112 GEOLOGY OF LOWER MESOZOIC HOCKS OF QUEENSLAND, 



in which freshwater deposits were laid down, increased enor- 

 mously. The early Cretaceous period saw very great changes in 

 distribution of land and ^vater. The sea transgressed from the 

 north in the region of the Gulf of Carpentaria, at least as far as 

 Lake Eyre; Australia appears to have been divided into two 

 parts, either by the extension of this transgression to the south- 

 west, or by meeting another from the south-west. These suc- 

 cessive changes are shown on Text-figs. 3-6. 



Summary. 



The Lower Mesozoic rocks of Queensland comprise three di^■i- 

 sions, namely, the Ipswich, Bundamba, and Walloon Series, The 

 Ipswich and Bundamba Series are of comparatively limited dis- 

 tribution, and are confined to the south-eastern portion of the 

 State. The Walloon Series has a much greater extent; in addi- 

 tion to occurring in South-eastern Queensland, in association with 

 the Ipswich and Bundamba Series, it outcrops in a belt along 

 the western slope of the Main Divide from the New South Wales 

 border to Cape York, dipping westerly beneath the marine Cre- 

 taceous. It probably underlies the Cretaceous strata over the 

 greater part of Western Queensland. In Eastern Queensland, 

 there are a number of small, isolated occurrences of the Walloon 

 Series, as indicated on Plate i. The thicknesses of the three series 

 are approximately as follows: Ipswich Series, 2,000-2,500 feet; 

 Bundamba Series, 3,000-5,000 feet; and Walloon Series, up to 

 10,000 feet. 



From an economic point of view, the Lower Mesozoic rocks 

 are of special importance in three respects, namely, (1) the greater 

 part of the coal produced in Queensland is from the coal-measures 

 of the Ipswich and Walloon Series, chiefly the former; (2\ the 

 large supplies of artesian water are obtained from sandstones 

 which are the equivalents of the Walloon Series in Western 

 Queensland; (3) practically all the Queensland sandstone used 

 for building purposes is of Lower Mesozoic age. 



In South-eastern Queensland, the Lower Mesozoic rocks (and 

 also the Cretaceous strata) have been folded into a series of anti- 



