Figure F7. Plot of cosmogenic ¹⁰Be vs. depth below seafloor at Site 1040. Produced by cosmic rays in the atmosphere and decaying with a 1.5-m.y. half-life, measurable ¹⁰Be enrichments are seen in sediments younger than 7–10 Ma. The underthrust sediments beneath the décollement (blue and purple) have high values typical of the incoming sediment section. Throughout the prism sediments of the upper plate, ¹⁰Be concentrations are very low, typical of sediments that are older than 3–5 Ma. Biostratigraphic (triangles) and magnetostratigraphic (x's) ages as well as sedimentation rates from Leg 170 cores (Kimura, Silver, Blum, et al., 1997) are shown on the right.