Uttley. — Volcanic Rocks of Oamarti. 



Ill 



The nodular limestone is of a similar character to the concretionary 

 bands described by the present writer at Kakanui (1916, p. 23). but in the 

 present occurrence there is very little glauconitic sandy material present, 

 and the band is extremely hard throughout, the nodules being set in a 

 calcareous matrix. The nodules vary in size up to the size of a cricket- 

 ball ; they show a concentric structure, with occasionally a central nucleus, 

 while sometimes the centre is hollow. 



The brachiopod band is a calcareous glauconitic sand, crowded with the 

 typical Hutchinsonian fossil Pachymagas parki (Hutt.). Other species that 

 occur are Pecten delicatulus Hutt. and Pecten (Pseudamusium) huttoni Park. 

 The shell-bed (i) is 2 ft. thick, and consists of a mass of shells embedded 

 in fine grey sands. The fossils are much broken and very friable, and it 

 was difficult to obtain specimens. The bed, however, is similar to the 

 shell-beds at Target Gully and Ardgowan described by Marshall and myself 

 (1913). One fossil obtained here was Aetheia gualteri (Morris), which has 

 not hitherto been obtained above the characteristic Pachymagas parki 

 greensands. Overlying the shell-bed is a blue mudstone with well-preserved 

 fossils which clearly indicate that the bed is Awamoan. A list of fossils 

 from this rock has been given by Marshall (1915, p. 384). 



The two sections described above are exposed on the extreme north and 

 extreme south respectively of a main anticlinal fold, the arch of which has 

 been thrown into minor undulations and faulted in several places. Between 

 the two exposures tuffs are exposed everywhere along the foreshore, but 

 they have not yet proved fossiliferous. Although, as mentioned above, 

 there are stratigraphical breaks in these tuffs and breccias, they are appa- 

 rently of minor significance, as the rocks above and below are lithologically 

 similar. Former observers have considered this underlying mass of volcanic 

 rocks to be Waiarekan, but there is not the slightest positive evidence to 

 support this contention. If they are Waiarekan, the breaks in the sequence 

 mentioned above assume a much greater importance, for they will represent 

 the time during which the greater part of the Ototara stone was being 

 deposited. 



(3.) Hutchinson Quarry and Neighbourhood. 

 Near the abandoned quarry at Eden Street the typical Hutchinson Quarry 

 beds occur. Although the exposures in this locality are small and discon- 

 nected, the succession is clear, and will 

 be best represented by a diagrammatic 

 vertical section. 



The lowest beds are fine calcareous 

 tufaceous rocks (a) weathering greenish- 

 brown, containing in places large frag- 

 ments of decomposed vesicular basalt, 

 and ramified throughout by calcareous 

 veins. The bed is 20 ft. thick in the 

 section, but the base is not visible. This 

 passes gradually into the overlying bed 

 (b), which is 6 ft. in thickness. It is 

 a confused mass of glauconitic sands, 

 hardened limestone, and tufaceous matter. 

 In places, however, the limestone shows 

 in bands from 1 in. to 1 ft. in thickness. 

 Fragments of fossils are visible but none 



Fig. 3 — Section at Hutchinson Quarry. 

 (a) Tufaceous rock, 20 ft. ; (6) lime- 

 stone bands with tufaceous rock, 6 ft. ; 



(c) limestone conglomerate, 11 ft. ; 



(d) greensand, 15+ ft. 



are recognizable. 



Overlying is a mass 



