Models for Holocene Valley-Fill Sequences from High-Resolution Seismic Facies of Galveston Bay: ABSTRACT

Abstract

Reconstructions of the northern Gulf of Mexico shelf for the Holocene have relied on the dating of isolated bathymetric banks. These banks, which are interpreted as former shorelines, provide snapshots of the shelf during periods of relative sea level stillstand. A more complete sedimentary record of the Holocene transgression is likely preserved in the incised valley-fill sequences. The first step in deciphering the record of Holocene valley-fill sequences is development of high-resolution seismic facies models based on modern environments. The modern incised valley-estuarine system of Galveston Bay has been seismically surveyed. Important environments include bayhead delta (Trinity River delta), tidal inlet, flood tidal delta (Bolivar Roads), and estuarine sediments (central bay). Additionally, fluvial sediments partially infill the entrenched Trinity River valley. Seismic facies interpretation was corroborated by information obtained from sediment cores. The influence of the rate of relative sea level rise on incised valley-fill facies architecture is demonstrated in hypothetical sequence models which are applied to the interpretation of high-resolution surveys of Holocene shelf deposits.