OBSERVATIONS IN CENTRAL SHAN-SI. 171 
STRUCTURAL GEOLOGY. 

By BAILEY WILLIS. 
GENERAL RELATIONS. 
The structure of central Shan-si is closely linked with that of the 
Wu-t’ai district, which has already been described in detail. The general 
trend of the axes of folds extends southwestward from the Wu-t’ai-hién 
basin, northwest of T’ai-yiian-fu and F6én-chéu-fu; and the normal fault 
of the Ki-chéu-shan is represented further south, by the system of faults 
which give rise to the Ho-shan, the Fén-huang-shan, the Ta-hua-shan, 
and the Ts’ing-ling-shan, a system which extends 450 miles, from latitude 
34° and longitude 108° in the province of Shan-si, to latitude 38° 30’, longi- 
tude 113° in Shen-si. The fault system is associated with smaller or 
larger downwarps, which constitute the loess basins of Téu-ts’un, Wu-t’ai- 
hién, Hin-chéu, T’ai-ytian-fu, P’ing-yang-fu, Kié-chéu, and the Wei valley. 
The folding of the Pre-Cambrian and Paleozoic rocks is a structure 
developed by compression probably during early or middle Mesozoic time. 
The normal faulting and warping are features of Quaternary origin, which 
result from vertical movements. We thus have exemplified here two 
great classes of structure, strongly distinguished in character and in time 
of development. ‘The folding has been described in accordance with our 
detailed observations en route between Pau-ting-fu and T’ai-ytian-fu; 
and in our rapid journey between T’ai-yiian-fu and Si-an-fu we added 
nothing beyond the general recognition of the existence of similar structures 
in rocks of like age throughout Shan-si and Shen-si. Our contribution 
to knowledge of these facts is therefore limited, though it embodies some 
corrections of the notes of von Richthofen, as published in ‘‘China.’’* 
Our observations on the normal faulting and warping were made from 
the point of view of physiographic studies as well as structural studies, 
and a full discussion of them involves taking account of the physiographic 
aspects. This section is limited to their strictly structural aspects. 
PRE-CAMBRIAN AND PALEOZOIC. 
OBSERVATIONS EN ROUTE. 
The highway from ‘T’ai-ytian-fu to Foén-chéu-fu, a distance of 55 
miles, 88 kilometers, in direct line, lies along the northwestern margin 
of the plain of the T’ai-yiian basin, much of the way close to the foothills, 
but between W6n-shui-hién and Fon-chéu-fu at a distance of several 
miles from them. The route has been traveled by von Richthofen, 

*China, vol. 1, chapter Ix, pp. 399 et seq. 
