Mineralogical, geochemical and micromorphological charasteristics of cretaceous paleosol in the Tri jezerca quarry : master's thesis

Cilj istraživanja bio je određivanje mineraloških, geokemijskih i mikromorfoloških karakteristika, te porijekla emerzijskog glinovitog sedimenta/paleotla smještenog između druge i treće megasekvencije na Istarskom poluotoku u kamenolomu Tri jezerca, kraj mjesta Selina. Teška i laka mineralna frakcija analiziranog sedimenta ukazuju na matične stijene metamorfnih i ofiolitnih kompleksa, a također i na vulkanski pepeo. Tri moguća izvorišta nekarbonatnog matičnog materijala istraživanog sedimenta su: netopivi ostatak vapnenca, vulkanski pepeo i eolski materijal. Netopivi ostatak vapnenca iz podine istraživanog sedimenta zasigurno je sudjelovao u formiranju istraživanog sedimenta kao izvorišni materijal, no njegov udio je vrlo mali u odnosu na druga dva izvorišna materijala. Dio matičnog materijala istraživanog sedimenta je vulkanskog porijekla na što ukazuju pronađene čestice krhotina vulkanskog stakla i alteriranih vulkanskih čestica. Vjerojatno je eolski matični materijal bio dominantno smektitnog sastava zbog velike raširenosti smektitnih glina na kopnu tijekom apta i alba. Vjetrovi sjeveroistočnih smjerova prenosili su na Jadransku karbonatnu platformu detritični materijal sa sjevernih, odnosno sjeveroistočnih kopnenih područja izdignutih eoalpskom orogenezom. Istraživanja u ovom radu otkrila su poligenetsko porijeklo glinovitog sedimenta iz kamenoloma Tri jezerca. Iz vulkanoklastičnog i eolski sedimentiranog ishodišnog materijala pedogenetskim i dijagenetskim procesima nastale su glinovite naslage. Mineralni sastav istraživanog sedimenta u kojem prevladavaju illitični materijal i mješanoslojni illiti/smektiti, posljedica je transformacije smektita preko mješanoslojnih illita/smektita u illit. Do illitizacije je najvjerojatnije došlo tijekom pedogeneze, unutar tla koje je imalo obilježja vertisola. Pedogenetska alteracija istraživanog glinovitog sedimenta utvrđena je na temelju mikromorfoloških istraživanja i distribucije K, U, V, S, Cu, Zn, Mo i REE duž profila sedimenta. Mikromorfološkim istraživanjima detektirana je prisutnost ostataka korijenja, rupa i kanala ispunjenih framboidalnim piritom, pedoturbacija, ostataka fekalnih produkata bušaćih organizama, nodularnih pedooblika i mikroteksture tla. Brojni sekundarni minerali unutar istraživanog sedimenta formirani su nakon taloženja vulkanskog pepela/eolskog materijala procesima alteracije njegovih primarnih sastojaka, te precipitacijom iz pornih otopina tijekom dijageneze. Među njima su razne forme pirita koje su nastale u reduktivnim uvjetima, različite autigene forme SiO2, izometrični i vlaknasti zeoliti na površini i u šupljinama krhotina vulkanskog stakla, limonitne čestice i kristali magnetita nastali devitrifikacijom vulkanskih čestica, autigeni albiti, kloriti, kristali gipsa i jarosit koji je produkt trošenja istraživanog sedimenta.Abstract: The subject of this thesis was to define mineralogical, geochemical and micromorphological charateristics and the origin of the emersion clay sediment/paleosol placed between the second and the third large-scale sequence on the Istrian peninsula in the Tri jezerca quarry near Selina. Heavy and light mineral fraction of the analysed sediment indicate that the parent material originated from metamorphic and ophiolite complex, and also from volcanic ash. There are three possible sources of the non-carbonate parent material of the analysed sediment: insoluble residue of the limestone, volcanic ash and aeolian material. The insoluble residue of the limestone from the basement section of the analyzed sediment certainly participated in the formation as a source material, but its share is very small compared to the other two source materials. Part of the parent material of the analyzed sediments is of volcanic origin, because of the debris particles of volcanic glass and altered volcanic particles which were found in the sediments. The aeolian parent material was probably dominantly of smectite , because of the large widespread of the smectite clay on the surface during the Aptian and Albian period. The winds that blown from the northeast directions transported the detrital material from the northern or northeastern inland areas that were raised during the Eo-Alpine orogenesis to the Adriatic carbonate platform. This research revealed a polygenetic origin of the clay sediment from the Tri jezerca quarry. The clay deposit was formed through pedogenetic and diagenetic processes from volcanic clastic and aeolian sedimentary parent material. Mineral composition of the analyzed sediments are dominated bz illitic material and mixed-layer illite/smectite, that is the consequence of the transformation of smectite through the mixed-layer illite/smectite to illite. The illitization process most likely occurred during the pedogenesis within the soil that had features of vertisoil. The pedogenic alteration on the analyzed clay sediments was determined on the basis of micromorphological research and distribution of K, U, V, S, Cu, Zn, Mo and REE along the sediment profile. Micromorphological analysis detected the presence of roots remains, burrows and channels filled with pyrite framboids, nests of the fecal products of soil dwelling fauna, nodular pedofeatures and microfabric. Numerous secondary minerals within the analyzed sediment were formed after the deposition of volcanic ash/aeolian material through alteration processes of its primary ingredients, and precipitation from the pore solution during diagenesis. Among these minerals are various forms of pyrite that have formed in reduction conditions, different authigenic forms of SiO2, isometric and fibrous zeolite on the surface and in the cavities of volcanic glass shards, limonite particles and crystals of magnetite formed from devitrification of volcanic particles, authigenic albite, chlorite, gypsum crystals and jarosite that are the product of weathering of the analysed sediment