Print this pageControls on Internal Stratigraphy of Incised Fluvial Systems: Examples From Valleys in Southwestern Kansas
LEIGHTON, VAN L.
Reservoir stacking patterns in incised valleys are widely believed to be a function of relative base level rise. However, other factors must be considered. Incised valleys of southwestern Kansas provide excellent examples illustrating the interplay between relative base level rise and other possible controls including climate1 tectonics, bedrock geology and valley order within the drainage basin network.
Relative base level rise generally produces vertically aggrading stratal stacking patterns as valleys back-fill. In contrast, fluvial sandstones deposited during sea level lowering or lowstand are sometimes characterized by multiple episodes of deposition followed by incision.
In fields with sufficient well control, the nature of the valley-filling sediment package can be defined. Fluvial sandstones deposited during base level lowering or lowstand are more commonly preserved in wide valleys than in narrow valleys in which later erosive events largely destroy the earlier sequences. In those narrow valleys, back-filling or vertically aggrading reservoirs ultimately are more likely to be preserved. A knowledge of valley morphology can therefore provide hints as to internal stratal stacking patterns, and can impact exploration and development strategies and success.