New Zealand Journal of Geology and Geophysics abstracts
Foraminiferal and carbon isotope stratigraphy through the Paleocene-Eocene
transition at Dee Stream, Marlborough, New Zealand
Haidi J. L. Hancock
Gerald R. Dickens*
School of Earth Sciences
James Cook University
Townsville QLD 4811, Australia
email: Haidi.Hancock@jcu.edu.au
C. P. Strong
Christopher J. Hollis
Brad D. Field
Institute of Geological & Nuclear Sciences
P.O. Box 30 368
Lower Hutt, New Zealand
*Present address: Department of Earth Science, Rice University, Houston TX
77005-1892, USA.
Abstract Dee Stream in the Clarence River valley of
New Zealand bisects a well-exposed section of marine sedimentary rocks deposited
in the early Paleogene at high southern latitudes. One hundred metres of
strata lying within this section and comprising cm-dm well-bedded, siliceous
limestone with marly partings was mapped, logged, and sampled to establish
a detailed foraminiferal and carbon isotope stratigraphy and to examine environmental
changes across the Paleocene-Eocene thermal maximum (PETM). Although low
abundance and poor preservation of planktic and benthic foraminifera characterises
much of the Paleocene, foraminifera and carbon isotopes clearly show that
the section spans the upper Paleocene to lower Eocene planktic foraminiferal
zones from Zone P4 to Subzone P6b, and the Subbotina triloculinoides
to Pseudohastigerina wilcoxensis Zones. The δ13C record
correlates closely to other δ13C curves generated from other key
early Paleogene carbonate sequences. The Dee Stream logged section contains
a 1 m thick PETM interval at 26.5 m at the base of Zone P5, or the Morozovella
velascoensis Subzone. Here, benthic foraminifera undergo significant
extinction, Morozovella aequa makes its first appearance, and the
δ13C of carbonate decreases by 2‰. The benthic foraminifer Bulimina
tuxpamensis dominates benthic assemblages immediately following the onset
of the PETM interval, suggesting dysoxic bottom waters during this event.
In conjunction with other recently examined sections from the Marlborough
region, the thick and apparently continuous Paleogene record at Dee Stream
provides an important site for understanding environmental change on high-latitude
continental margins during the Paleogene, including the PETM.
Keywords Clarence River valley; Muzzle Group; planktic;
benthic; isotopes; PETM; Teurian; Waipawan
G02010 Received 13 February 2002; accepted 12 November 2002; published
21 March 2003
New Zealand Journal of Geology & Geophysics, 2003, Vol. 46: 1-19
0028-8306/03/4601-0001 $7.00/0 © The Royal Society of New Zealand
2003
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