New Zealand Journal of Geology and Geophysics abstracts
Strontium isotope stratigraphy of the Oligocene-Miocene Otekaike Limestone
(Trig Z section) in southern New Zealand: age of the
Duntroonian/Waitakian Stage boundary
IAN J. GRAHAM
HUGH E. G. MORGANS
DAVID B. WAGHORN
Institute of Geological & Nuclear Sciences
P.O. Box 31 312
Lower Hutt, New Zealand
JULIE A. TROTTER
DAVID J. WHITFORD
Centre for Isotope Studies
CSIRO Division of Petroleum Resources
P.O. Box 136
North Ryde, NSW 2113, Australia
Abstract The Otekaike Limestone Trig Z sequence in
southeastern South Island, New Zealand, is the type section for the local
Waitakian Stage, and contains the Duntroonian/Waitakian Stage boundary,
previously thought equivalent to the Oligocene/Miocene Epoch boundary.
Strontium isotope analysis of molluscan (pectinid) macrofossil fragments and
mainly benthic foraminifera from the Otekaike Limestone has, together with
foraminiferal and nannofossil biostratigraphy, provided a chronology for the
section and established a correlation with the global time-scale. Strontium
isotope ratios of macrofossil and foraminiferal extracts are identical and
indicate an age for the section ranging from c. 25.5 Ma at the base
to c. 23.7 Ma at the top, placing most of the section within the late
Oligocene (Chattian). The Duntroonian/Waitakian boundary is set at
c. 25.2 Ma (intra-Chattian) and is not coeval with the
Oligocene/Miocene boundary (23.8 Ma), which occurs near the top of the
section.
Keywords Trig Z; New Zealand; Oligocene; Miocene;
foraminifera; calcareous nannofossils; strontium isotopes; sea-water curve;
absolute age
New Zealand Journal of Geology & Geophysics, 2000, Vol. 43:
335-347
0028-8306/00/4303-0335 $7.00/0 (c) The Royal Society of New Zealand
2000
PDF file of entire paper: medium quality (1920K); (scanned from paper original: notes about this process)
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