154 THE BUILDING OF EASTERN AUSTRALIA 



district, Victoria ; the Mt. Lofty Range, north of Peters- 

 burg, Kangaroo Island, Vincent's Gulf, and thence 

 north to the Queensland border, in South Australia ; and 

 the Kimberley district in Western Auhtralia. These 

 beds are in many places rich in the forms of life character- 

 istic of the period — such as the coral Archseocyathinse ; 

 sponge spicules ; the trilobites Conocephalites, Micro- 

 discus, Olenellus, Dikellocephalus ; the pteropods Salterella 

 and Tentaculites, and the Gastropod Gphileta. 



While the belt referred to was probably the con- 

 tinental shelf and region of heavy sedimentation in 

 Cambrian times, it is probable that the Cambrian ocean 

 extended eastwards over the whole of Eastern Australia. 

 The remarkable crystalline and wholly unfossiliferous 

 rocks, which are known to us as the Brisbane Schists, 

 the Byron Bay Schists and Coff's Harbour Sichists, are 

 probably deep sea deposits of Palaeozoic age, which 

 accumulated in the profound and lifeless ocean during 

 the periods ranging from Cambrian to Devonian. At 

 great depths life would be scarce, and any remains of 

 skeletons of organisms which may have dropped to the 

 bottom would speedily go into solution. 



During the Lower Cambrian period, a glacial age 

 was experiencied in Australia, boulder beds of iceworn 

 nature outcropping in many places on the belt ^of 

 Cambrian sediments, right from Adelaide north to the 

 Queensland-South Australian border, and in the north 

 of Western Australia. [4] 



Ordovician Sedimentation. 

 The region of the heaviest Ordovician Sedimenta- 

 tion lies east of the region of heaviest Cambrian deposition. 

 The latter had been uplifted and largely converted into 

 dry land before the Ordovician period. The continent 

 had therefore taken a step in the direction of the rising 

 sun. A strip, two or three hundred miles wide, lying 

 east of the Cambrian continent, had been converted, 

 into land. [Fig. 3). 



The Ordovician in the Australian region was truly 

 an age of graptolites, which were in many parts, particu- 

 larly in Victoria, buried in such numbers as to give a. 

 graphitic character to the shales and slates of this period. 

 These graphitic shales have acted as precipitants for gold,. 



