The 2,000 m isobath follows more or less the course of the Garonne River and divides the basin into a relatively shallow northern platform, the so-called Aquitaine Plateau, and into a much deeper, tightly folded, southern region.

The evaporites were later activated as diapirs during the Pyrenean orogeny and the mudstones served as decollement horizons along which Triassic sediments were squeezed northwards to the line Arcachon–Toulouse.

The Triassic marine transgression probably invaded the southern Aquitaine Basin from the southeast or from the south (from the Tethys) via the then still immersed Pyrenean region.

Despite smaller regressions during the Pliensbachian towards the end of the Lias and at the beginning of the Dogger the sea had onlapped the basement rocks of the Massif Central and the western Vendée (reaching today's limits) by 30 km.

On this shelf the generally detritic transgression sediments of the Hettangian normally comprise a base conglomerate, arkoses, and fairly thick layers of sand- and mud-stones rich in plant material.

These are followed by ammonite-bearing (Amaltheus margaritatus) and oyster-bearing (Gryphaea cymbium) marls indicating a shelf environment open to the spreading Atlantic Ocean.

The third and last sequence of the Lias sets in during the Lower Toarcian without any detrital deposits at its base, the sediments being black ammonite-bearing marls (with Harpoceras falciferum and Hildoceras bifrons).

Interlayered with these sandy limestones are oyster beds, iron oolite and gypsum layers; they contain ammonites like Pleydellia aalensis and Leioceras opalinum.

In the western domain open towards the Atlantic, the pelagic sediments comprise ammonite-bearing limy marls very rich in filamentous microfossils (bryozoans).

Laid down are breccias and the sediments also show synsedimentary reworkings; periodically interbedded limestones and marls carrying lignite horizons begin to form.

During the Tithonian, iron-bearing calcareous oolites interbedded with marls, as well as dolomite and border facies deposits develop—dated by Gravesia portlandicum.

Since the onset of the Albian, strong halokinetic movements affect the southern Aquitaine Basin and in turn profoundly influence sedimentation patterns.

At the same time, the sediments on the Aquitaine Plateau farther north are folded into gentle wavetrains following the Hercynian strike (northwest-southeast).

In the remainder of the Aquitaine Basin, mainly pelagic limestones (chalk facies) are sedimented during the Upper Cretaceous, including the type localities for the Coniacian, Santonian, and Campanian in the Charente.

After the initial deposition of bioclastic rudist-bearing limestones and the formation of some reef complexes composed of rudists and single corals, the sea level started dropping.

In the Lower Eocene (Ypresian), another transgressive period saw the sea advance north into the Médoc and south of Oléron; in the southeast it even reached the Montagne Noire.

The detrital sediments with provenance from the meanwhile strongly eroded Massif Central (muds, sands, gravels) then affected only a small fringe zone in the northeast.

In the Médoc, nummulite-bearing marls and limestones were still being laid down, but east of Bordeaux already continental molasses appeared that change farther south into gypsum-bearing formations.

During the Lower Oligocene (Rupelian), a permanently marine environment persists in the south with marls and sands rich in nummulites, lamellibranchs, and echinids.

After a short-lived advance at the beginning of the Chattian with seastar-bearing limestones in the northern Médoc and in the Libournais and with mammal-bearing molasses in the Agenais, the sea made a big retreat at the end of the Oligocene.

They pushed the surrounding belt of lakes ahead of them (in northerly directions) thereby spreading lacustrine limestones well into the Quercy, onto the Causses, and even onto the Massif Central.

The drainage system of the Garonne already resembled more or less today's pattern, the river avoiding the Miocene gravel accumulations as much as possible and then following between Toulouse, Agen and Bordeaux a weekly subsiding graben.

As a consequence several peneplanations were carved out from the detrital alluvial plains: On the pliocene peneplain, today's drainage system was firmly established.

The structures were formed during several tectonic phases: The Southern Province is characterised by the deep Parentis and Adour sub-basins with the Mimizan high ground in between.

Similar to the Northern Province, the major structures are again trains of parallel anticlines whose wavelength steadily diminishes approaching the Pyrenean front.

The following anticlines can be distinguished (from north to south): Isostatic movements during the Plio-Quaternary at the northeastern edge of the Aquitaine basin lead to an uplift and rejuvenation of the peneplained basement in the Massif Central.

This in turn has a strong effect upon the hydrographic network, for example in the drainage basins of the Garonne and Adour, the rivers' courses were changed or entirely abandoned.

Tectonic movements are still at work in the Aquitaine Basin today—strong earthquakes in the Pyrenees (with destroyed villages and churches) and somewhat milder tremors near the island of Oléron keep reminding us of that fact.

Two geodynamic developments are of primordial importance for the basin: In the Upper Triassic (Carnian) about 230 million years ago, the supercontinent Pangaea started slowly to break up.

Within the context of the opening of the Bay of Biscay, the Parentis Basin can furthermore be regarded as a failed attempt of the Atlantic to wedge into the continent's interior.