Such folds in the French Alps spread to the west, and in the Pyrenees, on the other hand, to the north. In the latter the carriageways are apparently almost finished with the middle Paleogenic. In the Eastern Pyrenees the chain was broken up by subsidence, and the ancient folds were leveled over high areas. The remains of the Pyrenees attacked by erosion actually formed most of the soil of Aquitaine, which, throughout the Tertiary, was a sleeve, or a shallow gulf, or was occupied by a series of lakes. The arenas and molasses clays accumulated there, and limestone was rarely deposited in the calmer waters. In the Alps it seems that the acute phase of the corrugation took place in the Aquitanian; at that time, the carriageways were already in place; and the subsequent thrusts only made the bending of the pre-alpine limestone chains more accentuated, attacking the same molasses, which often remained in some syncline and was sometimes surmounted. The Jura is nothing more than a branch detached from the pre-alpine chains of the Dauphiné and separated from those of the Savoy by means of a geosynclinal, where the molasse has been preserved, still covering the folds of the less robust secondary layers. Its formation decreased the width of the furrow, by which the tertiary seas had advanced from the Mediterranean to the Rhenish moat of Alsace. During the Neogenic period, the Saone Basin was occupied by a lake or a series of lakes, which ended up emptying (Lake Bressan). The Rhone valley itself was formed in the place of a narrow gulf (improperly namedfjord by some geologists), which was filled by marine deposits from the Upper Neogenic period and by Alpine floods. But the great river penetrated deeply into it, several hundreds of meters below its primitive layout, and sometimes breaking down into the ancient base of the Massif Central, it got stuck in epigenic depressions, which determined the position of a whole series of cities.: Valence, Montélimar, etc.
Probably during the Upper Neogenic period and when the sea was still advancing within the Rhone furrow, the coasts of Provence acquired their current configuration, due to the sinking of the Hercynian massifs, of which the Maures and Estérel are the last remnants.
According to Mathgeneral, the Quaternary did not bring great changes to the physiognomy of the French soil. The progress of erosion, alternating with periods of accumulation along the great rivers, resulted in the formation of stepped terraces, which are especially clear in the basins of the Loire and the Seine. Fertile silts, sometimes true loess, covered the northern and eastern platforms of the Paris Basin and the plain of Alsace. In the Alps and in the Pyrenees, the cooling of the climate determined a grandiose extension of the glaciers, which at various times filled all the valleys and overflowed into the neighboring plains. In this way, in the Lower Dauphiné and in the southern part of the Bresse, a fringe of coarse deposits was formed, similar to those that cover the Swiss hills and the Bavarian plateau.
In the interior of the mountains, the type of relief was totally changed. The classic forms of glaciation (suspended valleys, dam rises, basins and circuses) gave their character to the central ranges and massifs of Savoy and Dauphiné, consisting of deep slopes of carriageway, mostly crystalline. The glacial forms are less evident in the large valleys (lower Isère, Durance, etc.), in the pre-Alpine ranges, where adaptations to the structure dominate the landscape, and also in the Alpes de Provence, where the glacial extent was relatively limited. In the Pyrenees, glacial modeling is often very considerable, especially in the central Pyrenees; but the accumulations of the piedmont lobes, expanding on the perimeter region, represent an important part only in the country of the Gaves and the Haute-Garonne (plateau of Lannemezan, moraines of Montréjeau). In the Jura there were small local glaciers; but all of its southern part was covered by alpine glaciers, which left moraine deposits, which completely changed the physiognomy of the limestone soil. The Massif Central also had its glaciers, which capped the high volcanic peaks of the Cantal and the Monts Dore, descending to the basins of Neussargues and Aurillac, where they deposited their moraines, widening the valleys and modeling small cirques on the peaks. The Vosges were covered with a real ice cap, which divided into long tongues in the Lorraine valleys, depositing scattered moraines on the sandstone plateaus south of Épinal, and blocking the Moselle on several occasions. widening the valleys and modeling small cirques on the peaks. The Vosges were covered with a real ice cap, which divided into long tongues in the Lorraine valleys, depositing scattered moraines on the sandstone plateaus south of Épinal, and blocking the Moselle on several occasions. widening the valleys and modeling small cirques on the peaks. The Vosges were covered with a real ice cap, which divided into long tongues in the Lorraine valleys, depositing scattered moraines on the sandstone plateaus south of Épinal, and blocking the Moselle on several occasions.