control-points Well locations and interpreted depth to top Mesozoic unconformity in oil and gas wells. This table is provided as Table 1 on the printed map and in the csv file "control-points.csv" contours Lines of equal elevation (shapefile) faults Polyline representing the location of a displacement of rocks along a planar surface (shapefile) folds Polyline indicating the location of an anticlinal or synclinal fold axis (shapefile)
Shellenbaum, D.P., Gregersen, L.J., and Delaney, P.R., 2010, Top Mesozoic unconformity depth map of the Cook Inlet Basin, Alaska: Report of Investigations RI 2010-2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska.Online Links:
Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest 0.000001
Ordinates (y-coordinates) are specified to the nearest 0.000001
Planar coordinates are specified in meters
The horizontal datum used is North American Datum of 1983.
The ellipsoid used is Clarke 1866.
The semi-major axis of the ellipsoid used is 6378137.
The flattening of the ellipsoid used is 1/298.25722210088.
| Range of values | |
|---|---|
| Minimum: | 0 |
| Maximum: | -25000 |
| Units: | feet |
| Value | Definition |
|---|---|
| int_dash | intermediate_dashed; refers to approximately located intermediate contour |
| int | intermediate contour |
| index_dash | approximately located index contour |
| index | index contour |
| Value | Definition |
|---|---|
| normal_seis | normal fault derived from seismic interpretation |
| strike_slip | strike-slip fault |
| strike_slip_dash | approximately located strike-slip fault |
| thrust | thrust fault |
| thrust_dash | approximately located thrust fault |
| thrust_seis | thrust fault derived from seismic interpretation |
| Value | Definition |
|---|---|
| acl | anticline |
| acl_dash | approximately located anticline |
| scl | syncline |
| scl_dash | approximately located syncline |
| Range of values | |
|---|---|
| Minimum: | 1 |
| Maximum: | 101 |
Alaska Oil and Gas Conservation Commission (AOGCC) catalog index number
| Range of values | |
|---|---|
| Minimum: | 670 |
| Maximum: | 16650 |
| Units: | feet |
| Range of values | |
|---|---|
| Minimum: | -591 |
| Maximum: | -16221 |
| Units: | feet |
The purpose of the map is to provide an interpretation of the Cook Inlet basin Base Tertiary depth structure to the public. While most oil and gas exploration companies active in the Cook Inlet Basin have proprietary databases of seismic and well data with which they have created proprietary depth surface maps, a detailed map incorporating a significant amount of seismic data has not been available in the public domain, and to new companies who may be interested in exploring in the basin.This map incorporates seismic data over most of the marine portion overlying the basin.Additionally, this map will be used in a subsequent map of the Mesozoic subcrop surfaces, where Cretaceous and Jurassic subcrops will be displayed on the Base Tertiary depth surface.
Zippi, P.A., 2006, Greater Cook Inlet stratigraphic palynology control database and study.Online Links:
- www.biostratigraphy.com
Alaska Oil & Gas Conservation Commission (AOGCC), 2010, Annual Report and public well databases: Annual Report and public well databases 2010.Online Links:
Alaska Division of Oil & Gas, 2010, Alaska Oil and Gas Report 2009: Alaska Division of Oil & Gas, Anchorage, Alaska.Online Links:
Canadian Stratigraphic Services Lithologic Logs, 2010, USA Well Log Index.Online Links:
- www.canstrat.com
Magoon, L.B, Adkison, W.L, and Egbert, R.M., 1976, Map showing geology, wildcat wells, Tertiary plant-fossil localities, K-Ar age dates and petroleum operations, Cook Inletarea, Alaska: USGS Miscellaneous Investigation Map I-1019.
Wilson, F.H., Hults, C.P., Schmoll, H.R., Haeussler, P.J., Schmidt, J.M., Yahle, L.A., and Labay, K.A., 2009, Preliminary Geologic Map of the Cook Inlet Region, Alaska: USGS Open File Report OF 2009-1108.
CGGVeritas, 2010, 2010, CGGVeritas CI88 and CI89 marine 2D seismic speculative data.Online Links:
- www.cggveritas.com
Staff, DNR, Unpublished material, State of Alaska, Department of Natural Resources, Alaska Statewide Core GIS database.
Data sources used in this process:
Data sources used in this process:
Data sources used in this process:
Data sources used in this process:
Contours outside of the CI88 and CI89 two-dimensional seismic coverage are dashed to indicate uncertainty. Contours outside seismic coverage with little well control have even higher uncertainties, and are designated with question marks.The absolute depth error at any given point on the map is difficult to quantify and results from uncertainties in a) the depth pick in wells, b) interpolation between and extrapolation away from wells, c) time picks on seismic, d)variations in the seismic velocity field, and e) gridding, contouring, and smoothing artifacts, particularly in areas of sparse seismic and well control. There is also a certain amount of spatial uncertainty regarding the intersection of the top Mesozoic unconformity horizon with the Bruin Bay and Castle Mountain - Lake Clark fault systems that bound the basin to the west. The fault traces (Magoon and others, 1976) indicate surface expression, whereas the Base Tertiary surface lies at varying depths. The unconformity depth surface has been contoured as if the faults are single vertical entities, but the reality is certain to be more structurally complex.The magnitude of this spatial uncertainty depends on the dips and complexity of the faults as well as the depth of the Base Tertiary surface.The deeper the surface and the shallower the actual fault dips, the larger the potential error. This report has received two technical reviews by scientists familiar with the subject matter as well as technical editing.
Horizontal positional accuracy of entities outside of the two-dimensional seismic coverage area and where there is little well control is difficult to quantify.Error at any given point results from uncertainties in a) the depth pick in wells, b) interpolation between and extrapolation away from wells, c) time picks on seismic, d)variations in the seismic velocity field, and e) gridding, contouring, and smoothing artifacts, particularly in areas of sparse seismic and well control.
The location accuracy of interpreted depths displayed by the depth contours and presented in the "contours file" is discussed in Horizontal Positional Accuracy Report. The depth to the top Mesozoic unconformity for each well is presented in table 1 (Depth to top Mesozoic unconformity in oil and gas wells) and was interpreted using borehole geophysical log character, lithologic logs, and palynology data. The accuracy of our interpreted depths varies according the quality and density of the available data. Additional detail regarding the accuracy of our interpretations at each specific hole is not available.
The map was constructed primarily from marine seismic reflection data and oil and gas wells that penetrated the top Mesozoic unconformity.Where the well control is too dense to differentiate at the 1:500,000 scale, an inset map is provided. Previous mapping and well penetrations were used to interpret the top Mesozoic unconformity depth surface where seismic was not available.The data set displays contours as well as fault and fold traces.This dataset does not include locations of oil and gas wells or seismic lines used to interpret the top Mesozoic unconformity.
The digitized lines representing faults, folds, and contours in this dataset were checked visually for duplication using ESRI ArcMap software.
Are there legal restrictions on access or use of the data?
- Access_Constraints:
- 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).
- Use_Constraints:
- 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.
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| Data format: | SHP and CSV |
|---|---|
| Network links: |
<http://dx.doi.org/10.14509/21961> |
| Data format: | |
|---|---|
| Network links: |
<http://dx.doi.org/10.14509/21961> |
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