BV \v. N. 6E*rsoN. 553 



completely disappear, or they may even be sills, which, in addi- 

 tion, may transgress from one horizon to another, while the 

 presence of an indeterminable amount of strike-faulting permits 

 frequent repetition or complete disappearance of some beds. 

 Hence detailed accuracy is impossible. One must either leave 

 the succession a chaos, or attempt to piece together the isolated 

 fragments of evidence, making as few and as reasonable assump- 

 tions as possible. The latter course appears preferable. 



If reference be made to the earlier columnar section (loc. cit., 

 supra), the lowest portion of phyllites, jaspers, etc., may fairly 

 be correlated with such rocks in the Eastern Series as are not 

 comparable with Western types. They are separated from the 

 Neraingha Limestone by the intrusive mass of the eastern kerato- 

 phyre, a great irregular sill, and an unknown width of transi- 

 tional rocks. There is possibly a fault west of this, causing the 

 disappearance of all but the small mass of the Nemingha Lime- 

 stone in Portion 52, which itself would then be a repetition of a 

 portion of the main zone of the Nemingha Limestone. Beneath 

 this main zone, there is also keratophyre closely similar to that 

 to the east of it, and tentatively correlated therewith. The 

 jSTemingha Red Breccia reaches its maximum thickness near 

 Black Jack, and is possibly there near the point of its eruption. 

 The Nemingha Limestone is not confined to one horizon only, 

 such as the base of the Red Breccia, but may occur in large 

 lenses at various levels within this breccia, though since the 

 breccia must have been rapidly formed, all such lenses of lime- 

 stone arc practically coeval ((/. 6, p. 575). The depth of the sea 

 during the deposition of these limestones must have been con- 

 siderable to permit of the rapid accumulation of such a thickness 

 of breccia, though Mr. Chapman's remarks suggest (see p. 390) 

 that this locally may have risen above sea-level and permitted the 

 foriiiation of oolitic limestone. Such local production of islands 

 of pyroclastic material was shown to be probable in the Tam- 

 worth District. The intrusion of the porphyritic dolerite seems 

 to have been closely connected with the formation of the 

 Nemingha Breccias. 



'J'he deposition of radiolarian cherts and claystones followed 



