Uporaba metode datiranja povrsinske izpostavljenosti na primeru podora Veliki vrh

O podoru v Velikem vrhu (Košuta, Karavanke) ni zanesljivih zgodovinskih zapisov, vendar pa le ti obstajajo o podoru na Dobraču (25.1.1348), ki je od Velikega vrha oddaljen 46 km. Podor je povzročil potres in naša hipoteza je bila, da je tudi podor v Velikem vrhu posledica istega dogodka. Tako smo s pomočjo metode datiranja površinske izpostavljenosti analizirali vzorce matične kamnine v steni Velikega vrha ter vzorce s površine podornih blokov. Ugotavljali smo vsebnost ³⁶Cl, ki se je začel tvoriti po podoru. Na podlagi poznavanja števila atomov ³⁶Cl na gram Ca na leto izpostavljenosti, čas dogodka (podor) izračunamo iz koncentracij ³⁶Cl izmerjenih s pomočjo pospeševalnika (AMS). Prvi rezultati kažejo, da sta se podora na Dobraču in Velikem vrhu posledica potresa v Furlaniji Julijski krajini. Starost podora v Velikem vrhu je (740 +- 71) a. Za bolj zanesljive rezultate bo potrebno izboljšati sam model in upoštevati več dejavnikov - predvsem nadmorsko višino in klimatske razmere.

There are no reliable historical data about the Veliki vrh rockfall (Košuta, Karavanke Mountains) but the records exist about the Dobrach rockfall (25^th of January 1348) 46 km to the West of Veliki vrh. The rockfall was triggered by the earthquake and our hypothesis was that Veliki vrh rockfall was induced by the same event. Therefore we used the surface exposure dating method to analyze the bedrock samples in the Veliki vrh rock face as well as the samples of the boulder surface. The content of ³⁶Cl, that started to produce after the earthquake, was measured. On the basis of the known number of ³⁶Cl per gram Ca per year of exposure, the time of the rockfall can be calculated from the concentration of ³⁶Cl measured by accelerator mass spectrometry (AMS). Preliminary results show the correlation of the two rockfalls (Dobrach and Veliki vrh) as the consequence of the earthquake in Friuli Venezia Julia. The age of Veliki vrh rockfall is (740 +- 71) a. For more reliable results further research should be conducted using also the data on altitude and climate.