48 RESEARCH IN CHINA. 
PRE-CARBONIFEROUS UNCONFORMIT Y. 
We observed no rocks of Silurian, Devonian,* or Lower Carboniferous 
age in Shan-tung. The coal-bearing series lies in all cases directly upon 
the surface of the ‘'si-nan limestone. We found the two systems in 
adjacent outcrops at Ts’ai-kia-chuang, on both sides of Yen-chuang, and 
at Po-shan. In the last two of these places the actual contact was well 
exposed, revealing the fact that, although the coal-measures agree in dip 
and strike with the underlying limestone, as if the succession were conform- 
able, there is a very distinct erosion unconformity. As stated elsewhere 
in this report, the rocks of this region suffered no considerable amount 
of deformation during the Paleozoic era, and therefore unconformity of 
bedding between the two Paleozoic formations is not to be expected. 
In the shallow canyon of the Siau-fu-ho, the basal shales of the Po- 
shan series may be clearly seen in contact with the Ordovician limestone. 
The surface of the latter is irregular and cavernous, the cavities and prom- 
inences being rounded and tufaceous, like the exteriors of limestone 
outcrops which have long undergone terrestrial weathering. ‘This irregular 
surface is filled in and covered by evenly bedded green and blackish shales. 
They completely fill the old solution cavities, surround the protuberant 
points, and overspread the whole contact as they grade upward into the 
higher strata of the Po-shan series. The logical inference from these 
relations is that the Tsi-nan limestone emerged, without notable warping, 
at some time prior to the Po-shan epoch of the Carboniferous. It then 
suffered weathering and, doubtless, a limited amount of erosion. At the 
beginning of the Po-shan epoch, presumably attending a slight subsidence 
of the land, the sea or some other body of quiet water encroached over 
the weathered surface of the limestone. Fine clays were washed and 
sifted into the caverns and minor recesses, completely filling them and 
cementing the superficial limestone rubble into an agglomerate. 
Since the limestones were not folded or appreciably inclined before 
the period of erosion, the dip of the subsequently deposited shales is con- 
cordant. The character of the contact is amply sufficient to prove an 
unconformity. The absence of Silurian, Devonian, and Lower Carbon- 
* Lorenz states (loc. cit., p. 16) that a great period of sedimentation began in the Upper Devonian 
and continued on through the Carboniferous. The evidence which he furnishes seems to us quite insufficient 
to prove the statement. The lowest fossiliferous beds above the Ordovician limestone are not older than 
uppermost Lower Carboniferous according to Frech, who has recently reviewed the fossils brought by 
von Richthofen from Po-shan and by Lorenz from the same locality. He considers them to be of late 
lower Carboniferous age. (Neues Jahrb. fiir Min., 1895, p. 47.) The barren beds beneath are 100 to 300 
feet thick, but form a continuous sequence with the fossil-bearing strata, and at their base are fine shales 
which lie in caverns and crevices in the limestone. 
