Seismically-derived porosity of deep-sea sediments over the last 74 Ma in the equatorial Atlantic Ocean: Implications for paleo-climate

Deep-sea sediments record the geological and climate history of the Earth. The seismic properties of these sediments, namely the P- and S-wave velocities, depend on their chemical compositions, grain size, age and depth of burial, which, in turn, influence the porosity. We use multichannel seismic reflection data to estimate the sediment thickness and P-wave velocity over 4-74 Ma old oceanic crust on the African Plate and 3-27 Ma old crust on the South American Plate in the equatorial Atlantic Region. We then use the P-to-S converted waves from the basement-sediment interface recorded by 69 multi-component ocean bottom seismometers to determine the P- and S-wave velocity ratios ([Formula presented]) over 3 to 74 Ma. We find that the [Formula presented] decreases from 8.9 ± 2.0 at 3 Ma to 5.0 ± 1.0 at 17 Ma but abruptly increases to 19.5 ± 2.8 at 37.5 Ma. Then, it gradually decreases for crustal ages >37 Ma, reaching 7.0 ± 0.3 at 74 Ma. These variations are almost symmetric across the M...