Abstract: Stratigraphic Analyses of the Brazos Delta and Implications for Recognition

Michael Hamilton, John B. Anderson

According to numerous outcrop studies, the stratigraphic sequence for wave-dominated deltas possesses much of the same sedimentological signature as adjacent shoreface environments. Analysis of the modern Brazos delta reveals, however, a more complex facies architecture. Several vibracore transects from the delta and its shoreface indicate significant differences in depositional patterns. The most distinguishable differences are total sediment thickness, extent of bioturbation, abundance of sedimentological structures and gross lithologies. In all, the distinction between shoreface and wave-dominated delta facies is attributable to episodic and significant fluvial input into the delta.

Preservation potential of these deposits is also addressed with reference to preserved shelf sand bodies of the ancestral Brazos delta Although preservation potential during an overall transgression is low, deposition of wave-dominated deltaic sediments below wave base and during different eustatic regimes is known to have occurred.

Finally, the historical development of the Brazos delta suggests that deltaic classification schemes denote ideal conditions, and distinction between fluvial domination and wave domination is less apparent. We present here a depositional model implicating alternating periods of fluvial-dominated and wave-dominated sediment distribution within a single depositional lobe.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994