Report on the Geology & Gold Fields of Otago
Pareora Formation
Pareora Formation.
Distribution.—This formation is found in the Oamaru district, skirting the seaward side of the low hills between Oamaru and the Waitaki plains, and south of Oamaru to beyond the mouth of the Awamoa. Judging also from a few fossils that I received from the Waitaki, near Otakaik, I suspect that an outlier exists there also, but I have not seen it. South of the Kakanui River it extends to the Otepopo River, and runs north between the Oamaru and Kakanui formations to the Waireka. South of the Otepopo River it extends through Hampden to Moeraki and Kartiki Beach. Up the Shag River it is found as far as Coal Creek, and it forms the whole of the coast from the mouth of the Shag River to Waikouaiti Harbour. In the southern part of the Province it is found on the sea coast between the Tokomairiro and Clutha Rivers, at Wangaloa or Measly Beach (Sec VII., d.) It also occurs in the bed of the Pomahaka below Tapanui, and rises to an elevation of 1180 feet in the Conical Hills. Near Riverton it is again found in the bed of the Pourakino Stream, which flows out of the Longwood Range. In the interior it is extensively developed on the east side of Lake Te Anau from the Eglinton to the Whitestone River, and Mount Prospect, but the boundary between this and the younger lacrustine beds are here not easy to make out without a closer examination than I had time to give to the district. There are also in the museum two fragments of rock enclosing marine fossils belonging to this formation, which are labelled as coming from the Carrick Ranges, but I do not know whether they were obtained in situ or only from boulders.
Rocks.—This formation generally consists of blue sandy clay, often with calcareous concretions, which between Moeraki and Hampden assume the form of true septaria, and have sometimes on their exterior surface fine examples of that peculiar form of crystallation known as "cone-in-cone structure." Between the Shag page 58River and Waikouaiti bands of hard calcareous sandstone are interstratified with it, and at Wangaloa the rocks consists almost entirely of sandstones. In the Pomahaka district the upper beds, which form the Conical Hills, are composed of a white sharp quartz grit containing beautiful impressions of leaves of dicotyledonous plants, which have not yet been described. Inferior brown coal is also found in the Shag Valley and Pomahaka.
Position of Strata.—This formation is usually nearly horizontal in Otago, but on the south side of Oamaru Cape a blue clay belonging to it is seen lying on the Oamaru beds, and dipping conformably with them at an angle of 37° S.W. (Fig. 7, b.), but they soon get horizontal.
Thickness.—I have not been able to estimate the thickness of these rocks.
* Vide ante p. 25.
Awamoa. | Waitaki. | Hampden. | Shag Valley. | Mount Royal. | Wangaloa. | Pomahaka. | Pourakino. | Lake te Anau. | |
Mollusca— | |||||||||
Dentalium mantelli, Zittel | ∗ | ∗ | ∗ | ||||||
Dentalium irregularis, Hutton | ∗ | ∗ | ∗ | ||||||
Dentalium conicum, Hutton | ∗ | ||||||||
Dentalium lævis, Hutton | ∗ | ||||||||
Fusus australis, Quoy | ∗ | ||||||||
Fusus mandarinus, Duclos | ∗ | ||||||||
Fusus plicatilis, Hutton … | ∗ | ||||||||
Fusus nodosus, Quoy … | ∗ | ||||||||
Fusus nodosus, var γ | ∗ | ||||||||
Pleurotoma buchanani, Hutton | ∗ | ∗ | |||||||
Pleurotoma trailli, Hutton … | ∗ | ∗ | |||||||
Pleurotoma awamoaensis, Hutton | ∗ | ∗ | |||||||
Pleurotoma pagoda, Hutton | ∗ | ∗ | |||||||
Bela striata, Hutton | ∗ | ||||||||
Triton spengleri, Chemn … | ∗ | ∗ | |||||||
Triton minimus, Hutton | ∗ | ||||||||
Cominella nassoides, Reeve | ∗ | ||||||||
Cominella funereum, Gould | ∗ | ||||||||
Cominella robinsoni, Zittel … | ∗ | ||||||||
Cominella sp. … | ∗ | ∗ | |||||||
Ancillaria hebera, Hutton … | ∗ | ? | ∗ | ||||||
Ancillaria pomahaka, Hutton | ∗ | ||||||||
Voluta pacifica, Lam var γ | ∗ | ||||||||
Voluta subplicata, Hutton … | ∗ | ||||||||
Mitra apicalis, Hutton … | ∗ | ∗ | ? | ||||||
Amycla, sp. … | ∗ | ∗ | ∗ | ||||||
Marginella albescens, Hutton | ∗ | ∗ | ∗ | ||||||
Fasciolaria, sp. … | ∗ | ||||||||
Natica zealandica, Quoy | ∗ | ∗ | |||||||
Natica ovata, Hutton … | ∗ | ∗ | |||||||
Neritella nitida, Hutton … | ? | ||||||||
Lunatia, sp. … | ∗ | ∗ | ∗ | ∗ | |||||
Sigaretus subglobosus, Sow. | ∗ | ||||||||
Conus ornatus, Hutton … | ∗ | ∗ | ∗ | ||||||
Conus trailli, Hutton … | ∗ | ||||||||
Struthiolaria nodulosa, Lam. | ∗ | ||||||||
Struthiolaria scutulata, Desh | ∗ | page 60 | |||||||
Mollusca— | |||||||||
Struthiolaria cincta. Hutton, var γ | ∗ | ∗ | |||||||
Struthiolaria tuberculata, Hutton | ∗ | ||||||||
Struthiolaria sp. | ∗ | ∗ | |||||||
Cerithium rugatum, Hutton | ∗ | ||||||||
Cerithium cancellatum, Hutton | ∗ | ||||||||
Rissoa vana, Hutton | ∗ | ||||||||
Turritella rosea, Quoy | ∗ | ∗ | |||||||
Turritella vittata, Hutton | |||||||||
Turritella gigantea, Hutton | ∗ | ||||||||
Turritella tricincta, Hutton, var β | ∗ | ∗ | ∗ | ||||||
Turritella bicincta, Hutton | ∗ | – | |||||||
Turritella sp. | ∗ | ∗ | ∗ | ||||||
Turritella ornata, Hutton | ∗ | ||||||||
Phorus conchyliophorus, Born | ∗ | ||||||||
Calyptræa maculata, Quoy | ∗ | ||||||||
Crypta incurva, Zittel | ∗ | ||||||||
Crypta profunda, Hutton | ∗ | ||||||||
Crypta contorta, Quay | ∗ | ||||||||
Crypta ungiformis, Lam. | ∗ | ||||||||
Trochus stoliczkai, Zittel | ∗ | ||||||||
Emarginula striatula, Quoy | ∗ | ||||||||
Cylichna striata, Hutton | ∗ | ? | |||||||
Saxicava arctica, L. | ∗ | ||||||||
Corbula dubia, Hutton | ∗ | ||||||||
Zenatia acinaces, Quoy | ∗ | ||||||||
Psammobia stangeri, Gray | ∗ | ||||||||
Psammobia affinis, Reeve | ∗ | ||||||||
Tellina alba, Quoy | ∗ | ||||||||
Chione stuchburyi, Gray | ∗ | ||||||||
Chione vellicata, Hutton | ∗ | ? | ∗ | ||||||
Chione accuminata, Hutton | ∗ | ||||||||
Chione mesodesma, Quoy | ∗ | ||||||||
Callista disrupta, Desh | ∗ | ∗ | |||||||
Dosinea subrosea, Gray | ∗ | ||||||||
Dosinea grayi, Zittel | ∗ | ||||||||
Tapes intermedia, Quoy | ∗ | ||||||||
Venericardia intermedia, Hutton | ∗ | ∗ | |||||||
Lucina divaricata L | ∗ | ||||||||
Mysia zealandica, Gray | ∗ | ||||||||
Crassatella trailli, Hutton | ∗ | ||||||||
Trigonia pectinata (?), Lam | ∗ | ||||||||
Trigonia semiundulata, M‘Coy | ∗ | ||||||||
Cucullæa, sp. | ∗ | ∗ | |||||||
Pectunculus laticostatus, Quoy | ∗ | ||||||||
Pectunculus globosus, Hutton | ∗ | page 61 | |||||||
Mollusca— | |||||||||
Limopsis insolita, Sow | ∗ | ||||||||
Limopsis zealandica, Hutton | ∗ | ∗ | |||||||
Nucula nitidula, Adams | ∗ | ||||||||
Solenella australis, Zittel | ∗ | ∗ | ∗ | ||||||
Hinnites trailli, Hutton | ∗ | ||||||||
Pecten hochstetteri, Zittel | ∗ | ||||||||
Lima colorata, Hutton | ∗ | ||||||||
Brachiopoda— | |||||||||
Rhynchonella nigricans, Sow | ∗ | ||||||||
Polyzoa— | |||||||||
Pustulipora zealandica, Mantell | ∗ | ||||||||
Echinodermata— | |||||||||
Arachnoides placenta, L. | ∗ | ||||||||
Arachnoides conica, Hutton | ∗ | ||||||||
Schizaster rotundatus, Zittel | ∗ | ||||||||
Actinozoa— | |||||||||
Turbinolia, sp. | ∗ | ||||||||
Diatomaceæ— | |||||||||
Coscinodiscus, sp. | ∗ | ||||||||
Actinoclyclus, sp. | ∗ |
In addition to the above, beautiful casts in sandstone of dicotyledonous leaves are found at the Conical Hills near Tapanui.
Age.—The Moeraki, or Hampden clay was considered by Dr. Mantell and Professor Morris in 1850 to be pleistocene. In 1866 Dr. Hector called the Pomahaka series miocene, and the Moeraki clay eocene. In 1870, Mr. C. Traill stated his conviction that the Awamoa beds were not younger than miocene. In 1872, I referred the Awamoa beds to the upper miocene, and those at Te Anau Lake to the upper oligocene; and in 1873, I referred the rocks at Awamoa, Hampden, Pomahaka, and Waitaki to the upper miocene, and the Te Anau beds doubtfully to the lower miocene. I now consider them all to be the upper miocene.
Nomenclature.—The name of Pareora series was first applied by Dr. von Haast to some rocks in the south of Canterbury. I have not been able to find where this name was first published, and I have never examined the rocks myself, but took the name from Dr. Hector’s catalogue of the Colonial Museum*
* Page 186.