Geometrical analysis of folding in Kalut area (NE of Ardakan)

Abstract

The Kalut basin (NE of Ardakan) was formed as an intermountain depression just after Upper Cretaceous orogeny event and was severely folded in the Pliocene. The plunge of the fold axes are less than 30 degree frequently. From the viewpoint of interlimb angle, the important features of the folded Kalut basin are the open synclines and the closed diapiric anticlines with salty core. In the central parts of the basin the salt bodies have intruded along the b-axis anticlines as piercement domes. In the western and eastern zones of the basin, the interlimb angle of anticlines is "open" and in the eastern - and westernmost of the basin, the continuity of diapiric folds has ended and the thin salt beds have been deposited in the core of low amplitude folds. The axial surfaces of the folds mostly dip more than 70 degrees. The first traceable orogenic event in Tertiary beds of the basin occurred in the Middle Oligocene. The most severe folding in the kalut basin and also the greater part of the diaper upheavals were made in the Pliocene. The development of diapiric anticlines in this time has caused the upper-layer dips to about 60-85 degrees.