Resumen de Las formaciones esponjiolíticas del Dogger de la región Vasco-Cantábrica:: Características y posibilidades petrolíferas

S. Quesada, Victoriano Pujalte Navarro, Sergio Robles Orozco, José C. Vicente Bravo

• Siliceous sponges occur in the western Basque-Cantabrian region at two stratigraphic intervals: at the Lower Bajocian they appear in small mounds (less than 1 m.) isolated within a predominantly mar//limestone succession; an at the Upper Bajocian (Parkinsoni Biozone) as larger bioherms and biostromes, within an extensive carbonate plat form. The latter is up to 20 m. thick and a better hydrocarbon target than the Lower Bajocian mounds, mainly as fractured reservoirs. An example is described where local tectonics have determined a pervasive fracturation of these rocks, thus creating an important secondary porosity.