844 THE GEOLOGY OF THE NANDEWAR MOUNTAINS, 



south to Couradda (Grattai) Mountain on the north, and from 

 Noogera Creek on the east to the 1,000-feet contour on the west. 



(e) Tuffs allied to the lavas in (d). 



(f) Felspar porphyrites with labradorite phenocrysts exceeding 

 in some case two inches in length and |-in. in thickness. 

 This porphyrite occurs in sills associated with ^egirine syenite 

 sills which contain inclusions of fine-grained nepheline phonolite 

 (vide Petrological Notes, N.12, N.ll, and N.IO). 



(g) Porphyritic basalt with labradorite phenocrysts exceeding 

 two inches in length. 



(h) Lamprophyric porphyrite occurring as a sill at Dingo 

 Creek. This rock has huge phenocrysts of rhombic pyroxene, 

 some of which are from three to four inches long. 



(i) Basalts capping the other lavas. Some of the basalts 

 contain no olivine and resemble closely that from the Sandilands 

 Ranges. The last erupted contain olivine. 



(j) Tertiary C?) rhyolites and rhyolitic tuffs to the S.W. of the 

 Nandewars between Maule's Creek and Bosfgabri. The.'-e rocks 

 form cones and necks, and exist also to the west of Boggabri. 



(k) Quartz porphyries and old rhyolites associated with tuffs 

 and breccias at the head of Oakey Creek, Coolah, and between 

 Maule's Creek and Barraba. These rocks appear to be of 

 Carboniferous age. 



Alluvials and Windbloiun Deposits. — (a) Black Soil Plains, as 

 at Narrabri, occurring far and wide with interspersed sandy 

 patches on the plains. The black soils are usually of river 

 deposition, and are often of great depth. The alluvials and 

 Tertiary deposits at Narrabri attain a thickness of over 1,000 feet. 



(b) Poor sandy pine scrubs of the Pillaga type. The edge of 

 Pillaga scrub is encountered on the Narrabri-Boggabri Road 

 about 11-12 miles south of Narrabri (near Turrawan). 



3. Geomorphology (including Physiography, Topography and 

 Descriptive Geology). 



To illustrate this part I have prepared two sketch maps, one 

 of the Nandewar INIountains and Nandewar Range, including 



