Consolidation, effective stress, and fluid pressure of sediments from ODP Site 1073, US mid-Atlantic continental slope

Abstract

Fluid pressure interpreted from uniaxial consolidation tests equals 80% of the overburden (total) stress in Pleistocene mudstones at Ocean Drilling Program (ODP) Site 1073 of the US mid-Atlantic continental slope, offshore New Jersey. The fluid overpressure decreases effective vertical stress and preserves void ratio (e) greater than 0.8 in Pleistocene sediments. Overpressure in Oligocene–Miocene sediments is lower even though e is high. Cementation preserves high void ratio of Oligocene–Miocene sediments and therefore the void ratio does not record overpressure and low effective vertical stress. Sedimentation-flow models simulate overpressure and high void ratio in the Pleistocene sediments when fluid flow is coupled with sediment loading at ODP Site 1073. Lateral fluid migration is interpreted to be focused in the Oligocene–Miocene sediments, which are 2.5 times more permeable than the overlying Pliocene–Pleistocene mudstones. The lateral flow provides fluids to ODP Site 1073 to maintain high void ratio, high overpressure, and low effective vertical stress.