TY - SER ID - oregan2007cpah T1 - Consolidation properties and hydraulic conductivities of sediments from ODP Leg 207 sites AU - O'Regan, Matthew AU - Moran, Kate PY - 2007 T2 - Supplement to: O'Regan, M; Moran, K (2007): Compressibility, permeability, and stress history of sediments from Demerara Rise. In: Mosher, DC; Erbacher, J; Malone, MJ (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 207, 1-35, https://doi.org/10.2973/odp.proc.sr.207.114.2007 PB - PANGAEA DO - 10.1594/PANGAEA.776075 UR - https://doi.org/10.1594/PANGAEA.776075 N2 - The stress history, permeability, and compressibility of sediments from Demerara Rise recovered during Ocean Drilling Program Leg 207 were determined using one-dimensional incremental load consolidation and low-gradient flow pump permeability tests. Relationships among void ratio, effective stress, and hydraulic conductivity are presented for sampled lithologic units and used to reconstruct effective stress, permeability, and in situ void ratio profiles for a transect of three sites across Demerara Rise. Results confirm that a significant erosional event occurred on the northeastern flank of the rise during the late Miocene, resulting in the removal of ~220 m of upper Oligocene-Miocene deposits. Although Neogene and Paleogene sediments tend to be overconsolidated, Cretaceous sediments are normally consolidated to underconsolidated, suggesting the presence of overpressure. A pronounced drop in permeability occurs at the transition from the Cretaceous black shales into the overlying Maastrichtian-upper Paleocene chalks and clays. The development of a hydraulic seal at this boundary may be responsible for overpressure in the Cretaceous deposits, leading to the lower overconsolidation ratios of these sediments. Coupled with large regional variations in sediment thickness (overburden stresses), the higher permeability overpressured Cretaceous sediments represent a regional lateral fluid conduit on Demerara Rise, possibly venting methane-rich fluids where it outcrops on the margin's northeastern flank. ER -