Post‐impact structural crater modification due to sediment loading: An overlooked process

• Published in: Meteoritics & Planetary Science
• Main Authors: Tsikalas, Filippos, Faleide, Jan Inge
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2007
• Subjects: Space and Planetary Science; Geophysics; montagnais
• Online Access: http://dx.doi.org/10.1111/j.1945-5100.2007.tb00557.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1945-5100.2007.tb00557.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1945-5100.2007.tb00557.x

Abstract— Post‐impact crater morphology and structure modifications due to sediment loading are analyzed in detail and exemplified in five well‐preserved impact craters: Mjølnir, Chesapeake Bay, Chicxulub, Montagnais, and Bosumtwi. The analysis demonstrates that the geometry and the structural and stratigraphic relations of post‐impact strata provide information about the amplitude, the spatial distribution, and the mode of post‐impact deformation. Reconstruction of the original morphology and structure for the Mjølnir, Chicxulub, and Bosumtwi craters demonstrates the long‐term subsidence and differential compaction that takes place between the crater and the outside platform region, and laterally within the crater structure. At Mjølnir, the central high developed as a prominent feature during post‐impact burial, the height of the peak ring was enhanced, and the cumulative throw on the rim faults was increased. The original Chicxulub crater exhibited considerably less prominent peak‐ring and inner‐ring/crater‐rim features than the present crater. The original relief of the peak ring was on the order of 420–570 m (currently 535–575 m); the relief on the inner ring/crater rim was 300–450 m (currently ˜700 m). The original Bosumtwi crater exhibited a central uplift/high whose structural relief increased during burial (current height 101–110 m, in contrast to the original height of 85–110 m), whereas the surrounding western part of the annular trough was subdued more that the eastern part, exhibiting original depths of 43–68 m (currently 46 m) and 49–55 m (currently 50 m), respectively. Furthermore, a quantitative model for the porosity change caused by the Chesapeake Bay impact was developed utilizing the modeled density distribution. The model shows that, compared with the surrounding platform, the porosity increased immediately after impact up to 8.5% in the collapsed and brecciated crater center (currently +6% due to post‐impact compaction). In contrast, porosity decreased by 2–3% (currently −3 to −4.5% due to ...