GEOLOGICAL NOTES ON COAL AND IRON ORE 99 



Coal-seams occur throughout the entire Carboniferous 

 series. The oldest are generally thin, seldom more than 

 one foot in thickness, but the higher we proceed upwards 

 the thicker are the seams encountered. The maximum 

 seams are met with in the uppermost part of the coal series 

 and are probably of Upper Carboniferous age. 



The section I have taken through the Carboniferous sedi- 

 ments in the marginal districts of the Taiyuan basin, shows 

 that the coal seams are in most cases intimately connected 

 with marine horizons, and generally appear immediately 

 below these ; being separated from them by a sometimes 

 thin, sometimes more thick horizon of black plant-bearing 

 clayey sediments. This is, however, not always the case, 

 because sometimes the roof of the coal-seams is formed 

 by quartz -sandstone. Of thirteen observed coal-bearing 

 horizons, ten appear just below marine limestone, whereas 

 three are super-imposed by quartz -sandstone. (See Section). 



Of the primary stratigraphies! conditions which have 

 prevailed in the roof of those layers which contain the 

 maximum coal formation, I am unable to form an opinion 

 for the reason that between the latter formation and the 

 superimposed Permian sediments an unconformity has 

 occurred. 



The intimate connection between the coal seams and 

 the marine sediments seems to indicate that the material 

 in the coal seam has been accumulated in the vicinity of 

 the sea, to be more explicit on the frontier between the 

 sea and fresh water basins. 



As has been pointed out by J. Walther the importance 

 of water for coal formation lies in the fact that although 

 large quantities of cellulose can be formed above as well as 

 below water level, yet it can only be stored in great masses 

 if it is protected by a covering layer of water. 



Walther points out that in warm and moist climates 

 the cellulose of the plant-remains become— when air gets 

 access— decomposed by bacteria which break up the cellulose 

 mainly into gaseous substances. "Even in the tropical zone, 

 so abundant in vegetation, the rotting plant-remains are 

 accumulated onlv where the jungle soil is kept constantly 

 moist or where the level of groundwater rises above it. - 

 (J Walther: A. Allgemeine Palaeontologic, 1 Teil, p. 162). 



This theory might furnish an explanation of the suc- 

 cession of sediments in the coal formation of Central Shansi 



23 Translation by E. Norin. 



