Marshall. — -Fossils and Age of the Hampden Beds. 463 



Art. XXXIX. — Fossils and Age of the Hampden (Onekakara) Beds. 



By Professor P. Marshall, M.A., D.Sc, Professor of Geology, Otago 



University. 



[Read before the Otago Institute 5th December, 1916 ; received by Editors, 30th December, 

 1916; issued separately, 7th December, 1917.] 



A preliminary reference to the Hampden beds was made by me last year.* 

 At that time the collections that had been made had not been fully worked 

 out. and the following species only were recorded : Avellana tertiaria Marshall, 

 Surcula hamiltoni Suter, and Trigonia n. sp. A specimen of the Avellana 

 has since been sent to M. M. Cossmann, of Paris, but he identifies the species 

 as belonging to the closely allied genus Gilbertia, which is restricted to the 

 Palaeocene. 



That these beds of the Onekakara Beach, three miles north of Hampden, 

 were fossiliferous was known long ago. Mantell made the first collection 

 in 1849, and published the results in the Quarterly Journal of the Geological 

 Society. f He classed the beds as Pleistocene or newer Tertiary. Twelve 

 species of Mollusca are listed, but this list is now of little value. 



Hutton in 1875J placed the beds in the Miocene formation. He gives 

 a list of twenty-one species of Mollusca, but possibly some of these come 

 from neighbouring localities. In 1887 he gave a more detailed description 

 of the locality. § A section shows the exact spot at which fossils are found. 

 He obtained specimens of fourteen species of Mollusca, of which three 

 species are Recent. 



McKay in 1884 classed the beds as Cretaceo-Tertiary, but gave no list 

 of fossils. || He suggests that Recent species that had been placed in other 

 lists had been embedded in the strata as a result of slipping of overlying 

 formations. McKay further discussed the position of these beds in 1887.^[ 

 Again they are classed as Cretaceo-Tertiary, but it is stated that no exact 

 list of the species can be given. 



Park in 1905 classed the formation as Miocene.** He gave a list of 

 twenty-three species of Mollusca, with a percentage of 41-5 per cent, of 

 Recent species. 



The actual rocks consist of argillaceous sands with much glauconite, 

 in places becoming characteristic greensands. They have some concretions, 

 both calcareous and pyritic. The fossils are poorly preserved, and are 

 difficult to extract in a condition that admits of identification. Some 

 four days altogether were spent in collecting. 



McKay'sft statements as to the stratigraphy appear to be substantially 

 correct. The fossiliferous beds rest directly on the strata that contain 

 the well-known Moeraki concretions. These pass downwards into the 

 concretionary but more sandy Kartigi beds, which in turn rest on the 



* Trans. X.Z. Inst., vol. 48, 1916, p. 116. 



t Vol. 6. 1850, p. 330. 



% F. W. Hutton and G. H. F. Ulrich, Geology of Otago, Dunedin, 1875, p. 57. 



§ Trans. X.Z. Inst., vol. 19, 1887, p. 426. 



|| Rep. Geol. Explor. dur. 1883-84, 1884, p. 62. 



If Rep. Geol. Explor. dur. 1886-87, 1887, pp. 6. 238. 



** Trans. X.Z. Inst., vol. 37, 1905, p. 506. 



ft Loc. cit., 1887. 



