PENGANGA— POKARAN. 97 



Plateau limestone.— Descriptive name given by T. H. D. La 

 Touche (Director's General Report, Rec., Geol. Surv., hid., XXXVII. 

 54. 1908) to a limestone forming the plateau country of the 

 Northern Shan States and with a considerable extension to the 

 south. The prevailing type is a whitish or light-grey rock 3 

 weathering to a darker tint and stained by iron oxide. It only 

 becomes arenaceous near its boundary with the older rocks. 

 The composition varies from a pirre calcite through dolomitic 

 limestones to almost true dolomites. The dolomitisation is more 

 complete in the unfossiliferous, massive limestones. Brecciated 

 dolomites receniented by calcite are not uncommon. Oolitic 

 dolomites also occur. La Touche (Mem., Geol. Surv., Ind., 

 XXXIX, 186, 187, 1913) divides this system into two sections :— 



(2) Upper Plateau Limestones (Anthracolithic). Pure limestones, 

 dark grey or blue black in colour, with Fusulina, Pro- 

 ductus, etc., occurring only in detached masses, but not 

 separable from the lower beds. The fossils described 

 by C. Diener {Pal. Ind., New Ser., Vol. Ill, Mem. No. 4) 

 indicate an age corresponding to the Upper and Middle 

 Productus Limestones of the Salt Range. 



(1) Lower Plateau Limestone (Devonian). Finely crystalline 

 dolomites and dolomitic limestones, almost invariably 

 gTeatly crushed, with traces of fossils, minute forami- 

 nifera and corals. This includes at one locality (the 

 Padaukpin Coral Reef) an extremely rich Devonian 

 fauna corresponding to the Eifelian (F. R. Cowper 

 Reed, Pal. Ind., New Ser., Vol. II, Mem. No. 5). The 

 Wetwin shales (q. v.) are also included in this division. 



Plateau quartzites. — See Paniam stage. 



Pokaran beds. — The Lowo and Pokaran beds were first distinguished 

 by W. T. Blanford (Rec., Geol. Surv., Ind., X, 17, 1877), and re- 

 garded as older than the Vindhyan (Jodhpur) sandstones. The 

 boulders, mainly of Malani rhyolites, were considered to be ice- 

 borne, as underlying rocks near Pokaran were striated. Later 

 work by R. D." Oldham (Rec., Geol. Surv., Ind., XIX, 123, 

 1886) revealed similar beds near Bap, 40 miles to the north-east 

 of Pokaran in Jaisalmer State, and here the boulders were 

 partly composed of Vindhyan limestone. The boulder-beds were 

 thus regarded as probably equivalent to those of the Talchir 



