About This Item
Share This Item
The older Palaeozoic of the Libyan Sahara consists of the following terms. Above a highly folded Precambrian (Proterozoic) metamorphic series is found a locally restricted intermediate formation called "Infra-Cambrian" as in the eastern Fezzan (Mourizidie formation). The Cambrian consists of a mantle of cross-bedded coarse sandstones of the Hassaouna formation. The absence of feldspars and heavy minerals, except in some areas, and the general orientation of the sedimentary structures lead one to suppose that material was transported some distance from the south (central Africa). What can be the agents of transport and the conditions of deposition--rivers and deltas over a width of several thousand kilometers--or a shallow sea with wave action?
We can only imagine a Cambrian world very different from that existing now.
With the Ordovician we have a more classic marine sedimentation, with the development of a transgressive regularly bedded series (Haouaz formation) which ended with erosion and an infilling which is stratigraphically chaotic (Memouniat sandstone). From then on the sedimentary structures never had the homogeneity of the Cambrian, being affected by local factors.
End_of_Article - Last_Page 520------------