Sediment echosounder data was recorded during RV SONNE cruise SO174 between 01.10.2003 and 12.11.2003 in the Gulf of Mexico. The cruise SO174 aimed to investigate the types and structures of near-surface marine methane hydrates and the environmental conditions required for their formation. Furthermore, the cruise aimed at the assessment of microbiological turnover and deployments of long-term observatories for examination of the mechanisms controlling the formation and dissociation of gas hydrate. Bathymetric mapping with the multibeam echosounder (MBES) SIMRAD EM120 was utilized to conduct high-quality seafloor maps in water depths between 500 and 1000 m, covering an area of 350 km² notably improving the resolution of existing bathymetry. Sub-bottom profiling and plume imaging, visual seafloor observation, lander deployments, sediment coring, CT scanning and biological sampling complemented the research programme (https://oceanrep.geomar.de/13539/1/GEOMAR_Rep_117_SO174.pdf). CI Citation: Paul Wintersteller (seafloor-imaging@marum.de) as responsible party for raw data ingest and approval. Description of the data source: During the SO174 cruise, the hull-mounted parametric sub-bottom profiler ATLAS PARASOUND P7 was used to gather information about the sediment sub-surface and water column. It is utilizing the parametric effect of the non-linear relation of pressure and density during sonar propagation. Data acquisition was performed using measured real-time values of surface sound velocity and a static sound velocity profile of 1500 m/s. Using the software ATLAS PARASTORE, data was displayed and stored as raw .asd files (and its zipped versions .asd.acf with aux-file .asd.acf.idx) and can further be processed and converted into .ps3 / *.sgy file format. The signal penetration varied between 5 to 80 m. Several substrate conditions caused deterioration in signal penetration. Continuous ParaSound sub-bottom profiles were collected from two areas in the southern Gulf of Mexico: a 30 by 55 km area encompassing 5 of the Sigsbee Knolls and 60 by 110 km area encompassing 22 of the northern Campeche Knolls (https://oceanrep.geomar.de/13539/1/GEOMAR_Rep_117_SO174.pdf).

Responsible person during this cruise / PI: P. Blanchon, C. Mortera, A. Gerriets, F. Meier and D. S. Maddox