HR: 1340h
AN: T53C-1444    [Abstracts]
TI: Porosity modification during and following deposition of deep-water sediments
AU: * Butler, R W
EM: butler@earth.leeds.ac.uk
AF: University of Leeds, School of Earth and Environment, Leeds, LS29JT United Kingdom
AU: McCaffrey, W D
EM: wdm@earth.leeds.ac.uk
AF: University of Leeds, School of Earth and Environment, Leeds, LS29JT United Kingdom
AU: Haughton, P
T53C-1444 AF: University College Dublin, Dept of Geology, Belfield, Dublin, 4 Ireland
AU: del Pino Sanchez, A
T53C-1444 AF: University of Leeds, School of Earth and Environment, Leeds, LS29JT United Kingdom
AU: Barker, S
T53C-1444 AF: University of Leeds, School of Earth and Environment, Leeds, LS29JT United Kingdom
AU: Hailwood, E
T53C-1444 AF: Coremagnetics, The Green, Sedbergh, LA105JS United Kingdom
AU: Hakes, B
T53C-1444 AF: Britannia Operator Ltd, Royfold House, Hill of Rubislaw, Aberdeen, AB15 6GZ United Kingdom
AB: Deposition and early burial of sediments, especially sandy turbidites, are commonly accompanied by the reorganization of porosity structure through the localized expulsion of interstitial fluid. Fluid escape structures are preserved as thin sheets and pipes. Coeval sediment remobilization may be represented by shear structures, commonly taken to indicate down-slope creep and slumping. The history of shearing vs dewatering may be established from cross-cutting structures preserved in outcrop and/or core. Although these relationships are known for gravity-driven soft-sediment deformation on submarine slopes, they can also develop during deposition itself due to shear from the over-riding flow. Such deformation features, including pseudo s-c fabrics and distributed shear, together may previously have been misinterpreted as indicators of palaeoslope (slumps) or even of tectonic deformation. Progressive aggradation of sandy turbidites can show complex banded facies within which soft-sediment deformation is tiered. Syn-deposition micro-growth strata testify to ongoing seabed deformation occurring beneath active flows, while the bedforms themselves provide direct measurements of the magnitude of shear stresses imparted into the seabed and estimates of the shear strength of this substrate. Such banded facies may be interpreted in terms of cyclic partitioning of shear stress into the flow and the substrate. The modified porosity structures and related heterogeneities in permeability of such materials may persist during deeper burial, influencing the rheology of the sediment. These bed-scale processes are reflected in the quality and flow rates of hydrocarbon reservoirs. The reorganization of sand-body architecture through remobilization, by traction and/or down-slope failure, also has a strong impact on the permeability on the multi-bed scale (10s-100s m). Examples will be presented from hydrocarbon reservoirs in the subsurface and from outcrops of Tertiary turbidites in the Alpine-Apennine orogenic system.
DE: 1862 Sediment transport (4558)
DE: 3022 Marine sediments: processes and transport
DE: 3070 Submarine landslides
DE: 8025 Mesoscopic fabrics
DE: 8169 Sedimentary basin processes
SC: Tectonophysics [T]
MN: Fall Meeting 2005