Journal of the Royal Society of New Zealand abstracts
Sequence stratigraphy of the Nukumaruan Stratotype
(Pliocene-Pleistocene, c. 2.08–1.63 Ma), Wanganui Basin, New
Zealand
S. T. Abbott1*, T. R. Naish2, R. M. Carter3,
and B. J. Pillans4
1School of Earth Sciences,
University of Tasmania, Private Bag 79, Hobart, TAS 7001, Australia.
2Institute of Geological and Nuclear
Sciences, P.O. Box 30 368, Lower Hutt, New Zealand.
3Marine Geophysical Laboratory, James Cook University,
Townsville, QLD 4811, Australia.
4Research School of Earth Sciences, Australian National
University, Canberra, ACT 2000, Australia.
*Present address: School of Environmental
Science and Management, Southern Cross University, P.O. Box 157,
East Lismore, NSW 2480, Australia. Email: sabbott@scu.edu.au.
Abstract Late Pliocene to Early Pleistocene
(c. 2.08—1.63 Ma) strata exposed in coastal cliffs along Nukumaru
and Ototoka beaches near Wanganui, between the top of the Nukumaru
Limestone and the base of the Butlers Shell Conglomerate, comprise 11
depositional sequences of a total thickness of c. 86 m. The
sequences consist predominantly of silicilclastic shoreline facies.
Non-marine facies (including palaeosols), and a variety of
shallow-marine shellbed facies, are also represented. Patterns in
facies composition and sequence architecture reveal three sequence
motifs (Maxwell, Nukumaru, and Birdgrove) that
represent progressively increasing maximum palaeowater depths within a
broadly basin-margin palaeogeographic setting. The sequence motif
changes systematically up section and records a lower order tectonic
influence on accommodation that has modulated the stacking patterns of
individual sequences. Correlation of the sequences with oxygen isotope
stages 77–57 is achieved using the basin-wide Ototoka tephra, and
indicates that the sequences accumulated in response to obliquity
driven (41 k.y. duration) glacio-eustatic sea-level oscillations.
Correlation of the Nukumaru coast sequences with other sections along
basin strike, and the global oxygen isotope record indicates that (i)
500 k.y. (δ18O stages MIS 56–34) is missing at the
unconformity between the Nukumaruan and overlying Castlecliffian
stratotypes on the Wanganui coast, and (ii) the Pliocene-Pleistocene
boundary lies within sequence NC7 at the base of the Lower Maxwell
Formation.
Keywords cyclothem; sequence; motif; systems
tract; tephra; cyclostratigraphy; obliquity; glacio-eustasy; sea level;
Pliocene; Pleistocene; Nukumaruan; Wanganui Basin; New Zealand
R04015 Received 23 August 2004; accepted 13 May 2005; Online
publication date 27 July 2005
Journal of the Royal Society of New Zealand
Volume 35, Numbers 1 & 2, March/June, 2005, pp 123–150
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