GEOLOGICAL CONDITIONS. 
PRE-CAMBRIAN CONTINENTAL CONDITIONS. 
The material composing the surface of the land that was awaiting the 
advance of the Cambrian sea must have been, as described by Willis, very 
largely made up of clays and sands resulting from the long disintegration of 
the continental surface at a relatively low relief. Applying this conclusion, 
we infer that the Asiatic continent at the beginning of Cambrian time was 
practically a featureless continent and that the transgressing Cambrian sea 
gradually rose, carrying with it the marine life that developed in the sea on 
the continental slopes during the long period in which the pre-Cambrian 
continental surface had been worn down nearly to base-level. 
If we now turn to the life contained in the first series of deposits, the 
Man-t’o formation, we find that it represents the closing epoch of Lower 
Cambrian time that succeeded the faunas of the Olenellus epoch of the older 
western American formations, and the traces of the Lower Cambrian fauna 
that have been found in Siberia. The presence of a portion of the later 
Lower Cambrian fauna in Siberia indicates that this portion of the Asiatic 
continent was at a lower level and hence was traversed at an earlier epoch 
by the Cambrian sea than the portions of southeastern and southern Asia, 
which include Manchuria, eastern and southern China, and northern India. 
The relations of the Cambrian strata to the subjacent rocks compel the 
conclusion that the Asiatic continent was a land surface during the earlier 
part of Cambrian time and during the long Lipalian interval [Walcott, 
19100, p. 14] represented by the deposition of the great series of pre-Cambrian 
sedimentary rocks on the North American continent and the lesser series 
on the Asiatic continent, described by Willis as the Wu-t’ai and the Hu-t’o 
systems. [Willis, 1907, pp. 4-20.] 
In speaking of the rocks of the Hu-t’o system he says: 
All of the rocks of the Hu-t’o system are sedimentary strata: conglomerate, quartzite, 
shale, and limestone, which resemble the unmetamorphosed Paleozoic rocks more nearly 
than they do the Wu-t’ai schists. The physical events which intervened between the close 
of the Wu-t’ai period and the beginning of the Hu-t’o involved greater changes and probably 
longer time than those which occurred after the Hu-t’o and before the Sinian; but the 
presence of a rich fauna in the Sinian seas distinguishes that period from the preceding time, 
during which the life forms, though probably numerous, did not generally become fossil. 
‘The nearest relations of the Hu-t’o system are with the Belt terrane of Montana (in America), 
and it is probable that pre-Cambrian fossils! such as have been found in the Belt may 
eventually be discovered in the Hu-t’o. [Willis, 1907, p. 7.] 
Inthe above-quoted paragraph Doctor Willis unconsciously gives a strong 
argument for the non-marine origin of the rocks of the Hu-t’o system when 

1Pre-Cambrian fossiliferous formations, C. D. Walcott, Bull. G. S. A., vol. x, p. 199, 1899. 
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