president's address — SECTION 0. 89 



In the middle part of this extent of limestone, namely, from the 

 Weka Pass to the Kaikoura Peninsula, the upper portion of the 

 calcareous formation is a marly rock known as the Weka Pass 

 stone. The contact between it and the Amuri limestone is peculiar, 

 and was considered by Hutton to be a very significant uncon- 

 formity, separating the Oligccene Oamaru system from the under- 

 lying Cretaceous Waipara, system. Morgan (1916) concurs in 

 accepting this as an important unconformity. Marshall, and also 

 Speight and Wild (1918) do not belie.ve it to be such; nor till 

 recently (1912) did Park, who, moreover, has since (1917) with- 

 drawn his acceptance of this contact as an unconformity. The obser- 

 vatioms ol Speight and Wild have been very extensive. They believe 

 the peculiar features of the supposed erosion surface of Amuri lime- 

 stone are the result of extensive boring by some annelid during the 

 interval between the deposition of the typical Amuri limestone and 

 the upper more glauconitic Weka Pass stone. " The character of 

 the junction requires a uniformity of conditions over wide areas, 

 which would be obtained if the bored surface were a sea-bottom, 

 and not a shore line. The increased phosphatization of the frag- 

 ments of Amuri limstone, and, perhaps, of the true phosphatic 

 nodules (found here) might be accounted for by the decay of 

 the bodies of the boring organisms," in addition to the usual 

 chemical concentration. Thomson (1920), however, agrees with 

 Morgan that the penetration of limestone by greensand has taken 

 place along joint planes, enlarged by solution, and extends the 

 list of recorded occurrences of small pebbles of quartz-schist or 

 greywacke in this horizon. He concludes that the contact between 

 the Weka Pass stone and the Amun* limestone represents a period 

 during which deposition practically ceased, perhaps, by a shallow- 

 ing due to regressions, and boring and solution of the upper sur- 

 face of the Amuri limestone took place. Though it has not the 

 significance of uplift and great erosion attached to it by Hutton 

 and at one time by Park, it is nevertheless a correct place to draw 

 the dividing line and small time interval betweien the Cretaceous 

 and Tertiary beds By this time the surrounding land has been 

 reduced to a very low relief, and the attainment of such would 

 demand a period of still-stand, which agrees with the explanation 

 oflFered for the nature of the uoper surface of the Amuri lime- 

 stone, according to Thomson (1920, p. 411), whose discussion of 

 the problem is here summarized. 



The Lower Tertiary sea flooded widely over the peneplain -sur- 

 face, and this may be termed the Oamaruian transgression. In 

 the Clarence Valley, homson (1919) obsei"ved that argillaceous, or 

 arenaceous limestones, comparable with the Weka Pass stone, were 

 about 150 feet thick, and some volcanic tuff occurs locally in con- 

 nexion therewith. Impressions of dicotyledonous leaves and a few 

 molluscs occur of the tyne found in the Oamaru district, described 

 subsequently. In the Waipara- Weka Pass district, the Weka Pass 



