8 



RESEARCH IN CHINA. 









Observations of the contact between the Hu-t'o and the overlying 

 Sinian show clearly that the former were folded, intruded by dikes, and 

 eroded, before the latter were laid down.* 



The Hu-t'o strata apparently constitute a sequence, which consists of 

 conglomerate and sandstone, clay slates, and siliceous calcareous strata. 

 The entire series is thinly bedded and the three elements (sands, clays, 

 and carbonates) occur interbedded. In the type locality we observed a 

 number of partial sectionsf which we could not connect on account of the 

 extensive covering of the Huang-t'u, the loess formation. The sandy rocks 

 appear to preponderate near the base and the limestones increase in pro- 

 portion toward the top. This distinction appeared to be sufficiently marked 

 to separate a lower argillaceous group from an upper calcareous one, and 

 we have described the former as the Tou-ts'un slates and the latter as the 

 Tung-yu limestone. The division has local significance only. 



The Tou-ts'un slates comprise the lowest beds of the Hu-t'o series and 

 have a thickness of not less than 3,500 feet, 1,000 meters; they may reach 

 5,000 feet, 1,800 meters. The principal strata are earthy gray to purplish 

 slates, or locally phyllites, with which occur thin layers of buff to pink 

 dolomite and siliceous limestone. The lowest beds seen, which we take 

 to be near the base of the series, are of red and gray quartzite with local 

 layers of conglomerate. 



The Tung-yu limestone includes all the upper part of the Hu-t'o 

 system. The characteristic rock is gray limestone, in which chert is usually 

 present in notable quantity and often in masses or sheets. The massive 

 beds of limestone vary in thickness from 10 feet to 500 feet, 3 to 150 meters, 

 or more, and strata of gray to red slates or phyllites occur between them. 

 The sequence is very like that of the underlying Tou-ts'un group, but the 

 relative proportions of slate and limestone are reversed. The thickness 

 of the Tung-yu limestone is probably 3,000 feet, 900 meters, or more. 



Throughout northern China there is a limestone formation which is 

 lithologically identical with the heavy beds of the Tung-yii group, and 

 occupies the stratigraphic position of the whole Hu't'o series. We regard 

 it as the equivalent of the Hu-t'o, but have given it the distinctive name of 

 Ta-yang from a village in Chi'-li near which it is well developed, longitude 

 115 5 o',latitude 38 45'. 



The Ta-yang is a dark-gray, massive limestone, which is distinguished 

 from the very similar Sinian limestones by abundance of chert and absence 

 of fossils. The formation is exceedingly uniform in lithologic character; 

 the greater or less proportion of chert and the occasional occurrence of 

 white quartzite being the chief variations. A notable characteristic is found 



*Vol. i, p. 136. 



t Ibid., pp. 123-125. 



