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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Fluvial Depositional Systems of the
Carrizo-Upper Wilcox in South Texas
By
In the Rio Grande embayment of South Texas, the Carrizo-
Upper Wilcox interval (Eocene) consists of two sand-rich
coastal plain fluvial depositional systems that grade basinward into several deltaic complexes. The bedload
channel system is dominated by multi-story multi-lateral
fluvial channel-fill sandstones. This system is typically greater
than 90 percent sandstone. Shales are thin and laterally
discontinuous, the remnants of abandoned channel fills.
Bedload channel sandstones dominate the major fluvial axes
and form the depositional framework of the interval. The mixed
alluvial system consists of a more typical suite of coastal plain
facies. Mixed-load channel-fill sandstones tend to be isolated
and surrounded by overbank shales and thin sandstones.
Crevasse splay and lacustrine facies occur in the floodplain
area.
Total-interval isopach patterns, sandstone geometries,
and depositional systems distributions indicate that fluvial
sediment input was converging upon the embayment from the
west, northwest, and north.
Economically, the Carrizo-Upper Wilcox of South Texas
has a three-fold significance. The updip Carrizo Sandstone is a
major source of fresh groundwater, includes several large oil
fields, and also contains deposits of uranium minerals. The
downdip Upper Wilcox trend is an area of active hydrocarbon
exploration. End_of_Record - Last_Page 3---------------