184 PROCEEDINGS OF SECTION C. 



As one invariably finds in Queensland an unconformable passage 

 from the Lower Cretaceous (KoUing Downs) to the Upper Cretaceons 

 (Desert Sandstone), it seems safe to assume that these freshwater 

 beds are of Lower Cretaceous age. 



Recent Conglomerates. — About midway between Jenkins Point 

 and South Point, on the N.E. side of the island, there occurs along the 

 shore-line a coarse conglomerate made up of rounded pebbles of chert, 

 which have been cemented together by a ferruginous material. The 

 chert fragments have in all probability been derived from the cliffs 

 of chert above the shore-line. On the S.W. side of the island the 

 beach gravel previously referred to has also been cemented together 

 by a ferruginous cement, and converted into a rather finer conglomerate, 

 which might well be described as a pudding-stone for the most part. 



Recent Breccia. — Here and there along the base of the cliffs on the 

 N.W. side of the island, and particularly at the northern end of it, 

 there occurs a thin band of breccia made up of angular fragments of 

 chert cemented with a ferruginous material. At Datum Point the 

 cliffs are capped with a fairly considerable thickness of this. 



Recent Limestone. — On the N.W. side of the island, round from 

 Datum Point, there occurs recent limestone formed of loosely aggre- 

 gated beach material. Small cliffs of this material up to 12 feet high 

 occur, and a semicircular coastal strip of it several acres in extent 

 and about 10 feet above high-water mark exists. 



Picnic Island and Duck Islands. — These three islands are very 

 similar in character and only the largest and most southerly one will 

 be described. 



This island is composed of rocks entirely of a marine origin, and 

 consists for the most part of cherts which have been formed from the 

 raetasomatic replacement of shales of a bluish-grey colour. On this 

 island all the changes from the unaltered shale to the final chert may 

 be seen. 



The strike of the strata is 40° W. of N., while the dip is generally 

 about 35°, direction 50° W. of S. The dip at the southern end of the 

 island was somewhat more steep than that in the other parts. The 

 shales are particularly rich in traces of a marine fauna, Belemnites, 

 NuGula, and Maccoyella being common. The shells are preserved as 

 calcium carbonate in the shales, and this is in marked contrast to the 

 preservation of casts only in the cherts. 



The characteristic bluish-grey colour of the chert throughout the 

 area is just the same colour as the shales of this island possess, and in this 

 locality one can trace the passage from shale to chert. There is, then, 

 little doubt that the cherts of the area have been derived from meta- 

 somatic replacement of the shales. 



The lithological characters of these rocks and their strike correspond 

 with those of Woody Island, also these islands are in the line of strike 

 of the similar beds on Woody Island. 



