex due to multiple processes that alter the till geochemical, sedimentological and morphological properties. Here we presented a study of the depositional environments and the diagesesis of three different tills from a carbonate region. One of the tills was characterized as a lodgement till and the other two as melt out tills. The lodgement till has a limited permeability and the primary properties of the sediment are preserved. On the other hand, the melt out tills have a significant permeability and water percolation caused significant dissolution of some carbonate pebbles, although calcite cements have also been identified. There is a large spatial variability in the dissolution and cementation processes in relation to the distribution of clay and silt fraction that prevents the water flow. A substantial increase of organic matter took place in the melt out tills due to the rootlets propagation through porosity. On the contrary, the limited porosity of the lodgement till prevents the penetration of roots aside from weathered till sectors. The study of the morphostratigraphy, sedimentology and diagenesis of these tills has highlighted different potential problems that may arise at the time of establishing their chronology. Thus, erosion processes in some tills and the weathering rates of these carbonates anticipate accuracy problems in case of the use of 36Cl dating method. The U-Th method in calcite cements is not recommended since the water percolation implies an open system of these tills. Finally, the increase of organic matter prevents to identify primary organic particles that could be used for radiocarbon analyses. This research has identified potential problems prior to apply any dating method. We recommend carrying out similar studies in carbonate regions before conducting paleoglacier chronologies in order to identify and minimize their inaccuracy.

Biotic crisis at the Guadalupian/Lopingian boundary is well known in Neotethyan realm, but Permian section of the Central Velebit Mt. (External Dinaric Alps) in Croatia (Fig. 1) bears evidence of an earlier, intra-Guadalupian event which is biostratigraphically located in Neoschwagerina crati-culifera biozone (Late Roadian/Early Wordian). The studied section comprises thick black shales interbedded with reefal limestones and calcareous clastics composed of peri-reefal skeletal debris. The reefal bodies are interpreted as morphological and ecological cement reefs draped with peri-reefal clastics [1] and bounded by erosional bases and tops. Spherule-bearing horizons: Glass spherules were found at two horizons ; in black shales 5.5 m below the first reefal limestone unit (A), and in a shale bed 1.5 m below the second limestone unit (B, Fig. 2). The first spherule horizon is 0.3 m thick "basal" cross-bedded shale ; thin-bedded in the lower part and foliated in the upper, that underlies deformed shales which were interpreted as a submarine slump or possible large water-expulsion structure. Spherules occur in first 25 cm, and disappear in the uppermost 5 cm of the bed. No spherules were found in shales within the possible dewatering structure, nor in several other sampled horizons. The "basal" shales are marked by pronounced change in spongal communities ; calcisponges predominating below and silicisponges above, and comprise marine micro- and macrofauna (dominantly foraminifers, dasyclad algae and sponges). This shales also comprise well rounded lithoclasts (oolitic limestones, afossiliferous limestones, dolomites) 0.25 to 10 mm in diameter, and mineral debris (quartz, plagioclase and feldspars). Some quartz grains are shocked, with two sets of PDF's at sharp angles. The shales are fissile, compacted, whereas one horizon in approximately middle position within the unit is extremely vesicular. The voids are open and were presumably formed by the escaping gas (? methane). No other shale horizon on the studied outcrop shows the same structure, neither the compositional diversity of the spherule-rich shale unit. Morphology of spherules: Spherules (Fig. 3) are commonly clear glass spheres 180-620 µm in diameter. Several glass spherules may be fused together making relatively large clusters of smaller spheres (30-60 µm in diameter) surrounding a bigger one. In addition to spheres, there also occur large irregular ellipsoidal glass grains which attain more than 1000 µm in length, and 600 µm long teardrop brown glassy grains. Most spherules are water-transparent, but few are yellowish to brownish-colored. Spherules are commonly massive, but some are hollow in the middle, and some comprise tiny vesicles which are sometimes arranged in "laminae". The surface of vesicle-rich spherules is pitted with shallow degassing craters. Some spherules are partly covered by thin white amorphous "cement" crust (Fig. 2 in [3]). Morphologically identical are grains of homogenous white dull glass which host spherule casts. Composition of spherules: The transparent glass spherules are composed primarily of Si and subordinate Ca and Na oxides with minor compositional variations. The yellowish-tinted spherules are slightly richer in Ca, but the content of Na and Mg oxides is lower by 41-34% respectively, whereas the teardrop grain is made almost entirely of Fe. The white "cement" crust is made of Ca with high percentage of Ti, but depleted in Si oxides. The "matrix" is also largely made of Ca, enriched in Ti (but less than "cement" crust) and low in Si oxides [2]. Spherules from different horizons within the "basal" shale unit (sub-sampling was ca. 4 cm apart) have identical Si-rich chemical compositions, morphology and association with Ti-rich crusts, which all point to the same source/event. Discussion and conclusion: The spherule-rich shale unit is interpreted as possible tsunami mass-flow deposit because of its structure, mixing of debris from terrigenous sources (outsized lithoclasts) and shallow marine source (foraminifera, dasyclad algae, sponges, gymnocodiaceans) which was below the depth preferred by the reef builders (sponges and encrusters) [3]. The vesicular shale horizon may have been formed by the escaping gas formed by decay of trapped organic (? plant) matter. Consequently, the spherule-rich shale is interpreted in terms of single-event bed which was formed semi-contemporaneously with the spherule-producing event. The teardrop grain rich in Fe was formed as a melt was falling through the atmosphere, whereas perfect spherical and spheroidal Si and Ca-rich spherules were formed by rapid condensation and cooling of the melt which trapped escaping volatiles (Oxygen?) in tiny bubbles in the spherule interior, only few escaping at the surface. The compositional differences of spherules and amorphous Ca and Ti-rich glass indicates their origin from different melts created by the same event, very likely an impact into carbonate and siliciclastic target rocks, the interpretation also supported by presence of shocked quartz grains. The target must have been oceanic to account for generation of a tsunami which reworked debris from marine and terrigenous sources and dispersed spherules throughout the thickness of the resultant shale bed. The occurrence of spherules at two horizons, below the reef bodies "A" and "B", and in small number at several other sampling locations is very likely a consequence of reworking, because reefal bodies are underlain by erosional surfaces probably caused by regional sea-level falls. References: [1] Sremac J. & Marjanac T. (2003) In: Field Trip Guidebook, 22nd IAS Meeting of Sedimentology - Opatija, 147-150, [2] Čalogović M. et al. (2015) This volume, [3] Sremac J. (1988) Mikrofosilne zajednice srednjeg perma Velebita. Doctoral Thesis, University of Zagreb.

On the central part of the Velebit Mountain the traces of the Pleistocene glaciation have been found. The domination of the dissected relief, characterized by numerous elevations and depressions, in the conditions of low temperatures and richness of snow precipitations during Pleistocene were a very good predisposition for the glaciation development on the central part of the Velebit Mt.

U terenskom vodiču se opisuju stijene i facijesi u starosnom rasponu od srednjeg Perma do mlađe Jure koji su otkriveni na području srednjeg velebita.

The objective of this study is to present the first results of research conducted in the 1421 m deep cave system Lukina Jama during 2010 and 2011. The cave is situated in the area of Hajdučki kukovi in Northern Velebit National Park (Croatia) and is the deepest cave system in the Dinaric karst. In situ measurements of microclimate parameters and radon concentrations were performed at 20 measuring points. Two temperature gradients were detected: dT/dh = -3.65 ± 0.3oC/100 m from the entrance to a depth of 200 m and dT/dh = +0.39 ± 0.04oC/100 m to the bottom of the cave. Ice and snow dynamics influenced microclimate parameters to a depth of 200 m. Mean radon concentrations changed with distance, from 200–600 Bq/m3 in the upper cave sections, to 1139 Bq/m3 in the lower sections. This increase is in correlation with the partial pressure of carbon dioxide, which is an important factor in a variety of geochemical processes occurring in caves. Speleothems occur rarely in the deep caves of Mt. Velebit, and therefore the microclimate and geological conditions at the locations where they occur. As reported here, microclimate conditions below a depth of 220 m to the bottom are very stable, so speleothems are good candidates for further paleoclimate investigation.

Varved lacustrine sediments of the South Velebit Channel coast, eastern Adriatic Sea, comprises fossil macroflora which is the evidence of forested lake banks. Fossil macroflora was taxonomically determined and the leaf morphology was used for paleoclimate reconstruction. Vegetation grew near proglacial lake at the time of advance of major ice tongue from the Velebit Mt. range. The age of studied sediments is determined by U-series dating of secondary calcite in the overlaying lodgement till, providing the minimal age of >350ka. The ice advance is therefore attributed to the MIS 12. Paleoclimate reconstruction yielded paleotemperature values between 5.51 ± 2.86°C and 3.89 ± 2.72°C and mean annual paleoprecipitation of 679 mm. The data reflects the climate conditions in the foreland during the advance of an active ice tongue sometime before the Middle Pleistocene glacial maximum. Lake sediments are varved with presence of dropstones. Varves are complex which indicates differentiated seasons with episodes of temperature oscillations. Leaves are occurring at the base of winter clay laminae. The ice tongue extended at some point all over the lake, eroded the lake bed and glaciotectonically deformed the studied lake sediments. The determined taxa comprise Taxodium sp., Zelkova sp., Quercus sp., Castanea sp., Fagus sp., Liquidambar sp., Tilia sp., Acer cf. rubrum, Pterocarya sp. and Buxus sp. Most of the determined taxa form climax fitocoenosis which means that the vegetation around the lake was zoned and well developed at the time of the ice advance. This indicates climate change so rapid that the vegetation succession didn't have time to compensate for the newly formed conditions. The ice buildup is therefore presumed to last few hundreds of years.

Permian deposits in the Velebit Mt. area (Croatia) derive from the epeiric platform which existed in equatorial area along northern Gondwana. Late Permian is characterized by dolomites encompassing three relatively thin zones of dark limestones (together named as Velebit Fm., Flügel, 1977). Late Permian dolomites in the Velebit Mt. area are mostly early-diagenetic. The deposition took place in subtidal, intertidal and supratidal environments, as a result of global trends in sea level oscillations. Latest Permian Transitional Dolomite (TD) includes complete remains and bioclasts of algae (dasycladales, solenoporaceans, gymnocodiaceans), foraminifera (Earlandia, Ammodiscus, Glomospira, Tuberitina, Pachyphloia, Globivalvulina, Permodiscus, Staffela, Hemigordius, Lagenidae), with fragments of sponges, ostracods, gastropods, echinoderms and brachiopods. Conodont remains have not been found. The lithologic boundary between Transitional Dolomite and overlying Sandy Dolomite (SD) is marked by a sudden occurence of ooids and siliciclastic grains. Even though it was previously considered as the chronostratigraphic PTB, it represents latest Permian regressive phase marked by an enrichment in concentrations of most major, trace and rare earth elements, followed by the Last occurence of the Permian fossils (LPE) in the lower part of the SD unit (Fio et al., 2010). Chemostratigraphic Permian–Triassic Boundary (PTB) is set within the SD unit marked by the parallel negative carbon isotope excursions in carbonate and organic carbon and changes in element concentrations. First fossil remains after the PTB belong to foraminifera Earlandia sp., which is found together with the pyrite framboids just above the chemostratigraphic boundary, pointing to suboxic and anoxic conditions (Fio et al., 2010). Up in the column, only probable cyanobacterial mats and juvenile mollusc remains have been found within the SD.

Land flora was collected at several sites in the Velebit Mt. Flora is Carboniferous in age, dominantly consisting of pteridosperms and primitive gymnosperms. Samples are stored in collections of Croatian Museum of Natural History and Faculty of Science.

Middle Pleistocene moraines of Southern Velebit Mt. comprise karstified clasts which range from 0, 5 m up to more than 10 m in diameter. These are represented by lithologies which are common on the Velebit Mt. ; Upper Cretaceous limestones and Jelar-breccia of Paleogene-Neogene age. The moraines are several meters to several tens of meters thick and are composed of debris in grain contact, with interspaces locally filled with fine-grained matrix, and locally cemented by sparry calcite. The calcite cement is secondary infill of openwork moraine and was dated by U-Th series providing minimal age of 159.8 ka. The karstified clasts in these moraines are usually rotated and karren are abraded. Sometimes there are younger karren developed over the older forms, but both systems are today in a rotated position. Karstification of these clasts pre-dates formation of moraines which are attributed to the Riess glacial. These rillenkarren and rinnenkarren were possibly formed during the Mindel-Riess interglacial on nearby mountain tops, and were eroded and transported by glacial ice. Thus, recognition of karstified debris in moraines provides evidence of pre-middle Pleistocene karstification of the Dinaric Mountain range.

Surfaces showing evidence of exposure to subaerial conditions are frequent in particular parts of shallow-marine Adriatic-Dinaridic carbonate platform succession formed during Early Jurassic. Most of these surfaces represent hiatuses below biostratigraphic resolution and detailed sedimentologic and diagenetic study is needed to distinguish these small scale discontinuities from simple bedding planes and evaluate the environmental change involved (CLARI et al., 1995 ; HILLGÄRTNER, 1998). During Early Jurassic Adriatic-Dinaridic carbonate platform (ADCP) was a carbonate ramp with extensive shallow inner-ramp environments (ČRNE & GORIČAN, 2008), the area that small sea-level changes will mostly affect and therefore has the greatest potential to record environmental changes. Two sections of Lower Jurassic carbonate succession that belonged to the inner part of the ADCP, were studied in detail on a centimetre scale. Both sections are situated in the Velebit Mt. area - Kubus (82 m thick) and Mali Alan (83 m thick). Today, these localities are 50 km apart. The under- and overlying rocks of each bedding plane and rocks from the bedding planes itself were studied and detailed bed-by-bed logs recording stratigraphical data, sedimentary structures and textures obtained from field and laboratory investigations are made. Altogether 242 thin sections were made and analysed under the microscope to determine microfossil content and depositional facies. A correlation of the two sections is based on facies architecture (both logs show arrangement of facies change into shallowing- and coarsening-upward cycles (BUCKOVIĆ et al. (2001)), biostratigraphy, exposure surfaces and one bed marker, which enabled correlation of the two sections on a bed level. Combining data collected in the field with microfacies analysis from thin sections, three types of surfaces containing features of diagenesis in subaerial conditions are observed and classificated sensu HILLGÄRTNER (1998): i) Paleosols are recognized as emersion surfaces showing pedogenic features. In the field, these surfaces are of irregular relief, often show brecciated appearance due to the dissolution processes and rhizoturbation during exposure. Contact with the next bed is mostly sharp because of the erosion during the following marine flooding. The alteration of limestones is seen as reworked lithoclasts within brownish yellow clayey calcareous matrix. Microfacies analysis reveals circumgranular cracking, solution vugs, root-related structures and nodular texture. ii) Exposure surfaces showing fenestral fabric, sheet cracks, birdseyes, circumgranular and desiccation cracks (seen in the field, as well as in thin sections), i.e. diagenetic features that are result of repeated sediment drying and wetting in subaerial conditions are called inter- to supra-tidal hardgrounds (HG). Occasionally, upper bedding planes show strong reddish-brown staining by aluminium and iron oxides (possibly limonite and hematite) pointing to oxidation during subaerial exposure, but the possibility that this alteration is due to the outcrop weathering has to be taken into account. iii) Bedding surfaces showing meteoric influence visible in thin sections as recrystallization of skeletal and nonskeletal particles and cements are called diagenetic discontinuities. Recorded logs are of Middle Sinemurian to Early Carixian age (FADs of Lituosepta recoarensis CATI, Orbitopsella primaeva HENSON and Orbitopsella praecursor GÜMBEL are identified) (VELIĆ, 2007). Deposits of Middle to Late Sinemurian age show little evidence of subaerial diagenesis: rare diagenetic DSs and inter- to supra-tidal HGs are observed at both localities. Succession of Late Sinemurian age contains several significant paleosols at Mali Alan which are well correlated with contemporaneous exposure surfaces (inter- to supra-tidal HGs and paleosols) at Kubus locality. Several diagenetic DSs and inter- to supra-tidal HGs are recorded at both localities in deposits belonging to Latest Sinemurian to Earliest Carixian. Three types of exposure surfaces are differentiated. They indicate periods of generally shorter-lived supratidal regime, but compared to each other, paleosols and inter- to supra-tidal HGs point to relatively longer exposure in respect to diagenetic DSs. Late Sinemurian is determined as the time of the most significant and frequent exposures of the studied part of the inner platform area. Interval with the most prominent exposure features extends laterally over 50 km and shows that recognition of exposures can be useful in correlation of shallow-marine platform strata and obtaining additional information of platform evolution. Repeated periods of generally shorter-lived supratidal regime may be related to a single regressive event that occurred in the studied area, but to confirm this presumption, study of a wider platform area of the ADCP is required. BUCKOVIĆ, D., JELASKA, V. & CVETKO TEŠOVIĆ, B. (2001): Facies Variability in Lower Liassic Carbonate Successions of the Western Dinarides (Croatia).- Facies, 44, 151-162. CLARI, P.A., DELA PIERRE, F. & MARTIRE, L. (1995): Discontinuities in carbonate succession: identification, interpretation and classification of some Italian examples.- Sedimentary Geology, 100, 319-341. ČRNE, A.E. & GORIČAN, Š. (2008): The Dinaric Carbonate Platform margin in the Early Jurassic: a comparison between successions in Slovenia and Montenegro.- Boll. Soc. Geol. It., 127/2, 389-405. HILLGÄRTNER, H. (1998): Discontinuity surfaces on a shallow-marine carbonate platform (Berriasian, Valanginian, France and Switzerland).- J. of Sed. Res., 68, 1093-1108. VELIĆ, I. (2007): Stratigraphy and Palaeobiogeography of Mesozoic Benthic Foraminifera of the Karst Dinarides (SE Europe).- Geol. Croatica, 60/1, 1-113, Zagreb.

The peak areas of the Velebit mountain range display an interesting periglacial geomorphology. The appearance of forms is the result of the interdependent geological, geomorphologic, climatic, vegetational and pedological characteristics of the area. The structural and lithological properties of the rock complex, and the inclination of the slope, play a significant role in periglacial relief modelling. Climatic elements are also important, as they influence the intensity and duration of the processes. Low temperatures and relatively high precipitation during the last ice age (Würm III), served to intensify the activity of periglacial processes and relief modelling of the entire Velebit area. Nivation and cryofraction are the predominant periglacial processes which are represented by snow avalanches and stone streams. Air temperatures and soil temperatures (at 30, 60, 90 cm depth) were measured, presented and reviewed, together with other attributes and the slope inclination of the area. The interactions between ground temperature, snow cover and wind patterns play important roles in frost action. In addition to slope inclination, the penetration of warm winds (jugo) and warming of snow on the NE slopes are also important factors in destabilizing the snow cover and triggering avalanches. Snow avalanches are most intensive on slopes with declinations from 35° up to 50°, especially on the parts without vegetation cover.

The uppermost Permian and Lower Triassic dolomites of the Velebit Mt., Croatia, were deposited on the shallow-water carbonate platform of the western Paleotethys, close to the equator. The deposits are composed of two informal lithostratigraphic units – Upper Permian Transitional Dolomite and uppermost Permian and Lower Triassic Sandy Dolomite. Detailed palaeontological and geochemical characteristics of the analysed units are described by Fio et al. (submitted). Late Permian whole rock 18Ocarb, with respect to V–PDB, vary from –3.2 to –1.3‰ (average–2.6±0.4‰) and Early Triassic range from –3.2 to –2.2‰ (average–2.7±0.3‰). The oxygen isotopes are prone to diagenetic change if the deposits are influenced by metamorphic processes or hydrothermal fluids. Regarding very low and negative correlation of carbon and oxygen isotopes (r2 = –0.04, n = 111) and narrow range of oxygen isotope values (1.9‰) we can assume the primary magnitude of the isotope excursions. According to the formula t(°C) = 16.1 – 4.64(c–w) + 0.09(c–w)2 (Kim and O'Neil, 1997 ; Bemis et al., 1998), assuming seawater 18O, relative to V–SMOW to be 0‰ (Korte et al., 2005), and w correction from V–SMOW to V–PDB –0.27‰, average Late Permian temperature was 27.4°C and Early Triassic 27.9°C. Minimal end-Permian temperatures were 21.0°C and maximal 30.5°C, while in Early Triassic from 25.4 to 30.5°C. Our isotope measurements and calculations therefore correspond to Kiehl and Shields (2005) palaeotemperature models, assuming western Palaeotethys temperatures from 28–30°C, and Kearsey et al. (2009) estimating latest Permian temperatures between 26 and 29°C.

Numerous surfaces showing evidence of ancient exposure to subaerial conditions and dissolution from meteoric water are recognized in shallow-marine carbonates recorded on Velebit Mt.. Each of these surfaces point to subaerial exposure of various duration, but few of them show macroscopic and microscopic diagenetic features produced during prolonged chemical dissolution and associated modification of a carbonate rock, i.e. show signs of karstification. Such surfaces are therefore called palaeokarst surfaces (Choquette & James, 1988). Two potential palaeokarst surfaces are recognized in the studied succession and will be here described. Two sections of Lower Jurassic carbonate succession that belonged to the shallow inner ramp environment of the Adriatic-Dinaridic carbonate platform (ADCP) were studied in detail. Both sections are situated in the Velebit Mt. area (Kubus and Mali Alan passes). Today, these localities are 50 km apart. According to first appearance of foraminifer Mesoendothyra sp. and other characteristic fossil assemblage, studied succession is determined to be of Early Jurassic, or more precisely of Early Sinemurian age (Velić, 2007). Palaeokarst surfaces are recognized due to the data collected in the field (sedimentary structures) and during laboratory investigations (microfacies analysis from thin sections). In the field, these surfaces are of irregular relief, often show brecciated appearance due to the dissolution processes. Upper bedding planes show centimetre to decimetre sized irregular and circumgranular cracks filled with lighter coloured, often early diagenetic dolomitized limestone rock. Rarely these cracks contain yellow-brownish marly sediment. Cracks observed on upper bedding planes often penetrate as irregular fissures up to 15 cm downwards into the bed. The angle of dip of studied beds is 65°, but observed fissures pervade perpendicularly into the bed in relation to the upper bedding plane, pointing to their palaeokarst character and excluding the possibility that they are result of a recent karstification. Fissure walls are sharp and rough indicating that dissolution occurred in completely lithified rock. Fissure infill contains many angular millimetre to centimetre sized fragments of host rock. Dolomitized limestone found as fissure infill probably formed during marine transgression that followed exposure period, while yellow-brownish marly sediment, found on rare occasions, is probably washed away due to the same event. Limestones showing palaeokarstic features mostly have micritic texture (mudstones and wackestone) and under the microscope show small cracks and voids sometimes with preserved brownish coating on its wall indicating corrosion in subaerial conditions. According to the observed features, two surfaces studied in Lower Sinemurian carbonates are recognized as possible palaeokarst surfaces. Whereas these surfaces display micro-relief (penetrating few cm up to 15 cm into the rock) and no caves or larger dissolution features were observed, they can be attributed to a micro-karstification of lithified carbonates or formation of epikarst underneath a soil cover (Wright, 1992 ; Hillgärtner, 1998). These two palaeokarst surfaces are recorded at both studied sections and correlate very well, indicating contemporaneous subaerial exposure event that took place on the studied part of the ADCP and lasted long enough for palaeokarst structures to develop.

The Principal component analysis (PCA) was used to identify patterns of positive and negative covariation for Transitional and Sandy Dolomite samples, such as those expected between Al and trace elements included in clay matrices, or relations between Mg and Ca and siliciclastic minerals. Al, Si, K and Ti in the TD and SD datasets show high scores on the first principal component, indicating strong positive covariation. Elements with high coefficient of determination (R2) that correlate to Al2O3 content are those which tend to stay bound with clays during weathering and erosion, and therefore can be related to the terrigenous source area. Ca, Mg, S and Sr are generally more closely related within the Transitional Dolomite and may be connected to relatively abundant fossil content in these deposits. Transitional Dolomite is characterized by the positive Ca–Mg correlation (R2 = 0.59) and low variability in Ca/Mg ratio (1.48-1.50), indicating consistency in carbonate stechiometry. Sandy Dolomite with more variable Ca/Mg ratio (1.39-1.52) and low negative Ca–Mg correlation (R2 = -0.25) indicate more diverse carbonate mineralization. The increase in Mg content and its variability in Sandy Dolomite can be explained by sediment dolomitization and diagenesis. Correlations between Ca and S content in both units are positive (R2 = 0.46 in TD and 0.30 in SD). Mg and S are uncorrelated in the TD (R2 = 0.01), but show negative correlation in the SD unit (R2 = -0.48), suggesting that Mg source is not related to organic matter. This is consistent with the lack of the Mg-calcite skeletal remains in the lowermost part of the SD unit.

The uppermost Permian deposits in the Velebit Mt. area (Croatia) are characterized by the stratigraphic break caused by emergence and subsequent transgression which continued through the Permian–Triassic Boundary (PTB) into the Early Triassic. Two informal lithologic units can be distinguished – Transitional Dolomite (TD), relatively rich in fossils, and Sandy Dolomite (SD), characterized by recrystallized grains, scarce fossils, and enhanced input of terrigenous siliciclastic material [1, 2]. Selected TD and SD samples were disintegrated, or cut and polished and analyzed by optical microscopy, SEM, EDS, and XRD. Preliminary studies of the authigenic Fe-minerals found in the TD and SD units have shown characteristic mineral associations connected to the changes in the depositional environment. Fossiliferous TD deposits contain randomly dispersed red hematite grains. Highly recrystallized SD deposits above the lithologic change only occasionally contain hematite. Further up in the SD unit, due to the increased siliciclastic input and scarce fossils after the PTB, iron oxides form hematite, identical as in the TD unit, and magnetite. Magnetite, in framboidal form, in places accompanied with larger cubic crystals, is confined to recrystallized calcite and do not appear in the dolomite. The interstices between framboid microcrystals are filled with calcite ; some magnetite hexahedra intergrow with calcite rhombohedra or contain calcite crystals. Fine granulation, random dispersion, and association with fossil remains imply early diagenetic origin of hematite, when pore waters were more oxygenated and iron migrated by diffusion and not by pore water flow. Magnetite was formed during late diagenesis when more oxygen depleted waters penetrated into the sediment and mobilized iron from hematite. Locally concentrated magnetite suggests ion migration with pore water flow. Mineral stability fields of hematite and magnetite in an iron–carbonate–water system display magnetite as dominant mineral at high pH and low Eh conditions. In the absence of oxygen and at the high pH, precipitation was driven through OH¯ addition. As precipitation reduces OH¯ concentration and lowers pH, a small amount of carbonates was dissolved and restored equilibrium conditions within a solution.

Sedimentation from the uppermost Permian to the Lower Triassic deposits in the Velebit Mt. area is continuous (SALOPEK, 1948), and occurs within the lowest part of the informal lithostratigraphic unit of Sandy Dolomite. Lower Triassic deposits are mostly represented by early-diagenetic dolomites characterized by scarce fossil findings and frequent siliciclastic grains. Their composition indicate shallow-water marine depositional environment strongly influenced by the hinterland. Authigenic Fe-mineral association present in these dolomites, mainly pyrite and siderite, can therefore help in reconstruction of diagenetic and geochemical conditions of the dolomitization environment. Dolomitization of the studied sediments containing characteristic mineral association of pyrite, siderite, ankerite and dolomite, occurred in the mixing zone of sea and fresh water. Such dolomitization model is typical for the transgressive sequences (e.g. WRIGHT et al., 1997), which is in line with the ongoing transgression recorded within the Sandy Dolomite unit and continuous siliciclastic input to the shallow-water environment during Early Triassic. Fe-mineral associations and thermodynamic stability of authigenic iron minerals studied within uppermost Permian to Lower Triassic Sandy Dolomites of the Velebit Mt. provided a new tool to reveal diagenetic environment.

Shallow-marine carbonate succession formed during Early Jurassic on the Adriatic-Dinaridic carbonate platform (ADCP) contains numerous surfaces showing evidence of subaerial exposure. Most of these surfaces represent hiatuses below biostratigraphic resolution and only detailed sedimentologic and diagenetic study can distinguish these small scale discontinuities from simple bedding planes (Hillgärtner, 1998). In order to use exposure surfaces as correlation tool, their lateral extent needs to be determined (Sattler et al., 2005). Two sections of Lower Jurassic carbonate succession that belonged to the inner ramp environment of the ADCP were studied in detail on a cm scale. Both sections are situated in the Velebit Mt. area - Kubus (82 m thick) and Mali Alan (83 m thick). Today, these localities are 50 km apart. The under- and overlying rocks of each bedding plane and rocks from the bedding planes itself were studied and detailed bed-by-bed logs recording stratigraphical data, sedimentary structures and textures obtained from field and laboratory investigations are made. A correlation of the two sections is based on facies architecture, biostratigraphy, exposure surfaces and one bed marker, which enabled correlation of the two sections on a bed level. Three types of exposure surfaces containing features of diagenesis in subaerial conditions are observed and classificated sensu Hillgärtner (1998): i) paleosols showing pedogenic features (brecciated appearance, reworked lithoclasts within brownish yellow clayey calcareous matrix, rhizoturbation) ; ii) inter- to supra-tidal hardgrounds (HG) showing fenestral fabric, sheet cracks, birdseyes, circumgranular and desiccation cracks ; and iii) diagenetic discontinuities (DS) as bedding surfaces showing meteoric influence visible in thin sections as recrystallization of skeletal and nonskeletal particles and cements. Recorded logs are of Middle Sinemurian to Early Carixian age (FADs of Lituosepta recoarensis Cati, Orbitopsella primaeva Henson and Orbitopsella praecursor Gümbel are identified). Succession of Middle to Late Sinemurian age at both localities, shows little evidence of subaerial diagenesis: rare diagenetic DSs and inter- to supra-tidal HGs of limited lateral extent are observed. These surfaces are impossible to correlate at distance over 50 km. Contrary to this, succession of Late Sinemurian age contains the most prominent features of exposure into the meteoric diagenetic realm: 10 m interval section at Mali Alan containing several paleosols is well correlated with contemporaneous 8 m interval at Kubus containing several inter- to supra-tidal HGs and paleosols. This specific interval with different types of exposure surfaces extends laterally over 50 km and shows that their recognition can be useful in correlation of shallow-marine platform strata. Repeated periods of generally shorter-lived supratidal regime may be related to a single regressive event that occurred in the studied area, but to confirm this presumption, study of a wider platform area of the ADCP is required. Hillgärtner, H. (1998) Discontinuity surfaces on a shallow-marine carbonate platform (Berriasian, Valanginian, France and Switzerland). J. Sed. Res., 68, 1093-1108. Sattler, U., Immenhauser, A., Hillgärtner, H. and Esteban, M. (2005) Characterization, lateral variability and lateral extent of discontinuity surfaces on a Carbonate Platform (Barremian to Lower Aptian, Oman). Sedimentology, 52, 339-361.

Located along the Adriatic coast, the Velebit Mt. is the largest mountain range in Croatia. As a part of extensive Dinaric karst region, it consists of a wide variety of stratigraphic units, ranging in age from Carboniferous to Quaternary. Structurally, Velebit Mt. represents an anticline built up predominantly of carbonate rocks. The best developed karst features occur in the Jelar-breccia unit. Intensely tectonic deformed Jelar-breccia represents development of Paleogene deposits in the Karst Dinarides. These massive or thick- bedded carbonate breccias are built mostly from square, poorly sorted carbonate clasts of various sizes. Matrix is carbonate, gray to reddish coloured, whereas stratigraphic composition and size of clasts varies. Due to highly complex composition and differences in the composition of clasts (in relation to matrix) selective corrosion of these deposits occurs. Selective corrosion is further increased by micro-tectonic cracks in Jelar- breccia, as a result of intense tectonic deformations after sedimentation. All of these properties lead to increased weathering of rock mass, which results in “unusual relief forms“ development. From the sea-level up to the mountain top various types of karst relief forms occur: furrow-like karren (locally called žlibe), fissure karren (locally called škrape), rinnenkarren or runnels (solution grooves), network karren, debrits karren (locally called grohot), meandering karren, kamenitzas (solution pans), karst wells, natural bridges (locally called prozorci), and biocorrosion pits.

Post-Carboniferous deposits of the Karst Dinarides were analyzed in terms of their palaeomagnetic and rock magnetic properties in order to identify the best sections for comprehensive palaeomagnetic studies on the geodynamic and palaeogeographic evolution of this mountain belt. A total of eighteen reconnaissance rock samples have been collected from the Permian red beds and dolomites, and Triassic, Jurassic, Cretaceous and Eocene carbonates. Most come from Velebit Mt., part of the Dinaric orogenic belt finally uplifted in the Oligocene– Miocene, and stretching NW– SE along the NE Adriatic coast. Experimental studies comprised identification of potential carriers of a natural remanent magnetization (NRM) by means of their properties of Curie temperature and coercivity accompanied by SEM and microprobe studies, demagnetization of standard palaeomagnetic specimens by means of alternating field and thermal cleaning, as well as the measurement and analysis of magnetic susceptibility and its anisotropy. Haematite (in Permian red beds) and Ti-magnetite (in carbonates) and sporadically goethite have been identified as remanence carriers. The state of preservation, ascertained by SEM observations, suggests a detrital origin of NRM in most of the samples. Characteristic NRM components (ChRM), both of high coercivity and unblocking temperatures, could be clearly identified in most of the specimens. These components show smeared distribution on the sphere and do not cluster around any known palaeomagnetic direction expected for the Velebit area from apparent polar wander paths, neither for Eurasia nor for Africa. This outcome suggests lack of overall remagnetization of the studied part of the Karst Dinarides after the last tectonic event and/or important contribution from tectonic rotations to the observed pattern of ChRM distribution.

In the median part of the Velebit Mt. (SW Croatia, Yugoslavia) black limestones of the Zone have been investigated. Numerous fossils (175 taxa) have been determined and arranged into the fossil communities.The relationship betvween the type of sediment and the composition of fossil community has been studied.It was concluded that, during the Murghabian, the investigated region repre sented a shallow marine carbonate platform, settled in subtro pic climatic belt. Sea floor was overgrown with algal plains. Atseveral places mud-mounds and patch -reefs were created by fixosessile organisms. Sediments at the eastern edge of thezone were deposited in an intraplat form depression.

The glaciers developed during the Pleistocene have significantly contributed in the reshaping of the high mountain area by denudation but also by filling the karst depressions and speleological features. New glaciation proofs were recently found out in the underground, in the “ Ledenica u Štirovači” cave, in central part of the Velebit Mountain where clastic sediments of glacial and fluvioglacial origin were found out.

Generally the ridge crests spread in the dinaridic direction that is NW-SE what is mainly the characteristic of the older tectonic phase. The turn point in morphogenesis of the External Dinarides and thus of the Velebit Mt. occurs with the change of the in the shift of the Adriatic microplate toward N and NNW what is reflected on the orientation and morphology of the ridge crests as well as on the other relief form. The analyses of ridge crests are based on three main criteria: the analysis of orientation, length and the analysis of relatively homogeneous zones.

Sinemurian and Pliensbachian shallow-marine carbonates of the Velebit Mt. were deposited on a huge shallow marine carbonate platform covering vast areas of the Southern Tethyan realm, which was very soon, in Toarcian, disintegrated into several smaller platforms (including e.g. Apenninic, Apulian and Adriatic Carbonate Platform) separated by deeper marine basins. Detailed investigation of continuous Sinemurian and Pliensbachian succession outcropping along the Gospić-Karlobag road (Kubus locality – TIŠLJAR et al., 1991), allowed subdivision into 6 biostratigraphic zones, based on distribution and stratigraphic ranges of Lower Jurassic lituolids. Biozone 1: Mesoendothyra sp. lineage zone, Early Sinemurian (= interval zone of SEPTFONTAINE, 1984)- bounded by first appearance of Mesoendothyra sp. and first appearance of Lituosepta recoarensis CATI. Biozone 2) Lituosepta recoarensis lineage zona, Late Sinemurian (SEPTFONTAINE, 1984) – bounded by first appearance of Lituosepta recoarensis CATI and first appearance of Orbitopsella primaeva HENSON. Important taxa: Mesoendothyra sp., Lituosepta recoarensis, Planisepta compressa (HOTTINGER), Amijiella amiji (HENSON), Haurania deserta HENSON, Orbitopsella sp. Biozone 3) Orbitopsella primaeva lineage zona (SEPTFONTAINE, 1984) or Orbitopsella primaeva abundance zone, Early Carixian – bounded by first appearance of Orbitopsella primaeva HENSON and first appearance of Orbitopsella praecursor (GÜMBEL). Important taxa: Mesoendothyra sp., Lituosepta recoarensis, Planisepta compressa, Amijiella amiji, Haurania deserta, Orbitopsella primaeva. Biozone 4) Orbitopsella praecursor taxon-range zone, Late Carixian (SARTONI & CRESCENTI, 1962) - bounded by stratigraphic range of Orbitopsella praecursor (GÜMBEL). Important taxa: Mesoendothyra sp., Paleomayncina termieri (HOTTINGER), Lituosepta recoarensis, Planisepta compressa, Amijiella amiji, Haurania deserta, Orbitopsella primaeva, O. praecursor. Biozone 5: Orbitopsella praecursor– Pseudocyclammina liassica interval zone, Early Domerian – bounded by last appearance of Orbitopsella praecursor (GÜMBEL) and first appearance of Pseudocyclammina liassica HOTTINGER. Important taxa: Mesoendothyra sp., Paleomayncina termieri, Planisepta compressa, Amijiella amiji, Haurania deserta, Agerina martana (FARINACCI). Biozone 6) Pseudocyclammina liassica taxon-range zone, Late Domerian (SEPTFONTAINE, 1984) – corresponding to the stratigraphic range of Pseudocyclammina liassica HOTTINGER. Important taxa include: Mesoendothyra sp., Paleomayncina termieri, Planisepta compressa, Amijiella amiji, Haurania deserta, Agerina martana, Pseudocyclammina liassica. These established biozones correlate very well with contemporaneous deposits of Velebit Mt. (e.g. Mali Halan profile), as well as with other areas of the Karst Dinarides. In the wider Mediterranean realm these results almost completely correspond with biozonation proposed – and correlated with ammonite zones – by SEPTFONTAINE (1984) in the High Atlas Mts. of Morocco. Within the investigated Sinemurian and Pliensbachian shallow-marine inner platform carbonates of the Karst Dinarides, completely lacking ammonites and planktonic foraminifera, determined biozones of larger benthic foraminifera represent the most important tool for stratigraphic correlation.

Due to the predominance of soluble and broken carbonate beds on Velebit Mt., karst is main relief type there. But there also contact karst or fluviokarst occurs. It is developed in the parts where the alternation of permeable carbonate and less permeable or impermeable Carboniferous, Permian and Triassic beds occurs. Most significant contact karst forms in the area of Southern Velebit are Oštarijsko polje, Crno vrilo creek blind valley and Bunovac valley.

Middle Permian “middle zone of black limestones” exposed near Baške Oštarije on the Velebit Mt. is reinterpreted as ecological and morphological calcispongite reef. The reef framework is made of fenestellid bryozoans and calcisponges. It is possible to recognize two overgrowth generations. The reef framework is largely cemented by cyanobacterial coatings, so this reef complex belongs to cement reef family. The geometry of exposed sediments indicates a complex reef composition, which grew in three distinct phases. Reef growth was aborted by sea-level fall, which was followed by early cementation and creation of vadose silt which geopetally infilled the solutional cavities. The emersion lead to flattening of reef crest, whereas the weathering products deposited in internal cavities and on reef flanks. Three phases in reef growth were finally aborted by reef burial by thick black shales, what indicates rapid sea-level rise.

One of the many cave bears finding places in Croatia, caves Cerovačke pećine are situated on the slopes of Velebit Mt. in Lika. M. Malez discovered the cave bear remains in only one layer of upper pleistocene sediments during the excavation perfomed. After Malez (1975) this layer was deposited during the Last Glacial maximum (W3) and after radiometric dating before more than 40.000 years (Malez et al. 1979). Therefore, by using morphometry and morphogenesis of the most abundant remains (555 teeth and 393 metapodial bones of Ursus spelaeus) we have tried to solve the problem of the cave bears age. Namely, due to their very fast microevolutionary changes previously noticed on the material from Vindija Cave (Paunović 1998), they can be considered as guide elements for particular time intervals of the Last Glacial. The obtained results show two possibilities. 1. Fossiliferous layer was deposited under stable conditions very slowly from the beginning to the end of Last Glacial and the caves served as dens for numerous generations of cave bears in different periods of Upper Pleistocene. 2. The layer was deposited during Last Glacial Maximum and the cave bears were submitted to microevolutionary changes not characteristic for typical Ursus spelaeus. Because the question about the age of cave bears remains open, we think that a new investigation of quaternary sediments in caves Cerovačke pećine is necessary.

The superimposed Middle Permian carbonate bodies near Baške oštarije are interpreted as ecological and morphological reef complex, based on their characteristic fossil association, body geometry, and characteristic internal organisation. The superposition of the reefal bodies and the sediments studied document rapid sea-level changes, so that reef vertical growth was aborted during relative sea-level falls, and resumed during sea-level rise. Subaerial weathering created debris which was deposited in internal cavities and voids - further reducing the porosity, and on the reef flanks. The reef main body, as well as the flanking debris was levelled by weathering during relative sea-level falls, so that at the time of renewed colonization the substrate was virtually flat. The reef evolution can be summarized in 7 phases: 1. substrate colonization 2. formation of primary reef framework with dwellers 3. reef framework incrustation 4. early lithification 5. shallowing (relative sea-level fall) followed by weathering and erosion 6. infilling of secondary reef porosity 7. deepening (relative sea-level rise) followed by recolonization (or final burial as after reef body C)

Jablanac and its environs are composed of Paleogene-Neogene limestones and breccias. Quaternary sediments were deposited unconformably over thic Cenozoic basement. Quaternary sediments of Jablanac environs are represented by colluvial slope deposits, which are overlain by alluvial fans. The deposition acted in enclosed circular depression, which was opened towards the sea by later tectonical deformation. The debis was transported from the present-day Velebit channel. Very similar Quaternary sediments are exposed also on the Island of Rab, in Mišnjak Cove, but the paleotransport direction is opposite to the one of Jablanac. The source of sediment was evidently in the Velebit Channel area.

During three speleological expeditions the Slovačka jama cave has been explored to the depth of 1268m. In the cave there are several channels with phreatic forms. The highest relict phreatic channel is probably due to sinkholes formed on the karst uvala Veliki Lubenovac at the time of uvala formation. Lower, recent and subrecent, phreatic horizons at the cave bottom are probably a part of the underground route of the Lika river which sinks on the north-eastern side of Velebit mountain and flows through the mountain to the submarine springs in the Adriatic sea. Other channels are mostly shafts and channels with meandering vadose forms. 14C isotope analysis of speleothems shows that the oldest are situated in both ancient and subrecent phreatic channels, while younger ones are found in the vadose meandering channel.

Na području Srednjeg Velebita detaljno su istraženi crni vapnenci zone Neoschwagerina craticulifera. Određeno je ukupno stosedamdesetpet taksona mikrofosila i makrofosila, utvrđena je njihova pripadnost određenim fosilnim zajednicama, kao i odnos prema tipu sedimenta. Zaključeno je da je istraženo područje u vrijeme srednjeg perma predstavljalo plitkomorsku karbonatnu platformu smještenu u suptropskom klimatskom pojasu. Morsko dno bilo je obraslo algalnim livadama, unutar kojih su se na nekoliko mjesta formirali muljni humci i krpasti grebeni. Sedimenti na krajnjem istoku zone taložili su se u intraplatformskoj depresiji.

A detailed geochemical study, based on carbonate and associated organic carbon isotope composition, major and trace elements (including REE) distribution, the abundance and carbon isotope composition of hydrocarbon biomarkers, provides insights into the environmental changes at the Permian− Triassic (P/Tr) transition in the Velebit Mt., Croatia. The P/Tr transitional beds are regionally mainly represented by early to late diagenetic dolomites. The fossils in dolostones are represented mostly by calcareous algae, foraminifera, calcisponges, bryozoans, brachiopods and mollusks. The gradual impoverishment of Late Permian taxa moving towards the boundary is associated with a negative excursion at the transition of the d13C values of carbonates by up to 3‰ (P: – 0.8 to +2‰ , average +1.2± 0.5‰ ; T: – 1.3 to +0.9‰ , 0.0± 0.5‰ ), kerogen by up to 5‰ (P: – 27.3 to – 24.4‰ , – 25.8± 0.9‰ ; T: – 29.1 to – 26.4‰ , – 27.5± 0.4‰ ). The d15Nker values vary between – 2.4 to +8.2‰ (P: +3.7± 2.8‰ ; T: +3.8± 2.0‰ ), suggesting mixed contribution of 15N-rich marine (~7‰ ) and 15N-depleted terrestrial (~0‰ ) organic materials or cyanobacteria (– 2 to +4‰ ). Throughout the section the possible presence of zygospores suggests a contribution of terrestrial biomass. The variations in the distribution of n-alkanes (C13 to C34), acyclic isoprenoids (C21 to C28), hopanes and steranes, indicate input of bacterial and algal biomass. The occurrence of odd long-chain n-alkanes (maximazing at C26) and C39 steranes in all samples indicate a contribution of continental material. The relatively high contents of redox sensitive elements in the uppermost Permian dolomites (up to 28 mg/g V, 11 mg/g U, and 25 mg/g Cr) indicate a more reducing environment. In the uppermost Permian rocks an enrichment in most REE compared to the other Permian and Triassic samples is associated with a negative Ce anomaly (1.1 to 0.5). The decrease in the d13C values in the carbonates and kerogens are synchronized with a drop in D13Ccarb-ker by 2‰ , indicating lower productivity at the P/Tr transition. The first results of compound specific C isotope analyses of alkanes indicate a 13C depletion towards the boundary, supporting the lowering of primary productivity.

New biogeochemical data redefined the position of the Permian-Triassic boundary (PTB) in the Velebit Mt., Croatia, previously positioned at the lithological boundary, and indicate two stress events. Pronounced enrichment in REE concentrations, negative Ce anomaly, negative shift in d13Cker values and disappearance of microfossils coincide with the occurrence of ooids, marking the first stress event, most probably the Late Permian regression. The second event is the PTB, with the well known negative shift in d13Ccarb from +1.4 to -0.6‰ (VPDB ; P: -0.8 to +2‰ ; Tr: -1.3 to +0.9‰ ) and biota impoverishment. The d13Cker values at PTB are - 27.1‰ , P: -27.3 to -24.4‰ , and Tr: -29.1 to -26.4‰ . The d15Nker values show a preferential marine influence during the Late Permian (~7‰ ) before the regression phase, and enhanced terrestrial influence towards the PTB with presence of cyanobacteria (-2 to +4‰ ), which seems to be the only surviving taxa. Long chained n-alkanes (C17-C31, max. C26), with even/odd predominance are probably derived from the freshwater green microalga Botryococcus braunii, indicating lagoonal-type environment. The C17/C18 ratios show a stronger algal influence during Early Triassic. Prystane and phytane are present in most samples and they can be derived from chlorophyll in algae and cyanobacteria. The distribution of n-alkylcyclohexanes (C17-C24, max. C21) with even/odd predominance indicate a bacterial biomass contribution. Values of Pr/Ph ratio are mostly