Provider: - Institution: - Data provided by Europeana Collections- 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 hyaloclasti