Henry W. Posamentier1
(1) Veritas Exploration Services, Calgary, AB
ABSTRACT: On the Role of Flow Stripping and the Deposition of Channel Levees and Frontal Splays in Deep-Water Systems; Evidence from 3D Seismic Data
Flow stripping is the process by which the upper part of a turbidity flow is stripped off the main body, a process which commonly occurs at channel bends. The part of the flow that escapes the channel is the dilute or low-density, mud-rich part of the flow. The abrupt change from confined to unconfined flow as the upper part of the flow leaves the channel results in rapid sedimentation at and near the levee crest. Sediment waves are commonly observed at the top of, as well as within proximal levee deposits, suggesting that flow stripping and the construction of such waves are integral to the formation of this depositional element.
As a turbidity flows travel downsystem along a leveed channel, repeated flow stripping along its course results in a progressive impoverishment of mud within the flow. One consequence of this process is that the sediment budget available for levee construction decreases leading to a progressive decrease in levee height downsystem. Another consequence of flow stripping is the progressive increase of the sand to mud ratio within the overall flow down-system.
With distance down-system, levee height (above the channel floor) and height of the high-density column within the flow decrease; however, the levee height decreases at a more rapid rate. Where the height of the high-density column approaches the height of the levee, the levee walls are no longer efficiently able to confine the sand-prone part of the flow. At this transition, the leveed channel gives way to a multitude of smaller channels as the system splays out across the slope or basin floor. These channel complexes, characterized by a distributary or braided pattern, can form depositional lobes.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado