Cavernous Formation 1 : A formation having voluminous voids, usually the result of dissolving by formation waters which may or may not be still present. (Bul D20)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}