Chapter X: Geological Notes

Geologically the country traversed on the various journeys described in this book may be divided into two sections, separated roughly one from the other by the outer loop of the Great Wall.

South of this line, in Chihli and Shansi, the outcrops are chiefly of sedimentary rocks, with here and there masses of the underlying plutonic and metamorphic rocks showing through. Thanks to Baron von Richthofen and Bailey Willis these rocks are pretty well understood, and there remains only the work of recording their occurrence in different localities, and any other geological phenomena hitherto unobserved. These stratified rocks extend westward and northward across the Ordos, North Shensi and well into Kansu, and also up to the extreme north-west of Shansi.

North of the outer loop of the Wall the outcrops are entirely igneous and metamorphic, granite, trachyte, basalt, porphyry, gneiss and schist occurring in great confusion, so that considerable time, much close study and hard work will be required to reduce them to a system. There is evidence of great volcanic disturbance all along, and northward of this border line.

Nowhere are the sedimentary rocks visible, except well to the east of the eastern extremity of the loop, and far to the north-west of its western extremity.

This chapter is divided into nine parts, each dealing with a different section of country. The first four include the sedimentary formations which lie south of the outer loop of the Wall; while of the others, four consist of notes upon the igneous and metamorphic rocks just mentioned, and one (Part 8) deals with the recurrence of the sedimentary rocks in and west of North-western Shansi.

The parts are as follows:—