YENANGYOUNG. 85 



series of fine hard sandy beds alternating with beds of sedimentary 

 clay, we find here a bed (2) which represents all the characters of 

 eruptive mud ; higher above another bed (3) which, notwithstanding 

 the unconformity above it, unquestionably represents the termination 

 of a bed of eruptive mud. This is followed by a series of rather hard 

 sandstones, alternating with thin beds of clay, into which is injected 

 a horizontal vein of eruptive mud. 



I could easily increase the number of instances, but they all 

 illustrate the same features ; perhaps I might mention a large 

 lump of sandstone, which had apparently been crushed, and its 

 fragments recemented by the eruptive mud which filled the 

 cracks, but this only represents on a smaller scale what is already 

 shown in plate VIII. 



We find beds which thus exhibit all the characters of eruptive 

 mud imbedded in the regular sequence of the strata. 



It is most probable that eruptions of liquid mud took place during 

 the deposition of the strata between which we find the mud streams 

 conformably intercalated. 



All the evidence available leads us to believe that eruptions of 

 mud took place during the formation of the upper Prome and 

 probably also of the lower Yenangyoung stages. This mud spread 

 out in horizontal layers and was thus inclosed in the regular series. 

 We may suppose that subsequently the series of beds was rent by 

 innumerable fissures, through which mud was pressed up, passing 

 through the original horizontal layers. 



As regards the occurrence of these veins I found them in the 

 upper Prome and also in the lower Yenangyoung stages. So far 

 none were noticed in the upper parts of the Yenangyoung stage, 

 while it is certain that they do not occur in the Irawadi series. 

 This seems to me of a great theoretical importance, to which I shall 

 revert in a subsequent chapter ; but it may be mentioned here that 

 up to now I have only observed these veins within the Yenang- 

 young oil field. 



( i3« ) 



