Late Paleocene pipe swarm in the Great South – Canterbury Basin (New Zealand)

Abstract

We have identified a deeply buried fluid escape pipe province in Cretaceous-late Paleocene sediments of the Great South-Canterbury Basin (NZ). The seismic observations and interpretations point to an unusually vast fossil system of pipes. These features are exceptional in number (>2000 edifices) and appear to have formed from a common root zone. The areal extent of the analysed pipe system (2500 km 2) is among the largest systems of fluid expulsion features ever observed in three-dimensional seismic data. The unclustered distribution of the pipes suggests no specific link to faults or buried sedimentary features and, at their maximum vertical development, the pipes are equally distributed above depocentres or structural highs. The majority of pipes terminate at two discrete levels in the late Paleocene. Based on the geometrical relationship of the pipe edifices to the overburden, and the basinal setting of the hosting units, we interpret these horizons as representing the seabed at the time of pipe formation. This interpretation allows us to date the timing of pipe formation as prominently late Paleocene. We envisage that the pipes originated during discrete episodes of fluid venting in this time interval, disrupting the typical progressive basinal compaction-driven pore fluid expulsion. The pipes are associated with biogenic gas expulsion. We discuss their triggers, mechanical processes, and global significance for understanding fluid flow processes in sedimentary basins.

Late Paleocene CO<sub>2</sub> drawdown, climatic cooling and terrestrial denudation in the southwest Pacific

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Reutilization of fluid flow pathways over 54 million years, offshore New Zealand

“…The seismic data are zero‐phase processed and are displayed with the Society of Exploration Geophysicists (SEG) standard polarity, whereby a downward increase in acoustic impedance (a function of rock velocity and density) corresponds to a positive reflection event (red on seismic profiles) (Brown, 2011). Bertoni et al (2019) report that the vertical resolution of the seismic data is ca. 10 m in the shallow subseafloor between ca.…”

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Structural controls on the location, geometry and longevity of an intraplate volcanic system: the Tuatara Volcanic Field, Great South Basin, New Zealand

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