DEVONIAN SYSTEM : PLATEAU LIMESTONE. 



185 



accumulated, the sea was studded with a number of islands occupying 

 the same positions as the present ranges, though not of the same 

 dimensions and altitude ; for it has been observed that as we 

 approach the base of any of these island-like masses, the limestone 

 becomes sandy and in some cases passes into a calcareous sand- 

 stone, indicating the proximity of a coast. Abundant evidence also 

 of the overlap of the lower beds of the limestone series by the 

 higher is not wanting. On the other hand, no conglomerates have 

 been found at the base of the limestone, wherever this is exposed, 

 a circumstance that seems to indicate that the actual line of coast 

 does not occupy the position of the present boundary, but lay 

 further out on all sides. If this was the case, the absence of outlieis 

 is easily accounted for by the readiness with which limestones are 

 attacked and removed by denuding agents. 



The maximum thickness of this great mass of limestone is an- 



j other point on which considerable doubt exists. 



In only two instances yet found within the 



plateau area has the limestone been cut away to a sufficient depth 



to expose the base of it and to allow its position with regard to 



the rocky floor beneath it to be seen. One 

 Section at Lcma. . , . 



of these is in the deep gorge of the Nam-Tu 



or Myitnge river at Lema (C 5), about 15 miles due south of 

 Maymyo. Here the sides of the gorge are entirely composed, down 

 to within 300 feet of the rivei , of the limestones, resting at Lema itself, 

 so far as can be seen, on the upturned edges of the quartzites and 

 shales of the Chaung-Magyi series, which are highly disturbed and in 

 places vertical, and a little to the west upon almost ecpially highly 

 inclined Naungkangyi beds. The limestones are only slightly dis- 

 turbed and the thickness seen here is not less than 2,500 feet ; 

 but every vestige of overlying strata has been removed, and the 

 original upper limit of the formation cannot be determined ; while a 

 considerable thickness must also have been denuded away from the 

 top of the limestones. In any case, then- original thickness here was 

 probably not less than 3,000 feet. 



The other instance is at the southern end of the great, scarp south 



of Kyaukkyan. where a fault has brought the 

 Kyaukkyan scrap, i i • ,i f ■»•, . 



underlying strata to the surface. Here also 



the limestones have suffered very great ly from denudat ion, and their 



original thickness cannot be measured. At the viaduct in the Gok- 



