BY W. N. BENSON. 511 



activity broke out again, and the rhyolites, andesites, and tuffs of 

 the Rocky Creek Series were ejected. 



The intrusion of the peridolites then followed; they have been 

 shown to occur chiefly in the fault separating the Eastern rocks 

 from the rest of the country, and it is probable that they were 

 intruded into this fault-plane during the crust-movement. They 

 show some signs of shearing in themselves. That the folding 

 period was at the close of the Carboniferous, is indubitable, in 

 view of the strong unconformity between horizontal or slightly 

 disturbed Permo-Carboniferous beds, and highly disturbed Car- 

 boniferous rock existing at most points, where the two formations 

 are in contact. The serpentine has intruded the Burindi Carboni- 

 ferous Series at Crow Mountain, and a pebble of serpentine occurs 

 in the Permo-Carboniferous sandstones in the Newcastle district, 

 as do also other rocks which have come from the north. The Juras- 

 sic sandstones lie horizontally and undisturbed, on the vertically 

 dipping serpentine-mass near Warialda. The evidence for these 

 statements will be detailed later. Unfortunately, the Permo-Car- 

 boniferous beds and serpentine occurring together in situ, are not 

 clearly exposed, so that a direct proof in this manner is impossible 



The gabbros and eucrites came slightly later than the serpen- 

 tines. Their schistose structure suggests solidification during move- 

 ment, while the dynamic type of metamorphism is indicative of the 

 after-pressure they received by the later stages of the earth- 

 folding. 



Intruding the gabbros and serpentines, are a small series of 

 dykes of dolerite, different from the earlier type of dolerite. They 

 are common in the country north and south-east of Barraba, but 

 have not been sought much elsewhere. In some mineralogical and 

 structural variations, there are strong resemblances to certain of 

 the lamprophyres of this region. 



A third series of dolerites occur, the age and relationships of 

 which cannot be told at present. They make large and small sills, 

 and laccolites in the Barraba Series of rocks, in the region between 

 Burindi Station, Horton and Cobbadah. Blue Knob laccolite is 

 the larger of these. The manner of alteration suggests a Pre-Ter- 



