(Table 1) Potassium, radiogenic Argon 40 and dated age for DSDP Hole 94-608 sediments

K-Ar dates were obtained for three pillow basalt samples recovered from Site 608 (Samples 608-58-1, 103-109 cm; 608-59-1, 3-7 cm; 608-59-1, 48-53 cm). Reliable K-Ar dates cannot be routinely obtained for deep-sea igneous rocks, because they may be subject to inaccuracies related to seawater alteration (Seidemann, 1977, doi:10.1130/0016-7606(1977)88<1660:EOSAOK>2.0.CO;2) and/or the presence of excess radiogenic 40Ar (Dalrymple and Moore, 1968, doi:10.1126/science.161.3846.1132; Dymond, 1970, doi:10.1130/0016-7606(1970)81[1229:EAISBP]2.0.CO;2). Thus, the possibility that the samples dated in this study were subject to these sources of inaccuracy must be evaluated.

(Table 2) Compressional and shear wave velocites from basalts and sediments of the Atlantic and Pacific Ocean

Compressional (Vp) and shear (Vs) wave velocities have been measured to 1.0 kbar for 14 cores of well-consolidated sedimentary rock from Atlantic and Pacific sites of the Deep Sea Drilling Project. The range of VP (2.05-5.38 km/sec at 0.5 kbar) shows significant overlap with the range of oceanic layer-2 seismic velocities determined by marine refraction surveys, suggesting that sedimentary rocks may, in some regions, constitute the upper portion of layer 2. Differing linear relationships between VP and Vs for basalts and sedimentary rocks, however, may provide a method of resolving layer-2 composition. This is illustra ted for a refraction survey site on the flank of the Mid-Atlantic Ridge where layer-2 velocities agree with basalt, and two sites on the Saya de Malha Bank in the Indian Ocean where layer-2 velocities appear to represent sedimentary rock.