Parameters controlling acoustic properties of carbonate and volcaniclastic sediments at sites 866 and 869

Abstract

Comparison of the acoustic and index properties with the petrographic character of 125 brine-saturated carbonate and volcaniclastic rocks from Sites 866 and 869 indicates that porosity is the dominant parameter influencing P- and S-wave velocity and acoustic impedance. Porosity in the mid-Cretaceous platform carbonates (Site 866) is controlled by diagenetic alteration, rather than primary depositional texture. Replacement and cementation by dolomite yields the highest acoustic velocities. Similarly, porosity in the volcaniclastics (Site 869) is controlled by diagenetic alteration of components and partial replacement and cementing by zeolite. The density-velocity relationship of the carbonates shows excellent correlation with Gardner's curve for limestone. The carbonates at Site 866 have a considerably wider range of acoustic impedance than the basalt. -from Authors