STRATIGRAPHY OF THE MIDDLE YANG-TZI PROVINCE. 269 
stones and especially their striated surfaces, are positive characteristics of 
glacial till. The evidence of glacial origin is quite as plain as that usually 
seen in the Pleistocene drift of the United States or Great Britain. 
On account of the absence of fossils the age of the Nan-t’ou formation 
is not accurately known. It lies at the base of the Cambro-Ordovician 
limestone, from which we obtained Lower and Middle Cambrian fossils 
within less than 100 miles, 160 kilometers, of Nan-t’ou. Hence it is highly 
probable that these glacial beds on the Yang-tzi are of early Cambrian age. 
Little is known at present regarding the areal distribution of the 
Nan-t’ou glacial beds. The horizon at which they occur is exposed for 
many miles both north and south of the Yang-tzi, at the base of the escarp- 
ment which is crowned by the Cambro-Ordovician limestone; but the 
river crosses it at one point only, and we had no other opportunity to see 
it. At the lower entrance to the Lu-kan gorge Pumpelly examined the 
base of the limestone system and reported 50 feet, 15 meters, of quartzite 
overlain by limestones, which contain many layers and lenticular masses 
of flint.* It is probable, therefore, that the glacial beds do not occur in 
that locality. 
KI-SIN-LING (SINIAN) LIMESTONE. 
The lower strata of the Ki-sin-ling consist of thin-bedded limestone 
with black chert; the greater part is composed of dense limestone, the 
colors of which range from dark bluish-gray to dull liver-brown. The 
upper three-fourths are almost devoid of flint and may thus be distinguished 
from the basal limestones and from the great Wu-shan formation. The 
individual strata are from 10 centimeters to a meter in thickness, are 
rarely slabby, and contain only indistinct sections of coiled gastropods, 
so far as we observed. ‘There are several characters which the formation 
shares with the Sinian limestone of northeast China and paleontological 
evidence indicates an approximate correlation of certain beds. The two 
series were probably contemporaneous and continuous horizontally. 
The Nan-t’ou formation is limited above by an uneven surface, upon 
which lies a thin sheet of conglomerate. The matrix of the conglomerate 
is a greenish argillaceous limestone and the pebbles are like those in the 
underlying tillite. The two formations are therefore related by a basal 
conglomerate, which the till was well calculated to furnish; but it is not 
probable that there was any considerable interval of time between them. 
The conglomerate is at the base of the Ki-sin-ling limestone, and 
between it and the foot of the great cliffs below Nan-t’ou there rise about 
250 feet of rather thin-bedded argillaceous limestones. One of the lowest 
beds is a black and slaty dolomite, which is distinguished by peculiar 

* Smithsonian Contributions to Knowledge, vol. xv, page 6. 
