L.R. Hamberg, 1983. "Seismic Profiles and a Stratigraphic Trap—East Texas Field", Seismic Expression of Structural Styles: A Picture and Work Atlas. Volume 1–The Layered Earth, Volume 2–Tectonics Of Extensional Provinces, & Volume 3–Tectonics Of Compressional Provinces, A. W. Bally
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The use of seismic profiles to recognize and map potential stratigraphic traps is becoming an increasingly important exploration tool, especially within the more mature hydrocarbon provinces of the world. Seismic stratigraphy often requires not only high resolution seismic data, but also considerable geologic input to interpret features indicative of possible stratigraphic traps. Fortunately, one of the most readily recognized traps of this nature, the simple stratigraphic pinchout, does not require specially acquired seismic data. The composite line illustrated in this text shows such a feature. Although this "pinchout" may not seem overly impressive, it demonstrates the trapping mechanism for the giant East Texas field located on the east side of the East Texas Tyler) basin in northeast Texas. This field was discovered in 1930, by random drilling, long before seismic was considered an effective exploration tool. It is obvious, however, that the trap is easily recognized on reasonably good seismic data, and could readily be mapped with such data.
The trap is basically a stratigraphic pinchout of the Upper Cretaceous Woodbine formation. The Woodbine sand-shale sediments were truncated by erosion on the west flank of the elevated Sabine Uplift. These sediments are unconformably overlain by the Austin Chalk which serves as the main top seal for this trap. The bottom seal is the open marine shales and limestones of Lower Cretaceous age. The illustrations provided with this text show the geologic setting and parameters associated with this classic stratigraphic trap.
The relatively low velocity sand-shale section of the Woodbine overlying the high velocity, predominantly open-marine, carbonates of the Lower Cretaceous results in an excellent seismic interface mapable over most of the East Texas basin. Velocities associated with the Austin Chalk are usually sufficiently fast enough to also result in a well defined seismic interforce at the base of the Chalk. The velocity contrast between these three lithologic sequences is great enough to allow these