(Table 1) Summary of densities and compressional-wave velocities at DSDP Hole 72-516F@en

Compressional-wave velocities were measured in 9 samples from the 18 m of igneous basement penetrated by drilling at Hole 516F. Wet-bulk densities range from 2.50 to 2.92 g/cm**3; compressional-wave velocities (measured at 0.4 kbar confining pressure) range from 4.29 to 6.32 km/s. Because of progressive alteration, compressional-wave velocities in deep-sea basalts tend to decrease with age; velocities in basalts from immediately beneath the sediment/basement contact are consistent with the proposed age (86 ± 4 Ma) of basement at the site. A very strong vertical velocity gradient of 0.126 km/s/m in the 18-m basement interval reflects a marked decrease in the degree of alteration with depth beneath the contact.本数据集针对516F孔钻探揭露的18米火成岩基底（igneous basement）中的9件样品，开展了纵波速度（compressional-wave velocities）测试。样品的湿体密度（wet-bulk densities）区间为2.50~2.92 g/cm³；在0.4千巴围压（confining pressure）条件下测得的纵波速度范围为4.29~6.32 km/s。受递进式蚀变作用影响，深海玄武岩的纵波速度通常随地质年龄增长而降低；取自沉积物-基底接触面（sediment/basement contact）下方紧邻区域的玄武岩样品，其纵波速度与该站位基底的推定年龄（86±4 Ma）一致。在该18米的基底岩芯段内，存在0.126 km/s/m的极强垂直速度梯度（vertical velocity gradient），这反映出接触面下方随深度增加，蚀变程度显著降低。