44 RESEARCH IN CHINA. 



limestones, which are the equivalents of the Ch'au-mi-tien and Tsi-nan 

 divisions and compare with them in massiveness. The total thickness of 

 the system in northern Shan-si is not far from 4,000 feet, 1,200 meters. 



On the middle Yang-tz'i, in Hu-pei and eastern Ss'i-ch'uan, the Sinian 

 is represented by a limestone which is 4,500 to 5,000 feet, 1,350 to 1,500 

 meters, thick. The great formation is probably capable of subdivision on 

 lithologic and paleontologic differences, but the distinctions are less marked 

 than in Shan-tung or even in Shan-si. Regarding it as a whole it may be 

 called the Sinian limestone, but to give it sharper definition we apply the 

 name Ki-sin-ling, from the pass of that name where the provinces of Hu-pei, 

 Ssi'-ch'uan, and Shen-si corner. It is there typically exposed, and both 

 Cambrian and Ordovician fossils were found in nearby sections. 



At the base of the Ki-sin-ling limestone, at Nan-t'ou on the Yang-tz'i, 

 is a basal conglomerate of pebbles derived from the underlying tillite, 

 embedded in greenish shale. It is but two feet thick and is succeeded by 

 thin-bedded, shaly, oolitic, and in part chert-bearing limestones, 350 feet 

 thick. We did not see the bottom of the formation in any other section, 

 but the thin-bedded limestones probably appear in the gorges of the Yang- 

 tzi and in the mountains near the Ki-sin-ling. 



The upper and major part of the Sinian in the Yang-tz'i sections is 

 massive dark-gray or liver-colored limestone, free from chert. It is prob- 

 ably nearly 4,500 feet, i ,350 meters, thick. Farther north in the Ki-sin-ling 

 pass, it consists of thinner bedded, more carbonaceous or bituminous 

 strata. It is, however, in all its phases a great marine limestone. 



The upper limit of the Ki-sin-ling is indeterminate, as there is a tran- 

 sition from it into interbedded shale and limestone, which passes upward 

 into the overlying Sin-t'an shale. The transition strata are between 200 

 and 300 feet, 60 to 90 meters, thick, and at Sii-kia-pa in Ssi'-ch'uan they 

 yielded middle Ordovician (Trenton) fossils. The horizon is lithologically 

 distinguished by a peculiar stratum of black chert or lydite, which was also 

 found by von Richthofen and L6czy in sections north of Kuan-yiian-hien, 

 Ss'i-ch'uan, 200 miles, 300 kilometers, northwest of Sii-kia-pa. 



The age of the lower part of the Ki-sin-ling is not definitely fixed, as we 

 found no fossils at Nan-t'ou, where the base is exposed; and those which 

 we did find elsewhere were obtained from pebbles. They were picked 

 up on a river bar of the Nan-kiang, near Chon-p'ing-hien, Shen-si, where 

 strata of the Ki-sin-ling form the canyon walls, and they no doubt came 

 from the immediate vicinity and from the lower part of the limestone. 

 They comprise Lower Cambrian Obolus asiatica as well as lower Middle 

 Cambrian types, and represent the top of the Man-t'o and base of the 

 Kiu-lung group of Shan-tung. 



