elxxxii Journal of the Asiatic Society of Bengal. [N.S., XIV, 
urged against every other case in which similar migration is 
believed to have taken place. They are :— 
1. The mechanical difficulties against the passage of oil 
through considerable thicknesses of comparatively impervious 
shales. 
2. The time factor, more especially the question as to how 
the oil was preserved in the source-rocks during the time they 
were exposed at the surface before the deposition of the 
reservoir rocks. ; 
Too little is known of the exact conditions of oil move- 
The most important evidence for the migration hypothe 
e in 
basal conglomerates of the Upper Tertiary rocks, having 
originated in the same mother-rock. It seems probable, there 
fore, that the oil at Khaur has its origin in the same source: 
rock and has attained its present position in the manner out- 
lined above. 
Origin of the Oil. 
Although there is definite evidence to show that the oil 
‘has its origin at a particular horizon in the Lower Tertiary 
and gypsum in the source-rock and the paucity of wee x 
by some concentration of the salt water by evaporation, pare 
) 
The most abundant fossils in the Lower Tertiary aie 
nummulites, and some beds of considerable thickness at not 
up entirely of nummulite tests. Such beds, however, a cea 
The rocks in which the oil occurs contain @ few — ‘hat 
nummulites but are otherwise barren. It seems probable ©. . 
