Hugh J. L. Beadnell — Flowing Wells, Kharga Oasis. 53 



invasion of the area by the Cretaceous sea, the underlying shales and 

 sandstones being as far as known devoid of all fossil remains except 

 vegetable impressions and silicified wood, having in all probability 

 been accumulated in an immense inland lake. 



Underlying the phosphates is a great thickness of an almost 

 homogeneous red or purple shale, below which occurs tlie first 

 water-bearing sandstone ; this will presently be described in detail. 

 Between this sandstone, which for purposes of easy reference I have 

 designated the "surface-water sandstone," and the underground sand- 

 stone from which the flowing wells of the oasis derive their water, 

 is a 75 metre band of grey shale or clay; it is this bed which 

 forms the confining and impervious cover, and prevents the water in 

 the beds below from reaching the surface except when provided with 

 such means of escape as artificial boreholes. To all intents and purposes 

 these shales are impermeable, at any rate over the district in question, 

 and may therefore be referred to as the " impermeable grey shales," 

 The upper layers of this division are visible on the floor of the 

 depression in some parts of the oasis, notably in the Bellaida district 

 west of Jebel Ter, and in the neighbourhood of Ain Mukta to the east 

 of the same range. Their thickness has been determined from the 

 results of about twenty bores put down on the area about midway 

 between Jebel Ter and Jebel Ghennima near the eastern scarp of the 

 depression.^ 



The Longitudinal Monoclinal Flexure. 



Although over the Libyan desert as a whole the general dip of the 

 different sedimentary deposits is steadily northwards, we find con- 

 siderable local variations, especially in the oasis-depressions. In 

 northern Kharga there is a difPerence of level of over 200 metres 

 between the same beds on either side of the depression, the dip being 

 in fact eastwards, as will be seen from the accompanying section across 

 the oasis from the summit of Jebel Tarif to the top of the eastern 

 plateau in the neighbourhood of El Der. The dip appears to mai'kedly 

 decrease, if not die out altogether, on either side, and the structure of 

 the area might therefore be regarded as a simple monocline were it not 

 for the dominant line of disturbance which runs in a north and south 

 direction along the centre of the oasis parallel to the longer axis of the 

 depression. This line of folding and faulting is most marked in Jebel 

 Ter, a hill range bounded by faults and formed of beds let down 

 through a vertical distance of over a hundred metres. Southwards 

 the line of disturbance — in some places a fault, in others a monoclinal 

 fold — can be traced past Jebel Tarwan, Nadura, and Kharga village to 

 the conspicuous highly inclined beds of Gorn el Gennah, and tlienoe 

 passed the old ruined temple known as Qasr el Ghuata, immediately 



1 The localities referred to in this paper are shown on the accompanying map, p. 51, 

 the topoo-raphy of which is based on the maps of the Survey Departmental Report. 

 The scale (1 : 500,000) is of course too small to show each division of the Eocene and 

 Cretaceous, and the boundaries of such as are indicated must only be taken as 

 approximate. On the Survey maps the names of the two prominent outliers of the 

 plateau on the east side of the depression have their names reversed ; the most 

 northerly is Jebel el Ghennima, the other to the south Jebel Um el Ghennaim. 



