38 RESEARCH IN CHINA. 



quartz, clay, and oxide of iron, remain in notable quantities. The material 

 resulted from disintegration of crystalline rocks under climatic condi- 

 tions favorable to oxidation, or passed through stages of accumulation 

 as a continental deposit, during which it was subject to such conditions, 

 and was laid down without undergoing chemical reduction or abrasion or 

 sorting. The rock is red throughout, as the Permian and Triassic sand- 

 stones are, and like them was not only originally a red mud, but formed 

 a red deposit. It did not become blue, as the red muds of Virginia now 

 do in Chesapeake Bay in consequence of abundant organic matter. The 

 persistence of red in the Man-t'o formation shows that organic substances 

 were not present in quantity. 



Waves, of which ripple marks on the sandy shales are here and there 

 evidence, accomplished but little work in the way of sorting. They were 

 evidently too weak to sort sediment in which the proportion of mud was 

 so great. 



Calcareous layers occur in the Man-t'o formation occasionally very 

 near the base, persistently at horizons 100 to 150 feet, 30 to 45 meters, 

 higher up, and again, less commonly, near the top, which is often sandy. 

 A transition into the overlying limestone of the Kiu-lung group is formed of 

 interbedded brown shale and gray limestone. Individual limestone strata 

 are very uniform in thickness, though but a few inches, or at most 10 feet, 

 thick and not of great extent. The more continuous are those near the 

 middle of the formation, which were found in all the sections in the Ch'ang- 

 hia and Sin-t'ai districts in Shan-tung. 



The interbedding of the shale and limestone is irregular; it does not 

 follow any rhythm. It is apparent that local conditions were unlike in 

 adjacent waters at any one time and varied in unlike manner from time to 

 time; but red sediment from the land or calcareous sediment from the sea 

 was deposited at any time. The condition which favored precipitation 

 of lime, whether chemically or organically, was continuously present and 

 became effective whenever the environment became right; and so with 

 the mud. It is not possible to assume that the limestones were laid down 

 in deep waters; they are too closely related to the shales and sandstones 

 which were deposited in shallows. As the limestones are relatively free 

 from clay, and what they do contain is very fine, the lime-depositing waters 

 were comparatively clear, and this clearness appears to have been the 

 essential condition. 



One may form a concept of the conditions somewhat as follows: Along 

 the flat, red shore of the Man-t'o sea, bars and islands formed where streams 

 emptied, and shut off the mud-carrying currents from intermediate stretches 

 of coast. More or less extensive lagoons were thus produced and within 



