The Otapirian Stage of the Triassic System of New Zealand Part I

Transactions and Proceedings of the Royal Society of New Zealand, Volume 83, 1955-56, Page 695

The Otapirian Stage of the Triassic System of New Zealand Part I By J. D. Campbell, Canterbury University College, and I. C. McKellar, New Zealand Geological Survey. [Read before the Southland Branch, June 22, 1955; received by the Editor, July 8, 1955.] Abstract The Otapnran Stage is defined; a description is given of the sequence at the type locality, Otapiri Valley, western Hokoui Hills, Southland, and species described from Otapinan localities are listed. Introduction The type locality of the stratigraphic unit formerly known as the Otapiri Series, now the Otapirian Stage (as defined by Marwick, 1953, p. 18), lies in the Otapiri Valley, western Hokonui Hills, Southland. The section exposed along Otapiri Stream (which includes most of the type section) received detailed treatment by Cox (1878) and McKay (1878), but a re-examination of it is nevertheless timely. First, the exact geographic-and hence stratigraphic-positions of some of McKay's localities are not clear from the descriptions. Secondly, the systematic work of Trechmann and Marwick by no means exhausts the fauna known from other Otapirian localities. Some undescribed forms could be useful for correlation elsewhere if their positions in the type sequence were known. Coombs (1950, p. 439) noted a “large and handsome Lima” from the Otapirian beds in the northern Taringatura Hills. The same form is abundantly preserved in the southern Taringaturas. Undescribed pelecypods dominate the Otapirian fauna in the Kaihiku Stream-Puerua River area. That some of these forms might occur in beds at the type locality is suggested by Hector's (1878, p. x) list of 17 Otapirian species other than brachiopods, of which at least 10 remain un-described. It should be noted that the fauna might have been more fully described had Hector's material been better preserved (Marwick, 1946, p. 49). The field work for this paper was done jointly by the writers, with the willing assistance of Abdullah, a student at the Otago School of Mines. Complete responsibility for the map is accepted by one of us (I. C. McK.) while the definition of the stage and the fossil determinations are entirely the work of the other (J. D. C). Fossil localities are referred to by numbers for fossil record forms based on One Mile Sheet districts, the master file being held at the Invercargill Office of the New Zealand Geological Survey. Historical The first record of the term “Otapiri Series “is found in the catalogue of the Colonial Museum for 1870. Here, Hector (p. 195) listed genera occurring

at two localities: “Middle Series, of Otapiri Creek” and “Morley Creek, Southland.” From this brief account it is apparent that the unit as first conceived was broader than the Otapiri Series of Cox and later workers. In classifying 76 beds recognized in the Hokonui Hills, Cox (1878, table facing p. 28) grouped beds 38 to 49 inclusive as Otapiri Series of Liassic age (p. 37). In describing the series (pp. 44-5), he noted that the “highly fossil-iferous” beds (which he termed “Trigonia beds”) were “characterized by the occurrence of certain Spirifers, Trigonia, and… Belemnites otapiriensis Hector… and by the absence of Ammonites from the Bastion series and Monotis from the Wairoa series. “For the north-west corner of the Hokonui Hills he noted the development of the series “between the Benmore and Oreti [Dipton] railway stations… through the southern slopes of Benmore Hill [from whence] it then crosses the Otapiri, the highest bed, Taylor's crossing grit, being found where the Mataura track crosses. From there Taylor's Creek is approximately its higher boundary…. The average thickness of these beds is 1,650 feet… “In the summary (pp. 46-7) he stated “between the Monotis beds of the Wairoa series and the beds with Belemnites otapiriensis, Hect.: at the base of the Otapiri Series, a palaeontological unconformity probably exists, a distinct break in the character of the fossils occurring on this line.” Marwick (1953, p. 59) attributed the description of Otapiria dissimilis (Cox) to Cox (1878, p. 45). Hector (1878, p. vii) designated 1,600 feet of beds in the Hokonui Hills as Otapiri Series of Rhaetic age. In provisional notes on the series (p. x), he commented on the “mixed character” of the fossils, among which he recognized Oolitic, Liassic and Permian species as well as Triassic, and on the abundance of brachiopods, “chiefly pecuhar forms.” He named Clavigera and Rastelligera as new brachiopod genera to accommodate these forms, but no species being cited by him here or in a further publication (1878b), these remained genera caeliba. McKay (1878, pp. 87-9) listed fossils-mainly as genera-collected by him from 14 Otapirian localities in the Hokonui Hills. Two of these are in the type section of the stage, viz.: G.s.362, “Taylor's Crossing, Otapiri Creek,” bed 49 with: Ammonites Cypricardia Halobia ? Spirifer (2 sp.) Spirigera Terebratula, etc. and G.S.367, “In the west bank of Otapiri Creek, half a mile above Taylor's Crossing,” bed 46 with: Spirifer (2 sp.) Rhynchonella (2 sp.) Hector (1878a) described Anlacoceras otapiriense (Hector) from an Otapirian locality at Dipton railway cutting. McKay (1881. p. 44) listed 4 species from an Otapirian locality on the east bank of the Mataura River, near Gore. Two of these: Spiriferma spatulata Hector Rastelligera taylori Hector

Text-Fig. 1.-Geological map of the Otapiri Valley, N.W. Hokonui Hills, Southland. are nomina nuda being Ms. names only. The former name was again published also without description or figure by Hector in 1884 (p. xxxviii). Park (1910, pp. 61, 72) included within the Otapiri Series the two divisions Clavigera beds and Mytilus and Monotis beds. Thomson (1913, p. 15. footnote) appears, on the basis of Marshall's information on the locality from which Proclydonautilus mandevillei (Marshall) and Arcestes hokonui Marshall were described, to have accepted these fossils as belonging to the Otapiri Series. (It can now be stated that the locality is Otamitan). In a census of pre-Cretaceous fossil invertebrates of New Zealand, Thomson (p. 33) included a single valid species (Atractites otapiriensis (Hector)) from

the Otapiri Series It should be noted here that two nomina nuda included in the census (Clavigera tumida Hector and Monotis dissimilis Hector.), have since been validated. In an attempt to validate formally the genera Clavigera and Rastelli-gera, he published figures and type localities for the following Ms. species of Hector: C. bisulcata, C. cuneiformis, C. gracilis, C. tumida and R. elongata. The localities (G.S.371. 366 and 368) were all termed Rhaetic, and are in fact all Otapirian. In a later publication. Thomson (1919, p. 412) assumed responsibility for the species which were cited thus: “Rastelligera elongata Thomson, 1913.” Trechmann (1918) described 6 species of brachiopods from Otapirian localities. He renamed the genus Clavigera, rejected the genus Rastelligera and ignored the species cited by Thomson in 1913. Four of the species described by Trechmann passed into synonymy therefore with the publication of Thomson's 1919 paper. Those retained were Spiriferma gypaëtus Trechmann and Mentzelia kawhiana Trechmann. Trechmann compared an Otapirian ammonite with Arcestes rhaeticus Clark and a brachiopod with Mentzelia ampla Bittner. He confirmed a Rhaetic age for the Otapiri Series (p. 167) but suggested that the upper part of Noric time may also be represented. In a table (facing p. 237) he included- perhaps inadvertently-horizons with Halobia and Monotis in the series. The same author (1923, p. 273) recorded Pteria cf. contorta (Portlock) from an Otapirian locality in Southland, and in 1930 described Atlantobellerophon zea-landicus Trechmann from a Nelson locality that is probably Otapirian in age. Allan (1945, p. 10) declared Clavigera gracilis Thomson synonymous with C. tumida Thomson. Marwick (1946, pp. 29-30) reviewed the Otapiri Series, and for the Mara-kopa coastal section included in it beds with “three well defined forms of Monotis.” In 1951 the same author proposed a new classification for rocks of the Hokonui System, the Otapirian Stage being equivalent to the old unit Otapiri Series. Balfour Series was set up to include the Otamitan, Warepan and Otapirian Stages Fossils listed for the Otapirian Stage were: Clavigera bisulcata Rastelligera elongata Arcestes rhaeticus The last named species was referred by Marwick in 1952 (p. 30) to Rhaetites, a genus placed in synonymy with Arcestes by Spath (1951, p. 129). The new classification was amplified in the comprehensive bulletin on the Hokonui System published by Marwick in 1953. He defined the type locality for the stage and listed 7 species occurring there. Species from other Otapirian localities were mentioned, and the stage was said to be characterized by the “common occurrence of Clavigera and Rastelligera. Neither is confined to it, but beds containing the two in quantity are almost sure to be Otapirian. “Two new species were described: Torastarte bensoni Marwick from an undoubted Otapirian locality in the Hokonui Hills and Monotis calvata Marwick from a bed at Marakopa considered by Marwick to be Otapirian. Fleming (1953) recorded the oyster, Lopha of haidingeriana (Emmrich) from an Otapirian locality 12 miles west of Huntly, Auckland.

Definition The Otapirian Stage is defined as those rocks laid down at the type locality from the first appearance of Spiriferina (Rastelligera) diomedea Trechmann until the appearance of a fauna including psiloceratid ammonites. In stratal terms this consists of 4,000 feet of sandstone, siltstone and fine conglomerate between the localities S169/598 and S169/624. It should be noted that the thickness cannot be estimated accurately because of varying dips; the figure given could be in error by 500 feet. It is clear from McKay's writings that forms other than S. (Rastelligera) diomedea were often-perhaps most often-used m mapping the base of the unit. Myophoria sp. (giving the name “Trigonia beds”) was one of these (McKay, 1879, p. 119; 1881a, p. 106) but this seems to have been used only in the apparent absence of Aulacoceras otapiriense (Hector.). The latter form, though by no means abundant, has the advantage of being distinct from any other New Zealand Triassic fossil. S. (Rastelligera) diomedea is selected as the key fossil for the following reasons: 1. It occurs in the type section. 2. It is easily recognized in the field and is readily separated from the relatively rare species of Rastelligera occurring in Warepan beds. 3. Its appearance in time in the western Hokonui-Taringatura region at least, seems to have coincided with the incoming of A. otapiriense and of a number of other species. 4. It is widely distributed. It is appropriate to mention here the standing of S. (Rastelligera) diomedea as a species. Apart from suspected morphological differences, it is unsafe on stratigraphic grounds to accept Thomson's synonymy of the species with S. (Rastelligera elongata (Hector). It will be seen in Part II of this paper that the type locality of diomedea (Roaring Bay, Nugget Point) is to be correlated with the base of the Otapirian Stage, while the horizon from which elongata was described has long been considered as forming the uppermost bed of the stage The following forms are restricted to Otapirian beds at the type locality of the stage: Mentzelia kawhiana Trechmann Spiriferina (Rastelligera) elongata (Hector) S. (Rastelligera) diomedea Trechmann. S. (Rastelligera) gypaetus Trechmann Clavigera tumida Hector C. cuneiformis Hector (not of Trechmann) Myophoria sp. Pteria cf. contorta (Portlock) Otapiria dissimilis (Cox) Chlamys sp. Lima sp. Aulacoceras otapiriense (Hector) Several undescribed pelecypods and brachiopods, a nautiloid and crinoids qualify for inclusion here. The following are among those forms restricted to beds that are Otapirian by correlation:

Mentzelia cf. ampla Bittner Spiriferina sp. (S. spatulata of Hector) S. (Psioidea) sp. S. (Rastelligera) sp. Anodontophora sp. Triaphorus sp. Torastarte bensoni Marwick. Arcestes cf. rhaeticus Clark Type Locality The type locality of the Otapirian Stage lies in the Otapiri Valley, upstream from the Taylors Stream junction; for much of its length the type section follows along the Otapiri Stream. The rocks have a general north-westerly strike and they dip to the S.W. at angles ranging from 70μ to 25μ. Outcrops occur as low rocky banks beside the Otapiri Stream and occasionally form bars in it. There are several gaps in the section which preclude great accuracy in estimating thicknesses. The choice of locality was however a happy one, for every outcrop proved fossiliferous. The bed in which Spiriferina (Rastelligera) diomedea first appears does not crop out beside the Otapiri Stream; it occurs on the south facing slope 58 chains E. of the stream (S169/598). Its approximate position in the stream section is that of the strike stream joining the Otapiri from the east between two prominent hard bands that are ridge formers in this part of the valley (McKay. 1878, p. 69), a little over a mile upstream from the bridge at Taylors Crossing. The lower coarse bed crops out at stream level and can be traced along the strike in either direction. It contains Monotis richmondiana in abundance in a locality (S169/595) 45 chains west of the stream, on a track on the crest of a ridge between two patches of bush. The same fossil was collected from the summit ridge of the south peak of Benmore (S169/607). Both these localities were known to McKay, who also collected M. richmondiana from the N.W. branch of Taylors Stream (1878, p. 69). Fragments of the same fossil have been found recently in two new localities within a few chains of the Otapiri (S169/631, 632). The higher of the two hard bands referred to above crops out 90 chains up-stream from the bridge; it consists of coarse sandstone and fine conglomerate, and contains S. (Rastelligera) diomedea (S169/596). A break in the section is followed by a series of outerops of hard sandstones that form rapids in the stream between 70 and 80 chains upstream from the bridge. The following fossils occur in the lower part of the group of outcrops (S169/606, 605, 604): Spiriferina (Rastelligera) diomedea Trechmann. Clavigera tumida Hector Anodontophora sp. An undescribed species of Lima makes its appearance in the highest part of the group of outcrops (S169/603). Coombs (1950, p. 439) recorded a similar form from lower Otapirian beds in the Taringatura Hills. The next exposure, separated from the last by a break in the section, occurs on the left bank of the stream three-quarters of a mile upstream from the bridge (S169/602, 601, 600). In a faunule that includes the brachiopods mentioned above for lower beds, the following make their appearance:

“Rhynchonella” sp. “Terebratula” sp. Pteria sp. (cf. Trechmann, 1923) Pleurotomaria sp. crinoid At about this horizon Myophoria sp. was collected at a locality (S169/599), 30 chains E. of Otapiri Stream on the W. side of a S. W. flowing tributary gulley. This is presumably Trigoma vulgaris of Hector and is widely distributed in beds of lower Otapirian age. A gap in the stream section is followed by an outcrop (S169/621) on the right bank of the Otapiri, 40 chains upstream from Taylors Crossing bridge. There is little doubt that this is G.S.367, bed 46 of McKay (1878, p. 88) although subsequent reference has been made to McKay's locality as being one mile above Taylors Crossing (appendix to R. G. E. No. 11, 1878, pp. 196, 203, 209; Thomson, 1913, p. 90). The following make their first appearance in the bed, which also contains Clavigera tumida and Myophoria sp.: “Rhynchonella” sp. Spiriferina (Rastellgera) gypactus Trechmann Otapiria dissimitis (Cox) nautiloid O. dissimilis and C. tumida are common in beds above the present horizon; along with the rhynchonellid they form the characteristic assemblage of the upper Otapirian beds at Kawhia (see Part II). A locality thought to be G. S. 368 is about the same horizon as that just described. The outcrop is 100 chains W. of Otapiri Stream, on the north face of a knob on the spur that leads from the south peak of Benmore, south and then east to the stream G. S.368 is the type locality of S. (Rastelligera) gypaetus Trechmann and of Toraslarte bensoni Marwick. The following are also present (S169/608). “Terebratula” sp. Mentzelia kawhiana Trechmann. Clavigera tumida Hector Myophoria sp. Conularia sp. The next outcrop met with in the stream section is at Taylors Crossing where, in the lower 2 feet of a rocky bank 6 feet high in a cutting on the old Mataura road, the following are preserved in great numbers: Clavigera tumida Hector Otapiria dissimilis (Cox) The bed, known as G. S.362, bed 49 of McKay, is composed of fine sandstone (S169/619), and is overlain by a coarse sandstone making up the upper 4 feet of the bank. The coarser bed (S169/618) was termed Taylors Crossing Grit by Cox and McKay; it contains abundant fragments of S. (Rastelligera) elongata. (Hector) and C. tumida along with rare O. dissimilis and M. kawhiana. The remaining 400 feet of beds of the stage are mostly fine sandstone and siltstone cropping out as stream bluffs south of Taylors Crossing. Only C. tumida and O. dissimilis were found in these outcrops (S169/620, 622, 623). In a bluff 5 chains south of Taylors Crossing swing bridge, a new fauna enters. The boundary between beds containing the two assemblages, here taken as the

Otapirian-Aratauran boundary, is clearly marked at the south end of the bluff where the stream swings sharply eastwards. C. tumida and O. dissimilis were collected within inches of the new fauna which contains Pleuromya sp. and crushed pelecypods (S169/624). Psiloceratid ammonites have not so far been collected from this bluff although, from experience further east, they might be expected here. They are known from higher horizons, such as G.S.355, further south. The Otapirian-Aratauran boundary crosses and re-crosses Taylors Stream 1½ miles S.E. of Taylors Crossing. Otapirian beds with abundant fossils crop out on the left bank of the stream (S169/611) 8 chains downstream from the upper swing bridge. The following forms occur: “Rhynchonella” sp. Mentzelia kawhiana Trechmann Clavigera tumida Hector. Otapiria dissimilis (Cox) Marwick (1953, p. 59) recorded the last named fossil from G.S.5145, 60 yards below the upper swing bridge. On passing downstream from S169/611 the next overlying fossiliferous bed (S169/612) contains the following: “Rhynchonella” sp. “Terebratula” sp. Neither species is known from beds lower in the sequence; the rhynchonellid also occurs in siltstone immediately upstream from the upper swing bridge (S169/610). The terebratulid which is probably Athyris spiculata of Hector Ms. (fide Marwick, pers. comm.) is common in beds overlying those with O. dissimilis, C. tumida and M. kawhiana. It was found to occur with psiloceratid ammonites in at least two localities: on the right bank of Taylors Stream, a quarter of a mile upstream from the junction of the N.W. branch (S169/614, almost certainly G.S.358), and on the left bank of Taylors Stream at the junction of the main north tributary (S169/617). The latter locality is a prolific one; the terebratuhd and fragmentary ammonites are preserved in abundance along with wood, spicules and rare specimens of Chlamys sp. A satisfactory definition of the Aratauran Stage has yet to be published. When this is done the upper limit of the Otapirian Stage adopted in this paper may well require to be modified. Faunal Index No species has been described from the type section of the Otapirian Stage. The following are described from beds that are Otapirian by correlation: Mentzelia kawhiana C. T. Trechmann, 1918 Spiriferina (Rastelligera) elongata (J. Hector, 1913) S. (Rastelligera) diomedea C. T. Trechmann, 1918 S. (Rastelligera) gypaetus C. T. Trechmann, 1918 Clavigera tumida J. Hector, 1886 C. cuneiformis J. Hector, 1886 (not of Trechmann, 1918) C. bisulcata J. Hector, 1913 Otapiria dissimilis (S. H. Cox, 1878) Aulacoceras otapiriense (J. Hector, 1878) Torastarte bensoni J. Marwick, 1953.

Atlantobellerophon zealandicus C. T. Trechmanu, 1930 almost certainly qualifies for inclusion here, but there is considerable doubt as to the age of the bed from which Myophoria heslingtonensis C. T. Trechmann, 1918 was described. The type locality of Monotis calvata J. Marwick, 1953 is thought to be Warepan in age. Figures and descriptions have been published of the following species, the specimens in each case being collected from beds that are Otapirian by correlation: Mentzelia cf. ampla A. Bittner, 1890. (Trechmann, 1918) Pteria cf. contorta (J. E. Portlock, 1843). (Trechmann, 1923) Lopha cf. haidingeriana (A. Emmrich, 1853). (Fleming, 1953) Arcestes cf. rhaeticus W. B. Clark, 1888. (Trechmann, 1918). References Allan. R. S, 1945 Palaeozoic and Mesozoic Brachiopod Faunas in New Zealand; with an Index to the Genera and Species. Trans. Roy. Soc. N. Z., 75, (1), pp. 1-22 Boehm. G, 1910. Fossihen der oberen Trias von der Sudinsel Neuseelands. Centralb. f. Min., 1910, pp. 632-636. Coombs D. S. 1950. The Geology of the Northern Taringatura Hills, Southland. Trans. Roy. Soc. N. Z., 78, (4), pp. 426-448, map. Cox, S. U, 1878 Report on the Geology of the Hokanui Ranges, Southland N. Z. Geol Suiv. Rep Gcol Explor 1877-78 (11). pp. 25-48, table, map, sections Fleming. C. A. 1953 A Thiassic Oyster from New Zealand N. Z. J. Sci. Tech. (B). 35, (3).pp 276-8. Hector, J, 1870 Catalogue of the Colonial Museum, Wellington, New Zealand Wellington, 237 pp —— 1878 Progress Report N. Z. Geol Surv Rep. Geol Explor. 1877-78 (11). pp. i-xiv. —— 1878a. On the Belemnites found in New Zealand. Trans. N.Z. Inst., 10, pp. 484-9. Pls XXII, XXIII. —— 1878b. On the Fossil Brachiopoda of New Zealand. Trans. N. Z. Inst., 11, p. 537-9. —— 1879. Progress Report N.Z. Geol. Surv. Rep Geol. Explor 1878-79 (12), pp. 1-41. —— 1881 Progress Report N. Z. Geol Surv Rep Geol Explor. 1879-80 (13), pp. I-XXX. —— 1884 Progress Report. N.Z Geol Surv. Rep. Geol. Explor. 1883-84 (16), pp. IX-XXXI. —— 1886. Outline of the Geology of New Zealand App to Ind. and Col. Exhib., N.Z. Court, Det. Cat and Guide to Geol Exhib Wellington 88 pp Hevderson, J and Grange, L. I, 1926. The Geology of the Huntly-Kawhia Subdivision, Pnongia and Hauraki Divisions N. Z. Geol. Surv. Bull. No. 28. 112 pp. 3 Pls., maps Hutton, F. W, 1885 Sketch of the Geology of New Zealand Quart. J. Geol Soc. (Lond.), 41, pp. 191-220. McKay, A. 1878 Notes on the Sections and Collections of Fossils obtained in the Hokanui District N.Z Geol Surv. Rep Geol. Explor 1877-78 (11), pp. 49-90 —— 1878a Report on the Wanoa and Dun Mountain Districts N. Z. Geol Surv Rep Geol Explor 1877-78 (11). pp. 119-159. —— 1879 The District between the Wairau and Motueka Valleys N. Z. Geol Surv Rep Geol. Explor 1878-79 (12), pp. 97-121. —— 1881 Mataura Plant-beds, Southland County. N.Z. Geol. Surv. Rep. Geol Explor. 1879-80 (13), pp. 39-48. —— 1881a On the Older Sedimentary Rocks of Ashley and Annul Counties N.Z. Geol Surv Rep Geol Explor 1879-80 (13), pp. 83-118. —— 1884. On the Geology of the Kawhia District. N.Z. Geol. Surv. Rep Geol. Explor.1883-84 (16) pp. 140-8 Mackie, J. B., 1935. The Geology of the Glenomam Survey District, Otago. Trans. Roy. Soc. N. Z., 64. pp. 275-302, Pls 51, 51a. Marwick, J, 1946. The Geology of the Te Kuiti Subdivision N.Z. Geol Surv Bull. No. 41, vi + 89 pp. 28 Pls., maps —— 1951 Series and Stage Divisions of New Zealand Triassic and Jurassic Rocks. N. Z. J. Sci. Tech. (B) 32 (3) pp. 8-10

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