136 KRAFFT: EXOTIC BLOCKS OF MALLA jOHAR. 



flysch is overlaid by great masses of basic igneous rocks, which include 

 a large number of " exotic blocks ", consisting chiefly of limestones, the 

 whole resembling in appearance an extraordinarily coarse breccia with- 

 out any trace of stratification. In describing these masses it will be 

 convenient to deal first with the igneous rocks and subsequently with 

 the exotic blocks, imbedded in the former. 



(a) The igneous rocks. 



Rocks of igneous origin occur, as mentioned above, in the flysch, 

 the youngest division consisting of subaqueous red and green tuffs. 



These have, however, nothing to do with the subaerial basic igneous 

 rocks we have to consider at present. 



A number of rock specimens brought back were kindly determined 

 by Mr. T. H. Holland, who provided me with the following short 

 notes : — 



Petrological evtdence.— Most of the rocks present the characters 

 of lava flows, generally basic in composition, but too much altered for 

 precise determination, and many of these can be referred to as andesites. 

 They have generally a pilotaxitic structure, but their ferromagnesian 

 silicates having been altered beyond recognition, they may as often 

 be related to the diabases as to the andesites : the distinction is not 

 important. Many are distinctly amygdaloidal, but in some the cavities 

 now filled in with calcite may have been the result of secondary altera- 

 tions. 1 Other specimens are spherulitic pitchstones which fall into 

 line with the amygdaloidal and other structures which indicate a vol- 

 canic (surface) origin for most of the rocks. One rock is a serpentine, 

 which has resulted from the alteration of a peridotite. 



Aspect in the field. — In Johar one generally meets with loose 

 debris, consisting of large and small blocks of green and red andesite 

 and finer volcanic material, mixed with a multitude of pieces of sedimen- 



1 A rock specimen collected by Diener near Talla Sangcha was examined by 

 C.V. John, and his notes are communciated in Diener, " Ergebnisse," p. 599. 

 V. John described this rock as an amygdaloidal diabase. It appears to represent 

 a type of near affinity to those of my own collection which Mr. Holland deter- 

 mined as amygdaloidal andesites (see above). 

 ( 10 ) 



