492 THE CONTINENTAL ORIGIN OF FIJI, 



An alternative hypothesis is that the area may ha\e been one 

 of continual elevation, denudation about keeping pace with the 

 uplift. In this way various marine formations would be laid 

 down throughout geological time, but as (juickly as they were 

 raised above sea-level they were denuded and so no trace of them 

 left. Then a subsidence took place early in Tertiary time which 

 permitted the formation of the various marine Tertiaries. Within 

 recent times uplifts have taken place as indicated above. 



A third explanation is the one accepted by Wichmann (20), 

 namely, that after the formation of the sediments of Pre-Cambrian 

 or very early Palaeozoic age, the area became a land-surface and 

 remained so during the whole of Palaeozoic and Mesozoic time. 

 Then a subsidence permitted the deposition of the Tertiaries, 

 and the final uplift followed as above indicated. 



Any of these hypotheses explains reasonably the structure as 

 we now find it, but there are certain objections in each case. 



To my mind, the first theory is the most probable, namely, 

 that the area has, on the whole, been one of prolonged subsidence. 

 That we should have such a continuous subsidence as this idea 

 calls for, is certainly somewhat difficult to account for. 



In most cases with which I am familiar, where a prolonged 

 subsidence has taken place, it has not, at most, lasted for more 

 than three or four geological periods without ver}^ strong uplifts. 



If, however^ we accept tlie great principle which underlies the 

 theory of the permanence of ocean basins, namely, that the 

 general tendency is for the ocean basins and the continental 

 areas to become more marked — that is, for the oceans to become 

 deeper and the continents higher with increasing age — the diffi- 

 culty, to a great extent at an}'- rate, vanishes, as we have to deal 

 with an area lying between the great oceanic area and the great 

 continental mass, but rather towards the former than towards 

 the latter. 



In the case of the second theory, we are met by several objec- 

 tions. If the area has been one of average continuous elevation 

 it should be one of continuous peripheral growth, but such does 

 not appear to be the case. 



