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Thickness of Glacial Sediments in Connecticut and the Long Island Sound Basin Line

Frequently-asked questions:


What does this data set describe?

Title:
Thickness of Glacial Sediments in Connecticut and the Long Island Sound Basin Line

Abstract:
The Thickness of Glacial Sediments in Connecticut and the Long Island Sound Basin layer contains interpretive polygon data representing the thickness of glacial sediments in Connecticut and the Long Island Sound Basin. Compiled as part of the Quaternary Geologic Map of Connecticut and Long Island Sound Basin, Stone and others (1998, 2005). Includes thickness of glacial sediments in 50 foot (0-50, 50-100) and then 100 foot (100-200, 200-300, etc) intervals.

Data derived from original mapping at 1:80,000 scale for the Long Island Sound basin and at 1:125,000 scale on the land in Connecticut. The data are NOT recommended for use at higher resolution scales.

Supplemental information:
These data appear as figure 2 on sheet 2 of the Quaternary Geologic Map of Connecticut and Long Island Sound Basin, Stone and others, 2005.

Glacial and postglacial geologic deposits have long been studied on the land in Connecticut. Similar deposits are also present beneath modern marine sediments in Long Island Sound. Offshore geologic units in Long Island Sound are mapped largely from analysis of seismic-reflection profile data instead of from direct observation. 

The wasting away of the late Wisconsinan ice sheet, and the recession of its margin from south to north across Long Island Sound and Connecticut, was initiated when the rate of melting along the glacial margin exceeded the rate at which ice was flowing in from the north. Newly exposed lowlands and valleys were immediately filled with meltwater in the form of glacial lakes and ponds and meltwater streams.  In these meltwater settings, much of the unsorted glacial debris (till) that melted out of the ice was sorted into layers of gravel, sand, silt, and clay.

Glacial Lake Connecticut was impounded behind the Harbor Hill-Fishers Island- Charlestown moraine. At its maximum extent (when the ice front stood at a position near the present Connecticut shoreline) this glacial lake occupied all of the Long Island Sound Basin and extended into the mouths of the surrounding river valleys. The extensive glacial lake deposits that accumulated in Glacial Lake Connecticut often exceed 100m (328 ft) in thickness, and at one time very nearly completely filled in the Long Island Sound Basin. Today, these deposits have been locally extensively scoured by tidal currents (primarily in the eastern Sound) and generally lie beneath a blanket of Holocene marine sediment that is a few to 15m (45 ft) in thickness. 

To the north, Glacial Lake Hitchcock occupied the Central Valley north of Middletown, and smaller lakes and ponds occupied most river valleys. As meltwater streams carried sediment away from the receding ice front, these lakes and ponds were filled with sequences of stratified glacial deposits (most often deltaic), which choked the valleys. In upland areas, thick till deposits (e.g. drumlins) are locally scattered across the bedrock controlled topography which is generally mantled by a thin blanket of till (generally less than 5m or 15ft thick).

  1. How should this data set be cited?

    Long Island Sound Resource Center, a partnership between the State of Connecticut, Department of Environmental Protection and the University of Connecticut (compiler, editor and publisher), U.S. Geological Survey (source data compiler), 200407, Thickness of Glacial Sediments in Connecticut and the Long Island Sound Basin Line: State of Connecticut, Department of Environmental Protection, Long Island Sound Resource Center, Groton, Connecticut, USA.

    Online links:
    Other citation details:
    The USGS is the collector and source for the original geologic mapping and interpretation upon which this digital spatial data is based (source data compiler). The Long Island Sound Resource Center is the creator, maintainer, and producer of the digital spatial data (compiler, editor, publisher).

    This is part of the following larger work:

    Janet Radway Stone, John P. Schafer, Elizabeth Haley London, Mary L. DiGiacomo-Cohen, Ralph S. Lewis, Woodrow B. Thompson, 2005, Quaternary Geologic Map of Connecticut and Long Island Sound Basin: Scientific Investigations MapSIM-2784, U.S. Geological Survey, Reston, VA.

  2. What geographic area does the data set cover?

    Bounding coordinates:
    West: -73.785122
    East: -71.781364
    North: 42.052612
    South: 40.852372

  3. What does it look like?

    http://www.cteco.uconn.edu/metadata/dep/browsegraphic/glacialsedimentthickness.gif (GIF)
    Full view of the Thickness of Glacial Sediments in Connecticut and the Long Island Sound Basin layer showing nature and extent of polygon and line feature data.

    http://www.cteco.uconn.edu/metadata/dep/browsegraphic/glacialsedimentthicknessdetail.gif (GIF)
    Detail view of the Thickness of Glacial Sediments in Connecticut and the Long Island Sound Basin layer showing nature and extent of polygon and line feature data on the land in Connecticut at 1:125,000 scale.

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

    Calendar date: 200407
    Currentness reference:
    publication date

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

    Geospatial data presentation form: vector digital data

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • String (2383)

    2. What coordinate system is used to represent geographic features?

      The map projection used is Lambert Conformal Conic.

      Projection parameters:
      Lambert Conformal Conic
      Standard parallel: 41.200000
      Standard parallel: 41.866667
      Longitude of central meridian: -72.750000
      Latitude of projection origin: 40.833333
      False easting: 999999.999996
      False northing: 499999.999998

      Planar coordinates are encoded using coordinate pair.
      Abscissae (x-coordinates) are specified to the nearest 0.000250.
      Ordinates (y-coordinates) are specified to the nearest 0.000250.
      Planar coordinates are specified in survey feet.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.

      Vertical coordinate system definition:
      Altitude system definition:
      Altitude resolution: 1.000000
      Altitude encoding method: Explicit elevation coordinate included with horizontal coordinates

  7. How does the data set describe geographic features?

    Thickness of Glacial Sediments in Connecticut and the Long Island Sound Basin Line
    Lines of equal glacial sediment thickness (Source: State of Connecticut, Department of Environmental Protection and the U.S Geological Survey)

    OBJECTID
    Internal feature number. (Source: ESRI)
                      

    Sequential unique whole numbers that are automatically generated.

    SHAPE
    Feature geometry. (Source: ESRI)
                      

    Coordinates defining the features.

    THICK_FT
    Thickness Isopach - Glacial Sediment Thickness Isopach, in feet. (Source: Long Island Sound Resource Center compiler, Mary DiGiacomo-Cohen)
                      

    ValueDefinition
    50
    50 feet thick
    100
    100 feet thick
    200
    200 feet thick
    300
    300 feet thick
    400
    400 feet thick
    500
    500 feet thick
    600
    600 feet thick
    999
    Data limit. Not an isopach.

    SHAPE.len
    Entity and attribute overview:
    Line features are encoded for glacial sediment thickness in feet (50, 100, 200, 300, 400, 500, and 600). Line features that are encoded with sediment thickness values of 9999 define the (boundary) limits of the data and are not thickness isopach lines. They generally define the extremity of the data, following the Connecticut state boundary and southern boundary of the Long Island Sound basin. They also enclose areas where the glacial sediment thickness is unknown. 
    
    Polygon features are encoded for glacial sediment thickness interval in feet (0-50, 50-100, 100-200, 200-300, 300-400, 400-500, 500-600, > 600, and unkown). Values of "unknown" represent areas where the presence of methane gas in the sediment makes the interpretation of underlying layers difficult or impossible.

    Entity and attribute detail citation:
    Quaternary Geologic Map of Connecticut and Long Island Sound Basin (Stone, J.R., Schafer, J.P., London, E.H., DiGiacomo-Cohen, M.L., Lewis, R.S., and Thompson, W.B., 2005, U.S. Geological Survey special map, 2 sheets, scale 1:125,000).
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Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)


  2. Who also contributed to the data set?

    Mary DiGiacomo-Cohen (Long Island Sound Resource Center) for compiling and editing the digital data.  Original research conducted by USGS and Connecticut Geological and Natural History Survey Cooperative Mapping Program; contributing authors include Janet R. Stone, Sally Needell, Ralph S. Lewis, Nancy F. Neff, and Steven M. Colman.

  3. To whom should users address questions about the data?

    Mary DiGiacomo-Cohen
    Long Island Sound Resource Center
    Long Island Sound Resource Center
    UConn Avery Point
    1080 Shennecossett Rd
    Groton, Connecticut 06340
    USA

    (860)405-9015 (voice)
    lisrc@uconn.edu
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Why was the data set created?

The purpose is to show the thickness of glacial sediments on land in Connecticut and in the Long Island Sound Basin. This layer can be used other geologic information shown on the Quaternary Geologic Map of Connecticut and Long Island Sound Basin (USGS publication SIM-2784) as well as other geologic GIS data layers for Long Island Sound derived from the U.S. Geological Survey (USGS) / Connecticut Department of Environmental Protection (DEP) Marine Geology Cooperative Program. Complimentary data layers include the marine transgressive surface (marinet) and thickness of postglacial deposits (pgthkpol) found on Georeferenced Sea-floor Mapping and Bottom Photography in Long Island Sound (USGS Openfile report 00-304).

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How was the data set created?

  1. Where did the data come from?

    MF-1939-A (source 1 of 7)

    Ralph S. Lewis, Sally W. Needell, 19870101, Maps showing the stratigraphic framework and Quaternary geologic history of eastern Long Island Sound: U.S. Geological Survey Miscellaneous Field Studies MapMF-1939-A, U.S. Geological Survey, Hartford, Connecticut, USA.

    Type of source media: stable-base material
    Source scale denominator: 80000
    Source contribution:
    mylar compilation sheet for thickness of glacial drift

    MF-1939-B (source 2 of 7)

    Sally W. Needell, Ralph S. Lewis, Steven M. Colman, 19870101, Maps showing the Quaternary geology of east-central Long Island Sound: U.S. Geological Survey Miscellaneous Field Studies MapMF-1939-B, U.S. Geological Survey, Reston, Virginia, USA.

    Type of source media: stable-base material
    Source scale denominator: 80000
    Source contribution:
    mylar compilation sheet for thickness of glacial drift

    mylars for west and west-central LIS (source 3 of 7)

    Ralph S. Lewis, Nancy F. Neff, Unpublished Material, unpublished maps for west and west-central LIS: Long Island Sound Resource Center, Groton, Connecticut, USA.

    Other citation details:
    These maps were prepared as a continuation of the MF-1939 series which was not completed in that format since the framework studies of LIS evolved into other publications such as the Quaternary map (I-2784) and various openfile CD products (OF 02-002, OF 00-304).

    Type of source media: stable-base material
    Source scale denominator: 80000
    Source contribution:
    Unpublished contour maps of the total drift thickness for western and west-central LIS

    CT thickness map (source 4 of 7)

    Janet R. Stone, Unpublished Material, CT thickness of glacial sediments: U.S. Geological Survey, Hartford, Connecticut, USA.

    Other citation details:
    mylar overlay for the Quaternary map (on-land area) drafted at 1:125,000 scale

    Type of source media: stable-base material
    Source scale denominator: 125000
    Source contribution:
    mylar compilation sheet of thickness of glacial deposits

    glacialthk (source 5 of 7)

    Long Island Sound Resource Center, a partnership between the State of Connecticut, Department of Environmental Protection and the University of Connecticut (compiler, editor and publisher), 200407, Thickness of Glacial Sediments in Connecticut and the Long Island Sound Basin: State of Connecticut, Department of Environmental Protection, Long Island Sound Resource Center, Groton, Connecticut, USA.

    Online links:
    Type of source media: disc
    Source scale denominator: 80000 and 125000
    Source contribution:
    glacialthk is in ArcInfo Coverage format having both polygon and line features. The name of the ArcInfo Coverage is GLACIALTHK.

    Glacial_Sediment_Thickness_Line.shp (source 6 of 7)

    Long Island Sound Resource Center, a partnership between the State of Connecticut, Department of Environmental Protection and the University of Connecticut (compiler, editor and publisher), U.S. Geological Survey (source data compiler), 200407, Thickness of Glacial Sediments in Connecticut and the Long Island Sound Basin Line: State of Connecticut, Department of Environmental Protection, Long Island Sound Resource Center, Groton, Connecticut, USA.

    Online links:
    Type of source media: disc
    Source scale denominator: 80000 and 125000
    Source contribution:
    Includes all line features from glacialthk (ArcInfo Coverage format).  Glacial_Sediment_Thickness_Line.shp is in Shapefile format.

    Glacial_Sediment_Thickness_Line (source 7 of 7)

    Long Island Sound Resource Center, a partnership between the State of Connecticut, Department of Environmental Protection and the University of Connecticut (compiler, editor and publisher), U.S. Geological Survey (source data compiler), 200407, Thickness of Glacial Sediments in Connecticut and the Long Island Sound Basin Line: State of Connecticut, Department of Environmental Protection, Long Island Sound Resource Center, Groton, Connecticut, USA.

    Online links:
    Type of source media: disc
    Source scale denominator: 80000 and 125000
    Source contribution:
    Glacial_Sediment_Thickness_Line is in GeoDatabase Feature Class format.

  2. What changes have been made?

    Date: 1994 (change 1 of 6)
    Selected contours from the hand drawn compilation sheets (4 maps total, originaly with 10m contour intervals) for LIS were digitized on a Calcomp 9100 using ArcInfo software. The section coverages were edited and edgematched (contours were modified where necessary to match at map section boundaries), and attributed. Coverage was projected to Connecticut State Plane Coordinate System, NAD27.

    Person responsible for change:
    Mary DiGiacomo-Cohen
    Long Island Sound Resource Center
    Long Island Sound Resource Center
    UConn Avery Point
    1080 Shennecossett Rd
    Groton, CT 06340
    USA

    (860)405-9015 (voice)
    lisrc@uconn.edu

    Data sources used in this process:
    • MF-1939-A
    • MF-1939-B
    • mylars for west and west-central LIS

    Data sources produced in this process:
    • LISthickness

    Date: 1994 (change 2 of 6)
    The CT thickness map was digitized on a Calcomp 9100 using ArcInfo software, edited and attributed. Coverage was projected to Connecticut State Plane Coordinate System, NAD27.

    Person responsible for change:
    Margaret Thomas
    CT Geological and Natural History Survey, CT DEP
    Environmental and Geographic Information Center
    Department of Environmental Protection
    79 Elm St
    Hartford , CT 06106
    USA

    860 424-3583 (voice)
    margaret.thomas@po.state.ct.us

    Data sources used in this process:
    • CT thickness map

    Data sources produced in this process:
    • CTthickness

    Date: 1994 (change 3 of 6)
    Coverages CTthickness and LISthickness were appended and edited as necessary along the shoreline (interpolation by J.R. Stone and M.DiGiacomo-Cohen). 

    Person responsible for change:
    Mary DiGiacomo-Cohen
    Long Island Sound Resource Center
    Long Island Sound Resource Center
    UConn Avery Point
    1080 Shennecossett Rd
    Groton, Connecticut 06340
    USA

    (860)405-9015 (voice)
    lisrc@uconn.edu

    Data sources used in this process:
    • CTthickness
    • LISthickness

    Data sources produced in this process:
    • Comthk

    Date: 2003-2004 (change 4 of 6)
    Edited again in 2003 per review comments by USGS publication editors. Re-attributed and checked. Coverage projected to Connecticut State Plane Coordinate System, NAD83.

    Person responsible for change:
    Mary DiGiacomo-Cohen
    Long Island Sound Resource Center
    Long Island Sound Resource Center
    UConn Avery Point
    1080 Shennecossett Rd
    Groton, Connecticut 06106
    USA

    (860)405-9015 (voice)
    lisrc@uconn.edu

    Data sources used in this process:
    • comthk

    Data sources produced in this process:
    • glacialthk

    Date: 20060519 (change 5 of 6)
    Export to Shapefile format - Converted line feature data from an ArcInfo coverage named GLACIALTHK to a Shapefile named Glacial_Sediment_Thickness_Line.shp. Excluded the FNODE#, TNODE#, LPOLY#, RPOLY#, LENGTH, GLACIALTHK#, GLACIALTHK-ID attributes from the Shapefile because their values are only maintained by ArcInfo software with spatial data that is ArcInfo coverage format.

    Person responsible for change:
    Howie Sternberg
    State of Connecticut, Department of Environmental Protection
    79 Elm Street
    Hartford, Connecticut 06106
    USa

    860-424-3540 (voice)

    Data sources used in this process:
    • glacialthk

    Data sources produced in this process:
    • Glacial_Sediment_Thickness_Line.shp

    Date: 20061106 (change 6 of 6)
    Convert to GeoDatabase Feature Class format - Defined new Feature Class named Glacial_Sediment_Thickness_Line; and imported the attribute definitions, loaded features and imported metadata from Glacial_Sediment_Thickness_Line.shp shapefile. 
    
    Spatial Reference Properties for Feature Class:
    
    Coordinate System: NAD_1983_StatePlane_Connecticut_FIPS_0600_Feet
    XY Domain MinX: 100000; MaxX: 2247483.645
    XY Domain MinY: 200000; MaxY: 2347483.645
    Precision: 1000

    Person responsible for change:
    Howie Sternberg
    State of Connecticut, Department of Environmental Protection
    79 Elm Street
    Hartford, Connecticut 06106
    USA

    860-424-3540 (voice)

    Data sources used in this process:
    • Glacial_Sediment_Thickness_Line.shp

    Data sources produced in this process:
    • Glacial_Sediment_Thickness_Line

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

  1. How well have the observations been checked?

    The THICKI_FT attribute is in feet and for the Long Island Sound area was derived from interpretation of analog seismic records generated by a Uniboom seismic system. The Uniboom employed for this project had a resolution of approximately 1-2 m; original contours were drawn at 10 meter intervals (and reinterpreted or converted to 50 and 100 foot intervals to agree with the onshore mapping interval). Considered accurate for use at appropriate scales.

  2. How accurate are the geographic locations?

    For the Long Island Sound area, ship position was determined using Loran-C navigation (typical Loran accuracy for Long Island Sound is about 100 m). Additional horizontal error may have been introduced during the drafting of original compilation maps or the digitizing process. Data is considered accurate for use at 1:80,000 scale for Long Island Sound and 1:125,000 scale for Connecticut mainland.

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    All available (previously published or compiled) data for the area has been presented. There are data gaps in central Long Island Sound where the presence of gas in the sediments makes the interpretation of underlying layers difficult or impossible. Data gaps are either unmapped areas or represented by polygon features having Thickness Interval  attribute (THICKI_FT) values equal to "unknown".

  5. How consistent are the relationships among the observations, including topology?

    All lines were digitized, edited and coded in a consistent maner. No additional checks for topological consistency were performed on this data set. Polygon features conform to the following topological rules. Polygons are single part. There are no duplicate polygons. Polygons do not self overlap. Polygons do not overlap other polygons. Lines are single part. Line features conform to the following topological rules. There are no duplicate lines. Lines do not self overlap. Lines do not overlap other lines. Lines intersect only at nodes, and nodes anchor the ends of all lines. Lines do not overshoot or undershoot other lines they are supposed to meet and intersect. In general, there are no duplicate features, unresolved intersections, overshooting lines, open polygons, sliver polygons, or unlabeled (unattributed) polygons. The tests of logical consistency were performed by the Long Island Sound Resource Center using ESRI ArcInfo software to maintain feature topology in ArcInfo coverage format. The data is topologically clean. The ArcInfo Clean function was repeatedly used following edits to verify topology and enforce a minimum distance between vertices of 10 feet (fuzzy tolerance) and a minimum allowed overshoot length of 0 feet (dangle length).

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How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access constraints: None. The data are in the public domain and may be redistributed.
Use constraints:
Data derived from original mapping at 1:80,000 scale for the Long Island Sound basin and at 1:125,000 scale on the land in Connecticut. These data are NOT recommended for use at higher resolution scales. Please note that the on-land portion of these data was developed at 1:125,000 scale, and even though it was developed as part of the Quaternary Map and by the same author as the Quaternary Map and the Surficial Materials Map (J.R. Stone) that those digital data layers (quaternary geology and surficial materials) were compiled at 1:24,000 scale - because of the difference in scale and compilation methods these data sets may be noticibly incompatible at inappropriate scales.

Although this data set  has been used by the State of Connecticut, Department of Environmental Protection, no warranty, expressed or implied, is made by the State of Connecticut, Department of Environmental Protection as to the accuracy of the data and or related materials.  The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the State of Connecticut, Department of Environmental Protection in the use of these data or related materials. The user assumes the entire risk related to the use of these data. Once the data are distributed to the user, modifications made to the data by the user should be noted in the metadata. When printing these data on a map or using it in a software application, analysis, or report, please acknowledge the State of Connecticut, Department of Environmental Protection as the source for this information. For example, include the following data source description when printing this layer on a map: Glacial Thickness - From the Thickness of Glacial Sediments in Connecticut and Long Island Sound Basin layer, compiled and published by CT DEP and USGS. Source map scale is 1:80,000 (LIS) and 1:125,000 (CT).

The Long Island Sound Resource Center, CT DEP, and USGS must be referenced as the originator of the dataset in any future products or research derived from these data

Distributor 1 of 1

  1. Who distributes the data set?

    State of Connecticut, Department of Enviromental Protection
    79 Elm Street
    Hartford, Connecticut 06106-5127
    USA

    860-424-3540 (voice)
    860-424-4058 (FAX)
    dep.gisdata@ct.gov
    Hours of Service: Monday to Friday, 08:30 to 16:30 Eastern Standard Time

  2. What's the catalog number I need to order this data set?

    Thickness of Glacial Sediments in Connecticut and the Long Island Sound Basin

  3. What legal disclaimers am I supposed to read?

    Although this data set  has been used by the State of Connecticut, Department of Environmental Protection, no warranty, expressed or implied, is made by the State of Connecticut, Department of Environmental Protection as to the accuracy of the data and or related materials.  The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the State of Connecticut, Department of Environmental Protection in the use of these data or related materials. The user assumes the entire risk related to the use of these data.

  4. How can I download or order the data?

    • Availability in digital form:


    • Data format:
      in format Shapefile, Feature Class, ArcInfo Coverage (version ArcGIS)
      Network links:http://www.ct.gov/deep

    • Cost to order the data: An online copy of the data may be accessed without charge.


  5. Is there some other way to get the data?

    The data distributor does not provide custom GIS analysis or mapping services. Data is available in a standard format and may be converted to other formats, projections, coordinate systems, or selected for specific geographic regions by the party receiving the data.

  6. What hardware or software do I need in order to use the data set?

    Geographic information sytem (GIS), computer-aided drawing or other mapping software is necessary to display, view and access the information. The original format of this data is ArcGIS coverage format. The user must have a ESRI compatible software to read and process the data file. In lieu of an ESRI software, the user may utilize another GIS application package capable of importing the data.

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Who wrote the metadata?

Dates:
Last modified: 20111208

Metadata author:
Mary DiGiacomo-Cohen
Long Island Sound Resource Center, a partnership between the State of Connecticut, Department of Environmental Protection and the University of Connecticut
Long Island Sound Resource Center, UConn Avery Point, 1080 Shennecossett Rd
Groton, Connecticut 06340
USA

(860) 405-9015 (voice)
lisrc@uconn.edu
Hours of Service: Monday to Friday, 08:30 to 16:30 Eastern Standard Time

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata(FGDC-STD-001-1998)

Metadata extensions used:
  • http://www.esri.com/metadata/esriprof80.html

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