306 



THE AOBICULTURAL JOURNAL. 



At Sydney, the geological structure is 

 a simple isynclinal trough consisting of 

 the Hawkesbury sandstones (Triassic) 

 overlying, with the intervention of the 

 Narrabeen shales, the coal-bearing Permo- 

 carboniferous series, which outcrops on 

 the surface, at the edges of the trough, to 

 the north in the Newcastle district, and 

 to the south in the Illawarra district. 

 For a number of years special attention 

 was given by the Geological Survey to the 

 geological examination of these outcrops, 

 which are separated from one another by 

 100 miles of country, over which the 

 Hawkesbury sandstone is the surface 

 rock. The various coal seams in the 

 southern outcrop were ultimately correl- 

 ated with similar beds in the northern 

 coalfield, chiefly by means of palaeonto- 

 logical evidence, with the result that the 

 beds forming the two outcrops were 

 proved to be portions of the same series 

 of strata, and therefore of the same age. 

 The inference drawn from this know- 

 ledge, together with the stratigraphical 

 evidence as to the geological structure, 

 disposition and relations of the Hawkes- 

 bury sandstones to the coal-bearing series, 

 was that there was a great probability of the 

 coal-bearing series persisting in a trough- 

 like form, underneath the Hawkesbury 

 sandstones and Narrabeen shales. This 

 would mean that the beds outcropping in 

 the Newcastle district were continuous 

 under the Hawkesbury and Narrabeen 

 shales with those which outcrop in the 

 niawarra district. The result of this con- 

 clusion was the putting down of a bore 

 on Sydney harbour, which was successful 

 in striking the coal-measures within a 

 very short distance of the depth at which 

 Professor David, then of the Geological 

 Survey, computed they would be found. 



In conclusion, 1 would state, that there 

 is little doubt of the presence of the Ecca 

 series below the calcareous sandstones of 

 the Bluff, and it is possible that there may 



be thin coal seams among them, just as 

 there are on the coast at Umhlali, but the 

 question as to the occurrence of payable 

 coal is very problemaxical. If the series 

 keeps the low dip to the east, which it has 

 at the Congella bore, across the Bay to the 

 Bluff, a distance of about three miles, 

 there is certainly not much room for the 

 coming in of any thicknass of beds, higher 

 in the series than those at the bore, which 

 is undoubtedly sunk in the black shales 

 immediately overlying the Dwyka con- 

 glomerate. A persistent dip of 3'^, with- 

 out the intervention of faulting or other 

 displacement of the strata, would allow 

 of a little over 800 feet of beds being 

 brought in, from sea level at the Bluff, 

 down to the horizon of the shales at the 

 top of the Congella bore. There is no 

 evidence to prove at what depth from 

 the surface the unconformity between the 

 Bluff sandstones and the Ecca series 

 occurs. The deeper this is, the less 

 will the thickness of the Ecca beds be. 

 If the dip alters and assumes a high angle, 

 then there would be a probability ot 

 getting the coal-bearing series of the 

 Eccas under the Bluff. The same would 

 result by the intervention of faulting with 

 a down throw from the eastward, but 

 iudging from the districts in which 1 

 have seen the Ecca coal-bearing series, 

 faulting to any extent is very rare. As i 

 have previously stated, the prospects ot 

 obtaining payable coal under the Blutt 

 are not of an encouraging nature. 



The sections attached explain them- 

 selves ; No. 2 is a section from the Berea, 

 across the Bay to the Bluff, showing the 

 geological structure as I interpret it. 



I have the honour to be, 

 Sir, 



Your obedient servant, 



William Anderson, 

 Government Geologist 



HOW TO IMPROVE THE " JOURNAL." 



SIK _I wish, in this short article, to 

 emphasize the sensible letter in your 

 iournal of the 5th instant, by Mr. Geo. 

 J Wood. If our farming " Members " 



Correspondence^ 



To the Editor Agricultural Journal. 



would encourage the Journal, instead of 

 crying it down, our agricultural know- 

 ledge would probably increase m a like 

 ratio Truly, Mr. Wood proclaimed » 

 melancholy fact when he wrote, " Farmer. 



