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Impact of Input Data on the Quality of the Landslide Susceptibility Large-Scale Maps: A Case Study from NW Croatia
No full textAbstract The study presents analyses of input data impact on the quality of the landslide susceptibility large-scale maps. For comparison, two input data sets were used to produce two landslide susceptibility maps. The first input data set included free-available, small-scale data with low spatial accuracy, while the second set included high-resolution remote sensing data. The same nine types of landslide causal factors were derived and used for susceptibility analyses. Furthermore, LiDAR-based landslide inventory and bivariate statistical method, i.e. Information Value method, were used for susceptibility modelling. The resulting landslide susceptibility maps were compared with ROC curves. Success and prediction rates showed that the landslide susceptibility model based on causal factors derived from high-resolution remote sensing data is approximately 10% more accurate than the model based on causal factors derived from small-scale input data. Furthermore, based on the conducted research, it can be concluded that susceptibility modelling based on small-scale data and LiDAR-based inventories enables reliable landslide susceptibility assessments at the regional level
Transformation of geological maps from Gauss-Krüger projection to HTRS96/TM projection : master's thesis
No full textIzrađena je transformacija osnovnih geoloških karata lista Zagreb i Ivanić Grad. Te karte se nalaze u Gauss-Krügerovoj projekciji te se ne poklapaju sa službenom projekcijom republike Hrvatska, a to je HTRS96/TM. Karte su uređivane u programu QGIS 3.24.2. Također, u tom programu je kreirana vlastita Helmertova 7-parametarska transformacija i vlastita projekcija s određenim parametrima. Nakon transformacije karata, vjerodostojnost transformacija provjerena je i uspoređena s podacima koji su preuzeti s Državne geodetske uprave. Ovakve vrste transformacija i rada u QGIS-u velika su pomoć za razne zadatke s kojima se susreću geolozi te im omogućuju jednostavnu upotrebu.A transformation of basic geological maps for the Zagreb and Ivanić Grad sheets has been carried out. These maps were in the Gauss-Krüger projection and did not match the official projection of the Republic of Croatia, HTRS96/TM. The maps were edited using QGIS 3.24.2 software. Additionally, a custom Helmert's 7-parameter transformation and a custom projection with specific parameters were created in the program. After the transformation of the maps, the credibility of the transformations was checked and compared with data obtained from the State Geodetic Administration. Such types of transformations and work in QGIS greatly assist various tasks encountered by geologists, enabling them to work with ease
Stop 1: Rovinj-1 deposit – Lower Kimmeridgian – upper Tithonian unconformity
No full textThe 1st stop represents one of the best outcrops of the 1st unconformity. The unconformity between the Oxfordian to lower Kimmeridgian and upper Tithonian carbonate deposits is marked with the formation of a large bauxite body up to 20 metres thick – the Rovinj-1 bauxite deposit, which is currently the only operating bauxite mine in Croatia. However, the bauxite ore is not used for aluminium production due to its high silica content but is currently used as a secondary ore in the production of mineral wool. With estimated reserves of around 15 million tonnes, it is also one of the largest bauxite deposits in Croatia
Mineralni sastav, gustoća, prostorna masa, poroznost i upijanje vode amfibolita s lokaliteta Vetovo (Papuk, Slavonija, Republika Hrvatska) : završni rad
No full textPredmet istraživanja rada su uzorci amfibolita iz kamenoloma Vetovo (Papuk, Slavonija). Na tri uzorka, V-I-8, V-I-9, V-I-14/1, provedena su istraživanja mineraloško-petrografskog sastava i određivanja sljedećih fizičkih svojstava: gustoće, prostorne mase, poroznosti i upijanja vode. Glavni minerali primarne metamorfne parageneze u sva tri uzorka su hornblenda i plagioklas. Uzorci V-I-8 i V-I-9 imaju vrlo sličan mineralni sastav te uz hornblendu i plagioklas sadrže kvarc, titanit, epidot, klinozoisit, klorit, tinjčasti mineral (sericit/ilit), kalcit i opàke minerale dok se uzorak V-I-14/1 razlikuje po većoj količini kvarca i dodatno sadrži biotit u odnosu na druga dva uzorka. Struktura sva tri uzorka je granonematoblastična, a tekstura trakasta. Uzorak V-I-9 ima nešto manju gustoću (3,07 g/cm3) u odnosu na uzorke V-I-8 (3,18 g/cm3) i V-I-14/1 (3,10 g/cm3). Svi uzorci imaju malu relativnu poroznost i malo upijanje vode, manje od 0,5 %, što se smatra vrlo niskim upijanjem te su na temelju toga pogodni za uporabu kao kameni agregati pri izradi pješačko-kolničkih konstrukcija, za gornji habajući sloj
Naturally occuring botryoidal carbonates in a Holocene karst paleolake Prološko Blato (Dalmatia, Croatia)
No full textThe Prološko Blato is a seasonal karst wetland in the NW part of the Imotsko polje (karst polje) in the Dalmatian hinterland. Ongoing paleolimnological research revealed the existence of Holocene paleolake sediments made of pale brown lacustrine carbonate, rich in gastropods and ostracods, that started to form at ca. 8000 cal yr BP. Multiproxy core analysis, including geochemical, sedimentological, and micropaleontological (ostracods), suggests a relatively shallow, oligotrophic lacustrine environment with continuous carbonate sedimentation until ca. 800 cal BP. Specific to this karstic paleolake is the occurrence of enigmatic botryoidal carbonates initially detected in coarser sieved fractions (>250 um) during the ostracod analysis, and confirmed via SEM analysis. In micropaleontological slides, botryoidal grains occur as plate-like forms, flat on one side and botryoidal (spherical) on the other, implying their growth on a fixed substrate. SEM analysis revealed that botryoidal grains are made of acicular crystals, similar to the needle-like aragonite, exhibiting two distinctive spherulitic forms: a) spherules made of needles radially spreading from the central point outwards, and b) spherules made of needles radially arranged around a circular void. This potentially implies the same formation process, but different stages of development of needle-like crystals. Botryoidal carbonates are numerous in specific samples throughout the paleolake record, which could possibly be used as a proxy for paleoenvironmental interpretation. However, their origin (organic vs. inorganic, diagenetic) and environmental conditions necessary for their formation remain to be investigated
Measurements of thermal conductivity of rocks at locations in the Croatian part of the Pannonian basin : master's thesis
No full textU sklopu ovog rada provedeno je ukupno 16 mjerenja toplinske vodljivosti stijena na tri lokacije, od kojih se dvije nalaze u istočnom dijelu Dravske depresije. Mjerenja su izvedena metodom iglene sonde (engl. Single Needle Probe), koristeći uređaj Thermal Properties Analyzer. Pet točaka mjerenja je izvedeno unutar lapora, a po jedna točka unutar gnajsa, biokalkarenita, filita i biokalkarenita do biokalkrudita Dobiveni rezultati su uspoređeni s podatcima iz literature te je uočeno da se većina izmjerenih vrijednosti toplinske vodljivosti nalazi unutar prosječnog intervala vrijednosti za određenu vrstu stijene. Poneka odstupanja određenih izmjerenih vrijednosti se vrlo vjerojatno mogu prepisati malo drugačijem mineralnom sastavu stijene za koje su dane vrijednosti u literaturi u odnosu na stijene ispitane u okviru ovoga rada. Osim toga, razlike su vjerojatno utjecane i različitim uvjetima mjerenja. Potrebna su daljnja istraživanja kako bi se vrijednosti korigirale za utjecaje saturacije fluidima koje se očekuju u podzemlju.As part of this work, a total of 16 measurements of thermal conductivity of rocks were carried out at three locations, two of which are located in the eastern part of the Drava Depression. The measurement was performed using the Single Needle Probe method, using the Thermal Properties Analyzer device. Five measurement points were made inside marl, and one point each inside gneiss, biocalcarenite, phyllite and biocalcarenite to biocalcrudite. The obtained results were compared with data from the literature and it was assessed that most of the measured thermal conductivity values are within the average value interval for a certain type of rock. A few deviations of certain measured values can very likely be attributed to the slightly different mineral composition of the rocks for which the values are given in the literature compared to the rocks examined in this work. In addition, the differences are probably due to different influences and measurement conditions. Further research is needed to correct the values for the influence of fluid saturation expected in the subsurface
Paleoenvironmental and paleoclimatic changes during the deposition of Upper Jurassic bauxites and their immediate cover: case study of the Rovinj bauxite pit, Istria, Croatia
No full textThe aim of this study was the reconstruction of paleoclimatic and paleoenvironmental changes which occurred during the deposition of Upper Jurassic bauxite, and their cover beds, which comprise a cyclic alternation of clays, limestones, and black pebble breccias. Clay and bulk mineralogy, geochemistry and micromorphology of bauxites and clays was studied using XRPD, SEM-EDS, ICP-MS, XRF, AAS and petrography. The bauxite is composed from haematite, boehmite and kaolinite with variable amounts of 14 Å clay, illite and titanium oxides. The composition of major oxides is consistent with the mineralogical composition and is uniform throughout the profile. The values of rare earth elements and variations in the trace element values displayed differences throughout the bauxite profile, distinguishing two bauxite sections, both capped by two clay illuviation rich horizons. The upper section has numerous erosional features and clastic bauxite beds, which when coupled with its different trace elemental fingerprint indicates its deposition over the older pelitomorphic section. This change is likely a consequence of a paleoclimatic shift towards a more seasonal climate during the formation of the younger part of the bauxite. This can be related to the oscillating transgression succeeding the bauxite formation, which is recorded in the cyclical beds covering the bauxite. The clays from the cover beds are composed from dioctahedral vermiculite, kaolinite, illite and a mixed-layer clay mineral (MLCM) consisting of illite and dioctahedral 14 Å phyllosilicate. The increase in illite and MLCM over kaolinite and the increase in Sr/Ba ratio along the profile, indicate a change from a lacustrine towards a marine environment. The iron speciation data supports this, as it recorded the redox changes which indicate a transition from a closed lacustrine environment to an open marine environment. Overall, the study of both bauxites and their cover, allowed a detailed reconstruction of a late Kimmeridgian transgression that followed a terrestrial phase in this part of the Adriatic carbonate platform. This work has been fully supported by Croatian Science Foundation under the project IP-2019-04-8054 – Wian- Lab (Western Istrian Anticline as an Ideal Natural Laboratory for the Study of the Regional Unconformities in Carbonate Rocks)
Numerical modeling of cover colapse sinkholes – case study : master's thesis
No full textNakon potresa magnitude 6.4, koji se dogodio 29. prosinca 2020. godine s epicentrom u Petrinji pojavilo se preko 100 pokrovno-urušnih vrtača na površini od približno 1 km2 tijekom nekoliko mjeseci od potresa. Geotehnički istražni radovi na promatranom području izvedeni su početkom 2021. godine. Analizirani su postojeći geološki i hidrogeološki podaci te su zabilježene geometrije vrtača. U blizini najveće vrtače, koja se nalazila u Mečenčanima, izvedene su dvije istražne bušotine s kontinuiranim jezgrovanjem. U istim bušotinama izveden je standardni penetracijski pokus. Naknadno su izvedena i laboratorijska ispitivanja fizikalnih, indeksnih i projektnih svojstava tla. Modeliran je karakterističan profil tla, za najveću vrtaču, koji je korišten za numeričke analize kako bi se ispitali mogući mehanizmi loma te izvršile parametarske analize radi utvrđivanja ovisnosti utjecaja geometrije i stanja naprezanja na nastanak pokrovno-urušnih vrtača.After the magnitude 6.4 earthquake that occurred on December 29, 2020, with its epicentre in Petrinja, more than 100 cover-collapse sinkholes appeared over an area of approximately 1 km2 in the months following the earthquake. Geotechnical site investigations were carried out in the area affected by the earthquake in early 2021. Existing geological and hydrogeological data were analysed, and the geometries of the sinkholes were recorded. Two exploratory drillings with core sampling were conducted near the largest sinkhole, located in the Mečenčani village. Standard penetration tests were performed in the same boreholes. Subsequently, laboratory tests of physical, index, and engineering properties were conducted. A typical soil profile was modelled for the largest sinkhole, which was used for numerical analyses to investigate potential failure mechanisms and perform parametric analyses to determine the dependencies of the influence of geometry and stress conditions on the formation of cover-collapse sinkholes
Circles related to a complete quadrangle
No full textThis paper presents an overview of some properties of a complete quadrangle ABCD in the Euclidean plane. We study the circles with diameters AB, AC, AD, BC, BD, and CD, as well as the pedal triangles and the pedal circles of the points A, B, C, D with respect to the triangles BCD, ACD, ABD and ABC, respectively. The presented results are known in literature, but here we prove them using a single method