276 GREAT SERPEXTINE-BKLT OF NEW SOUTH WALES, Vl., 



Tertiary clays and gravels occur. Following to the west, along 

 the basalt-capping of the Nandewar Range, the elevation steadily 

 rises. About four miles west of Bell's Mountain, the underlying 

 Tertiary drift reaches a considerable width. Mr. Pittman has 

 described it (47) as follows — "The deposit, which is probably of 

 late Tertiary age and of lacustrine origin, apparently occupies a 

 denuded hollow in the Carboniferous rocks [here considered 

 Upper Devonian (W. N.B.)], for the latter containing impressions 

 of Lejyidodendron australe are seen to outcrop around its margin. 

 The lowest beds of the Tertiary series consist of yellowish-grey 

 sandstones and shales with numerous impressions of Eucalyj)tus 

 and other plant-remains; above this is a volcanic tuff consisting 

 of impure diatomaceous earth, with rounded pebbles, sanidine 

 crystals and fragments of pumice. In some places the tuff is 

 very much impregnated with ferric oxide forming a hard 

 limonite. It is succeeded by a bed of yellowish-brown sandy 

 mudstone, about a foot in thickness, and resting upon this is 

 the bed of pure white diatomaceous earth, nine feet six inches 

 in thickness, with a layer of two inches of coarse sand about 

 three feet from the top. Another bed of volcanic tuff contain- 

 ing numerous sanidine crystals covers the keiselguhr, and is 

 overlain by about 100 feet of basalt. The sedimentary beds 



undulate considerably, and it is difficult to estimate their 



thickness." Messrs. Card and Dun have found Melosira and 

 Spofigilla in abundance in the diatomaceous earth (29). 



Tertiary drift appears again beneath the basalt at the head of 

 Oakey Creek, and, at the Horton Gap, the basalt has been cut 

 through, exposing a thickness of 50 feet of Tertiary drift, fol- 

 lowed by about 100 feet of basalt, the surface of which is at an 

 elevation of 2,450* feet. Five miles south-west of here, at the 

 head of Little Creek, the top of the basalt is at an elevation of 

 2,510 feet. Across the Horton River, is the long line of basalt, 

 which runs east of the Nandewar Mountains, and is repoi'ted to 

 overlie gravels (19); this may well be a continuation of the 

 old river marked by the Nandewar Range. If so, a length of 



" This figure is hased on a single reading of the aneroid, and is, perliaps, 

 lathei- too hiirli. 



