TRANSACTIONS OF SECTION E. 655 



5. Present Trias Conditions in Australia. By Rev. E. C. Spicer, 



M.A., F.G.S, 



Trixssic conditions in England resulted in (1) the jagged outline of the peaks 

 visible above the 'buried landscape' of Charnwood Forest which were thus 

 modified during their exposure in Trias times; (2) the formation of the ' Bunter 

 pebble bed ' ; (3) the thick deposits of wind-bedded Trias sandstones ; (4) the 

 Keuper marls; (5) the salt deposits; (6) the poor fauna and flora; (7) footprints 

 and burst viscid bubbles ('raindrops'). 



Flinders Range in South Australia is modified into rounded outlines in the 

 south, where there is a fair amount of regular rainfall. In the northern part 

 of the range, beyond the influence of the southern cyclonic system, the range 

 becomes (1) jagged in character. 



(2) During some years there is no rain at all. When a drought breaks up 

 there is usually a ' deluge ' of two or three inches, sometimes falling in twenty- 

 four hours, accompanied by heavy thunder. The only outlet from the range-mass 

 is through gorges five miles apart opening on to the Great Western Plain. A great 

 wall of water rushes furiously through these gorges, pushing a mass of boulders 

 and grace! bodily downwards, gradually wearing the hard materials down and 

 spreading them in great sheets over the plain. 



(3) In the long dry summers and in drought seasons the Great Western Plain is 

 covered by a mass of moving sand, driven in great clouds by the rare high winds 

 and constantly drifting over the plain. 



(4) Around Lake Torrens and inland the surface is more compact and of a 

 marly character. 



(5) Lake Torrens is flooded during the rain-storm periods. As the lake water 

 evaporates the marshy border dries up, and there are great areas of coarsely 

 crystallised salt. 



(6) The plain below Flinders Eange is almost destitute of life, with the 

 exception of a few birds and reptiles. All the animals that cannot escape to 

 trees are drowned when the floods occur. 



(7) The drying muds receive the impression of emu tracks; the drifting sands 

 blow over these and preserve them, while the decaying drifted vegetation pro- 

 duces gas bubbles in the viscid mud, which is also covered by drifting sand. 



Thus the northern part of the Flinders Range area and the Great Western 

 Plain region extending to Lake Torrens reproduce Trias conditions at the present 

 time. 



The following Paper was read in Section E : — 



Notes on a Journey through South America from Bogota to Mandos via 

 the River Vawpes. By Hamilton Rice, B.A., M.D. 



The author spoke of the march from Bogota to Villa vicencio by passage of the 

 Andes and across the ' llanos ' to San Martin, the cattle centre of S.E. Columbia 

 and last outpost of municipal control. 



The ' tierra caliente ' and beginning of the densely forested Amazonian area 

 marked by the watershed of the Meta and Guaviare rivers, big western tributaries 

 of the Orinoco, just to the south of which region the sources of the Uaupes 

 originate. 



The rher's extent and geological character of the country through which it 

 flows.— In the western portion the rock masses and hills are of lacolithic structure, 

 as evidenced by their scoriaceous and pyroclastic appearance, which attests a vary 

 rapid cooling from the original frothy and viscid condition. In the eastern part 

 of )ts course the rocks forming its rapids and composing the discrete dome shaped 

 and sugar-loaf forms of hills are granitic in character, and the river banks are 

 formed of coarse or fine sand instead of the soft unctuous-like mottled-clay found 

 everywhere above. 



From any eyrie where far-reaching areas may be discerned the terrain presents 

 a surface of undulating or crumpled unevenness, suggestive of a process of uplift 

 having ensued in conjunction with, or as complementary to, the violent volcanic 

 cataclysms of a former period. 



The aborigines, or so-called Indians, inhabiting its banks, of Tupi-Guarani 



v v 2 



