The geological position of the layers in the pharaonic "Ochre Quarries"
at the Abu Ballas Trail (Western Desert, Egypt)

December 2010
Norbert Brügge, Germany
Dipl.-Geol.

On the route between Abu Ballas -- a depot of water jugs, built in the Pharaonic period -- and the Gilf Kebir plateau, excavated outcrops of red Ochre layers from the Abu Ballas Formation were described. This specially locality were found and photographed in February 2003 by Giancarlo Negro, Italia. In November 2005, have precise explored Giancarlo Negro, Vincenzo de Michele and Benito Piacenza this locality. They come to the conclusion that the Ochre layers was used by mining in the Pharaonic period. The results were published  in Sahara Journal 2005 and 2007. During an expedition to the Gilf Kebir in 2009 explored Richard de Nul, Belgium, and its companions, the "Ochre Quarries" again.

The geological context of the Ochre layers

In connection with the Ochre layers was mentioned the Abu Ballas Formation. This Formation in the Western Desert of Egypt represents a marine intercalation within fluvial, Nubia-type sandstones. These deposits document an extensive transgression of Aptian age flooding the Dakhla Basin from north to south. Due to this first advance of the Tethyan sea during the Cretaceous, sediments of open and marginal marine provenance were accumulated in the SE of the basin.
At the western coast line the Abu Ballas Formation is interfinger with the fluvial Gilf Kebir Formation.

The sedimentary succession of the open marine facies is in sense HENDRIKS & KALLENBACH (1986) divided into five lithostratigraphic units which reflect that deposition was largely controlled by one single transgressive-regressive event. The transgressive sequence in the lower part of the formation comprises sandstones of a backshore to foreshore environment (unit 1) which are overlain by offshore claystones (unit 2). The middle portion of the sedimentary succession consists of silty and sandy strata (unit 3) which are attributed to large-scale redepositional processes due to intensified bottom currents during the maximum extension of the sea. These sediments are capped by off-shore originated claystones (unit 4) grading upwards into siltstones and sandstones of transition-zone to backshore environments (unit 5), which indicate a gradual regression. This stratigraphic sequence documenting a retrograding-prograding shoreline due to the transgression and regression of the Aptian sea, interfingers with silty and sandy deposits of the marginal marine facies of the Abu Ballas Formation. Comparable to the lithostratigraphic units 1 and 5 these strata represent a variety of sedimentary environments ranging from the backshore to the transition zone. They were accumulated on the western slope of the Kharga Uplift bounding the Dakhla Basin towards the east, which was partially flooded while the sea had its maximum extension.
  


  

The stratigraphic sequence of open marine origin which has a thickness of 12.2 m to 27.6 m, is separated into the following 5 units because of lithologic aspects.
Unit 1
The strata of unit 1 comprise white and grey, fine-grained sandstones which are strongly bioturbated. These deposits overlying the Six Hills Formation with a gentle unconformity, where they attain a thickness of 1.5 m. This sequence generally is small-scale wave-ripple cross-laminated. The foreset laminae are more less bundled. Individual sets which often have an undalatory lower bounding surface, and cosets partially are separated by evenly laminated beds with a thickness of 2-5 cm. These occasionally show desiccation cracks and are bare of any trace fossils. The uppermost part of the unit is destratified due to intense bioturbation.
Unit 2
Unit 2 mainly consists of white, grey, green, red and violet, partially mottled, massive or laminated claystones. The thickness of this unit varies from 1.8 m to more than 7.0 m. These strata are bioturbated and contain shells of brachiopods (Lingula sp.), pelecypods and gastropods. The middle part of the unit is made up of white and yellowish grey, laminated, fossiliferous, marly claystones. Locally the uppermost portion of the sequence is characterized by an increasing silt and sand content documenting a gradual coarsening upwards of grain sizes. Lenses and beds of fine-grained sandstone which are horizontally bedded or small-scale wave- and current-ripple cross-laminated, also occasionally occur in this part of unit 2. These intercalations attain a thickness of 2 to 10 cm. The partially calcareous sandstone beds contain bioturbations, among which Rhizocorallium sp. The upper part of this unit is furthermore characterized by the occurrence of concretionary clay-ironstone layers and of coquinas which are up to 5 cm thick and occassionally contain intraformational claystone pebbles.
Unit 3
The deposits of unit 3 comprise siltstones and sandstones which have a thickness of 1.0 to 2.3 m . Yellowish grey and red, horizontally bedded siltstones with trace fossils varying in thickness from 1.0 to 2.2 m. These strata often are clayey and partially contain claystone layers. The siltstones occasionally are calcareous again. They alternate with bioturbated, fine-grained sandstone beds, which show small-scale wave-ripple cross-lamination and which are up to 10 cm thick. The uppermost 0.1 m of unit 3 within this section consists of an intraformational conglomerate overlying a minor erosional unconformity. This unit is almost completely made up of red and violet, bioturbated, fine-grained sandstones. These sediments which attain a maximum thickness of 2.1 m  are small-scale current- and wave-ripple cross-laminated. In the latter section they overlie a grey, massive siltstone bed with a thickness of 0.2 m.
Unit 4
The strata of unit 4 again are made up of grey, green, yellowish brown, red and violet, partially mottled, massive or laminated claystones. They vary in thickness from 3.4 m  to 6.9 m. These sediments contain various brachiopods, pelecypods, gastropods and trace fossils. In the uppermost 1.0 to 2.0 m of the unit horizontally bedded siltstone layers with a thickness of 1-5 cm and intra-formational conglomerates with a thickness of 5-15 cm occur. The intraformational claystone pebbles have a maximum diameter of 2.5 cm. A fining-upward sequence with a thickness of 0.4 m appears in this part of unit 4. It consists of a basal intraformational conglomerate (10 cm) erosively overlying claystones, which upwards grade into grey, bioturbated siltstones (15 cm). The latter strata are horizontally bedded in the lower part and small-scale wave-ripple cross-laminated in the upper part.
They upwards grade into white, laminated, silty claystones (5 cm) which in turn are erosively capped by horizontally bedded siltstones (10 cm). Nearly this entire unit which comprises variegated, massive claystones with a total thickness of 5.6 m, is destratified by roots penetrating the sequence from the overlying Sabaya Formation. Only the lowermost 0.5 m of the unit which consists of laminated, silty claystones, is not uprooted.
Unit 5
The deposits of unit 5 generally are made up of siltstones and sandstones attaining a thickness of 5.0 to 15.6 m. Although the strata of this sedimentary succession in all sections studied have more or less the same lithofacial, stratofacial and ichnofacial characteristics, conspicuous regional variations occur.
The lower part of the unit 5 comprises grey, bioturbated siltstones with an upward increasing sand content. Coinciding with the gradual coarsening of grain sizes, even lamination progressively is replaced by small-scale current- and wave-ripple cross-lamination. Within these siltstones numerous grey and red, massive or laminated, thin claystone layers are intercalated. The upper portion of unit 5 in this section is made up of grey, reddish brown and violet, fine-to medium-grained sandstones which are partially strongly bioturbated.
These deposits are mainly evenly laminated or small-scale current- and wave-ripple cross-laminated. The uppermost part of this sedimentary succession consists of grouped sets of large-scale cross-bedded psammites alternating with small-scale current- and wave-ripple cross-laminated strata, which fill up a local through-shaped depression. The individual large-scale cross-stratified sets within this sequence have an erosional, planar or scoop-shaped lower bounding surface. The angular relation of the lithologically homogeneous, tabular and concave-upward foreset laminae to the lower bounding surface is discordant.



Reference profile through the Abu Ballas Formation
in sense  BARTHEL & BOETTCHER, 1978


The geographic position of the "Ochre Quarries":  24°12'48''N / 27°11'28''E

 


Sources:

W. BARTHEL & R. BÖTTCHER -- Abu Ballas Formation (Tithonian/Berriasian; Southwestern Desert, Egypt) a significant lithostratigraphic unit of the former "Nubian Series"
Mitt. Bayr. Staatsslg. Paläontologie hist. Geol., 18, 1978, München, Germany

Ronald BÖTTCHER -- Die Abu Ballas Formation (Lingula Shale) (Apt ?) der Nubischen Gruppe Südwest-Ägyptens.
Eine Beschreibung der Formation unter besonderer Berücksichtigung der Paläontologie
Berliner geowiss. Abh. (A), 39, 1982, Berlin, Germany

Ronald BÖTTCHER -- Environmental model of the shallow marine Abu Ballas Formation (Aptian, Nubia Group) in South-Western Egypt
N. Jb. Geol. Paläont. Abh., 196, 3, 1985, Stuttgart, Germany

F. HENDRIKS & H. KALLENBACH  -- The offshore to backshore environments of the Abu Ballas Formation of the SE Dakhla Basin (Western Desert, Egypt)
Geologische Rundschau 75/2, 1986, Stuttgart, Germany

    

"Ochre Quarries" and surrounding







 

 Richard de Nul (Belgium)

 
 
   

 
Giancarlo Negro et. al. (Italia)

 
  
 
 
 
"Mud Pans" at the Abu Ballas Scarp

The attraction in the "Mud Pans" at the Abu Ballas Scarp are the "Red Lions" yardangs. There are layer-remains of the Abu Ballas formation (marine Cretaceous layers, not prehistoric lake deposits), eroded by strong northern winds.
 



 

Gilf Kebir Crater Field (GKCF)

At the southern Scarp - in the southwest and northwest of the crater No.13 - I have found some smaller crater shaped structures in 2010. Here are the outcrops of red and yellow layers of the Abu Ballas Formation in erected position.
  

 

Area of the Scarp-Contours