High Quality Content by WIKIPEDIA articles! The Aquitaine Basin is after the Paris Basin the second largest Mesozoic and Cenozoic sedimentary basin in France, occupying a large part of the country`s southwestern quadrant. Its surface area covers 66,000 km2 onshore. It formed on Variscan basement which was peneplained during the Permian and then started subsiding in the early Triassic. The basement is covered in the Parentis Basin and in the Subpyrenean Basin — both sub-basins of the main Aquitaine Basin — by 11,000 m of sediment.