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doi:10.2204/iodp.proc.302.203.2009

Introduction

The detrital mineral content of Arctic Ocean sediments is one of the major sources of paleoceanographic interpretations because of the scarcity of biogenic tracers, in particular in the Neogene sediments of central Arctic Ocean cores (e.g., Moran et al., 2006; Backman and Moran, 2008; Darby, 2008; Krylov et al., 2008, and references therein). The Integrated Ocean Drilling Program (IODP) Arctic Coring Expedition (ACEX; Expedition 302) cores are situated below the confluence of the two major surface currents of the Arctic Ocean, the Beaufort Gyre and the Transpolar Drift. Intermediate and deep waters of the Amerasian and Eurasian Basin are separated by the Lomonosov Ridge, which rises >3000 m above the seafloor (Fig. F1) (Rudels et al., 2004; Jakobsson et al., 2008). Previous work has delineated the major source rocks and tracer mineral assemblages that are related to the diverse mineralogy of the circum-Arctic source regions. Figure F1 (Vogt, 1997, with later additions) summarizes early investigations (Belov and Lapina, 1961; Berry and Johns, 1966; Silverberg, 1972; Naugler et al., 1974; Darby, 1975; Clark et al., 1980; Darby et al., 1989; Stein et al., 1994), recent clay (Wahsner et al., 1999; Viscosi-Shirley et al., 2003) and heavy mineral (Behrends et al., 1999) investigations, and the first comprehensive quantification of bulk mineral assemblages (Vogt, 1997).

In general, the Canadian Arctic archipelago is a major source of detritral carbonates and the Putorana flood basalts to the south of the eastern Kara and Western Laptev Sea are the source of a unique smectite, plagioclase, and (clino-)pyroxene mineral assemblage. These regions are also very significant sources of geochemically highly differentiated Fe-oxide mineral assemblages (Darby et al., 2002). Putorana Plateau basalts also produce a unique signal that is detectable in rare earth elements and radionuclide investigations (Eisenhauer et al., 1994, 1999; Tütcken et al., 2002; Haley et al., 2008) as well as in their inorganic geochemistry (Schoster et al., 2000). Investigations of the magnetic properties also traced a specific magnetic mineral assemblage for these basaltic rocks (Kleiber and Niessen, 2000).

Here I extend the initial investigation of the offshore science party to a much higher sample resolution (every few centimeters in the uppermost 60 m, lithologic Unit 1, and between ~190 and 380 meters below seafloor [mbsf], lithologic Units 1/5, 1/6, 2, and 3) (see the “Sites M0001–M0004” chapter for detailed lithology). Although general trends prevailed (cf. the Expedition Reports section of this volume), much higher frequency changes in the mineral assemblage are observed in the extended data set (Fig. F2). Despite the already high number of samples, I hope to increase the sample resolution in the future. I encourage every research group that possesses ground powder samples of ACEX cores to provide us with their sample sets. Samples would not be destroyed and contamination is at a minimum at our laboratory.

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