168 GEOLOGY OF THE SON VALLF.Y, ETC. 



have been attributed to injection from below, as the result of 

 earthquakes, or as an infilling of crevices from above. 



Mr. Diller showed, in the case of the dykes examined by him, 

 that the sandstone must have been injected from below, not formed 

 by infilling from above, and attributed this to earthquake action of 

 the same kind which produces sand vents. Dr. Noetlingin his memoir 

 of the Yenangyoung oil field adopts a similar explanation for the 

 shale dykes formed in that region > 



At Markundi I was unable to get any direct evidence bearing on 

 the origin of these sandstone dykes, The occurrence of fragments 

 of limestone lying with their longer axes more or less vertical sug- 

 gests that they were detached and carried upwards by the sand, for if 

 they had fallen from above into an open but partially filled fissure they 

 would probably be found lying more or less flat, and with their longer 

 axes at right angles to the edges of the dyke. There is also evidence 

 to show that they are not due to recent filling of open fissures in 

 the bending up of the bedding of the limestone against the sandstone 

 of the dykes as seen in Plate 2. This bending is most naturally expli- 

 cable on the supposition that it is due to a slight compression either 

 at the time of injection or, more probably, after the induration of the 

 sandstone. The occurrence of fragments of limestone shows that this 

 had already solidified at the time of formation of the fissures now 

 filled by the sandstone, and this combined with the evidence of their 

 age makes it probable that, as in the American instances, the 

 sandstone is truly intrusive in the limestone, and derived from a sand 

 underlying the limestone, 



The transition rocks of this area are sufficiently treated in the 

 Transition chapter by Mr. Vredenburg. It will only be 



necessary to notice here the occurrence, de- 

 scribed by Mr. Datta, of a curious conglomeratic rock about half a 

 mile south-west of the termination of the Jungel outlier of the red 

 shale series. The rock is described as a fine-grained laminated bluish 

 shale, 5 or 6 ft. thick, through which small well-rounded pebbles are 

 scattered. The rock is exposed on a hillside and cannot be traced, 

 owing to the absence of exposures either eastwards or westwards* 



« Mem., Ceol. Surv. Ind., Vol. XXVII. 



( 168 ) 





