Raw single-channel seismic reflection images from the Red Sea (RC0911A, 1965)

Scientists aboard R/V Robert Conrad, led by Tom Aitken, collected single-channel analogue seismic reflection data during cruise RC0911A in 1965 with a 25 cubic-inch airgun and short hydrophone streamer. Despite their age, the data have good resolution. They reveal seismic stratigraphy within the Plio-Pleistocene sediments overlying the "S-reflection", which is commonly taken to mark the top of the Miocene evaporites in the Red Sea or perhaps a little above them. The data in places also reveal some of the uppermost layered Miocene evaporites, erosional unconformities at the S-reflection and possible salt diapirs. The seismic profiles extend from the entrance to the Bab el Mandeb Strait in the Gulf of Aden to the Gulf of Suez. Data quality deteriorates towards the northern end of the transect. Electrical recordings from the hydrophone streamer were recorded in two channels onto paper (one with high amplifier gain and one with low amplifier gain). Navigation is unknown though likely combined celestial and dead-reckoning. The paper sheets were scanned by Neil Mitchell at Lamont in June 2014 with the help of Rose Anne Weissel. Individual data sheets were too big for the scanner (a 600 dpi Tokia photocopier). So, each sheet was scanned twice, covering both ends of each sheet. The dates are given at the base of each sheet and are in day-month-year format (with the month given in Roman numerals). Other annotation, such as times of vessel alter course (A/c) and coring stations, are also given at the base of each sheet. Annotated times are local, not UTC. The time offset appears to be 3 hours (ship time was 3 hours ahead of UTC). The time conversion may be checked by comparing the seabed profile against that in GeoMapApp (the "Blue book" version of the data under Portals > "Analog Seismic Reflection Profiles" menu is correctly aligned) or against the bathymetry in MGD77 files. Horizontal lines on the sheets are at every 0.5 seconds of Two-Way Travel Time (TWTT). These images are in JPEG image format (greyscale), and the files are in image pairs, labelled a and b, with one a/b pair corresponding to one seismic reflection data sheet. The numerical parts of the file names are in sequence following the survey time, hence the first file, RC0911A_01a, was collected at the start of the survey near the Bab el Mandeb Strait in the south. Higher file numbers are progressively further north, until RC0911A_45a, which was collected in the Gulf of Suez at the end of the survey.