Chirp 512i sub-bottom geophysical data collected in Breton Sound offshore of the Lower Mississippi River Delta, Louisiana, during R/V Point Sur cruise PS2518 from 2025-05-07 to 2025-05-10

During R/V Point Sur cruise PS2518, from 2025-05-07 to 2025-05-10, 97 line-kilometers of Chirp sub-bottom geophysical data were collected in Breton Sound offshore of the Lower Mississippi River Delta as part of the Mississippi River Delta Transition Initiative (MissDelta) project. This dataset archives raw, high-resolution Chirp sub-bottom files in standard Society of Exploration Geophysicists (SEG) SEG-Y revision 1 format, which produce high-resolution, shallow-penetration images of stratigraphy beneath the seafloor. Data were collected using an Edgetech 3400 512i towfish instrument that was towed at a depth of 1-3 meters below the water's surface. The Chirp system emitted a high frequency pulse of 1-16 kHz with a 15-millisecond pulse at a ping rate of 5 Hz. Acoustic energy transmitted from the instrument was reflected off density boundaries in seafloor or sub-seafloor sediment layers, received by the transducer, and recorded by a topside computer. This process generated a two-dimensional profile of the structure of sediment layers beneath the towfish and the seafloor. Positioning data for the Chirp sub-bottom data was collected by a Hemisphere Global Positioning System antenna.