Saturday, April 06, 2013

A More Detailed Examination of the Chicxulub Impact Crater

Geophysical characterization of the Chicxulub impact crater


1. S.P.S. Gulick (a)
2. G.L. Christeson (a)
3. P.J. Barton (b)
4. R.A.F. Grieve (c)
5. J.V. Morgan (d)
6. J. Urrutia-Fucugauchi (e)


a. University of Texas Institute for Geophysics, Jackson School of Geosciences, Austin, Texas, USA

b. Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Cambridge, UK

c. Department of Earth Sciences, University of Western Ontario, London, Ontario, Canada

d. Department of Earth Science and Engineering, Imperial College London, London, UK

e. Instituto de Geofísica, Universidad Nacional Autónoma de México, Ciudad Universitaria, Coyoacán, Mexico


Geophysical data indicate that the 65.5 million years ago Chicxulub impact structure is a multi-ring basin, with three sets of semicontinuous, arcuate ring faults and a topographic peak ring (PR). Slump blocks define a terrace zone, which steps down from the inner rim into the annular trough. Fault blocks underlie the PR, which exhibits variable relief, due to target asymmetries. The central structural uplift is great than 10 km, and the Moho is displaced by 1–2 km. The working hypothesis for the formation of Chicxulub is: a 50 km radius transient cavity, lined with melt and impact breccia, formed within 10 s of the impact, and within minutes, weakened rebounding crust rose kilometers above the surface, the transient crater rim underwent localized deformation and collapsed into large slump blocks, resulting in a inner rim at 70–85 km radius, and outer ring faults at 70–130 km radius. The overheightened structural uplift collapsed outward, buried the inner slump blocks, and formed the PR. Most of the impact melt was ultimately emplaced as a coherent less than 3 km thick melt sheet within the central basin that shallows within the inner regions of the PR. Smaller pockets of melt flowed into the annular trough. Subsequently, slope collapse, ejecta, ground surge, and tsunami waves infilled the annular trough and annular basin with sediments up to 3 km and 900 m thick, respectively. Testing this working hypothesis requires direct observation of the impactites, within and adjacent to the PR and central basin.

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