Art. XXXIX.—On the Wanganui Beds (Upper Tertiary).

Transactions and Proceedings of the Royal Society of New Zealand, Volume 2, 1869, Page 163

Art. XXXIX.—On the Wanganui Beds (Upper Tertiary). By J. Buchanan, of the Geological Survey of New Zealand. [Read before the Wellington Philosophical Society, September 18, 1869.] The following notes give the results of a comparison of the fossil shells from the Upper Tertiary stata of New Zealand, which are in the Colonial Museum, with the fossils obtained by the author, in that portion of the formation locally known as the “Wanganui series”: Wanganui Beds (Upper Tertiary). The information, respecting the latter series, is founded on personal examination of the cliffs of the Wanganui river, near the township, and

continued six miles on No. 2. road-line, in the direction of Wangaehu, and six miles on No. 3 road-line, up the river; also, as far north as Patea for forty miles along the sea coast, at various points between the Kai Iwi and Waitotara rivers, and between the Whenuakura and Patea rivers. Over the area thus surveyed, the beds are uniformly the same, so that it is unnecessary to protract a section of each particular locality. In some places they are slightly disturbed—as for instance opposite the town of Wanganui—but, on the whole, they strike in North and South line, with a dip of 10° to 15° to the East; the blue clay stratum which I shall describe, keeping, in general, parallel with the drainage level of the country. The formation consists of an upper sandy, and lower clay stratum, and separated by a deposit of sand of varying thickness, being at least twelve feet in Shakespere cliff, at Wanganui, the whole covered by a heavy deposit of sands and gravels, containing a cemented gravel bed also of variable thickness, the material from which is in common use for the construction of roads throughout the district. Along the sea coast the blue clay rises to a height of from one to forty feet above the sea level. A few shells appear to be confined to this deposit, such as Murex* Instead of attempting to give scientific names, the numbers by which each specimen is distinguished in the Museum, is employed.—Ed. No. 2, Pecten No. 2, and Mytilus No. 2. A few others decrease upwards in the series such as Ancillaria, Murex No. 1, Fusus No. 2, Pecten No. 1, and Ostrea No. 2. Again, a few shells, poorly represented in the blue clay, become very numerous in the upper bed, such as Lucina No. 2, Rotella, Waldheimia, and Imperator imperialis. The upper bed of the series has generally an open sandy matrix, varying in thickness from four feet at Shakespere cliff, to over a hundred feet at the lower cliffs below Putiki pa; the blue clay, or lower bed, scarcely showing there above the river level. In this upper bed the following species occur for the first time, in addition to those mentioned as common to both formations: Ostrea ingens, Cardium No. 2, Tapes, Ostrea No. 3, Pecten No. 7, Tellina, Pectunculus No. 1, Mactra No. 1, Pileopsis, Pectunculus No. 3, Mactra No. 2, Triton, Pecten No. 3, Donax, Myadora. (Extinct forms are in italics.) There is every probability that, in addition to the above two beds, an older stratum exists, more inland, characterized by the presence of Cucullæa, and if the blue clay of the Patea river should prove to belong to this lower bed, the proportion of extinct species in the Wanganui beds would be considerably diminished. Napier Beds (Upper Tertiary). The fossils collected at Napier are too few to determine the relative position of the Limestone formation there; but there is no doubt that several of them are identical with those of the Upper Wanganui beds, and probably belong to the same period. Blue Clay-marl. Kanierei River, Westland. Of the fifteen species collected at Hokitiki, every one of them are common at Wanganui, so that it may be inferred that they belong to the same period.

Shakespere Cliff Wanganui

Kawau Island Beds. The Kawau Island deposits contain only extinct species, and have been erroneously grouped with the newer-tertiary formation, by Hochstetter, from the species having been mixed with more modern forms from a littoral deposit at Cape Rodney. A list of the Cape Rodney shells is given separately; all of them being extinct species. Awatere and Motanau Beds (Upper Tertiary). The Awatere and Motanau clays are undoubtedly of the same age, and it is very probable, when further examined over the whole area, will be naturally grouped in three subdivisions. At Motanau three beds can be distinctly recognized: first, an upper sandy bed, containing the most common shells of the adjacent coasts; second, a middle blue clay bed, containing probably fifty species, nine-tenths of which are identical with those of the blue clay at Wanganui; these upper and middle beds lie conformable, and have, evidently, like those at Wanganui, been accumulated on their breeding grounds, on quiet sea bottoms. Not so the third, or lower, blue clay bed, found inland near its outcrop. It exhibits masses of concreted broken shells, the result of wave action on an ancient sea beach. The proportion of extinct species in this series is very small, and those chiefly miocene fossils, of the lower bed, such as Cucullæa. Summary. By a comparision of the fossils collected in the different districts, with those of Wanganui taken as a standard—as being the most complete—the evidence is conclusive of the sameness of the whole, with the exception of the Kawau beds, as a reference to the columns will show. The formation must be divided into three groups: an upper, a middle, and a lower; nearly every genus of the upper and middle beds still existing on the adjacent coasts. Napier. Ostrea—2 sp., Mytilus, Pecten—3 sp., Crepidula, Calyptræa, Venus, Pectunculus. Total, 10 sp.: recent 7, extinct 3. Cape Rodney. Haliotis, Cardium, Scalaria, Fusus—2 sp., Turritella, Teredo, Pectunculus, Pecten—2 sp., Rhynchonella, Turbo, Ostrea. Total, 14 sp.: recent 13, extinct 1. Kawau. Ostrea, Turritella, Turbo, Crassitella, Natica, Pectunculus. Total, 6 sp., all extinct. Hokitika. Fusus—2 sp., Dentalium, Voluta—2 sp., Natica, Limopsis, Trophon, Turritella, Leda, Pecten, Ancillaria, Cassis, Venus, Pectunculus. Total, 15 sp.: recent 13, extinct 2. Waipara. Fusus—2 sp., Natica, Turritella—2 sp., Scalaria—2 sp., Struthiolaria—2 sp., Crepidula—2 sp., Calyptræa, Voluta, Cucullæa—4 sp., Dentalium, Echinite—3 sp., Trochus, Shark's tooth, Crania, Pectunculus—2 sp., Waldheimia—4 sp., Ostrea, Venericardia, Myodora, Pecten—5 sp., Venus—2 sp., Mactra, Mytilus, Modiola, Lucina, Panopæa, Cytherea, Artemis, Lima. Total, 48 sp.: recent 27, extinct 21.

Awatere. Fusus—3 sp., Voluta—2 sp., Natica, Turritella—3 sp., Struthiolaria—6 sp., Crepidula—3 sp., Calyptræa, Trochita, Ancillaria, Balanus, Pectunculus, Ostrea—2 sp., Pinna, Mactra, Lutraria, Artemis, Tapes, Tellina, Cucullæa, Dentalium, Purpura. Total, 34 sp.: recent 26, extinct 8. Motanau. Fusus, Voluta—2 sp., Natica—2 sp., Struthiolaria—3 sp., Turritella, Crepidula, Venericardia, Pecten, Ostrea, Terebratula, Cardium, Pectunculus, Mactra, Dosinia, Artemis, Tapes, Venus—4 sp., Sanguinolaria, Lutraria, Cucullæa—2 sp., Dentalium—2 sp., Tellina, Mytilus, Trochus, Nerita, Balanus, Rotella, Imperator, Pholas, Saxicava, Pinna, Modiola, Struthiolaria. Total, 42 sp.: recent 34, extinct, 8. Wanganui. Murex—3 sp., Fusus—6 sp., Trichotropis, Trophon, Mangelia, Triton, Buccinum—4 sp., Purpura, Lymnæa, Ancillaria, Cassis, Trochus—2 sp., Imperator, Rotella, Pleurotoma, Auricula, Cerithium, Turritella—3 sp., Scalaria, Mytilus—2 sp., Ostrea—3 sp., Pinna, Modiola—2 sp., Venus—8 sp., Dosinla, Terebratula, Terebratella, Waldheimia—3 sp., Rhynchonella, Cardita, Tapes, Artemis, Lucina—2 sp., Cardiu—3 sp., Venericardia, Natica—3 sp., Voluta—2 sp., Struthiolaria—3 sp., Pileopsis, Crepidula—3 sp., Calyptræa, Trochita, Emarginula, Hemitoma, Lima—2 sp., Balanus, Echinus, Echin-arachnius, Turbinolia, Vermetus, Teredo, Coral—2 sp., Bryozoa (?), Pecten—7 sp., Mactra—3 sp., Arca, Chamostrea, Nucula, Corbula, Tellina—2 sp., Lutraria, Panopæa, Mya, Pectunculus—4 sp., Mesodesma—3 sp., Donax, Psammobia, Sanguinolaria, Myodora. Total, 121 sp.: recent 109, extinct 12. Grand Total, 290 sp.: recent 229, extinct 61.