Cretaceous Faunas from Zululand and Natal, South Africa. Systematic
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Cretaceous faunas from Zululand and Natal, South Africa. Systematic palaeontology and stratigraphical potential of the Upper Campanian–Maastrichtian Inoceramidae (Bivalvia) Ireneusz Walaszczyk. Faculty of Geology, University of Warsaw, Al. Zwirki i Wigury 93, Warsaw, Poland E-mail: [email protected] William James Kennedy Geological Collections, Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, United Kingdom E-mail: [email protected] & Herbert Christian Klinger Natural History Collections Department, Iziko South African Museum , P.O. Box 61, Cape Town, 8000 South Africa and Department of Geological Sciences, University of Cape Town, Private Bag, Rondebosch, 7701 South Africa E-mail: [email protected] (with 53 figures) Received 27 July 2009. Accepted 27 October 2009 Thirty three species of Inoceramidae, of which two are new, are described from KwaZulu. They fall into four zonal assemblages that can be correlated with sequences recognized elsewhere: the Cataceramus flexus Zone and the ‘Inoceramus’ tenuilineatus Zone are referred to the lower Upper Campanian. The Trochoceramus radiosus Zone is referred to the upper Lower Maastrichtian. The ‘Inoceramus’ ianjonaensis Zone is referred to the lower Upper Maastrichtian, and represents the youngest known assemblage of true inoceramids. There is no evidence for upper Upper Campanian or lower Lower Maastrichtian inoceramids, and this, together with the geological context of the faunas, indicates the presence of a regional unconformity at this level. This is confirmed by the associated ammonite assemblages. The inoceramid faunas include many taxa that have a wide distribution in the northern hemisphere, and provide a basis for correlation with the ammonite and inoceramid zonations recognized in the U.S. Western Interior, and the European ammonite and belemnite succession. Key words: bivalves, inoceramids, Cretaceous, Campanian, Maastrichtian, KwaZulu, South Africa. CONTENTS Abstract · · · · · · · · · · · · · · · · · · · · 49 Cordiceramus paraheberti Genus Platyceramus · · · · · · · · · · · 68 Introduction· · · · · · · · · · · · · · · · · 50 subsp. nov? · · · · · · · · · · · · · · · · · 57 Platyceramus salisburgensis · · · · 68 Field localities · · · · · · · · · · · · · · · 50 Genus Cataceramus · · · · · · · · · · · 57 Platyceramus stephensoni · · · · · · 69 The inoceramid succession · · · 50 Cataceramus? aff. altus · · · · · · · · 58 Genus Trochoceramus · · · · · · · · · 69 The Cataceramus flexus Cataceramus antunesi · · · · · · · · · 58 Trochoceramus radiosus · · · · · · · 70 assemblage· · · · · · · · · · · · · · · · · 50 Cataceramus balticus· · · · · · · · · · 59 Trochoceramus tenuiplicatus · · · · 71 The ‘Inoceramus’ tenuilineatus Cataceramus barabini · · · · · · · · · 59 Trochoceramus thomasi · · · · · · · 71 assemblage· · · · · · · · · · · · · · · · · 50 Cataceramus? bebahoensis· · · · · 60 Trochoceramus cf. thomasi · · · · · 72 The Trochoceramus radiosus Genus Endocostea · · · · · · · · · · · · 72 assemblage· · · · · · · · · · · · · · · · · 52 Cataceramus? sp. aff. Endocostea coxi · · · · · · · · · · · · · 72 The ‘Inoceramus’ ianjonaensis bebahoensis· · · · · · · · · · · · · · · · · 61 assemblage· · · · · · · · · · · · · · · · · 53 Cataceramus flexus · · · · · · · · · · · 61 Endocostea aff. coxi · · · · · · · · · · 73 Biostratigraphy · · · · · · · · · · · · · · 53 Cataceramus? glendivensis · · · · 62 Inoceramids of unknown generic affiliation · · · · · · · · · · · · 74 Palaeobiogeography · · · · · · · · · 55 Cataceramus goldfussianus · · · · · 63 ‘Inoceramus’ ?borilensis· · · · · · · · 74 Comparison of inoceramid and Cataceramus aff. goldfussianus ·64 ammonite associations · · · · · · · 55 ‘Inoceramus’ howletti · · · · · · · · · · 74 Cataceramus mortoni · · · · · · · · · 64 The Campanian/Maastrichtian ‘Inoceramus’ ianjonaensis · · · · · · 75 Cataceramus pteroides pteroides boundary in KwaZulu · · · · · · · · · 56 65 ‘Inoceramus’ tenuilineatus · · · · · · 77 Conventions · · · · · · · · · · · · · · · · 56 Cataceramus pteroides bailyi · · · · 65 ‘Inoceramus’ sp. B · · · · · · · · · · · · 78 Systematic palaeontology · · · · · 56 Cataceramus palliseri · · · · · · · · · · 66 ‘Inoceramus’ sp. C · · · · · · · · · · · · 78 Family Inoceramidae · · · · · · · · · 56 Cataceramus subcircularis · · · · · · 66 Acknowledgements · · · · · · · · · · · · 78 Genus Cordiceramus · · · · · · · · 56 Cataceramus terrazului · · · · · · · · 67 References · · · · · · · · · · · · · · · · · · · 78 Cordiceramus heberti· · · · · · · · 56 Cataceramus sp. A· · · · · · · · · · · · 67 Figures · · · · · · · · · · · · · · · · · · · · · · 83 50 African Natural History, Volume 5, 2009 INTRODUCTION Mtubatuba. Referred to as Locality 20a below, it is 200 m Members of the bivalve family Inoceramidae Giebel, 1852, north of Locality 20. (It is now degraded and overgrown; are abundant in the Late Campanian and Maastrichtian H.C.K., personal observations) sequences of KwaZulu, South Africa; the present account is A further outcrop on the Southern Peninsula that was based on over 700 specimens, collected by Kennedy and concealed during our early field seasons provided one of the Klinger since 1970. key inoceramid faunas described below. Locality 115 (Fig. 1) At some levels in the Maastrichtian in parts of the sequence was referred to division Campanian III in our 1975 publica- calcite prisms derived from their outer shell layer are a major tion, foreshore exposures with concretions and abundant component of the sediment. In spite of their abundance, Menuites (Menuites) spathi (Venzo, 1936). Movement of these bivalves have not been documented previously. The sand revealed a small outcrop of Inoceramus shell bed to the present account is thus the first monographic description of east of the Menuites locality, and at a higher stratigraphical the Late Campanian and Maastrichtian inoceramid bivalves level. It is referred to here as Locality 115A. of KwaZulu, as is the account of their stratigraphical and biogeographical significance. The succession in KwaZulu is THE INOCERAMID SUCCESSION incomplete, as there appears to be a hiatus in the sequence, Inoceramids are common to abundant throughout the with a part of the highest Campanian and lowest Maas- succession studied. The species-level taxonomic diversity is trichtian missing. In spite of this, the sequence of assem- relatively constant, with five to six taxa present in samples blages recognized provides the first documented succession of 25–30 specimens or more. Four successive inoceramid fau- of inoceramid faunas for this interval in the whole of the nas were recognized (Fig. 2). From oldest to youngest, there southern hemisphere. The presence within the inoceramid are the Late Campanian Cataceramus flexus assemblage, faunas studied of a number of taxa common to the the ‘Inoceramus’ tenuilineatus assemblage, the Maas- Euramerican region enables direct inter-regional correla- trichtian Trochoceramus radiosus assemblage and the tion, and the calibration of the South African ammonite ‘Inoceramus’ ianjonaensis (youngest). These in turn define succession against the Euramerican standard. four inoceramid assemblage zones with these same species In spite of their common occurrence, the Late Campanian as zonal indices. and Maastrichtian inoceramids from South Africa were pre- viously known only from scattered references in the The Cataceramus flexus assemblage literature. The youngest inoceramids for which detailed This is is recognized at localities 109A, 109D–E, 110 and accounts are available are Early or at most early Late 111 (Fig. 1). The fauna is dominated by Cataceramus Campanian in age. Heinz (1930) reported on the common species, the most common of which are C. flexus (Sornay, occurrence of Inoceramus regularis d’Orbigny and Inoceramus 1975) and C. balticus (Böhm, 1907). Less common is C. impressus d’Orbigny in the False Bay area, which he visited pteroides bailyi subsp. nov., a geographical subspecies of the during the 1929 International Geological Congress held in Early–early Late Campanian Euramerican C. pteroides South Africa. More recently, Morris (1995) listed two (Giers, 1964). Much less common are Cordiceramus, with Maastrichtian species, Endocostea (Endocostea) coxi a single specimen of C. heberti (Fallot, 1885), and (Reyment, 1955) and ‘Endocostea’ bebahoensis (Sornay, C. paraheberti subsp.nov.? (Sornay, 1968), known from few 1973), which he recognized in the collections studied here. specimens. Some Campanian forms from the subsurface near Durban Of four localities with the C. flexus fauna the number of were described by Kauffman (in Kennedy et al. 1973). These, species-level taxa recognized is relatively high at localities however,are mostly Early Campanian and possibly in part of 111 and 110 (6 and 4, respectively); only two and three earliest Late Campanian age (see comments in Kennedy species are represented at localities 109A and 109D-E, et al. 2008). Inoceramus expansus of Baily (1855), originally respectively. described from the coastal exposures at Mzamba in the The C. flexus fauna is very similar to the Euramerican Eastern Cape Province, is also probably of Early Campanian Cataceramus haldemensis (Giers, 1964) and/or Cataceramus age (see also comments in Heinz 1930). subcompressus (Meek & Hayden, 1860) faunas of the upper (but not uppermost) Middle Campanian (in the tripartite FIELD LOCALITIES American subdivision of the stage), and may be treated as its Details of field localities are given in Kennedy & Klinger geographical