﻿90 



MR. G. W. TYRRELL ON THE 



[vol. lxxii, 



being intimately welded together. Immediately beneath the 

 contact the Carboniferous sediments crop out, dipping westwards 

 at 10°. 



This gradual transition from the lower teschenite to a dense 



basaltic contact-facies 

 can be followed on 

 the eastern side of the 

 stream. On the west- 

 ern side there are 

 much more compli- 

 cated relations. Here 

 a portion in which the 

 dense basaltic schlie- 

 ren are dominant over 

 the coarser teschenitic 

 layers may be distin- 

 guished from one in 

 which the reverse 

 relation holds. The 

 former abuts against 

 the latter horizontally, 

 and overlies and under- 

 lies it. There is also 

 a more or less gradual 

 transition between the 

 two portions. These 

 relations are shown 

 diagrammatically in 

 fig. 2. The coarse- 

 grained teschenitic 

 rock forms conspicu- 

 ous, waterworn knobs 

 in the bed of the 

 stream. As the stream 

 is crossed to the eastern 

 side the fine-grained 

 basaltic schlieren dis- 

 appear, and the tes- 

 chenite passes down 

 normally, as above 

 described, into its con- 

 tact-facies. This can 

 be traced to a small 

 bar of sandstone seen 

 at low water in the 

 bed of the stream. 

 The relations of the 



various facies at the lower contact are suggestive of considerable 

 movement in the magma before crystallization had taken place to 

 any extent, for the minerals show little or no alignment in the 

 direction of the banding. 



