Foraminiferne združbe zgornjetriasnih (karnijskih) plasti v zahodni in osrednji Sloveniji

Rifl, Matic (author), Gale, Luka (mentor)

Foraminifere so enocelične praživali, ki so pogosto najdene v fosilnem zapisu sedimentnih kamnin. Triasne foraminiferne združbe predstavljajo okrevanje po masovnem izumrtju na meji perm-trias. Namen moje naloge je bil ugotoviti taksonomsko sestavo foraminifernih združb v karnijskih plasteh, ki so se odlagale pri različnih trofičnih razmerah oz. pri različnih sedimentacijskih pogojih. Vpliv trofičnih razmer na združbo je prikazan z razlikami v velikosti hišic vrste Aulotortus friedli. Prav tako sem sestavo karnijskih združb primerjal s sestavo norijsko-retijskih foraminifernih združb. Analiziral sem štiri profile karnijskih plasti: spodnjejulski periplimski Razorski apnenec, tankoplastnate kalkarenite v karbonatnem olistolitu v spodnjejulskih amfiklinskih plasteh blizu vasi Jesenica, julski Srednji apnenčasto-lapornati člen iz Lesnega Brda in julsko do spodnjetuvalsko Tor formacijo iz profila Stože. Snemanju profilov je sledila izdelava zbruskov, opis mikrofaciesov in določitev vrst foraminifer. Razlike v sestavi foraminiferne združbe sem utemeljil z uporabo različnih statističnih metod (Kruskal-Wallisov test, ANOVA, DCA, SIMPER in CVA). Foraminiferne združbe v preiskanih profilih vsebujejo taksone (Duostomina, Aulotortus, Lagenina, Endothyroidea, Duotaxis, Agathammina, Trochammina, Pillaminella, Semiinvoluta, Variostoma, Reophax, Lammeliconus, Planiivoluta, Hoyenella, Tolypammina, Miliolipora, Ammodiscus, Krikoumbilica, Gandinella). Preiskana zaporedja se razlikujejo v diverziteti združb, frekventnosti vrst in velikosti hišic vrste Aulotortus friedli. Razlike lahko pripišemo različnim trofičnim razmeram v morju. Razorski apnenec in kalkareniti na lokaciji Jesenica vsebujejo združbo visoke diverzitete. Pogoste so Duostominidae in Endothyroidea. Povprečna velikost vrste Aulotortus friedli je na lokaciji Razor 0, 56 mm, medtem ko so hišice te vrste na Jesenici večje, (0,67 mm), kar pa lahko pripišemo mehanskemu sortiranju. Združba lesnobrdskega apnenca in Tor formacije v profilu Stože ima nižjo diverziteto. V posamičnih plasteh je pogosta prevlada majhnega števila rodov (Hoyenella in Aulotortus). Manjša količina kisika, prisotnosti večje količine organske snovi bolj drobnozrnat sediment sta lahko tudi vzrok za manjšo povprečno velikost vrste Aulotortus friedli na teh dveh lokacijah (0,42 mm lokacija: Stože in 0,24 mm lokacija: Lesno Brdo).

• Language: Slovenian
• Keywords: triasne foraminiferne združbe, Tor formacija, amfiklinske plasti, Razorski apnenec, lesnobrdski apnenec, karnij, sedimentologija, paleoekologija, multivariatina statistika, morfometrija, Aulotortus friedli, Carnian pluvial event
• Work type: Bachelor thesis/paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2017
• PID: 20.500.12556/RUL-97486
• COBISS.SI-ID: 1369694
• Publication date in RUL: 26.10.2017

Secondary language

• Language: English
• Title: Late Triassic (Carnian) foraminiferal assemblages in west and central Slovenia

Abstract

Foraminifera are single-cell protists that are found within the fossil record of sedimentary rocks. Triasic foraminiferal assemblages represent a recovery after the Permian-Triassic extinction event. The aim of my thesis was to determine the taxonomic composition of foraminiferal assemblages found in Carnian beds deposited in different trophic or sedimentary settings. The differences in trophic levels demonstrated by variation in test size of Aulotortus friedli. Carnian foraminiferal assemblages were compared with the Norian-Rhaetian assemblages. Four localities were investigated: Lower Julian intertidal beds of Razor Limestone, thin bedded calcarenites within carbonate olistolith, in lower Julian amphiclina beds, near Jesenica, Julian Middle Limestone-Marl Member at Lesno Brdo, and Julian to Lower Tuvalian Tor Formation from Stože section. Field analysis was followed by the preparation of thin sections and determination of microfacies and foraminiferal assemblages. Differences in taxonomical compositions were evaluated using statistical methods (Kruskal-Wallis test, ANOVA, DCA, SIMPER and CVA). The assemblages are composed of following taxa: Duostomina, Aulotortus, Lagenina, Endothyroidea, Duotaxis, Agathammina, Trochammina, Pillaminella, Semiinvoluta, Variostoma, Reophax, Lammeliconus, Planiivoluta, Hoyenella, Tolypammina, Miliolipora, Ammodiscus, Krikoumbilica, Gandinella. Investigated sections demonstrate differences in diversity and abundance of taxa and also differences in test size of Aulotortus friedli. Differences can be attributed to different in trophic levels. The Razor Limestone and calcarenits from the Jesenica locality contain a more diverse assemblage with frequent Duostominidae in Endothyroidea. Average size of the tests of Aulotortus friedli species on Razor Mt. is 0,56 mm, whereas in Jesenica 0,66 mm. The latter could be attributed to sorting. The Middle Limestone-Marl Member of Lesno Brdo locality and the Tor Formation in the Stože section show lower diversity of foraminifera. Individual layers often show high abundance of few genera (Hoyenella and Aulotortus). Lower oxygen content, higher levels of organic matter and fine-grained sediment, found at both localities, could be the cause of smaller test sizes of Aulotortus friedli species (0,42 mm at Stože, and 0,24 mm at Lesno Brdo).

• Keywords: Triassic foraminiferal assemblages, Tor Formation, amficlina beds, Razor limestone, Lesno Brdo limestone, carnian, sedimentology, Carnian Pluvial Event, paleoecology, multivariate statistics, morfometrics, Aulotortus friedli