Sedimentological and mineralogical properties of recent sediments of Plitvice Lakes : master's thesis

Cilj ovog diplomskog rada bio je istražiti granulometrijske, mineraloške te morfološke značajke recentnih sedimenata Plitvičkih jezera. Analizirani su uzorci iz jezgri sedimenata s četiri lokaliteta u jezeru Prošće, tri lokaliteta u jezeru Kozjak, te s jednog lokaliteta u Matici, Gradinskom jezeru i jezeru Kaluđerovac. Za određivanje granulometrijskih značajki sedimenta korištena je metoda laserske difrakcije (LD), mineraloški sastav određen je rendgenskom difrakcijom na prahu (XRD), a morfološke značajke sedimenta istražene su primjenom pretražne elektronske mikroskopije s visokim razlučivanjem (FE-SEM). Prema klasifikacijskom modelu koji je predložio Shepard (1954) sedimenti Gradinskog jezera svrstani su u grupu pijeska, sedimenti jezera Kozjak u grupu silta, a sedimenti Matice i Prošća u grupu pjeskovitog silta. U karbonatnom precipitatu iz Matice i mladoj sedri iz jezera Galovac jedina dominantna mineralna faza je visoko kristalizirani kalcit, uz koji se pojavljuju male količine dolomita. Sedimenti jezera Kozjak sadrže približno 95 % kalcita, te manje količine dolomita i kvarca. Najzastupljenije čestice kalcita u recentnim sedimentima imaju značajke mezokristalnih struktura što ukazuje na procese formiranja kalcitne mineralne faze iz vodenog sustava. U Matici je u kalcitnim mineralnim prevlakama uočena pojava cijanobakterija, što ukazuje na njihov značaj u biološki induciranim procesima formiranja kalcita.Abstract: This thesis provides granulometrical and mineralogical properties of recent sediments from the Plitvice Lakes. Sediment cores were collected at four stations from the Lake Prošće, three stations from the Lake Kozjak and one station from the Matica, the Gradinsko Lake and the Lake Kaluđerovac. Sediment samples were granulometrically characterized by laser diffraction (LD), identification of mineral composition was performed by X-ray powder diffraction (XRD) and morphological properties of particles were analyzed by field emission scanning electron microscopy (FE-SEM). Considering the ratio of different grain size fraction (Shepard, 1954), sediment from the Gradinsko lake was classified as sand, sediment from the Kozjak Lake was classified as silt, while the sediments from the Matica and the Prošće Lake were classified as sandy-silt. The dominant mineral phase in tufa from the Matica and the Galovac Lake was highly crystallized calcite with partial appearance of dolomite. The recent sediments from the Kozjak Lake consist of approximately 95 % calcite and a small amount of dolomite and quartz. The most common morphology of calcite particles found in sediment was mesocrystal shape, which exemplifies the role of biologically induced inorganic precipitation processes in their formation. The appearance of cyanobacteria in the precipitates of the Matica indicated the significance of cyanobacteria in formation of calcite solids