THE BRISBANE SCHISTS. 125 



Every geologist who has visited Brisbane has commented on 

 the highly distorted schists that form the main geological feature 

 of the environment of that city. 



Hitherto these schists have been officially classed as Permo- 

 carbonifercais, and said to belong to the Gympie series. 



My object in writing this short note is to give, at least, food 

 for discussion which may bring forth evidence in support of the 

 theory that the Brisbane schists belong to a much older period than 

 Permo-carboniferous. I have carefully examined these rocks on 

 the western flanks of the southern portion of the D'Aguilar Range 

 and along their junction with the Ipswich Coal Measures between 

 Brisbane and Fernvale, a sm:,ll township on the Brisbane \'alley 

 railway line, 16 miles from Ipswich. 



There is no positive evidence to determine their age, but from 

 the following data I am of opinion that some at least of these schists 

 are possibly Pre-Cambrian : — 



1. — In iithological character they resemble some of the Pre- 

 cambrian rocks of South Australia. The whole series has been 

 completely metamorphosed and some intrusive igneous rocks have 

 been rendered completely schistose in character. 



The chief rock types met with are mich-schist, quartz-schist, 

 quartzite, dolomite, serpentine, amphibolite, etc. 



2. — A marked uniformity exists between the Brisbane schists 

 and the Ipiswich Trias- Jura coal measures. 



At Fernvale, a fine section has been revealed by a creek about 

 I mile from the railway station. Here the schists dip at an angle 

 of 80°, while the coal measures are practically horizontal. 



3. — Absence of Fossils. — The true Gympie beds contain a plenti- 

 ful supf^ly of marine Permo-carboniferous fossils, whereas the 

 Brisbane schists have been found to be entirely barren despite the 

 fact that numerous deep railway cuttings have been made through 

 them. 



While investigating the alkaline eruptives near Mt. Barney, a 

 few miles to the north of Mt. Lindsay on the New South Wales 

 border, I came across a sandstone ridge in which I found a well 

 defined fossil of Fenesiella. It was referred to Mr. W'. S. Dun for 

 determination, and he states the area undoubtedly belongs to the 

 Permo-carboniferous. Now, if the rocks belonging to this period 

 are quite undisturbed and retain their fossil imprints so clearly 

 despite the volcanic agencies that have played such an important 

 part in forming the topography of this district, it is only reasonable 

 to suppose that the Brisbane schists if of Permo-carboniferous age 

 would, at least, retain their finger prints in areas free from volcanic 

 or plutonic intrusions. 



I admit the evidence deduced is negative and far from con- 

 clusive, but I trust the subject will receive more detailed attention 

 in the near future. 



