LOWER NEW RED, SHROPSHIRE. 



59 



6. Laminae of deposit in the Lower New Red Sandstone. 



a 



b 



a. Calcareous Conglomerate. 



I may here remark, that whether considered in its central or in its lower member, 

 there is no system of rocks, which occasionally offers greater difficulties for determining 

 its real laminae of deposit than the New Red Sandstone. Besides the joints or fissures, 

 the diagonal lines of false stratification are sometimes so prevalent, that it is only by 

 tracing at wider intervals the true laminae of deposit, b.b. (wood-cut), as marked by her- 

 bage or moss, that we can correctly ascertain the real dip of the strata. As these ap- 

 pearances sometimes reoccur, from top to bottom of cliffs two and three hundred feet 

 in height, and as the intervals between the true beds is often fifteen or twenty feet, it at 

 first sight does not seem easy to assign an adequate cause for the accumulation of such 

 a vast number of interjacent laminae, parallel to each other in separate wedges, yet 

 divergent from the lines of true bedding, Such appearancs are to be found, to a cer- 

 tain extent, in rocks of all ages, and however difficult it may be, to explain the precise 

 method, by which water can have deposited the grains of sand in these positions, we 

 have positive evidence of precisely similar phaenomena, not only in young tertiary de- 

 posits like the crag, but also in those accumulations of the modern aera, which having 

 been formed under the sea, have subsequently been raised up, and occupy low cliffs 

 along certain parts of the coasts of our island 1 . 



To the south and north of Bridgenorth, the other strata of the Lower New Red, as 

 exposed on both banks of the Severn, are similar in all respects to those described else- 

 where, consisting of brownish, red, argillaceous and calcareous sandstones, flaglike, 

 calcareous grits, with occasional underlying, slightly red and yellowish sandstones, not 

 unlike certain coal grits. Before, however, we take leave of this tract, a little more 

 detail is called for, respecting the relations of the Lower New Red to the south of 

 Bridgenorth, where the formation has been generally confounded with the Old Red 

 Sandstone ; though it is clearly separated on many points from that system by a zone 

 of coal measures. Such is distinctly seen at Chelmarsh, where a ridge consisting 

 entirely of the Lower Red Sandstone, and associated beds of calcareous concretions, 

 overlies in conformable apposition, and graduates downwards into strata containing 



1 See description of a raised beach on the north coast of Devonshire, by Rev. Professor Sedgwick and Mr. Mur- 

 chison, Geol. Proceedings. (Vol. ii. No. 48.) Mr. Lyell has given an ingenious explanation of the manner in 

 which these transverse lamina? may have been formed by water, in showing how similar inclined planes of sand 

 are accumulated by wind. (See a full examination of this form of stratification, with numerous analogies drawn 

 from the formation of the crag, in Lyell's Principles of Geology, Fourth Edition, vol. iv. p. 91.) Mr. De la 

 Beche also throws light on the origin of this false bedding. (See Theoretical Researches in Geology, p. 88.) 



