Crystalline rocks are generally characterized by negligible porosity and permeability in terms of groundwater exploitability. However, alteration processes can greatly increase their fracture ...permeability and induce formation of modest, but locally important aquifers. Therefore, subsurface characteristics of alteration zones are of major importance for hydrogeological evaluation of crystalline terrains. Alteration processes greatly affect rock total porosity and water content, causing contrasting electrical resistivity of rocks affected by varying degrees of weathering. This makes electrical resistivity tomography (ERT) a preferable geophysical method for the exploration of alteration zones in crystalline rocks. In our research, we used an integrated approach, combining the ERT method with monitoring of spring discharge and hydrochemistry to characterize metamorphic aquifers on slopes of the Medvednica Mountain (Croatia). Significant fracture flow aquifers are found to be formed in intensely fractured but not highly weathered rock masses (medium to high resistivity values), while highly weathered masses (low resistivity values) form local barriers for fracture flows. Subsurface structure of the alteration zone proved to be highly irregular, with sharp contacts between more and less weathered rocks. Decrease of permeability below the alteration zone keeps the water level near the surface and enables spring occurrence on the mountain slopes. Studied aquifers have relatively limited extent, resulting in typical capacity of major springs of a few l/s. More frequent but less productive springs are attributed to the draining of the shallow part of the alteration zone (mostly saprolite). Combination of the ERT method with spring monitoring proved to be very effective as a first and relatively inexpensive methodology for hydrogeological characterization of crystalline terrains, both in local and catchment scales.
This paper addresses the role of Medvednica Mountain streams in the past and present spatial planning of the City of Zagreb. A description of their main characteristics is followed by an examination ...of their historical role in spatial planning and spatial plans, and of their impact on the urbanisation of Zagreb over four characteristic periods from the second half of the 19th century to the time of writing. A survey was also conducted to determine the ways in which the people of Zagreb use these streams and their views on their potential development. The international practice of planning and management of urban streams is explained in selected examples. Finally, on the basis of the survey, field research, and a synthesis of foreign and domestic planning practice and literature, the authors summarise the results and findings of the research.
Park prirode Medvednica, kao zelena oaza nadomak glavnog grada, iznimno je vrijedan resurs za opuštanje i rekreaciju stanovništva grada Zagreba u prirodnom okruženju, ali i sve značajnija atrakcija ...za turiste koji posjećuju grad Zagreb i okolicu. Kako su pritisci na taj zaštićeni prostor sve izraženiji u urbanističkom, sportskorekreacijskom i turistički razvojnom smislu, smatralo se važnim ispitati stavove i percepciju stanovnika grada Zagreba prema razvoju zimskog sportskog turizma na području Parka. Podaci za ovo kvantitativno istraživanje prikupljeni su anketnim ispitivanjem na uzorku od 309 stalnih stanovnika grada Zagreba. Istraživanje je pokazalo da stanovnici hrvatske metropole zimi često posjećuju Park te da taj prostor ipak ima veći značaj i vrijednost za gradsko stanovništvo, nego kao turistička atrakcija za privremene posjetitelje. Iako velika većina ispitanika smatra kako su ekonomske koristi od zimskog sportskog turizma od velikog značaja za očuvanje Parka i njegov daljnji razvoj, svjesni su da takav razvoj vrši dodatan pritisak na održivost zaštićenog područja. Među ograničenjima daljnjeg razvoja zimskog sportskog turizma ispitanici primarno vide u ograničenom prostornom kapacitetu i nedostatnoj infrastrukturi, ali i u neizbježnim klimatskim promjenama koje štetno utječu na redovitost održavanja međunarodnih skijaških utrka i imidž Medvednice kao destinacije zimskog sportskog turizma. Nalazi ovog istraživanja ukazuju na potrebu povećane brige o raspoloživim resursima, kao i pomnog promišljanja o mogućnostima i posljedicama daljnjeg razvoja zimskog sportskog turizma na promatranom prostoru. Originalnost ovog rada očituje se u dizajnu istraživanja i njegovoj primjeni na specifičnom prostoru, što do sada u tom obliku nije znanstveno istraživano.
U radu su dani prikaz i usporedba satelitskih informacija srednje (Landsat 8, 30 m) i visoke (RapidEye, 5 m) rezolucije radi ispitivanja mogućnosti vizualne i kvantitativne procjene šteta od ...vjetroizvala na Medvednici, nakon oluje Teodor u studenome 2013. godine, te obnove šumskog pokrova u 2018., odnosno nakon pet godina. Za vizualnu detekciju šteta na čitavom području korišten je 3D prikaz, u 15 m prostornoj rezoluciji, izveden iz RGB kanala vidljivog dijela spektra, izoštren pomoću pankromatskoga kanala. Prostorna razlučivost različitih satelitskih indeksa (NDVI, SAVI, MSAVI, NDMI, NBR, NBR2), kao kvantitativne mjere stanja vegetacijskog pokrova, ispitivana je na temelju snimaka Landsat 8 na čitavom području Medvednice. Od ispitivanih indeksa najbolja razlučivost vegetacijskog pokrova postignuta je na korigiranim SAVI i MSAVI indeksima u odnosu na NDVI, dok su indeksi temeljeni na infracrvenom dijelu spektra (NDMI, NBR, NBR2) pokazali dosta dobru osjetljivost pri detekciji narušenosti šumskog pokrova nakon vjetroizvala. Na ispitivanom dijelu površine s vjetroizvalom, neposredno uz potok Bliznec, utvrđena je znatna komparativna prednost snimaka visoke rezolucije (RapidEye) pri razlučivanju šteta na pokrovu odnosno pri praćenju stanja obnove šumske vegetacije. Na osnovi dobivenih prethodnih rezultata utvrđene su znatne mogućnosti satelitskih snimaka srednje i visoke rezolucije, kako u svrhu detekcije šteta nakon prirodne nepogode, tako i pri praćenju obnove šuma na tim površinama, što će potvrditi daljnji tijek ovog istraživanja.
Extensive and protracted volcanism in the Carpathian-Pannonian Region climaxed during the Early to Middle Miocene with series of major ignimbrite-forming eruptions with their products dispersed ...across the Alpine-Mediterranean Region. The spatial and temporal dispersion of these volcanic horizons make them potentially important stratigraphic markers throughout the region, allowing better understanding of temporal and spatial changes in depositional environments and paleoclimate. Several of these Middle Miocene volcaniclastic layers are preserved in stratigraphically and environmentally variable sedimentary facies on Mt. Medvednica, located in the North Croatian Basin. In order to decipher the age, depositional environment and provenance of two volcaniclastic horizons intercalated within Central Paratethys marine sediments on Mt. Medvednica, we applied an integrated approach of volcanological, geochronological, and paleontological analyses. New high-precision zircon geochronology and volcanic glass geochemistry data allow to distinguish two primary rhyolitic volcaniclastic horizons derived from distinct eruptions, “Plaz“, and the “Bidrovec“, dated at 14.937 ± 0.012 Ma and 14.835 ± 0.012 Ma. Distinguished mineralogical and geochemical data enabled the correlation of the older (“Plaz”) horizon on Mt. Medvednica with the Demjén eruption, one of the six major Early–Middle Miocene ignimbrite-forming eruptions of the Carpathian-Pannonian Region. However, a correlation of the younger (“Bidrovec“) horizon and assignment to a specific eruption could not be established due to a lack of compositional data from coeval eruption products throughout the region. The newly gathered data establishes both “Plaz” and “Bidrovec” pyroclastic deposits as valuable marker horizons for regional reconstructions, and enable a better understanding of the eruption chronology and tephrostratigraphy of the Carpathian-Pannonian Region.
•Mt. Medvednica volcaniclastic horizons were emplaced at ∼14.94 Ma and ∼ 14.84 Ma.•Primary volcaniclastic deposits were deposited in Central Paratethys environments.•∼14.94 Ma horizon can be related to Demjén eruption of the Carpathian-Pannonian Region.•∼14.84 Ma horizon is coeval with several regionally spread volcaniclastic horizons.•Better understanding of the regional widespread eruption history and tephrostratigraphy is enabled.
On 22 March 2020, Zagreb was struck by an M5.5 earthquake that had been expected for more than 100 years and revealed all the failures in the construction of residential buildings in the Croatian ...capital, especially those built in the first half of the 20th century. Because of that, extensive seismological, geological, geodetic and structural engineering surveys were conducted immediately after the main shock. This study provides descriptions of damage, specifying the building performances and their correlation with the local soil characteristics, i.e., seismic motion amplification. Co-seismic vertical ground displacement was estimated, and the most affected area is identified according to Sentinel-1 interferometric wide-swath data. Finally, preliminary 3D structural modeling of the earthquake sequence was performed, and two major faults were modeled using inverse distance weight (IDW) interpolation of the grouped hypocenters. The first-order assessment of seismic amplification (due to site conditions) in the Zagreb area for the M5.5 earthquake shows that ground motions of approximately 0.16–0.19 g were amplified at least twice. The observed co-seismic deformation (based on Sentinel-1A IW SLC images) implies an approximately 3 cm uplift of the epicentral area that covers approximately 20 km2. Based on the preliminary spatial and temporal analyses of the Zagreb 2020 earthquake sequence, the main shock and the first aftershocks evidently occurred in the subsurface of the Medvednica Mountains along a deep-seated southeast-dipping thrust fault, recognized as the primary (master) fault. The co-seismic rupture propagated along the thrust towards northwest during the first half-hour of the earthquake sequence, which can be clearly seen from the time-lapse visualization. The preliminary results strongly support one of the debated models of the active tectonic setting of the Medvednica Mountains and will contribute to a better assessment of the seismic hazard for the wider Zagreb area.
•Clay minerals in soils formed from marls in temperate climate were studied.•High pH hampers pronounced clay minerals transformation.•Clay minerals in soils are mainly inherited from parent ...material.•Slight changes detected in mixed-layered clay minerals and interlayer space.
Five young soil profiles, formed from Miocene marls and argillaceous limestone, were investigated to determine changes in their clay mineralogy. Soil profiles were described, sampled, and their basic properties analyzed (particle size distribution, pH, cation exchange capacity (CEC), CaCO3 and organic C contents). The soils were classified according to the WRB classification as: 1) Calcaric Mollic Leptosol (Humic); 2) Calcaric Lithic Leptosol (Humic); 3) Calcaric Regosol (Loamic, Relocatic); 4) Calcaric Regosol (Siltic); and 5) Calcaric Cambisol (Densic, Endoloamic, Episiltic). Mineralogy was determined via X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) on bulk samples and clay fractions, and chemical composition was determined by inductively coupled plasma emission spectroscopy (ICP-ES). Calcite, quartz and some plagioclase alongside phyllosilicates were identified in parent material. Dolomite was found in the parent material of younger age. Clay fraction from parent material consists of expandable clays (smectite-rich illite-smectite and vermiculite), illite and kaolinite, with chlorite present in younger parent materials. In most soil horizons dissolution and leaching of less stable phases (calcite, dolomite, chlorite) occurred. Initial stage soil formation is consistent with the dominant influence of parent rock mineralogy on soil clay mineral assemblage. Analyses showed substantial homogeneity between and within profiles; nevertheless, slight changes in the clay mineralogy were noted: decrease of illite layers in illite-smectite in topsoil samples and occurrence of mixed-layered chlorite-vermiculite and/or hydroxyl or organic matter interlayering in soil horizons. Chemical composition of bulk samples indicated mobility only of alkali elements, confirming weak chemical weathering. The results show slight changes in clay mineralogy, which can be detected in young soils developed from calcareous parent material under high pH conditions. Those weak alterations of parent clay minerals assemblage, often through unstable phases, can modify soil properties, but are also indicators of subtle clay transformation in calcareous soils in temperate climate.
Hectometric blocks of Middle Triassic mafic pyroclastic rocks, represented by volcanic agglomerates/breccias and lapilli tuffs, form part of the ophiolitic mélange of Mt. Medvednica, situated in the ...southwestern segment of the Zagorje-Mid-Transdanubian Zone. These rocks share petrochemical characteristics with pyroclastic derivatives of alkali, within-plate basaltic lavas of Mts. Medvednica, Samoborska Gora, and Kalnik, indicating the occurrence of explosive events preceding the dominant effusive submarine volcanism during the Middle Triassic (Illyrian-Fassanian?) stages. The formation of these pre-ophiolitic pyroclastics is associated with an intracontinental rift setting and reflects melts derived from an OIB-type enriched mantle plume source. These pyroclastics represent uncontaminated melts that erupted through a highly thinned continental crust. In geodynamic terms, the formation of pyroclastites occurred during the Late Anisian-Early Ladinian along the continental margin of Palaeotethys through the proto back-arc rifting of continental lithosphere (Adria Plate), leading to the formation of the Maliak/Balkan Neotethys Rift, in the emerging northwestern segment of Neotethys. The investigated pyroclastic rocks of Mt. Medvednica document the extension in an evolved intracontinental rift basin, which immediately preceded the generation of the initial Neotethyan oceanic lithosphere during the Upper Triassic.
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