Genesis of Middle Triassic volcaniclastic deposits in the External Dinarides : doctoral thesis

Tijekom srednjega trijasa na području Vanjskih Dinarida tektonika povezana s otvaranjem Tetiskog oceana dovela je do značajne diferencijacije taložnih okoliša. Istovremeno su egzistirala izdignuta područja sa značajkama subaerske vulkanske aktivnosti i trošenja starijih stijena te njihova pretaloživanja, kao i plitkomorski prostori obilježeni karbonatnom sedimentacijom te dublja, pelagička morska korita u kojima su taloženi različiti sedimenti uključujući i vulkanoklastične i vulkanske stijene. Cilj provedenog istraživanja je bio definirati i opisati srednjetrijaske vulkanoklastične naslage, odrediti njihov stratigrafski položaj u Vanjskim Dinaridima, definirati taložne okoliše u kojima su nastale, geokemijskim podacima povezati ih s geotektonskim okolišem u kojem je nastala magma koja je producirala vulkanoklastične naslage te usporediti razvoj prostora Vanjskih Dinarida s okolnim prostorima zapadnog Tetisa. Analizirane su petrološko-sedimentološke, mineraloške i geokemijske karakteristike vulkanoklastičnih naslaga s pet lokaliteta u Vanjskim Dinaridima (Donje Pazarište i Jovanović Draga u okolici Gospića, Bosansko Grahovo u Bosni i Hercegovini, Zelovo u blizini Sinja, i Plavno u blizini Knina). Mikropetrografskim metodama određeni su facijesi istraživanih stijena i mehanizmi njihova postanka čime je omogućena rekonstrukcija taložnih okoliša. Analizama konodontnog materijala biostratigrafski je određena starost te je postavljen vremenski okvir taloženja vulkanoklastita srednjega trijasa. Geokemijskim analizama dobiveni su podaci koji su korišteni za klasifikaciju istraživanih stijena, odredbu geotektonskog okvira i porijekla magme iz koje su nastale vulkanoklastične naslage, te je omogućena rekonstrukcija petrogenetskog modela u srednjem trijasu Vanjskih Dinarida. Vulkanoklastične naslage srednjega trijasa nastajale su u kopnenim i marinskim okolišima. Većina istraživanih lokaliteta ima obilježja dubljevodne pelagičke sedimentacije. Taloženje ovih naslaga u Vanjskim Dinaridima vezano je za prijelazni interval iz anizika u ladinik, kao i u većini okolnih prostora zapadnog dijela nekadašnjeg Tetiskog oceana. Geokemijska obilježja vulkanoklastičnih i vulkanskih stijena ukazuje na kalcijsko-alkalijsku magmu kontaminiranu krustalnim materijalom nastalu u složenom geotektonskom sustavu. Sedimentološka obilježja istraživanih vulkanoklastita i s njima udruženih sedimentnih stijena dokazuju postojanje nepotpuno razvijenih malih riftnih sustava.In the Middle Triassic times, the External Dinarides were a part of the Western Tethyan domain (Haas et al., 1995; Stampfli & Borel, 2002; 2003; Scotese et al., 2004). A deposition of the Early Triassic low energy carbonate-siliciclastic sediments of the epeiric ramp (Aljinović et al., 2014) was interrupted in the Middle Triassic by vigorous and extensive tectonic activity related to the opening of the Tethyan Ocean. Tectonic activity was accompanied by volcanism and formation of volcanic and volcaniclastic rocks. These tectonic movements caused the differentiation of the relief, thus forming different rift related tectonic structures. Some tectonic blocks were uplifted and prone to subaerial erosion while others were subsided and developed different deep marine, pelagic facies. All depositional environments were under the influence of volcanic activity. However, some areas experienced long lasting shallow marine, mostly carbonate sedimentation. The Middle Triassic volcanic and volcaniclastic rocks were investigated by various authors (e.g. Poljak & Tajder, 1948; Lugović & Majer, 1983; Pamić, 1984; Marci et al., 1991; Trubelja et al., 2004; Garašić et al., 2006; Preglej, 2006; Hrvatović et al., 2011; Aljinović et al., 2011). Some of them pronounced the controversial relation between the geochemical data of volcanic rocks and geotectonic setting in the Middle Triassic (Lugović & Majer, 1983; Pamić, 1984; Trubelja et al., 2004; Garašić et al., 2006). That resulted in the unambiguous interpretation of the magma origin. Geochemical data all indicate calc-alkaline magma composition, which is more common in the subduction areas than in rift zones. The typical Middle Triassic rift related magmatic rocks (ophiolites) are still not found in the External Dinarides. The aim of this dissertation is to present the petrological, sedimentological, stratigraphical and geochemical data of the investigated volcaniclastic rocks and to unravel its genesis and origin. Therefore, volcaniclastic rocks at five localities in the External Dinarides were investigated. The field methods included recording the sedimentary sections in which different volcaniclastic rocks crop out. Petrographical methods were used to analyse micropetrographic composition (in thinsections) and differentiate sedimentary facies based on the lithology and depositional processes. The differentiation of the facies allowed reconstruction of the depositional mechanisms and prediction of the sedimentary model for each of the investigated localities. Carbonate sedimentary rocks associated with the volcaniclastics served for conodont analysis that enabled the biostratigraphic constrains of the volcanic activity. The high-resolution conodont biostratigraphy also enabled the correlation of the investigated sequences. Geochemical analysis aimed to determine the magma composition and according to that interpret geotectonic position of the investigated area. In Lika, part of the Velebit Mts., the five small localities were investigated adjacent to the village Donje Pazarište. In all five localities, the different volcaniclastic deposits were recorded in different sedimentary sequences. The three sedimentary sequences, called Donje Pazarište 1, Donje Pazarište 2 and Donje Pazarište 3 form almost continuous 97 m thick succession with six different facies: Flysch facies (FF), Carbonate shale facies (KS), Syneruptive resedimented pyroclastic facies (FSP), Platy limestone and pyroclastic facies (FPV), Limestone breccia facies (VB) and Slumped limestone, chert and pyroclastic facies (FSV). Near the investigated sections (Donje Pazarište 1, 2, 3) the Pyroclastic flow facies (FPT) was determined (similarly as investigated by Preglej, 2006). The whole sequence has the characteristics of deposition in the open marine, pelagic environment. The beginning of the sequence was influenced by Flysch facies (FF) deposited by turbidity currents. Flysch facies was conformably overlain by Carbonate shale facies (KS) slightly influenced by deposition of pyroclastic material. Syneruptive resedimented pyroclastics (FSP) were redeposited from relatively shallow parts of the depositional area to the deep pelagic areas via pyroclastic turbidity currents. Deposition of the Platy limestone and pyroclastic facies (FPV), indicates shallowing of the environment envisaged by prevalence of limestones. Limestone breccia facies (VB) occassionaly occurres in the sequence and imply periods of intense tectonic activity. Slumped limestone, chert and pyroclastic facies (FSV) was deposited in pelagic environment influenced by the deposition of pyroclastic material primary sedimented through water settled fall out on slopes. The sequence was strongly influenced by tectonic activity and tectonic block movements. The Pyroclastic flow facies (FPT), located in vicinity of the youngest strata of the Donje Pazarište section, has the characteristics of subaerial emplaced ignimbrite flow, as does the same facies in the vicinity of the village Brušane, in the foothill of Vinac. Lithological similarities of these rocks allow the interpretation that they possibly represent a unique pyroclastic flow generated by pyroclastic column collapse and subaerial of shallow marine emplacement. The time constraint of this facies is unfortunately missing due to lack of conodont species in the associated shallow water limestones. In the same area, the recorded profile Jovanović Draga consists completely of volcaniclastic deposits (81 m thick) that are associated with the olivine basalt of Coherent facies (KF). Among volcaniclastics, the Hyaloclastic facies (HF) was differentiated. It was formed by autoclastic processes and limited pyroclastic activity. Fragments formed by autoclastic processes were mixed with fragments of carbonate rocks probably formed by fragmentation of the lithified carbonates during magma ascent. Explosive eruption was restricted due to water depth that limited the spread of pyroclastic material (dominantly volcanic glass shards). The recorded profile near the village Bosansko Grahovo (Bosnia and Herzegovina), consists of 79 m thick dominantly autoclastic deposits. Four different volcaniclastic facies were determined. The base of the profile is represented by the significant Limestone peperite facies (FVP). It consists of bioclastic peckstones-weckstones with thin-shelled bivalves and radiolarians indicating emplacement of hot lava in the pelagic environment. The Limestone peperite facies is conformably overlain with the Pyroclastic flow facies (FPT), followed by a Hyaloclastic facies (FH) divided into three lithotypes: resedimented basalt-andesite hyaloclastite (Pba), in situ basalt hyaloclastite (ISb) and resedimented basalt hyaloclastite (Pb). The top of the sequence is characterized by the occurrence of the Breccia-conglomerate peperite (FBP). The facies distribution possibly represents both, the lateral and the vertical exchange of recorded facies. According to the fossil content in the limestone parts of the peperite, the sedimentary environment is determined as pelagic. Pyroclastic flow facies in this profile is represented by a small volume ignimbrite formed in the low fountaining volcanic vent and was constantly in contact with warm ascending magma throughout the emplacement time. Hyaloclastic facies (FH) was formed by quenching fragmentation of the coherent facies. The accurence of in situ basalt hyaloclastite is closely associated with the coherent facies of the same composition (not recorded in the outcrops). The resedimented hyaloclastite shows the increased distance from the area where the coherent facies was located. The same trend can be observed in the gradual transition to the Breccia-conglomerate peperite facies that consists of limestone, silicified limestone and basalt clasts with volcanic matrix. The most investigated locality of the Middle Triassic volcaniclastic deposits in the External Dinarides is located in the area of Mt. Svilaja, near the village Zelovo. The area was investigated by Šćavničar et al., (1983), Belak, (2000), Marjanac, (2000), Jelaska et al., (2003), Balini et al., (2006), Kolar-Jurkovšek et al., (2006), Aljinović et al., (2010), Hrvatović et al., (2011), Halamski et al., (2016). In the investigated area, two sedimentary sequences were recorded, and an isolated coherent facies was noticed and analyzed. The profile Zelovo 1 (14,5 m thick) consists of Silicified carbonate facies (FSK) with slumped beds, interlayered with the pale green unconsolidated altered clay tuffs and dark green consolidated crystalovitric tuffs belonging to the Syneruptive resedimented pyroclastic facies (FPP). The profile Zelovo 2 (8,2 m thick) consists of the same rock types in the similar vertical arrangement as in Zelovo 1. The noticed coherent facies (KF) is located nearby the profile Zelovo 2 and is represented by basalts with intrasertal texture. The volcaniclastic deposits were formed by syneruptive resedimentation of pyroclastic material by turbidity currents and deposited in small-scaled restricted pelagic basins that Belak (2000) defined as simple graben structure. The pyroclastic material has phreatomagmatic characteristics indicating that external water enhanced explosive eruptions and influenced production of the pyroclastic material. The Plavno locality represents a short, 6,5 m thick sedimentary succession. It consists of the three differentiated facies: Silicified limestones composed of pelagic biota and occasional crystaloclasts (FSV), Resedimented pyroclastic facies (FPT) and Volcanogenic sandstone facies (FVP). The Resedimented pyroclastic facies (FPT) consists of vitiriclastic and lithoclastic tuffs formed by resedimentation processes. Lithoclasts in lithoclastic tuffs are represented by low porosity juvenile clasts classified as cognate lithic clasts formed as products of pyroclastic activity of basaltic explosive eruptions, probably of strombolian or hawaiian eruption type. Concerning time constraint of the Middle Triassic volcanic activity, the new biostratigraphic data is presented. At Donje Pazarište locality ammonoids, found in Carbonate shale facies (KS), were determined as Flexoptychites sp. which was earlier reported in the trinodosus ammonoid zone in the External Dinarides ( Prlj & Murđenović, 1988; Petek, 1997). Conodont analysis yield different conodont species in the described sections. Conodont species determined in the sample DP-2/34 of the Platy limestone and pyroclastic facies (FPV) are Neogondolella bifurcate, N. constricta, N. sp. and Gladigondolella sp. that indicate Lower Illyrian age. Higher in the succession, Paragondollela sp., P. trammeri, P. excelsa and G. tethydis conodont species were found in the Slumped limestone, chert and pyroclastic facies (FSV). These species indicate stratigraphic range from Upper Illyrian to Fassanian. At the Bosansko Grahovo locality from the Limestone peperite facies (FVP) following conodont assemblages were determined: in samples G2 and G3 conodont species Neogondolella excentrica, Paragondolella excelsa and Gladigondolella tethydis suggest Lower Illyrian age, while in samples G4 to G9 – N.excelsa, P.trammeri and G.tethydis imply Upper Illyrian age. Jelaska et al. (2003), Balini et al., (2006), and Kolar-Jurkovšek et al., (2006), presented the biostratigraphic data for the Zelovo section previously. The determination of conodont zones from these investigations were used as reference conodont zonation for the investigated area of the External Dinarides. The conodont samples form the Plavno section proved negative in conodont elements. Presented biostratigraphic data enable valid correlation of the investigated sections and proved that Donje Pazarište and Bosansko Grahovo sections represented a deposition in the similar time interval and are of Illyrian age, while Zelovo section was somewhat younger and point to Fassanian age. Two major types of geochemical analysis were conducted in the scope of this research: 19 samples were analysed using ICP-MS and XRF for the whole rock analysis, and 7 samples were analysed using EMP point analysis and element mapping of thinsection areas. Whole rock geochemical data enable to constraint the magma type and to interpret geotectonic setting and their close relation. Results presented in concentration diagrams for rare earth elements and spider diagrams for trace elements showed the influence of continental crust in the formation of calc-alkaline magma significant for the Middle Triassic volcanism in the External Dinarides. The same influence was proved by diagrams of Cabanis & Lesscolle, (1979) and Wood, (1980), that implied all analysed samples had characteristics of volcanic arc magma composition. The EMP analysis of the pyroxene in the coherent and hyaloclastic facies of the Jovanović Draga section and in situ basaltic hyaloclastics from Bosansko Grahovo section showed that most of them are diopside and augite originated from calc-alkaline magma under low to medium pressure regimes. In addition, the diagram for the definition of the geotectonic position showed that pyroxenes from Jovanović Draga are of calc-alkaline orogenic magma origin, while pyroxenes from Bosansko Grahovo are characterized by magma of rift areas. This can mean that the more southern localities are less influenced by arc magmatism and that influence can be seen only in the geochemistry of pyroxenes. Plagioclase analysis from Zelovo locality shows that pyroclastic crystaloclasts are both normally and reversely zoned. Composition of the Na2O and CaO content vary from the core to the rim of the crystaloclasts respectively. This fact can be interpreted as constant income of the new more primitive magma (with higher CaO content) in the magma chamber from where the explosive eruptions were triggered and pyroclastic material was formed. The synthesis of all the investigated results enabled comparison of the External Dinarides with other areas of the Western Tethys (Internal Dinarides, Southern Alps, Northern Calcareous Alps, and Transdanubian Range). Most of the areas show some significant regional events or are time constrained that enable correlation between them. Almost all facies, differentiated in this work, appear with some differences, in other Western Tethyan areas. The occurrence of deeper marine facies and drowning of shallow marine carbonate sedimentary environments was recorded for the first time in the Upper Anisian (Buser, 1989; Krystyn & Lein, 1996; Gianolla et al. 1998; Missoni et al., 2001; Preto et al., 2009; Kovács et al., 2011). The main magmatic activity started in the Anisian but was the most vigorous in the Upper Anisian and Lower Ladinian (Bechstäld et al., 1978; Castellarin et al., 1988; Szoldán, 1990; Castellarin & Rossi, 1991; Obenholzner, 1991; Mundil et al., 1996; Harangi et al., 1996; Velledits, 2004; 2006; Brandner et al., 2007). As the magmatic and tectonic activity slowly abated in the Upper Ladinian, a development of the shallow marine, carbonate dominant environments had commenced (Broglio-Loriga, 1967; Keim & Neri, 2005; Manfrin et al., 2005; Bernardi et al., 2011; Lein et al., 2012; Celarc et al., 2013). Geochemical data from all neighbouring Western Tethyan areas has calc-alkaline, even shoshonitic character, not common for the supposed geotectonic setting depicted as rift (e.g. Bechstäld et al., 1978; Crisci et al., 1984; Castellarin et al., 1988; Harangi et al., 1996). The Middle Triassic rift related depositional environments, where various types of volcanoclastic rocks occurred, was also interpreted for the External Dinaridic area and documented in this work. The volcanic and volcaniclastic rocks have the same geochemical imprint as recognized in the neighbouring Tethyan areas. This fact can be explained by fitting the External Dinarides in the palinspactic reconstructions (in this work the palaeoreconstruction by Stampfli & Borel, 2003 was used). In the Middle Triassic, the External Dinarides can be located between the rift-related Tethyan domains (opening of the Tethyan Ocean from the southeast). The Tethyan rifting phase had detached the Cimmerian block while contemporaneously the subduction of the Palaeotethys to the northeast, beneath the Laurasian part of Gondwana, occurred. The formation of the several small-scale back arc rift belts was related to the subduction on the northern margin of Palaeotethys. One of these back arc rift belts developed as Meliata Ocean, bordering the Dinaridic region to the north. More to the west from Meliata an undeveloped back-arc rift belt was positioned in the area of today Exteranal Dinarides. This rift did not continue to develope the real ocean (lack of ofiolites) but due to the main Tethyan rifting trend that was intensified during Ladinian, the back-arc rift in the External Dinarides had arrested and ended as differentiated pelagic environment filled with various sedimentary material

Genesis of Middle Triassic volcaniclastic deposits in the External Dinarides : doctoral thesis

Tijekom srednjega trijasa na području Vanjskih Dinarida tektonika povezana s otvaranjem Tetiskog oceana dovela je do značajne diferencijacije taložnih okoliša. Istovremeno su egzistirala izdignuta područja sa značajkama subaerske vulkanske aktivnosti i trošenja starijih stijena te njihova pretaloživanja, kao i plitkomorski prostori obilježeni karbonatnom sedimentacijom te dublja, pelagička morska korita u kojima su taloženi različiti sedimenti uključujući i vulkanoklastične i vulkanske stijene. Cilj provedenog istraživanja je bio definirati i opisati srednjetrijaske vulkanoklastične naslage, odrediti njihov stratigrafski položaj u Vanjskim Dinaridima, definirati taložne okoliše u kojima su nastale, geokemijskim podacima povezati ih s geotektonskim okolišem u kojem je nastala magma koja je producirala vulkanoklastične naslage te usporediti razvoj prostora Vanjskih Dinarida s okolnim prostorima zapadnog Tetisa. Analizirane su petrološko-sedimentološke, mineraloške i geokemijske karakteristike vulkanoklastičnih naslaga s pet lokaliteta u Vanjskim Dinaridima (Donje Pazarište i Jovanović Draga u okolici Gospića, Bosansko Grahovo u Bosni i Hercegovini, Zelovo u blizini Sinja, i Plavno u blizini Knina). Mikropetrografskim metodama određeni su facijesi istraživanih stijena i mehanizmi njihova postanka čime je omogućena rekonstrukcija taložnih okoliša. Analizama konodontnog materijala biostratigrafski je određena starost te je postavljen vremenski okvir taloženja vulkanoklastita srednjega trijasa. Geokemijskim analizama dobiveni su podaci koji su korišteni za klasifikaciju istraživanih stijena, odredbu geotektonskog okvira i porijekla magme iz koje su nastale vulkanoklastične naslage, te je omogućena rekonstrukcija petrogenetskog modela u srednjem trijasu Vanjskih Dinarida. Vulkanoklastične naslage srednjega trijasa nastajale su u kopnenim i marinskim okolišima. Većina istraživanih lokaliteta ima obilježja dubljevodne pelagičke sedimentacije. Taloženje ovih naslaga u Vanjskim Dinaridima vezano je za prijelazni interval iz anizika u ladinik, kao i u većini okolnih prostora zapadnog dijela nekadašnjeg Tetiskog oceana. Geokemijska obilježja vulkanoklastičnih i vulkanskih stijena ukazuje na kalcijsko-alkalijsku magmu kontaminiranu krustalnim materijalom nastalu u složenom geotektonskom sustavu. Sedimentološka obilježja istraživanih vulkanoklastita i s njima udruženih sedimentnih stijena dokazuju postojanje nepotpuno razvijenih malih riftnih sustava.In the Middle Triassic times, the External Dinarides were a part of the Western Tethyan domain (Haas et al., 1995; Stampfli & Borel, 2002; 2003; Scotese et al., 2004). A deposition of the Early Triassic low energy carbonate-siliciclastic sediments of the epeiric ramp (Aljinović et al., 2014) was interrupted in the Middle Triassic by vigorous and extensive tectonic activity related to the opening of the Tethyan Ocean. Tectonic activity was accompanied by volcanism and formation of volcanic and volcaniclastic rocks. These tectonic movements caused the differentiation of the relief, thus forming different rift related tectonic structures. Some tectonic blocks were uplifted and prone to subaerial erosion while others were subsided and developed different deep marine, pelagic facies. All depositional environments were under the influence of volcanic activity. However, some areas experienced long lasting shallow marine, mostly carbonate sedimentation. The Middle Triassic volcanic and volcaniclastic rocks were investigated by various authors (e.g. Poljak & Tajder, 1948; Lugović & Majer, 1983; Pamić, 1984; Marci et al., 1991; Trubelja et al., 2004; Garašić et al., 2006; Preglej, 2006; Hrvatović et al., 2011; Aljinović et al., 2011). Some of them pronounced the controversial relation between the geochemical data of volcanic rocks and geotectonic setting in the Middle Triassic (Lugović & Majer, 1983; Pamić, 1984; Trubelja et al., 2004; Garašić et al., 2006). That resulted in the unambiguous interpretation of the magma origin. Geochemical data all indicate calc-alkaline magma composition, which is more common in the subduction areas than in rift zones. The typical Middle Triassic rift related magmatic rocks (ophiolites) are still not found in the External Dinarides. The aim of this dissertation is to present the petrological, sedimentological, stratigraphical and geochemical data of the investigated volcaniclastic rocks and to unravel its genesis and origin. Therefore, volcaniclastic rocks at five localities in the External Dinarides were investigated. The field methods included recording the sedimentary sections in which different volcaniclastic rocks crop out. Petrographical methods were used to analyse micropetrographic composition (in thinsections) and differentiate sedimentary facies based on the lithology and depositional processes. The differentiation of the facies allowed reconstruction of the depositional mechanisms and prediction of the sedimentary model for each of the investigated localities. Carbonate sedimentary rocks associated with the volcaniclastics served for conodont analysis that enabled the biostratigraphic constrains of the volcanic activity. The high-resolution conodont biostratigraphy also enabled the correlation of the investigated sequences. Geochemical analysis aimed to determine the magma composition and according to that interpret geotectonic position of the investigated area. In Lika, part of the Velebit Mts., the five small localities were investigated adjacent to the village Donje Pazarište. In all five localities, the different volcaniclastic deposits were recorded in different sedimentary sequences. The three sedimentary sequences, called Donje Pazarište 1, Donje Pazarište 2 and Donje Pazarište 3 form almost continuous 97 m thick succession with six different facies: Flysch facies (FF), Carbonate shale facies (KS), Syneruptive resedimented pyroclastic facies (FSP), Platy limestone and pyroclastic facies (FPV), Limestone breccia facies (VB) and Slumped limestone, chert and pyroclastic facies (FSV). Near the investigated sections (Donje Pazarište 1, 2, 3) the Pyroclastic flow facies (FPT) was determined (similarly as investigated by Preglej, 2006). The whole sequence has the characteristics of deposition in the open marine, pelagic environment. The beginning of the sequence was influenced by Flysch facies (FF) deposited by turbidity currents. Flysch facies was conformably overlain by Carbonate shale facies (KS) slightly influenced by deposition of pyroclastic material. Syneruptive resedimented pyroclastics (FSP) were redeposited from relatively shallow parts of the depositional area to the deep pelagic areas via pyroclastic turbidity currents. Deposition of the Platy limestone and pyroclastic facies (FPV), indicates shallowing of the environment envisaged by prevalence of limestones. Limestone breccia facies (VB) occassionaly occurres in the sequence and imply periods of intense tectonic activity. Slumped limestone, chert and pyroclastic facies (FSV) was deposited in pelagic environment influenced by the deposition of pyroclastic material primary sedimented through water settled fall out on slopes. The sequence was strongly influenced by tectonic activity and tectonic block movements. The Pyroclastic flow facies (FPT), located in vicinity of the youngest strata of the Donje Pazarište section, has the characteristics of subaerial emplaced ignimbrite flow, as does the same facies in the vicinity of the village Brušane, in the foothill of Vinac. Lithological similarities of these rocks allow the interpretation that they possibly represent a unique pyroclastic flow generated by pyroclastic column collapse and subaerial of shallow marine emplacement. The time constraint of this facies is unfortunately missing due to lack of conodont species in the associated shallow water limestones. In the same area, the recorded profile Jovanović Draga consists completely of volcaniclastic deposits (81 m thick) that are associated with the olivine basalt of Coherent facies (KF). Among volcaniclastics, the Hyaloclastic facies (HF) was differentiated. It was formed by autoclastic processes and limited pyroclastic activity. Fragments formed by autoclastic processes were mixed with fragments of carbonate rocks probably formed by fragmentation of the lithified carbonates during magma ascent. Explosive eruption was restricted due to water depth that limited the spread of pyroclastic material (dominantly volcanic glass shards). The recorded profile near the village Bosansko Grahovo (Bosnia and Herzegovina), consists of 79 m thick dominantly autoclastic deposits. Four different volcaniclastic facies were determined. The base of the profile is represented by the significant Limestone peperite facies (FVP). It consists of bioclastic peckstones-weckstones with thin-shelled bivalves and radiolarians indicating emplacement of hot lava in the pelagic environment. The Limestone peperite facies is conformably overlain with the Pyroclastic flow facies (FPT), followed by a Hyaloclastic facies (FH) divided into three lithotypes: resedimented basalt-andesite hyaloclastite (Pba), in situ basalt hyaloclastite (ISb) and resedimented basalt hyaloclastite (Pb). The top of the sequence is characterized by the occurrence of the Breccia-conglomerate peperite (FBP). The facies distribution possibly represents both, the lateral and the vertical exchange of recorded facies. According to the fossil content in the limestone parts of the peperite, the sedimentary environment is determined as pelagic. Pyroclastic flow facies in this profile is represented by a small volume ignimbrite formed in the low fountaining volcanic vent and was constantly in contact with warm ascending magma throughout the emplacement time. Hyaloclastic facies (FH) was formed by quenching fragmentation of the coherent facies. The accurence of in situ basalt hyaloclastite is closely associated with the coherent facies of the same composition (not recorded in the outcrops). The resedimented hyaloclastite shows the increased distance from the area where the coherent facies was located. The same trend can be observed in the gradual transition to the Breccia-conglomerate peperite facies that consists of limestone, silicified limestone and basalt clasts with volcanic matrix. The most investigated locality of the Middle Triassic volcaniclastic deposits in the External Dinarides is located in the area of Mt. Svilaja, near the village Zelovo. The area was investigated by Šćavničar et al., (1983), Belak, (2000), Marjanac, (2000), Jelaska et al., (2003), Balini et al., (2006), Kolar-Jurkovšek et al., (2006), Aljinović et al., (2010), Hrvatović et al., (2011), Halamski et al., (2016). In the investigated area, two sedimentary sequences were recorded, and an isolated coherent facies was noticed and analyzed. The profile Zelovo 1 (14,5 m thick) consists of Silicified carbonate facies (FSK) with slumped beds, interlayered with the pale green unconsolidated altered clay tuffs and dark green consolidated crystalovitric tuffs belonging to the Syneruptive resedimented pyroclastic facies (FPP). The profile Zelovo 2 (8,2 m thick) consists of the same rock types in the similar vertical arrangement as in Zelovo 1. The noticed coherent facies (KF) is located nearby the profile Zelovo 2 and is represented by basalts with intrasertal texture. The volcaniclastic deposits were formed by syneruptive resedimentation of pyroclastic material by turbidity currents and deposited in small-scaled restricted pelagic basins that Belak (2000) defined as simple graben structure. The pyroclastic material has phreatomagmatic characteristics indicating that external water enhanced explosive eruptions and influenced production of the pyroclastic material. The Plavno locality represents a short, 6,5 m thick sedimentary succession. It consists of the three differentiated facies: Silicified limestones composed of pelagic biota and occasional crystaloclasts (FSV), Resedimented pyroclastic facies (FPT) and Volcanogenic sandstone facies (FVP). The Resedimented pyroclastic facies (FPT) consists of vitiriclastic and lithoclastic tuffs formed by resedimentation processes. Lithoclasts in lithoclastic tuffs are represented by low porosity juvenile clasts classified as cognate lithic clasts formed as products of pyroclastic activity of basaltic explosive eruptions, probably of strombolian or hawaiian eruption type. Concerning time constraint of the Middle Triassic volcanic activity, the new biostratigraphic data is presented. At Donje Pazarište locality ammonoids, found in Carbonate shale facies (KS), were determined as Flexoptychites sp. which was earlier reported in the trinodosus ammonoid zone in the External Dinarides ( Prlj & Murđenović, 1988; Petek, 1997). Conodont analysis yield different conodont species in the described sections. Conodont species determined in the sample DP-2/34 of the Platy limestone and pyroclastic facies (FPV) are Neogondolella bifurcate, N. constricta, N. sp. and Gladigondolella sp. that indicate Lower Illyrian age. Higher in the succession, Paragondollela sp., P. trammeri, P. excelsa and G. tethydis conodont species were found in the Slumped limestone, chert and pyroclastic facies (FSV). These species indicate stratigraphic range from Upper Illyrian to Fassanian. At the Bosansko Grahovo locality from the Limestone peperite facies (FVP) following conodont assemblages were determined: in samples G2 and G3 conodont species Neogondolella excentrica, Paragondolella excelsa and Gladigondolella tethydis suggest Lower Illyrian age, while in samples G4 to G9 – N.excelsa, P.trammeri and G.tethydis imply Upper Illyrian age. Jelaska et al. (2003), Balini et al., (2006), and Kolar-Jurkovšek et al., (2006), presented the biostratigraphic data for the Zelovo section previously. The determination of conodont zones from these investigations were used as reference conodont zonation for the investigated area of the External Dinarides. The conodont samples form the Plavno section proved negative in conodont elements. Presented biostratigraphic data enable valid correlation of the investigated sections and proved that Donje Pazarište and Bosansko Grahovo sections represented a deposition in the similar time interval and are of Illyrian age, while Zelovo section was somewhat younger and point to Fassanian age. Two major types of geochemical analysis were conducted in the scope of this research: 19 samples were analysed using ICP-MS and XRF for the whole rock analysis, and 7 samples were analysed using EMP point analysis and element mapping of thinsection areas. Whole rock geochemical data enable to constraint the magma type and to interpret geotectonic setting and their close relation. Results presented in concentration diagrams for rare earth elements and spider diagrams for trace elements showed the influence of continental crust in the formation of calc-alkaline magma significant for the Middle Triassic volcanism in the External Dinarides. The same influence was proved by diagrams of Cabanis & Lesscolle, (1979) and Wood, (1980), that implied all analysed samples had characteristics of volcanic arc magma composition. The EMP analysis of the pyroxene in the coherent and hyaloclastic facies of the Jovanović Draga section and in situ basaltic hyaloclastics from Bosansko Grahovo section showed that most of them are diopside and augite originated from calc-alkaline magma under low to medium pressure regimes. In addition, the diagram for the definition of the geotectonic position showed that pyroxenes from Jovanović Draga are of calc-alkaline orogenic magma origin, while pyroxenes from Bosansko Grahovo are characterized by magma of rift areas. This can mean that the more southern localities are less influenced by arc magmatism and that influence can be seen only in the geochemistry of pyroxenes. Plagioclase analysis from Zelovo locality shows that pyroclastic crystaloclasts are both normally and reversely zoned. Composition of the Na2O and CaO content vary from the core to the rim of the crystaloclasts respectively. This fact can be interpreted as constant income of the new more primitive magma (with higher CaO content) in the magma chamber from where the explosive eruptions were triggered and pyroclastic material was formed. The synthesis of all the investigated results enabled comparison of the External Dinarides with other areas of the Western Tethys (Internal Dinarides, Southern Alps, Northern Calcareous Alps, and Transdanubian Range). Most of the areas show some significant regional events or are time constrained that enable correlation between them. Almost all facies, differentiated in this work, appear with some differences, in other Western Tethyan areas. The occurrence of deeper marine facies and drowning of shallow marine carbonate sedimentary environments was recorded for the first time in the Upper Anisian (Buser, 1989; Krystyn & Lein, 1996; Gianolla et al. 1998; Missoni et al., 2001; Preto et al., 2009; Kovács et al., 2011). The main magmatic activity started in the Anisian but was the most vigorous in the Upper Anisian and Lower Ladinian (Bechstäld et al., 1978; Castellarin et al., 1988; Szoldán, 1990; Castellarin & Rossi, 1991; Obenholzner, 1991; Mundil et al., 1996; Harangi et al., 1996; Velledits, 2004; 2006; Brandner et al., 2007). As the magmatic and tectonic activity slowly abated in the Upper Ladinian, a development of the shallow marine, carbonate dominant environments had commenced (Broglio-Loriga, 1967; Keim & Neri, 2005; Manfrin et al., 2005; Bernardi et al., 2011; Lein et al., 2012; Celarc et al., 2013). Geochemical data from all neighbouring Western Tethyan areas has calc-alkaline, even shoshonitic character, not common for the supposed geotectonic setting depicted as rift (e.g. Bechstäld et al., 1978; Crisci et al., 1984; Castellarin et al., 1988; Harangi et al., 1996). The Middle Triassic rift related depositional environments, where various types of volcanoclastic rocks occurred, was also interpreted for the External Dinaridic area and documented in this work. The volcanic and volcaniclastic rocks have the same geochemical imprint as recognized in the neighbouring Tethyan areas. This fact can be explained by fitting the External Dinarides in the palinspactic reconstructions (in this work the palaeoreconstruction by Stampfli & Borel, 2003 was used). In the Middle Triassic, the External Dinarides can be located between the rift-related Tethyan domains (opening of the Tethyan Ocean from the southeast). The Tethyan rifting phase had detached the Cimmerian block while contemporaneously the subduction of the Palaeotethys to the northeast, beneath the Laurasian part of Gondwana, occurred. The formation of the several small-scale back arc rift belts was related to the subduction on the northern margin of Palaeotethys. One of these back arc rift belts developed as Meliata Ocean, bordering the Dinaridic region to the north. More to the west from Meliata an undeveloped back-arc rift belt was positioned in the area of today Exteranal Dinarides. This rift did not continue to develope the real ocean (lack of ofiolites) but due to the main Tethyan rifting trend that was intensified during Ladinian, the back-arc rift in the External Dinarides had arrested and ended as differentiated pelagic environment filled with various sedimentary material

SASTAV I PROVENIJENCIJA GREDENSKIH PJEŠČENJAKA VELEBITA

Six samples of Gröden sandstones (Middle Permian) were analysed: Five of them were from Pikovac Creek valley (in the vicinity of Brušane village at Velebit Mts., Croatia) and one was from the locus typicus Gröden/Val Gardena (Italy). Based on the micropetrographical characteristics of sandstones, as well as on the modal composition and heavy mineral association, origin of material, weathering index of source rocks, climate and relief in the period of deposition have been supposed. Four samples from Pikovac Creek were petrographicaly determined as lithic greywackes, one as densely packed lithic arenite, while a specimen from Gröden locus typicus represents feldspar greywacke. Lithic greywackes/arenites imply very low maturity and suggest a close proximity of source rocks as well as the active tectonics in the hinterland of the depositional basin. Heavy mineral association in the samples from Pikovac Creek valley, with a large amount of fairly rounded stable grains (zircon, tourmaline and rutile), indicate that clastic material was derived from recycled orogen, and probably from reworked sedimentary rocks. The presence of kyanite and chlorite in the heavy mineral assemblage suggest their origin is from metamorphic rocks. This data assumes that Gröden sandstones from Pikovac Creek were possibly deposited in the fan delta or braided delta depositional environment as a part of a rift system (recycled orogen). The composition of the sample Gröden s. locus typicus (light and heavy mineral fractions) suggests the vicinity of magmatic rocks in the source area. All analysed samples are red coloured and have a large amount of limonitized grains in the heavy mineral assemblage, that point to the arid climate at the time of deposition. A weathering index diagram for Pikovac sandstones implies an arid/semiarid climate and high relief of the source area where metamorphic or sedimentary rocks dominate, while an arid/semiarid climate and high relief with plutonic source rocks were supposed for the provenance of Gröden s. locus typicus.Analizirano je šest uzoraka srednjopermskih gredenskih pješčenjaka: pet uzoraka iz doline Pikovačkoga potoka u okolici Brušana na Velebitu i jedan uzorak s locus typicus lokaliteta Gröden/Val Gardena u Italiji. Na temelju mikropetrografskih karakteristika pješčenjaka, njihova mineralnog sastava te sastava teške i lake mineralne frakcije, interpretirano je podrijetlo materijala, indeks trošenja matičnih stijena te klima i reljef u vrijeme taloženja. Četiri uzorka pješčenjaka iz Pikovačkoga potoka petrografski su određena kao litične grauvake, a jedan uzorak kao gusto pakirani litični arenit, dok je uzorak pješčenjaka s locus typicus lokaliteta Gröden određen kao feldspatska grauvaka. Litične grauvake/areniti podrazumijevaju vrlo nisku zrelost i sugeriraju blizinu matičnih stijena, kao i aktivnu tektoniku u zaleđu sedimentacijskoga bazena. Asocijacija teških minerala u uzorcima iz Pikovačkoga potoka, s velikom količinom dobro zaobljenih stabilnih zrna (cirkon, turmalin i rutil), upućuje na to da klastični materijal potječe iz recikliranoga orogena, i to vjerojatno od pretaloženih sedimentnih stijena. Prisutnost distena i klorita u teškoj mineralnoj frakciji sugerira podrijetlo iz metamorfnih stijena. Rezultati upućuju na to da su gredenski pješčenjaci iz doline Pikovačkoga potoka možda taloženi u okolišu lepezne delte koja je dio riftnoga sustava (reciklirani orogen). Sastav lake i teške mineralne frakcije uzorka Gröden s. locus typicus sugerira podrijetlo iz magmatskih stijena. Svi analizirani uzorci crvene su boje i imaju veliku količinu limonitiziranih zrna u teškoj mineralnoj frakciji, što upućuje na aridnu klimu u vrijeme taloženja. Dijagram indeksa trošenja pješčenjaka iz Pikovačkoga potoka upućuje na aridnu/semiaridnu klimu i visoki reljef izvorišnoga područja koji je izgrađen od sedimentnih i metamorfnih stijena, dok uzorak Gröden s. locus typicus pješčenjaka ukazuje na aridnu/semiaridnu klimu i visoki reljef, s magmatskim matičnim stijenama i izvorišno područje magmatskoga luka

Composition and provenance of Gröden sandstone from the Velebit Mts.

Six samples of Gröden sandstones (Middle Permian) were analysed: Five of them were from Pikovac Creek valley (in the vicinity of Brušane village at Velebit Mts., Croatia) and one was from the locus typicus Gröden/Val Gardena (Italy). Based on the micropetrographical characteristics of sandstones, as well as on the modal composition and heavy mineral association, origin of material, weathering index of source rocks, climate and relief in the period of deposition have been supposed. Four samples from Pikovac Creek were petrographicaly determined as lithic greywackes, one as densely packed lithic arenite, while a specimen from Gröden locus typicus represents feldspar greywacke. Lithic greywackes/arenites imply very low maturity and suggest a close proximity of source rocks as well as the active tectonics in the hinterland of the depositional basin. Heavy mineral association in the samples from Pikovac Creek valley, with a large amount of fairly rounded stable grains (zircon, tourmaline and rutile), indicate that clastic material was derived from recycled orogen, and probably from reworked sedimentary rocks. The presence of kyanite and chlorite in the heavy mineral assemblage suggest their origin is from metamorphic rocks. This data assumes that Gröden sandstones from Pikovac Creek were possibly deposited in the fan delta or braided delta depositional environment as a part of a rift system (recycled orogen). The composition of the sample Gröden s. locus typicus (light and heavy mineral fractions) suggests the vicinity of magmatic rocks in the source area. All analysed samples are red coloured and have a large amount of limonitized grains in the heavy mineral assemblage, that point to the arid climate at the time of deposition. A weathering index diagram for Pikovac sandstones implies an arid/semiarid climate and high relief of the source area where metamorphic or sedimentary rocks dominate, while an arid/semiarid climate and high relief with plutonic source rocks were supposed for the provenance of Gröden s. locus typicus

SREDNJOTRIJASKE AUTOKLASTIČNE NASLAGE U OKOLICI BOSANSKOG GRAHOVA (JUGOZAPADNA BOSNA I HERCEGOVINA)

Middle Triassic volcanic and volcaniclastic rocks have been recognized at several localities near Bosansko Grahovo, in southwestern part of Bosnia and Herzegovina in the External Dinarides. Peculiar types of autoclastic rocks were investigated. These are peperites and hyaloclastites. Regarding specific structures, mineral composition and micropetrographic characteristics it was possible to further differentiate hyaloclastites into in situ hyaloclastites and slightly resedimented hyaloclastites that represent genetic succession. All rock types occurred in a deep sea troughs that formed as a consequence of Middle Triassic extensional tectonic and rift related wrench faulting. In situ hyaloclastites and slightly resedimented hyaloclastites were formed due to quenching at the contact of lava effusions with sea water. Genesis of peperites is related to lava emplacement in unconsolidated water saturated lime mudstones that were deposited in deep sea basin. All investigated rock types represent first findings of autoclastic deposits in the External Dinarides. Biostratigraphic constraints achieved by means of conodont species Neogondolella excentrica, Paragondolella excelsa, Paragondolella trammeri and Gladigondolella tethydis indicate Late Anisian to Early Ladinian interval of the autoclastic deposits from Bosansko Grahovo.U okolici Bosanskoga Grahova u jugozapadnome dijelu Bosne i Hercegovine (vanjski Dinaridi) istražen je specifičan tip vulkanoklastičnih stijena – autoklastične stijene srednjotrijaske starosti. Izdvojena su dva osnovna tipa autoklastičnih naslaga: peperiti i hijaloklastiti. Geneza peperita povezana je s procesima smještanja lave u nekonsolidirane, vodom zasićene vapnenačke madstone koji imaju karakteristike taloženja u pelagičkome okolišu. S obzirom na specifičnu teksturu, mineralni sastav i mikropetrografske karakteristike hijaloklastiti predstavljaju genetski slijed na opisanome lokalitetu Bosansko Grahovo I, te su podijeljeni na a) in situ hijaloklastite, b) neznatno pretaložene hijaloklastite i c) pretaložene hijaloklastite. In situ hijaloklastiti i neznatno pretaloženi hijaloklastiti nastali su fragmentacijom užarene lave bazaltnoga sastava u doticaju s hladnom morskom vodom, dok pretaloženi hijaloklastiti predstavljaju dominantno vulkanski detritus s kojim je pomiješana mala količina klasta vapnenaca i/ili rožnjaka, te se smatra da je detritus pretaložen nakon fragmentacije, vjerojatno, u blizini primarnih magmatskih izljeva bazaltne lave. Svi tipovi stijena označavaju magmatsku aktivnost u dubokomorskim jarcima formiranim kao posljedica srednjotrijaske ekstenzije i normalnoga rasjedanja asociranoga s procesima nastajanja rifta. Opisane autoklastične stijene prvi su pronalazak autoklastičnih naslaga u vanjskim Dinaridima. Biostratigrafska odredba temeljena na nalazima konodontnih vrsta iz vapnenaca peperita (Neogondolella excentrica, Paragondolella excelsa, Paragondolella trammeri i Gladigondolella tethydis) upućuje na kasnoanizičku do ranoladiničku starost autoklastičnih naslaga Bosanskoga Grahova, a time i na početak vulkanske aktivnosti već u aniziku

PRVI NALAZ REITZIITES REITZI MARKERA GORNJOILIRIČKE AMONITNE PODZONE U KRŠKIM DINARIDIMA

Middle Triassic deposits in the Karst Dinarides (south Lika area, near Gračac) were investigated for petrological, sedimentological and biostratigraphic determinations. Within two continuously recorded sections of sedimentary carbonates and interlayered pyroclastic rocks (Mali Kunovac and Kunovac sections) reflecting variable sedimentary-magmatic environments, valuable cephalopod fauna ranging from the middle Illyrian to the upper Illyrian age was found. The most significant was the recovery of the ammonoids Asseretoceras sp., indicating the upper part of the Illyrian Paraceratites trinodosus Zone, and Reitziites reitzi species which marks the upper part of the Illyrian Reitziites reitzi Zone. The discovery of the Reitziites reitzi species was not known from the Karst Dinarides until this finding.Srednjotrijaske naslage u krškim Dinaridima (okolica Gračaca u južnoj Lici) istraživane su s ciljem njihove petrološke i sedimentološke odredbe te odredbe njihove biostratigrafske pripadnosti. Unutar dvaju snimljenih kontinuiranih sljedova koji se sastoje od izmjene karbonatnih sedimentnih stijena i piroklastita (Mali Kunovac i Kunovac), a koji odražavaju varijabilne sedimentacijsko-magmatske okoliše njihova postanka, prikupljena je relativno malobrojna, ali vrijedna kolekcija cefalopoda srednjoiliričke i gornjoiliričke starosti. Najvažniji su nalazi amonitne vrste Asseretoceras sp. koja upućuje na gornji dio iliričke Paraceratites trinodosus zone te vrste Reitziites reitzi koja označava gornjoiliričku Reitziites zonu. Pronalazak vrste Reitziites reitzi do sada nije bio zabilježen na području krških Dinarida

Od grebena do bazena – progradacija plitkovodnih karbonata preko srednjetrijaskog riftnog bazena sjeverozapadne Hrvatske (Ivanščica, SZ Hrvatska)

The NW part of Croatia represents a tectonically complex area at the junction of the Dinarides and the Southern Alps. In Očura Quarry on Ivanščica Mt. there is 34 m thick section composed of volcanic, volcaniclastic and carbonate rocks that can be divided into three parts. The lower interval (7 m) is composed of dominantly basaltic rocks (SiO2 = 43–51 wt%). In the basal part glomeroporpyric basalt is followed by basaltic autoclastic breccia. The second interval (7–19 m) is composed of cm–dm irregularly and wavy bedded calcarenites, occasionally coarsening upward, with lithoclasts varying in size from fine sand up to fine breccia. Carbonate lithoclasts are mostly micritic limestones – biomicrite, pelmicrite, pelsparite, intrasparite, also bioclasts of bivalves, crinoids, ammonoids, brachiopods, and gastropods. Two types of basaltic lithoclasts are present in the dominantly calcarenite interval, one with the porphyric to glomeroporphyric texture, similar to the basalts of the lower part; and the other type completely hyaline. Lithoclasts are cemented by sparry calcite. In the coarser varieties lithoclasts are the same, with the only difference in the matrix found between the clasts, that is composed of fine calcarenites with basaltic lithoclasts. Calcarenites are interlayered by thin layers of biomicrites with filaments and radiolarians, and thin layers of fine to coarse ash vitriclastic tuffs. In the middle of this interval around 1.5 m thick matrix supported breccia occurs with limestone and basaltic lithoclasts. Third interval of the section (19–34 m) is composed of extremely unsorted breccia with slump texture. Clasts of limestones, calcarenites, and subordinary basalts are supported by fine grained matrix of carbonate and basaltic particles. Abundant framestone clasts are present in the breccia, containing complex reef community, dominating of sponge Celyphia zoldana, with other microorganisms of uncertain taxonomy Plexoramea cerebriformis and Olangocoelia otti, and others. Generally in this interval carbonate material is predominant over basaltic lithoclasts. The investigated section represents sedimentation in the deeper marine environment near the steep edge of the carbonate platform and reef. Basalts found at the base of the section present effusions in the marine areas, and their fragmentation and reworking. A thick interval of calcarenites with basaltic lithoclasts is formed by shedding of the carbonate material from the nearby platform to the pelagic/basinal areas, indicated by the pelagic limestone interlayers. Chaotic breccia with meter sized fragments of reefal limestones indicates a more proximal position to the shallow marine area from which these clasts were derived. Slump texture emphasizes gravitational processes. The general trend of coarsening upward, as well as the predominance of the framestone clasts in the breccias imply the progradation of the platform over the basinal areas. Therefore, indicating a relatively rapid closure of the basinal/pelagic areas and cessation of the extensional tectonics related to the Neotethyan rifting. One sample (OD-15A) bears conodonts Gladigondolella tethydis (Huckriede), Paragondolella trammeri (Kozur), that indicate Illyrian to Lower Longobardian age of this section. That age is in the accordance with the regional cessation of the volcanic activity in the Ladinian, and progradation of the platforms over the basinal areas that were filled with various clastic, volcaniclastic, silicious and pelagic sediments

Middle Triassic syntectonic sedimentation and volcanic influence in the central part of the External Dinarides, Croatia (Velebit Mts.)

Middle Triassic deposits in the Velebit Mts. of the External Dinarides in Croatia show strong differentiation of sedimentary environments and facies. In the area of Donje Pazarište, a 90 metre thick section includes six different facies, each with its specific genetic characteristics (Flysch-like Facies ; Carbonate Shale Facies ; Pyroclastic Density Current Facies ; Platy Limestone with Pyroclastics Facies ; Limestone Breccia Facies and Slumped Limestones with Pyroclastics and Chert Facies). In the same area, in the nearby Top of Donje Pazarište section, a Pyroclastic Flow Facies was defined, and this was also recognized ~15 km to south-east, in the area of Brušane village, in the foothills of Vinac. Throughout the area and section investigated, the effects of intense tectonic and volcanic activity can be traced. The pronounced differences in the facies determined facies are interpreted as consequences of syntectonic and volcanically influenced sedimentation in a graben/half- graben depositional system

Gornjotrijaski litofacijesi na lokalitetu Lokve u Gorskom kotaru – indikatori paleookolišnih i paleoklimatskih promjena

The Upper Triassic deposits in the entire Western Tethys realm are widely recognized in the form of the Main Dolomite (Hauptdolomit/Dolomia Principale). However, the lower part of the Upper Triassic is lithologically more diverse, and of variable thicknesses, sometimes even missing in the External Dinarides. It is represented by different lithofacies ranging from fine to coarse grained clastics, marls, limestones, dolomites as well as coal and bauxite occurrences. This heterogeneous lithology archives several palaeoclimatic events that punctuated the otherwise predominantly arid monsoonal regime of the Late Triassic. On such climatic episode in the lower part of the Carnian ( Julian 2–Tuvalian 2), is the Carnian Pluvial/Humid Episode (CPE, SIMMS & RUFFELL 1989; RUFFELL et al., 2016); a rather short episode of climatic change, indicated by a shift from arid to relatively more humid conditions, an enhanced hydrological cycling, and increased weathering intensity linked to global carbon cycle perturbations triggered by large-scale volcanism (e.g., DAL CORSO et al., 2020). The CPE is distinguished in the sedimentary record as a period of intensive weathering and clastic influx into the marine realm, paralleled by a reduced carbonate deposition, as well as coal or bauxite accumulation on land. The aim of this research was to identify this climatic episode in the Lokve section, Gorski Kotar area, in the External/ Karst Dinarides with the help of petrography, clay mineral analysis and palynology. In this area, the Upper Triassic strata directly lays on Permian siliciclastics (SAVIĆ & DOZET, 1983). The recorded Upper Triassic succession is composed of sandstones, followed by an interval of red shale and dolomite intercalations, as well as grey shales between dolomite layers, and finally well-bedded dolomites in its uppermost part. Sandstones are determined as feldspar arenites to greywackes. They are composed of angular to rounded clasts and exhibit good sorting. The matrix is composed of clay minerals which are cemented by calcite. The shales are irregularly laminated, with very dispersed irregular dark laminae. Only rare quartz silt-size clasts are observed. Dolomites are mostly primary with well-preserved textures and alochem fabrics. Four types of dolomites are determined: dolomicrite, dolobiomicrite, dolobiosparite and dolobiolitite. XRD analysis of shales and sandstones showed a general increase in micaceous and clay minerals, coupled with a decrease in albite, hematite, and quartz along the section. Among the clay minerals only chlorite was distinguished, but no kaolinite was recognized. The increase in carbonate sedimentation is interpreted as stabilization of the sedimentary environments, and cessation of siliciclastic input. Decrease in grains size of clastic component up section indicates more quiet environments and possibly more distal position on the stabilized shelf. The increase in clay sized particles is also related to the increase in micaceous minerals, and consequently to the decrease in quartz content. Although K-feldspar and plagioclase were recognized in XRD analysis, the lack of kaolinite, as a weathering product of such minerals indicates the climatic conditions were not humid tropical but rather warm arid. Change in shale colour, from red to grey is related to the reduction of iron, as the red clastic bare hematite, and in the grey shales pyrite is recognized. The “Carnian Pluvial Episode” sediments have some similar characteristics with the recorded Lokve section, but clear evidence for such an episode is not seen here. The Lokve section probably represents a younger Upper Triassic stratigraphic interval, representing the stabilization of carbonate production and deposition of the regionally recognized Main Dolomite

Od grebena do bazena – progradacija plitkovodnih karbonata preko srednjetrijaskog riftnog bazena sjeverozapadne Hrvatske (Ivanščica, SZ Hrvatska)

The NW part of Croatia represents a tectonically complex area at the junction of the Dinarides and the Southern Alps. In Očura Quarry on Ivanščica Mt. there is 34 m thick section composed of volcanic, volcaniclastic and carbonate rocks that can be divided into three parts. The lower interval (7 m) is composed of dominantly basaltic rocks (SiO2 = 43–51 wt%). In the basal part glomeroporpyric basalt is followed by basaltic autoclastic breccia. The second interval (7–19 m) is composed of cm–dm irregularly and wavy bedded calcarenites, occasionally coarsening upward, with lithoclasts varying in size from fine sand up to fine breccia. Carbonate lithoclasts are mostly micritic limestones – biomicrite, pelmicrite, pelsparite, intrasparite, also bioclasts of bivalves, crinoids, ammonoids, brachiopods, and gastropods. Two types of basaltic lithoclasts are present in the dominantly calcarenite interval, one with the porphyric to glomeroporphyric texture, similar to the basalts of the lower part; and the other type completely hyaline. Lithoclasts are cemented by sparry calcite. In the coarser varieties lithoclasts are the same, with the only difference in the matrix found between the clasts, that is composed of fine calcarenites with basaltic lithoclasts. Calcarenites are interlayered by thin layers of biomicrites with filaments and radiolarians, and thin layers of fine to coarse ash vitriclastic tuffs. In the middle of this interval around 1.5 m thick matrix supported breccia occurs with limestone and basaltic lithoclasts. Third interval of the section (19–34 m) is composed of extremely unsorted breccia with slump texture. Clasts of limestones, calcarenites, and subordinary basalts are supported by fine grained matrix of carbonate and basaltic particles. Abundant framestone clasts are present in the breccia, containing complex reef community, dominating of sponge Celyphia zoldana, with other microorganisms of uncertain taxonomy Plexoramea cerebriformis and Olangocoelia otti, and others. Generally in this interval carbonate material is predominant over basaltic lithoclasts. The investigated section represents sedimentation in the deeper marine environment near the steep edge of the carbonate platform and reef. Basalts found at the base of the section present effusions in the marine areas, and their fragmentation and reworking. A thick interval of calcarenites with basaltic lithoclasts is formed by shedding of the carbonate material from the nearby platform to the pelagic/basinal areas, indicated by the pelagic limestone interlayers. Chaotic breccia with meter sized fragments of reefal limestones indicates a more proximal position to the shallow marine area from which these clasts were derived. Slump texture emphasizes gravitational processes. The general trend of coarsening upward, as well as the predominance of the framestone clasts in the breccias imply the progradation of the platform over the basinal areas. Therefore, indicating a relatively rapid closure of the basinal/pelagic areas and cessation of the extensional tectonics related to the Neotethyan rifting. One sample (OD-15A) bears conodonts Gladigondolella tethydis (Huckriede), Paragondolella trammeri (Kozur), that indicate Illyrian to Lower Longobardian age of this section. That age is in the accordance with the regional cessation of the volcanic activity in the Ladinian, and progradation of the platforms over the basinal areas that were filled with various clastic, volcaniclastic, silicious and pelagic sediments