Deep drilling results of Leg 47b (Galicia Bank area) in the framework of the early evolution of the North Atlantic Ocean

• Published in: Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 1980
• Subjects: North Atlantic
• Online Access: http://dx.doi.org/10.1098/rsta.1980.0011; https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.1980.0011

Lithologic and stratigraphic evidence from D.S.D.P. Site 398 (3910 m water depth, 1740m total penetration) and regional seismic reflexion data are placed in the context of the early tectonic evolution of the North Atlantic ocean. The morphology of the western Iberian continental margin is the result of two main tensional episodes dated Permo— Lias and Upper Jurassic - Lower Cretaceous, during which the initial basins between Grand Banks and Iberia were created by subsidence and tilting of continental blocks. A limited oceanic opening had probably occurred in Jurassic time between these two tensional episodes. There was no relative motion during Lower Cretaceous between North America and Iberia. One of the main results is that the 398 drillhole penetrated into the basement structure of a tilted block of the continental margin. Borehole data indicate an Uppermost Aptian age for the end of the Upper Jurassic - Lower Cretaceous tensional episode at the level of the site. The subsequent beginning of sea floor spreading in the Uppermost Aptian is associated with a change of sedimentary facies from graded sequences interbedded with slump beds or debris flows to dark, detritic shales. The continental margin had subsided on a regional scale since this time.