Facijesna i kemostratigrafska definicija granice perm-trijas na Velebitu

master's thesis

• Title: Facijesna i kemostratigrafska definicija granice perm-trijas na Velebitu : diplomski rad
• Title (english): Facies and chemostratigraphic definition of the P/T boundary of Mts. Velebit : master’s thesis
• Author: Ivan Jazvac
• Mentor: Dunja Aljinović (mentor)
• Committee member: Dunja Aljinović (predsjednik povjerenstva)
• Committee member: Uroš Barudžija (član povjerenstva)
• Committee member: Goran Durn (član povjerenstva)
• Granter: University of Zagreb; Faculty of Mining, Geology and Petroleum Engineering; (Department of Mineralogy, Petrology and Mineral Resources); Zagreb
• Defense date and country: 2017-12-15, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Geology; Mineralogy and Petrology

Abstract

Ovim radom prikazane su facijesne i kemostratigrafske karakteristike naslaga gornjega perma i donjega trijasa na području Brušana (planina Velebit). Istraživani slijed predstavlja kontinuiranu karbonatnu sedimentaciju na prijelazu iz paleozoika u mezozoik, a moguće ga je pratiti profilom Brušane Sy smještenom u zasjeku šumske ceste južno od Brušana. Na temelju mikropetrografskih karakteristika spomenutog profila utvrđeni su okoliši taloženja ovih, u potpunosti dolomitiziranih stijena. Određena je sedimentacija na karbonatnoj platformi, u relativno plitkome okolišu, a karakterizira je obilje mikritnih taloga, prisustvo mikrobijalnih (cijanobakterijskih) proslojaka, povremeno sačuvano obilje mikrofosila te taloženje u subtajdalnoj, tajdalnoj i supratajdalnoj zoni. Gornjopermska starost naslaga potvrđena je foraminiferama, a osim njih slijed je bogat fosilnim ostacima vapnenačkih zelenih algi i njihovih spora, gastropoda te ostrakoda. Utvrđeno je izronjavanje primarnih taloga u zonu intertajdala/supratajdala usred povremenih oscilacija morske razine, što je ujedno rezultiralo i pretaloživanjem djelomično litificiranog sedimenta iz ovih zona u zonu subtajdala. Posljedica izronjavanja karbonatnih taloga je i intenzivna dijageneza u vadoznoj zoni. Rezultati izotopne analize ugljika i kisika uspoređeni su s vrijednostima karakterističnim za ovo razdoblje. Izostanak negativnog otklona u sastavu ugljikovih izotopa na P/T granici objašnjen je kao utjecaj vadozne dijageneze na primarni izotopni signal pri čemu ni promjene uzrokovane procesom dolomitizacije nisu isključene.

Abstract (english)

Facies and chemostratigraphic characteristic of the transitional Permian and Triassic interval were differentiated by investigating dolomites near the village Brušane (Velebit Mts.) along the road-cut south from Brušane village. Investigated section “Brušane Sy” represents a continuous deposition of carbonates at the P/T boundary interval. All deposits in the vertical column are determined as dolostones. Related to their main micropetrographic features a deposition in a shallow part of carbonate platform was discerned – in subtidal, intertidal and supratidal zones. The sedimentation is characterized by the prevalence of micritic component, the presence of microbial (cyanobacterial) interlayers and fairly preserved fossils: foraminifers, green algae and their spores, gastropods and ostracods. The Upper Permian age of the lower part of the section “Brušane Sy” is confirmed by Permian foraminifers genera. Occasional emerging of the subtidal/intertidal deposits to supratidal condition occurred that has resulted partially with the desiccation and local resedimentation of desiccated lime-mud fragments to subtidal zone. A significant process related to the deposition in the supratidal zone was vadose diagenesis observed in many Permian dolostones. The periodic emergence of the platform was interpreted due to sea-level oscillation. The values of the δ13C, δ18O isotope content resulted in the isotope curve that was compared to the P/TB isotope curve from several world known P/TB localities. A composite isotope curve from Brušane (“Brušane Sy” and “Brušane 2” sections) is missing the extreme negative values pointing to an exact position of P/TB. This can be interpreted as a consequence of the vadose diagenesis observed along almost entire “Brušane Sy” section.

• Keywords: Brušane; granica perm-trijas; mikropetrografska analiza; analiza stabilnih izotopa
• Keywords (english): Brušane; Permo-Triassic boundary; micropetrographic analysis; stable isotope analysis
• Language: croatian
• URN:NBN: urn:nbn:hr:169:777245
• Study programme: Title: Geology; specializations in: Geology of mineral resources and geophysical explorations; Course: Geology of mineral resources and geophysical explorations; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra geologije (magistar/magistra geologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2018-04-12 09:39:56