152 RESEARCH IN CHINA. 
that the deposition of the gravels was subsequent to the folding and partial 
erosion of the Paleozoic strata. The conglomerate can hardly be older than 
late Mesozoic, and, judging from the slight consolidation, we are inclined 
to think that it may be younger. Like the Wén-ho conglomerates of Shan- 
tung, the Ning-shan gravels are intimately related in occurrence with the 
normal faults of the vicinity, and are probably the coarser portion of the 
material derived from the demolition of the fault-scarp. The scarp, as 
such, has disappeared entirely, and the gravels must, therefore, be set far 
enough back from the modern period to permit the completion of this 
large work of erosion after the gravels began to accumulate. Upon the 
basis of physiographic studies, Willis concludes that the normal faults 
were produced in early Tertiary time, and we therefore assign the Ning- 
shan formation tentatively to the Tertiary. 
