Karst and Caves in Salt Diapirs, SE Zagros Mts. (Iran)

Abstract

Na podrocju Perzijskega zaliva je znanih okoli 200 solnih diapirjev, med njimi mnogo aktivnih. Kraske kamnine predstavljajo najvec kamena sol in redkeje sadra ter anhidrid. Kraske oblike, popolnoma primerljive z oblikami v “klasicnih” karbonatnih kamninah, so najbolje razvite v ostankih uravnanih povrsij. Tako so skraplje, “solution pipes”, vrtace, udorne vrtace, depresije podobne uvalam in poljem, slepe doline, soteske, ponori, izviri in jame. Tod sta bili odkriti in raziskani dve izmed najdaljsih jam v soli na svetu. Daljse jame so nastale predvsem v piezometricni gladini, vecje pa v diapirjih ob morski obali. Jame pogosto predstavljajo odtok iz depresij, podobnih poljem. V dnu udornih vrtac in v ponorih so tudi strme, skoraj navpicne jame. Kraski procesi so omejeni predvsem na sol, redkeje na sadro. Predvsem gre za raztapljanje in odnasanje soli izpod neprepustnega pokrova (gypcrete). V nekaterih diapirjih je dokazano globoko kroženje padavinske vode. About 200 salt diapirs (plugs) have been known in the region of the Persian Gulf. numerous are still active. Karst rocks are represented by a rock salt, less frequently by gypsum and anhydrite. Karst developed especially in relics of planated surfaces. Karst forms are completely comparable with karsts in classical carbonate rocks. Different forms can be distinguished: karren, solution pipes, solution dolines, solution-collapse dolines, uvalalike to polje-like depressions, blind valleys, canyon-like forms, ponors, springs and caves. Two World longest caves in salt were discovered and explored here. Long caves are developed especially in a watertable, large ones in plugs near the seacoast. Caves are often outlets of closed depressions (polje-like). Some caves at bottoms of collapse-solution dolines or swallow holes are subvertical. Karst processes are caused dominantly by dissolution of salt, less frequently of gypsum. The process of subrosion of halite under gypcretes plays the main role. Deep circulation of meteoric waters was proved in some plugs.