Salt-tectonic features of northern Iraq

Structural disharmonies between rock masses lying above and below the salt-bearing lower Fars formation are characteristic of the Alpine foothill folds of the Zagros mountain belt in parts of northern Iraq and southwestern Iran. The typical disharmonic habit in northeastern Iraq is the overthrusting of the northeastern flanks of the long and strongly developed anticlines. The thesis is advanced that the overthrusts resulted from gliding adjustments of each synclinal fill to gravitational changes caused by isostatic recovery of the Zagros after the fold-producing orogeny. Overthrusting essentially postdated the completion of folding, being facilitated by decreases in competency of the anticlinal crests as these became deeply eroded. It was controlled by the excess of load in the northeast of each syncline, which resulted from development of high relief during progressive regional tilting.