Aquitaine Basin

The Aquitaine Basin is named after the Paris Basin, the second largest Mesozoic and Cenozoic sedimentary basins of France. The 66,000 -square-mile basin is above the eroded during the Permian Variscan basement, which gradually began to sink since the Triassic. In the Parentis Basin and in Subpyrenäenbecken, the basement is hidden at its lowest point under a Sedimentauflast of 11,000 meters.

4.1 tectono - metamorphic zones of the basement
4.2 Moho depths

5.1 Mega sequences

6.1 hydrocarbons
6.2 groundwater
6.3 Other Resources

Geographical breakdown

The Aquitanian basin, named after the region of Aquitaine, has roughly the shape of a funnel, the opening to the west is the straight, long in about 330 kilometers north-south running Atlantic coast. Its southern boundary is at about 350 kilometers east-south -west to north-west - trending Pyrenees. In the southeast, the basin extends into the Détroit de Carcassonne between Montagne Noire in the north and in the south Mouthoumet until shortly before Narbonne, where it is run over by Pyrenees ceilings. The northeastern subsequent arc-shaped framing is made of the Massif Central. In the threshold region of the maximum of 100 km wide Seuil du Poitou in the north there is a connection to the adjacent Paris Basin. In the far north the basin is limited to approximately 110 kilometers in east-west direction from the Vendée, the southernmost foothills of the Armorican Massif.

Basin structure

The Aquitaine Basin is a highly asymmetrically constructed foreland basin. Its deepest point of 11,000 meters is located in the immediate vicinity of Nordpyrenäenüberfahrung.

The 2000 m isobath approximately follows the course of the Garonne River and divides the basin into a shallow plateau region in the north ( the so-called Aquitanian plateau ) and in a deep, tightly folded area. The tabular plateau in the north has only a greatly reduced sedimentary sequence with long-wave Faltenbau and occasional disturbances. The folded area in the south shows since the Early Triassic subsidence, the degree of deformation increases in this direction Nordpyrenäenüberfahrung increasingly, also still occurs a strong salt tectonics ( diapirs ) added.

A deviation in this somewhat simplified scheme represents the Parentis Basin on the Atlantic edge dar. Also the Parentis Basin reached the impressive depth of 11,000 meters. It forms a symmetrical Einmuldung that draws from the Golfe de Gascogne from the direction of Arcachon and seaward already partially 100-95 million year old ( Cenomanian ) of oceanic crust underlain. It is possible that here is a pull- apart basin at a cross to the Continent, long-lasting Transform fault with dextral shear component.

Sedimentary development

The words used to sedimentary sequence and their widths are based on over 70 exploration wells that occasionally encountered, the basement only to over 6000 meters.

The sedimentary development begins in the Aquitaine basin in the Lower Triassic in the immediate vicinity of Nordpyrenäenüberfahrung (Note: Permotriassische basins such as the Brive Basin and the Grésigne Basin still be expected to bedrock ). By starting here, the depression spread slowly to the north.

Triassic

Sedimentation begins in the Lower Triassic ( Buntsandstein ) with colored sandstones and mudstones, in the Middle Triassic ( Muschelkalk ) follow dolomitic limes, salt beds and colorful mudstones. In the Upper Triassic ( Keuper ), the salt deposition continues further, the conclusion then form ophitische lavas ( dolerites and tholeiites, just to the south ). The salt layers were later recognized as diapirs during the Pyrenean orogeny, the colorful clays were used as Abscherhorizonte where Triassic sediments and later up to the line Arcachon - were pressed Toulouse.

Characteristic of the Triassic sediments is their germano formulaic character. On the Aquitanian plateau they are of continental origin, it is only the Keuper available. In the south, however, they take on marine character and show their full training. The Triastransgression was from south or southeast from the Tethysbereich about the time not yet existing Pyrenees away. The sediments in favor of a restrictive marine depositional environment and shallow water, the dry fell occasionally; this explains the strong presence of evaporites. The sediments can be total to over 1000 meters thick. They range in the north approximately up to the line Garonnemündung - Brive.

Law

Sequenzstratigraphisch can the marine Jurassic cycle divided into seven second-order sequences, three in the Lias, two in the Dogger and Malm two:

Hettangische - sinemurische sequence.
Lotharingische - carixische -dome step sequence (Upper Sinemurian - Pliensbachian ).
Toarcische - aalenische sequence.
Bajocische - unterbathonische sequence.
Mittelbathonische - callovische sequence.
Oxfordische - sequanische sequence ( Oxfordian - Kimmeridgian lower ).
Cimmeridgian - portlandische sequence (Upper Kimmeridgian - Tithonian ).

The sequences are separated by unconformities. The Jurassic sequence is completely preserved only in the Quercy, in the south ( Subpyrenäenbecken ) it is partially made very patchy.

The basal hettangisch - sinemurische sequence has transgressive character and for the first time appear now in the Aquitaine basin full navy, but generally relatively poor fossil sediments. This Liassic transgression picks from the Sinemurian - characterized by calcareous - dolomitic, partly oolitic sedimentation - gradually throughout Aquitaine over, then despite minor regressions in Pliensbachian towards the end of the Lias and Dogger, the basement of the western Massif Central in part with more than 30 to overlap kilometers - the same is true also for the western Vendée. Until the line La Rochelle - Angoulême - Périgueux - Figeac an inner shelf builds up in the northern section. Here there are the general detrital Transgressionssedimente the basal Hettangiums usually range from a base conglomerate, from arkoses and out of plant material, relatively fairly dense sand and mudstone. Here are the rest of Hettangian -marine sediments of a restrictive lagunär - lacustrine facies (green mudstones, colorful marl, dolomitic limestones and limestones rich in Zwergfaunen and evaporitic layers ). The sediments of the Sinemuriums have fully marine character, they contain a pelagic fauna ( soft and hard lithographic limestones Bänderkalke ). At the end of Sinemuriums there is a sudden regression with the formation of hard reasons.

The second Liassequenz also has marine- transgressive character and begins in Lotharingium / Unterer Carixium - well dated by a rich ammonite fauna ( Arietites, Oxynoticeras, Deroceras and Uptonia jamesoni ). The sediments are calcareous, rich in quartz grains and reprocessed to cobbles Sinemuriums. The Upper Carixium consists of very fossiliferous ( Aegoceras capri cornu ) Mergelkalkbänken with intermediate gray marl layers. The following ammonites leading ( Amaltheus margaritatus ) and oysters leading ( Gryphaea cymbium ) marl, which reveal an open shelf to the Atlantic Ocean. In the Lower Domerium is for the first time on the Seuil du Poitou, a marine connection to the Paris basin and the Détroit de Rodez and the Détroit de Carcassonne on Jurassic sea south-eastern France. In the course of the Upper Domeriums it comes to a renewed regression with sandy limestones of the littoral, the ( spinatum Pleuroceras, Pecten aequivalvis ) are very rich in fossils and can occur in marginal zones as iron-rich oolites. At the end of the sequence form again hard reasons.

The third and final Liassequenz goes in the Lower Toarcian without detrital deposits immediately to black ammonites leading over ( Harpoceras falciferum and Hildoceras bifrons ) marls. Towards the end Toarcian / early Aalenian take the sediments with sandy limestones to regressive character. The limestones contain oyster beds, Eisenoolith and gypsum layers and usually end with an erosional. At fossils they lead Pleydellia aalensis and Leioceras opalinum.

In the southern sector of the Aquitaine basin, the salt deposition proceeds ( with layers of anhydrite) continue, which can be up to 500 meters thick in the Lias.

The Dogger reached along a north -south line running Angoulême - Tarbes its maximum thickness of 300 meters. Along this line Riffkomplexe build on, the two share the Aquitaine basin. The reefs (east of Angoulême, northwest of Perigueux, east of Pau) are associated with Kalkoolithen that indicate a high-energy range. On the east of the reefs located shallow shelf neritic limestones and dolomites come ( in the south) to deposit and even supratidale in Quercy lignitführende limes. In the Atlantic Ocean opened area located ammonites leading pelagic limestone clay divorced from that very rich in micro- fossil Fädchenbildnern ( bryozoans ) are.

The first Doggersequenz begins east of Riff-/Oolithbarre in dolomitic Bajocian transgressive, the environment is very restrictive in nature. In places Aalenium is reprocessed. The Bathonian is calcareous in the northeast, southeast dolomitic. Towards the end of the cycle in the Lower Bathonian regressive tendency occurs on ( Lignite, breccias, lacustrine fossils in the Quercy ). In the Pyrenees range, a long-lasting layer gap forms. By the Kimmeridgian no longer occur in the eastern section Ammonites - this of course complicates accurate dating.

The second Doggersequenz begins in the Middle Bathonian in places with lacustrine limestones and brekzienhaltigen cobbles. The following are then mainly in the quiet shallow water remote neritic limestones (in the south continue dolomites). The conclusion in the Callovian form litorale Marginal Facies.

The significant Faziesgrenze the Riffbarre remains initially persist through Malm. In the deeper West area ammonites leading marl and limes are sold, in the eastern area, however, calcareous dolomite. The retreat of the Jurassic sea makes itself felt in the late Tithonian, as for example appear in the Adour basin dolomites and breccias, in the Charente evaporites, in the Quercy extremely littoral sediments in the Parentis Basin lacustrine limestones and anhydrite in the Gers. The straits close again and a last reef still holds in the Périgord ( in La Tour- Blanche ). The sea finally pulls back to south behind the Garonne back.

The first Malmsequenz seems to follow the Callovian without interruption in the Lower Oxfordian. However Zellkalke and breccias indicate sediment rearrangement ( Malm in the Grands Causses, this is backed up). In the Middle and the Upper Oxfordian limestones are sedimented under open marine conditions in the intercalate some reefs. The Lower Kimmeridgian is close to the beach again, indicated by oysters, sea urchins, and ripple marks.

The second begins in the Upper Kimmeridgian Malmsequenz although only sporadically regressive, yet the sedimentary character changed. There arise brecciated facies, synsedimentary re workups and rhythmic alternations of limestones and clays with Lignithorizonten. At datable fossils ammonite Aulacostephanus and Aspidoceras orthocera occur. This very restless sedimentation with a juxtaposition of open marine facies and reducing Schlicksedimentation under restrictive conditions seem to correspond to a first-time sedimentary individualization of the Pyrenees area. This phase contributes according to the oyster Exogyra virgula the name Virgulien. The pelvic narrowing is even more evident in the Tithonian to proceed in an almost complete marine retreat ultimately before the beginning of the Cretaceous ( the exception is the southern area ). To form in the Tithonian -ferrous Kalkoolithe with marl layers, dolomite and randfazielle sediments, dated by Gravesia portlandicum.

Lower Cretaceous

Compared to the Jurassic chalk has less distinct sequences, also the Lower Cretaceous is limited to depositional areas in the Pyrenees near. Probably the marine connection was better in the Lower Cretaceous in the direction of the Mediterranean than the Atlantic.

After a long hiatus, sedimentation resumes in the Lower Cretaceous. The sedimentation is limited to two areas - the Parentis Basin and on the Adour Basin. Both sub-basins have an amazing subsidence. Thus, up to 2000 meters of sediment, for example, in the Parentis Basin in the Lower Cretaceous deposited in the Adour basin even up to 4000 meters. The remaining Aquitanian basin is subject to the same time period continue to severe erosion.

The first deposits in the two sub-basins are littoral sediments in Wealden facies, mainly sand and mudstones.

In the Barremian marine Flachwasserkalke then divorced from, which are replaced in the northern Parentis Basin of detrital deposits. In Lacq the limes go on even in Lagunarfazies ( anhydrite ).

In the Upper Aptian reef-building partly the Urgon facies established in the two sub-basins - Fossilkalke with algae, coral polyps and rudists. The Urgonfazies girded the Parentis Basin complete; it remains in place until the Albian.

From the Albian take place in the southern Aquitanian basin strong salt tectonic movements, which in turn exert a great influence on the sedimentation - it arise breccias, conglomerates and turbidites powerful. In the Parentis Basin forms as a result even a remarkable unconformity. In the northern Aquitanian basin, however, lie down at the same time, the sediments in long-wavelength folds trains herzynischer direction. All these events are related with the first tectonic movements in the western Pyrenees in context. The sedimentation in the late Albian under rising sea levels is clayey, the Kalkreliefs the Urgonfazies be completely covered by it.

Upper Cretaceous

The beginning already in the late Albian transgression spreads very rapidly in the Cenomanian to the north of. Sedimentation takes in a northerly direction ultimately about the same proportions as before in the Jura. To the east, however, the sea penetrates only until shortly before Brive, Cahors, Agen, Muret and Carcassonne. The Nordpyrenäenüberfahrung forms at this time the Faziesgrenze Schelfsedimentation between the north and einsinkenden troughs in the south which receive flysch deposits (partly brekziöser Wildflysch ) from the Pyrenees region. In Saint -Gaudens, the flysch deposits are even accompanied by igneous rocks - Trachyte to ultramafic lavas. In Flyschbereich sedimentation during Turoniums and Coniaciums is very restless. The rest of the Upper Cretaceous is also done in Flyschsedimentation - sand - and mudstones in interbedded with occasional Karbonatlagen. Towards the end of the Cretaceous then increasing signs of regression, which is usually completed before the Cretaceous / Tertiary transition. In Subpyrenäengraben in the Petits Pyrénées, the sea holds even down to the lowermost Paleocene ( Danian ).

Moreover, the Aquitaine basin mainly pelagic limestones are excreted during this period ( as there are for example, the type localities for the Coniacian, Santonian and the Campanian in the Charente).

On the northern edge occur due to proximity to the coast to more differentiated facies. So the Cenomanian in the north has three sedimentation cycles:

In the upper cycle, a slight regression with sandy Rudistenkalken and oyster marls in the northwest and very shallow marine, plaster leading marls and sands in the northeast.
In the average cycle which overlaps into the Quercy, generally deeper marine marl (except occasional Paleoreliefs in Périgord with Litoralfazies and lignites ).
In the lower cycle Flachwasserfazies with Rudistenriffen in the northwest and continental influence with lignites in the Northeast.

The Turonian has marin transgressive character and spreads out into the solder. It leaves two are generally divided:

In one of massive, brecciated Rudistenkalken with subsequent Kalksanden existing Angoumien. The Angoumien is partially right from distinctive terrain levels.
In an exemplary chalk, marly Ligérien at the base.

Towards the end of Turoniums there is an increase in the Massif Central, which is reflected as an extensive sand beds in the sediment.

Coniacian and Santonian are generally constructed in the northern Aquitanian basin limestones, however, assume east of Périgueux increasingly sandy character.

The Campanian follows with a pronounced unconformity. The Flyschtrog now expanded to the north. In the vicinity of Pau was eroded away the entire Lower Cretaceous and the entire law before the start of Flyschsedimentation, sometimes even attacked the erosion down to basement. North of Pau occurs in the Campanian Mergelfazies, the so-called Aturien. In the northern Aquitanian basin contrast, unify the sediments and are fully marine, deposited capel leading Kalkmikrite.

In the Maastrichtian regression begins. After initial deposition of bioklastischen Rudistenkalken and isolated reefs of rudists and corals individual, there is a significant reduction in sea level and finally to the emersion. The sea stretches gradually back to behind the line Arcachon -Toulouse. At the same time emerge at the northern edge isolated shallow wrinkles trains with herzynischer strike.

Cenozoic

During the Paleocene the coast approximately follows the line Arcachon -Toulouse. North of this line ( in the Nordaquitanischen zone) sedimentation is continental - red mudstones, sands and lacustrine limestones. There is a short sea foray that leaves Echinidenkalke. In the southern basin area formed up to the line Audignon - Carcassonne ( Zentralaquitanische zone) a shallow shelf. The further south location Südaquitanische zone is deep water area, but the east flattens rapidly. In the Golfe Aturien in the West pelagic limestones are sedimented containing Globigerina, Operculinen and Alveolinen. Near the Petits Pyrénées, the limestones are already flachwasserfaziell, they lead here Madreporien, echinoids and Operculinen. In the Ariège and in the Corbières in the east, the sediments eventually take on entirely continental and lacustrine character.

In the Lower Eocene ( Ypresium ), a renewed transgression, the sea comes to the Medoc and until south of Oléron, in the southeast it reaches the Montagne Noire. In the Golfe Aturien now Globorotalia - leading marls are deposited further east turitellenreiche marls and limestones. In neuüberschwemmten area sands and limestones rich in sediment Alveolinen and Nummulites. In continental North East store at the same time iron-rich sands ( in the Charente ) and molasses ( in the Libournais and Agenais ) from. The continental sediments come into middle Ypresium mainly from the Massif Central.

In the Middle Eocene ( lutetium and Bartonium ), the sea level rise continues. The Alveolinen and Nummulitenkalke spread further from north to Blaye and Saint-Palais and to the east into Agenais. The North Pyrenean ditch deepens, the same thrown in his eastern part of conglomerates that Poudingues de Palassou. This marks the beginning of the uplift of the Pyrenäenorogens and the dominance of detrital sediment input from the south. The coalescing alluvial fans removal stretch north from down to Castrais. North of the alluvial fan created lakes where lacustrine limestones come for deposition. The detrital sediments coming from the now greatly leveled the Massif Central ( clays, sands, gravel ) are limited now only to a narrow peripheral zone on the northeast edge. In the Périgord and Quercy spreads at this time of Sidérolithique from - iron-rich sediments that have emerged from lateritähnlichen deposits.

During the Upper Eocene ( Priabonium ) a marine retreat takes place. The North Pyrenean trench is now filled completely with the detritus of the Pyrenees chain. In the Medoc still keep Nummulitenkalke and marl, but east of Bordeaux already occur continental molasses in appearance, which pass south of the Gironde in gypsum- bearing formations.

A permanent marine environment remains in place during the Lower Oligocene ( Rupelium ) in the south with Nummulites, lamellibranchien and echinidenführenden marls and sands. The Anomiidenkalke the southern Medoc, however, are lagunär. After a short-lived marine push at the beginning of Chattiums ( with starfish leading limestones in the northern Medoc and in the Libournais; mammal with leading molasses in Agenais ) the sea pulls towards the end of the Oligocene back very far. This general withdrawal is accompanied by tectonic movements, which can be in the north and in the center anticlinal ridge formed. The originating from the Pyrenees alluvial fans now range up to Albi and thus attain its greatest extent. Push it umgürtenden lakes before them, whose lacustrine Kalksedimentation then spreads over the Quercy and accesses the Causses and even on parts of the Massif Central.

In the Lower Miocene ( Aquitanian ) transgrediert the sea again, starting from his retreat in the south-western, north and east. Marine, littoral and lacustrine facies alternate with each other. While a slight temporary withdrawal arises in Condom, an enormous lake of Lac de Saucats in which a gray lacustrine lime Calcaire gris de l' Agenais is issued. After that, the sea reached its peak. It is surrounded by continental sediments, whose thickness increases toward the southeast. The Pyrenees alluvial fans show for the first time receding trend due to increased subsidence in the immediate vicinity of the orogen, but they still date back to the Agenais.

In the Middle Miocene ( Langhium and Serravallium ), the alluvial fan pull back further. The lacustrine zone therefore expands south to the Armagnac from.

The Upper Miocene ( Tortonian and Messinian ) is characterized by a dramatic sea retreat to the west. The sea takes place first from the northeastern Bordeaux and from the Bazadais back to finally leave the greater part of the basin. Add discontinued from the sea areas in the Armagnac sediment fossil empty sands and clays. In the dried-up areas in the north and east already established the draining of the Massif Central, still existing river network.

In the Pliocene ( Zancleum ), the sea is limited only to a narrow strip near the Arcachon Basin south of Soustons. It leaves sandy marl, which are very rich in benthic microfauna. In the rest of the Aquitaine basin continental sands are deposited, the Fauves Sables. The alluvial fans from the Pyrenees now settle only in the immediate vicinity of the mountain foot ( alluvial fans of Ger, Orignac - Cieutat, Lannemezan ). The drainage network of the Garonne River and its tributaries is already taking its existing today in the form - the Garonne differs here the Miocene debris accumulations largely from and between Toulouse, Agen and Bordeaux it then follows a weak subsidenten grave course.

The progressive silting of the Aquitaine basin, starting from its north-eastern edge was accompanied by a significant subaerial erosion, several Verebnungsniveaus out prepared in the detrital alluvial fans, including:

An Eocene Verebnungsfläche.
A Aquitanian Verebnungsfläche which is usually strongly silicified - clearly visible in Agenais, in the Périgord and Quercy.
A Pliocene ( Zancleum ) Verebnungsfläche, characterized by detrital clays in the Bordeaux region and in the country.

On the Pliocene Verebnungsfläche the present drainage system installed.

The three last Pleistocene ice ages Mindel, crack and Würm were also detected in the Aquitaine basin, mainly due to the different river terraces in the drainage network. At other glacial phenomena can be mentioned here:

Cavity fillings. These are of great importance in the dating of archaeological finds.
Deposits Aeolian origin. These cover more than one third of the Aquitaine region, mostly in Medoc and in the country. They were deposited during the last two stages of the Würm glaciation. The dune belt along the littoral today dates from the Holocene.
Slopes and ridge verhüllendes colluvium.
Kryoklastischer talus.

The evolution of the estuary of the Gironde is approximately 20,000 years ago to the late Würm.

In conclusion, even the rich prehistoric finds and sites in the Aquitaine basin mentioned, especially in the Dordogne.

Structural design and tectonics

Structurally can the Aquitanian basin divided into two areas, which are separated by a major fault voneinder. It is here to Nordaquitanische flexure, the starting moves from Arcachon towards Carcassonne. It represents the extension of the continental slope nordaquitanischen and divides the Aquitanian basin structurally in a northern province and in a southern province.

The Northern Province or Aquitanisches plateau represents a typical continental shelf is with a greatly reduced sedimentation and several Auftauchphasen ( throughout the Lower Cretaceous, in phases in the Upper Cretaceous and Cenozoic in ). The basement is rarely deeper than 2000 meters. Triassic and Jurassic achieve together the cardinality of 1000-1700 meters. The Lower Cretaceous is missing, the Upper Cretaceous reaches only a few hundred meters. The Paleogene is in the north, if present, only very thin, but wins in thickness to the south and is then overlaid by thin Neogene.

In the eastern part can be parallel to the Pyrenees border recognize several west-northwest - east-southeast - trending large-scale structuring:

Einmuldung of Quercy.
High area of Tarn -et -Garonne.
Ditch Castres.
High area of Toulouse.

In general, the northern province is characterized by simple tectonic structures (regional trough configurations and high areas, long-wave trains folds, faults ), followed by the Hercynian, Armorican and Variscan strike directions. These structures were created in the course of several phases:

Jurassic phase. The created structures are usually synsedimentary origin and follow Variscan strike directions. During the later taking place Kreidesedimentation they affect Faziesräume and Transgressionsmodus sustainable.
Endcampanische - maastrichtische phase. This phase enhances the already Jurassic pre-drawn structures. There arise the following anticlinal ridge, running parallel to the north-eastern edge of the pool more or less, and can be traced to more than 200 Kilometers The Mareuil- Meyssac anticline. This structure is an asymmetric anticline at Mareuil, but between Terrasson and Meyssac a fault with a significant jump height.
The Périgueux anticline. This structure extends from about La Tour Blanche Cognac to Perigueux and Saint- Cyprien, designed as a typical anticline is in La Tour Blanche and Saint- Cyprien.
The Oléron Jonzac - Riberac - Sauveterre la Lemance anticline. This structure is a unique anticline at Jonzac and Sauveterre.

These anticlines are interrupted by the northwest-southeast running synclinal trough configurations of Sarlat and from Saintes.

Eocene - Oligocene phase. It is subject to other anticlines, usually somewhat lower floor and not visible on the surface: The northeast-southwest - trending dome Aufbeulungen of Listrac, Blaye and Couquèques.
The northwest-southeast - trending state bulging of Sainte -Hélène - Carcans.
The synclinal of Bordeaux.
The east-west - trending anticlinal ridge of La Teste- Villagrains - Landiras - Miramont in Guyenne.

The southern province is dominated by the deep sub-basins Parentis and Adour, as well as the intermediate threshold range of Mimizan. Compared with the Northern Province to take her as the sediment thickness ( 5000-11500 feet ) strongly. Triassic and Jurassic reach 2000 - 3000 meters, the Lower Cretaceous 500 - 1500 meters. The Upper Cretaceous varies 500-3000 meters, the Paleogene between 1000 and 3000 meters, and even the Neogene can boast almost 1000 meters.

The tectonic movements in the Southern Province were much more complex in nature and are also of a significant salt tectonics ( diapirs ) superimposed. Unfortunately, a large part of the structures formed from plio - quaternary detritus is covered. Thanks to the numerous exploratory drilling for oil and aquifer but they are known in broad outline. As in the Northern Province is also here mainly arranged in parallel Antiklinalrücken whose wavelength decreases steadily towards the south. Conversely, the intensity of the Halokinese increases towards the south. The Antiklinalrücken incurred during the uplift of the Pyrenees in the Eocene / Oligocene. Your structuring was completed in the Miocene.

The following Antiklinalzüge can be seen ( from north to south ):

Parentis- Bouglon - Agen
Mimizan- Roquefort- Creon - Cezans - Lavardens
Boos - Audignan - Nogaro
Saubrigues - Biarotte - Bastennes - Garlin
Peyrehorade -Sainte -Suzanne - Lacq - Pau - Meilhon

During the Plio - Quaternärs tectonic movements result in compensation at the northeast edge of the Aquitaine basin to uplift and rejuvenate the desk plaice of the Massif Central; Pelvic inside they usually follow sketches in the basement and there are thus tilted some Pliocene Verebnungsflächen. This in turn has a very large influence on the hydrographic network, then river relocation and responsibilities are a river in the basin of the Garonne and the Adour.

The tectonic movements in the Aquitaine basin are far from complete even today, as revealed by strong earthquake on the northern edge of the Pyrenees and medium-strong quake on Oléron.

Tectono - metamorphic zones of the basement

The hidden under the sediments of the Aquitaine basin Variscan basement can be the basis of geophysical soundings in several northwest- trending tectono - metamorphic zones are divided ( from north to south ):

Ligero arvernische zone. It is bounded by the line Niort - Angoulême - Fumel -Montauban, which runs parallel to the dextral shear zone Südarmorikanischen in the north. Polymetamorphic core zone of the Variscan orogen.
Südarmorikanische zone. Its southern boundary is the line La Rochelle -Saintes -Chalais. The zone ends at Bergerac. To the south, via deferred crystallizer ceiling Devonian / Carboniferous age.
Nordaquitanische zone. Their southern boundary is identical to the Südvariszischen thrust front or the Nordaquitanischen flexure. It follows the line Arcachon - Agen -Toulouse. In Pennsylvanian south over false ceilings of the external zone.
Aquitanian block, referred to as micro- continent Aquitania. This zone extends to the Nordpyrenäenüberfahrung and is equated with the Southern Province. Already at the Gondwana foreland block belonging.

Moho depths

The maximum depth of Mohorovicic discontinuity with 36 km approximately follows the course of the Garonne. You flattens towards the Massif Central, and has here only around 30 kilometers. The same is true for the approach to the Pyrenees, on the northern edge of the Pyrenees, the Moho is also only 30 kilometers deep. In the oceanic part of the Parentis basin the Moho is found already at 20 Kilometres depth. This indicates an extreme thinning of the continental crust, or their starting Ozeanisation. By comparison, under the Central Pyrenees, the crust is 50 km thick!

Geodynamic relationships

For a better understanding of the geological processes in the Aquitaine basin, it is important to direct our attention to larger geodynamic contexts. The decisive factor should be two significant developments:

The break-up of Pangea and the opening of the North Atlantic and, consequently, the Bay of Biscay.
The movements of Iberia.

During the Upper Triassic period about 230 million years ago ( Carnian ) of the supercontinent Pangea began to break up slowly. In the Atlantic region continued this gradual rifting process in a region of the Central Atlantic. During the Lower Jurassic, the initial nor continental grave breaches were changed over into their marine stage, the Central Atlantic began to spread out ( in the Toarcian, 180 million years ago ) and North America, South America and Africa separated from each other. Already in the Callovian of the Central Atlantic was full marine. However, the spreading process went on and gradually extended also to the North Atlantic area. Thus came during the Tithonian 150 million years ago in the wake of occurring later opening of the North Atlantic a one Riftarm along the present-day north-western French continental margin and began Iberia, which was still up there with the Armorican Massif in connection to push away in southern direction. The Atlantic Ocean was thus able to penetrate for the first time directly into the Aquitanian basin. In the north of the retreating Iberia consequently the Bay of Biscay opened. Iberia led except its southern drift motion throughout the Lower Cretaceous an additional rotational movement counterclockwise through that made to approach the north-eastern part of Iberia to the southern France (first tectonic movements in the Pyrenees in the Albian; Pyrenees metamorphosis million years ago, 108-93; Cenomantransgression ) and ultimately the collision in the Eocene / Oligocene ( uplift of the Pyrenees with simultaneous removal ) resulted. The main phase of the Pyrenees uplift went with the Aquitanian to end, followed by essentially isostatic movements, which persist to the present day.

Mega sequences

The geodynamic evolution of the Aquitaine basin can be somewhat simplified in four mega sequences summarize, the starting point is the beginning of rifting in the Bay of Biscay in the late Jurassic ( Tithonian ):

Prärift mega sequence. Triassic to Upper Jurassic. Mainly clastic sediments and carbonates, followed by powerful evaporites in the Triassic; Schelfkarbonate in the Jura.
Synrift mega sequence. Lower Cretaceous ( Tithonian to Albian ). Formation of Biscay with partial Ozeanisation. Non - and shallow marine clastic sediments and limestones in the Neocomian, followed by powerful Schelfkarbonaten in the Aptian and Albian. The mega sequence ends in the Cenomanian by the onset Inversionstektonik to former strain fractures.
Postrift mega sequence. Upper Cretaceous ( Cenomanian to Paleocene ). The sinistral movement of Iberia relative to France leads to the formation of several sub- basins, which are caused by shearing motions with simultaneous stretching (pull -apart structures). Turbidites in the south.
Foreland basin mega sequence. Cenozoic ( Eocene to current). The collision of Iberia with France in the Eocene extensional tectonics finished. Ins foreland basin is entered by Pyrenenäenorogen in the Eocene flysch and Miocene molasse.

Minerals and natural resources

Hydrocarbons

Economically, the most significant among the natural resources in the Aquitaine basin are undoubtedly the hydrocarbons ( oil and gas). The deposits are located in the Lower Cretaceous basins of Southern Province:

In the Parentis Basin. Petroleum. Locations are Parentis, Cazaux, Lavergne. The Parentis Basin contains the bulk of the oil reserves of the European France.
In the Adour Basin. Natural gas. Locations are Lacq, Meillon, Saint- Marcet. With 220 billion cubic meters of the Adour Basin contains virtually all of the natural gas reserves of France.

Mother or reservoir rocks are limestones and dolomites from the Jurassic ( Kimmeridgian ) and from the Lower Cretaceous. Claystones from the Lower Aptian act as a seal.

Groundwater

Classic groundwater reservoirs are located in the Upper Cretaceous and the Tertiary of Bordeaux. Recently, the huge deposits is to be entered into the Eocene sands at Lussagnet, for the space Pau -Toulouse a hugely important discovery.

Other Resources

Furthermore, to lead:

Clays and shales. Raw material for countless brickworks (tile, brick, terracotta, etc.). Deposits are predominantly found in the Toarcian, in the Eocene ( lutetium ), in the Oligocene and Miocene ( Aquitanian, Burdigalian, Tortonian and Langhium ).
Kaolin. Raw material for porcelain manufactories. Lens -like Eocene Residuallagerstätten, often in the Upper Cretaceous karst (eg in Les Eyzies ).
Peat. Pleistocene and Holocene horizons in the Médoc (Gironde estuary ).
Lignite. In the Cenomanian of Sarladais, obermiozäne / Pliocene deposits in the country, in open cast mines at Arjuzanx.
Bauxite. In Jurassic karst pockets between pitch and Lavelanet. Unprofitable.
Iron. In the Eocene Sidérolithique. Deposits in the Périgord and Quercy. No longer economically viable.
Non-ferrous metals. Mainly lead-zinc mineralization in the basal Sinemurian. In the Charente and in Figeac, but not economically more profitable.
Wood. Vast forest areas in the country and in the Dordogne provide the raw material for a diversified wood processing industry (production of firewood for heating plants and for private consumption, charcoal, activated carbon, pallets, lumber, furniture industry )
Fruit growing. For example, the plums Agenais ( Pruneau d' Agen ).
Wine. Famous vineyards in Cognac, Bordeaux, in Armagnac, in the Chalosse and Béarn.

Final considerations

The structuring of the Aquitaine basin is characterized by two main factors:

The Variscan basement.
The Pyrenäenorogen.

The northwest-southeast - trending tectono - metamorphic zonation of the basement has been reflected sustained on the sedimentary evolution and structuring in the Aquitaine Basin. Hercynian same direction also follows the northwestern French continental margin, which had emerged in the wake of the opening of the Bay of Biscay. He finds his continent Continued upward in deep Subpyrenäenbecken. The Antiklinalrücken into the pelvic sediments are arranged substantially along this direction. Similar to the Südarmorikanischen shear zone, which also strikes the northwest-southeast direction and has a pronounced dextral shear component Antiklinalrücken also show this dextral shear. Their origin is therefore not only compressive nature. Also the Parentis Basin is bounded by the Armorican, dextral shear zones simultaneously subject to a distension and finally produced an east-west - oriented pull -apart basin. In the course of Biscay spreading represents the Parentis Basin is the attempt of the Atlantic penetrate further into the continental Aquitanian basin. However, this was prevented by the final anti -clockwise rotational movement of Iberia. From the Cenomanian the Aquitanian basin is then subject to the influence of the resulting Pyrenäenorogens with its west-northwest - east-southeast - trending structures. The Pyrenees are not purely compressive origin but have, in their case at the same time a major sinistral shear movement. The Pyrenees structuring then influenced the Aquitanian basin up to the present day and was pervasive nature - for example, tectonic effects of Pyrenäenorogens can still be observed on the northeast edge of the Aquitaine basin in the immediate vicinity of the Massif Central.

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