Speight. — The Tertiary Beds of the Trelissick Basin. 321 



Art. [XXIII. — The Stratigraphy of the Tertiary Beds of the Trelissick or 



Castle Hill Basin. 



By R. Speight, M.Sc, F.G.S., Curator of Canterbury Museum. 



[Read before the Philosophical Institute, of Canterbury, 6th December. 1916 ; received by 

 Editors, 30th December, 1916 ; issued separately, 30th October, 1917.] 



Plates XXI, XXII. 



Table of Contents. 



A. Introductory. 



B. General Physical Features. 



C. Stratigraphy. 



1. Statements of Previous Workers ; McKay and Hutton. 



2. Sequence, Thickness, and Arrangement of Beds in Particular Areas : — 



(a.) Lower Members of the Tertiary Sequence occurring in the Broken 

 and Porter Rivers, Whitewater and Coleridge Creeks, &c. ; Volcanic 

 Action. 



(b.) Occurrences of Limestone with Interstratified Tuff in the Porter and 

 Broken Rivers, at Castle Hill, in Whitewater, Volcanic, Coleridge, 

 Waterfall, and Murderer's Creeks ; Nature and Stratigraphical 

 Relationship of the Limestones. 



(c.) Pareora Beds occurring in the Thomas River, Home Creek. Porter 

 River, Whitewater Creek, &c. ; no Evidence of Unconformity. 



D. Tectonic Features. 



E. Volcanic Rocks. 



F. Palaeontology : — 



1. Lists of Fossils from Particular Localities. 



2. Considerations of these Lists. 



3. General Table showing Occurrence and Range of Species. 



A. INTRODUCTORY. 



The Trelissick or Castle Hill Basin, which is situated in the heart of the 

 mountain region of Canterbury, has attracted considerable attention on 

 account of the interesting outlier of Tertiary sediments located therein. 

 It is somewhat surprising that no adequate reference is made to it in the 

 writings of Haast, but its leading physical and geological features, with 

 lists of fossils, have been given by McKay* (with map by Hector) and by 

 Hutton, f and in connection with the former Hector gave a summary of 

 results in the Progress Report introducing the results of the geological 

 explorations for the year. A brief reference is also made to the locality 

 by Marshall, Speight, and Cotton, J and to its features as an intermontane 

 basin by the present author. § There is a reference to the occurrence of 

 certain fossils in this locality, with descriptions, in various lists by Hutton. || 



* A. McKay. Reports of Ceologieal Explorations during 1879-80. 1881, p. 53. 



f F. W. Hutton, Geologv of the Trelissick or Broken River Basin. Trans. N.Z. 

 Inst., vol. 19, 1887, p. 392. 



X P. Marshall, R. Speight, and C. A. Cotton, The Ycunger Rock-series of 

 New Zealand, Trans. N.Z. Inst., vol. 43, 1911, p. 390. 



§ R. Speight, The Intermontane Basins of Canterbury. Trans. N.Z. Inst., vol. 47. 

 1915. p. 341. 181 



|| F. W. Hutton, Catalogue of the Tertiary Mollusca of New Zealand, 1873 ; 

 Mollusca of the Pareora and Oamaru Systems, Proc. Linn. Soc. N.S. If'., vol. 1, 2nd ser. , 

 1887, p. 205. 



11— Trans 



