Notes on the Geology of South-Central Ceylon

Abstract

I. Introduction The following notes are the result of a tour of a few weeks' duration in the south-central parts of Ceylon. The time spent in the island was brief, and the work was done entirely upon inland sections; but in many places the exposures of rock are good, especially along the lines of railway. Petrological descripions of Ceylon rocks are not wanting, but details of their field-relations are few, and it is hoped that the following paper may direct attention to the interesting problems which are likely to arise from such an investigation. II. The Gneissoid Granulites ( a ) On the Ceylon Government Railway: from Rambukkana eastward in the direction of Alagala.—Leaving the station at Rambukkana, and proceeding along the metals, we walk over country which is flat, or nearly so, for about 1/2 mile, when we come to a small cutting. Here is exposed a rather coarse granitic rock with pinkish-brown felspars up to ·3 inch across. In about 6 yards this gives place to one more finely grained, rather saccharoidal in appearance, and speckled with patches of mica. On the opposite Bide of the railway-line the rock is banded, but not in the clear even way which, for instance, characterizes the gneiss on the south side of the St. Gotthard Pass. The darker parts are rich in hornblende and brown mica, and contain little or no quartz. These bands often have a wavy habit, as though torn, and sometimes small black patches, like fragments