Tangaroa TAN1312 Voyage Report : dredging Reinga and Aotea basins to constrain seismic stratigraphy and petroleum systems (DRASP), NW New Zealand

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Bache, F.; Sutherland, R.; Mortimer, N.; Browne, G.H.; Lawrence, M.J.F.; Black, J.A.; Flowers, M.; Rouillard, P.; Pallentin, A.; Woelz, S.; Wilcox, S.; Hines, B.; Jury, S.; Roop, H. 2014 Tangaroa TAN1312 Voyage Report : dredging Reinga and Aotea basins to constrain seismic stratigraphy and petroleum systems (DRASP), NW New Zealand. Lower Hutt, N.Z.: GNS Science. GNS Science report 2014/05 136 p. + 1 CD

Abstract: The DRASP (Dredging Reinga and Aotea basins to constrain seismic Stratigraphy and Petroleum systems) project is part of a New Zealand government initiative to obtain broader understanding of our marine estate. The specific project goal of DRASP is to understand submarine geology of the region 100 to 500 km west of Northland: how has plate tectonics shaped and moved New Zealand, how has New Zealand’s environment changed through time, what is the composition of sediment layers that record this history, and does the region host natural resources? Samples of deeply-buried strata are usually only possible to obtain with expensive drilling, but Reinga and Aotea basins have a folded and eroded geological configuration that has resulted in a wide variety of rocks being exposed on the seabed. Our working hypothesis is that Eocene to Miocene contractional tectonics exposed Cretaceous to Eocene sedimentary rocks and older basement rock. Uplift followed by subsidence resulted in younger limestone deposition and clastic sediments that are derived from New Zealand or nearby submarine ridges. Volcanism may have been associated with development of the Tonga-Kermadec subduction zone. Over an 18 day voyage (TAN1312) on RV Tangaroa (1-17 November 2013) we collected multi-beam swath bathymetry, gravity and magnetic data, attempted two gravity cores, and used a steel rock dredge with a 0.45 x 1.2 m mouth to collect seabed samples from 45 locations. We successfully removed approximately 2 m3 of rock in total from 38 localities. Most samples collected were limestones, sandstones or mudstones, with a few basalts, greywackes and granite pebbles. Provisional interpretation indicates a match of many of these samples with strata exposed onshore New Zealand. This report documents our activities and provides a preliminary description of the rock samples and bathymetric data we collected. (auth)