BY H. I. JENSEN. 861 



north and south by mesas several miles removed from the creek. 

 This Maule's Creek plain marks an area of undoubted Permo- 

 Carboniferous age. It is well-grassed and timbered, box trees, 

 an indication of good soil, being abundant. The mesas north and 

 south of it are probably chiefly of Upper Permo-Carboniferous 

 age, but of Trias-Jura age in places, especially between Black 

 Mountain and Deriah. The sandstones of the mesas are com- 

 posed chiefly of quartz sand and the conglomerates of quartz 

 pebbles, and the vegetation is very poor. The Lower Permo- 

 Carboniferous sandstones and conglomerates give a much better 

 soil, containing much felspar of rhyolitic origin. 



In the gorge above its junction with Buron Creek, Maule's 

 Creek has cut through a series of conglomerates composed of 

 rhyolite pebbles like those of Berrioye, but having, nevertheless, 

 a totally different appearance — being, in fact, boulder beds, con- 

 taining boulders up to two feet in diameter. They are chiefly 

 tilted in places and exceed 1,000 feet in thickness. On the 

 Government Geological Map this area is put down as Carbo- 

 niferous, an estimate which appears to me to be correct. 

 Mount Byar and Mount Coolah are composed of massive 

 conglomerates with interbedded sheets of tuff and rhyolite 

 (quartz porphyry), the pebbles of the conglomerate being 

 identical in nature with the interbedded sheets. Above Coolah 

 Station on INIaule's Creek and its branch, Oakey Creek, similar 

 rocks occur, but near Waterloo Pinnacle cherts and slates are 

 met with in the hill-slopes. They are highly metamorphic, and 

 sills or dykes of orthoclase quartz porphyry intrude them. They 

 are probably Devonian, and the whole series here seems to dip 

 E. at 20°. 



The rocks of Byar and Coolah Mountains on the other hand 

 have a N.W. dip at angles up to 20*^. The Pinnacles, a couple 

 of peaks north of Coolah, are remarkable for being as rugged 

 and precipitous as trachyte plugs, I went to them expecting to 

 find them composed of trachyte, but to my astonishment they 

 consisted of Carboniferous conglomerate similar to Byar Moun- 

 tain, dipping N.W. at 20°. The dips around Coolah Station are 



