Ain (river)

The Ain (æ̃, ɛ̃; En) is a river in eastern France. It gave its name to the Ain department. It is long. The river rises at an altitude of some 700 metres, near the village of La Favière, in the Jurassic limestone of the southern end of the Jura mountains and flows into the Rhône near Saint-Maurice-de-Gourdans, about 40 kilometres upstream of Lyon. Its source is in the old county of Franche-Comté. It flows south through the combined lengths of the two departments of: Jura (named after the mountains), and Ain (named after the river). On the way it passes through the towns of Champagnole and Pont-d'Ain. Its longest tributaries are the Suran, Bienne, Albarine and Valouse. The river flows through two regions. The Jura is, of course, Jurassic but it includes less clay than the Jurassic of England so Upper or Middle Jurassic means limestone of some sort, possibly marl (EB 13). The lower river passes over Holocene deposits from the river's own activity amongst rocks of the Middle or Upper Pleistocene (CG). The Jura consists of limestone strata crushed into ridges between the forces of the spreading rift valley of the Saône and the Alps, the latter raised by a collision of the Italian tectonic plate with Europe. The highest ridge is the easternmost and the Ain flows southwards in the lowest valley, which lies towards the western side of the Jura. The westernmost ridge is again rather higher as the plain of the Saône valley is subducted below the Jurassic rocks (Dercourt). The whole has been glaciated but there is relatively little till remaining in the Jura. The lower Ain flows on the plain where there is much Pleistocene material, much of it glacial till. However, the low scarp between the Pays de Dombes and the river is Miocene (CG). The economy is not generally such as to provide riches. Neither is it one which used to require large towns as other than external markets in which to sell. The population is therefore dispersed. The exception to this is the town of Oyonnax, in the Ange valley which is parallel with the Ain.