Page:Provincial geographies of India (Volume 4).djvu/71

VII] plateau of the Shan States. Visitors to Maymyo will be familiar with the typical scenery belonging to this system, rolling uplands covered by a thick mantle of poor red clay soil on which the common bracken fern nourishes, shallow valleys or precipitous gorges, and steep cliff-scarps due to faulting. The limestone, when freshly broken, has, like so many limestones, a fœtid smell. It usually includes a proportion of carbonate of magnesia, and in fact varies from a pure lime carbonate to a true dolomite. The rock is characterized by a network of calcite veins, which have evidently filled an innumerable series of fissures, and give the rock such an unstable texture that one blow from a hammer will often shatter a small boulder into fragments, a quality much appreciated by those in quest of road-metal or railway ballast; as the limestone has not been excessively folded this peculiar fracture structure must be regarded as the direct result of pressure, exerted after the consolidation of the limestone and caused by the great earth movements which commenced just before the Tertiary period. Fossils are not frequent but from the small assemblage of forms so far collected, the great bulk of the Plateau Limestone belongs to the Devonian system, and its fauna, incomplete as it is, seems to have more in common with the Devonian of Europe than with that of America. The Plateau Limestone in all probability extends continuously to Moulmein and Tenasserim, and similar limestones have been described in Yunnan and other parts of China. Mr La Touche concluded that the Plateau Limestone was formed under conditions similar to those of modern coral reefs, and that some of the ranges, such as Loi Leng and the Loi Pan-Loi Twang range, may have been islands in the Devonian sea.

Here and there upon the plateau we find small patches of a limestone which differs in many ways from the great bulk of the beds below, and in some places contains abundant fossils. An examination of the latter shows that these