This is the first study of cretaceous or Paleogene Radiolaria from on-land New Zealand. It is based on five Late Cretaceous to Paleocene sections within the Amuri Limestone Group of eastern Marlborough (NE South Island): Woodside Creek, Wharanui Point, Chancet Rocks, Flaxbourne River and Mead Stream. Faunas from coeval sediments at DSDP Site 208 (Lord Howe Rise, north Tasman Sea) are also reexamined. Because diverse and well-preserved radiolarian faunas are common, the location of the Cretaceous/Tertiary (K/T) boundary well-documented, and the earliest Paleocene relatively complete, these sections provide the most complete known record of radiolarian evolution from latest Cretaceous to mid Late Paleocene (c.70-60 Ma). Systematic treatment of K-T transitional faunas was hampered by a dichotomy between Cenozoic and Mesozoic methodologies and nomenclature. To resolve this schism, broad taxonomic definitions are adopted, numerous synonymies are identified, and several revised definitions are proposed for established taxa. Of the 94 taxa recorded, 65 are species or species groups, and 29 are undifferentiated genera or higher level categories. Three new species are described: Amphisphaera aotea n.sp., A. kina n.sp. and Stichomitra wero n.sp. A new latest Cretaceous to mid Late Paleocene zonation is proposed. Six new interval zones are defined by the first appearances of the nominated species. In ascending order these are: Lithomelissa? hoplites (RK9, Cretaceous), Amphisphaera aotea (RP1, Paleocene), A. kina (RP2), Stichomitra granulata (RP3), Buryella foremanae (RP4) and B. tetradica (RP5) Interval Zones. The Late Paleocene Bekoma campechensis Zone of Nishimura (1987) succeeds RP5 at Mead Stream. The K/T boundary does not mark an extinction event for radiolarians, but does coincide with a sudden change from nassellarian to spumellarian dominance. It also coincides with a sudden influx of diatoms in Marlborough, where a fall in sea level appears to have promoted upwelling. Thus, rather than marking a catastrophe, the K/T boundary heralded a period (from RP1 to lower RP3) of great productivity for siliceous plankton. With a return to conditions similar to those of the Cretaceous, later in the Paleocene (upper RP3-RP6), Cretaceous survivors were rapidly replaced by new Tertiary taxa in deep-water settings. However, in shallower settings, many Cretaceous taxa remained abundant throughout the Early Paleocene. Faunal changes at site 208 are similar to those of the deep-water Marlborough sections, but without clear evidence for increased fertilty in the earliest Paleocene.
| Identifer | oai:union.ndltd.org:ADTP/274914 |
| Date | January 1991 |
| Creators | Hollis, C. J. |
| Publisher | ResearchSpace@Auckland |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated., http://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm, Copyright: The author |
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