Print this page
Donald R. Lowe1
(1) Stanford University, Stanford, CA
Abstract: Sediment texture and flow processes as interactive controls on the architecture and properties of deep-water deposits with examples from the Britannia Formation (Lower Cretaceous), North Sea
Although many small-scale features of deep-water deposits are clearly related to the processes of sedimentation, the relationship between process and large-scale properties is often less obvious. However, sediment properties and deposit architecture from microscopic to seismic scales can be related directly to available sediment supply and flow and depositional mechanics. Many large-scale components of deep-water systems, such as channel-levee complexes and meandering channels, develop only where flows are turbulent. Flow mechanics and sediment size also control the locus of sedimentation relative to topography and the lateral extent and geometry of sand bodies. The Britannia Formation (Lower Cretaceous), North Sea, is a major deep-water gas reservoir. Thicker-bedded units range from clean, dish-structured sandstones (HDTs), deposited by high-density turbidity-currents, to muddy, complexly-structured sandstones interpreted to represent slurry flows transitional between turbidity currents and debris flows. Mud-matrix-supported sandy mudstones are the deposits of true debris flows. Clean HDTs and HDT-dominated packages are commonly lenticular and appear to represent channel-fill or lobe-like canyon- or channel-mouth bodies. They are excellent reservoirs but predicting geometry and lateral relationships is difficult. Slurry-flow deposits are sheets that show no evidence for the existence of organized channels or levees, but exhibit regular downslope size grading. They are good gas reservoirs and reasonably predictable laterally. Muddy debris flows were less mobile than either turbidity currents or slurry flows, and their deposits are poor reservoirs, restricted laterally, and lack internal organization.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana