ANDERSON, JOHN, and ANTONIO RODRIGUEZ , Rice University, Houston, Texas
High resolution seismic data, oil company platform borings and sediment cores were used to map and characterize late Quaternary highstand, lowstand and transgressive fluvial channels of the ancestral Trinity, Brazos and Colorado rivers. The objective of this research was to evaluate these different fluvial systems as potential reservoirs and to assess their capacity for nourishing outer shelf-upper slope sand bodies.
Two main-end members are recognized. The first, which is represented by the Trinity/'Sabine fluvial complex, includes rivers that occupy the same channel throughout the eustatic cycle. They are characterized by complex valley fills consisting mainly of estuarine deposits and they deliver significant sand to the shelf break during lowstands. The second (Brazos) end-member is prone to avulsion, which results in minimal input of sand to the slope. Rather, sands are sequenstered in highstand and transgressive fluvial channels and associated deltas. Valley-fill successions are dominated by fluvial deposits.
Having a good sequence stratigraphic framework is essential for distinguishing these different fluvial end-members. Ongoing research focuses on seeing if there are differences in channel geomorphology and facies character that might further help distinguish these different fluvial systems.
AAPG Search and Discovery Article #90908©2000 GCAGS, Houston, Texas