Empirical models of the ocean-sediment and marine sediment-bedrock density contrasts

We utilize empirical density models of the seawater, marine sediments and bedrock to evaluate the ocean-sediment and (marine) sediment-bedrock density contrasts. The depth-dependent seawater density model and a density model of the upper sedimentary layer are used in computing the ocean-sediment density contrast. A definition of the sediment-bedrock density contrast with respect to the average bedrock density is based on applying the marine sediment density model. Density samples from the Deep Sea Drilling Project are used to establish the density model of marine sediments and to estimate the average bedrock density. The marine sediment density model describes the density distribution within the upper sedimentary layer as a function of the ocean-floor depth, while the increasing sediment density due to compaction is defined as a function of the sediment depth. The depth-dependent seawater density model was derived based on the analysis of oceanographic data from the World Ocean Atlas 2009 and the World Ocean Circulation Experiment 2004. The predicted values of both density contrasts are compiled on a 5×5 arc-min geographical grid for the world’s oceans and marginal seas. The ocean-sediment density contrast varies between 0.05 and 0.63 g/cm³. The maximum density contrast is predicted beneath marginal seas due to the accumulation of heavier sediments near coast. Transportation of fine and light particles at long distances results in decreasing density contrast between the seawater and the underlying deep-ocean sediments. The sediment-bedrock density contrast varies between 0.00 and 1.70 g/cm³. The most enhanced density contrast between the marine sediments and the underlying bedrock is predicted beneath thin sedimentary layers, while the density at the lowermost stratigraphic units of thick sedimentary accumulations is similar to the bedrock density due to sediment compaction (and further lithification).