cob_attitude - strikes and dips of beds cob_beds - beds traceable in outcrop or on air photos cob_compgeo - geology polygons cob_contacts - geologic contacts cob_faults - fault traces cob_folds - fold axial planes cob_inferred - inferred geologic contacts cob_kc - point locations of coquinoid limestone cob_samples - sample locations (used only on appendix map)
Mull, C.G., Harris, E.E., Delaney, P.R., and Swenson, R.F., 2009, Geologic map of the Cobblestone Creek - May Creek area, east-central foothills, Brooks Range, Alaska: Preliminary Interpretive Report PIR 2009-5, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys, Fairbanks, Alaska - USA.
Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest 0.000064
Ordinates (y-coordinates) are specified to the nearest 0.000064
Planar coordinates are specified in meters
The horizontal datum used is D_Clarke_1866.
The ellipsoid used is Clarke 1866.
The semi-major axis of the ellipsoid used is 6378206.4.
The flattening of the ellipsoid used is 1/294.978698.
|Codeset Source:||Alaska Division of Geological & Geophysical Surveys <http://www.dggs.dnr.state.ak.us/metadata/PIR2009-5_codeset.pdf>|
|alloc_con||allochthon boundary, concealed|
|alloc_con?||allochthon boundary, concealed and queried|
|alloch||allochthon boundary thrust|
|alloch?||allochthon boundary thrust, queried|
|alloch_con||allochthon boundary thrust, concealed|
|left_con?||left-lateral fault, concealed, queried|
|thrust?apx||thrust fault, approximately located, queried|
|thrust?con||thrust fault, concealed, queried|
|thrust_apx||thrust fault, approximately located|
|thrust_con||thrust fault, concealed|
|transverse||trace of a transverse fault, relative motion unknown|
|anti||axial trace of anticline|
|arrow||arrow symbol to show plunge|
|concealed||trace of fault, concealed; relative motion unknown|
|AFT||Apatite fission track sample|
|micro_chem||sample for micropaleontology and geochem|
00XXYY; 00=year, XX=Geologist's initials, YY= unique sample identifier.
|Range of values|
|Range of values|
|Range of values|
|Range of values|
|appxbed||approximate bedding surface|
|appxotbed||approximate overturned bedding surface|
|horizontal||horizontal bedding surface|
|vertical||vertical bedding surface - approximated|
|vert||vertical bedding - certain|
This Geologic Map was fundedby DGGS Energy Section. Geologic field investigations by: C.G. Mull (1982, 1985, 1986, 1987, 1989, 1990, 1991, 1992, 1993, 1999, 2000, 2001); E.E. Harris (1985, 1999, 2000, 2001); Paige R. Peapples (2001); D.L. LePain, R.A. Kirkham, and R.R. Reifenstuhl (1999, 2000, 2001); Jerry Siok (1983, 1985); D.A. Bodnar (1983); K.E. Adams and M.L. Buckingham (1985); D.W. Houseknecht, C.J. Schenk, and T.J. Ryherd (2001); M.D. Myers (1989, 1999); M.T. Whalen and M.B. Mickey (2000).Digital cartography by Paige R. Delaney.
(907) 451-5029 (voice)
(907) 451-5050 (FAX)
Local field studies by the Alaska Division of Geological & Geophysical Surveys (DGGS) began in the area in 1982 and continued intermittently in conjunction with other field studies. In recent years, interest in hydrocarbon exploration in the Brooks Range foothills has increased considerably, resulting in an opportunity to compile previous studies as well as to carry out additional field studies to address specific structural and stratigraphic problems. In addition, ongoing mapping and structural and stratigraphic studies in the Siksikpuk River - Tiglukpuk Creek area to the west (Peapples and others, 2007) have resulted in some revised structural and stratigraphic concepts that have proven to be applicable to the Cobblestone Creek-May Creek map area and the adjacent Kanayut River map area to the west (Harris and others, in press).
Patton, W.W., Jr., and Tailleur, I.L., 1964, Geology of the Killik - Itkillik region, Alaska: Professional Paper P 0303-G, United States Geological Survey, Reston, VA.
Pessel, G.H., and Mull, C.G., 1964, Geologic Map of the Chandler Lake quadrangle.
Sonneman, H.S., and Mull, C.G., 1972, Geologic map of the Chandler Lake Quadrangle.
Data sources used in this process:
Geologic point, line, and polygon data were determined visually using color infrared aerial photographs at a scale of approximately 1:63,360 and topographic maps at scales of 1:63,360 and larger. Feature attributes were checked by the geologists who conducted the field observations. To check attribute accuracy, a check plot was visually compared to the geologist's original compilation. Discrepancies between the digital geospatial dataset and the original analog or digital compilation were corrected as needed. The geologic interpretations presented in this report have undergone two technical reviews by geologists familiar with the subject of the report or geology of the map area. Reviewers' suggestions were incorporated into the final draft when deemed appropriate by the author.
Locations were determined in the field using raster images of topographic base maps and Garmin GPS units. The estimated positional error caluclated by the GPS unit was not recorded. Bedrock geologic map data also have a horizontal positional accuracy dependent on the "on-screen" method of digital cartography. Map error is induced by: (1) transferring map data from base topography to a Mylar compilation map, with an estimated potential error due to a pen line width of approximately 0.001 inches being equivalent to approximately 1.5 meters on the ground; (2) the digitizing RMS error (30 control points on a regular grid have an average RMS error of 14.0 meters on the ground; individual control point error ranges from 2.9 to 24.0 meters on the ground); and (3) the accuracy of the human operator digitizing the geologic line work from the topographic base map, with an estimated error due to a pen line width of approximately 0.001 inches being equivalent to approximately 1.5 meters on the ground. The average potential horizontal error for bedrock geologic map features is estimated to be approximately 15 meters.
This dataset includes geospatial information about beds traceable on air photos and/or in the field. The dataset displays: geologic units and contacts; inferred geologic contacts; fold and fault traces; strike, dip, and fold axis attitude; point locations of coquinoid limestone; manmade infrastructure such as airstrips, roads, etc.; sample locations; point elevations digitized from the raster map; and wells.
Polygon topology is present and clean on the originating geospatial dataset. All polygon features were were topologically validated using the ESRI ArcGIS 9.0 software prior to export to shape file format. The logical consistency of the point and line files has been visually checked but not systematically verified.
Are there legal restrictions on access or use of the data?
- This report, map, and/or dataset are available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).
- Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. User specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys.
Preliminary Interpretive Report 2009-5
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|Data format:||PDF (version 1.6)|
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