79 PASCOE: GEOLOGICAL NOTES ON MESOPOTAMIA. 



CI 



seepage and oil-well waters ; the baths of Hamniam Ali are an 

 example of this. Rogers formed the opinion that hydrogen sulphide 

 in the Coalinga and other oil-fields of California was probably 

 produced by the reduction of sulphate by hydrocarbons. 1 That 

 this is the case in Mesopotamia is borne out by the fact that 

 petroleum indications, occurring as they do in a highly gypsiferous 

 series, are, so far as my experience goes, invariably accompanied 

 by hydrogen sulphide. It cannot be maintained that the converse 

 is invariably true, but my experience has been that on searching 

 lon<r enough and deep enough immediately around the vent of 

 any hydrogen sulphide emanation, bituminous earth will in nearly 

 all cases be found. The question is of considerable economic im- 

 portance, since it renders a hydrogen sulphide emanation almost 

 equal in importance to an oil seepage, as an indication of the 

 presence of oil below the surface. Numbers of these " sulphur 

 springs" have been marked on the maps and- are reported con- 

 stantly by native inhabitants, and nearly all those I have examined, 

 have proved to be bituminous to a greater or less extent. 



Date of Movement. 



Flexuring of the Tertiary rocks into anticlines and synclines took 

 place of course after the deposition of these rocks, i.e., in post- 

 Tertiary times, but indications are not wanting that this lateral 

 disturbance had commenced as early at least as the beginning of 

 the Kurd or Bakhtiyari period, and probably in the Fars period ; 

 whether it preceded the latter will be known perhaps when the 

 Nummulitic series has been surveyed. This movement probably 

 continued unevenly during the deposition of the whole of the Kurd 

 red clays and sandstones and undoubtedly survived the last recorded 

 zones " d " and " e." The indications of an early commencement 

 of the movement may be summarised as follows : — 



(i) The rapid steepening of the dip in the more compressed 

 folds in passing from the lowest zone of the Kurd series 

 down into the Fars, may be explained — among other 

 ways — on this assumption. This rapid steepening or 

 erection of the anticlinal core was noticed in all the 

 compressed folds examined. A similar steepening occurs 

 in Burma in the neighbourhood of the junction of the 



1 United States Geol. Sur. Bull. 653 (1917), p. 114. 



