18 W. iV. Benson — Spiliie Lavas and Radiolarian Rocks 



that in the Tamworth District of New South Wales described by 

 Professor David and Mr. Pittman, for these give clear evidence of 

 their origin in comparatively shallow water.' The occurrence of spilitic 

 rocks among these also has now been determined, liecently the writer 

 has surveyed tlie greater portion of the Great Serpentine Belt of 

 New South Wales, whicli extends from Bingara and Warialda, more 

 than a hundred miles N.N.W. of Tamworth, to beyond Nundle, over 

 thirty miles to the S.S.E. of the same town. A detailed description 

 of this very interesting and diversified area is now in preparation. 

 The following will here suffice to indicate the main points pertaining 

 to the present subject. 



The general sequence of the pre-Permo-Carboniferous formations 

 observed is stated below. The series appears conformable throughout. 

 The figures given are the apparent thicknesses only, and serve merely 

 to indicate how great are the masses of sediment involved. Doubtless 

 mush repetition bj' faulting has occurred, particularly in the older 

 formations, but at present it is impossible to estimate to what extent 

 this is present. The sequence is as follows : — 



Rocky Creek Conglomerates. — These are conglomerates and sand- 

 stones, interstratified flows of rhyolite and trachyte, and felspathic 

 tuff beds. They contain yEnimites ovata and Lepidodendron velthei- 

 iiiianum. Their age is considered Middle Carboniferous, and the 

 thickness is certainly more than 2,000 feet. 



Burindi Miidstonen. — These are composed of evenly bedded mud- 

 stones and occasionally limestones containing a rich Lower Carbon- 

 iferous marine fauna. The thickness is about 1,500 feet. 



Barraha Mudsiones. — These consist of mudstones and clay stones 

 with frequent Itadiolarian bands differing from the non-lladiolarian 

 beds chiefly in their somewhat finer grain size. Frequently bands of 

 andesitic or felsitic tuff are present, also lenticles of non-fossiliferous 

 argillaceous limestone. Lepidodendron aicstrale is abundant. Their 

 age is probably Upper Devonian. Their thickness is very great, 

 apparently exceeding 13,000 feet. They have a wide distribution, 

 covering more than a thousand square miles. 



Baldwin Agglomeratex. — These are coarse agglomerates with rounded 

 ])ebbles of most of the older rocks set in a tufaceous matrix of felspar 

 and augite crystal fragments, chips of spilite, etc. Occasionally 

 narrow, rapidly chilled, spilite flows are interstratified, and rarely 

 bands of very fine-grained felspathic chert containing lladiolaria. 

 These beds commence near Tamworth (Cleary's Hill agglomerates of 

 the previous authors), increase in thickness to over 1,800 feet, and 

 die out again near Bingara, about one hundred miles to the north. 

 Their age is assumed to be Upper Middle Devonian. 



The Tamworth Series comprises Kadiolarian banded cherts and 

 claystones, fine and medium-grained tuff, of a composition similar 

 to the matrix of the Baldwin agglomerates, but with smaller grain 

 size. A well-marked coral limestone occurs, with an abundant 

 Middle Devonian fauna,- sometimes as a string of small lenticular 

 masses, sometimes a broad b;ind. Spilite flows are numerous. They 



1 Quart. Journ. Geol. Soc, 1899, pp. 16-37. 



" K. Etheridge, Jan., Eecords Geol. Survey N.S.W., vol. vi, p. 151. 



