4 



J. A. PHILLIPS ON THE OCCURRENCE OF REMAINS 



Silica 



Ferric oxide 



Alumina 



Phosphoric anhydride 

 Sulphur 



Water { 



| hygrometric 

 [ combined . , 



•23 



99-80 



It follows that this is a rich ore of iron of fairly good quality ; and 

 as there is now a well-appointed railway in its immediate proximity, 

 it is probable that under moderately favourable conditions of the 

 iron trade it may be worked with advantage. 



During the process of quarrying this ironstone for exportation, 

 Mr. Kennedy first observed the presence of fossil remains of what 

 appeared to be leaves and seeds of many of the plants still growing 

 in the neighbourhood, as well as of several well-preserved beetles. 



All doubt as regards the recent character of these fossils is, how- 

 ever, removed by the following communication fromMr.W.Carruthers, 

 who kindly undertook their examination, and who says, " The speci- 

 mens you have sent me for examination from Rio Tinto contain the 

 following fragments of plants which I have been able to identify : — 

 leaves and acorns of Quercus llecc, Linn. ; leaves and seed of a two- 

 leaved species of Piniis, most probably Pinus Pinea, Linn. ; the cone 

 of Equisetum arvense, Linn. ; and a small branch of a species of Erica. 

 There is also a well-marked leaf of a Dicotyledonous plant which 

 I have not yet been able to identify. The greater portion of two of 

 the specimens consists of a thick growth of moss, but it is impossible 

 to say what the species are. The whole is permeated with minute 

 branching roots, showing that the vegetation was formed as a peat- 

 moss, the oak- and pine-leaves being carried or blown into it. The 

 plants are evidently, all of them, the same species as are still found 

 growing in Spain." 



In addition to these fossils this deposit sometimes contains minute 

 concretionary patches of imperfectly crystallized quartz. 



Every one who examines the section extending from the Cerro 

 Salomon across the valley of the Bio Agrio to the Mesa de los 

 Pinos will probably agree that the origin of this deposit of iron-ore 

 can scarcely be doubtful. At the time of its formation a marsh or 

 shallow lake extended from beyond the last-named point to the foot 

 of Salomon, and into this flowed solutions of iron-salts resulting 

 from the decomposition of the upper portions of the immense masses 

 of pyrites constituting the south lode. 



Erom these salts oxide of iron was deposited, as in the case of 

 bog iron-ores generally ; and, finally, the valley of the Rio Agrio was 

 eroded, as well as that south of the deposit, leaving the Mesa 

 capped with iron-ore, while a small patch of the same mineral 

 was left at the Cerro de las Yacas. 



That the deposit took place at a comparatively recent date is 

 evident from the fossils it contains ; and it is equally certain that the 



