156 



GEOLOGY OP THE GLENDONBROOK DISTRICT, 



(b)Permo-Carboniferous Mocks west of the Elderslee Fault. — 

 The Elderslee fault, with a throw of nearly 6,000 feet to the west, 

 brings the Upper Coal-Measures clown against the Carboniferous 

 rocks, just to the west of Brook's Mountain. In these Upper Coal- 

 Measures, there are a number of coal-seams, which outcrop at inter- 

 vals along Glendon Brook and "Westbrook Creek. The series there 



consists chiefly of interbedded 

 sandstones and conglomerates, 

 with which there are also coal- 

 seams, bands of ironstone, and 

 occasional dolomitic bands. 

 The ironstone is concretion- 

 ary, and the bands vary from 

 1 inch to 15 inches in thick- 

 ness. At the centre of the 

 concretions, there is often a 

 cavity in which quartz-crystals 

 have grown. From the out- 

 crops of the strata, Professor 

 David* has calculated a de- 

 scending vertical section, in 



S ft 



a: isoo- 



I 



I 



Rg. 4. 



Sandstones « 

 conglomerates 



Greta Coal 

 Measures 



Sandstones <* 

 Con<jlomeralts 



Greenish sandstone 



Uiifh Eury<i;sma cordjfj vc 



which there are eighteen coal- 



SMes 

 ^* Hornanof fimeslbttt barui? 



Sandstone with 

 plant remains 



Carboniferous Rocks 



seams varying from 3 to 27 

 feet in thickness. The mea- 

 sures in this part (Westbrook 

 Creek), dip to the east, at an- 

 gles up to about 70°, the very 

 Vertical Section of the Pernio- high angles of dip being at the 

 Carboniferous rocks. extreme west of the occurrence 



of the series. The reason for these steep easterly dips is explained 

 by their occurrence close to the Greta fault, which has a throw, at 

 this point, of some 1,500 feet to the east, and forms the western 

 boundary of these Upper Coal-Measures. Thus the Upper Coal- 

 Measures here occupy an area of subsidence between two heavy 

 faults, i.e., it is a senkungsfeld-area. They do not extend any dis- 



Op. cit., pp. 275-276. 



