Details

Autor(en) / Beteiligte

• Snyder, D. B.
• Hobbs, R. W.

Titel

Ringed structural zones with deep roots formed by the Chicxulub impact

Ist Teil von

• Journal of Geophysical Research, 1999-05, Vol.104 (B5), p.10743-10755

Ort / Verlag

Washington, DC: Blackwell Publishing Ltd

Erscheinungsjahr

1999

Link zum Volltext

Quelle

Wiley Online Library

Beschreibungen/Notizen

• The Chicxulub meteorite/comet impact of 65 Ma occurred on the present northeast coast of the Yucatan peninsula of Mexico and is considered by many to have caused a mass extinction at the end of the Cretaceous period. Impact craters are traditionally described in terms of ring structures. Deeply rooted faults underlying four previously recognized ring zones of the Chicxulub impact crater, as revealed on new deep seismic reflection profiles, demonstrate the catastrophic and diverse deformations that produced these zones. The innermost annular zone at Chicxulub coincides with a central peak ring. The seismic data show that the peak ring is composed of low‐velocity (<5 km s−1), chaotically reflective material, interpreted as impact breccia, lying on top of blocks of pre‐impact strata that were downdropped 4–6 km. Normal faults within the Cretaceous strata and deep, inward dipping reflections characterize two deformation zones at radial distances of 55–65 and 85–98 km. These normal faults accommodated the collapse, during the modification stage of crater development, of large (radial width of 5–25 km) blocks of pre‐impact strata uplifted during the excavation stage. The structures root in the lower crust at depths of 15–30 km. Blind thrusts indicated by monoclines in pre‐impact sedimentary rocks and deep, inward dipping reflections within the crystalline basement mark the outermost ring of deformation. These monoclines correlate with small topographic changes on the Cretaceous‐Tertiary boundary layer at radial distances of 120–135 km. Palinspastic restoration of coherent blocks of downdropped pre‐impact strata enabled improved estimates of the size and shape of the hole formed by the impact in a prominent reflector at 3‐ to 4‐km depth. This hole is slightly elliptical along a SE‐NW major axis (radius of 68 versus 63 km).