[meteorite-list] Known Tektite Strewn Fields - North American Strewn Field
From: Paul H. <oxytropidoceras_at_meteoritecentral.com>
Date: Wed, 1 Sep 2010 22:07:01 -0500 Message-ID: <20100901230701.8LQ4L.1675438.imail_at_eastrmwml49> In the thread ?[meteorite-list] Known Tektite Strewn Fields?? http://six.pairlist.net/pipermail/meteorite-list/2010-August/068400.html , Sterling K. Webb asked: ?So, I have a question for the geologists on the List (I know you're there), where do I go in the Eastern U.S. to find Top-O-The-Eocene exposures (beside Georgia and Texas)?? First, figure 1 of Heinrich(2009) shows the approximate distribution of the North American strewn field and locations from where tektites and microtektites of the North American strewn field has been reported. Microtektites have been reported from St. Stephens Quarry in Alabama from two levels in the North Twistwood Creek Formation. This suggest that microtektites, possibly even tektites, can be found within the outcrops within exposures of the Moodys Branch Group from Georgia to Texas that expose sediments which are contemporaneous with the Chesapeake Bay Impact (King and Petruny 2008). The exact outcrop belt in which find exposures, can be found in local and regional geologic maps, county geologic reports, field trip guidebooks and other publications. In Louisiana, the entire Moodys Branch Group is still somewhat exposed at Montgomery Landing Bluff on the Red River. Reference Cited: Heinrich, Paul V., 2009, Reevaluation of Tektites Reported from Rapides Parish, Louisiana. Louisiana Geological Survey NewsInsights. vol. 19, no. 1, pp. 10-14. The PDF file of this article can be either requested from the author of downloaded from either: http://www.scribd.com/doc/18698759/Alleged-Tektites-From-Rapides-Parish-Louisiana or http://www.lgs.lsu.edu/deploy/uploads/Summer_09_LGS_Newsletter.pdf King, D. T., Jr., and L. W. Petruny, 2008, Impact stratigraphy of the U.S. Gulf coastal states: Gulf Coast Association of Geological Societies Transactions. vol. 58, pp. 503-516. Georgia Deposits In Georgia, the source bed of Georgiaites has been located. It is "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.? It contains shocked quartz from the Chesapeake Bay impact. This sand layer, which is the basal layer of the Twiggs Clay, is a transgressive sheet sand consists of sand that has been redeposited, reworked, and bioturbated, Published papers and abstracts are: Harris, R. C., M. F. Roden, P. A. Schroeder, S. M. Holland, M. S. Duncan, and E. F. Albin, 2004, Upper Eocene impact horizon in east-central Georgia. Geology. vol. 32, no. 8, pp. 717-720; DOI: 10.1130/G20562.1 http://geology.geoscienceworld.org/cgi/content/abstract/32/8/717 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. Geological Society of America Abstracts with Programs. vol. 34, no. 6, pp. 402. http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_41931.htm http://gsa.confex.com/gsa/2002AM/finalprogram/session_3270.htm Schroeder, P. ., and Harris, R. S., 2004, X-ray powder diffraction evidence for shocked quartz in an upper Eocene sand deposit, Warren County, Georgia, U.S.A. Southeastern Geology. vol. 42, pp. 145?150 Schreoder, 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. Geological Society of America Abstracts with Programs. vol. 34, no. 6, pp. 544. http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_38959.htm http://gsa.confex.com/gsa/2002AM/finalprogram/session_3270.htm In addition, multi-lithic conglomerates and breccias, which are one to two meters thick have been reported from Georgia. These enigmatic conglomerates, occur between the middle Eocene Hawthorne Group and middle Miocene Altahama Formation. Although their origin is unknown, it has been suggested that they might be deposits related to the Chesapeake Bay impact. If so, they might contain ejecta from this impact (Cocker 2007, King and Petruny 2008). Additional studies of these conglomerates are definitely needed. References Cited: Cocker, M., 2007, Possible impact-related conglomeratic sediments in the upper coastal plain of southwestern Georgia. Geological Society of America Abstracts with Programs. vol. 39, no. 6, p. 311. http://gsa.confex.com/gsa/2007AM/finalprogram/abstract_131779.htm King, D. T., Jr., and L. W. Petruny, 2008, Impact stratigraphy of the U.S. Gulf coastal states. Gulf Coast Association of Geological Societies Transactions. vol. 58, pp. 503-516. Yours, Paul H. Received on Wed 01 Sep 2010 11:07:01 PM PDT |
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