Reconnaissance geologic map of the Duncan Canal/Zarembo Island area, southeastern Alaska

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Frequently-anticipated questions:

What does this data set describe?

    Reconnaissance geologic map of the Duncan Canal/Zarembo Island area, southeastern Alaska
    USGS OFR 99-168 is an update of bedrock geologic mapping of the Duncan Canal/Zarembo Island area in southeast Alaska. This new mapping incorporates recent a recent airborne geophysical survey, new field work, fossils, radiometric ages, and geochemical signatures.

  1. How should this data set be cited?

    Karl, Susan M. , Haeussler, Peter J. , and McCafferty, Anne E. , 1999, Reconnaissance geologic map of the Duncan Canal/Zarembo Island area, southeastern Alaska: U.S. Geological Survey Open-File Report OFR 99-168.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -134.0
    East_Bounding_Coordinate: -131.6
    North_Bounding_Coordinate: 57.2
    South_Bounding_Coordinate: 56.0

  3. What does it look like?

    of99-168-map.pdf (PDF)
    Adobe PDF file showing the map sheet from OFR99-168 shows the geologic map with fossil locations, cross-sections, correlation of geologic units, and a brief description of the geologic units.

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

    Calendar_Date: 1999
    Currentness_Reference: publication date

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

    Geospatial_Data_Presentation_Form: map

  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.

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

      Grid_Coordinate_System_Name: Universal Transverse Mercator
      UTM_Zone_Number: 8
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -135.0
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 0.0
      False_Northing: 0.0

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 150
      Ordinates (y-coordinates) are specified to the nearest 150
      Planar coordinates are specified in meters

  7. How does the data set describe geographic features?

    Characteristic of arcs in dzgeol.aat, the arc attribute table, of the geology coverage (Source: USGS OFR 99-168)

    ARC-CODE is a positive integer value (3 3 I) item in the arc attribute table. Values range from 1-99. ARC-CODE identifies the type of geologic contact or other line feature. A description of the arc-code is given in the item LINE-TYPE. Look-up table, dzgeol.lut2, also contains this information. (Source: USGS OFR 99-168)

    1Stratigraphic contact, certain location
    2Stratigraphic contact, approximate location
    7Shoreline or riverbank
    9Boundary of altered zone or hornfels
    10Thrust fault, certain location; teeth on right from origin
    11Thrust fault, location approximate; teeth on right from origin
    15Ice contact
    30Fault, sense of displacement uncertain, location certain
    31Fault, sense of displacement uncertain, location approximate
    50Dikes and sills
    51Concealed contact
    52Concealed fault
    53Concealed thrust fault
    55Concealed normal fault, having right lateral oblique slip
    56Concealed normal fault, having left lateral oblique slip
    71Normal fault, having right lateral oblique slip, location certain
    72Normal fault, having right lateral oblique slip, location approximate
    73Normal fault, having left lateral oblique slip, location certain
    74Normal fault, having left lateral oblique slip, location approximate
    88Right lateral fault, location approximate
    98latitude and longitude marks used for cartography
    99Bounding line of coverage

    Characteristic of the polygon features in dzgeol are coded in the dzgeol.pat, the polygon attribute table. The .pat contains the following items: CLASS (4 5 B), UNIT (geologic unit label), DESC (brief description of geologic unit) (Source: USGS OFR 99-168)

    Class is a positive integer value (4 5 B) item in the polygon attribute table. Values range from 2-10059. A lookup table, dzgeol.lut, contains CLASS, LABEL, and DESC (a brief descripton of the geologic unit). See USGS OFR 99-168 for full description of the geologic units. (Source: USGS OFR 99-168)

    2Qs - Surficial deposits (Quaternary)
    3Qb - Basalt (Quaternary)
    4QTv - Vent breccia (Quaternary and Tertiary)
    5QTa - Andesite (Quaternary and Tertiary)
    6QTc - Volcaniclastic deposits (Quaternary and Tertiary)
    7QTr - Rhyolite (Quaternary and Tertiary)
    8QTb - Basalt (Quaternary and Tertiary)
    9QTd - Dikes, sills, and intrusive rocks (Quaternary and Tertiary)
    11Tmae - Alkali granite (Tertiary)
    12Tmge - Granite (Tertiary)
    13Tmme - Migmatite (Tertiary)
    14Tmaz - Alkali granite (Tertiary)
    15Tmgk - Granitic rocks (Tertiary)
    16Tmdk - Diorite (Tertiary)
    19Tk - Kootznahoo Formation (Tertiary)
    20Kwqo - Quartz monzodiorite (Cretaceous)
    24Kbdu - Dunite (Cretaceous)
    25Kbwh - Wherlite (Cretaceous)
    26Kbgb - Gabbro (Cretaceous)
    30TRhl - Hyd Group limestone (Triassic)
    31TRhb - Hyd Group breccia (Triassic)
    32Pp - Pybus Formation (Permian)
    33PCsy - Syenite (Permian to Pennsylvanian)
    36Sch - Heceta Limestone (Lower to Upper Silurian)
    37Schc - Polymictic conglomerate of the Heceta Limestone (Lower to Upper Silurian)
    38Scp - Polymictic conglomerate (Silurian)
    39Stbg - Bay of Pillars Formation graywacke turbidites (Silurian)
    40Stbc - Bay of Pillars Formation polymictic conglomerate (Silurian)
    41Stbo - Bay of Pillars Formation olistostrome deposits (Silurian)
    42Stpg - Bay of Pillars Formation graywacke (Lower to Upper Silurian)
    43Stpc - Bay of Pillars Formation conglomerate (Silurian)
    44SOdg - Descon Formation graywacke (Lower Ordovician to Lower Silurian)
    45SOdl - Descon Formation limestone (Lower Ordovician to Upper Silurian)
    49KJsg - Seymour Canal Formation greenstone (Cretaceous and Jurassic)
    50Ktif - Tonalite (Cretaceous)
    51Ktop - Tonalite porphyry (Cretaceous)
    52Ktoc - Tonalite porphyry (Cretaceous)
    53Kqop - Quartz monzodiorite (Cretaceous)
    54Kqo - Quartz monzodiorite (Cretaceous)
    55Kdi - Diorite (Cretaceous)
    56Kuk - Ultramafic complex (Cretaceous)
    57Khb - Hornblendite (Cretaceous)
    58KJsv - Seymour Canal Formation volcanic rocks (Cretaceous and Jurassic)
    59KJss - Seymour Canal Formation (Cretaceous and Jurassic)
    67Mzg - Gabbro (Mesozoic)
    70TRhv - Hyd Group volcanic rocks (Triassic)
    71Dls - Fossiliferous limestone (Lower and Middle Devonian)
    72Tdr - Rhyolite (Tertiary)
    74Tag - Alaskite granite (Tertiary)
    75Tlgm - Leucocratic granodioritic migmatite (Tertiary)
    76Tgdp - Porphyritic granodiorite (Tertiary)
    77Tgrg - Gneissic granite and granodiorite (Tertiary)
    78Tgdb - Granodiorite and quartz diorite (Tertiary)
    80Tlg - Leucocratic granite and granodiorite (Tertiary)
    81Tgd - Granodiorite (Tertiary)
    82Ttom - Tonalite migmatite (Tertiary)
    83Tto - Tonalite (Tertiary)
    84Tgdg - Gneissic granodiorite (Tertiary)
    85MzPzp - Phyllite (Mesozoic and Paleozoic)
    86MzPzbs - Biotite schist (Mesozoic and Paleozoic)
    87MzPzsc - Schistose conglomerate (Mesozoic and Paleozoic)
    88MzPzhs - Hornblende schist (Mesozoic and Paleozoic)
    89MzPzm - Marble (Mesozoic and Paleozoic)
    90MzPzbg - Biotite gneiss (Mesozoic and Paleozoic)
    91MzPzhg - Hornblende gneiss (Mesozoic and Paleozoic)
    92MzPzgn - Gneiss (Mesozoic and Paleozoic)
    93Kmgf - Granodioritic migmatite (Cretaceous)
    94Ktef - Tonalite (Cretaceous)
    95Ktob - Tonalite (Cretaceous)
    96Kgb - Gabbro (Cretaceous)
    106TRhsv - Hyd Group sedimentary and volcanic rocks (Triassic)
    107PMc - Cannery Formation (Permian and Mississippian)
    109Dsv - Metasedimentary and metavolcanic rocks (Devonian)
    110Tqdz - Quartz diorite (Tertiary)
    111Qls - Landslide deposits (Quaternary)
    113TRha - Hyd Group argillite (Triassic)
    114TRh - Hyd Group (Triassic)
    115Tgbk - Gabbro (Tertiary)
    116TRh? - Hyd Group? (Triassic)
    117PzpCm - Metamorphic rocks (Paleozoic and Precambrian)
    119Ki - Intrusive rocks (Cretaceous)
    121Mzi - Intrusive rocks (Mesozoic)
    123Qb? - Basalt? (Quaternary)
    127Ti - Intermediate intrusive rocks (Tertiary)
    131MzPzsv - Metasedimentary and metavolcanic rocks (Mesozoic and Paleozoic)
    134Tmqe - Quartz diorite and diorite (Tertiary)
    137KJsm - Stephens Passage Group sedimentary rocks of Marsh Island (Cretaceous)
    139Tgdm - Gneissic granodioritic migmatite (Tertiary)
    10038Scp - hornfels Scp
    10039Stbg - hornfels Stbg
    10042Stpg - hornfels Stpg
    10043Stpc - hornfels Stpc
    1044SOdg - hornfels SOdg
    10059KJss - hornfels KJss

    Fossil locality and data are stored in dzfossil.pat. Items include MAP (map number), SAMPLE (sample id), AGE (stratigraphic age range), FOSSIL1-9 (fossil id), CAI_MIN and CAI_MAX (color alteration index minimum and maximum), SCIENTIST (identifier), SOURCE (reference), and USGS (USGS Collection id) (Source: USGS OFR 99-168)

    Point coverage dzstruct contains measurments of strike and dip of bedding and foliations. Items include: LAT and LONG (latitude and longitude in decimal degrees), ANGLE (strike), DIP (angle of dip), STATION (station id), and TYPE (numeric code for type of measurement) (Source: OFR 99-168)

    TYPE is a positive integer value item in the point attribute table. TYPE describes the what the measurement is of. (Source: OFR 99-168)

    20strike and dip of bedding
    49strike of bedding, upright
    50strike of dip of bedding, overturned
    51strike and dip of foliation in intrusive rocks
    52strike and dip of foliation

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?

    Kelly Brunt, Raytheon STX contractor

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

    U.S. Geological Survey
    c/o Susan M. Karl
    4200 University Drive
    Anchorage, AK 99508-4667

    907-561-1181 (voice)

Why was the data set created?

The purpose of this geologic map is to identify and understand the sources of geophysical anomalies found during airborne geophysical survey in 1997. This area was selected for the geophysical survey because of its high mineral potential.

How was the data set created?

  1. Where did the data come from?

  2. What changes have been made?

    Date: 1999 (change 1 of 1)
    Linework was captured by hand digitizing from a stable base line drawing. The digital linework was edited and attributed using ARC/Info. The coverage was cleaned, built for polygon topology, and had labels created and attributed. For the purpose of distribution, the coverage has been converted to an interchange format file using the ARC/Info export command.

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

  1. How well have the observations been checked?

    The linework was captured by hand digitizing from 1:63,360 scale stable base maps. The coverage was edited and topology was built. The arcs and polygons were attributed. The linework was captured by hand digitizing from field compilations on stable base mylar at 1:63,360 scale. Vector and polygon attributes were obtained from field maps and compilations. The digital data has been visually checked and the geologic map has undergone technical review.

  2. How accurate are the geographic locations?

    Users of this digital geologic map should respect the intentions of the original mappers and map compilers, and the limitations of the map. The Duncan Canal/Zarembo Island area geologic map is intended to be used at a scale of 1:150,000; it is not intended to be used at a more detailed scale.

  3. How accurate are the heights or depths?

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

    These digital files are the geospatial files used to create the geologic map. Files for the correlation of map units and cross-sections are not included.

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

    The geology coverage, dzgeol, is a network coverage containing arcs and polygons. Each polygon has a coded attribute designating the mapped geologic unit. Faults and stratigraphic contacts are represented as arcs. When a fault is also a stratigraphic contact, only a single arc is present. Dangling arcs may be present (faults, dikes, etc.)

    Coverage dzfossil is a point data set showing the locations of fossil samples. The data set includes fossil identification, stratigraphic age, color alteratioin index, and name of the identifier.

    Coverage dzstruct is a point data set containing strike and dip information for bedding and foliation.

How can someone get a copy of the data set?

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

Access_Constraints: None
Use_Constraints: None

  1. Who distributes the data set? (Distributor 1 of 1)

    USGS Information Services
    Box 25286
    Denver Federal Center
    Denver, CO 80225-0046

    303-202-4200 or 1-888-ASK-USGS (voice)

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

    USGS OFR 99-168

  3. What legal disclaimers am I supposed to read?

    Although this data has been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data, software, or related materials.

  4. How can I download or order the data?

Who wrote the metadata?

Last modified: 21-Jun-2001

Metadata author:
U.S. Geological Survey
c/o Nora Shew
4200 University Drive
Anchorage, AK 99508-4667

907-786-7445 (voice)

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

Generated by mp version 2.4.30 on Thu Jun 21 13:44:16 2001