U.S. Geological Survey Unpublished material raster digital data Woods Hole Coastal and Marine Science Center, Woods Hole, MA U.S. Geological Survey, Coastal and Marine Geology Program The online link is to the field activity page. See the supplemental information and distribution section for additional information regarding viewing and downloading the data. https://cmgds.marine.usgs.gov/fan_info.php?fan=2006-015-FA In 2006 and 2007, the U.S. Geological Survey, in partnership with Louisiana Department of Natural Resources and the University of New Orleans, conducted geologic mapping to characterize the sea floor and shallow subsurface stratigraphy offshore of the Chandeleur Islands in Eastern Louisiana. The mapping was carried out during two cruises on the R/V Acadiana. Data were acquired with the following equipment: an SEA Ltd SwathPlus interferometric sonar (234 kHz), Klein 3000 dual frequency sidescan sonar, and an Edgetech 512i chirp subbottom profiling system. The long-term goal of this mapping effort is to produce high-quality geologic maps and geophysical interpretations that can be utilized to investigate the impact of Hurricane Katrina in 2005 and to identify sand resources within the region. These chirp seismic-reflection data were collected to use for interpretation of shallow subsurface stratigraphy offshore the Chandeleur Islands, Louisiana. For more information on the seismic surveys see https://cmgds.marine.usgs.gov/fan_info.php?fan=2006-015-FA. These data are also available via GeoMapApp (http://www.geomapapp.org/) and Virtual Ocean ( http://www.virtualocean.org/) earth science exploration and visualization applications. The JPEG format of these data (along with other data associated with this field activity) were released through the Open-File Report 2008-1195 (https://pubs.usgs.gov/of/2008/1195/). See the cross-reference for full citation information. 20060708 20060719 ground condition Complete None planned -88.902069 -88.751057 30.118149 29.704002 USGS Metadata Identifier USGS:3d8d44eb-ca7f-4c7b-951f-88aee4494542 None U.S. Geological Survey USGS Woods Hole Science Center WHSC Coastal and Marine Geology Program CMGP seismic-reflection SEGY profiles seismic subbottom image chirp WHSC field activity serial number 06015 ISO 19115 Topic Category geoscientificInformation oceans imageryBaseMapsEarthCover USGS Thesaurus sub-bottom profiling marine geophysics None Louisiana Chandeleur Islands Breton Island Gosier Island Curlew Island Mississippi River Gulf Outlet New Harbor Islands North Islands North-Central Gulf Coast United States Gulf of Mexico MRGO none Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey as the originator of the dataset. David C. Twichell U.S. Geological Survey Oceanographer mailing and physical address

384 Woods Hole Rd.

Woods Hole MA 02543-1598 (508) 548-8700x2266 (508) 457-2310 dtwichell@usgs.gov https://pubs.usgs.gov/of/2008/1195/images/seis_imag.jpg JPEG image of a chirp seismic-reflection profile JPEG Microsoft Windows XP Professional x64 Edition Version 2003 Service Pack 2 John Stockwell 2008 document Golden, CO Center for Wave Phenomena - Colorado School of Mines http://www.cwp.mines.edu/cwpcodes/index.html Paul Henkart 2007 document LaJolla, CA Scripps Institution of Oceanography, University of California - San Diego http://sioseis.ucsd.edu/index.html Michael W. Norris and Alan K. Faichney 2002 document Tulsa, OK Society of Exploration Geophysicists http://www.seg.org/documents/10161/77915/seg_y_rev1.pdf Wayne E. Baldwin Elizabeth A. Pendleton David C. Twichell 2009 1.0 raster digital data Open-File Report 2008-1195 Reston, VA U.S. Geological Survey https://pubs.usgs.gov/of/2008/1195/ Processed seismic data were converted to JPEG format for ease of seismic trace display. Quality control was conducted during processing. All acquired seismic data were processed and JPEG images produced. The SB-0512i was towed approximately 6 m astern and approximately 1.5 m below the sea surface. DGPS navigation (assumed to be accurate within 1-2 m) was obtained from the receiver mounted above the interferometric sonar head, but towfish layback was not accounted for. The layback of the towfish adds additional uncertainty due to changes in angle and scope of the tow cable in response to sea state and vessel speed. Based on horizontal offsets between the fish and GPS receiver, and fish motion behind the vessel, the resulting horizontal accuracy is assumed to be +/- 20 m. U.S. Geological Survey unknown disc 20060708 20060719 ground condition Information unavailable from original metadata. Approximately 1900 km of high-resolution chirp seismic-reflection profiles were collected using an EdgeTech Geo-Star FSSB system and an SB-0512i towfish (0.5-12 kHz) on the R/V Acadiana of Loreauville, LA. SB-Logger acquisition software (Triton Imaging Inc. http://www.tritonimaginginc.com/site/content/products/sblogger/index.htm) was used to control the Geo-Star topside unit and digitally log trace data in the SEG-Y rev. 1 standard format. Data were acquired using a 0.25-s fire rate, a 20-ms pulse length, and a 0.7 to 12 kHz sweep (swept frequency). Tracklines are spaced 100 to 125 m apart in the shore parallel direction and about 1 km apart in the shore perpendicular direction. A script was run that used SIOSEIS (version 96.4) to shift all traces by -2 ms vertically to account for the position of the 512i towfish beneath the sea surface. A second SIOSEIS script was used to predict the vertical location of the sea floor by identifying peak amplitudes within a vertical window. Two-way travel times (milliseconds) to the sea floor at each trace were recorded to an ASCII text file. 2006 Wayne E. Baldwin U.S. Geological Survey Geologist mailing and physical address

384 Woods Hole Rd.

Woods Hole MA 02543-1598 (508) 548-8700x2226 (508) 457-2310 wbaldwin@usgs.gov All SEG-Y trace data were imported into Seisworks 2-D(version R2003.12.0; Landmark Graphics Corp.), a 2-dimensional, digital seismic interpretation software, and seafloor values were imported as Seisworks horizon data. Spurious seafloor values were edited for discrete traces through heads-up digitization of the Seisworks horizon, and corrected values were exported to a new ASCII text file. 2006 Wayne E. Baldwin U.S. Geological Survey Geologist mailing and physical address

384 Woods Hole Rd.

Woods Hole MA 02543-1598 (508) 548-8700x2226 (508) 457-2310 wbaldwin@usgs.gov An additional script was run that used SIOSEIS to remove sea surface heave and mute water column portions of the traces by: 1) loading the corrected seafloor times into the SEG-Y trace headers; 2) smoothing the sea floor picks using an along-track filter that approximates twice the period of sea surface heave to be removed (the filter window was set to use 46 traces); 3) creating a series of difference values between the raw and smoothed seafloor picks for each trace; 4) shifting traces up or down according to the difference values; and 5) muting each trace between time zero and the time of the smoothed sea floor pick, thus removing noise within the water column. Changes to the traces within each profile were saved to new "heave corrected" SEG-Y files, which were used for creation of jpeg browse images and digital interpretation. 2006 Wayne E. Baldwin U.S. Geological Survey Geologist mailing and physical address

384 Woods Hole Rd.

Woods Hole MA 02543-1598 (508) 548-8700x2226 (508) 457-2310 wbaldwin@usgs.gov A script was run that used Seismic Unix (version 4.1) to read the SEG-Y files and plot the data as 8-bit gray scale Postscript files using the Seismic Unix 'psimage' algorithm. All images were created with a horizontal scale of 200 traces per inch. Images were plotted within a constant 8-inch vertical window of 50 milliseconds (Two-Way Travel Time) duration, yielding a vertical resolution of about 8.3 milliseconds per inch. The Postscript images were then converted to JPEG format using ImageMagick (version 5.5.6). 2006 Wayne E. Baldwin U.S. Geological Survey Geologist mailing and physical address

384 Woods Hole Rd.

Woods Hole MA 02543-1598 (508) 548-8700x2226 (508) 457-2310 wbaldwin@usgs.gov Edits to the metadata were made to fix any errors that MP v 2.9.36 flagged. This is necessary to enable the metadata to be successfully harvested for various data catalogs. In some cases, this meant adding text "Information unavailable" or "Information unavailable from original metadata" for those required fields that were left blank. Other minor edits were probably performed (title, publisher, publication place, etc.). Attempted to modify http to https where appropriate. Fixed an online link in a cross-reference. The distribution format name was modified in an attempt to be more consistent with other metadata files of the same data format. The source information was incomplete and had to be modified to meet the standard. The metadata date (but not the metadata creator) was edited to reflect the date of these changes. The metadata available from a harvester may supersede metadata bundled within a download file. Compare the metadata dates to determine which metadata file is most recent. 20170228 U.S. Geological Survey VeeAnn A. Cross Marine Geologist Mailing and Physical

384 Woods Hole Road

Woods Hole MA 02543-1598 508-548-8700 x2251 508-457-2310 vatnipp@usgs.gov This metadata record was modified from one describing JPEG images to reflect the SEG-Y version of the same data (Open-File Report 2008-1195, https://pubs.usgs.gov/of/2008/1195/). Changes were made to the Citation and Distribution_Information. 20171121 U.S. Geological Survey VeeAnn A. Cross Marine Geologist Mailing and Physical

384 Woods Hole Road

Woods Hole MA 02543-1598 508-548-8700 x2251 508-457-2310 vatnipp@usgs.gov USGS Thesaurus keywords added to the keyword section. 20180720 U.S. Geological Survey VeeAnn A. Cross Marine Geologist Mailing and Physical

384 Woods Hole Road

Woods Hole MA 02543-1598 508-548-8700 x2251 508-457-2310 vatnipp@usgs.gov Added keywords section with USGS persistent identifier as theme keyword. 20200908 U.S. Geological Survey VeeAnn A. Cross Marine Geologist Mailing and Physical

384 Woods Hole Road

Woods Hole MA 02543-1598 508-548-8700 x2251 508-457-2310 vatnipp@usgs.gov Raster pixel Wayne E. Baldwin U.S. Geological Survey Geologist mailing and physical address

384 Woods Hole Rd.

Woods Hole MA 02543-1598 (508) 548-8700x2226 (508) 457-2310 wbaldwin@usgs.gov Downloadable Data Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. SEG-Y Link is to a folder containing SEG-Y files. https://cmgds.marine.usgs.gov/data/2006_015_FA/ The online link gives access to the folder containing the individual SEG-Y files. none These data require software that can read SEG-Y data. 20240318 Wayne E. Baldwin U.S. Geological Survey Geologist mailing and physical address

384 Woods Hole Rd.

Woods Hole MA 02543-1598 (508) 548-8700x2226 (508) 457-2310 whsc_data_contact@usgs.gov The metadata contact email address is a generic address in the event the person is no longer with USGS. (updated on 20240318) FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998 local time None None