Tramp, Kristy L.¹, John B. Anderson¹ 
(1) Rice University, Houston, TX 

ABSTRACT: Depositional Architecture for a Coastal River in a Sequence Stratigraphic Framework, Sabine Pass, Texas and Louisiana

The modern Sabine Lake area, located in the northern Gulf of Mexico, consists of surficial estuary, fluvial, coastal and near-shore systems. Considerable sedimentation rates and subsidence preserve a subsurface clastic succession that can be divided based on erosional surfaces and stratal stacking patterns. 
High resolution seismic data reveals fluvial channels within each systems tract. Incised valleys, which form during the lowstand systems tract, are preserved as steep erosional surfaces with both fluvial and bay fill. Diagnostic features of fluvial/bay fill include chaotic reflectors at the base changing upward to predominantly parallel reflectors with minor inclined reflectors interpreted as fluvial sand grading to laminated bay mud and tidal channels. In contrast, transgressive valleys contain predominantly chaotic and dipping reflectors interpreted as laterally migrating fluvial systems. Stacked cut and fill sequences representing aggradational fluvial facies represent highstand valleys where preserved on the flanks of incised valleys. These data provide the opportunity to compare several 4th order glacio-eustatic fluctuations including cycles during which sea level fell below the shelf break. 
Glacio-eustatic sea level fall and rise is an important control on coastal river morphology, sediment deposition and strata preservation. Recognizing different valley architectures and applying the appropriate sequence stratigraphic context is important for prediction of favorable reservoir facies. Ongoing research includes relating the depositional architecture to a chronostratigraphic framework in order to facilitate direct correlation with the eustatic sea level curve and investigation of climate change and drainage basin reconfiguration as mechanisms for variations of valley architecture.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.