Geological researches in China, Mongolia, and Japan, during the years 1862-1865.

4 GEOLOGICAL RESEARCHES IN
CHAPTER II.
GEOLOGICAL OBSERVATIONS IN THE BASIN OF THE
YANOTSE KIANG.
A GLANCE at the section (P1. 1) across Central China will show that the Devo-'aoS lMtk4 ^sA. GEJmi-e& Cdz' n' -zmisimrAs seem to peihrn1nmate, at Least at trie surface, over all else. There is only one point in the whole length of the section,
where rocks older than the great limestone deposit rise to the surface, so that if the
former exist, they are buried deep below the level of the sea. I shall give, in a
subsequent chapter, reasons for believing that, at least in the valley of the Yangtse,
there are also no representatives of the Mesozoic formations of later date than the
Chinese Coal measures, and few, if any, of the Cenozoic.
Where the Yangtse breaks through the ridges of the central.anticlinal axis of
elevation, in Eastern Sz'chuen and Western Hupeh, a section, nearly eighty miles
long, is exposed in the succession of deep gorges through which the river passes
this barrier. Here the Devonian limestone is seen to rest almost immediately on
the granite, a comparatively small development of metamorphic schists intervening.
This seems to be the only point between Western Sz'chuen and the Pacific, where
the Yangtse has exposed these lower rocks, and even here they occur during only
about eight miles of the river's course, and with a maximum height of only a few
hundred feet above the river. To their occurrence are due the rapids that render
the navigation of this part of the " Great River" so dangerous.
The granite immediately above the first rapids consists.of a triclinic feldspar and
orthoclase, the former predominating, a brilliant black mica and quartz with small
crystals of sphene scattered through the mass. Above Shantowpien the granite
becomes very fine-grained, and still further up the river it is succeeded by syenitic
granite, composed of white triclinic feldspar, quartz, large laminae of brown mica,
and crystals of hornblende, with minute octahedrons of magnetic iron.
On its eastern and western declivities the granite supports the metamorphic strata.
Those to the eastward, which could not be closely examined, seemed to be gneiss
trending E. W. and dipping about 30~ to S. West of the granite the strata consist, where examined, of hornblendic schist and ehloritic schist, the former often
containing lenticular masses and cross veins of quartz, feldspar, and chlorite. Rolled
fragments of diorite, probably of metamorphic origin, indicate the presence of this
usual companion of these rocks. Near their contact with the granite these strata
trend N. N. E., dipping about 85~ to E. S. E., while further up the river their trend
changes to E. N. E., and the dip to N. N. W.