[ 392 ]' 

 XLVI. Proceedings of Learned Societies, 



GEOLOGICAL SOCIETY. 



[Continued from p. 280.] 



November 23rd, 1910.— Prof. W. W. Watts, Sc.D., M.Sc, E.B.S., 



President, in the Chair. 

 nPHE following communications were read : — 



1. 'The Effects of Secular Oscillation in Egypt during the 

 Eocene and Cretaceous Periods.' By William Eraser Hume, D.Sc, 

 E.G.S., Director of the Geological Survey of Egypt. 



2. ' The Origin of the British Trias/ By A. K. Horwood. 



It is maintained that, though desert conditions prevailed locally 

 during the Triassic Period in Britain, deposition was brought about 

 solely by the action of water ; and the British Trias is a delta- 

 system. 



For, during Carboniferous, Permian, and Triassic times deposition 

 vras mainly in the same area. There is, moreover, a gradual 

 gradation from the Bunter to the Bhaetic, from coarse sediments 

 to fine. The Bunter is known to be of fluviatile origin, since 

 Prof. Bonney first showed it to be so ; and there is a continuity 

 from Lower to Upper Trias, with an unconformity due to the 

 new mode of formation and change in sedimentation. Oscillation 

 and overlapping, which occur in the Trias, are admittedly due to 

 aqueous agency. The Triassic outcrop and the delta-area of the 

 Biver Mississippi again are closely similar. The alternations of 

 pebbles and sands, sandstone and marl, etc., are due to those seasonal 

 changes which are characteristic of deltas. Coloration is original, 

 from below upwards, and not coincident with bedding. The thickness 

 of the Bunter is an argument for a subsiding area. The ferruginous 

 types in the Carboniferous, Permian, and Trias are alike due to 

 delta conditions. The Trias is horizontal now, as originally, away 

 from any ancient hills which it covers, and ' radial dip ' is merely 

 ' angle of rest.' It is only the skerries, furthermore, that are rippled. 

 Screes, too, occur mainly to the south-west of submerged hills. 

 Sandstones thin out eastward, marls westward, and the skerries 

 are on the hills. The surface-features of ancient hills once covered 

 by Trias are quite unaffected ; and desert conditions are merely 

 marginal, limited to granitic or syenitic knolls at one horizon, 

 while in the surrounding area such conditions are absent. Bock- 

 salt and gypsum are also horizontal and continuous in a linear 

 direction. The Keuper gradually merges into the Bhagtic phase, and 

 the latter into the Lias. Since the Bunter sediments came from 

 the north-west into the Midlands, so probably did the Upper Trias. 

 Triassic sediments and those of the Nile are similar, but the first 

 have been acted upon chemically, the latter mechanically. Local 

 metamorphic and volcanic rocks may have provided some of the 

 heavier minerals, but as a whole their source was more distant. 

 The flora and fauna can be grouped in provinces around the 

 delta-head of the Trias. These considerations all point to an 

 aqueous mode of sedimentation in a moist and equable climate ; and 

 desert conditions only prevailed locally. 



