Terrestrial Carboniferous sedimentation on the northeastern plateau of Djebel Uweinat
 
 -  detected by new finds of fossil plant remains  -

Norbert Brügge, Germany

The presence of Lower Carboniferous strata has been known for a long time from Karkur Murr and Karkur Talh at the eastern side of Djebel Uweinat. It was already known, that the so-named Karkur Murr/Wadi Waddan Formation  (now Wadi Malik Formation in sense KLITZSCH) consist of sandy shales and include often numerous well-preserved plant remains.

The Carboniferous strata of this Wadi Malik Formation are present in varying thickness and facies. It is normally several 10 meters thick and it consists of  crossbedded to flaserbedded sandstone, siltstone and some shale deposited in shallow marine, coastal floodplain or fluvial environment. Parts of the strata are intensively burrowed and brachiopods as well as plant remains of Carboniferous age are common. At Karkur Murr these strata rest directly on methamorphic Precambrian rocks, while at Karkur Talh, as well as east of Djebel Uweinat, they overlie older Paleozoic strata.
The Carboniferous strata at the Uweinat and surrounding areas are a near-shore facies of a transgression from the western Kufra basin. The strata overlain  unconformably the northeastern to southeastern  foothills of the already uplifted mountain range the Uweinat. Remains of strata from the Carboniferous transgression also were found extensive at the northern Clayton Craters and approximately 100 kilometers southeast of Djebel Kissu.
Due to a new assessment of plant remains by Norbert Brügge (were found 1977 and 1984 ) at the southern edge of the Gilf Kebir is a different occurrence of Carboniferous layers is become probable.

In recent years, and especially in 2008, 2009 and 2010 by Andras Zboray, Hungary, and his groups, were found fossil plant-remains on the northeastern part of the Uweinat plateau. The plant-remains of the types "Lepidodendron" and "Sigillaria" are usually not well preserved. The barely layered deposits have a fine-grained or coarse-grained facies. The finds were deposited on intra-Devonian level. It is likely that this deposits are terrestrial, this means, products of the intra-erosion of the Devonian mountains. This facies differs from the shallow-marine or coastal facies on the southeastern side of the Uweinat (e.g. Karkur Murr). The plant-remains are preserved in situ. In contrast, the plant-remains in shallow-marine deposits are allochthon of origin at the southeastern part of the Uweinat.


 

Geological structure of the northern plateau

Massive sandstones of the Silurian age lie unconformably on the methamorphic Precambrian basement. An example is visible at the northern mouth of the Kakur Talh. On the whole plateau in ascending branches of the Karkur Talh occur eroded Silurian sandstones. In the massive Silurian sandstones are included siltstones, common on the bedding planes found traces of burrows from Arthrophycus. The following conformably layers of the Devonian age can be found outside of the valleys in the higher positions on the plateau. The slightly red colored sandstone can be identified by its stratification and graining. The latest Carboniferous terrestrial deposits are not consistently horizon. They occure on infra-Devonian level in paleo-valleys, because they are products of erosive ablation of Devonian strata. The deposits are not clearly layered and have a fine-grained or coarse-grained facies.

  

Most of the following pictures from Andras Zboray                          


Northeastern Uweinat plateau

Southeastern Uweinat plateau: Devonian sandstones at the upper part of the Karkur Murr
 (Background: uplifted Hassanein mountain with Silurian sandstones)

 
Partially cross-bedded Devonian sandstones on northeastern Uweinat plateau

 
 



Loc 2 -- Terrace with debris of Devonian and including Carboniferous, fallen down.



Loc 3 -- Remains of fine-grained terrestrical Carboniferous layers in the foreground


Up to now known finds of fossil plant-remains on the Uweinat plateau



Loc 2 -- Downfalled terrestrical sandstone remains,
            found on terrace 20 metres above valley floor



Loc 2 -- Stigmaria imprint on coarse-grained sandstone



Loc 7 -- Sigillaria aff. cancriformis



 Loc 5 -- Sigillaria imprint on fine-grained sandstone



Loc 3 -- Roots aff. Stigmaria



Loc 5 -- Sigillaria imprints



Loc 8 -- Sigillaria aff. cancriformis



Loc 8 -- dito



Loc 1 -- Lepidodendron sp.



Loc ? -- Lepidodendron aff. veltheimi



Loc 4  -- Lepidodendron aff. volkmannianum



Loc 6 -- Lepidodendron imprint