CHAPTER VI. 
STRATIGRAPHY OF WESTERN CHI-LI AND CENTRAL SHAN-SL 
By BAILEY WILLIS AND ELIOT BLACKWELDER. 
The stratigraphy of western Chi-li and central Shan-si is similar in 
many respects to that already described for Shan-tung. It is, however, 
less well known to us in detail, because in the former province we made 
rather minute surveys of small districts, whereas in Chi-li and Shan-si we 
moved more rapidly and were obliged to leave many things of greater 
or less importance unstudied; and furthermore, the rocks that we saw 
included certain Pre-Cambrian terranes, which present obscure relations 
beyond the reach of any but the most careful investigation. 
In this region we were able to distinguish all of the larger divisions of 
the geologic column found in Shang-tung, with the addition of at least two 
distinct systems belonging to the Pre-Cambrian. The general sequence of 
formations is given in Fig. 16, and in more detail, especially with refer- 
ence to the Pre-Cambrian, in the statement of classification on page 100. 
PRE-CAMBRIAN, 
The time preceding the Cambrian period is represented here by at 
least three distinct systems of rocks, comparable in magnitude with divi- 
sions of the Pre-Cambrian in the United States. The two older ones are 
greatly metamorphosed, while the youngest is much less altered. The 
oldest system is the T’ai-shan complex, consisting of various profoundly 
metamorphic rocks, which we consider Archean, but which are intimately 
associated with granites and other igneous intrusives, many of which are 
less metamorphosed and are presumably Algonkian. The second system, 
the Wu-t’ai schists, is plainly of sedimentary origin, but has been strongly 
metamorphosed. The third, the Hu-t’o system, is composed of slighty 
altered limestones and slates. 
T’AI-SHAN COMPLEX. 
The rocks of the T’ai-shan complex are broadly exposed in the vicinity of 
T’ang-hién and Foéu-p’ing-hién, Chi-li, and along the divide between that 
province and Shan-si. They occur also in the dissected upland west and 
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