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The goal of the decision tree is to use composition and texture data from smear slide analysis, core photos, and knowledge of the water depth and distance from land of cored sites on the seafloor to determine the lithologic name of the sediment. The decision tree aims to capture the most distinctive (i.e. end‐member) lithologies of marine sediments. These are:

 Calcareous ooze: biogenic sediments composed of calcareous nannofossils and/or foraminifera.

 Siliceous ooze: biogenic sediments composed of diatoms, radiolarians, sponge spicules, and/or silicoflagellates.

 Red clays: very fine terrigenous sediment that often contains siliceous microfossils, fish teeth, Mn–Fe micronodules, and/or volcanic glass.

 Terrigenous sediment: sediment from the weathering of continents or volcanic islands.

 Glaciomarine sediment: sediment containing terrigenous sand, pebbles, or cobbles transported to the sea by icebergs.

Note, while the above five marine sediment lithologies are the most distinctive sediment types, mixed lithologies are common (Mazzullo and Graham, 1988). In addition, the lithologies can also change within a core. For example, the sediment could alternate between red clay and siliceous ooze, or gradually change from one to another. In any marine sediment lithology, but especially in biogenic oozes and deep‐sea red clays, layers of volcanic ash may be distinguishable, as a minor lithology.

TABLE 2.2. Smear slide composition and textural data, plus presence/absence of pebbles on core surface. A copy of this table in Excel format can be found in the online Supplemental Resources.