[meteorite-list] Louisiana - The Mysterious Zenoria Structure

From: Keith <littlejo_at_meteoritecentral.com>
Date: Thu Apr 22 10:08:33 2004
Message-ID: <Pine.SOL.4.33.0209291427110.27691-100000_at_katie.vnet.net>

As of September 30, 2002, there have not been any
credible reports of either impact structures or
craters from Louisiana published in the scientific
literature.

The only structure within Louisiana, to ever have been
unofficially proposed to be an impact structure is
Little Creek / Zenoria structure. It was first mapped
by Fisk (1938), who quite remarkably, made no comments
as to its origin. Since, then a number of people have
investigated the structure but nobody was able to come
tp any solid conclusions about its origin. An excellent
cummary about what is known about the Little Creek /
Zenoria structure is Echols and McCulloh (2000). This
paper can be found complete with text and figures in
"Search and Discovery - Little Creek Structure, T9N-R2E,
La Salle Parish, Louisiana, by John B. Echols and
Richard P. McCulloh, #50001 (2000)." at:

http://www.searchanddiscovery.com/documents/echols/index.htm
http://www.searchanddiscovery.com/sandd2a.htm

The abstract stated:

  "Little Creek is perhaps the most enigmatic structure
  in Louisiana. It shows a conjunction of two seemingly
  contradictory aspects: an areally extensive subsurface
  domal structure, on the crest of which is an
  unconformity with mappable angularity in the Upper
  Cretaceous chalk interval; and an overlying, compact
  collapse structure in Cenozoic strata, which crops out
  at the surface. The authors are aware of three
  unpublished hypotheses for the origin of this structure:
  (1) piracy of a preexisting piercement-type salt
  structure, (2) astrobleme, and (3) deep-seated
  subsurface igneous diapirism. A hybrid hypothesis
  combining any of these and possibly other influences
  may be viable. Oil and gas fields on the flanks of
  the larger, subsurface domal structure have produced
  since at least the 1920's."

Location Map
http://www.searchanddiscovery.com/documents/echols/images/fig01.htm

Geologic Map from Fisk (1938)
http://www.searchanddiscovery.com/documents/echols/images/fig02.htm

Regardless of the mystery surrounding this structure, at
this time, there is no evidence that the Little Creek /
Zenoria structure is an impact structure. The complex
history of tectonic movement strongly argues against such
and origin. In my opinion, as mysterious as this structure
is, it is very likely not an impact structure.

References cited:

Fisk, H. N. (1938) Geology of Grant and LaSalle parishes.
Geological Bulletin no. 10, Louisiana Geological Survey,
Baton Rouge, LA 246 pp.

John B. Echols and Richard P. McCulloh (1998) Little
Creek Structure, T9N-R2E, La Salle Parish, Louisiana.
Basin Research Institute Bulletin. vol. 8, pp. 30-39
(November, 1998) Louisiana Geological Survey, Baton
Rouge, LA

Yours,

Keith Littleton
New Orleans, LA
Received on Sun 29 Sep 2002 02:38:52 PM PDT