82 Transactions. 



(3.) Greensand, 25 ft. thick with sporadic nodules in the lowest 2 ft., 

 more thickly distributed near the junction. This passes up with 

 occasional more marly or arenaceous layers into arenaceous lime- 

 stone (Mount Brown limestone) ; passage beds are well developed 

 along the junction. 



Boundary Creek. 



Boundary Creek, which lies midway between Stonyhurst and Motunau, 

 was also examined, since McKay (1881, p. Ill) records a good section there. 

 The exposure was found to be very unsatisfactory owing to slips, although 

 probably it was in better condition when McKay described it nearly forty 

 years ago. The Amuri limestone appears to be about 20 ft. thick, but the 

 exact contact with the overlying beds is not visible at present. Large blocks 

 of greensand also occur in the bed of the stream, showing plentiful subangular 

 nodules similar to those in the Motunau, associated with borings filled with 

 greensand, no doubt near the actual junction. McKay does not mention 

 this greensand layer, and says that grey marls immediately overlie the 

 Amuri limestone. Judging by the dip, the limestone is in a conformable 

 position under the top beds of the series, which have a general synclinal 

 arrangement with the eastern limb towards the present coast-line ; but 

 there are local variations in dip well displayed on the sides of the deep 

 gorge which the stream has cut through the non-resistant sands and marls 

 which close the Tertiary series in this locality. It is noteworthy that McKay 

 considers the sequence below the Motunau beds to be perfectly conformable, 

 although he places a stratigraphical break immediately at the base of these 

 beds, a conclusion which appears to us not warranted by observations of 

 dip and a general examination of the section both here and in the Motunau 

 River. The similarity of the sections in the two localities is most marked, 

 and the evidence available from one supports that from the other. 



South Side of Amuri Bluff. (Plate VI, fig. 2.) 



The Amuri limestone is much jointed into flaky quadrangular blocks 

 something like a tiled roof ; it strikes north-east, and dips south-east 30°. 

 The top 4 ft. are bored through and through with tubes which are well 

 filled with calcareous greensand, the phenomena being progressively more 

 marked as the upper surface is reached, where the rock is completely honey- 

 combed and the fragments are detached. These are from 1 in. to 3 in. in 

 diameter and are also completely bored. From this level upwards the 

 pebbles decrease in importance and the greensand increases. All through 

 the greensand layer nodules occur, which become smaller in the upper 

 portions ; the thickness of the greensand layer is about 2 ft., and the nodular 

 portion where the structure is most marked is about 1 ft. thick. Above 

 the greensand layer the rock passes gradually upward for about 3 ft. into 

 typical Amuri limestone. The nodules of the upper layer are markedly 

 phosphatic, while those of the lower layer are only slightly so ; the phos- 

 phatization apparently diminishes progressively from the nodular layer. 

 There are numerous sharks' teeth and occasional bones (? whale-bone) in the 

 nodular layer. 



On Bluff North of the Mikonui Creek. 



The bed is exposed on the face of the cliff immediately to the north 

 of the point where the track rises over the shoulder of the spur to escape 

 high tides. Here we have the following sequence : First, typical Amuri 



