CARBONIFEROUS AND PERMO-CARBONIFEROUS ROCKS, N.S.W. 257 



The Hllldale Tuffs. — So far as bulk is concerned these 

 are the most important rocks of the Burindi Series; they 

 are interstratifled with the other sedimentary rocks, 

 individual beds ranging from less than an inch up to several 

 hundreds of feet in thickness. Towards the top of the 

 series they become increasingly important and at Hilldale 

 form a very massive bed at the top of the series. When 

 they occur as thin beds interstratifled with the mudstones 

 they frequently contain marine fossils and not uncommonly 

 contain fragments of drift-wood. These tuffs are typically 

 fine-grained; uuder the microscope they are found to con- 

 sist mainly of angular fragments of quartz and plagioclase 

 with smaller amounts of hornblende and biotite. Small 

 fragments of volcanic rock also occur. They are essentially 

 dacitic tuffs. 



The Stony Creek Lava Flows. — Three lava-flows occur 

 in this series on the road from Wallarobba to Clarence 

 Town ; whether these are three distinct flows or whether 

 there may be some repetition due to faulting the writer is 

 not yet prepared to say. The first of these flows outcrops 

 on portions 175 and 188 Parish of Wallarobba; the second 

 outcrops in a quarry at the junction of the Wallarobba 

 Road with the road from Clarence Town to Dungog, while 

 the third may be seen crossing the Clarence Town-Glei\ 

 William Road at portion 13 in the Parish of Uffington. 

 These lavas are aphanitic rocks with abundant small pheno- 

 crysts of felspar; in thin slices under the microscope they 

 exhibit phenocrysts of plagioclase, hornblende and more 

 rarely biotite set in a glassy to cryptocrystalline ground- 

 mass; an occasional phenocryst of quartz may also occur. 

 The rock is essentially a hornblende-andesite. 



Ironstone Beds. — Several beds of a titaniferous magnetite 

 occur in this series; these beds have been mapped in detail 

 by J. B. Jaquet and fully described in his monograph on 

 the iron ore deposits of New South Wales. 



Q -December 3. 1919. 



