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doi:10.2204/iodp.proc.338.204.2016

Introduction

Lithic grains are polycrystalline particles that can in many cases be identified as belonging to specific parent lithologies. Although monocrystalline grains may have internal textures (e.g., Bernet and Bassett, 2005; Lee et al., 1998), the provenance information in monocrystalline grains (quartz, feldspar, and dense minerals) is primarily derived from their composition, which for feldspars and dense minerals can be modified by dissolution and replacement during diagenesis (e.g., Milliken and Mack, 1990; Milliken, 1988; Morton, 1984). Grain ratios (e.g., quartz-feldspar-lithic fragments) are also subject to control by grain size (Ingersoll et al., 1984), a factor that is not fully removed even by the Gazzi-Dickinson point-count technique that extracts large monocrystals from lithic grains (Milliken et al., 2012; Decker and Helmold, 1985). In lithic fragments themselves, however, provenance information resides mostly in their textures, which are less subject to postdepositional alteration (Milliken, 1988) and unaffected by grain size once a grain is sufficiently large to preserve the texture. Lithic grains are “recognizable fragments of the source terrane” (Decker and Helmold, 1985) and as such constitute an easily accessible and exceptionally reliable type of information on sediment source. Survival of lithic grains during sediment transport is favored in far-distal sands that avoid reworking in coastal depositional systems (Dutton and Loucks, 2010).

The atlas presented here intends to serve as a reference for the lithic grain types observed within the sand-size (62 µm to 2 mm) grain fraction of the Kumano Basin and underlying Nankai accretionary prism. Our grain identifications draw on materials presented in several published petrography resources (Usman et al., 2014; Fergusson, 2011; Milliken et al., 2007; Underwood and Fergusson, 2005; Fergusson, 2003; Garzanti and Vezzoli, 2003; Marsaglia, 1992; Marsaglia et al., 1992; De Rosa et al., 1986; Taira and Niitsuma, 1986; Scholle, 1979).