278 C. A. SUSSMILCH AND T. W. E. DAVID. 



Eastern Australia during the Mesozoic Era implies a very 

 considerable extension of the Australian continent over 

 what is now the Tasman Sea during the Mesozoic Era* 



That the Carboniferous epicontinental sea was shallow 

 is indicated (a) by the marine fauna preserved in the Lower 

 Carboniferous strata, which consists mainly of shallow- 

 water species; (b) the presence of occasional beds of con- 

 glomerate interstratified with the marine mudstones, and 

 (c) the oolitic limestones which occur. Throughout the 

 Lower Carboniferous Epoch, the bed of this sea was under- 

 going a slow subsidence, which allowed of the deposition 

 of perhaps 5,000 feet of strata. In the lower part of these 

 sediments, the presence of beds of limestone indicates that 

 the sea over some areas was at times sufficiently free of 

 terrigenous sediments to allow of the accumulation of a 

 moderate thickness of calcareous organic material, particu- 

 larly crinoid stems. 



From the adjoining land, stems and twigs of plants were 

 being washed down by rivers, and as these became water- 

 logged they sank and were preserved in the marine sedi- 

 ments. The abundance of this drift vegetation at some 

 horizons indicates that at times fairly extensive floods took 

 place, an inference supported by the beds of conglomerate 

 which in some cases overlie such deposits. 



Volcanic activity accompanied the Lower Carboniferous 

 sedimentation, a considerable proportion of the strata con- 

 sisting of volcanic ash deposits, and towards the close of 

 the epoch several lava flows were poured out. 



At the close of the Lower Carboniferous Epoch, a very 

 pronounced deformative movement affected the crust in 

 this part of New South Wales, particularly that part of it 

 which lay immediately to the south and west of the area 

 of Lower Carboniferous sedimentation, and possibly that 

 part (Tasmantis) which lay to the north-east may also 



