Open AccessMultiscale Geoelectrical Properties of the Rochechouart Impact Structure, France
Author(s) -
Quesnel Yoann,
Sailhac Pascal,
Lofi Johanna,
Lambert Philippe,
Rochette Pierre,
Uehara Minoru,
Camerlynck Christian
Publication year - 2021
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2021gc010036
Subject(s) - geology , breccia , basement , magnetotellurics , impact structure , stratigraphy , petrology , lithology , seismology , geomorphology , electrical resistivity and conductivity , impact crater , tectonics , civil engineering , physics , electrical engineering , astronomy , engineering
The 205 Ma Rochechouart impact structure (France) is characterized by various impactite formations overlying the Hercynian crystalline basement. New constraints from downhole logging and surface electrical resistivity measurements along >100 m long profiles reveal that the top melt‐bearing breccia layer is more conductive and porous than the underlying melt‐poor breccia layer. The stratigraphy within the impactite and the transition with the basement are irregular at small (∼1–10 m) and medium (>100 m) scales, with vertical amplitude up to 40–50 m. At larger scale (>1 km), audio‐magnetotelluric observations are able to map the lateral and vertical extent of fracturing/brecciation in the basement, reaching 200 m below the surface nearby Chassenon, in the northern part of the structure. Our results also unveil that the impactite deposits and the brecciated basement of the Rochechouart impact structure may have been shifted laterally and vertically during the modification stage of the impact event through displacements of megablocks, which may be associated with the collapse of a central uplift.