Computed Tomography (CT) scans of sediment cores collected from Montague Island, AK

Frequently anticipated questions:

• What does this data set describe?
  1. How might this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How might this data set be cited?
   Witter, Robert C., SeanPaul M. La Selle, DePaolis, Jessica, Haeussler, Peter J., Bender, Adrian M., Curran, Janet H., and Dura, Tina, 20240326, Computed Tomography (CT) scans of sediment cores collected from Montague Island, AK: data release DOI:10.5066/P13RVDJZ, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

   Online Links:

   • https://doi.org/10.5066/P13RVDJZ

   This is part of the following larger work.
   Witter, Robert C., SeanPaul M. La Selle, DePaolis, Jessica, Haeussler, Peter J., Bender, Adrian M., Curran, Janet H., and Dura, Tina, 2024, Computed Tomography (CT) scans of sediment cores collected from Montague Island, AK: data release DOI:10.5066/P13RVDJZ, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, CA.

   Online Links:

   • https://doi.org/10.5066/P13RVDJZ

   Other_Citation_Details:

   Suggested Citation: Witter, R.C., La Selle, S.M., DePaolis, J., Haeussler, P.J., Bender, A.M., Curran, J.H., Dura, T., 2024, Computed Tomography (CT) scans of sediment cores collected from Montague Island, AK: U.S. Geological Survey data release, https://doi.org/10.5066/P13RVDJZ.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -147.32948
   East_Bounding_Coordinate: -147.30783
   North_Bounding_Coordinate: 60.17820
   South_Bounding_Coordinate: 60.19528
   

3. What does it look like?

   montague_ct_preview.png (PNG)

   Preview of a CT image from core 19HL-24, with a false colormap applied to CT intensity values.

4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 10-Jul-2019

   Ending_Date: 10-Oct-2019

   Currentness_Reference:

   Ground conditions at time data were collected

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form: raster digital data
   

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (6)
   2. What coordinate system is used to represent geographic features?
      

      Vertical_Coordinate_System_Definition:

      Depth_System_Definition:

      Depth_Datum_Name: Local surface
      Depth_Resolution: 1.0
      Depth_Distance_Units: centimeters
      Depth_Encoding_Method: Attribute values
      

7. How does the data set describe geographic features?

   montague_ct.zip

   A zip file containing 6 TIFF files of CT images and their respective software-proprietary XML files. (Source: Producer defined)

   orthogonal CT image metadata XML file

   This Geotek software-proprietary XML file contains information on CT scan acquisition settings and reconstruction settings. The following attributes and example attribute values are provided: <geotek-image> <image-type>giCTOrthogonalView</image-type> <coreID>19CR-10</coreID> <section-number>1</section-number> <physical-width>7.55</physical-width> <physical-height>101.23</physical-height> <physical-top>0.01</physical-top> <pixels-per-CM>125</pixels-per-CM> <horizontal-resolution>125</horizontal-resolution> <pixel-width>944</pixel-width> <scan-lines>12606</scan-lines> <comments></comments> <camera-name>Thermo Kevex PSX10-65W</camera-name> <average-of>1</average-of> <filename>montague_ct_10CR-10-02.tif</filename> <x-ray-voltage>130</x-ray-voltage> <x-ray-current>308.5</x-ray-current> <x-ray-spot-size>58</x-ray-spot-size> <source-object-distance>199.73</source-object-distance> <source-detector-distance>630.01</source-detector-distance> <detector-CCD-mode>2x2</detector-CCD-mode> <image-enhancement-filter>Enabled=False,WindowCount=2,Window=400,SigmaA=0.1,SigmaV=0.0005,Weight=0.4,Window=100,SigmaA=0.1,SigmaV=0.0005,Weight=1,Reduction=0.85</image-enhancement-filter> <is-a-sync-scan-image>0</is-a-sync-scan-image> </geotek-image> (Source: producer defined) These Geotek software-proprietary XML files contain information on CT scan acquisition settings and image scaling information. The values in the example provided may be different for each scan. Please contact the PCMSC data coordinator for more information on the contents of these XML files.

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Robert C. Witter
   • SeanPaul M. La Selle
   • Jessica DePaolis
   • Peter J. Haeussler
   • Adrian M. Bender
   • Janet H. Curran
   • Tina Dura
2. Who also contributed to the data set?
3. To whom should users address questions about the data?
   PCMSC Science Data Coordinator

   U.S. Geological Survey, Pacific Coastal and Marine Science Center

   2885 Mission Street

   Santa Cruz, CA
   

   831-427-474 (voice)

   pcmsc_data@usgs.gov

Why was the data set created?

How was the data set created?

1. From what previous works were the data drawn?
2. How were the data generated, processed, and modified?

   Date: 2019 (process 1 of 2)

   Sediment cores were collected from coastal environments on Montague Island, Alaska using a hand-driven peat sampler at two sites: 'Hidden Lagoons' and 'Crescent'. At each core site, two adjacent bore holes were used to sample sediment in 50 cm intervals. Coring alternated between the two bore holes to avoid sampling the approximately 7 cm of disturbed sediment induced by the “nose” at the bottom of the peat sampler. After core extraction, sediment in the auger was transferred to an approximately 5 cm diameter plastic sleeve (50 cm long, 2 inch diameter polyvinyl chloride (PVC) pipe cut lengthwise) and wrapped in plastic. Sampling depths were targeted to bracket specific stratigraphic layers. The cores in this data release therefore do not represent the entire stratigraphic sequence at each core site. Cores were transported back to the USGS Pacific Coastal and Marine Science Center core lab for subsequent CT analyses.

   Date: 2019 (process 2 of 2)

   CT scans were acquired at the USGS Pacific Coastal and Marine Science Center core facility using a Geotek Rotating X-Ray CT (RXCT) Scanner system, running acquisition software version XCT4. Rotational x-ray images were acquired with a Thermo Kevex PSX10-65W x-ray source every 0.2 degrees at 130 kilovolts (kV) and 308 microamperes. Core segments were scanned in batches of two to three segments. Rotational images were reconstructed into axial slice TIFFs using Geotek’s Reconstructor Software. Once reconstructed, the axial slice TIFFs were imported into GeoTek's Image Viewer software and a representative two-dimensional orthogonal view was selected. TIFFs are provided in 16-bit unsigned integer, single channel format. Scaling information is embedded in the TIFF files and also provided in the associated XML files. File names correspond to the names of the cores within each scan. For example, ‘montague_ct_10HL-22.tif' corresponds to the CT image of core segments from the core location '10HL-22'. 'HL' refers to the Hidden Lagoon site, while 'CR' refers to the 'Crescent' site. The support file, 'montague_ct_supportfile.pdf' provided in this data release illustrates the position of each individual core segment in the CT scan images.

3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

1. How well have the observations been checked?
   Quality control of attribute accuracy was conducted during field data collection and processing workflows. No formal attribute accuracy tests were conducted.
2. How accurate are the geographic locations?
   
3. How accurate are the heights or depths?
   Core depth values are relative to the top of sediment surface at the time of core collection. Coring-induced compaction, if any, was not determined. No formal vertical accuracy tests were conducted.
4. Where are the gaps in the data? What is missing?
   Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details.
5. How consistent are the relationships among the observations, including topology?
   No formal logical consistency tests were conducted.

How can someone get a copy of the data set?

1. Who distributes the data set? (Distributor 1 of 1)
   
   U.S. Geological Survey - CMGDS

   2885 Mission Street

   Santa Cruz, CA
   

   United States

   831-427-4747 (voice)

   pcmsc_data@usgs.gov
2. What's the catalog number I need to order this data set? CT images are provided in a zip archive (montague_ct.zip) with CSDGM FGDC compliant metadata. Please contact the PCMSC Data Coordinator about availability of full 3D CT scan volumes.
3. What legal disclaimers am I supposed to read?
   Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty.
4. How can I download or order the data?
   • Availability in digital form:

     Data format:	Zip file contains CT core imagery in TIFF format and associated proprietary metadata in XML format. in format TIFF, XML (version Geotek RXCT Scanner system, software version XCT4) Size: 119
     Network links:	https://doi.org/10.5066/P13RVDJZ

   • Cost to order the data: None.

5. What hardware or software do I need in order to use the data set?
   CT images can be viewed with any standard image software. Proprietary metadata XML files can be viewed with any standard text editing software.

Who wrote the metadata?

Dates:

Last modified: 29-Mar-2024

Metadata author:

U.S. Geological Survey, Pacific Coastal and Marine Science Center

Attn: PCMSC Science Data Coordinator

2885 Mission Street

Santa Cruz, CA

831-427-4747 (voice)

pcmsc_data@usgs.gov

Metadata standard:

Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)