The U.S. Geological Survey (USGS) Coastal and Marine Geology Program has actively collected geophysical and sedimentological data in the northern Gulf of Mexico for several decades, including shallow subsurface data in the form of high-resolution seismic reflection profiles (HRSP). Prior to the mid-1990s most HRSP data were collected in analog format as paper rolls of continuous profiles up to 25 meters long. As part of the National Geological and Geophysical Data Preservation Program (
https://datapreservation.usgs.gov/), and in collaboration with the Bureau of Ocean Energy Management, Marine Minerals Program, scientists at the USGS St. Petersburg Coastal and Marine Science Center were converting the analog paper records to digital format using a large-format continuous scanner. The image files created by scanning were further processed to fix distortions and crop out blank spaces to create industry standard Society of Exploration Geophysicists date exchange (SEG-Y) format.
This data release serves as an archive of HRSP profiles annotated with header information, converted SEG-Y files, navigation data, and cruise trackline shapefiles. The HRSP data were collected using a minisparker/hydrophone system onboard the research vessel Gyre and a Huntec boomer seismic system onboard research vessels (R/V) Carancahua and Kit Jones. Data collection dates and locations varied between surveys: (1) R/V Carancahua (legs 1 and 2) surveys were conducted July 1–15, 1981, within Chandeleur and Mississippi Sounds, (2) the R/V Gyre 81-6 cruise occurred April 9–23, 1981, in the Gulf of Mexico (south of Mississippi and east of Louisiana), (3) R/V Kit Jones 90 (legs 1 and 2) data were acquired from Mississippi Sound and the Gulf of Mexico (south of Mississippi and Alabama) June 21–27, 1990, and (4) R/V Kit Jones 91-2 HRSP data came from Mississippi Sound (south of Alabama) and the Gulf of Mexico (south of Alabama and Florida) from July 10 to 11 and July 21–27, 1991. Data collection and processing methods are described in USGS Data Series 1047.
To archive all digitized analog boomer seismic profile data and associated files collected along the northern Gulf of Mexico, during the R/V Carancahua, Gyre, and Kit Jones geophysical cruises.
The USGS Saint Petersburg Coastal and Marine Science Center (SPCMSC) currently holds 13 major geophysical surveys from the northern Gulf of Mexico in its paper repository. A conservative estimate of 2,000 line-kilometers (km) of data are available. Paper copies of data are difficult and expensive to duplicate and share with other facilities, and cannot be analyzed using standard GIS and interpretative software. Conversion of this data into a usable digital format is necessary to archive the geologic information that otherwise might be lost, requiring additional redundant and expensive marine geophysical surveys. The USGS National Geological and Geophysical Data Preservation Program (NGGDPP,
http://datapreservation.usgs.gov) addresses the need to preserve, catalog, and provide access to geological and geophysical data for scientific research and economic development. In addition to the current efforts under the NGGDPP, four geophysical investigations from the 1980s and 1990s were previously archived through a preservation project in collaboration with the Bureau of Ocean Energy Management (Harrison and others, 2007; Sanford and others, 2009a, b, c). The USGS-SPCMSC scans its analog HRSP holdings using a large-format continuous scanner. The analog to digital conversion process used for this dataset is similar to the processes used previously in Harrison and others (2007) and Sanford and others (2009a, b, c). The digital files were converted into Tagged Image File Format (TIFF) for standard accessibility by raster image processors. The TIFF images of the seismic profiles were also converted into SEG-Y format. This standard non-proprietary format is the accepted industry standard for seismic data, and can be accessed by all major seismic data processing and interpretation systems. Accompanying the HRSP are navigation and metadata files, which are generated for use in GIS, database and Internet Message Access Protocol (IMAP) services. Processed seismic profile images are also provided. The processed profiles provided in this data release are Portable Document Format (PDF) images that were created using Seismic Unix and/or Imagemagick software.
The northern Gulf of Mexico is a passive continental margin, where minimal structural change to the shallow stratigraphy has occurred during the last few thousand years (Anderson and others, 2004). Therefore, subsurface data collected from this environment for the purposes of geologic assessment can be considered useful in perpetuity. The geologic information collected by the USGS in the northern Gulf of Mexico remains a valuable resource for sea floor and stratigraphic investigations, and is continuously revisited by researchers interested in Holocene and recent earth processes. For example, decades-old geologic data is commonly used in sediment resource studies in coastal Louisiana (for example, Kindinger and others, 2001; Kulp and others, 2002; Rogers and others, 2009) and previously collected datasets across the Mississippi-Alabama shelf have been used in recent geologic-framework assessments (Roberts and others, 2004; Greene and others, 2007; Flocks and others, 2011).
The seismic data for three of the cruises (Carancahua and both Kit Jones) were collected using a single-channel Huntec boomer/benthos hydrophone system with Ocean Research Equipment (ORE) Geopulse power supply. The system consists of an electromechanical sound source mounted on a catamaran sled towed behind the vessel at the water surface. The seismic data for the Gyre cruise were collected using a minisparker/hydrophone system. Sparkers create sound waves from a collapsing bubble, which is a result of vaporizing water between a positive and negative leads (Trabant, 1984). The signal emitted from either sound source is received by a 5 meter (m)-long hydrophone streamer towed alongside the sled. The received signal was recorded in one of two ways. For older cruises, the signal went straight to a graphic recorder, while in the most recent cruises, the signal is processed into response amplitudes via a topside computer running the acquisition software; the settings varied by cruise for both methods. The seismic returns were printed onto paper rolls as two-dimensional profiles representing shots horizontally (time along track) and depth (two-way travel time). Geographic positioning of the system was collected using a long-range navigation (LORAN) system and annotated onto the paper copies.
