550 GREAT serpentine-bp:lt of new south wales, v.. 



To see the succession most clearl}/, we must commence at the 

 anticline in the valley of the Seven Mile Creek, and follow west 

 along the line of section described by Messrs. David and Pittman. 

 The lowest beds are radiolarian claystones, in places more or less 

 cherty, and associated with several bands of tuff. Above them 

 comes a narrow band of limestone, bent sharply by the anticline. 

 It is not more than fifty or a hundred feet thick, and is so altered 

 by the contact-effect of the adjacent granite, that its fossil-con- 

 tent is scarcely recognisable. The presence of Favosites, Alveo- 

 lites, Biphyphyllum, and a pentameroid shell, was noted by the 

 previous observers. For reasons which will appear subsequently, 

 this limestone is considered to be on the same horizon as that 

 which we have termed the Nemingha limestone. It is associated 

 with more or less tuffaceous material. Above this commence 

 the great thicknesses of radiolarian cherty claystones with 

 lenticular, interbedded, radiolarian limestones, and vast quanti- 

 ties of pyroclastic material, that form the bulk of the Middle 

 Devonian Series. Not far above the limestone, however, is 

 frequently found a finegrained, grey, quartzitic rock, and, above 

 this, is the greatest and most persistent of the zones of igneous 

 rock. In this portion of the district, the Igneous Zone is com- 

 posed chiefly of pyroclastic rock, though, elsewhere on this 

 horizon, large masses of spilite and spilite-porphyry are developed. 

 For convenience of reference, all the Tamworth Series up to and 

 including the Igneous Zone are here classed as the Lower Middle 

 Devonian Series. 



The Upper Middle Devonian Series, above the Igneous Zone, 

 consists of a great thickness of cherty radiolarian claystone, and 

 banded cherts, with lenticular masses of radiolarian limestone, 

 interstratified with pyroclastic rocks. This extends uninter- 

 ruptedly up to the base of the Baldwin Agglomerates in the 

 Upper Devonian Series. If we anticipate the discussion of the 

 distribution of this series, however, it will be seen that, on two 

 horizons in this sequence, limestone might occur. Northwards 

 of Messrs. David and Pittman's line of section, the large mass of 

 limestone on Moore Creek will be found to lie among radiolarian 

 cherts above the Igneous Zone, but far below the Baldwin 



