Henri Magnan
Henri Magnan (born September 2, 1831 in Valence , † July 3, 1872 in Toulouse ) was a French geologist.
Magnan went to school in Valence and Aubenas as well as to the Lyceum in Grenoble . He then attended the mining school in Saint-Etienne , but left it to help his father explore coal deposits. He examined deposits in Castanet, Saint-Génès (Hérault), Brassac (Cantal), Polonge, la Souche, Ouzy and Aveyron (Tarn) (in the latter place he examined lead-silver ores). Then he examined coal deposits in Spain ( Asturias , Sierra Morena ). From 1864 he was in Toulouse, where he studied geology with great zeal and success with Alexandre Félix Gustave Achille Leymérie . The focus was on exploring the Pyrenees .
In 1867 he discovered the Avicula contorta zone in the Corbières . The formation from the Rhaetian on the border of the Triassic to Jura is widespread in south-east France. He was also able to assign plaster formations in the Aude department , which were previously assigned to the Jura (Lias) and were formed hydrothermally, to the Triassic. He also examined the carbon and Permian stratigraphy in the Corbières.
Then he examined the chalk formations in the Pyrenees and was the first to be able to detect the stages Cenomanium (the first stage of the Upper Cretaceous), Aptium and Albium (Lower Cretaceous).
In 1869 he studied the geology and especially the Jura stratigraphy in the Tarn and Tarn-et-Garonne departments . The area is shaped by the foothills of the Massif Central (with extensive plutonites and metamorphic changes, Montagne Noires, Sidobre), but there are also Jurassic deposits (Causses du Quercy). He also thought he could resolve a stratigraphic inconsistency by dating a formation in the Grésigne into the Zechstein. This was not confirmed, but Perm deposits were later found in the wider area (east of the Grésigne).
He discovered the role of faults (he found the Marnaves faille, later called the Villefranche fault) and river erosion in landscaping and clarified the dating of old river terraces. These ideas were adopted by his friend Gustave-Marie Bleicher and transferred to other parts of the country (Vosges).
Much of his work was left unfinished because of his untimely death. In the short period from 1867 to 1872 he published 22 papers.
Fonts
- Etude des formations secondaires des bords sud-ouest du plateau central de la France entre les vallées de la Vère et du Lot, Bulletin de la Société d'histoire naturelle de Toulouse 1869
- Notice on the terrain quaternaire des bords de la Montagne Noire entre Castres et Carcassonne et sur l'ancien lit de l'Agout. Bulletin de la Société d'Histoire naturelle de Toulouse, Volume 4, 1870, p. 120.
Web links
Individual evidence
| personal data | |
|---|---|
| SURNAME | Magnan, Henri |
| BRIEF DESCRIPTION | French geologist |
| DATE OF BIRTH | September 2, 1831 |
| PLACE OF BIRTH | Valence |
| DATE OF DEATH | July 3, 1872 |
| Place of death | Toulouse |