AUSTRALASIA, NEW GUINEA, AND NEW ZEALAND 765 



widths so great as to appear as local peneplains, although they are 

 only very broad, shallow valleys in whose bases other broad and 

 shallow valleys have been excavated. The great uplifts of the 

 later Kosciusko period allowed the streams to form profound can- 

 yons which receded along these older shallow valleys. In other 

 words, the main Tertiary land history has consisted of repeated 

 elevations with stream revivals. During one or more of the Ter- 

 tiary divisions of time, particularly in what may be the Miocene, 

 the land appears to have sunk with the formation of lakelike 

 expanses along the stream courses and the burial, later, of deep- 

 river deposits beneath basalt floods covering thousands of square 

 miles in Eastern Australia. This led to great modifications in 

 the stream drainage, but the dominating lesson of the repeated 

 revival of stream action must not be overlooked, the modifica- 

 tions due to lava floods being only an incident in the great 

 geographical unity of Australia in Tertiary and post-Tertiary 

 times. 



New Guinea. — If attention be turned, however, to the north- 

 eastern part of Australia, it will be found that as geological time 

 progressed, the area occupied now in part by New Guinea was built 

 to the south and west. An excellent epitome of the main features 

 of structure known to date has been supplied by Professor T. W. E. 

 David. 1 Schists outcrop at very high altitudes along its northern 

 portion, while strongly folded Cretaceous Strata are reported to occur 

 at the highest altitudes in the north, their steep dips ending abruptly 

 against a high and deeply dissected plateau surface. For 50 or 

 60 miles inland from the south, the area consists of middle and late 

 Tertiary strata, all intensely folded, and all beveled off by a high 

 plain, probably one of submarine erosion. The knowledge of this 

 strong orogenic movement in late or closing Tertiary time and the 

 excavation of a plain of erosion within folded sediments of this age 

 was established by Carne while doing pioneering work in the oil 

 industry. 2 



^'Geology of Papua" (Federal Handbook), Brit. Assoc. Adv. Sci., Australian 

 meeting, 1914, pp. 316-25. 



2 J. E. Carne, Bull, of the Territory of Papua, No. 1, Dept. External Affairs, 

 Melbourne, 1913, pp. 19-29. 



