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Origin and history

La phosphatière du Cloup d'Aural is a former phosphate mining mine discovered in 1865 by Jean-André Poumarède, pharmacist and chemist. Intrigued by bone debris and unusual stones in a field near Bach, he analyzed samples and detected an exceptional tricalcium phosphate content (70-80%). In 1867, he alerted the Prefect of Tarn-et-Garonne on the agricultural and paleontological importance of this discovery, marking the beginning of the systematic exploitation of phosphate deposits in Quercy.

Phosphatory exploitation was booming in the 1870s, with more than 160 active sites between Cahors, Figeac, Gaillac and Montauban. These mines, nicknamed phosphate holes, produce 30,000 tons of ore annually, valued at one million francs. However, as early as 1887, the deposits exhausted and the discovery of phosphates in North Africa (Tunisia in 1899, Morocco) made local exploitation uncompetitive. In 1902, only two phosphates remained active in Cajarc and Saint-Martin-Labouval.

The Cloup d'Aural site is distinguished by its paleontological richness: more than 600 fossil animal species, dating from the tertiary era (between -50 and -20 million years), have been identified. These fossils, including Xenomorphia parasitoid wasps discovered in 2018, served as a reference for European fauna. After decades of abandonment and looting, the site is protected by the creation of the national nature reserve of geological interest of the Lot in 2015. Ranked a historic monument in 1998, it is now valued by the association Les Phosphatières du Quercy and attracts 30,000 visitors annually.

The geological origin of phosphates results from karst phenomena. 170 million years ago, a tropical sea covered the Quercy, depositing carbonated sludge that later formed the limestones of the Causses. After withdrawal from the sea (-70 million years), erosion and acid rain will dissolve carbonates, creating cavities filled with phosphate clays between -50 and -20 million years. Fossils are accumulated, preserved in these natural pockets. Theories of their formation have evolved from a hydrothermal hypothesis to a karst explanation, confirmed by geologists such as Louis Dieulafait and Bernard Gèze.

Phosphatory exploitation has profoundly affected the local landscape and economy. In the 1880s, a "phosphate fever" in Quercy, attracting hundreds of workers. However, the rapid depletion of deposits and North African competition led to a sharp decline. Abandoned mines become landfills before being rehabilitated for their scientific value. Since 2000, the Cloup d'Aural site, designed for the public, a couple mining visit and paleontological discovery, offers a unique testimony to the geological and industrial history of the region.

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