Editing Rochechouart impact structure (section)

== History ==
The impact origin of the structure was recognized by F. Kraut in 1969.<ref name=":2">{{Cite journal|last=Kraut F.|date=1969|title=Über ein neues Impaktit-Vorkommen im Gebiete von Rochechouart-Chassenon (Départements Haute Vienne und Charente, Frankreich)|journal=Geologica Bavarica|volume=61|pages=428–450}}</ref> The occurrence of an unusual set of rock types referred to as ''breccias'' on the crystalline rocks of the Massif Central was reported in the Rochechouart area at the start of geology, in the early 1800s.<ref name=":3">{{Cite book|title=. Les effets des ondes de choc naturelles et artificielles, et le cratère d'impact de Rochechouart (Limousin, France), Thèse d'État|last=Lambert P.|publisher=Université de Paris-Sud, Orsay, France|year=1977|pages=515 p}}</ref> However, their interpretation either as sedimentary, volcanic, tectonic, or a mix of these, was a major subject of debate until impact became progressively recognized as a geological process in the 1960s.<ref name=":1">{{Cite book|title=Astroblemes: Ancient Meteorite-Impact Structures on the Earth, in, The Moon Meteorites and Comets, Edited by Gerard P. Kuiper, and Barbarra Middlehurts.|last=Dietz|first=R.S.|publisher=University of Chicago Press|year=1963|pages=285}}</ref><ref>{{Cite journal|last=Chao E.C., Shoemaker E.M., Madsen B.M.|title=First Natural Occurrence of Coesite|journal=Science|volume=132-3421|issue=3421|pages=220–222|bibcode=1960Sci...132..220C|year=1960|doi=10.1126/science.132.3421.220|pmid=17748937|s2cid=45197811}}</ref>

The impact origin of Rochechouart was definitely confirmed in the mid-1970s with the recognition by P. Lambert of the projectile signal in the various rocks bearing up to 500 times the nickel content of the target rocks.<ref>{{Cite journal|last=Lambert P.|date=1975|title=Nickel enrichment of impact melt rocks from Rochechouart. Preliminary results and possibility of meteoritic contamination|journal=Meteoritics|volume=10|pages=433–436|bibcode=1975Metic..10..433L}}</ref><ref name=":4">{{Cite journal|last=Lambert P.|date=1976|title=The meteoritic contamination in the Rochechouart crater: Statistical geochemical investigations|journal=Symposium on Planetary Cratering Mechanics. Flagstaff, Arizona|volume=259|pages=69–71|bibcode=1976LPICo.259...69L}}</ref> Rochechouart was then the first impact structure to be confirmed by the presence of projectile contamination, in the absence of meteorite debris and in the absence of crater morphology. This is significant because after shock metamorphism has been recognized and used by early impact geologists as ''the'' criteria for identifying impact structures in the absence of projectile, the opponent to impact craters on Earth postulated an endogenic process so called ''cryptovolcanism'', capable of creating the extreme shock waves responsible for craters and shock metamorphism. Rochechouart was thus on the list of ''cryptovolcanic'' structures. The recognition of a projectile signal at Rochechouart and progressively at other impact structures and especially at the K-T boundary a few years later,<ref name=":5">{{Cite journal|last=Alvarez L.W., Alvarez W., Asaro F., Michel H.V.|date=1980|title=Extraterrestrial cause for the Cretaceous–Tertiary extinction|journal=Science|volume=208|issue=4448|pages=1095–1108|bibcode=1980Sci...208.1095A|doi=10.1126/science.208.4448.1095|pmid=17783054|citeseerx=10.1.1.126.8496|s2cid=16017767}}</ref> definitely terminated the era of cryptovolcanism and skepticism toward impact cratering.