REPORTS OF RESEARCH COMMITTEES. 325 



{('..(J., the Marble Range. Mt. Duttoii, Darke's Peak, &c.) above 

 the peneplaiiated surface (3, 5). The present general coastline of 

 the block appears to have been detei'mined by fractui-ing in early 

 •Tertiai-y time, the only marine transgressions being at the Eucla 

 Basin and the narrow coastal basin near Franklin Harbour (1, 3). 



To the eastward of the great pre-Cambrian block, in the north- 

 eastern part of South Australia, lies the gi-eat sediment-filled 

 depression of the Australian Artesian Basin with its Jurassic, 

 Cretaceous, and recent deposits (6). Outlying fragments of 

 the upper beds of this group occur on the margin or tiie pre- 

 Cambrian block, but are not important. Within the limits of the 

 great basin there are residual prominences of pre-Cambrian rocks 

 at the Peak and Denison Ranges (12) which represent islands 

 in the Lower Cretaceous sea. On the western and south-western 

 margin of the basin the drainage systems of to-day have dissected 

 the almost horizontal sandstone which rests uncoiiformably on the 

 Lcwti- Cretaceous shales (6, 9). The lowest parts cf the basin lie 

 along the chain of lakes extending from La,ke Eyre (north and 

 south) through Lakes Gregory, Blanche, and Callabonna, to Lake 

 Fiome (12). 



The South Australian Highlands occupy a position to the east- 

 ward of the great rift which extends northwards from Spencer's 

 Gulf to the head of Lake Torrens. They are built up for the most 

 part of folded and faulted sediments which are deeply dissected 

 (11). The predominant influence that has shaped the land forms 

 within this region is that of faulting and differential uplift, 

 which has greatly modified the central portion of the region and 

 has absolutely determined most of fbs boundaries. 



At very few places the topography is influenced by the effects 

 oi igneous intrusions (7, 17). Traces of a former drainage system 

 are decipherable (2, 16), and the passage of a great glacier across 

 the southern part of the highlands in Permo-Carboniferous time 

 has left an imprint on the land surface that is to be clearly 

 recognised to-day (18). 



An easterly branch of this elevated region extends into New 

 South Wales in the Broken Hill district, and separates the Great 

 Australian Artesian Basin from the Murray River Basin (12). 



Yorke Peninsula is physicgraphically distinct from the highlands 

 on the one hand and from Eyre Peninsula on the other. The 

 basal pre-Cambrian complex, worn down almost to sea-level, has 

 suffered submergence during the deposition of the Cambrian 

 limestone, on which Tertiary limestone rests disconformably (13). 

 A subsequent uplift follo-wed by a recent penoplanation has 

 produced existing contours. The coast-line has been determined 

 by the fractures of the gulf system, and the horizontal Cambrian 

 sediments acquire a pronounced dip on the eastern side of thoi 

 Peninsula (15). 



