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Compaction Band Spacing - Bed Thickness Scaling

Compaction band spacing shows a significant variation from a few millimeters to several meters. For example, Figure 1 shows a rather narrow spacing on the order of a few millimeters or centimeters across thin beds or sequence of thin beds of Aztec sandstone outcropping out near the Willow Tank locality at Valley of Fire State Park, Nevada (see 'Fractures in Valley of Fire, Nevada, USA' under case studies for the location). Analogous to the joint spacing-bed thickness relationship of the bed-confined joints (see the link for 'Joint Spacing - Layer Thickness Scaling' and 'Mechanisms and Mechanics of Joint Sets') roughly a similar ratio appears to exist for the compaction bands and the cross beds or in some cases amalgamated sequence of cross beds as seen in the photograph of a steep erosional surface in Figure 2. Click on the image to enlarge it so that it will be easier to observe bed-bounded compaction bands and their spacing.

A set of deformation bands with remarkably narrow spacing in thinly bedded Aztec sandstone exposed on the southern extension of the geomorphic feature identifying the Willow Tank at Valley of Fire State Park, Nevada.Figure 1. A set of deformation bands with remarkably narrow spacing in thinly bedded Aztec sandstone exposed on the southern extension of the geomorphic feature identifying the Willow Tank at Valley of Fire State Park, Nevada.
Compaction band (cb) single set confined into single beds in Aztec Sandstone, about 500 meters west of the Silica Dome, Valley of Fire State Park, Nevada. Note that the bands are nearly perpendicular to the bed interfaces and their spacing is roughly proportional to the thickness of the bed in which they occur. There are also at least two shear bands (sb, white double arrows) which are diagonal to the beds and cut and offset them. These are not the focus of this section, but they are pointed out for completeness. George Chittenden who is about 6' tall for scale.Figure 2. Compaction band (cb) single set confined into single beds in Aztec Sandstone, about 500 meters west of the Silica Dome, Valley of Fire State Park, Nevada. Note that the bands are nearly perpendicular to the bed interfaces and their spacing is roughly proportional to the thickness of the bed in which they occur. There are also at least two shear bands (sb, white double arrows) which are diagonal to the beds and cut and offset them. These are not the focus of this section, but they are pointed out for completeness. George Chittenden who is about 6' tall for scale.


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