The Meganos gorge is a large fossil channel of late Paleocene age in the subsurface of the southern Sacramento Valley, California. The gorge fill is predominantly shale whose original volume has been reduced 30-50 percent by compaction. Elongation of overlying units indicates that compaction began immediately after burial. Where the gorge fill is entirely sandstone, there has been no measurable compaction.

If the presence and amount of compaction are not recognized, incorrect interpretations of structure are easy to make. Often nonexistent faults are used to explain anomalously low structural positions for units overlying compacted areas of gorge fill.

At River Break field, several wells show entrapment of gas on an anticlinal structure created by compaction of the gorge fill.

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