ABSTRACT

Five distinct facies are recognized in the Eocene Queen City exposures between the Trinity River valley and the Louisiana state boundary. These facies (fluvial, deltaic, tidal flat, barrier, and tidal delta) display diagnostic suites of physical and biogenic structures. Sandstones within these facies exhibit substantial differences in paleocurrent pattern.

Fluvial influx was mainly from the northwest, with subordinate contributions of sediment from the east. A marginal alluvial and upper deltaic plain was transected by fluvial channels of fluctuating bedload to suspended load proportions and variable preservtion potential. Along the northwestern embayment margin, small, high-constructive shoal water deltas and crevasse subdeltas developed and prograded across the shallow Reklaw shelf. Barriers may have originated as destructive components of delta abandonment or as contemporaneous strike-fed features marginal to the main delta complex to the west. In either event, barriers are poorly preserved, possibly because of transgressive ravinement, but more likely because they were never developed on a major scale. Extensive backbarrier or bay-margin intertidal and subtidal flats and shoals reflect the interplay of tidal and wave-generated processes, leaving a characteristic record of variable physical energy and flow patterns. Flood-tidal deltas formed at the mouths of microtidal estuaries and, like some modern analogues, they were significantly larger than comparable mesotidal features. The inferred flood-tidal delta deposits also exhibit features reflecting storm processes.

Regional depositional patterns were largely controlled by: 1) location of the east Texas embayment with respect to the major deltaic depocenter, resulting in an eastward decrease in sediment supply; 2) configuration of the broadly funnel-shaped embayment and wide shelf, which may have augmented tidal range; and 3) transition from overall progradational character, with local transgressions, to a major marine transgression that culminated in shelf sedimentation of the overlying Weches Formation.