In the Kohgiluyeh and Boyer Ahmad province in the southwest of Iran, along the road of Dehdasht to Sarfariab city, when pass through the pirzal gorge, we enter to the plain between the two mountains “Siah” and “Mondon”. The two mountains, Siah and Mondon, are anticlines that extend along the northwest to the south-east. In the plain between the two anticlines, there is a beautiful perched syncline.
Syncline is a geologic feature like a “V” fold in layered sedimentary ground, which often occurs when the layers tend to go horizontally, but twisted by the tectonic forces. In analogy, an “anticline” is the convex opposite form, where the sedimentary layers form a dome, and a “monocline” is flat.
A “perched syncline”, or “perched synclinal”, differenciates itself by the fact it stands elevated from the surrounding terrain. Contrary to the monoclines, they form very characteristic mountains, looking like fortresses surrounded by walls.
In fact, a perched syncline is formed when the central layers of syncline (younger) have more resistance than the outer layers (older) against erosion. In this case, the outer stones are eroded and the strong rocks remains in the center. These strong rocks remain in the form of a ship stands elevated from the surrounding terrain and form a perched syncline.
In center of Pirzal perched syncline, thick to medium bedded limestone (Asmari formation – Oligomiocene in age) and on the sides, alternation of Marl and thin bedded limestone (Pabdeh formation – Eocene to Oligocene) have been outcropped. Over the time, marls have been eroded, and strong limestones remain in the center.
This beautiful photo was taken by M.S.Zangeneh looking northward.
Keywords: Iran , Kohgiluyeh , Zagros , Anticline , Syncline , Perched syncline , dehdasht , sarfaryab , geology , geotourism , asmari formation , pabdeh formation , mondon anticline , kuh e siah anticline , pirzal gorge , zamingasht