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Chicxulub impact crater geophysical characteristics



From: Ben Creisler
bcreisler@gmail.com


A new online paper:


S.P.S. Gulick, G.L. Christeson, P.J. Barton, R.A.F. Grieve, J.V.
Morgan & J. Urrutia-Fucugauchi (2013)
Geophysical characterization of the Chicxulub impact crater.
Reviews of Geophysics (advance online publication)
DOI: 10.1002/rog.20007
http://onlinelibrary.wiley.com/doi/10.1002/rog.20007/abstract


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 >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 <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.