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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Relationships Between Depositional System;
Ground-Water Flow History; and Origin, Migration,
and Concentration of Uranium-Catahoula Formation of Texas Coastal Plain
By
The Catahoula Formation is a host for major known
reserves of uranium ore and is the target of extensive
exploration in the Texas coastal plain. Regional genetic
facies analysis shows the Catahoula to consist of two
principal fluvial systems. The Gueydan fluvial system of
South Texas consists of low sinuosity, bed-load to mixed-load
channel sands, and gravelly sands interbedded with
ash-rich crevasse and floodplain facies. Coarse material
was derived from erosion of volcanic debris in Trans-Pecos Texas; ash was derived from explosive eruptive
centers in western Mexico. The Chita-Corrigan fluvial
system of East Texas contains deposits of several sinuous
to meandering, mixed-load channel complexes surrounded
by extensive crevasse-splay, floodplain, and lacustrine
facies. Sands were derived from nonvolcanic
sources, but air-fall ash is abundant.
Analysis of trace uranium content of, ash-derived
mudstones indicates early mobilization of uranium in
depositional environments characterized by subaerial
leaching and soil formation. Solubilized uranium entered a
well-integrated, semiconfined ground-water flow system in
areas of ground-water recharge, and moved coastward down the regional hydrodynamic gradient. Primary controls
on the geometry of ground-water flow and total flux
through a particular area include (1) the aggregate permeability,
degree of interconnection, and orientation of
aquifer sands (determined by the depositional system); (2)
the distribution of syndepositional fault zones (which
affect both facies distribution and later ground-water flow
geometry); and (3) the geographic position of recharge
and discharge areas. The areal extent, geometry, and
uranium content of alteration fronts, in turn, reflect the
geometry and flux of the ground-water flow system at the
time of mineralization. Postmineralization diagenetic alteration
of host sands and the geological relationships suggest
that Catahoula mineralization patterns were established
soon after deposition in a semiconfined aquifer;
subsequent remobilization and migration of uranium have
been limited. End_of_Record - Last_Page 2---------------