TATE--ON THE GEOLOGY OF BEADNELL. 



65 



Other conditions of the Carboniferous Era are made known by 

 several of the sandstones, which present ripple-marks, oblique lamina- 

 tion, and fossil worms and worm-tracks, indicating ancient beaches and 

 the action of waves and currents. When deposits are made in com- 

 paratively tranquil water, the planes of the several beds are pretty 

 nearly parallel to each other ; but some sandstones exhibiting in mass 

 this ordinary stratification have also included in them thin layers or 

 stratula, which are inclined sometimes highly to the plane of the 

 principal bed ; of this oblique lamination, or, as it is frequently called, 

 false-hedding, there are many examples in the " Beadnell-sandstones." 

 Both ripple-marks and false-bedding result from the action of waves 

 and currents ; the former being produced by the gentle motion of 

 waves, and the latter by stronger currents. After the recession of 

 the tide, furrows and ridges may be seen on sandy and muddy coasts ; 

 these are similar in form and arrangement to those left impressed by 

 ancient waves on the " Beadnell-sandstones," in which they are beau- 

 tifully distinct ; some of them are large, measuring six inches from one 

 ridge to the other, and they usually trend from east by south to west 

 by north. As the line in which a current moves is at right angles to 

 the direction of such marks, the ancient currents which rolled over the 

 Beadnell coast must have come either from the north or the south. 



Mr. H. C. Sorby has attempted to determine the direction whence 

 currents came by observations on the dip of the stratula, as he con- 

 siders the direction to be the opposite to this dip in relation to the 

 plane of true bedding ; and he concludes from a series of observations, 

 that the drifting current which formed the carboniferous sandstone- 

 beds of the southern part of the coast of Northumberland came from 

 north 9^ east.* The " Beadnell-beds," however, do not not lead to any 

 such general conclusion, for I found in the same stratum, and within 

 a distance of not many yards, that the stratula in one place dipped 

 from 40" to 70° to the north, and in another place at similar angles to 

 the south-west by south. Probably this bed had been formed by the 

 action of strong eddies and counter currents, which piled up the 

 drifted sand with considerable irregularity. 



Most curious and instructive are the fossil worms and their tracks 

 which occur in several layers of flaggy and ripple-marked sandstones 

 * Proceedings of the Yorkshire Geological Society for 1852, p. 232. 

 VOL. ir. F 



