New Zealand Journal of Geology and Geophysics abstracts
Belemnite biostratigraphy of the New Zealand Late Jurassic Mangaoran
(Early Puaroan) Substage and the Puaroan Stage revisited
A. B. CHALLINOR
Department of Earth Sciences
University of Waikato
Private Bag 3105
Hamilton, New Zealand
Abstract Hibolithes arkelli Stevens, H. marwicki
Stevens, and H. mangaoraensis Stevens are common fossils with partly
overlapping stratigraphic ranges in the Mangaoran Substage, of the Late
Jurassic Puaroan Stage . Studies based on samples from known stratigraphic
positions in the Kawhia Harbour sequence provide data for comparative purposes.
The three species are similar in several measurable features. Mean values
differ only slightly, and dispersions are partially concurrent. The specific
identification of fragmentary specimens may be difficult, and that of pre-adult
fragments particularly so. The stratigraphic proximity of the morphologically
similar Upper Ohauan Hibolithes kaimangoensis Challinor is a
complicating factor. The stratigraphic succession of H. arkelli, H.
marwicki, and H. mangaoraensis can be demonstrated in several
sections in the Kawhia and Port Waikato regions. Hibolithes arkelli
grantmackiei Challinor, currently used to define the base of the Puaroan
Stage, is a composite taxon some members of which are here re-identified as
H. arkelli and H. mangaoraensis. The remainder are re-described
as Hibolithes sp A. Its morphology and stratigraphic range are
poorly known and the species is unsuitable as a stage boundary marker.
Hibolithes arkelli regularly appears near the base of the Puaroan Stage
as presently defined and a formal re-definition based on that taxon is
proposed. Although this alters the faunal basis of the stage, the position of
its base remains unchanged.
Keywords belemnites; biostratigraphy; Hibolithes;
morphological similarities; Puaroan Stage (re-defined); Middle Tithonian;
Jurassic; New Zealand
New Zealand Journal of Geology & Geophysics, 1999, Vol. 42:
369-393
0028-8306/99/4203-0369 $7.00/0 (c) The Royal Society of New Zealand
1999
PDF file of entire paper: medium quality (3503K); (scanned from paper original: notes about this process)
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