Sediment Characterization and Mapping Using High Frequency Acoustic and Core Data in the Chesapeake Bay

Abstract

Abstract : Several locations in the Chesapeake Bay were surveyed with an acoustic seafloor classification system to characterize and delineate areal distribution of surficial sediment properties. Predictions of acoustic impedance using this system provide a capability for initial assessment and prediction of sediment properties during the survey. Color-coded trackline maps created in real-time on a computer monitor represent estimated surficial sediment fades type and location. Analyses of the color-coded maps reveal a diversity of sediment types and distribution at each site and between sites. Thick sediment coverings are predominantly fine grained as identified by low intensity acoustic returns. Thin coverings consist of more dense, granular materials and are identified by higher intensity acoustic returns. Two locations south of the mouth of the Patuxent River and one near the mouth of the Choptank River consist primarily of fine and medium silts to silty clays. These sizes exhibit the lowest impedance levels on the trackline maps. Samples collected at one site slightly inside, and three sites north, of the mouth of the Patuxent River are composed of more dense, granular sands. Higher predicted impedance on the maps are indicative of dense sediments. Acoustically derived impedance predictions have been gridded and contoured to create a color-coded sediment facies province map at one of the sites. This province map provides a representation of relative sediment type and distribution at this site.