Holocenski sedimentacijski procesi na aluvialnih pahljačah v dolini Planice

Novak, Andrej (author), Šmuc, Andrej (mentor), Levanič, Tom (co-mentor)

Aluvialne pahljače so dinamično sedimentacijsko okolje, v katerem se prepletajo tako gravitacijski kot aluvialni sedimentacijski procesi, ki za seboj pustijo značilne sedimentne faciese. Preplet gravitacijskih in aluvialnih sedimentnih faciesov je še posebej značilen za pahljače v gorskem okolju. Primer doline, ki so jo v holocenu začeli zasipavati sedimenti na številnih aluvialnih pahljač, je dolina Planice v severozahodni Sloveniji. Doktorska disertacija je namenjena detajlni sedimentološki analizi holocenskih sedimentacijskih procesov na aluvialnih pahljačah v gorskem okolju, njihovemu časovnem in prostorskem pojavljanju ter dejavnikom, ki vplivajo na njihovo sprožitev. Facielna analiza vključuje opis sedimentnih struktur, tekstur ter litologije zrn. Opravili smo jo na sedimentih odloženih na površju pahljač ter v detajlnih sedimentoloških profilih. Starost sedimentnih nanosov smo določili z dendrogeomorfološko metodo ter radiokarbonskimi datacijami. Datiranim nanosom smo pripisali sprožitvene meteorološke dogodke, ki jih je zabeležila meteorološka postaja Rateče. Pri določevanje sedimentnih faciesov in morfoloških značilnosti pahljač smo uporabili tudi metode daljinskega zaznavanja (lidarske posnetke ter brezpilotni letalnik). Z georadarjem smo opravili podpovršinske raziskave. Skupno smo določili osem sedimentnih faciesov. Šest jih je značilnih za aluvialna sedimentacijska okolja in se pojavljajo predvsem tam, kjer preperevanje kamninske podlage ne tvori drobnozrnatih (muljastih) sedimentov. Le dva faciesa sta značilna za gravitacijske (drobirske in blatne) masne tokove, ki se pojavljajo le na lokacijah, kjer pri preperevanju kamninske podlage nastaja večja količina muljastega sedimenta. Sedimentološki podatki, datacije, povezava sedimentnih procesov s sprožitvenimi dogodki, podatki daljinskega zaznavanja in podpovršinske raziskave dokazujejo, da aluvialne pahljače gradijo predvsem aluvialni sedimentacijski procesi, ki jih prožijo pogosta 24-urna deževja z več kot 50 mm padavin. Sedimentacijski procesi gravitacijskih tokov so redkejši, vendar destruktivnejši in so pogojeni z zaledno litologijo.

• Language: Slovenian
• Keywords: aluvialne pahljače, sedimentacijski procesi, dendrogeomorfologija, padavinski dogodki, lidar, brezpilotni letalnik, DMV, holocen, Planica
• Work type: Doctoral dissertation
• Organization: FGG - Faculty of Civil and Geodetic Engineering; NTF - Faculty of Natural Sciences and Engineering
• Year: 2023
• PID: 20.500.12556/RUL-146720
• COBISS.SI-ID: 151877891
• Publication date in RUL: 09.06.2023

Secondary language

• Language: English
• Title: Holocene sedimentation processes on alluvial fans in the Planica Valley

Abstract

Alluvial fans are a dynamic sedimentary environment where a set of sedimentary facies typical of alluvial and gravity sedimentary process occur. Such interlinked occurrence of sedimentary processes is typical for alluvial fans in the alpine environment. An example of an alpine valley is the Planica Valley in northwest Slovenia, which is covered by numerous Holocene alluvial fans. Multimethod research of this dissertation is focused on detailed sedimentary analysis of Holocene sedimentary deposits which built a set of typical alpine alluvial fans, spatio-temporal presence of these process and factors which contribute to their occurrence. Sedimentary analysis of facies is based on structure, texture, and lithology of sediment documented on fan’s surfaces and in sedimentary profiles. Sedimentary deposits were dated using dendrogeomorphology and radiocarbon dating. Dated deposits were related to triggering rainfall events monitored at the Rateče meteorological station. Processes and alluvial fan landforms were also defined using remote sensing techniques (lidar and unmanned aerial vehicle). Ground-penetrating radar technique was applied to understand subsurface geometry. We classified eight sedimentary facies, mostly typical for alluvial sedimentary environments. They occur where the bedrock does not weather into fine-grained (mud) sediment. Only two facies are typical for gravitational (debris and mud) flow, which occur at places with bedrock that weathers into large amounts of fine-grained sediment. Sedimentary analysis, dating of deposits, relating dated deposits to triggering rainfall events, remote sensing and subsurface data prove that alluvial fans are predominantly built by alluvial sedimentary processes during frequent 24-hour rainfalls that exceed 50 mm. Gravitational mass movement sedimentary process are much less frequent, however much more destructive and conditioned by bedrock lithology.

• Keywords: alluvial fans, sedimentary processes, dendrogeomorphology, rainfall events, lidar, unmanned aerial vehicle, DEM, Holocene, Planica