Late Cretaceous to Late Tertiary States of Paleostress in the Foreland

Analysis of brittle failure structures has been carried out for (22) sites in different parts of the Foreland Folds Belt of northern Iraq. These structures include joints, faults, veins together with stylolite. Geometrical and genetic analysis of joints revealed several joint sets and systems including two sets of tensional joints and four conjugate shear systems. One of the tensional sets is parallel to the fold axes and the other is perpendicular to these axes. The conjugate shear joints in the areas of study comprise (1) two main conjugate systems each of which consists of two conjugate sets or a singular shear set. These are perpendicular to the bedding planes and have definite angular relationship with the fold axes, and (2) two secondary systems each of which consists of joints that are parallel or perpendicular to the fold axes with different angular relationships with the bedding planes. The planar veins are widespread over all the areas of study and are usually associated with two conjugate shear systems (or singular shear joint sets). They have acute or obtuse angles with the axes of the folds in which they exist.