REVISION OF THE STRATIGRAPHIC SIGNIFICANCE OF THE OLIGOCENE-MIOCENE "LETTER-STAGES"

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1 REVUE DE MICROPALEONTOLOGIE Vol. 42, n 2, juin 1999, pp REVISION OF THE STRATIGRAPHIC SIGNIFICANCE OF THE OLIGOCENE-MIOCENE "LETTER-STAGES" REVISION DE LA SIGNIFICATION STRATIGRAPHIQUE DES ~ ETAGES-LETTRES ~ DE L'OLIGOCENE-MIOCENE by MarceHe K. BOUDAGHER-FADEL* and Fred T. BANNER* ABSTRACT. -- A new correlation is proposed between the "Letter Stages" of the Far East, the Planktonic Forarniniferal Zones of the Oligocene-Miocene and the European Stages. Constructive criticisms are invited. RI~SUMI~. - Une nouvelle corr6lation est propos6e entre les <<6tages-lettres ~> de l'extr~me-orient, les Foraminif~res Planktoniques Zones de l'oligocbne-mioc~ne et des 6rages Europ6ens. Des critiques constructives sont sugger~es. Key-words : Foraminifera - Oligocene-Miocene Stages - Far East. Mots-cl6s : Foraminif~res - Etages Oligocbne-Mioc~ne - Extreme-Orient. INTRODUCTION The "Letter Stages" were divisions of Tertiary Geological time devised by the micropalaeontologists of the Netherlands East Indies. These "Stages" were really assemblage Zones of larger foraminifera which formed a sequence which was labelled Ta (the oldest) to Th (the youngest). This rather broad classification was improved by dividing certain stages into numbered parts corresponding to the ranges of species or to the occurrence of particular generic assemblages. The Letter Classification was erected because of difficulties encountered when the conventional stage terminology of Europe was applied to successions in the Far East. The difficulties arose because the molluscan and foraminiferal faunas were different in the two regions, although there were enough similarities between the faunas for broad correlation to be possible. Originally, there were only six "Letter Stages" (van der Vlerk and Umbgrove 1927) but these were later increased to eight (Leupold and Van der Vlerk, 1931). Although many modifications of the sequence were attempted, many of the additional subdivisions which were proposed were found to be based on biofacies and not on true evolutionary sequences. As the distribution of Larger Foraminifera is influenced by facies to the same extent as other marine invertebrates, workers such as Leupold and van der Vlerk (1931) and Rutten (1947) produced their own versions of the Letter Classification by recognising stage faunas from main areas and sections. These stages were discussed by Adams (1970, 1984), who based his reconsiderations primarily upon the microfossil successions which he had seen in Borneo, with additional notes on other workers' published records from the Middle and Far East, from Iran to the Pacific islands. Matsumaru (1996) has revised in detail the larger foraminifera of the Palaeogene in Japenese Islands; his youngest assemblage (assem- * Research School of Geological and Geophysical Sciences, University College London and Birkbeck College, University of London, London WC1 6BT.

2 94 OLIGOCENE-MIOCENE "LETTER-STAGES" blage 5) is correctly identified by him as being of Late Oligocene (early "Te Stage"). This paper attempts to reconsider the foraminiferal biostratigraphy of the late "Te" to "Tf3 Letter Stages", and supplements Matsumaru's work. We have adopted much of Adams' work (op. cit.) with many modifications, including those by Wonders and Adams (1991). Others involve much unpublished material originally compiled by Wonders and Banner, together with the elaborate correlations of the planktonic foraminiferal Zones of Banner and Blow (1965) and Blow (1969) attempted by Berggreu et al. (1995); these themselves have required some revisions. We have also included the data obtained by us, but as yet unpublished, from northeast Borneo, as well as from Sumatra and adjacent islands, the Middle East (Cyprus, Banner et al., in press, and Lebanon, BouDagher-Fadel and Noujaim Clark, in press) and Melanesia (principally Papua New Guinea). Much of this remains unpublished as the work was done for commercial petroleum exploration. These data have added to the knowledge of the distribution in the Te and Tf Stages of many taxa on a broad geographic scale so that our regional biostratigraphic knowledge is not simply that which would have been provided by data from a small region. For example, Heterostegina (Vlerkina) borneensis VAN DER VLERK may be restricted in Melanesia to the lower part of the Te interval, but evidence from Borneo has showed that it ranges throughout the Te interval in the eastern region as a whole (BouDagher-Fadel et al., in press). The generalised information given by AGIP biostratigraphers (D. Sartorio and S. Venturini, edts.) on the larger foraminifera have also been taken into account. All the Planktonic Foraminiferal Zones arc summarised by Kennett and Srinivasan (1983). An early attempt to display the ranges of the larger foraminifera taxa in relation to the "Letter Stages" alone was given by Eames et al., 1962, p. 14). Later, the Planktonic Foraminifera Zones were defined and enumerated (Banner and Blow, 1965, Blow, 1959) and they can now he correlated with the "Letter Stages" and shown here. The larger foraminifera which characterise the Oligocene-Mioccne belong to taxa which are either very rare or not present at all in the Oligocene-Miocene of western and central Europe where the stages have their stratotypes. However, by correlating with the planktonic zonation we are now able to correlate the planktonic foraminifera stages with the geostratigraphic stages of western Europe. STRATIGRAPHIC FRAMEWORK The framework of the biostratigraphy is outlined in figure 1. Here the planktonic foraminiferal zones are enumerated and many are explained by the ranges of key taxa. These are derived from many publications, including Blow (1956), Blow and Banner (1962, 1966), Banner and Blow (1967), etc., many of which have been accurately summarised by Kennett and Srinivasan (1983) and by several authors in Bolli, Saunders and Perch-Nielson (1985). Reference can be made to these. Also on figure 1 are many of the larger foraminifera taxa which are known internationally ; these show how "Letter Stages" may be recognised, so these are also drawn out in sequence. The last true Nummulites spp. became extinct at the top of the Td "Stage" with Nummulites fichteli MICHELOTTI (1841) from the upper Early Oligocene of Italy. Contrary to the opinions of S. Cole (in Loeblich and Tappan, 1964) and Loeblich and Tappan (1988), Nummulites can be distinguished from Operculinella. Eames et al. (1962) illustrated a simple Nummulites vascus JOLY and LEYMERIE (plate 1, figures A, B) to compare with Operculineila cumingii (CARPENTER) (Paleonummulites, nomen oblitum, plate 1, figures C, E). The strong dimorphism seen between microspheric and megalospheric forms of Oligocene specimens of Nummulites is never seen in Operculinella (where the microspheric and megalospheric generations are externally identical), the presence of trabeculae in Nummulites and their absence from Operculinella, but, most importantly, the diameter of the megalospheric protoconch of Nummulites (in both simple and complex forms) is much greater than the diameter of the megalospheric protoconeh of OperculineUa. Operculinella (e.g. Operculinella cumingii) persists to the Holocene but the large protoconch of true Nummulites does not occur above the Early Oligocene. The Nummulites is unknown in the Americas. The extinction of Nummulites can be correlated with the end of the Rupelian and planktonic zones P17-P19. The possible ancestor of the Ohgocene Eulepidina is traced by Matsumaru (1996) to the Eocene genus Orbitoclypeus SILVESTRI. Eulepidina H. DOUVILLE (sensu BouDagher-Fadel and Banner, in press), Spiroclypeus H. DOUVILLI~ (sensu Banner and Hodgkinson, 1991) and Tansinhokella (sensu Banner and Hodgkinson, 1991) range up from the Td to the top of the Te. This can be elaborated by evolutionary sequences such as that of Austrotrillina PARR (sensu Adams, 1968).

3 LATE o..ooc~.~ I~,oc~.~l ~,oo.~,oc~ I ~, o ~ I ~ CHATTIAN LANGHIAN SERRAVALLIAN I TORTONIAN I MESSINIAN I STAGE spp. Praeorbulina ~, O lrbulina Globorotalia ~ ; z 7 z z z z PLANKTONIC ZONES r~araglobototalia lenguaensis ~nd~a Paragloborotalia oaralen ua, ensis GL tumida s.s. Globorotalia plesiotumida" ~hero.cuta I~ ~. tum}da G~borotalia praefohsi Globorotalia fohsi! w" SohaeroidinelloDsi.,; subdehiscens t &py~a:::l~ ~kella ll' Flosculinella reichefi Pseudotaberina malabarica I Alveolinella praequoyi Alveolinella quoyi Marginopora vertebralis Austrotnllina striata Austrotrillina asmariensis LeDidocvclina Nephro/epidina ) spp, Miogypsinella spp. Miogypsinoides spp. Miogypsina spp. Miolepidocyclina spp. 9) 2 ~: %-,

96 OLIGOCENE-MIOCENE "LETTER-STAGES" The evolutionary sequence of Austrotrillina species shown here (Fig. 1) and described by Adams (1984) has its origin apparently throughout Tethys.

4 96 OLIGOCENE-MIOCENE "LETTER-STAGES" The evolutionary sequence of Austrotrillina species shown here (Fig. 1) and described by Adams (1984) has its origin apparently throughout Tethys. Different taxa became extinct at different times in different places (Adams, 1984). One excellent section photographed by Matsumaru (1996, pl. 84) from the Early "Te Stage" has broad alveoles in a single series and it is referable to Alveolina striata TODD and POST, not A. howcheni (SCHLUMBERGER) as identified by Matsnmaru (op. cir.). The evolution of Miogypsinella HANZAWA, in the Lower Te, its descendant Miogypsinoides YABE and HANZAWA in the Upper Te-Lower Tfl and then by the true Miogypsina SACCO are well known through the evolutionary studies of Tan Sin Hok (1936, 1937), Drooger (1952, 1963) and Raju (1974). Adams (1984) considered all records known to him of the latest occurrences of Miogypsina. He found evidence for the persistence of Miogypsina up into the equivalent of Planktonic Foraminiferal Zone N9 to be acceptable, but that younger stratigraphic occurrences were doubtful. Our investigations (especially in Papua New Guinea) have shown us that true Miogypsina persists to the top of Tf2 "Letter Stage", the equivalent of Zone Nll-N12, and this confirms to us that many of the records doubted by Adams (1984) were in fact correct. We admit that occurrences of Miogypsina spp. become much less frequent after Tfl "Letter Stage" but the late Tf2 records cannot be dismissed. Matsumaru (1996, figl 23 and 24) dealt with the earliest biostratigraphic occurrences of the Miogypsinidae which he believed occurred in the earliest Te "Letter Stage" (Chattian, Late Oligocene). He illustrated the evolution of Miogypsinella from Neorotalia (called "Pararotalia") via the appearance of Neorotalia-like specimens with very few peripheral chamberlets. These were named Paleomiogypsina and BonineUa by Matsumaru (1996). We have not yet observed good specimens of these two genera but, nevertheless, we agree that Miogypsinella evolved from Neorotalia near the beginning of the lower Te "Letter Stage". One axially-sectioned specimen has been found by us which could be Paleomiogypsina boninensis MATSUMARU, and is illustrated in (Bou- Dagher-Fadel et al., in press). Alveolinella quoyi (d'orbigny) arose from its ancestral A. praequoyi WONDERS and ADAMS, 1991, referred by previous authors to A. fennemai CHECCIA-RISPOLI, as noted by Adams, 1970, at the base of the Tf3, which we can correlate with the horizon of extinction of Katacycloclypeus (TAN), and the base of Zone N13, Late Serravallian. At this same horizon, Marginopora vertebralis BLAINVILLE, arose from its ancestor, Amphisorus EHRENBERG. Both of these species range up into the Holocene, but the end of Tf3 is marked by the extinction of Lepidocyclina (Nephrolepidina) approximately at the end of the Serravallian, the end of the Middle Miocene. The succeeding "Letter Stages" Tg and Th were based upon mollusks and smaller foraminifera and are beyond the scope of this paper. This paper is published in order to draw the attention of concerned biostratigraphers to the work in progress and encourage them to forward to the authors constructive comments on its possible modification. ACKNOWLEDGEMENT We would like to acknowledge the financial support of the South East Asia Research Group. We would also like to thank Dr. Nell Harbury for his help throughout the project and Prof. A.R. Lord, Department of Geological Sciences, University College London, for his the use of facilities in the Postgraduate Micropalaeontology Unit of the Department. BIBLIOGRAPHY ADAMS C.G. (1970) : A reconsideration of the Indian Letter classification of the Tertiary. Bull. British Museant (Natural History) Geology, London, vol. 19, n 3, p ADAMS C.G. (1984) : Neogene larger foraminifera, evolutionary and geological events in the context of datum planes, p In : I. Ikebe and R. Tsuchi (Eds.), Pacific Neogene Datum Planes, University of Tokyo Press, 288 p. BANNER F.T. and BLOW W.H. (1965) : Progress in the planktonic foraminiferal biostratigraphy of the Neogene. Nature, London, vol. 208, n 5016, p BANNER F.T., LORD A.R. and BoUDAGHER-FADEL M.K. : The Terra Limestones Member (Miocene) of Western Cyprus. Greif. Jeo. Ast. Beit. (in press). BERGGREN W.A., KENT D.V., SWISHER II1 C.C. and AUBRY M.-P. (1995) : A revised Cenozoic Geochronology and Chronostratigraphy. In : W.A. Berggren, D.V. Kent, M.-P. Aubry and J. Hardenbol (Eds) : Geochronology Times Scales and Global Stratigraphic Correlation, SEPM Special Publication, Tulsa, n 54, p BLOW W.H. (1969): Late Middle Eocene to Recent planktonic foranliniferal biostratigraphy. Proc. First International Conference on Planktonic Microfossils Geneva, 1967, vol. 1, p BOLLI H.M., SAUNDERS J.B. and Pr;RcH-NIELSEN K. (Eds) (1985) : Plankton Stratigraphy. Cambridge University Press, etc pp. BOUDAGHER-FADEL M.K. and Noujaim CLARK : On the Middle to Late Miocene of Central Coastal Lebanon, Jonrn. micropalaeontol. (in press).

BOUDHAGER-FADEL and BANNER 97 BouDAGHER-FADEL M.K., BANNER F.T., LORD A.R. and NOAD J. : Late Oligocene-Earliest Miocene Reefal Limestones of North Borneo. Journ. Foram. Res. (in press). DROOGER C.W.

5 BOUDHAGER-FADEL and BANNER 97 BouDAGHER-FADEL M.K., BANNER F.T., LORD A.R. and NOAD J. : Late Oligocene-Earliest Miocene Reefal Limestones of North Borneo. Journ. Foram. Res. (in press). DROOGER C.W. (1952) : Study of American Miogypsinidae, Thesis, Univ. of Utrecht, 80 p. DROOGER C.W. (1963) : Evolutionary trends in the Miogy-psinidac. In: G.H.R. yon Koeuingswald, et al. (Eds) : Evolutionary Trends in Foraminifera. Elsevier, London, p HASHIMOTO W. and MATSUMARU K. (1984) : Mesozoic and Cenozoic larger foraminifera of the Philippines and a reference to those from Borneo by the APRSA's paleontological reconnaissance. Geol. Paleont. SE Asia, vol. 25, p KENNETT J.P. and SRINIVASAN M.S. (1983) : Neogene Planktonic Foraminifera, A Phylogenetic Atlas. Hutchinson Ross Pubhshing Company, Pennsylvania, 265 p. LEUPOLD W., VLERK VAN D~:a I.M. (1962) : The Tertiary. Leidsche Geol. Med., Aachen, vol. 5, p MATSUMARU K. (1996) : Tertiary Larger Foraminifcra (Foramini ferida) from The Ogasawara Islands, Japan. Palaeont. Soc. Japan, Spec. Pap., Tokyo, n 36, 239 p. RAJU D.S.N. (1974) : Study of Indian Miogypsinidae. Utrecht Micropal. Bull., vol. 9, 184 p. SARTORIO D. and VENTURINI S. (1988) : Southern Tethys Biofacies, AGIP, San Donato Milanese, 235 p. TAN S~N HOK (1936): Zur Kenntnis der Miogypsiniden (1. Fortsetzung). lug. in Ned. lndie, Bandung, vol. 3 (5), p TAN SIN tlok (1937) : Weitere Untersuchungen tiber die Miogyp siniden II. Ibid., Bandung, vol. 4 (6), p VLERK VAN DER I.M. and UMBGROVE J.H.F. (1927) : Tertiare Gidsforaminiferen va nederlandisch oost-indie. Dutch East Indies, Dienst Mijnb. Weteusch. Meded., n 9, pp WONDERS A.A.H. and ADAMS C.G. (1991) : The biostratigraphical and evolutionary significance of Alveolinella praequoyi sp. nov. from Papua New Guinea. Bull. Brit. Mus. nat. Hist. (Geol.), London, vol. 47 (2), p

THE FORAMINIFERAL FAUNA AND AGE OF SAMPLES FROM THE WIDE BAY-OPEN BAY AREA, EAST NEW BRITAIN. Records 1968/82

THE FORAMINIFERAL FAUNA AND AGE OF SAMPLES FROM THE WIDE BAY-OPEN BAY AREA, EAST NEW BRITAIN by D.J. Belford Records 1968/82 The information contained in this report has been obtained by the Department