195 



clay is probably the decomposed covering whicli formed the 

 Pre-Cambrian floor on which the basal grits were laid down. 



9. Maitland. The Maitland No. 1 Bor>e, put down 

 about a mile from the township on its western side, proved 

 the basal grits at that place to have a thickness of 51 feet 

 (see page 202). 



10. Yorke Valley, Western Ridge. About 5 to 6 miles 

 to the southward of Maitland there is an interesting series 

 of outcrops of the Cambrian rocks along this ridge. The top 

 of the ridge shows outcrops of the basal grits which have 

 been quarried for building stones in Section 16 (Hundred of 

 Maitland) and other places. It was followed in a con- 

 tinuous outcrop through the properties of Messrs. William 

 Greenslade, Joseph Kelly, and A. W. Jarrett, in Sections 1, 

 16, 19w, 19e, etc. Within the area mentioned the granite 

 is seen to underlie the grits on the one side, and the Cam- 

 brian limestones to overlie them on the other. 



11. Henderson's Quarry. I am indebted to the Rev. J. 

 R. Andrew for the information that a quarry (owned by 

 Mr. Henderson), in the basal grits, occurs on the north side 

 of Section 53, Hundred of Muloowurtie, about 3 miles due 

 west from Rogues Point. The Pre-Cambrian igneous rocks 

 occur a little to the south of this quarry. 



12. Port Hughes. In October, 1905, a visit was paid 

 to Port Hughes, near Moonta, where the basal grits of the 

 Cambrian series were seen to outcrop on the beach, and the 

 following observations were made. The beds consist of coarse 

 conglomerates and silicious gritty quartzites. The included 

 pebbles consist almost entirely of quartz, much worn and 

 rounded, and the beds generally closely resemble the basal 

 grits as they occur at Winulta Creek. In certain zones the 

 rock has been much fractured and the cracks subsequently 

 filled with quartz, forming veins that intersect the matrix 

 and pebbles without distinction. (Dip N". 20° W. at 

 12°). (4) 



Limestones. 



The Cambrian limestones (in common with the other 

 geological outcrops) of Yorke Peninsula make n.o very 

 prominent features in the landscape and give only limited 

 sections at the surface; it is, therefore, somewhat difficult 

 to obtain an unquestionable order of succession for the 

 respective members of the series. This defect is, in part, 



(4) For further geological information on this part of Yorke 

 Peninsula see the comprehensive and detailed descriptions given 

 by the Assistant Government Geologist (Mr. R. Loekhart Jack) in 

 The Geology of the Moonta and Wallaroo Mining District, Bull. 

 No. 6, Department of Mines, 1917. 

 h2 



