Speight. — An Ancient Buried Forest near Riccarton. 361 



Art. XXV. — An Ancient Buried Forest near Riccarton : its Bearing on 

 the Mode oj Formation of the Canterbury Plains. 



By E. Speight, M.Sc, F.G.S., Curator of Canterbury Museum. 



[BfMil befort tht Philosophical Institute of Canterbury, 6th December, 1916; received by 



Editors, 30th December, 1916 ; issued separately, 30th October, 1917.] 



Plate XXIII. 



As the mode of formation of the Canterbury Plains is a matter of especial 

 scientific interest, I venture to submit the following short note, based, on 

 the existence of an ancient buried forest, in support of the idea first 

 advanced by Haast (1, 2), and endorsed by the surveys of Doyne (3, 4) and 

 Dobson, that the plains have been formed almost entirely by the action of 

 aggrading streams, and that the form of their surface is due to the over- 

 lapping and coalescence of the fans of glacier-fed rivers. The original 

 hypothesis has received support from most geologists of standing, notably 

 from Professor W. M. Davis, who after an examination of their salient 

 features has expressed to me privately his substantial adherence to Haast's 

 theory. This opinion was, however, strongly opposed by Hutton (5, 6), who 

 regarded the plains as a marine deposit built up from material brought 

 down by rivers, the upper surface being a plain of marine denudation. 



In two somewhat recent papers (7, 8) I have urged that after being built 

 up in the way suggested by Haast, or while they were actually in process 

 of formation, they were subjected to a gradual sinking of the land— that is, 

 instead of the chief recent movement being one of elevation, as demanded 

 by Hutton, it has been one of subsidence. This is proved almost con- 

 clusively by the records of the bores of the artesian-well sinkers in the 

 Christchurch area. On the margin of the plains, especially just north of 

 Banks Peninsula, there is an inte -mingling of land and marine beds, the 

 latter with marine shells overlying beds of terrestrial origin. There has 

 been a struggle between the agents responsible for building up the land 

 and those causing depression, in all probability the latter getting the better 

 of it ; but the effect of this struggle is not clearly manifest on the inland 

 part of the plains owing to the enormous depth of the gravel deposit and 

 the absence of sections showing the whole sequence. The records of the 

 bore being put down at Chertsey for the purpose of prospecting the plains 

 for petroleum show up to the present a thickness of 1,250 ft. of shingle 

 and clay deposit, with no clear sign of a change in its character from that 

 occurring near the surface. 



When the earliest colonists arrived in Canterbury in the early " forties" 

 there were patches of forest growing on the low-lying and swampy areas 

 in the neighbourhood of Riccarton, Papanui, Rangiora, and Temuka ; while 

 near Oxford, Alford Forest, Mount Peel, and Geraldine the eastern foothills 

 of the Southern Alps were clad with submontane forest, tongues of which 

 stretched out into the plains for a varying distance, that from Oxford 

 following the line of the River Eyre and almost junctioning with the patch 

 on the plains near Rangiora and Woodend ; also from the north-western 



