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THE AGRICULTURAL JOURNAL. 



Coast Geofagym 



THE following geological observations of 

 Mr. William Anderson, geologist, on 

 tlie formation of the Bluff, Durban, and 

 the adjacent country, are published by 

 order : — 



Geographical Survey, 



J^urvej'or General's Office, 

 Pietermaritzburg, Natal, 



June i2th, 1901. 



J. L. Masson, Esq., 



Surveyor-General. 



Sir, — I have the honour to furnish you 

 with a geological report on papers (L & W 

 Hij) dealing with the prospects of obtain- 

 ing payable coal under the Bluff, Durban 



The country around Durban harbour 

 from the Umgeni to the Umlaas River, 

 with a few local exceptions, is covered to 

 a considersble depth with Pleistocene and 

 Recent sands and clays. There are, there- 

 fore, few outcrops of rock to be seen. At 

 the Umgeni Bi-idge the Dwyka, a con- 

 glomerate, outcrops at the surface, and is 

 worked at the Corporation Quarries. The 

 next outcrop of rock that I know of is at 

 Congella, where black carbonaceous shales, 

 with intrusive basalt occur close to the 

 railway line. On this outcrop a bore was 

 put down by Mr. Jonsson, to a depth of 

 over 300ft. Mr. J. Goodricke has kindly 

 furnished me with information relative 

 to this bore and the others in the neigh- 

 bourhood put down by him. The rocks 

 passed through were dark carbonaceous 

 shales, with occasional intrusive sills of 

 basalt. At some depth an artesian mineral 

 water was struck, which still overflows 

 from the bore. 



Further to the south, at Clairmont 

 quarry, the Palseoroic sandstones occur. 

 Some time ago, a bore was put down, on 

 the fiat, to the south-east of the quarry, to 

 a depth of 150 feet. This bore passed 

 through basaltic rock (not felsite as re- 

 corded in the Mines report for 1892), and 

 sandstone, which is, undoubtedly the 

 Palajoroic sandstone of the quarry. These 

 sandstones are older than the Dwyka con- 

 glomerate, which rests unconformal)ly 

 upon them, and their presence is, there- 

 fore, significant in curtailing the area 

 occupied by the conglomerate and Ecca 

 series which usually overlie it. 



About a mile to the north of the cross- 

 ing of the Umlaas river, the Dwyka con- 

 glomerate crops out on the road. The 

 ridge known as the Berea is composed of 

 the same rock, which, however, does not 

 often show at the surface, as it is covered 

 with a good depth of sand. 



In the outcrops of these rocks, the 

 Dwyka conglomerate at Umgeni quarry, 

 the same rock forming the Berea, the 

 Palfeoroic sandstones at Clairmont, and 

 the Dwyka conglomerate at the Umlaas 

 river, we have, roughly, the boundary of 

 the Ecca series, landwards. The shales 

 which crop out at ihe Congella bore have 

 a hardly appreciable dip, to the eastward, 

 and therefore, in their projection, they 

 pass under the alluvial deposits of the 

 Bay. 



The Ecca series, as it is exposed in the 

 Umhlali district of the north coast and in 

 the coalfields of Zululand, have invariably 

 the same succession, that is, a series of 

 black shales, generally carbonaceous, rest- 

 ing, usually with a slight unconformity, 

 on the Dwyka conglomerate. These are 

 succeeded by a less thickness of light 

 grey-coloured shales, and they, in their 

 turn, by the coal-bearing series of sand- 

 stones and shales with thin coals. There 

 is no break in the succession of strata 

 from the Dwyka conglomerate up 

 through the shales to the coal-bearing 

 portion of the Ecca series, with the ex- 

 ception of the slight uuconformity im- 

 mediately above the glacial conglomerate. 



In the Durban area we get the basal 

 conglomerate, and in the Congella bore, 

 over 300 feet of black carbonaceous shales, 

 which are undoubtedly the representa- 

 tives of the black shales overlying the 

 the Dwyka conglomerate in the areas 

 mentioned above at Umhlali and in Zulu- 

 sand. The overlying and upper portion 

 of the Ecca series, comprising the light 

 shales and the coal-bearing series of sand- 

 stones and shales, are not anywhere ex- 

 posed in the Durban area, if they exist 

 there, owing to the large quantities of 

 Pleistocene and Recent alluvials which 

 cover the surface. 



The distribution of the Ecca series 

 along the coast of Natal is as follows : — 

 Between Port Shepstone and Isipingo out- 



