414 Transactions. 



Art. XXXI. — -The Hawera Series, or the So-called "Drift Formation" of 



Haw era. 



By J. Allan Thomson. M.A., D.Sc, F.G.S., Director of the Dominion 



Museum, Wellington, New Zealand. 



[Read before the Wellington Philosophical Society, 20th September, 1916; reecived by 

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



The " drift formation " which is the subject of this paper was so termed 

 by Park in 1887 in his paper " On the Geology of the Western Part of 

 Wellington Provincial District and Part of Taranaki."* Park divides the 

 " Recent and Pleistocene " into — ■ 



(a.) Blown sands, river-terraces, and superficial pumice deposits. 



(b.) Drift formation of Taranaki and Wanganui. 



Using " Notopleistocene " instead of "Recent and Pleistocene," I am in 

 full accord with Park in this classification. The "drift formation" is very 

 well displayed on the coast-line between Wanganui and Hawera, and lies 

 in age between the Wanganuian beds and the superficial blown sands and 

 river-terrace gravels of the district. The superficial pumice beds to which 

 he refers cluster around Moimt Ruapehu, and do not extend into the area 

 under consideration. 



Park gives the following description of the " drift formation " : — 



" This formation is very widely distributed, and extends as a maritime 

 belt from the Ruahine Range to the foot of Mount Egmont ; and, on the 

 North Taranaki coast, from New Plymouth to the Mokau. At Kawaiki 

 it occurs at an altitude of 400 ft. above the sea, but at no other place has 

 it been observed at a greater height than this. 



'' It consists of stratified sands and clays that are usually micaceous, 

 and of a yellow or red colour ; and coarse gravels that are often cemented 

 by iron-peroxide into rusty conglomerates. Near the volcanic centre of 

 Taranaki the gravels consist chiefly of igneous rocks, while east of the 

 Rangitikei they are composed of siliceous sandstones and dark slaty shales. 



" The drift is well exposed in th.e cliffs between Wanganui and Patea, 

 and a great many opportunities are presented of closely studying its 

 character. Drift-timber and upright stumps of trees occur in most places 

 at its base. These are covered or mixed with gravels, in which marine 

 shells are sometimes found in small patches or irregular layers. There 

 appears to be no regular order of superposition of the various beds of the 

 drift. For short distances the drift-timber and gravels are absent, or more 

 frequently appear at the top of the series, and the yellow sands and clays 

 lie directly on the Tertiary clays or limestones. 



" At most places on the coast between Wanganui and Patea the 

 Tertiary strata are but slightly inclined from a horizontal position, and 

 where immediately succeeded by the stratified sands and clays of the drift 

 there is no apparent unconformity between the Pleistocene and Tertiary 

 formations. But, although at special points it is difficult to determine 

 an unconformity, this is made quite clear by the manner in which the drift 

 is foimd resting successively on the different members of the Tertiary 

 formation. At Wanganui it lies on the upper sandy beds, and proceeding 

 along the coast, on the rise of the beds, it may be seen resting alternately 



* Rep. Geol. Explor. during 1886-87, No. 18, 1887, pp. 24-73 (ref. to pp. 57, 59-60). 



