Sedimentologija in stratigrafija anizijskih bazenskih razvojev pri planini Obranca na Mežakli : magistrsko delo

Škrap, Petra (avtor), Rožič, Boštjan (mentor), Celarc, Bogomir (komentor)

Mežakla je planota v Julijskih Alpah, ki sega do 1348 metrov nadmorske višine. Razteza se med rekama Radovno na jugu ter Savo Dolinko na severu, na vzhodu pa sega do Blejskega kota in Blejskega Vintgarja. Natančno kartiranje tega območja je pokazalo, da severovzhodni del Mežakle strukturno pripada Krnskemu pokrovu, ki je strukturno najnižji pokrov Julijskih pokrovov v vzhodnih Južnih Alpah. Jugovzhodni del planote kaže razvoje značilne za Pokljuški pokrov. V magistrski nalogi so preučene in opisane srednjetriasne plasti anizijske, natančneje pelsonske starosti pod planino Obranca. Posnela sem sedimentološki profil dolžine 195 m, na katerem sem opravila biostratigrafsko in detajlno mikrofacielno analizo. Podana je interpretacija sedimentarnega razvoja anizijskih plasti severovzhodnega dela planote. Sedimentološki profil in rezultati analiz so pokazali, da je razvoj severovzhodnega dela planote primerljiv s stratigrafskim razvojem v Kamniško-Savinjskih Alpah. Nad anizijskim dolomitom, se razvoji lateralno močno spreminjajo. Na najbolj severovzhodnem delu planote najdemo debeloplastnate apnence. Nasprotno v osrednjem delu planote nad Anizijskim dolomitom ležijo plasti tankoplastnatega črnega bituminoznega laminiranega apnenca, ki so primerljive s Strelovško formacijo in/ali členom Velike planine iz Kamniško-Savinjskih Alp. Sinsedimentne gube, majhni prelomi, zdrsne gube - slumpi in majhni turbiditi dokazujejo sedimentacijo na nagnjenem pobočju in/ali povečano tektonsko aktivnost, ki sproži gibanje sedimenta. Tankoplastnat apnenec navzgor prehaja v plastnate apnence, dolomite in dolomitizirane apnence, ponekod v obliki manjših klinoform. Takšno zaporedje tankoplastnatih bituminoznih apnencev, ki navzgor prehajajo v plastnate apnenece, dolomite in dolomitizirane apnenece plitvomorskega razvoja, se znotraj profila ponovi trikrat. Pelsonska starost posnetega zaporedja je določena na podlagi preseka razponov foraminifer Pilammina densa, Aulotortus? eotriasicus, Trochammina jaunensis in Citaella dinarica. Sedimentološki profil odraža večkratno plitvenje znotraj restriktivnega intraplatformnega bazena, kar je pogojeno s sinsedimentno tektoniko. Postopen prehod v masiven dolomit in apnenec na celotnem zgornjem delu planote in lateralno izklinjanje bazenskih razvojev kažejo na progradacijo platforme in popono zasipanje manjšega bazena v pelsonu in zgornjem aniziju.

• Jezik: Slovenski jezik
• Ključne besede: Julijske Alpe, vzhodne Južne Alpe, Krnski pokrov, anizij, bazenski razvoj, Strelovška formacija
• Vrsta gradiva: Magistrsko delo/naloga
• Tipologija: 2.09 - Magistrsko delo
• Organizacija: NTF - Naravoslovnotehniška fakulteta
• Kraj izida: Ljubljana
• Založnik: [P. Škrap]
• Leto izida: 2023
• Št. strani: XV, 64 str.
• PID: 20.500.12556/RUL-143935
• UDK: 55
• COBISS.SI-ID: 138723075
• Datum objave v RUL: 20.01.2023

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Sedimentology and stratigraphy of Anisian deep-watter deposits near Obranca on Mežakla plateau : master's thesis

Izvleček

The Mežakla plateau in the Julian Alps reaches 1348 meters above sea level. It is located between the rivers Radovna to south and west, and Sava Dolinka to the north. Its eastern border extends to Blejski kot and the Vintgar Gorge. Detailed mapping showed that the northeastern part of Mežakla structurally belongs to the Krn Nappe, which is the lowest of the Julian nappes in the eastern Southern Alpes. On the other hand, the southwestern part of the plateau shows stratigraphic evolution distinctive for the Pokljuka nappe. In this master´s thesis, Pelsonian succession from section near Obranca is studied and presented. A 195 m long sedimentological section was logged and sampled for thin sections. The latter were used for detailed microfacial and biostratigraphic analysis. The interpretation of sedimentary evolution is given. Our results show that the Anisian succession in the northeastern part of the Mežakla plateau closely resambles the stratigraphic succession from the Kamnik-Savinja Alps. The base of the succession on the Mežakla plateau is represented by Anisian dolomite. On the northeastern-most part of the plateau, the Anisian dolomite is followed by thick-bedded limestones, whereas in the central part of the plateau the Anisian dolomite is followed by thin-bedded laminated black bituminous limestone, equivalent tot he Strelovec Formation and/or the Velika planina Member. Sinsedimentary folds, slumps and small-scale faults and turbidites are evidence of sedimentation on the slope and/or higher tectonic activity. Upwards, the thin-bedded laminated black bituminous limestone gradually passes into bedded limestone, dolomite and dolomitized limestone. The alternation of thin-bedded black bituminous limestone and bedded limestone, dolomite and dolomitized limestone is observed three times in the entire succession. The Pelsonian age of the succession was determined based on the cross-section of the ranges of Pilammina densa, Aulotortus? eotriasicus, Trochammina jaunensis and Citaella dinarica foraminifera species. The succesion shows repeated shallowing of restrictive intraplatform basin, which is conditioned by synsedimentary tectonics. Throughout the Mežakla plateau, the platform progradation can be observed with lateral and upwards transition into massive dolomite and limestone, which shows the final filling of the basin during Pelsonian and upper Anisian age.

• Ključne besede: Julian Alps, Eastern Southern Alps, Krn nappe, Anisian, deep-water succession, Strelovec formation