116 E. 0. Teale: 



form occurring in these rocks, and the stresses to which they havc 

 been subjected may liave been favourable to the production of the 

 micaceous form of the ferric cxide. 



One feature worthy of some reference, and well f.hown at Section 

 E, is the fact that the porphyroids appear to have been more affected 

 by dynamical stresses than the underlying older sediments, consist- 

 ing of chloritic shales, slates and quartzitic sandstones. They 

 therefore frequently approach typical schists in character, while 

 the adjoining older bods still preserve the appearance of normal 

 sediments. It is probable, however, that the two steries may have 

 been subjected simultaneously to stresses of the same order of 

 magnitude, but the nature of the mineral composition of the por- 

 phyries and ash beds from which the porphyroids have been derived 

 made them more susceptibb to the development of new structures 

 and mineralogical rearrangement. 



Stratified Ash Btds. — These beds are best s;tudied at Section A 

 and C, Boggy Creek, and at Section D, Ironstone Creek, llie 

 stratification is regular, with an alternation of coarse and fine 

 material, the dip being at a high angle, westerly in sections A and 

 D, and easterly at C. It is well known that a sub- aerial deposition of 

 volcanic ash may result in remarkably regular deposition, and in the 

 absence therefore of definitely aqueous sediments interbedded Avith 

 the ash beds or of the aissociation of fossils in sedimentary material 

 with the pyroclastic, it may not be possible to decide whether the 

 beds in question are really sub-aqueous or not. The fine, purple 

 shales, beds b and d, Seiction A, however, resemble very closely true 

 sub-aqueous .sediments, and may, in fact, be such. No. 16, Sec-tion 

 C, may be taken as one typical example of the normal bedded ash 

 beds, though the degree of coarseness; naturally varies from bed 

 to bed. This example is a light greenish grey granular rock. A 

 thin section shows well the fragmental structure, with abundant 

 chlorite, angular quartz, and some triclinic felspar and magnetite 

 set in a micro-crystalline base of quartz and felspar, with some 

 secondary silicification. 



At Siection D the beds are exposed more or less continuously for 

 about 8 chains, and sometimes show a slight amount of schistosity. 

 A good exposure is to be seen under the road bridge. The colour 

 is in general grey, but darker and lighter bands with slight varia- 

 tions in texture bring out the thin regular character of the bedding. 

 Numerous thin sections (27-39) show a general similarity mineralo- 

 gically. No. 28 is a finely granular grey rock, with a little fels- 



