200 



by the Maitland No. 1 Bore (see page 202), and from the fol- 

 lowing analysis, kindly undertaken by Mr. W. S. Chapman, 

 of the Adelaide School of Mines, it is shown to be a true 

 dolomite : — 



Per cent. 

 Insoluble matter 0*88 



Ferric oxide 



Alumina 



Calcium carbonate ... 

 Magnesium carbonate 



0-67 



0-45 



54-10 



43-51 



99-61 



This is the most widely distributed member of the Cam- 

 brian limestones throughout the district (the newer beds 

 having aparently been removed by denudation), and pre- 

 serves a general uniformity of chemical and physical char- 

 acteristics in all its exposures. The following are the chief 

 localities where its outcrops can be seen: — 



1. Eastern Scarp of Coastal Ridge. A low range with 

 its scarp facing the sea is continuous from Horse Gully to 

 Ardrossan. The dolomitic rock rises from beneath the 

 marble on the northern side of Horse Gully, and has been 

 quarried on Cliff's farm (formerly Mrs. Naughton's land), 

 almost in a direct line with Parara Head Station. It is here 

 a white, crystalline dolomite, with a dip west at 38°, and a 

 little further to the westward the dip changes to the south- 

 west at 19°. Excellent exposures are seen in a small trans- 

 verse gully, about half a mile to the northward of the quarry 

 just referred to, whexe the stone is a yellowish, granular 

 dolomite (penetrated by ferro-manganese stains), with a dip 

 of 35° facing 40° east of south. In the next gully, a little 

 further to the northward, the beds have a south-westerly dip 

 at 30°, and continue in outcrop along the slopes of the ridge, 

 until they cross the Maitland road, and disappear from sight 

 on the western side of the Ardrossan Cemetery. 



2. Rogues Gully. Situated 2 J miles to the southward of 

 Horse Gully and about 6 miles from Ardrossan. Deep gul- 

 lies, now permanently dry, have been excavated in the 

 dolomite beds, but as the country is covered by dense scrub 

 it is unfavourable for geological observations. The hillsides 

 are covered with surface rubble, but no large faces of stone 

 are exposed, and consequently no reading of dip could be 

 taken. The stone is saccharoidal in texture, grey or yel- 

 lowish in colour, and at surface often soft through partial 

 decomposition. The base of the beds is not exposed, but as 

 they occupy the whole of the main and lateral gullies to the 

 top of the adjoining heights, their thickness is estimated at 

 not less than 100 feet. 



