Neptunian dykes and associated features in southern Spain: mechanics of formation and tectonic implications

Neptunian dykes and sills in Jurassic carbonate platform strata of the Betic region of Spain occupy spaces created by wholly mechanical fracturing and displacement of the host strata, and later filled by pelagic sediments from above or by precipitation of calcite from circulating solutions. In some places, joint-bounded blocks of platform carbonates have been wholly removed, possibly by sliding down submarine slopes, leaving a staircase topography, commonly Fe-encrusted, that was subsequently filled by pelagic sediments. Other cavities that formed during Cretaceous times were developed by dissolution and current erosion in moderately deep submarine environments, and then filled by pelagic sediments from above. None of the cavities hosted by either platform or pelagic strata contain evidence for their formation by dissolution in a subaerial environment. The Jurassic and Cretaceous history of subsidence of the Betic margins is thus simpler than in versions requiring repeated emergence to form subaerial karstic cavities.