[meteorite-list] Kilmichael Structure, Mississippi, Revisited

[Paul]

Tomorrow afternoon, David T. King of the Department of Geology, 
Auburn University, Auburn, AL will talk recent research conducted
on the Kilmichael Structure, Mississippi, at this weeks Gulf Coast
Assicaition of Geological Societies 2006 Annual Meeting in 
Lafayette, louisiana. The paper accompanying this talk is;

King, D. T., Jr., and L. W. Petruny, 2006, Cosmic impact in the coastal 
plain of Mississippi? The Kilmichael structure. Gulf Coast Association 
of Geological Societies Transactions, vol. 56, pp. 341-351.

Its abstract states:

"The Kilmichael structure, a probable impact crater in Montgomery 
County, Mississippi, is a circular, structurally disturbed feature 
possessing a diameter of approximately 5.6 mi. A refraction seismic 
survey reveals subsurface characteristics of an impact structure, 
including a central uplift, annular graben, and concentric inward-
dipping faults. A gravity profile like that of some confirmed impact 
craters is present. In a key core hole at the structure’s center, 
770 ft of section, consisting mainly of breccias and large intact 
blocks, was penetrated and sampled. In this paper, we have 
reinterpreted the sequence of drilled strata as follows (in reverse 
stratigraphic order): (1) soil and colluvium; (2) post-impact 
laminated marine sediments; (3) conglomeratic aqueouswashback 
or resurge deposits of mixed provenance; (4) interbedded impact 
breccias and target rock blocks, i.e., surgeback deposits; (5) large, 
deformed and rotated blocks of the Upper Cretaceous Ripley 
Formation; and (6) interbedded impact breccias and target rock 
blocks, mainly Upper Cretaceous chalks. The stratigraphic age 
of this structure is probably late early to early late Paleocene, 
based on the fossil age of material from the youngest 
recognizable intact block drilled in the key core hole. The 
Kilmichael area was in a marginal marine to shallow marine setting
at the time of deformation and the drilled stratigraphy is consistent 
with aqueous or “wet-target” impact."

Yours,

Paul


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