243 



Dauphin on the west, to Mira bay on the east. The area 

 occupied by these measures amounts to about 300 square 

 miles (780 sq. km.) of which total about 50 square miles 

 (130 sq. km.) is underlain by the Productive Coal Measures. 

 In addition to the land area of the Productive Coal Mea- 

 sures, there is, by reason of the low seaward dip of the 

 strata, a very considerable submarine area from which 

 coal may be won. 



The Sydney Carboniferous basin is notable for the 

 splendid sections exposed along the coast and for the great 

 thickness of the strata, which, in the vicinity of Sydney 

 harbour, reaches approximately 12,600 feet (3,840 m.). The 

 section is characterized by the apparent absence of pro- 

 nounced stratigraphical breaks. In general, the geological 

 structure is simple in form, the angles of dip low, and 

 although a few prominent faults occur, the greater part of 

 the field is free from them. 



By reason of a series of low folds and certain indenta- 

 tions of the coast, the coal field is naturally divisible into 

 six coal basins or districts. All of these with but one excep- 

 tion, contain, besides a number of minor seams, 5 to 8 

 seams of coal varying from 2 feet (o-6 m.) to 13 feet 

 (3-9 m.) in thickness. The total thickness of coal in seams 

 that may be workable varies in the five main basins from 

 23 feet (7 m.) up to 47 feet (14-3 m.). The coal is of a 

 bituminous variety and in 191 1 the total production 

 amounted to above 4,900,000 tons. The individual 

 seams are traceable for miles along the strike, in fact many 

 of them are believed to extend throughout the whole 

 length of the field. The individual seams vary somewhat 

 in quality along the strike, change in thickness in a rather 

 remarkable manner, and in some cases what is one seam 

 in one locality becomes two in another because of the 

 greatly increased thickness of an elsewhere relatively 

 insignificant parting. 



The fund of general geological information concerning 

 the Sydney Carboniferous area is contained, almost entirely, 

 in early reports by Charles Robb, and Hugh Fletcher, 

 published by the Geological Survey in the '70s. and in a 

 series of maps by Fletcher which are, in part, revisions of 

 earlier editions. Important contributions to the geology 

 of the district were made by Richard Brown at one time 

 manager of a coal company operating in the field. The 

 varied and striking palseobotanical material described by 

 35063— 3^A 



