This digital data set consists of information about the surficial geology for the Dixie Mountain 7.5' quadrangle, Columbia, Multnomah and Washington Counties, Oregon, at 1:24,000-scale as part of the Oregon Department Geology and Mineral Industries (DOGAMI) earthquake reduction program. The layer contains 21 separate map units, some representing landforms, present on the surface in the quadrangle. This file is one in a set of four files which are provided to the user in two formats: MapInfo .tab and ESRI .shp format files. The other three files in the set include: Dixie_Mtn_Bedrock, Dixie_Mtn_Faults, and Dixie_Mtn_Folds. The map units include thick surficial deposits of loess, Missoula Flood sediments and colluvium mantle, and landslide deposits. Compiled from high resolution (1-2 m grid size) LiDAR (Light Detection and Ranging) bare-earth digital elevation allowing a truly revolutionary view of the geomorphology of the area.
To produce a general descriptive layer of surficial geology for the quadrangle and overlay map to go with the bedrock geology map. The purpose of the project is to improve geologic mapping in the Portland urban area in order to better understand earthquake hazards. In that context, the surficial map can be used to assist in new generation of earthquake hazards and to identify and locate geologic hazards, such as landslides.
The CD contains digital files with various map originally coverages created in MapInfo Professional version 9.1 (.tab) and a screen graphic of the map in Adobe PDF format. Digital map coverages are also provided as ArcView version 3.3 Shapefile (.shp) format for ESRI users. Accompanying the screen graphic of the map, is a text file (pdf format) describing the map units, a discussion of the quadrangle's structural history. This digital data is not field-checked and comes with no guarantees as to its accuracy.
Field work conducted in 2006 and 2007, data compliation-2008
There is uncertainty in the position of the surficial units from the field mapping process, the original map preparation, and the digitizing process. Therefore, DOGAMI makes no warranty as to the currency, completeness, accuracy or utility of any specific data. This disclaimer applies both to individual use of the data and aggregate use with other data. It is strongly recommended that careful attention be paid to the contents of the metadata file associated with these data. User should use caution when overlaying other data sets and should not make legally binding decisions from this data. Any person using the information presented here should fully understand the data collection and compilation process before beginning their analysis/use. The burden of determining fitness for use lies with the user. To avoid the risk of misinterpretation, invalid results, and erroneous conclusions, the users must consider original map scale, collection methodology, and any other conditions specific to every data element and each dataset as a whole. Potential users are advised to consult with DOGMAI to gain an understanding of the inherent limitations of this data set and its scope of inference. Also, the user must be aware that errors and conditions originating from physical sources involved in developing a dataset may be reflected in the data, and that the digital processing performed during preparation, storage, and transmission of the dataset may have exacerbated such errors and/or introduced additional ones.
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This research was supported by the U.S. Geological Survey (USGS), Department of the Interior, under USGS award number 03HQAG0013. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government. The Oregon Department of Geology and Mineral Industries created and maintains the spatial data sets. Credit should always be given to the data source and/or originator when the data is transferred or printed.
Surficial polygons units were delineated by the interpretation of LiDAR shaded relief, elevation color gradient, slope-shaded and slope color gradient grids and as vector contours at 1 m nominal (3 ft) intervals. Prior to release of map-on-demand files and metadata, the author was given final digital data sets and paper plots for checking against the source map(s) to verify the linework and attributes. Also, the author was asked to check the metadata and accompanying files for completeness and accuracy.
All polygons are fully attributed
All polygons are closed and each polygon has one unique label.
Horizontal accuracy of the images is approximately 20 centimeters.
Vertical accuracy of the images is approximately 20 centimeters.
The LiDAR data was visualized as shaded relief, elevation color gradient, slope-shaded and slope color gradient grids and as vector contours at 1 m nominal (3 ft) intervals--Digital Elevation Models (DEMs) derived from LiDAR data (<http://pugetsoundlidar.ess.washington.edu/>), and from which landslides, windblown deposits, and man-made features and other landforms were mapped.
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Polygons geologic features and data points were hand digitized, heads-up on the computer screen. The resultant coverages were attributed with data describing surficial geologic units. Each polygon was attributed with a 3 to 4 characters in "UNIT" field which contains the surficial geology unit designation.
Prior to release of map-on-demand files and metadata, the author was given final digital data sets and paper plots for checking against the source map(s) to verify the linework and attributes. Also, the author was asked to check the metadata and accompanying files for completeness and accuracy.
Internal feature number.
ESRI
Feature geometry.
ESRI
Unit identification code
Oregon Department of Geology and Mineral Industries
The attribute "UNIT" only contains the unit designation and labeled with the following code: Qal = Alluvium, Qt = Terrace deposits, QP, Pond deposits, Qmf = Missoula (Bretz) flood deposits, Ql = Primary loess, Qclb = Loess-basalt fragment colluvium, Qcm = Missoula flood silt colluvium, Qcls = Loess and sandstone colluvium, Qls1 = Surficial landslides, Qls2 = Surficial landslides, Qls3 = Surficial landslides, Rls = Surficial landslides, Qlb1 = Bedrock landslides, Qlb2 = Bedrock landslides, Pllb1 = Bedrock Landslides, Pllb2 = Bedrock landslides, Qf = flow and fan deposits, Qlww = Wildwood landslide complext, Plld = Dutch Canyon landslide complex, af = Artificial fill, b = Bedrock exposures
For complete decription of attributes, see O-08-07print.pdf
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No warranty, expressed or implied is made regarding the accuracy or utility of the data described and/or contained herein, nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data. It is strongly recommended that careful attention be paid to the contents of the metadata file associated with these data. The Oregon Department of Geology and Mineral Industries shall not be held liable for improper or incorrect use of these data. This information may be updated without notification.
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