East Texas (Sabine/Trinity/San Jacinto)
Lowstand Systems Tract
Thomas and Anderson (1996) found that an average of eight meters of fluvial sand exists at the base of the Trinity/Sabine/Brazos incised fluvial valley. No radiocarbon ages have been acquired from the fluvial deposits, so it is not known how much of this fill was deposited during the lowstand and how much was deposited during the transgression. The valley is poorly imaged on the outer shelf, although platform borings from the area show approximately 30 meters of sand within the valley near the shelf break. Sediments were initially deposited in minibasins on the outer shelf, but as these minibasins filled bypass to upper slope minibasins occurred (Seismic Line OS91-11).
Thomas and Anderson showed that the Trinity/Sabine/Brazos valley experienced multiple stages of filling and incision. During each phase of incision, fluvial sands were eroded and transported down the valley axis. Hence, the valley acted as a point source for sand to the slope fan system that is confined to minibasins on the upper slope.
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