TRIJASKI MORSKI GMAZ IZ OKOLICE KRAŠIĆA (ŽUMBERAK)

master's thesis

• Title (english): TRIASSIC MARINE REPTILE FROM THE KRAŠIĆ AREA (ŽUMBERAK MT.)
• Author: Fran Vidaković
• Mentor: Aleksandar Mezga (mentor)
• Committee member: Aleksandar Mezga (predsjednik povjerenstva)
• Committee member: Đurđica Pezelj (član povjerenstva)
• Committee member: Marijan Kovačić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Geology); Zagreb
• Defense date and country: 2024-02-23, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Geology

Abstract

Na ljeto 2021. godine, u mjestu Vlašić Brdo na Žumberačkoj gori, nedaleko od Krašića, otkriven je sekundarni blok vapnenca s očuvanim kostima trijaskog morskog gmaza. Preparacija kostiju omogućila je detaljan opis i taksonomsku odredbu ostataka. Riječ je o djelomično artikuliranom dijelu posteriornog trupnog i/ili najviše anteriornog repnog dijela kralježnice, rebara i gastralija, te neodredivoj kosti uda ili zdjelice ihtiosaura iz porodice Cymbospondylidae. Bogata konodontna fauna izolirana iz vapnenca ukazuje da je uzorak srednje trijaske starosti, iz prijelaznog intervala anizika u ladinik, usporedivog s rasponom između gornje Reitzii i Curionii amonitne zone. Uz konodonte, mehaničkom je i kemijskom preparacijom samog uzorka, kemijskom ekstrakcijom mikrofosila te analizom mikropreparata utvrđena bogata fosilna zajednica koja uključuje ostatke foraminifera, radiolarija, mogućih srodnika dinoflagelata, spužva i/ili mahovnjaka, ostrakoda, brahiopoda, juvenilnih puževa, školjkaša, glavonožaca, bodljikaša te riba koštunjača i hrskavičnjača. Na temelju fosilnih ostataka rekonstruirana je hipotetska hranidbena mreža ove tafocenoze. Vapnenački mikrofacijes može se opisati kao kristalo-bioklastični pekston koji pokazuje tipične značajke dubljevodnih facijesa očekivanih u tektonski stvorenom intra-platformskom bazenu, ali i naznake veoma značajanog siliciklastičnog i/ili vulkanoklastičnog donosa.

Abstract (english)

In the summer of 2021, a block of limestone preserving bones of a Triassic marine reptile was discovered at the Vlašić Brdo locality on the Žumberak Mt., not far from Krašić. Preparation of the bones allowed a detailed description and taxonomic determination of the remains. It consists of a partially articulated portion of the anterior trunk and/or posterior-most tail region of the spine, ribs and gastralia, and an unidentifiable limb or pelvic bone of an ichthyosaur from the family Cymbospondylidae. A rich conodont fauna extracted from the limestone indicates that the sample is of the Middle Triassic age, specifically from the Anisian – Ladinian boundary interval, which can be correlated with a span between Reitzii and Curionii ammonoid zones. In addition to conodonts, mechanical and chemical preparation, chemical extraction, and analysis of thin sections revealed a rich fossil community which includes remains of foraminifera, radiolarians, possible relatives of dinoflagellates, sponges and/or bryozoans, ostracods, brachiopods, juvenile snails, bivalves, cephalopods, echinoderms, and bony and cartilaginous fishes. On the basis of all these fossil remains, a hypothetical food web of this taphocenosis was reconstructed. Microfacies of the limestone can be described as a crystalo-bioclastic packstone which shows the characteristics typical of deeper-water facies expected in a tectonically induced intra-platform basin, but also exhibits evidence of very significant siliciclastic and/or volcanoclastic influx.

• Keywords: Ichthyosauria; Cymbospondylidae; Conodonta; trijas; anizik; ladinik
• Keywords (english): Ichthyosauria; Cymbospondylidae; Conodonta; Triassic; Anisian; Ladinian
• Language: croatian
• URN:NBN: urn:nbn:hr:217:276515
• Study programme: Title: Geology; Study programme type: university; Study level: graduate; Academic / professional title: sveučilišni magistar/magistra geologije (sveučilišni magistar/magistra geologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Embargoed access; Embargo expiration date: 2026-02-23
• Created on: 2025-01-30 14:36:38