Geological Sketch of the Shillong Plateau in North-Eastern Bengal, 

 hy Heney B. Medlicott, a. m., f. g. s., and Deputy Superintendent y 

 Geological Survey of India. 







Contents. 







1. 



2. 

 3. 



4. 

 5. 



Introduction 



Alluvium 



Supra-Nummulitic 



Nummulitic 



Cretaceous 



... p. 1 



• • » 5 

 ... „ 9 

 ... „ 10 



... „ 18 

 11. Granite 



6. 



7. 



8. 



9. 



10. 



Silhet Trap formation ... p 

 General stratigrapHcal features „ 

 Gneiss Series ... ... « 



Shillong Series ... ... „ 



Khasia Greenstone ... ... „ 



p. 53 



33 

 39 

 46 

 47 

 51 







1. Inteoduction. 





The extensive hill-tract in north-eastern Bengal to the south of 

 the great valley of Assam has abeady been twice noticed in the 

 Memoirs of the Geological Survey of India.* Recent orders of Gov- 

 ernment to investigate some reported coal discoveries in the western 

 portion of those hills have given another opportunity of adding to our 

 information upon the geology of this region. Although it presents a 

 weU defined orographical featm-e of no small extent^ geographers have 

 not yet assigned a name to this area as a whole ; it is locally spoken 

 of in segments by the names of the several tribes which inhabit it. To 

 supply this want, it was proposed, in the last paper above referred to, to 

 call this elevated tract the Shillong plateau from the name of its culmi- 

 nating and nearly central poiut, and avoiding any of the partial names 

 now in use, as likely to lead to confusion. As a plateau, formed in great 

 part of horizontal rocks, its position is remarkable, occupying, as it does, 

 neutral ground in the acute angle between two great regions of special dis- 

 turbajice — the Himalayan on the north, and the mountain-system that 

 separates Bengal from the great valley of the Irrawaddi on thesouth- 

 east. The area that can be described as table-land appears on maps 



* Vol. I, p. 99, and Vol. IV, p. 387. 

 Mem. Geological Survey of India, Vol. VII, Art. 3. 



( 151 ) 



