72 



Nan-tou sandstone series 



200 m. =Nantou-tillite. 



Precambrian. 



Gneiss and crystalline schists 



Huang-ling 



gneiss. 



It is almost certain that the Ping-shan limestone series of Noda, together 

 with the underlying Lower Clayslate-and Niu-kan limestone series, corres- 

 ponds to the Ki-sin-ling limestone of Willis and Blackwelder ; as Noda 

 found Coscinocyatlnis cf cancellatus Borxemann in the Ping-shan limestone 

 series^' (in a horizon but little above the Lower Clayslate series, and hence 

 some 450 m. above the very base of the Ki-sin-ling limestone), the Cambrian 

 age of the greater part of the Ki-sin-ling limestone became confirmed on fossil 

 evidence. It is a question, however, whether the Nan-tou tiUite — that ancient 

 boulder clay deposit of glacial orign — is really of the Lower Cambrian age, as 

 assumed by Willis and Blackwelder. 



Blackwelder and Willis believed the early Cambrian age of the Nan-tou 

 tillite on account of i) "that it lies at the base of the Cambro-Ordovician 

 hmestone,^^ " and 2) that " the tillite passes into a greenisli shale, consisting 

 of the same materials, including characteristic pebbles, all rearranged by 

 water, and this shale conglomerate grades into the overlying limestone.^' 



Willis, further, sought a support of his view of Cambrian glaciation in the 

 Lower Cambrian Man-to shale of Shan-tung ; this red formation, according to 

 him, is composed of the end product of mechanical and chemical rock decay 

 under special climatic condition favourable to oxidation, the persistence of the 

 red colour in the formation showing that organic substances were not present 

 in quantity, and the absence or poorness of organism in the shore of the Man- 

 to sea indicating the low temperature of that time.*' 



It must not be forgotten that there is another possibility in this connection ; 

 namely, the Nan-tou tillite may be older than Lower Cambrian. I get this 

 impression, first because the Cambrian (if not surely Lower Cambrian) fossil 

 was found in a very high horizon of tlie Ki-sin-ling limestone, as pointed out 



I I See this paper p. 20. 



2) Research in China, voL L, i, p. 269. ' 



3) Research in China, vol. II., p. 39. 



4) Research in China, vol. II., pp. 38-40. 



