54 RESEARCH IN CHINA. 



Productus semireticulatus, accompanied by numerous other brachiopods, 

 bivalves, corals, and fenestellas; and (3) an upper limestone more than 

 i, 600 feet, 480 meters, thick, which is separated from a bed of coal of the 

 preceding member only by a thin stratum of black shale and is similar in 

 nature to the lower limestone. The Ki-tau corresponds in a general way 

 with the Wu-shan limestone. 



The further description deals with beds of Mesozoic and later age which 

 rest unconformably upon the Carboniferous. 



A type of the middle Paleozoic is found in central China, in eastern 

 T Ss'i-ch'uan, southern Sli^ii-si, and western Hu-pei'. The region is moun- 

 tainous, the strata are folded, and exposures are practically continuous in 

 the superb canyons of the Yang-tzi-kiang and its tributaries. 



Descriptions of supposed Devonian rocks in place are given by Pum- 

 pelly in his account of the Yang-tzi gorges. The great limestone which rests 

 on the pre-Cambrian rocks, and is now known to be of Cambro-Ordovician 

 age, was called by him Devonian on the supposition that the fossils of that 

 age from China were from the limestone in question. In fact, Devonian 

 in that region is either absent or represented by the shale which appears 

 immediately above the limestone in several places in the gorges through 

 which Pumpelly passed in his adventurous journey.* 



Sections observed by our expedition occur on the Ta-ning-ho, longitude 

 110 east, and on the Yang-tzi'-kiang, from that meridian east to I-chang.f 

 At the base collections of middle Ordovician fossils were obtained from the 

 transition strata of the Ki-sin-ling limestone near Su-kia-pa, a village on 

 the Ta-ning-ho in eastern Ssi-ch'uan, latitude 31 40', longitude 109 40'. 

 From a local bed at the top, a pink limestone near Ta-miau-ssi', we obtained 

 forms which may be Devonian or lower Carboniferous. 



At Su-kia-pa the middle Paleozoic strata lie in a closely folded syncline, 

 with nearly vertical dip between outcrops of the underlying Ki-sin-ling, 

 (Sinian) limestone. The sequence is continuous, conformable, and appar- 

 ently complex; the following are the principal rocks in order from the top 

 downward : 



Massive gray limestone, with abundant black chert nodules and upper Carboniferous 

 fossils; base of the Wu-shan limestone. 



Sandy shale, chiefly green, in part black; calcareous, ferruginous, bituminous, and 

 coaly near the top ? also bituminous and black 200 to 300 feet, 60 to 90 meters, 

 above the base; weathers earthy brown and iron stained: total 1,800 feet, 550 

 meters; Silurian, Devonian, or lower Carboniferous fossils at the top. 



Gray limestone, 200 feet, 60 meters. 



* Smithsonian Contributions to Knowledge, vol. xv, Geological Researches in China, Mongolia, 

 and Japan, during the years 1862-65, R. Pumpelly, pages 5-6. 

 (Vol. i, pp. 270-271; atlas sheets d 6 and d 7, geology. 



