New Zealand Journal of Geology and Geophysics abstracts

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Foreword

If there was any doubt that western science and religious belief are still as tightly intertwined as they were in the days of Copernicus, a cursory reading of current literature surrounding the Cretaceous/Tertiary (K/T) boundary debate will lay that doubt to rest. In the third millennium, heated argument continues between fervent catastrophists and battle-hardened uniformitarians: did a giant asteroid wipe out the dinosaurs and half of all life on Earth 65 million years ago, or was the impact the coup de grâce after long-term climatic cooling? Both camps have recently presented new data and cogent, yet distinct interpretations in support of their long-held positions (e.g., Koeberl & MacLeod 2002; Remane & Adatte 2002).

Since the ground-breaking discoveries of Percy Strong, Robert Brooks, and colleagues that identified the K/T boundary layer in several South Island localities, New Zealand has been recognised as a crucial area to test K/T boundary theories. Being far from the favoured Yucatan impact site, New Zealand provides a key test for global distribution of fallout and, importantly, the global effects of the impact on biological systems. The papers in this special issue represent the latest phase of K/T boundary research in New Zealand. They are by no means the last word on the subject but they do mark an important threshold. Previously, and on the basis of relatively meagre data, many of us were lazily confident that the New Zealand record conformed to our preferred K/T boundary scenario. The wealth of new data presented in these papers has knocked this confidence by calling into question many assumptions, including the stratigraphic completeness of key K/T boundary records and the isochroneity of biostratigraphic events, as well as the perception that the latest Cretaceous was a time of tectonic quiescence and stable climatic conditions. But such is the nature of science. When there are few data, we tend to interpret them from the comfort of an established paradigm. Such paradigms only get challenged when contradictory data become too numerous to ignore. You could say that those of us engaged in K/T boundary research in New Zealand have moved from being uncertainly confident to being confidently uncertain!

Most of the papers in this special issue present research findings of a 1998-2001, Marsden Fund programme, Profiling mass extinction: the K/T event from swamp to deep ocean. The programme's aim was to identify local environmental changes associated with the K/T boundary catastrophe across a range of environments, and, by doing so, determine the overall impact of the boundary event on Southwest Pacific biological and physical systems. A major focus was the comparatively well studied, bathyal K/T boundary sections in southeastern Marlborough, which represent the deepest part of the continental margin transect. The scene is set by Crampton et al. who establish the paleogeographic setting of these sections within the Marlborough paleo-embayment. Hollis et al. present paleoenvironmental interpretations of lithofacies and biofacies trends in four of the sections: Flaxbourne River and Woodside Creek sections in coastal Marlborough, and the more siliceous Mead and Branch Stream sections in the Clarence valley. Su et al. use the large Flaxbourne River dataset to demonstrate the value of wavelet analysis to evaluate trends in paleoenvironmental proxies. Field & Hollis highlight the potential for using field-based gamma-ray measurements to identify Milankovitch-scale cycles in the pelagic Marlborough sections as well as in siliciclastic sections, such as at mid Waipara, North Canterbury.

The neritic mid-Waipara section is the focus of two studies. Hollis & Strong review the foraminiferal biostratigraphy and present new records of radiolarians that improve age control for previous sample collections. Vajda & Raine show that the mid-Waipara terrestrial palynomorph record corroborates their earlier findings, based on the terrestrial Moody Creek Mine section, that the K/T boundary event caused abrupt disruption to New Zealand forest communities (Vajda et al. 2001). Kennedy places this disruption in context by presenting an overview of leaf fossil-based climatic trends through the Late Cretaceous and Paleocene in New Zealand. Laird et al. round off the studies of marine sections by showing that the comparatively little studied marine K/T boundary succession at Tora, southeast Wairarapa, contains evidence for major sea-level fluctuations during the Late Cretaceous and early Paleocene.

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