BEDROCK GEOLOGIC MAPPING OF THE MESABI IRON RANGE October 2005 Minnesota Geological Survey—University of Minnesota Project #523- 6141 Funded September 2, 2003 through September 30, 2005 The published bedrock geologic map is referenced as follows: Jirsa, M.A., Chandler, V.W., and Lively, R.S., 2005, Bedrock geology of the Mesabi Iron Range, Minnesota: Minnesota Geological Survey Miscellaneous Map M-163, scale 1:100,000. An image of the map is provided as a PDF document--M163.pdf All GIS shapefiles or coverages are NAD83, UTM Zone 15. Files below and pictures linked from the ArcView project are in the zip file m163.zip Index of GIS files: 1) Stations.shp=Station numbers that relate to bedrock-related observations, mine photos, and structural measurements. Associated table lists station number and a general mine name. 2) Bgoc.shp=Bedrock outcrops. Includes several outcrop databases from prior projects of the MGS, and new mine outcrops mapped for this project. Some overlap of outcrops occurs locally. 3) Bgpg.shp=Geologic units coded by age, formation, and rock type. 4) Bgln.shp=Faults and unit contact lines. 5) Struclns.shp=Diabasic dikes and fold axes. 6) Intslate.shp=Approximate position of intermediate slate unit of Biwabik Iron Formation. 7) Gemstr.shp=Bedrock structure showing attitude of bedding, joints, faults, slickensides and fold axes measured at specific stations. Associated table records azimuth and plunge of dip for all planar structures; plunge direction and degrees from horizontal for linear structures. SEE below for more details. 8) Seeps.shp=Location of seeps and flows into mines. This database is not the result of a thorough search for seeps, and instead represents seeps discovered in the process of reconnaissance field work. Associated table shows station number (where one was assigned) and source of seeps—either from fractures in rock (rk), layers in the overburden (ob) that may include glacial materials or waste-rock, or at the rock/overburden interface (rk/ob). The visually estimated height in feet above 2004 water levels is given. File also includes the location of surface flows that were observed. 9) Quatchannel.shp=Approximate locations of depressions on bedrock surface filled with glacial material. Typically shown as a line along portions of mine shorelines or pit outlines. Depressions are commonly, but not everywhere filled with varying amounts of sand and gravel. 10) Pitlakes.shp=Mine pit lakes modified locally from DNR Mine Lands Database using Farm Service Administration air photography. Most are abandoned and flooded natural ore mines. 11) Tacmines.shp=Approximate outline of taconite mining; modified locally from DNR Mine Lands Database using air photography. 12) Btlines.shp=Bedrock topographic contours at 20-foot intervals; modified from Jirsa and others, 2002; 2005—see map for references. 13) Msbmag_lp=(Folder: mag_grids) A georegistered image of total field magnetic anomaly data constructed from the original flight lines specifically for this project, and modified using low-pass filter. The image is part of the ArcView project; and also is included on this CD-ROM as an ESRI grid. 14) Msbmag_hplp=(Folder: mag_grids) Magnetic grid image created by processing original flight line data, then applying a high-pass filter over the low-pass-filtered data from Msbmag_lp to remove much of the effect of high frequency anomalies and accentuate subtle contrasts of magnetic signature. The image is part of the ArcView project; and also is included on this CD-ROM as an ESRI grid. 15) msb_fsa.img=THIS FILE NOT INCLUDED WITHIN THE ZIP BECAUSE OF THE LARGE SIZE. COUNTY IMAGES CAN BE OBTAINED FROM THE DNR DATA DELI. Clipped version of Farm Service Administration air photography. Imagine image format (Imagine extension is standard with ArcView). This image has been made smaller than the original county data files, but has not been clipped to the map area. It may take several minutes to be read from the CD. 16) Basemap datasets=Compiled and modified from 1990 TIGER/line digital files maintained by the U.S. Bureau of the Census. Subdivided into east and west halfs of the study area. East is in folder eastbase, West in folder westbase. 17) BRphoto.shp=(in folder BRHOTOS) Point locations that generally correspond to the camera position from which the photos were taken. Photographs are linked to the APR so that users can select a location using the “Hotlink” icon and view the image. Image resolution is generally quite low—if higher resolution is needed, please contact the authors. Photos can also be viewed directly with the ifanviewer provided, although there will be no link to location other than the folder name indicating the mine. Folders 1) Legends—folder containing ArcView legend files for shapefiles (.avl) 2) Export—folder containing ArcInfo file interchange datasets (e00) for the bedrock linework, bedrock polygons, dikes and the maparea. 3) Iview—folder containing the jpeg viewer used for the hotlinks in the ArcView project. 4) Metadata--metadataMSB.doc. Word file of metadata about the map project. Also in the folder are metadata about standard MGS formats. Mesabi.ppt--Powerpoint display that describes the project, explains the mapping methods and provides a summary interpretation of the results. m163bg.apr—the ArcView project file. For questions about the digital data contact Mark Jirsa (jirsa001@umn.edu) or Richard Lively (lively@umn.edu)