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, 

 19106, 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 W T u-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.] 



In the above-quoted paragraph Doc tor Willis unconsciously gives a strong 

 argument for the non-marine origin of the rocks of the Hu-t'o system when 



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



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