48 GEOLOGY OF LOWER MESOZOIC ROCKS OF QUEENSLAND, 



Mr. Marks towards the New South Wales border, has been com- 

 menced by Mr. J. H. Reid, of the Geological Survey. 



Other areas of Lower Mesozoic rocks in Queensland have been 

 studied in detail by other officers of the Geological Survey, the 

 more important ones being : the Stan well Coal-Measures, ex- 

 amined by Mr. Dunstan;* the Laura Coalfield, west of Cooktown, 

 by Mr. Ball;! the Lower Mesozoic rocks in the Roma district, 

 by Mr. Saint-Smith. Unfortunately, the full results of Mr. 

 Saint-Smith's work have not been published, but a summary was 

 communicated to the Second Interstate Conference on Artesian 

 Water. I For local details regarding these areas, reference must 

 be made to these publications. 



(c) Litholoyical Chavdcters. — The lithological characters of the 

 Lower Mesozoic rocks in Queensland do not call for very special 

 remark. For the greater part, they consist of sandstones and 

 shales in varying proportions, with which are associated occa- 

 sional conglomerates, grits, and also coal-seams. 



The Ipswich Series consists, for the most part, of light-coloured 

 shales and sandstones, with associated conglomerates, and four- 

 teen or fifteen workable coal-seams. There are coarse conglom- 

 erates developed near the base of the series, indicating vigorous 

 erosion in the early portion of the period. 



The Brisbane Tuff, which is near the base of the Ipswich 

 Series in the Brisbane area, is a rock probably of volcanic origin 

 (though there is no indication of its source), resulting from the 

 deposition of volcanic ash of acid nature over a long, narrow area 

 in the vicinity of Brisbane. The general direction of the out- 

 crop of this belt of tuff is N.30°W. As far as known, there are 

 no volcanic rocks of undoubted Lower Mesozoic age in South 

 eastern Queensland, with the exception of a series of andesites 

 south of Maryborough, which are apparently interbedded in the 

 Tiaro Series. Marks, Andrews, and Wearne and Woolnough 

 have, at times, advocated a Lower Mesozoic (Trias-Jura) age for 



* Queensland Geol. Surv., Publication 131. 

 t Queensland Geol. Surv., Publication 222, p. 5. 

 X Report Second Interstate Conference on Artesian Water, Brisbane, 

 1914, p.l9. 



