W.A. PERMO-CARBOXIFEROUS GLACIAL DEPOSITS. 209 



glomerate of the Arthur and the Minilya Rivers. ^ The limestone, 

 which forms a well-marked ridge, to the west of the boulder bed, 

 occupies a considerable area of country in a N.W. and S.E. direction 

 and dips at a comparatively low angle to the south-westward. 

 The debris of the boulder-bed also covers a very wide expanse of 

 country in this latitude. 



The occurrence at Tchugareywurdoo Pool marks the northern 

 limits of this glacial conglomerate in this portion of the State, 

 which has now been proved to extend for a distance of about 200 

 miles between the Lyndon and the Wooramel Rivers (Lats. 23 to 26). 



Fairly full details, illustrated with photographs, sections, and 

 a map, will be found set out in Geol. Surv. Bull., 33, pp. 8 to 23, and 

 need not be repeated. 



Irwin River. — In my presidential address on Recent Advances 

 in the Knowledge of the Geology of Western Australia^, delivered 

 to the Association in Adelaide in 1907, it was pointed out that the 

 carboniferous rocks of the Irwin River Valley contained associated 

 with the Marine Series a boulder bed, the debris of which strewed 

 the surface for a considerable distance, while no ice-scratched 

 boulders had at that time been detected, its glacial origin was 

 suspected. 



The recently completed geological survey of the Irwin River 

 coalfield has added considerably to our knowledge of the Carbon- 

 iferous series, and has resulted in the discovery of a glacial boulder 

 bed of some importance. 



Wherever exposed, the boulders forming the bed consist of a 

 heterogeneous collection of granite, gneiss, quartzite, basic lavas, 

 €tc., many of them being beautifully glaciated. 



The debris of the boulder bed occurs more or less regularly along 

 a general N.W. direction over the whole area of the coallieid, and 

 marks a very important geological horizon, extending for about 

 twenty-four miles along the surface. 



This Irwin River boulder bed does not appear to be exactly at 

 the base of the Carboniferous series as developed in this latitude, 

 and is in all probabihty the southern extension of that occurring 

 in the valleys of the Lyndon, Lyons, Gascoyne and Wooramel 

 Rivers, which are described in Bull., 33, q.v. 



The Carboniferous rocks of the Irwin River Valley do not 

 occupy any very large area, but are covered by a considerable 

 thickness of Jurassic rocks, which dip generally to the southward. 



Full details of these glacial deposits and associated rocks, 

 illustrated by geological maps, sections and photographs, will be 

 found in Geol. Stir. Bull., 38, and hardly need repetition. 



1 Geol. Surv. Bull. 33, Perth, 1909, pp. 8-22. 



2.Austr. Assoc. Adv. Set., 11th meeting, .\delaide, 1907, p. 1-16. 



