The Distribution of the Triplet Reflector in the Northwestern Gulf of Mexico as Observed on High-Resolution Subbottom Profiles

Abstract

A regionally persistent sequence of closely spaced, parallel reflectors known as the Triplet was studied using high-resolution profile data and sediment core data collected throughout the slope of the Gulf of Mexico. When reflectors are regionally persistent, they may be of value for two reasons: their distribution provides important clues about the nature of broad-scale environmental processes, and they can serve as reference horizons for both scientific and engineering applications. Sediments accumulating in the northwest Gulf of Mexico serve as an archive for glacial-interglacial changes in climatic and oceanographic conditions. Specifically, it is thought by other researchers that the Triplet marks a significant flux of terrigenous sediments into the Gulf of Mexico at the end of the last glaciation, which happened when glacial meltwater from the Laurentide Ice Sheet and associated Lake Agassiz flowed through the Mississippi River drainage. In this study, the occurrence and character of the Triplet was carefully documented using reflectors on high-resolution subbottom profiles collected during twenty-eight surveys of various locations across the continental slope. Analysis of this data was conducted using the IHS Kingdom seismic software platform, and sediment physical properties and radiocarbon ages from a previous study provided a means to ground truth the reflectors. Synthetic seismograms generated from sediment physical properties were quite similar to actual subbottom profiles, and synthetic seismograms corresponding to incrementally increasing sedimentation rates were compared to regional changes in actual reflector character. Results show the characteristics of the Triplet reflectors change with distance from the Mississippi River in ways that are consistent with it being the source sediment variations that produced the reflectors.