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doi:10.2204/iodp.proc.317.206.2014

Introduction

Integrated Ocean Drilling Program (IODP) Expedition 317 was devoted to understanding the relative importance of global sea level (eustasy) versus local tectonic and sedimentary processes in controlling continental margin sedimentary cycles. Upper Miocene to recent sedimentary sequences were cored in a transect of three sites on the continental shelf (landward to basinward, Sites U1353, U1354, and U1351) and one site on the continental slope (Site U1352) in the Canterbury Basin on the eastern margin of the South Island of New Zealand (see the “Expedition 317 summary” chapter [Expedition 317 Scientists, 2011a]). Obtaining the most accurate age model for the drilled sediments is pivotal for attaining the main goals of the expedition. Shipboard paleomagnetic measurements taken during Expedition 317 had limited success because of a strong, pervasive drilling overprint on the natural remanent magnetization (NRM) because of the use of magnetic core barrels for most of the drilled interval, preventing the unambiguous identification of a characteristic primary component (characteristic remanent magnetization [ChRM]). Shipboard measurements demagnetized the archive section halves to 20 mT but seldom removed the overprint along those intervals. Advanced piston coring with nonmagnetic core barrels produced reasonably good magnetic results. However, these barrels could only be used for the upper 60–70 m for the shelf sites or to ~250 m at the slope site where stiffness of the sediments and/or the presence of coarse-grained material prevented further use. Unfortunately, given the relatively high sediment accumulation rate, the upper part of the interval drilled with nonmagnetic barrels usually comprised only the youngest magnetic polarity magnetozone (the Brunhes Chron), precluding retrieving a sensible magnetostratigraphy downhole. Here, we report on a detailed paleomagnetic study for 764 individual discrete samples from Holes U1351B (water depth 122 m; 131 samples), U1352B/U1352C (water depth 354 m; 485 samples), U1353B (water depth 85 m; 54 samples), and U1354B/U1354C (water depth 113 m; 95 samples) in an attempt to substantiate the nature of the remanence and to evaluate the potential for developing magnetostratigraphic constraints on the chronology of these sediments.

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