72 RESEARCH IN CHINA. 



Wu-shan-hien, the Carboniferous limestone is beautifully exposed. Its 

 distribution is shown on the geological map of the Yang-tzi gorges, plate 

 xxxvi of volume i of this report. It was also repeatedly crossed in the 

 sections on the Ta-ning-ho in eastern Ssi'-ch'uan, and its relation to the 

 underlying 'strata was thus repeatedly observed by the members of the 

 expedition of 1903-04. The greenish, sandy, and bituminous shales of the 

 middle Paleozoic are followed by calcareous shales, and these by massive 

 gray limestones in which layers and nodules of black flint constitute a 

 conspicuous feature. A pink limestone at the top of middle Paleozoic 

 strata yielded a few fossils already referred to and described in volumes 

 I and HI of this report. They are not earlier than Silurian (Gothlandian) , 

 may probably be Devonian, and may even be as late as the lower Carbon- 

 iferous (Mississippian) . This fauna has nothing in common with that from 

 the base of the gray limestones which closely overlie it, and it is evident 

 that the life conditions underwent a notable change between the two epochs. 

 Nevertheless there is such a uniformity of sequence in repeated sections 

 that the strata can not be otherwise described than as conformable. We 

 are thus led to conclude that in this district the sequence of deposits 

 which began with the lower Cambrian (Sinian) limestone, and continued 

 conformably through the middle Paleozoic, remained unbroken through the 

 lower, middle, and upper Carboniferous. Yet it is to be noted that the 

 sedimentation from late Ordovician to upper Carboniferous time was very 

 meager and may possibly have ceased altogether at intervals in the middle 

 Paleozoic. 



This upper Carboniferous limestone, which we distinguished by the 

 name Wu-shan from its prominent section in the Wu-shan gorge of the 

 Yang-tzi, is probably the same as the Ki-tau limestone of von Richthofen. 

 But until the faunas have been more fully collected and the geology of the 

 entire region more accurately mapped, it is as well that they should be 

 designated by separate names. 



The Wu-shan limestone exhibits a sequence which has been described 

 by Blackwelder in volume i, p. 275. 



In the district in central China which has just been described we have, 

 so far as the faunal evidence goes, a large development of the upper Car- 

 boniferous and only a very meager representation, if any, of lower Carbon- 

 iferous strata. But from this locality toward the northwest and southwest 

 Carboniferous limestones may be traced through the observations of von 

 Richthofen, L6czy, Obrutchov, and others, and they are apparently not 

 restricted to the upper Carboniferous. De Lapparent gives a good synop- 

 sis* of the occurrence of the older Carboniferous strata. In view of the 



* Trait de Geologic, fifth edition, 1906, p. 914. 



