The oldest known high grade metamorphic rocks of garnet-amphibolite facies of probably Precambrian (pre-Silurian-Devonian) in the Hajiabad Quadrangle are exposed as a basement complex in the area, with older N-S and younger E-W B-lineations. After the diastrophic phase (probably of late Precambrian) reponsible for the metamorphism of the older and lower complex,the horsts of Baikalides were developed in the area. The trend of Baikalid horsts in Hajiabad was E-W and it swings to NW-SE towards the northwest of the area. The horsts were bounded by major faults with the same trends (Fig. 19).
During ?Silurian, Devonian and Carboniferous, several detritic and volcanic rocks, together with some carbonates, were deposited in the E-W to NW-SE grabens existing then between the Baikalides. After this deposition and during a younger phase, probably Hercynian, the rocks were metamorphosed in the green-schist facies and
Fig. 20. direction of maximum horizontal shortening deduced from Neogene axes of fokding in Haji-abad Quadrangle area (cf. Fig. 19).
an E-W B-lineation developed for the first time. The compression in this period refolded the N-S B-lineations previously formed in the highgrade lower complex and a second E-W B-lineation was formed.
The Permian sea transgressed from the north but could not cover the still preserved Baikalides and Hercynides (?), and just covered the northern foothills of the high lands. During the Early Kimmerian orogeny, the area underwent another syntectonic regional metamorphism in the lower green-schist facies. The Baikalides, Hercynides (?) and the horsts of the Early Kimmerian remained as high lands during the Jurassic and the Lower Cretaceous, and some parts remain high lands to day. The Jurassic-Lower Cretaceous sea covered the grabens or the rifts developed in these periods.
A separate rift (the Coloured Melange rift) system developed in the southwestern marginal part of Central Iran (along the present Zagros line) (Fig. 19) During Eocene another rift opened and Eocene flysch were deposited along the Zagros line. The Oligo-Miocene sea only covered the lowlands of the northern Hajiabad area.
The study of the B-axes of the post Neogene folds in this area shows a uniforn E-W direction for the B-axes and a nearly local N-S stress direction during the Zagros Orogeny (Wallachian diashophism) in this region (Fig. 20).