Editing Rochechouart impact structure (section)

== Major characteristics ==
The Rochechouart impact structure is composed of central sub circular zone approximately {{cvt|12|km}} in diameter exposing breccias and impact melt rocks (represented in grey on the map), and an annular diffuse zone approximately {{cvt|25|km}} in diameter where breccia dykes, intense fracturing, para-authochonous breccias are locally encountered in the crystalline rocks forming the basement of the crater.<ref name=":7" /> The central deposits fill and landmark the initial crater bottom. From a stratigraphical point of view, the impact deposits form a quasi-horizontal (slight tilt of less than {{val|1|u=deg}}) continuous blanket. Yet the deposit is entailed by river valleys providing unique series of cross sections exposing the crater fill, crater floor and underlying bedrock.

Owing to the texture and the composition of the impact breccias, there is no significant contribution from sediments implying there was no sedimentary cover on top of the crystalline basement at the time of impact or it was shallow. The same applies for the sediments deposited in the nearby sea.<ref name=":7" /><ref name=":11">{{Cite journal|last=Sapers H.M., Osinski G.R., Banerjee N.R., Ferrière L., Lambert P., and Izawa R.M.|date=2014|title=Izawa R.M., 2014, Revisiting the Rochechouart impact structure, France|journal=Meteoritics & Planetary Science|volume=49-12|issue=12|pages=2152–2168|bibcode=2014M&PS...49.2152S|doi=10.1111/maps.12381|doi-access=free}}</ref>

Yet the Rochechouart impactites all display a prominent hydrothermal overprint that can be related to the proximity of the sea at the time of impact.<ref name=":7" /><ref name=":3" /><ref>{{Cite journal|last=Simpson S.L., Boyce A.J., Lambert P., Lindgren P and Lee M.R.|date=2017|title=Evidence for an impact-induced biosphere from the δ34S signature of sulphides in the Rochechouart impact structure, France|journal=Earth and Planetary Science Letters|volume=460|pages=192–200|bibcode=2017E&PSL.460..192S|doi=10.1016/j.epsl.2016.12.023|doi-access=free}}</ref>

Despite the erosion, the sequence of impactite lithologies is exceptionally complete at Rochechouart. All typologies of impactites and the whole sequence of shock metamorphic features are represented both in the deposits and in target. This includes dislocation breccia, breccia dikes, melt veins, pseudotachylites, cataclasites, shatter cones, megablocks, in the target rocks beneath and around the breccia deposits,<ref name=":3" /><ref name=":7" /><ref>{{Cite journal|last=Reimold W.U., Oskierski W., and Huth J.|date=1987|title=The pseudotachylite from Champagnac in the Rochechouart meteorite crater, France|journal=Journal of Geophysical Research|volume= 92|pages= E737–E748|bibcode=1987JGR....92E.737R|doi=10.1029/JB092iB04p0E737}}</ref> and all types of melt free, melt poor and melt rich impactites in the deposits.<ref name=":7" /> Even the very fine materials (impactoclastites) depositing last and transported worldwide by the winds, is preserved forming a very fine layered horizontal deposits on top of the melt rich suevite (breccia with a debris matrix and both rock debris and melt fragments as clasts) near Chassenon (see map).<ref name=":7" /> This material is emplaced in a quiet environment, after all the chaos produced by the excavation, by the collapse of the cavity, and by the possible back flooding related to the tsunami induced by the impact in the nearby sea. Such a landmark of the final stage of impact deposit is exceptional at impact sites (quasi unique case among the 198 terrestrial meteoritic impacts officially registered on Earth as of 2020).