Sedimentološka analiza siliciklastičnih plasti v Mesečevem zalivu : diplomsko delo

Moškon, Mateja (avtor), Rožič, Boštjan (mentor)

Srednje eocensko flišno zaporedje na območju Strunjanskega klifa sestavljajo predvsem siliciklastične kamnine v obliki turbiditnih peščenjakov in laporjev, podrejeno se pojavljajo tudi kalciturbiditne plasti. Osnovni namen diplomskega dela je bila sedimentološka analiza siliciklastičnih plasti v 216 metrov debelemu zaporedju, ki smo ga posneli med rtom Ronek in Sv. Križem. Turbiditne plasti so povečini zelo tankoplastnate in zajemajo le vrhnje dele boumove sekvence. Razlike v strukturi, barvi in velikosti zrn so s prostim očesom slabo vidne. V zaporedju je prisotna tudi bioturbacija. Odlitki na spodnji strani plasti nakazujejo smer paleotransporta iz ZSZ – VJV, kar sovpada s predhodno ugotovljeno dominantno smerjo transporta vzdolž osi flišnega bazena. Na plastnicah peščenjakovih plasti se pogosto pojavljajo poogleneli rastlinski ostanki. V diplomskem delu sem analizirala 23 zbruskov, ki sem jih pod mikroskopom ločila v pet skupin, glede na sestavo in velikost zrn. V prvi skupini so laporovci, v drugi drobnozrnati meljasti litični kremenovi peščenjaki in v tretji srednjezrnati litični kremenovi peščenjaki. Za slednjo, ki je med zbruski tudi najštevilčnejša, so značilni peščenjaki s polzrelo strukturo, z veliko zrni kremena in litičnimi zrni bioklastičnega apnenca in roženca. Drobnozrnate meljaste peščenjake sem dalje delila v dve podskupini, glede na limonitizacijo vzorca. Vzorce, ki so odstopali od povprečja, sem dodatno natančneje opisala. Izpostavila sem dva vzorca - vzorec ST17 (199 meter višine profila) zaradi nekoliko manjših in bolj zaobljenih zrn ter vzorec st4 (28 meter višine profila) zaradi večje vsebnosti fosilov. Sestava siliciklastičnih turbiditov razkriva, da je bilo njihovo izvorno območje mešan siliciklastično-karbonaten šelf. Inhofosili dokazujejo potek sedimentacije na dobro prezračeni distalni bazenski ravnici. Prisotnost pooglenelih rastlinskih ostankov priča o tem, da so v morje pritekale tudi takratne reke in nosile material iz zamočvirskih deltnih območij.

• Jezik: Slovenski jezik
• Ključne besede: fliš, siliciklastiti, Strunjanski klif, turbiditi, Boumova sekvenca
• Vrsta gradiva: Diplomsko delo/naloga
• Tipologija: 2.11 - Diplomsko delo
• Organizacija: NTF - Naravoslovnotehniška fakulteta
• Kraj izida: Ljubljana
• Založnik: [M. Moškon]
• Leto izida: 2021
• Št. strani: X, 32 f.
• PID: 20.500.12556/RUL-131171
• UDK: 55
• COBISS.SI-ID: 86608387
• Datum objave v RUL: 23.09.2021

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Sedimentological analysis of siliciclastic layers in the Mesečev zaliv : diploma work

Izvleček

Middle Eocene flysch sequence in the area of the Strunjan Cliff consists mainly of siliciclastic rocks in the form of turbidite sandstones and marls, calciturbidite layers appear subordinately. The purpose of the diploma thesis was the sedimentological analysis of siliciclastic layers in 216 meters thick sequence, which was recorded between the cape Ronek and the bay of Sveti Križ. Turbidite layers are mostly very thin and cover only the top parts of the Bouma sequence. Differences in the structure, color and size of the grains are poorly visible to the naked eye. In the succession, the bioturbation is also present. Current ripples on the underside of the beds indicate the ZSZ - VJV direction of paleotransport that confirmes the previously reported direction of transport along the axis of the flysch basin. On the bedding planes of the sandstone beds, carbonized plant remains often appear. In my thesis, I analyzed 23 thin-sections under the microscope. I divided them into five groups, based on the composition and size of the grains. In the first group, I’ve included marl, in the second group, the fine-grained silty lithic quartz sandstone and in the third, the medium grained lithic quartz sandstone. The latter is most common in thin-sections and is characterized by sandstone with a semi-mature structure, with large grains of quartz and lithic grains of bioclastic limestone and chert. I further divided fine-grained silty sandstone into two subgroups, depending on the limonitization of the sample. Samples differing from the average were described in more detail. I highlighted two outstanding samples - the ST17 (199 meter of the section) sample due to slightly smaller and more rounded grains and the st4 (28 meter of section) sample due to the high content of fossils. The composition of siliciclastic turbidites reveals that their source area was mixed siliciclastic-carbonate shelf. Inhofossils demonstrate the sedimentation on a well-oxigenated distal basin plain. The presence of carbonatized plant remains testifies to the fact that the rivers flowed into the sea and carried material from the marsh delta environments.

• Ključne besede: Flysch, siliciclastites, Strunjan cliff, turbidites, Bouma sequence