Consolidation characteristics and related properties of sediments from experimental mohole (Guadalupe site)

‘Consolidation’ in the geologic sense is the hardening, or lithification, of a sediment; in the field of soil mechanics consolidation refers to the reduction of volume of a sediment under imposed loads. Consolidation tests were run on eleven samples from the Guadalupe Mohole site, including surface samples from gravity cores (taken in the usual manner by lowering a weighted tube from the ship) and cored samples to a depth of 136 m (from the drilling operation). Interpretation of the test curves of these seriously disturbed samples indicates that these deep-sea sediments are stronger than might have been anticipated. They appear capable of supporting overburden pressures without significant reduction of porosity in the depth range studied. Porosities at the sediment surface were about 80%; in situ porosities for the deepest samples were estimated to be about 72%; reduction of no more than 5% owing to overburden pressure is estimated for the deepest sample (168 m). It is concluded that these effects are due to low rates of deposition, great age, and materials which induce interparticle bonds having the nature of chemical cementation.