1IAYDEN : GEOLOGY OF NORTHERN AFGHANISTAN. 



and cannot be determined with any confidence. They include, however, 

 species of Miliolina not yet described, Spiroloculina sp., and various 

 genera of Textnlaridae, including Bigenerina d'Orb. and Valvulina 

 d'Orb. ( = Tetrataxis Ehr.). 



Douville recognises three /.ones in the Fusulina limestones of the 

 Indo-China and S. E. Asia,! v iz.: 



(i) Upper Permian, with Sumalrina anna Volz, (2) Lower Permian, 

 with N. craticulifera Schw., and (3) Uralian, with Sckwagerina 

 princ.eps Ehr. All these are represented in the limestones of Afghan- 

 istan, which we may therefore regard as extending from Carboniferous 

 to Upper Permian. 



Outcrops of massive grey limestone are common among the hills 

 between Ak Robat and Saighan and also westwards in the Ao and 

 Khargin valleys. Fossils have not been found in any of them, but I 

 have little doubt that detailed examination of the rock under the 

 microscope would enable us to refer most of the apparently disconnected 

 occurrences to the Fusulina limestone and associated limestones of 

 Ghorband and Ak Robat. 



Doab Series. 



Neither in the Shibar area nor on the Koh-i-Ghandak was I able to 

 examine the beds immediately overlying the Fusulina limestone series, 

 but in the latter area it is probably overlain unconformably by Upper 

 Mesozoic rocks. 



In upper Saighan the older formations are overlain unconformably 

 by a volcanic series, which covers a large area both there and in lower 

 Saighan and is evidently younger than the Fusulina limestone. It may 

 be conveniently named the ' Doab series/ being well exposed at and 

 around Doab-i-Mekhzann at the junction of the Kahmard and Saighan 

 rivers. It consists of volcanic ashes, breccias and lava flows with inter- 

 bedded shale and sandstone. Shale is usually more prevalent in the 

 1 Bull. Soc. Ge'ol. France, 4e Ser., VI, 587 (1906). 



