O'Regan, A. Matthew; Moran, Kate (2007): Compressibility, permeability, and stress history of sediments from Demerara Rise. Texas A&M University, Ocean Drilling Program, College Station, TX, United States, In: Mosher, David C., Erbacher, Jochen, Malone, Mitchell J., Berti, Debora, Bice, Karen L., Bostock, Helen, Brumsack, Hans-Juergen, Danelian, Taniel, Forster, Astrid, Glatz, Christine, Heidersdorf, Felix, Henderiks, Jorijntje, Janecek, Thomas R., Junium, Christopher, Le Callonnec, Laurence, MacLeod, Kenneth G., Meyers, Philip A., Mutterlose, H. Joerg, Nishi, Hiroshi, Norris, Richard D., Ogg, James G., O'Regan, A. Matthew, Rea, Brice, Sexton, Philip, Sturt, Helen, Suganuma, Yusuke, Thurow, Juergen W., Wilson, Paul A., Wise, Sherwood W., Jr., Proceedings of the Ocean Drilling Program; scientific results; Demerara Rise; equatorial Cretaceous and Paleogene paleoceanographic transect, western Atlantic; covering Leg 207 of the cruises of the Drilling Vessel JOIDES Resolution; Bridgetown, Barbados, to Rio de Janeiro, Brazil; sites 1257-1261; 11 January-6 March 2003, 207, georefid:2007-087734

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 approximately 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.
West: -54.4400 East: -54.1100 North: 9.2800 South: 9.0200
Expedition: 207
Site: 207-1257
Site: 207-1258
Site: 207-1259
Site: 207-1260
Site: 207-1261
Data access:
Provider: SEDIS Publication Catalogue
Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=10.2973/odp.proc.sr.207.114.2007 (c.f. for more detailed metadata)
Data download: application/pdf
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