O nastanku hidrografske mreže in o nekaterih kraških pojavih na Idrijskem

Ivan Mlakar

DOI: https://doi.org/10.3986/ac.v31i2.387

Abstract

Rekonstruirali smo geološke razmere na nivoju najmlajšega - pliocenskega ravnika v današnji višini 1000 metrov. Pokazali smo, da so takratne litološke in tektonske okoliščine imele pri nastajanju hidrografske mreže odločilno vlogo, kar velja tudi za pretočitve Kanomljice, Nikove, Idrijce in Belce. Območje južno in NW od Idrije izpolnjuje vse pogoje, da postane klasično ozemlje za preučevanje začetnega stadija zakrasevanja, zato smo namenili tej problematiki posebno pozornost. Pri nastajanju kraških objektov je igral pomembno vlogo zlasti sistem prečnoalpskih prelomov in razpok. S teorijo brezen smo med drugim obrazložili nastanek Divjega jezera in pokazali, da so bile vsaj nekatere vrtače zasnovane že v obdobju, ko so kredne apnence še prekrivale slabše vodoprepustne kamenine. Antiklinalne strukture so se izkazale kot najboljši indikator za prisotnost podzemnih kraških prostorov. Na koncu prispevka smo tabelarno predstavili še rezultate 60 kompletnih silikatnih analiz skoraj vseh kamenin na Idrijskem.

 

Geological structure on the Pliocene paleosurface level in the nowadays 1000 m altitude were reconstructed. The lithological and tectonical circumstances in that time played a decisive role in hydrographic net origin and also on Kanomljica, Nikova, Idrijca and Belca rivers piracy. Landscape south and NW from Idrija fulfil all conditions to become classical region for initial karstification stadium examination, for that reason to this problems great attention have been paid. Particularly system of cross alpine faults and fissures played significant role on karst phenomena origin. With potholes theory the origin of Wild Lake have been explained and pointed out, that some dolinas at least have been projected already in period when Cretaceous limestones were covered by worse waterpermeable rocks. Anticline structures proved as the best indicator for karst rooms presence. On article end the results of 60 complete silicate analyses of nearly all Idrija's rocks in table shape are presented.

 

 

 

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DOI: https://doi.org/10.3986/ac.v31i2.387

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