Re-evaluation of the conodont Iapetognathus and implications for the base of the Ordovician System GSSP

Fredrik Terfelt, Gabriella Bagnoli, Svend Stouge

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31 Citations (SciVal)


In 2000, the International Union of Geological Sciences (IUGS) ratified the decision
from the International Working Group on the Cambrian–Ordovician Boundary (COBWG)
to place the Global boundary Stratotype Section and Point (GSSP) for the base of
the Ordovician System in the Green Point section, Newfoundland, Canada, at a point
coinciding with the first appearance of the conodont Iapetognathus fluctivagus. However,
a restudy of the conodont successions from Green Point shows that this species is not
present at the boundary interval, and as a consequence the section does not fulfil the biostratigraphical
requirements of a GSSP. The GSSP horizon as now defined is based on a
level part-way through the range of I. preaengensis – a species with lower first appearance
datum (FAD). The true FAD of I. fluctivagus is above the FAD of planktonic graptolites
and well above the FAD of I. preaengensis. As a consequence of these problems, a restudy
of the GSSP section and the other sections in the Cow Head Group is necessary. A redefinition
of the GSSP horizon is suggested. The following four alternative horizons have
potential as new horizons for the GSSP level: the FAD of Cordylodus intermedius; the
FAD of Cordylodus andresi; the FAD of Eoconodontus notchpeakensis; and the FAD of the
agnostoid Lotagnostus americanus.
Original languageEnglish
Pages (from-to)227-237
Issue number2
Publication statusPublished - 2011

Subject classification (UKÄ)

  • Geology


  • global boundary stratotype section point
  • conodont
  • boundary
  • cambrian
  • Iapetognathus
  • ordovician


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