Secondary compaction after secondary porosity: can it form a pressure seal?

Petrographic analysis of sandstones from the vicinity of a pressure seal (transition from normal to overpressure) at 5.5-km depth in the lower Tuscaloosa Formation in Louisiana documents local, high porosity above and below the seal. Packing analysis shows that compaction is greater in normally pressured, high porosity sandstones than in overpressured, high-porosity sandstones; compaction in overpressured, high-porosity sandstones is similar to that in normally pressured, well-cemented sandstones. We propose that focused corrosive fluids created a zone of high secondary porosity, allowing further compaction that we call "secondary compaction'. -from Authors