498 Transactions. — Geology. 



to places where the conditions were more favourable for their 

 existence. 



Among the living shells found in this horizon, Lucina di- 

 varicata has not been identified in either the Kakanui beds 

 or Waitaki Stone. Bhynchonella nigricans ranges through 

 the three horizons, while Ancilla australis, Scapella gracilis, 

 Siphonalia nodosa, and Struthiolaria jwjmlosa are common to 

 both the Waihao and Kakanui horizons, but absent from the 

 Oamaru Stone, as would naturally be expected. 



Conditions of Deposition. 



The succession of grits and conglomerates, with coal, clays, 

 and sandstones with a littoral marine fauna, followed by 

 coralline sandstones and limestones, clearly prove that the 

 Oamaru series was formed during a period of slow submerg- 

 ence of the old Tertiary shore -line. The grits, and con- 

 glomerates, and fire-clays accumulated on the sea-shore and 

 in estuaries, forming the narrow low-lying beach on which 

 the fringe of coal-vegetation afterwards established itself and 

 flourished. The slow progressive sinking of the land in time 

 submerged the forests and destroyed the vegetation, which 

 became covered with littoral sands and estuarine clays, while 

 the littoral deposits in turn became covered by the coralline 

 accumulations of the deeper seas. 



The character of the fauna and the large size of the shells 

 indicate warm conditions of a subtropical sea. 



Distkibution. 



After the deposition of the Waitaki Stone the sinking 

 movement ceased, and there began a period of elevation. 

 The newly formed beds now emerged from the sea, arranged 

 as a narrow marginal fringe or bench which contoured around 

 the bays and headlands of the old Tertiary shore-line. They 

 also stretched far back among the mountains, into inland 

 basins and winding fiords, some of which for length and 

 diversity of form are without a parallel at the present time. 



Physical Geology. 



From the marginal distribution of the Miocene Tertiaries 

 we gather some interesting information with respect to the 

 physical geography of New Zealand in the Eocene. We 

 learn, in the first place, that the main mountain features had 

 already been determined ; and, in the second place, that the 

 old Tertiary fiords and inland basins, before the Miocene 

 submergence, were merely deep valleys of erosion which the 

 sinking of the land enabled the sea to encroach and flood like 

 the submerged valleys forming the fiords of south-west Otago 

 in the present day. 



