Paleozoic Sediments of the Oued el-Mya Basin

Throughout the entire Paleozoic the Oued el-Mya region was subjected to generally marine sedimentation. As the Paleozoic sea was unstable, it experienced several cycles of transgression and regression. 

In the dynamics of facies development during the Lower Paleozoic there is a certain similarity throughout virtually the entire Ordovician. The western, central and northwestern parts of the region were subjected to the stable accumulation of finely banded argillaceous deposits. This facies is unfavourable for the formation of good reservoirs in contrast to the predominantly silty-sandy deposits of the rest of the region which are favourable reservoirs. 

During the Lower Paleozoic the continent was under a temperate humid, sometimes even cold climate. This conclusion is based on  

Towards the northwest and in the extreme north the proportion of sandstones and siltstones in the succession decreases and intercalations of carbonates, mostly argillaceous sandstones, make their appearance. These sediments formed in a shallow sea. They accumulated under deeper water than those in the north. According to the adsorbed complex the salinity of the Silurian sea must have been low, probably because of the melting of the glaciers which led to a reduction of the salinity of the basin waters. The basin was not deeper than about 200 m. 

During the Emsian the sea probably became wider and deeper because of a transgression, argillites representing the predominemt rock type. 

---