249 



some as evidence of a fault striking along the southeast side 

 of the hills and it has been held that this fault continues to 

 the northeast through the Carboniferous basin, perhaps 

 along the winding, river-like channel of the Little Bras 

 d'Or. No direct evidence has been produced of the exist- 

 ence of such a fault and it seems more probable that the 

 structure is due to overlapping and not to faulting. 



The next anticlinal axis passes through Point Edward at 

 the extremity of the projection separating the two arms 

 of Sydney harbour. In a southwest direction, the course 

 of this axis is indicated by the zone of the Conglomerate 

 series lapping around the Pre-Cambrian strata of the 

 Coxheath hills. Towards the northeast, beyond Point 

 Edward, the anticlinal axis follows a course that swings to 

 the E.N.E. and passes beneath the waters of Bridgeport 

 basin. A fault has been described by Fletcher as extending 

 southwestward up the valley of Sydney river on the south 

 side of Coxheath hills. This fault in the neighbourhood of 

 the town of Sydney has been supposed to abruptly change 

 its direction and to run thence with a southeasterly course 

 forming the northern boundary of a subordinate synclinal 

 basin of strata mapped as Millstone Grit but which on 

 palaeobotanical grounds was considered by Dawson as 

 possibly of the age of the Productive Measures. 



Farther eastward, an anticlinal axis strikes inland from 

 Cape Percy (North Head) with a W.S.W. course. This 

 anticline apparently dies away inland. It is followed on 

 the south by the synclinal basin of Cow bay which also dies 

 away inland. 



The southern margin of the western portion of the field 

 when represented in plan on a map, indicates very clearly 

 the position of the anticlinal axes of the Coxheath, Boisdale 

 and Ste. Anne hills — the Carboniferous projecting south- 

 westward in the form of synclinal basins between the axial 

 areas of Pre-Cambrian strata. Towards the east, the 

 basin-like structure is not so strikingly exhibited and the 

 south boundary is formed by Millstone Grit strata resting 

 directly on Cambrian and Pre-Cambrian beds except in 

 the extreme east where beds of the Limestone series form 

 the basement and are separated by faults from the Mill- 

 stone Grit measures. 



