62 RESEARCH IN CHINA. 
petency of the mass. Planes of parting are very numerous, and the form- 
ation is capable of much internal movement. It was consequently weak 
in opposition to a tangential compressive stress, and liable to local flexure. 
The Kiu-lung formation overlies the Man-t’o formation. In some 
localities it includes an extremely massive limestone, the Ch’ang-hia 
oolite, 500 feet, 150 meters, thick, but elsewhere it is represented by thinly 
bedded shales, in which occur discontinuous limestone lenses. Where the 
massive oolite occurs, the formation is rigid and capable of transmitting 
thrust throughout that area; but where it is composed of shale the forma- 
tion is locally weak and flexible. These two mechanical elements occur in 
one horizon, and consequently afford an opportunity for the development 
of irregular structures through general tangential pressure. 
The Ch’au-mi-tién and Tsi-nan limestones constitute a structural 
unit. Essentially similar in constitution and in bedding throughout, they 
form a thickness of 3,000 feet, 900 meters, or more of massive strata, 
with relatively few and closely adherent bedding planes. A sequence of 
calcareous strata of this thickness and character belongs among the most 
rigid components of sedimentary systems. It is capable of transmitting 
thrusts throughout a very wide area, and to it the rigidity of the Sinian 
system is due. Where the lower member of the Tsi-nan limestone was 
locally shaly, it served to distribute motion between the rigid limestones 
above and below. 
Distribution of structures.—If we regard the Sinian system, together 
with a part of the underlying T’ai-shan complex, as a mechanical strut 
subject to horizontal compression, we may distinguish three elements or 
parts, namely: the T’ai-shan complex, which, by its vertical structure, 
is sharply distinguished from the horizontally bedded Sinian; the rigid 
limestone mass of the upper Sinian; and between these two, the relatively 
flexible layer of the Man-t’o and Kiu-lung formations. Such a strut pre- 
sents two stiff elements and a weak intermediate one. When compressed 
it may, if the resistance to horizontal movement of the lowest and upper- 
most elements be the same, yield by bending in a large curve, and the 
necessary adjustment on the longer and shorter sides of the curve will take 
place chiefly by motion in the inner member. Or, in case the resistances 
to horizontal motion of the lowest and uppermost members be unequal, 
these two members will move past one another, the intermediate one 
serving as a plane of motion and being folded and dislocated accordingly. 
It follows from these considerations that we may expect to find local . 
folds and overthrusts in the Man-t’o and Ch’ang-hia formations, which 
may not be shared, at least to the same extent, by the T’ai-shan complex 
or the great limestones of the upper Sinian. 
