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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 913

Last Page: 913

Title: Uranium Mineralization in Eocene Point-Bar Deposit, South Texas: ABSTRACT

Author(s): Stephen P. J. Cossey, Hal Frank

Article Type: Meeting abstract


An Eocene point-bar deposit was exposed by open-pit mining near Conoco's uranium mill in Karnes County, Texas. Two oxidation cells within the 1-mi-wide point bar are closely associated with the sedimentary facies. One oxidation cell with a subtle color difference was wedge shaped, confined by the steeply dipping accretion sets of the point bar. Color differences between oxidized and unoxidized sediments are very subtle. The front of oxidation was in basal point-bar sediments immediately below a sandy channel fill sequence. This sequence contains the second or upper oxidation cell, which is tube shaped and is only 50 ft (15 m) wide and about 20 ft (6 m) thick. Abundant clay galls within the sandy channel fill prevented the encroachment of oxidation along lateral boundaries of this oxidation cell and, therefore, controlled the distribution of local crenulations in the front. Trough cross-bedding and ripples indicate a south to southwesterly paleocurrent direction within the point bar. The orientation of the upper oxidation cell suggests that oxidizing fluids flowed in an easterly direction. Therefore, mineralization developed substantially later than sediment deposition, after uplift and a change in ground-water flow direction.

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Copyright 1997 American Association of Petroleum Geologists