Microcrystalline aragonite from the Bahama Banks was compacted in the laboratory at pressures from 10^-1 to 10⁵ psi. at room temperature; the effects of heating were explored. The important conditions affecting the maximum compaction were total pressure, rate of loading, rate of removal of water, grain-size, and cohesion of grains. Conditions having a minor effect were initial water content, time period of compaction (for periods of more than 3 hours), and temperature (for water-saturated samples).

A new parameter is proposed to characterize compaction: grain proportion (g), which is equal to the volume of grains divided by the bulk volume; g is equal to one minus porosity expressed as a decimal fraction. Grain proportion is a useful index of compaction because it is also the ratio of the dry bulk density to the grain density of the sediment, and thus is a linear measure of the approach to solid rock.

The effect of raising the pressure from 1 psi. to 10⁵ psi. on Bahaman aragonitic sediment is to increase the compaction from g = 0.3 to g = 0.8. Rapid loading of the sediment (at 10⁴ psi./min.) results in differential compaction ranging from g = 0.85 under the moving piston to g = 0.65 at the stationary piston; differential compaction also seems to occur at very slow loading rates (10^-6 psi./min.). Constricted egress of water as the sediment is compressed can reduce the amount of compaction by ^Dgrg = 0.1. Sediment of 1µ median grain-size compacts to g = 0.5 under 500 psi., but sediment of 200µ median grain-size compacts only to g = 0.4 under the same pressure; furthermore, the compacted coarse sediment falls apart, but the fine sediment is r latively coherent.

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