308 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
ance with the crystalline limestones of the Laurentian of Canada 
(Grenville series). 
At Thabeikkyin the steep bank of the river is composed of a soft 
friable rock containing thin beds holding water-worn pebbles of 
Tertiary age. This is confined to the immediate vicinity of the 
river. On the road running to Mogok it is immediately succeeded 
by exposures of the pre-Cambrian rocks. This road _ between 
Thabeikkyin and Mogok, running directly at right angles to the 
strike of these ancient rocks for a distance which, in a straight line, 
is about 40 miles, although by the road it is about 60 miles, affords 
an excellent section across the series, which present a most remarkable 
and striking resemblance to a section through the Grenville series in 
Canada. The section (fig. 2) consists of alternating bands of gneiss 
and white highly-crystalline limestone with some subordinate bands 
of quartzite. The gneisses are in part reddish (sometimes grayish), 
SS 
Tertiary. Granire. Gneiss. Crystalline limestone. Surface covered. 
Fie. 2.—Section from Irrawaddy River to Mogok 
garnetiferous orthoclase biotite gneisses, with many stringers, 
streaks, and lenses of reddish pegmatite running parallel to the 
foliation, closely resembling those so abundant in the Laurentian 
Plateau of Canada. They are excellently displayed at the eastern 
end of the section in the bed of the Yaynee River near the power 
house, about 2 miles south of the village of Mogok, where their 
appearance suggests a series of highly altered and granitized sedi- 
mentary rocks. They are also well seen in many other parts of the 
section. In addition to these there are lght colored pyroxene 
(augite) scapolite gneisses, which occur intimately interbedded with 
the crystalline limestones at Mogok, Kathe, and at many other parts 
of the section. The quartzite, which is white and vitreous in char- 
acter, is seen at milepost 22 on the road between Thabeikkyin and 
Mogok. It contains a little biotite and a few grains of orthoclase 
scattered through it and bears a striking resemblance to certain 
quartzites in the Grenville areas of Canada. There are large 
exposures of graphitic quartzite about 18 miles from the former 
station. 
