Abstract
The Farwah Group of Early Eocene age and its equivalents Tajoura, Hallab Formations were deposited on the continental stable shelf along the northern margin of the cratonic African plate.
The deposition started with shallow water facies that range in depositional environment from inner to middle shelf lagoon, where the inner shelf lagoon setting is represented by facies belts 1 and 2 of Bilal Formation and occupy the southern and the southwest part of the shelf. In the centre the less restricted middle shelf lagoon prevailed where facies belt 3 of Bilal Formation was deposited. These facies grade into a deeper shelf environment in the north direction, as indicated by the deposition of the basinal facies of Hallab Formation.
This is followed by the sedimentation of Taljah and Jirani dolomite type facies, which indicate rather shallow and a more restricted condition and dominate the southern edge of the shelf; on the other hand, the centre and the north part of the shelf is characterized by a less restricted condition where sediments rich in large foraminiferas were very common, thus indicating the start of the transgression which began in the Lower Ypresian in the north and reached the south during the Upper Ypresian to Lutetian.
During that time, the increase of water depth initiated a favourable condition for nummulite accumulation (Jdeir Formation) along the shelf margin, and later spreading over the rest of the shelf, forming a large, broad nummulitic bank with a bank-back setting, bordered by Sabkha setting in the southern part of the shelf.These Nummulitic facies grade northward into basinal facies of Hallab Formation which dominate the deep basin off the shelf. Locally, within the back-bank, a bryozoan build-up and high energy facies developed, suggesting a local condition to such deposition existed near the F1-NC41 well during the Early Eocene time.
The termination of Late Paleocene-Early Eocene cycle is marked by a widespread break in sedimentation that is widely recognised. This break between the Ypresian and Lutetian, signalled the beginning of the Middle and Upper Eocene regressive cycle. This cycle is represented by the shales and limestones of Tellil Group.