An Introduction to Hypogene Karst Regions and Caves of Iran

Abstract Iran is divided into five major geologic zones—the Zagros, Sanandaj-Sirjan, Central Iran, the East and Southeast, and the Alborz. About 10.5% of the country is underlain by carbonate rock formations, chiefly in a broad western strip, in the northeast, and central parts. Geomorphologic investigations have found clear differences between the extent and intensity of karst surface landform development, karst being more abundant in wetter regions such as the Zagros and very limited in arid Central Iran. Iran is within a very active tectonic region, with some sporadically active volcanoes, strong and widespread seismic activity, numerous active faults, and thermal springs. The hypogene caves that have been studied to date are found chiefly in just three areas: the North West and the Central and Eastern zone where they are associated with the igneous activity, and the Zagros Mountains. Although there is no modern volcanic or other igneous activity in the Zagros, the occurrence of oil fluids is considered to be a potential cause for hypogene cave development. The development of the two largest karst caves in Iran, Katalekhor and Alisadr, is attributed to ascending CO2 due to volcanic activity. Other large caves such Karaftoo and Kangohar were created by magmatic fluids. Excavations for dams and water transmission tunnels in the non-volcanic Zagros zone have discovered some remarkable, active hypogene systems. Oil brines are considered to be the most important contributor to their development.