and Diastrophism in Oceanica. 97 



tinent. The trough began to appear as a sea-way in the 

 Ordovician ( ?5,000 feet of deposits, according to Siissmilch 4 ), 

 with the greatest time of subsidence during the Devonian 

 (27,000 feet) ; it continued with some interruptions through- 

 out the Carboniferous and Permian (36,000 feet). During the 

 Paleozoic, about 70,000 feet of essentially coarse sediments and 

 interbedded volcanics were laid down in New South Wales, 

 though smaller thicknesses seem to prevail elsewhere in eastern 

 Australia. Here again we see the geologic results of high 

 adjacent and often rejuvenated western lands. The record also 

 shows that there were in Paleozoic time at least three periods 

 of decided crustal folding (Ordovician, Silurian, and Devon- 

 ian), and one of vertical uplift with faulting (during the close 

 of Permian time) . 



The marked crustal unrest of eastern Australia is also demon- 

 strated by the vast quantities of extruded volcanics that in the 

 main precede and accompany the deformations, appearing in 

 greatest quantity in the Ordovician, Devonian, and Lower Car- 

 boniferous. According' to Siissmilch, 5 "Nearly every period 

 belonging to the Paleozoic era had its active volcanoes, from 

 which extensive floods of lava were poured out. The Mesozoic 

 era, on the other hand, appears to have been quite free f rom .'. 

 volcanic displays. In the Cenozoic era, renewed activity took 

 place." Following the Permian deformpion the continent was, 

 repeatedly lifted above the embrace' of the Tasman sea. It is i 

 true, however, that the Cretaceous seas have-recorded themselves 

 widely in this continent, but it was a shallow-water flood from 

 the north across medial Australia, ,and to the west of the high 

 eastern margin, a condition. bringing to mind the similar Cam- 

 brian invasion. In the Eocene and Oligocene, the sea again 

 overlapped from the south across a part of central Australia, 

 and most markedly so in the Pliocene, when all of eastern 

 Australia was vertically elevated and block-faulted between : 

 1,500 and 7,300 feet above the level of the sea (during the 

 "Kosciusko epoch"). In compensation for this elevation the 

 Tasman sea sank, there being now great depths close to the 

 continent which in one place go down to 18,500 feet. 



Time of severance of Australia from Asia. — Australasia 

 (Australia, Tasmania, New Guinea) has been the most remark- 

 able asylum among the continents for the preservation to this 

 day of living examples of the plants and animals of the medieval 

 world. Among these in great variety of size, habits, and adap- 



4 C. A. Siissmilch, Geology of New South Wales, 1911. 

 5 Op. cit, p. 161. 



