Sequence stratigraphy of the Nukumaruan Stratotype (Pliocene‐Pleistocene, c. 2.08–1.63 Ma), Wanganui Basin, New Zealand

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. (δ 18 O 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.

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“…There are more such truncated facies associations than there are seismic sequence boundaries, and it is therefore possible that some of the truncated facies associations may represent higher order cycles or autocyclicity related to migration of distributaries and/or shelf depocenters. The facies associations, both complete and truncated, are similar to those known from the Wanganui Basin, between North Island and South Island of New Zealand Saul et al, 1999;Abbott et al, 2005;Naish et al, 2005).…”

“…Though in detail individual cycles display differing sedimentary architectures, which await full description and interpretation, elements of the Castlecliff motif Saul et al, 1999) and the Birdgrove and Maxwell motifs (Abbott et al, 2005) may all be represented.…”

Marine Mollusca of isotope stages of the last 2 million years in New Zealand. Part 3. Gastropoda (Vetigastropoda - Littorinimorpha)

“…comm. August 2003) reported an incomplete spire of S. frazeri in 'shellbed f' (of Abbott et al [2005, fig. 3 Remarks.…”

“…The faunas included in this overview, their ages and their oxygen isotope stage correlations were summarized in Part 1 of this series of papers , modified slightly in the introduction to Part 2 (Beu 2006), and are not repeated here. Once again this work is founded on the seminal works on Wanganui Basin by Fleming (1947Fleming ( , 1953, and much of what the present 'Wanganui Basin working group' has published (particularly Beu , 2006Abbott et al 2005;Naish et al 2005;Pillans et al 2005) is based on Fleming's brilliant foundation. Fleming (1953) listed a number of possibly new taxa in his faunal lists from Wanganui PlioceneÁPleistocene formations, based on material in GNS.…”

Preface

“…The sequence stratigraphy of the Nukumaru Stage (c. 2.08-1.63 Ma) stratotype section at Nukumaru and Ototoka Beaches is described here for the first time by Abbott et al (2005). The authors discuss the characteristics of shallow-marine and marginal to non-marine sequences, and correlate the historically important coastal section into the Wanganui Basin composite cyclostratigraphy.…”