404 Transactions. — Qeolociy. 



the marl. Between the marl and the limestone rolled volcanic 

 pebbles are found, but these may have come from the same 

 source as the liparite pebbles found at Craigieburn, which were 

 certainly not erupted iu the neighbourhood. Chemically these 

 dykes appear to be closely allied to the tachylyte and palagonite 

 tuffs of White-water and Home Creeks ; so that we may, I think, 

 conclude that they were erupted at the commencement of the 

 Oamaru period, and that their failure to penetrate Prebble Hill 

 was owing to the tough nature of the overlying rocks.''' 



I have considered that the tufaceous beds in White-water 

 Creek are of the same age as those at the Thomas Eiver and 

 Home Creek, where they join the Porter ; but as Mr. McKay 

 holds a different opinion, it is necessary to state the evidence 

 more fully: — (1.) Stratigraphically, the positions of the two are 

 identical. Mr. McKay, unfortunately, missed seeing the out- 

 crop of the Amuri limestone on the left bank of White-water 

 Creek, which is now quite i^lain, although it might liave been 

 covered up at the time of his visit. (2.) Lithologically, the 

 palagonite tuff's are the same in both places, and are quite 

 different to the beds between the marl and the Amuri limestone, 

 at the first gorge of the Porter, with which Mr. McKay would 

 compare them. (3.) Palaeontologically, the fossils from the two 

 localities are identical. If the reader will compare the list of 

 fossils given by Mr. McKay from the tuffs at W^hite-water Creek 

 (locality No. 241) with those from the Fan coral-beds at Thomas 

 Eiver (localities Nos. 23!) and 243), he will find that there are 

 in the first list 23 named species, (the undetermined species not 

 being available for comparison,) all but three of which occur 

 in the Fan coral-beds. And of these three, Triton miniums 

 ( = r. pseudospengleri, Tate) occurs elsewhere in New Zealand, 

 only in the Pareora rocks ; Cah/jitra maculata { = Trochita 

 neozelanica, Lesson) is still living ; and Pcctcn Jwctori (= P. i/a/i- 

 lensis, Ten. -Woods) is a miocene shell of Victoria and South 

 Australia. Consequently, none of these can indicate a greater 

 age for the White-water Creek beds. Mr. McKay says : " The 

 fossils collected from these beds at the first limestone gorge on the 

 Porter Paver were too few to serve the purpose of this comparison ; 

 yet, as far as these may, they tend to show that those from 

 White-water Creek belong to the lower tufas at present under 

 consideration. The comparative list at the end of this report 

 will show upon what grounds this opinion rests." I The locality 



• Since the above was written, Mr. Enys has brought me a specimen 

 from another dyke on the south-west side of Prebble Hill, between dykes 

 c and d. I have culled it dyke J,-. Its specific t^ravity is '281, and no doubt 

 it is a basalt ; but I have not made a microscopical examination. It runs 

 nearly north and south, and may be a continuation of dyke c, which has, 

 however, a specilie ^^ravity of 2\)'2. 



t "Reps. Geo. Expl.," 1879-80, p. 64. 



