ROCKS FROM NORTHERN AND CENTRAL CHINA. 399 
blende crystals have been replaced only by calcite, chlorite, quartz, and 
iron ores, but in the great majority of cases these alteration products are 
obscured by an opaque brownish clay, the nature of which is not apparent; 
this is evidently one of the end products of weathering. 
THE POST-SINIAN FORMATIONS. 
The stratified rocks of this age consist of clastic sediments which are 
probably for the most part non-marine in origin. They are separated from 
the underlying Sinian system by a pronounced unconformity. In central 
Shan-tung two well-defined phases of these rocks have been differentiated ; 
an upper series of shales, sandstones, and conglomerates which are prevail- 
ingly red, and a lower coal-bearing series of shales and sandstones in which 
the colors are variable, but seldom red. ‘The former of these has been 
named the ‘‘Sin-t’ai series’’ and the latter the ‘‘ Po-shan series.”’ 
With these sedimentary strata there are associated in several localities 
numerous volcanic rocks. They occur mostly in dikes, but also in the form 
of flows and intruded sheets. Connected with these eruptives there are 
also fine-grained stratified tuffs. 
ROCKS OF SEDIMENTARY ORIGIN. 
PSEPHITES. 
Pink limestone breccia, No. 39.—These reddish breccias occur in several 
layers interbedded with red clay at Sin-t’ai-hién and northeast of Yen- 
chuang. In many cases the pebbles are more rounded than our specimen 
and the rock would perhaps be called conglomerate. Such conglomerate 
horizons are numerous in the upper part of the Sin-t’ai formation. Speci- 
men collected in the river bluffs, 1 mile east of Sin-t’ai-hién. 
A rock of unusual appearance, composed of angular fragments of dark 
dolomitic limestone embedded in a light reddish matrix which is also 
calcareous. The pieces of limestone are mostly dense brown, drab, and 
purplish-gray rocks, like those which make up the Tsi-nan* division of the 
Sinian system. It is evident that almost all of the debris has been derived 
from that formation. In addition to these pieces of limestone bits of chert 
and grains of quartz are occasionally visible. The fragments are not closely 
packed together and they show no traces of stratification. The rock 
appears to be limestone rubble cemented by calcareous tufa. 
The matrix is composed of very fine-grained calcite, associated with 
an earthy ferruginous matter which imparts to it its reddish color. The 
matrix has a porous or cavernous structure in which, however, we can see 
no trace of organic features; all openings have been sealed with trans- 
parent calcite. 

* See brown limestone, No. 9. 
