Litiotidni školjkaši u donjojurskim karbonatnim naslagama južnog Velebita i južne Like

master's thesis

• Title (english): Lithiotis-type bivalves in Lower Jurassic carbonates of Southern Velebit Mt. and Southern Lika
• Author: Silvija Brcko
• Mentor: Maja Martinuš (mentor)
• Committee member: Maja Martinuš (predsjednik povjerenstva)
• Committee member: Jasenka Sremac (član povjerenstva)
• Committee member: Dražen Kurtanjek (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Geology); Zagreb
• Defense date and country: 2020-09-29, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Geology; Geology and Paleontology

Abstract

U donjojurskim karbonatnim naslagama na prostorima Malog Alana i Štikade pronađene su dvije vrste litiotidnih školjkaša: Cochlearites loppianus i Lithioperna scutata. Radom na terenu određene su vrste litiotidnih školjkaša, mjerene dimenzije i orijentacije ljuštura te struktura i teksture slojeva. Na području Malog Alana snimljen je i litostratigrafski stup. Uzorci koji su bili prikupljeni ranijim istraživanjima korišteni su za sedimentološke analize. Analizom mikroskopskih preparata određeni su okoliši u kojima su litiotidni školjkaši živjeli. Slijed Mali Alan debljine 207 m u potpunosti obuhvaća prvu i zadnju pojavu litiotidnih školjkaša, dok slijed Štikada debljine 45 m samo njihov najmlađi dio, tj. dobro se korelira s posljednjom jedinicom Malog Alana. Prva se pojavljuje vrsta L. scutata u mlađem sinemuriju koja je preferirala lagunske potplimne okoliše, dok se vrsta C. lopianus pojavljuje u starijem plinzbahu. U ovim naslagama moguće je pratiti kako su se dimenzije litiotida mijenjale od svega nekoliko centimetara, pa preko 20 cm i onda ponovno dolazi do smanjivanja ljuštura, tijekom starijeg toarcija. Nakon starijeg toarcija litiotidni školjkaši izumiru.

Abstract (english)

Two species of Lithiotis-type bivalves were found in the Lower Jurassic carbonate deposits in the areas of Mali Alan and Štikada: Cochlearites loppianus and Lithioperna scutata. Lythiotis-type bivalve species, dimensions and orientations of their shells were determined in the field, as well as limestone texture and bed structures. A lithostratigraphic column was also recorded in the area of Mali Alan. Samples collected from previous studies were used for sedimentological analyses. Environments in which Lithiotis-type bivalves lived were determined from microscopic thin sections. The Mali Alan succession is 207 m thick and encompasses first and last occurrence of the Lithiotis-type bivalves, while the Štikada succession is 45 m thick and includes their youngest part, i.e. it correlates well with the last unit of the Mali Alan. The first to appear is L. scutata in the Late Sinemurian, which preferred lagoonal subtidal environments, while C. loppianus first appears in the Early Pliensbachian. In these deposits, it is possible to observe how the dimensions of the Lithiotis-type bivalves changed from only a few centimetres to over 20 cm, and during the Early Toarcian the decrease of shell dimensions is observed. After Early Toarcian, the Lithiotis-type bivalves become extinct.

• Keywords: litiotidni školjkaši; Lithioperna scutata; Cochlearites loppianus; donjojurske naslage; Južni Velebit; južna Lika
• Keywords (english): Lithiotis-type bivalves; Lithioperna scutata; Cochlearites loppianus; Lower Jurassic carbonates; Southern Velebit Mt.; Southern Lika
• Language: croatian
• URN:NBN: urn:nbn:hr:217:954446
• Study programme: Title: Graduate university study of Geology; 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: 2021-02-10 09:35:54