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)

---

This year's abstracts | Journal home page | All abstracts | Publishing home page