Offprint from: The oceanic Permian/Triassic boundary sequence at Arrow Rocks (Oruatemanu), Northland, New Zealand
K.B. Spörli A. Takemura R.S. Hori (editors)
GNS Science Monograph 24
BIBLIOGRAPHIC REFERENCE Spörli, K. B.; Takemura, A.; Hori, R. S. (eds.) 2007: The oceanic Permian/Triassic boundary sequence at Arrow Rocks (Oruatemanu), Northland, New Zealand. GNS Science Monograph 24. 229p. Lower Hutt, New Zealand. GNS Science.
GNS Science Lower Hutt, New Zealand 2007
SECTION 2 BIOSTRATIGRAPHY Section 2 Chapter 4: Yamakita et al. - Conodont biostratigraphic framework CHAPTER 4 A CONODONT BIOSTRATIGRAPHIC FRAMEWORK OF A PERMIAN/TRIASSIC OCEAN-FLOOR SEQUENCE IN THE ACCRETIONARY WAIPAPA TERRANE AT ARROW ROCKS, NORTHLAND, NEW ZEALAND SatoshiYamakita1, Atsushi Takemura2, Yoshihito Kamata3, Yoshiaki Aita4, Rie S. Hori5 and Hamish J. Campbell6 1
Department of Earth Sciences, Faculty of Education and Culture, Miyazaki University, Miyazaki 889-2192, Japan. (
[email protected]); 2Geoscience Institute, Hyogo University of Teacher Education, Yashiro-cho, Kato-gun, Hyogo 673-1494, Japan; 3Research Institute for Time Studies, Yamaguchi University, Yamaguchi 753-8512, Japan; 4Department of Geology, Faculty of Agriculture, Utsunomiya University, Utsunomiya +321-8505, Japan; 5Department of Earth Sciences, Ehime University 790-8577, Matsuyama, Japan; 6GNS Science, P.O. Box 31-312, Lower Hutt, New Zealand.
ABSTRACT Abundant microfossils, including conodonts, radiolarians and acritarchs are present in numerous horizons in the Oruatemanu Formation of the Waipapa terrane, exposed along several sections at Arrow Rocks, Northland, New Zealand. Conodont ages at Arrow Rocks range from late Late Permian (Changhsingian) to early Middle Triassic (Anisian). In the Induan to lower Olenekian, seven conodont biozones are distinguished, with a further two zones in the Anisian. Early Triassic conodont assemblages from Arrow Rocks have faunal affinities with those from the Peri-Gondwana Tethys Province rather than with the Tethys sensu stricto. The other microfossil horizons in the Oruatemanu Formation, including radiolarians and acritarchs, are also put into their stratigraphic and paleoenvironmental context. The Unit 2a/2b boundary in the Oruatemanu Formation could correspond to the Permian/ Triassic boundary.
In this paper, we outline the conodont biostratigraphy of the Oruatemanu Formation and integrate the occurrence of radiolarian and acritarch fossils described in Chapters 5 to 7 and Chapter 8 respectively with the resulting biostratigraphic time frame. GEOLOGICAL SETTING The Oruatemanu Formation is divided into eight lithologic units, in ascending order Units 2a, 2b, 3 to 8 (Figs 1 and 2). The basalt of Unit 1, which is exposed on the eastern part of the island and contains numerous lenses of limestone, was originally regarded as the lowermost member of the Arrow Rocks sequence, forming the basement of the pelagic sediments (Takemura et al. 1998). It has recently been re-interpreted as a sill complex that intruded into the poorly consolidated pelagic sequence (Sakakibara et al. 2003).
INTRODUCTION Arrow Rocks (Oruatemanu Island) is a small islet off Marble Bay in the Whangaroa Area, Northland, New Zealand (Chapter 1). Deep sea sediments, including cherts and siliceous mudstones, of the Oruatemanu Formation (Chapter 2) crop out on Arrow Rocks, together with a sill complex of intra-oceanic basalt (Sakakibara et al. 2003; and Chapter 10), which intruded into the sediments. These rocks belong to the Waipapa terrane, a Mesozoic accretionary complex widely exposed in the northern and central part of the North Island of New Zealand (Spörli 1978; Aita and Spörli 1992; Black 1994; Adams and Maas 2004). The age of the Oruatemanu Formation was initially determined to be Middle Permian to Middle Triassic on the basis of radiolarians (e.g. Takemura et al. 1998; 1999; 2002; Takemura, S. et al. 2004). Subsequently, numerous conodonts were collected from this formation by the senior author. Their ages range from Late Permian (Changhsingian) to early Middle Triassic (Anisian), and many Early Triassic conodont biozones were distinguished within the sequence.
Units 2a and 2b were originally regarded as forming one unit, Unit 2 (Takemura et al. 1998). However, because they are separated by a fault and are clearly different in lithology from each other, we continue to regard them as two units. Unit 2a crops out at the southern and northern foot of “East Peak” (informal name), in contact with the basalt of Unit 1 to the east. In the ARG section to the south of “East Peak” (Figs 1 and 3), this unit, about 10 m in thickness, comprises, in ascending order, volcaniclastic rocks, bedded red cherts, bedded red siliceous mudstones, and grey to pale green thin-bedded cherts. Unit 2b forms a continuous exposure in the ARH section on the northern shore of the island, with a minor fault at its base marking the contact with the underlying thin-bedded cherts of Unit 2a. Unit 2b starts with a basal black chert whereas the rest of the 6mthick section is mostly composed of bedded cherts of various colours, some of which are partially or entirely recrystallised (Fig. 3). Stratigraphic columns of Units 3 to 8 were measured and sampled mostly in the continuous ARB and ARC sections, which are exposed on the shore platform between the “East
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Figure 1
Simplified geological map of Arrow Rocks, showing sections measured and fossil localities.
Peak” and “West Peak” (Fig. 1). Unit 3, 2.1 m thick, consists of bedded black or grey cherts and mudstones. It conformably overlies the bedded cherts of Unit 2b and, as seen in the ARH section, the lithologies gradually change at the boundary. Unit 3 is overlain by a pale green tuff layer marking the base of Unit 4 (Fig. 4 in Takemura et al. 2002). Unit 4 consists of bedded red cherts and siliceous mudstones of 6.6 m in total thickness. A fault with a 1.5 mthick shear zone exists between Units 4 and 5. Intensely folded thin-bedded grey cherts occur in this shear zone (Aita and Spörli, this volume). Units 5 to 8 are mostly composed of bedded siliceous mudstones, with colours changing upward from red through maroon to green. Unit 5, 17.2 m thick, consists of bedded red siliceous mudstones with bedding planes
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parallel to the fault at its base. The bedded siliceous mudstones gradually change in colour from red to maroon in the uppermost part and maroon bedded siliceous mudstones of Unit 6 follow conformably. Unit 6 was estimated as 29.5 m in thickness (Takemura et al. 1998), but it has some repetition by faulting and folding and is actually thinner. Unit 7, an 11.2 m-thick alternation of maroon and green siliceous mudstones, shows a lithology intermediate between those of Units 6 and 8. Unit 8, the uppermost unit of the Oruatemanu Formation, crops out on the “West Peak” of Arrow Rocks and consists of green siliceous mudstones with vitric tuffs. A thickness of 27 m was measured, but there is some repetition by folding.
Section 2 Chapter 4: Yamakita et al. - Conodont biostratigraphic framework
CONODONT BIOSTRATIGRAPHY OF THE ORUATEMANU FORMATION In our study, conodont specimens were not extracted from host rocks with hydrofluoric acid, but were observed on surfaces of cleaved small chips of sample rocks. This method is more effective for chert and siliceous mudstone in spite of the restriction on direction of observation, because it provides many more specimens, and even impressions (Imoto and Kozur 1997; Yamakita et al. 1999). We found many conodont specimens from many horizons of the Oruatemanu Formation with this method (Figs 3 to 5). They range from Permian to Triassic in age.
Permian Late Permian-type neogondolellids, with thin and wide platforms, occur sparsely in several horizons of the bedded red siliceous mudstone sequence of Unit 2a. One specimen with an elongate platform rounded at the posterior margin and fused continuous carina connecting with a low cusp, detected in sample ARG 73 collected from the lower part of this sequence, is referable to Neogondolella prechangxingensis (Plate 1, fig. 1). This species was described from the lower part of the Changhsingian (late Late Permian) Changxing Formation at Meishan, South China, and its range was regarded as restricted to the early Changhsingian by Mei et al. (1998). Therefore, the middle part of Unit 2a, including this horizon, can be assigned an early Changhsingian age (Fig. 3). We have not distinguished any conodont zones in Unit 2a at present because the conodonts occur only rarely.
Figure 2 Stratigraphy of the Oruatemanu Formation on Arrow Rocks (Takemura et al. 1998) and summary of age information. The geologic column was taken along the AR, ARB and ARC sections shown in Figure 1. Horizons with radiolarians and acritarchs are also shown.
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Figure 3 Stratigraphic columns of Units 2 to 4 of Arrow Rocks and correlation between sections. Occurrences and local ranges of important conodont species are also shown.
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Figure 4 Stratigraphic column and detailed vertical distribution of conodont species in Units 2b to 3 in ARH section. Numbers indicates frequency of specimens in each 1.5 to 3 kg sample.
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Section 2 Chapter 4: Yamakita et al. - Conodont biostratigraphic framework
Figure 5 sections.
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Stratigraphic column and vertical distribution of conodont species in Units 3 to 6 in ARB and ARC
Section 2 Chapter 4: Yamakita et al. - Conodont biostratigraphic framework
Triassic Triassic conodonts occur in various horizons from Unit 2b to Unit 6. We investigated Lower to MiddleTriassic sequences in several sections and distinguished nine conodont zones, namely Neogondolella carinata Zone, Neospathodus kummeli Zone, Neospathodus aff. kummeli Zone, Neospathodus dieneri Zone, Neospathodus cristagalli Zone, Neospathodus pakistanensis Zone, Neospathodus waageni Zone, Chiosella timorensis Zone and Neogondolella cf. bulgarica Zone in ascending order (Figs 3 to 5). The former seven and the latter two are Early Triassic and Middle Triassic in age respectively. Neogondolella carinata Zone The Neogondolella carinata Zone is characterised by the presence of Ng. carinata (=Gondolella carinata sensu Matsuda 1984) and absence of Neospathodus (Fig. 3). Its top is defined by the first occurrence of Neospathodus kummeli. This zone is recognised in the lower part (about 2.5 m in thickness) of Unit 2b, which is fully exposed at ARH and ARJ sections on the north shore of “East Peak”. In this part, Neogondolella carinata and Neogondolella aff. bisselli are present in many horizons (Figs 3 and 4). Ng. carinata is characterised by a wide and thick platform that downcurves laterally in a large specimen (Plate 1, figs. 4 to 6). Ng. aff. bisselli has small and low denticles and a relatively narrow, elongated platform with a rounded posterior margin and subparallel lateral margin (Plate 1, fig. 2). It resembles Ng. bisselli of Early Permian age, while it differs from Ng. bisselli in having a shallower and wider adcarinal groove. Quite similar specimens were reported as Clarkina aff. phosphoriensis by Jin et al. (1996) from the Otoceras Bed at Selong, South Tibet. They also reported Neogondolella carinata as Clarkina taylorae and Clarkina tulongensis from the same horizons. Thus the assemblage of Neogondolella from the lower part of Unit 2b is similar to that of the Griesbachian in South Tibet. One specimen of the P1 element of Hindeodus sp. was detected in the basal part of Unit 2b in ARH section. Although this specimen is ill-preserved and not identifiable to species level, its broken cusp seems to have been much larger and higher than other denticles (Plate 1, fig. 3). This feature is typical of Griesbachian Hindeodus, such as H. parvus. Most of this zone corresponds to the Neogondolella carinata Zone of Sweet (1970) and Sweet et al. (1971) and Gondolella carinata Zone of Matsuda (1985) of upper Griesbachian (lower Induan), whereas its basal part could be correlated to Anchignathodus typicalis Zone of Sweet (1970) and Sweet et al. (1971) and Isarcicella isarcica Zone or Hindeodus parvus Zone of Matsuda (1985) of lower to middle Griesbachian age, because of the occurrence of Hindeodus sp. Neospathodus kummeli Zone The Neospathodus kummeli Zone is characterised by the presence of Ns. kummeli and absence of other species of
Neospathodus (Fig. 3). Its base and top are defined by the first occurrences of Ns. kummeli and Ns. aff. kummeli respectively. This zone is recognised in the middle part of Unit 2b, just above the Ng. carinata Zone, in ARH and ARJ sections. The lowest occurrence of Ns. kummeli is near the 3.4 m level in the ARH section and the 2.7 m level in ARJ, and the thickness of this zone is about 1 m. Ng. carinata co-occurs in the whole of this zone, and Ng. aff. bisselli and Neogondolella sp. A co-occur in its basal and upper parts respectively. Ng. sp. A is an undescribed species of Neogondolella characterised by subequal-sized, posteriorly inclined denticles and a narrow platform which does not reach or just reaches the cusp at the posterior end of the process (Plate 1, figs. 12 and 13). This zone is correlated with the lower part of the Neospathodus kummeli Zone of Sweet (1970), Sweet et al. (1971) and Matsuda (1985) of lower Dienerian (upper Induan) age. Neospathodus aff. kummeli Zone The Neospathodus aff. kummeli Zone is characterised by the presence of Neospathodus aff. kummeli (Fig. 3). Its base and top are defined by the first and last occurrences of Ns. aff. kummeli. Ns. aff. kummeli (Plate 1, figs. 9 to 11) resembles Ns. kummeli in having subequal-sized denticles and a rounded but not widely expanded posterior margin in aboral view, but the former has posteriorly inclined denticles in the posterior part and only a weakly developed midlateral rib, while the latter has upright denticles and an often well-developed, platform-like midlateral rib. Ns. aff. kummeli also differs from Neospathodus dieneri in not having a widely flared basal cavity and in having subequal denticles. Matsuda (1982) reported two morphotypes of Ns. kummeli from his Ns. kummeli Zone in Kashmir, India. His Type 1 of Ns. kummeli agrees well with the description of Ns. kummeli by Sweet (1970), but the Type 2 of Ns. kummeli does not. Our Ns. aff. kummeli corresponds to Matsuda’s Type 2 of Ns. kummeli. His Ns. kummeli Zone in Kashmir was distinguished based on a record of only one horizon. Samples from nine horizons in ARH section contain Ns. kummeli or Ns. aff. kummeli, and Ns. aff. kummeli occurs in higher horizons than Ns. kummeli with a co-occurring interval (Fig. 4). Here we regard them as different species. The Neospathodus aff. kummeli Zone is recognised in the middle part of Unit 2b, just above the Ns. kummeli Zone, in ARH section, and measures 1.2 m in thickness. Neospathodus dieneri and Neogondolella sp. B occur together in this zone and Ns. kummeli, Ng. carinata and Ng. sp. A co-occur in its lower part. Ng. sp. B is an undescribed species of Neogondolella with posteriorly inclined high denticles and a narrow platform (Plate 1, figs. 14 to 17). In immature specimens, the first or second denticle anterior to the cusp at the posterior end of the process is the highest, while in mature specimens it is the third or fourth denticle. Heights of the denticles gradually decrease toward the anterior end from the highest one.
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This zone is correlated with the upper part of the Ns. kummeli Zone of Sweet (1970), Sweet et al. (1971) and Matsuda (1985) of lower Dienerian age. Neospathodus dieneri Zone The Neospathodus dieneri Zone is characterised by the presence of Ns. dieneri and absence of other species of Neospathodus (Fig. 3). Its base and top are defined by the last occurrence of Ns. aff. kummeli and the first occurrence of Ns. cristagalli respectively. This zone is recognised in the upper part of Unit 2b, just above the Ns. aff. kummeli Zone and beneath the Neospathodus cristagalli Zone in ARH section (Fig. 4). This zone corresponds to the Neospathodus dieneri Zone of Sweet (1970), Sweet et al. (1971) and Matsuda (1985) of middle Dienerian age. Neospathodus cristagalli Zone The Neospathodus cristagalli Zone is characterised by the presence of Ns. cristagalli with the co-occurrence of Ns. dieneri (Fig. 3). Its base and top are defined by the first occurrences of Ns. cristagalli and Ns. pakistanensis, respectively. This zone is recognised in the uppermost part of Unit 2b in ARF section and Unit 3 in ARB, ARF and ARH sections (Figs 3 to 5). Its top is considered to exist near the boundary between Units 3 and 4 or at a slightly higher level, although the exact level is not clear due to a barren interval 1 m thick in the lowermost part of Unit 4. The total thickness of this zone is estimated at about 2.5 m. Sweet (1970) reported that the last occurrence of Ns. cristagalli is lower than the range of Neospathodus pakistanensis in the Salt Range, Pakistan, but Matsuda (1982, 1983) and the Pakistan-Japanese Research Group (1985) reported the co-occurrence of these two species in Kashmir, India, and the Salt Range, Pakistan. Sweet (1988) also considered that the range of Ns. cristagalli overlaps that of Ns. pakistanensis in its upper part. In the Oruatemanu Formation, Ns. cristagalli does not occur together with Ns. pakistanensis, so there is no overlap as reported by Sweet (1970). This zone corresponds to the Neospathodus cristagalli Zone of Sweet (1970), Sweet et al. (1971) and Matsuda (1985) of upper Dienerian age. Neospathodus pakistanensis Zone The base and top of the Neospathodus pakistanensis Zone are defined by the first occurrences of Ns. pakistanensis and Neospathodus waageni respectively (Fig. 3). Ns. dieneri co-occurs in this zone. This zone is recognised in the lower part of Unit 4, above the Ns. cristagalli Zone, in ARB and ARF sections, and measures 2 to 2.5 m in thickness (Figs 3 and 5). Sweet (1970) stated that it is diagnostic of Ns. pakistanensis to have a lower edge that is straight anteriorly but downcurved posteriorly. However, Matsuda (1983) included elements with a totally straight lower edge in this species also, and regarded Neospathodus novaehollandiae described by McTavish (1973), which has a straight lower edge, as a junior synonym of
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Ns. pakistanensis. We agree with this opinion, and assign all specimens having a prominent midlateral rib, a cylindrical rather than a trumpet-shaped basal cavity, and a short posterior process with two or three small denticles, to Ns. pakistanensis (Plate 2, Figs 11-13). This zone corresponds to Ns. pakistanensis Zone of Sweet (1970), Sweet et al. (1971) and Matsuda (1985) of uppermost Dienerian to lowermost Smithian (lower Olenekian) age. Neospathodus waageni Zone The Neospathodus waageni Zone is characterised by the presence of Ns. waageni with co-occurrence of Ns. dieneri (Fig. 3). Ns. pakistanensis also co-occurs in its basal part. The base of this zone is defined by the first occurrence of Ns. waageni. This zone is recognised in the upper part of Unit 4, just above the Ns. pakistanensis Zone, as an interval 1.7 m thick in the ARB section. The top of this Zone is not observed because it is cut off by the fault at the top of Unit 4. Middle to Late Smithian species, such as Neospathodus conservativus and Neogondolella milleri, are entirely absent in this interval. This Zone corresponds to the Neospathodus waageni Zone of Matsuda (1985) and Sweet (1988) of lower Smithian age. Chiosella timorensis Zone The Chiosella timorensis Zone is characterised by the presence of Ch. timorensis. Its top is defined by the first occurrence of Neogondolella cf. bulgarica. Unit 5 and the basal part of Unit 6 are assigned to this zone. The base of this zone is not observed due to the fault at the base of Unit 5. Neospathodus symmetricus, Neogondolella jubata, Neogondolella regale and “Neohindeodella bederi” (form species) occur together in the lower part of this zone. These species are well known to co-occur with Ch. timorensis in many parts of the world. Elements of Ns. symmetricus were assigned to Neospathodus homeri by many authors; however, Orchard (1995) revised the diagnosis of Ns. homeri to restrict it to elements with inturned short posterior process and proposed a new species Ns. symmetricus for elements lacking a posterior process and having subequal denticles. Our specimens lack a posterior process and should be assigned to Ns. symmetricus. This zone corresponds to the Neospathodus timorensis Zone of Sweet (1970), Sweet et al. (1971) and Matsuda (1985) and the Neogondolella timorensis Zone of Koike (1981) and Nakazawa et al. (1994). Their Ns. timorensis Zone or Ng. timorensis Zone was assigned to the upper Spathian (upper Olenekian) or upper Spathian to lower Anisian. Recently, however, the range of Ch. timorensis has been considered to be restricted to the early Anisian (e.g. Orchard 1995). We follow this opinion and regard this zone as lower Anisian. Neogondolella cf. bulgarica Zone The Neogondolella cf. bulgarica Zone is characterised by the presence of Ng. cf. bulgarica. Its base is defined
Section 2 Chapter 4: Yamakita et al. - Conodont biostratigraphic framework
by the first occurrence of Ng. cf. bulgarica. Most of our specimens of Ng. cf. bulgarica are immature and cannot be safely identified, but they are comparable to Ng. bulgarica in the sense that a fused carina has the highest denticle in its middle or slightly posterior position and gradually decreases in height toward both anterior and posterior ends but remains rather high. This zone is recognised in the lower part of Unit 6. Gladigondolella tethydis co-occurs in the upper part of this interval. The top of this zone is not confirmed because conodont records are rare, without any index species, in the upper part of Unit 6 and further upper horizons. This zone is correlated to the Neogondolella bulgarica Zone of Koike (1981) and Nakazawa et al. (1994), of middle Anisian age. CONODONT PALEOBIOGEOGRAPHY OF THE ORUATEMANU FORMATION Matsuda (1985) recognised a provincialism among Early Triassic conodont faunas within the Tethys Realm, and proposed two faunal provinces, the Peri-Gondwana Tethys and the Tethys province sensu stricto. Ng. carinata and Hindeodus minutus are abundant in Griesbachian faunas of the Peri-Gondwana Tethys, while I. isarcica is rare. The conodont assemblages of the Tethys province s.s., however, contain abundant H. parvus and I. isarcica, but only rare Ng. carinata and H. minutus. On the other hand, some authors assume that this faunal difference is due to different biofacies. Orchard (1996) considered Neogondolella and Hindeodus as deep-water and shallow-water genera respectively. Baud (1996) also distinguished Neogondolella-rich deep-water facies and Hindeodus-rich shallow water facies. Lai et al. (2001) proposed a model stating that Clarkina (=Neogondolella) was a deep-water nektobenthic taxon which was driven away during the end Permian to earliest Triassic interval where anoxia developed, but Hindeodus was a pelagic taxon and survived despite the anoxic bottom water. Contrary to these hypotheses, Griesbachian strata deposited in a very shallow marine environment in the Salt Range, Pakistan, which belong to the Peri-Gondwana Tethys province, contain abundant Ng. carinata but rare I. isarcica (Pakistan-Japanese Research Group 1985; Matsuda 1985). Furthermore, the occurrence of H. parvus without any neogondolellids is recorded even in Griesbachian deep-sea sedimentary rocks below the CCD, represented by a chert and siliceous claystone sequence, in a Jurassic accretionary complex in Japan (Yamakita et al. 1999), which was originally deposited in central Panthalassa in low latitudes (Isozaki 1996). These faunal differences are hard to explain with the biofacies theory. The provincialism proposed by Matsuda (1985) is the better interpretation at present. The Griesbachian to early Dienerian conodont fauna from Arrow Rocks, containing common Ng. carinata, shows similarity with the Peri-Gondwana Tethys faunas, and the Lower Triassic of the Oruatemanu Formation is considered to have been deposited in southern higher latitudes.
OCCURRENCE OF OTHER MICROFOSSILS IN THE ORUATEMANU FORMATION As well as conodonts, radiolarians and acritarchs are present in the Oruatemanu Formation (Figs 2, 3). Radiolarians have been found in many horizons of Units 2, 3, 6 and 7. Although one limestone lens within basalt contains well preserved Permian radiolarians (Takemura et al. 1998; 1999, Chapter 5 this volume), this lens is included in a basalt sill and is therefore excluded from the formation. The lowest occurrence of radiolarians is in the bedded red cherts of Unit 2a of the ARG section. Many chert beds in the lower part of Unit 2a contain Middle to Late Permian radiolarians (Chapter 5). Well-preserved radiolarians have also been found in several horizons of bedded cherts in the lower part of Unit 2b of the ARH section. They contain a fauna of Permian-type radiolarians (Chapter 6), but conodonts fix the age of this interval to the Griesbachian (early Induan, Early Triassic). Radiolarians which also seem to have affinities with Permian forms occur in a few horizons in the lower Dienerian Ns. aff. kummeli Zone of the ARF section (Chapter 6). The oldest Mesozoic-type radiolarians appear in bedded cherts of the uppermost part of Unit 2b and Unit 3 in ARD and ARE sections (Fig. 3). This fauna also contains Permian-type radiolarians (Chapter 7). These horizons lie in the late Dienerian Ns. cristagalli Zone. Well-preserved acritarchs also occur within the Dienerian Neospathodus cristagalli Zone, in a chert bed of the upper part of Unit 3, in the ARB section (Figs 2 and 3, Chapter 8). Some chert or siliceous mudstone horizons of Units 4 and 5 (Upper Dienerian, Smithian and Lower Anisian) contain numerous radiolarians. However, they have suffered high recrystallisation so that they cannot be classified. Despite this, their occurrence is important because no radiolarians have been reported from the Smithian worldwide. From higher up in the section, Takemura et al. (2002) reported two Triassic radiolarian horizons in siliceous mudstone (Figs 1 and 2). One (ARB-T57; locality P04/f112/28.5), containing Parentactinia nakatsugawaensis, Archaeosemantis sp., Glomeropyle sp. and Spongosilicamiger(?) sp., is from Unit 6 and is Early to Middle Triassic (Spathian to Anisian) in age, the other (ARC-3; P04/f113/22.4), containing Pseudostylosphaera spinulosa, Cryptostephanidium cornigerum, Tiborella agria and Glomeropyle waipapaensis, from Unit 7, is Anisian (Middle Triassic). In addition, manganese carbonate lenses containing well-preserved radiolarians occur in the upper part of Unit 6 but have not yet been studied in detail.
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SUMMARY OF AGE INFORMATION ON THE ORUATEMANU FORMATION INCLUDING THE P/T BOUNDARY The lowest part of the Oruatemanu Formation (at the base of Unit 2a) is Middle Permian (Guadalupian(?)) in age as indicated by radiolarians from bedded cherts (Takemura et al. Chapter 5 in this volume). Bedded cherts and siliceous mudstones of Unit 2a were deposited during Late Permian (Wuchapingian and Changhsingian) as indicated by radiolarians and conodonts. Lower Triassic cherts and mudstones from Unit 2b to Unit 5 are dated by conodonts, since no radiolarian zonation is available during this time interval. Bedded cherts and siliceous mudstones of Units 2b, 3 and 4 were deposited almost continuously through the Induan and the early Olenekian, because the corresponding sedimentary sequence is continuous and most of the conodont biozones of this time interval have been identified. The age of the lower part of Unit 2b was determined by conodonts as Griesbachian (early Induan) as mentioned above. Neither H. parvus nor I. isarcica, which are index species of the lowest Triassic, have yet been obtained from the lowest part of Unit 2b. However, a remarkable negative excursion in ä13Corg (from -29 ‰ to -35 ‰ PDB) was identified at the black chert horizon lying at the base of Unit 2b (Hori et al., this volume). It is comparable to other potential or confirmed P/T boundary sections in New Zealand (Krull et al. 2000) and South China (e.g. Xia et al. 2004). Therefore, the boundary between Units 2a and 2b could correspond to the P/T boundary, despite the presence of a minor fault at the base of Unit 2b, which suggests that some lowest Triassic (lowest Induan) and/ or uppermost Permian (upper Changhsingian) strata may be missing. The ages of the middle part of Unit 2a to Unit 4 are well defined by successive conodont biozones. The bedded cherts of the middle and upper parts of Unit 2b and Unit 3 are considered to be of Dienerian (late Induan) age. The Induan/Olenekian boundary must lie within Unit 4, and the upper part of this unit is therefore Smithian (early Olenekian). Conodonts indicate an early Anisian age for Unit 5. A gap caused by deformation exists at the boundary between Units 4 and 5, which is a major shear zone where at least the Spathian is missing. However, some of this interval may be represented by the grey cherts involved in the shear zone (Aita and Spörli, this volume) which have not yet yielded any faunas. Unit 6 is considered to be of early to middle Anisian age based on conodonts. Unit 7 is regarded as Anisian in age on the basis of radiolarian occurrences, but no age indicator has been obtained from Unit 8.
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ACKNOWLEDGMENTS We heartily thank Prof. Keisuke Ishida of Tokushima University and another anonymous reviewer for their critical readings and suggestions for improvement of the manuscript. REFERENCES Adams, C. J.; Maas, R. 2004: Age/isotopic characterisation of the Waipapa Group in Northland and Auckland, New Zealand, and implications for the status of the Waipapa terrane. New Zealand Journal of Geology and Geophysics 47: 173-187. Aita, Y.; Spörli, K.B. 1992: Tectonic and paleobiogeographic significance of radiolarian microfossils in the PermianMesozoic basement rocks of the North Island, New Zealand. In Aitchison, J.C.; Murchey, B. ed. The significance and application of Radiolaria to terrane analysis. Palaeogeography, Palaeoclimatology, Palaeoecology 96(1/2): 103-125. Aita, Y.; Spörli, K. B. this volume: Chapter 1, Geological framework for the pelagic Permian/Triassic oceanic sequence of Arrow Rocks, Waipapa terrane, Northland, New Zealand. In Spörli, K. B.; Takemura, A.; Hori, R. S. ed. The oceanic Permian/Triassic boundary sequence at Arrow Rocks (Oruatemanu), Northland, New Zealand. GNS Science Monograph 24: 1-16. Baud, A. 1996: The Permian-Triassic boundary: recent developments, discussion and proposals. Albertiana 18: 69. Black, P. M. 1994: The “Waipapa terrane”, North Island, New Zealand: Subdivision and correlation. Geoscience Report Shizuoka University 20: 55-62. Hori, R. S.; Higuchi, Y.; Fujiki, T.; Maeda, T.; Ikehara, M. this volume: Chapter 9, Geochemistry of the Oruatemanu Formation, Arrow Rocks, Northland, New Zealand. In Spörli, K. B.; Takemura, A.; Hori, R. S. ed. The oceanic Permian/ Triassic boundary sequence at Arrow Rocks (Oruatemanu), Northland, New Zealand. GNS Science Monograph 24: 123156. Imoto, N.; Kozur, H. 1997: The age of Triassic conodonts from shale intercalations in cherts from Kyoto Prefecture, Japan. News of Osaka Micropaleontologists, Special Volume 10: 115-126. Isozaki, Y. 1996: P-T boundary superanoxia and oceanic stratification in Panthalassa. In Noda, H.; Sashida, K. ed. Professor Hisayoshi Igo commemorative volume on geology and paleontology of Japan and Southeast Asia, Gakujutsu Tosho Insatsu. Pp 29-41. Jin, Y.; Shen, S.; Zhu, Z.; Mei, S.; Wang, W. 1996: The Selong section, candidate of the global stratotype section and point of the Permian-Triassic boundary. In Yin, H. ed. The Paleozoic-Mesozoic boundary. Candidates of the global stratotype section and point of the Permian-Triassic boundary. China University of Geosciences Press. Pp 127137. Koike, T. 1981: Biostratigraphy of Triassic conodonts in Japan. Science Report of Yokohama National University Sec. II 28: 25-42. Krull, E. S.; Retallack, G. J.; Campbell, H. J.; Lyon, G. L. 2000: ä13Corg chemostratigraphy of the Permian-Triassic boundary in the Maitai Group, New Zealand: evidence for highlatitudinal methane relaease. New Zealand Journal of Geology and Geophysics 43: 21-23.
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Lai, X.; Wignall, P.; Zhang, K. 2001: Palaeoecology of the conodonts Hindeodus and Clarkina during Permian-Triassic transitional period. Palaeogeography , Palaeoclimatology, Palaeoecology 171: 63-72. Matsuda, T. 1982: Early Triassic conodonts from Kashmir, India. Part 2: Neospathodus 1. Journal of Geosciences, Osaka City University 25: 87-102. Matsuda, T. 1983: Early Triassic conodonts from Kashmir, India. Part 3: Neospathodus 2. Journal of Geosciences, Osaka City University 26: 87-110. Matsuda, T. 1984: Early Triassic conodonts from Kashmir, India. Part 4: Gondolella and Platyvillosus. Journal of Geosciences, Osaka City University 27: 119-141. Matsuda, T. 1985: Late Permian to Early Triassic conodont paleobiogeography in the “Tethys Realm”. In Nakazawa, K.; Dickins, J. M. ed. The Tethys, Her Paleogeography and Paleobiogeography from Paleozoic to Mesozoic. Tokai University Press. Pp. 151-170. McTavish, R. A. 1973: Triassic conodont faunas from western Australia. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 143(3): 275-303. Mei, S.; Zhang, K.; Wardlaw, B. R. 1998: A refined succession of Changhsingian and Griesbachian neogondolellids conodonts from the Meishan section, candidate of the global stratotype section and point of the Permian – Triassic boundary. Palaeogeography , Palaeoclimatology, Palaeoecology 143: 213-226. Nakazawa, , K.; Ishibashi, T.; Kimura, T.; Koike, T.; Shimizu, D.; Yao, A 1994: Triassic biostratigraphy of Japan based on various taxa. In Guex, J.; Baud, A. ed. Recent Developments in Triassic stratigraphy – proceedings of the Triassic symposium, Lausanne, 20-25 Oct., 1991. Memoires de Géologie (Lausanne) 22: 83-103. Orchard, M. J. 1995: Taxonomy and correlation of Lower Triassic (Spathian) segminate conodonts from Oman and revision of some species of Neospathodus. Journal of Paleontology 69(1): 110-122. Orchard, M. J. 1996: Conodont fauna from the Permian-Triassic boundary: Observations and Reservations. Permophiles 28: 29-35. Pakistan-Japanese Research Group 1985: Permian and Triassic Systems in the Salt Range and Surghar Range, Pakistan. In Nakazawa, K.; Dickins, J. M. ed. The Tethys, Her Paleogeography and Paleobiogeography from Paleozoic to Mesozoic. Tokai University Press. Pp. 221-312 Sakakibara, M.; Sakai, T.; Hori, S. R.; Spörli, K. B.; Fujiki, T.; Aita, Y.; Takemura, A.; Campbell, H. J.; Takemura, S.; Kamata, Y.; Yamakita, S.; Suzuki, N.; Nakamura, Y.; Kodama, K. 2003: Basaltic sheet intruding into Middle-Late Permian pelagic sedimentary rocks at Arrow Rocks, Waipapa terrane, North Island, New Zealand. Journal of Geological Society of Japan 109(12): XXIII-XXIV. Spörli, K.B. 1978: Mesozoic tectonics, North Island, New Zealand. Geological Society of America Bulletin 89: 415425.
Sweet, W. C. 1970: Uppermost Permian and Lower Triassic conodonts of the Salt Range and Trans-Indus Range, west Pakistan. In Kummel, B.; Teichert, C. ed. Stratigraphic boundary problems, Permian and Triassic of west Pakistan. University of Kansas, Department of Geology, Special Publications 4: 207-275. Sweet, W. C. 1988: The Conodonta: Morphology, taxonomy, paleoecology, and evolutionary history of a long-extinct animal phylum. Oxford monographs on geology and geophysics No. 10. Oxford University Press. 212p. Sweet, W. C.; Mosher, L. C.; Clark, D. L.; Collinson, J. W.; Hasenmueller, W. A. 1971: Conodont biostratigraphy of the Triassic. Geological Society of America Memoir 127: 441465. Takemura, A.; Aita, Y.; Hori, R. S.; Higuchi, Y.; Spörli, K. B.; Campbell, H.; Kodama, K.; Sakai, T. 1998: Preliminary report on the lithostratigraphy of the Arrow Rocks, and geologic age of the northern part of the Waipapa terrane, New Zealand. News of Osaka Micropaleontologists, Special Volume 11: 47–57. Takemura, A.; Aita, Y.; Hori, R. S.; Higuchi, Y.; Spörli, K. B.; Campbell, H.; Kodama, K.; Sakai, T. 2002: Triassic radiolarians from the ocean floor sequence of the Waipapa terrane at Arrow Rocks, Northland, New Zealand. New Zealand Journal of Geology and Geophysics 45: 315-322. Takemura, A.; Morimoto, T.; Aita, Y.; Hori, R. S.; Higuchi, Y.; Spörli, K. B.; Campbell, H.; Kodama, K.; Sakai, T. 1999: Permian Albaillellaria (Radiolaria) from a limestone lens at the Arrow Rocks in the Waipapa terrane, Northland, New Zealand. Geodiversitas 21: 751–765. Takemura S.; Sakamoto S.; Takemura A.; Nishimura T.; Aita Y.; Yamakita S.; Kamata Y.; Spörli, K. B.; Campbell, H. J.; Sakai T.; Suzuki N.; Hori S. R.; Sakakibara M.; Ogane K.; Kodama K.; Nakamura Y. 2004: Lithofacies of Middle to Upper Permian pelagic sediments in the Arrow Rocks, North Island, New Zealand. News of Osaka Micropaleontologists, Special Volume 13: 21-28. Takemura, A.; Yoshimura, M.; Sakamoto, S.; Takemura, S.; Yamakita, S. this volume: Chapter 5, Permian radiolarians from Arrow Rocks, Northland, New Zealand. In Spörli, K. B.; Takemura, A.; Hori, R. S. ed. The oceanic Permian/Triassic boundary sequence at Arrow Rocks (Oruatemanu), Northland, New Zealand. GNS Science Monograph 24: 87-96. Xia, W.; Zhang, N.; Wang, G.; Kakuwa, Y. 2004: Pelagic radiolarian and conodont biozonation in the Permo-Triassic boundary interval and correlation to the Meishan GSSP. Micropaleontology 50: 27-44. Yamakita, S.; Kadota, N.; Kato, T.; Tada, R.; Ogihara, S.; Tajika, E.; Hamada, Y. 1999: Confirmation of the Permian/Triassic boundary in deep sea sedimentary rocks; earliest Triassic conodont from black carbonaceous claystone of the Ubara section in the Tamba Belt, Southwest Japan. Journal of Geological Society of Japan 105(12): 895-898.
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Plate 1 Permian and Griesbachian to early Dienerian Conodonts from the Oruatemanu Formation at Arrow Rocks (1: Unit 2a, 2-17: Unit 2B). All photographs are in stereographic pairs. Scale bar = 0.5 mm. 1. Neogondolella prechangxingensis (Mei, Zhang and Wardlaw) P1 element, oral view, on a surface of siliceous mudstone, ARG 73 (P04/f117/-6.8). 2. Neogondolella sp. aff. Ng. bisselli (Clark and Behnken) P1 element, oral view, on a surface of a siliceous mudstone film between bedded cherts, ARH 1.6m (P04/f118/1.6). 3. Hindeodus sp. P1 element, lateral view, within chert, ARH 0.5m (P04/f118/0.5). 4-6. Neogondolella carinata (Clark) sensu Matsuda (1984) P1 element, 4. oral view, within chert, ARH 4.7m (P04/ f118/4.7), 5. aboral view, on a surface of chert, ARH 4.6m (P04/f118/4.6), 6. lateral view, within chert, ARH 3.7m (P04/ f118/3.7). 7-8. Neospathodus kummeli Sweet P1 element, 7. oral view, within chert, lighted from right (a) and left (b) sides, ARH 4.6m (P04/f118/4.6), 8. lateral view, within chert, ARH 3.7m (P04/f118/3.7). 9-11. Neospathodus sp. aff. Ns. kummeli Sweet P1 element, 9. lateral view, on a surface of a siliceous mudstone film between bedded cherts, ARH 4.3m (P04/f118/4.3), 10. oblique postero-lateral view, within chert, ARF 3.7m (P04/f116/ 3.7), 11. oblique postero-lateral view of an immature specimen, within chert, ARH 5.2m (P04/f118/5.2) 12-13. Neogondollella sp. A P1 element, 12. lateral view, within chert, ARH 3.7m (P04/f118/3.7), 13. lateral view of a mold specimen, reversely arranged stereographic pair, on a surface of siliceous mudstone film of bedded chert, ARF 3.9m (P04/f116/3.9). 14-17. Neogondollella sp. B P1 element, 14. Oral view, within chert, lighted from right (a) and left (b) sides, ARH 4.6m (P04/f118/4.6), 15. oblique lateral-aboral view, within chert, ARF 3.9m (P04/f116/3.9), 16-17. lateral view of immature specimens, within chert, ARH 4.6m (P04/f118/4.6).
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Plate 2 Dienerian to Smithian Conodonts from the Oruatemanu Formation at Arrow Rocks (1-3: Unit 2b; 4, 7-10: Unit 3; 5-6, 11-16: Unit 4). All photographs are in stereographic pairs. Scale bars = 0.5mm. 1-6. Neospathodus dieneri Sweet P1 element, 1. lateral view, within chert, ARH 5.2m (P04/f118/5.2), 2-3. lateral view of immature specimens, on a surface of a siliceous mudstone film between bedded cherts, ARH 5.5m (P04/f118/5.5), 4. oblique aboral-lateral view of an immature specimen, within chert, ARB 0.3m (P04/f112/0.3), 5. lateral view of an immature specimen, on a surface of siliceous mudstone, ARB 5.3m (P04/f112/5.3), 6. lateral view, on a surface of siliceous mudstone, ARB 4.95m (P04/f112/4.95). 7-10. Neospathodus cristagalli (Huckriede) P1 element, 7. lateral view, on a surface of a siliceous mudstone film between bedded cherts, ARH 6.5m (P04/f118/6.5), 8. lateral view, within chert, ARF 7.55m (P04/f116/7.55), 9. lateral view of a mold specimen, reversely arranged stereographic pair, on a surface of siliceous mudstone film of chert, ARF 6.0m (P04/f118/6), 10. lateral view, within chert, ARB 0.3m (P04/f112/0.3). 11-13. Neospathodus pakistanensis Sweet P1 element, 11. lateral view of a mold specimen, reversely arranged stereographic pair, on a surface of siliceous mudstone, ARB 2.6m (P04/f112/2.6), 12. lateral view, on a surface of siliceous mudstone, ARB 4.5m (P04/f112/4.5), 13. lateral view, on a surface of chert, ARF 10.1m (P04/f118/10.1). 14-16. Neospathodus waageni Sweet P1 element, 14-15. lateral view, on a surface of siliceous mudstone, ARB 5.05m (P04/f112/5.05), 16. lateral view, on a surface of siliceous mudstone, ARB 5.3m (P04/f112/5.3).
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Plate 3 Anisian Conodonts from the Oruatemanu Formation at Arrow Rocks (1-11, 13-15: Unit 5; 12, 16-19: Unit 6). All photographs are in stereographic pairs. Scale bars = 0.5mm. 1-3. Neospathodus symmetricus Orchard P1 element, 1. lateral view, on a surface of siliceous mudstone, ARB 17.4m (P04/f112/17.4), 2. lateral view, within chert, ARB 12.2m (P04/f112/12.2), 3. lateral view, on a surface of siliceous mudstone, ARB 17.0m (P04/f112/17). 4-5. “Neohindeodella benderi” (Kozur and Mostler), 4. lateral view, on a surface of a siliceous mudstone film between bedded cherts, ARB 9.5m (P04/f112/9.5), 5. lateral view, on a surface of siliceous mudstone, ARB 9.6m (P04/f112/ 9.6).. 6-8. Neogondolella jubata Sweet P1 element, 6-7. lateral view, on a surface of a siliceous mudstone film between bedded cherts, ARB 9.5m (P04/f112/9.5), 8. lateral view of an immature specimen, within chert, ARB 11.0m (P04/f112/ 11). 9-11. Neogondolella regale Mosher P1 element, 9. lateral view, on a surface of siliceous mudstone, ARB 8.6m (P04/ f112/8.6), 10. lateral view, on a surface of a siliceous mudstone film between bedded cherts, ARB 9.5m (P04/f112/ 9.5), 11. lateral view, on a surface of siliceous mudstone, ARB 17.4m (P04/f112/17.4). 12-15. Chiosella timorensis (Nogami) P1 element, 12. lateral view of a mold specimen, reversely arranged stereographic pair, on a surface of siliceous mudstone, ARB 28.1m (P04/f112/28.1), 13-14. lateral view, on a surface of siliceous mudstone, ARB 17.1m (P04/f112/17.1), 15. lateral view, within chert, ARB 12.2m (P04/f118/12.2). 16-17. Neogondolella sp. cf. Ng. bulgarica (Budurov and Stefanov) P1 element, 16. lateral view of an immature specimen, within chert, ARB 36.5m (P04/f112/36.5), 17. lateral view of an immature specimen, within chert, ARB 33.8m (P04/f112/33.8). 18-19. Gladigondolella tethydis (Huckriede) P1 element, 18. lateral view, within chert, ARB 36.5m (P04/f112/36.5), 19. lateral view, within chert, ARB 33.8m (P04/f112/33.8).
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