THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE V. VOL. V. 



No. VIIL — AUGUST, 1908. 



<D:EixarXi<rj^iLj -a.rtici-.es. 



I. — On the Evidence toe Desekt Conditions in the Bkitish Tkias. 

 By Professor T. G, Bonxey, Sc.D., LL.D., F.R.S. 



A PAPER by jVIr. J. Lomas on "Desert Conditions and the Origin of 

 the British Trias" appeared last year in the Proceedings of the 

 Liverpool Geological Society,^ and was reprinted, with some slight 

 abridgement, in the J^ovember and December numbers of this Magazine. 

 Yaluable and suggestive as it is, I venture to think that its author, as 

 is not unfrequent with enthusiastic advocates, is attempting to prove 

 too much. I have more than once expressed my beliefs that the pebble 

 beds of the Bunter, perhaps also its Upper and Lower Sandstones, 

 were deposited on a lowland by mountain-fed rivers, and think it very 

 probable that this lowland, in consequence of its geographical position, 

 may have been generally arid, and its temperature rather extreme, as 

 is the case in Turkestan and parts of Persia ; the occasional wind- worn 

 sands being due to the one cause and the angular breccias to the other.^ 

 But I think the Keuper Marls, on the whole, aqueous rather than 

 seolian in origin, and the Lower Keuper Sandstones, with the Water- 

 stones, indicative of the gradual setting in of inland sea conditions. 

 Prom time to time, before the salt lake attained its greatest dimensions, 

 the wind might blow the lowland dust into dunes or carry it away 

 from the shore till much of it settled down beneath the water, but 

 I still think that a large part of the material, which now forms the red 

 marl, was brought down as river mud to this magnified Dead Sea, by 

 the streams which had formerly transported sand and pebbles.* In 

 regard to this, however, we cannot at present speak dogmatically. 

 More study is needed of the constituents of the Keuper Marl, of 

 fluviatile, lacustrine, and even marine muds, as well as of the lighter 



1 Proc. Liverpool Geol. See, 1906-7, p. 172. 



2 See for instance Quart. Journ. Geol. Soc, vol. hi (1900"), p. 288. 



^ See for a fuller statement Quart. Journ. Geol. Soc, vol. Iviii (1902), p. 201. 

 [Also paper on " Wind-worn Pebbles in the British Isles," by F. A. Bather, M.A., 

 F.G.S.: Proc. Geol. Assoc, vol. xvi (1900), pp. 396-420, pi. xi and text-figures 

 (with numerous references to the literature of the subject). — Edit. Geol. Mag.] 



* See for a general statement of my views Proc. Yorkshire Geol. Soc, vol. xvi 

 (1906), pt. 1, on the origin of the British Trias. 



DECADE V. — VOL. V. NO. VIII. 22 



