Marshall. — Relations between Cretaceous and Tertiary Rocks. 107 



species in a collection of sixty, a percentage of 23-3 ; in the horizon of the 

 limestones at Otiake, fifteen Eecent species in a collection of sixty-one, a 

 percentage of 24 ; in the upper greensands directly above the limestone, 

 forty-seven Eecent species in a collection of 155, a percentage of 33 ; in the 

 next horizon — that of the marls at Awamoa — -twenty-one Recent species 

 in a collection of sixty -four, a percentage of 35. Of these strata, it appears 

 that the last two would have been placed in Hutton's Pareora (Miocene) 

 system, and the two former in the Oamaru (Oligocene) system ; yet some 

 75 per cent, of the species of the limestone horizon occur also in the upper 

 greensands. So far as it goes, this collection of fossils from Oamaru shows 

 a constant increase in the numbers of Recent species. No allowance had 

 been made for the increase in the depth of water in which the sediments 

 were deposited, nor for our lack of knowledge of the fauna of the deeper 

 water off the New Zealand coasts. In this case, however, it is probable 

 that the differences in the depth of water was not very great. 



It is noticeable that Murex and Area have not been found in the lower 

 beds, while Exilia and Niso have been found in the lower only. This, of 

 course, may be due to incomplete collecting, and the dominant fact emerges 

 that the species are so similar throughout that the beds obviously aU belong 

 to one series ; and the palaeontological results confirm the statement of 

 the order of succession of the strata that was based on stratigraphical 

 considerations. Even in the lowest of the strata, however, the fauna is 

 distinctly of a middle Tertiary type when judged by European equivalents 

 or by the percentage of Recent species. As previously pointed out, this 

 latter criterion may be misleading, for it is quite possible that the rate of 

 faunal change in New Zealand, owing to its complete isolation, may be 

 extremely slow. So far as the results that have been obtained at Oamaru 

 up to the present time are concerned, it may be said that there is no indica- 

 tion of a transition from Cretaceous to Tertiary types. Collections have 

 not yet been made from the Black Point beds, where McKay collected some 

 Cretaceous fossils, though Park subsequently collected Tertiary types only. 



II. Relations between Cretaceous and Tertiary Rocks in other 



Countries. 



It appears to be generally thought that there is a great stratigraphical 

 break between the Cretaceous and the Tertiary strata throughout the world. 

 Wilckens, in his w^ork on the younger sediments of Patagonia, has expressed 

 this opinion in its most extreme form. He says, " The division betw^een 

 the Cretaceous and the Tertiary is one of the sharpest known in the whole 

 earth's record. Here occurs a break in our knowledge of our planet which 

 has up to the present been maintained complete. . . . We know of 

 no marine sediments which correspond in age to the interval between the 

 two periods."* In such sweeping statements it appears that the palaeonto- 

 logical side of our knowledge is given great emphasis at the expense of our 

 stratigraphical information. 



In regard to this point, it may be of value to quote the statements 

 made in standard works, since the detailed researches in which the actual 

 original observations of geologists have been recorded are not available. 

 Thus Chamberlin and Salisbury, in discussing the age of some American 

 strata, state, " If the presence of saurian fossils demonstrates the Cretaceous 



* 0- Wilckens, "Die Meeresablagerungen der Kreide- iind Tertiarformation in 

 Patagonien," Neues Jahrb. Min., &c.. Btil.-Band xxi, 1905, p. 147. 



