[meteorite-list] Shocked Quartz Found in Georgia

From: Keith <littlejo_at_meteoritecentral.com>
Date: Thu Apr 22 10:08:30 2004
Message-ID: <Pine.SOL.4.33.0209241040220.27007-100000_at_katie.vnet.net>

In the upcoming Geological Society of America
Annual Meeting in Denver there will be a session
on impact stratigraphy. The abstracts for session
T89, Impact Stratigraphy, at the 2002 Denver
Annual Meeting (October 27-30, 2002) can
be found on-line at:

http://gsa.confex.com/gsa/2002AM/finalprogram/session_3270.htm

These abstracts include two papers about shocked quartz
and their relation to georgiaites.

Harris, R. S., M. S. Duncan, S. M. Holland, M. Steven,
M. F. Roden, Michael, and P. A, Schroeder (2002)
Probable shocked quartz as evidence of for an Upper
Eocene Impact Horizon in Coastal Plain, Warren County
Georgia. Denver Annual Meeting (October 27-30, 2002) at:
http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_41931.htm

In this abstract, the authors stated that they have found
a discrete impact horizon in the upper Eocene section of
southern Georgia. In east-central Georgia, they have
recovered shocked quartz from a " a patchy coarse-grained
sand layer up to 10 cm thick that lies at the boundary
between the Twiggs Clay and the underlying Middle Eocene
Huber Formation. The abstract stated:

  "Approximately 3-5% of fine to medium-grained quartz
  examined from the unit contain planar elements similar
  to planar deformation features (PDF's) indicative of
  impact shock. Most of the quartz grains display one set
  of planar features, but some exhibit 2 or 3 intersecting
  sets."

If they have found shocked quartz, they concluded "the
sandy lag at the base of the Twiggs Clay may record the
Chesapeake Bay impact in the stratigraphy of Georgia and
may be related to the parent stratum for georgiaites."

additional comments about the identification of the
shocked quartz is discussed in:

Harris, R. S., M. S. Duncan, S. M. Holland,
M. Steven, M. F. Roden, Michael, and P. A, Schroeder,

SCHROEDER, P. A., R. S. Harris, M. F. Roden, M. Duncan,
S. Mack, and S. M. Holland. (2002) 100% X-Ray Diffraction
Evidence for Shocked Quartz in an Upper Eocene Sand
Deposit, Warren County, Georgia, U.S.A. 2002 Denver
Annual Meeting (October 27-30, 2002) at:
http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_38959.htm

Other URLs

Michael Roden
http://www.gly.uga.edu/mroden/roden.html

Yours,

Keith
New Orleans, LA
(Future site of the world's largest artificial reef)

I will be visiting friends in Baton Rouge, Bunky,
and Alex, LA for the rest of the week and weekend.
And may move to Houston, TX after that.
Received on Tue 24 Sep 2002 10:43:32 AM PDT