U.S. Geological Survey 2000 Version 2.0, Updated Feb, 2015 vector digital data Ground Water Atlas of the United States USGS HA-730 Reston, VA U.S. Geological Survey https://water.usgs.gov/lookup/getspatial?silurian-devonian_aquifers U.S. Geological Survey 1996 Hydrologic Atlas USGS HA-730-K Reston, VA U.S. Geological Survey https://pubs.usgs.gov/ha/ha730/ch_k/K-text1.html#silurian This data set represents the extent of the Silurian Devonian aquifers in the states of Michigan, Wisconsin, Illinois, Indiana, Ohio, Kentucky, and Tennessee. These data delineate the areal extent of the Silurian Devonian aquifers as defined in the 'Ground Water Atlas of the United States' (U.S. Geological Survey HA 730). The scale of source material is 1:2,500,000 and these data are not intended for use at a larger scale. The juxtaposition of regionally mapped aquifers has led to some instances where an aquifer outcrop or shallow subcrop is bounded by a State line. This is a result of the regional mapping and national categorization methods used and is not meant to imply a hydrogeologic change coincident with a State boundary. Comments regarding the names of aquifers or the hydrogeologic interpretation of the aquifers can be directed to the U.S. Geological Survey, Water Mission Area, Office of Ground Water. The nationwide principal aquifers map, cited as a complete or partial source, refers to both a dataset published at 1:2,500,000 and a derived map printed at 1:5,000,000. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in ARC/INFO format, this metadata file may include some ARC/INFO-specific terminology. 1992 publication date complete As needed -96.397816 -81.580344 45.953080 35.324817 USGS Thesaurus aquifer aquifer extent groundwater ISO 19115 Topic Category geoscientificInformation inlandWaters environment USGS Metadata Identifier USGS:9bc8ac55-0d7e-46c3-a464-2b8e1d098bf0 Geographic Names Information System Northern Illinois Western Illinois Michigan Illinois Indiana Central Ohio Central Lowland Province None. Acknowledgement of the U.S. Geological Survey would be appreciated in products derived from these data. These data are not to be used at scales greater than 1:2,500,000. Selection of the aquifer polygon may also result in selection of non-aquifer polygons (AQ_CODE=999) within the aquifer extent. U.S. Geological Survey Water Webserver Team mailing address

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Reston VA 20192 USA 1-888-275-8747 h2oteam@usgs.gov Please use email. https://water.usgs.gov/GIS/browse/k039.gif Image of the silurian-devonian aquifer jpg Windows NT Version 4.0 (Build 1381) Service Pack 6; ESRI ArcInfo 8.1.0.415 U.S. Geological Survey 1999 map National Atlas of the Unites States of America National Atlas product Reston, VA U.S. Geological Survey https://water.usgs.gov/GIS/dsdl/USAaquiferMAP11_17.pdf U.S. Geological Survey 1989 map Hydrologic Investigations Atlas HA 730 Reston, VA U.S. Geological Survey https://pubs.usgs.gov/ha/ha730/index.html Source data was checked using standard USGS review procedures. Attributes were checked by plotting the coverage and reselecting for the different values. Polygon and chain-=node topology present. Every polygon has a label. This was checked using the labelerror command and the idedit command. The extent is based on the best available printed sources on the subject of aquifer extents. There is the potential that better data is available at the local level. All digitized lines when plotted at 0.05" were within the lineweight of the compilation source. U.S. Geological Survey 1992 map Hydrologic Atlas HA 730 - J, Fig. 73 Reston, VA U.S. Geological Survey https://pubs.usgs.gov/ha/ha730/ 7500000 mylar separates 1996 currentness text U.S. Geological Survey, 1998 Source provided location of aquifer extent line U.S. Geological Survey 1998 data National Atlas of the United States of America National Atlas product Reston, VA U.S. Geological Survey 2500000 digital file 1998 as published U.S. Geological Survey, 1998 Source provided location of aquifer extent line U.S. Geological Survey 1995 map Hydrologic Atlas HA 730-K, fig 39 Reston, VA U.S. Geological Survey 5000000 mylar separates 1992 currentness text U.S. Geological Survey, 1998 Source provided location of aquifer extent line U.S. Geological Survey 1999 map Reston, VA U.S. Geological Survey 2000000 digital file 1995 1999 ground condition U.S. Geological Survey, 1998 boundary used to delineate coastal extent of aquifer a.) Aquifer names and all or part of the outcrop line shown on the Nationwide 'Principal Aquifer' map (Miller, James A., 1998), were used with the extent of each aquifer from the various chapters of the 'Ground Water Atlas of the United States' to create this coverage. The largest scale map source available was used. Where the line defining the aquifer extent is the same as the outcrop, the data were copied from the Principal Aquifers data set. Otherwise data were traced from 1:7,500,000, 1:5,000,000, or 1:2,500,000 scale map sources onto a stable base material. Where the extent was defined by a coastline, the 1:2,000,000-scale Hydrography Features of the U.S. was used. (The following steps were done using ARC/INFO 7.2.1 on Data General AViiON UNIX. Much of the terminology used will be specific to ARC/INFO). b.) The aquifer extent lines were digitized into ARCEDIT using standard USGStolerances. After digitizing, a check plot was created and reviewed against the traced map. If a line was located more than a line weight (0.05") from the digitized source, it was corrected during an ARCEDIT session. c.) Using the TRANSFORM command, the coverage containing the digitized, aquifer extent lines was combined with the coverage containing registration tics, was rubbersheeted from geographic to Albers Equal-Area Conic projection. An RMS error of less than 0.004 was accepted. If it was greater than 0.004 the location and values of the lat/long points were verified. Following this transformation, any aquifer lines from the aquifer extent coverage coincidental to aquifer lines from the 'Principal Aquifers' map data set were copied from the 'Principal Aquifers' map data set and put into the aquifer extent coverage. The aquifer extent coverage was cleaned, the topology was built, and labels were added. d.) Four items were added to the .PAT file: AQ_NAME (60 65 C) AQ_CODE (4 5 I), ROCK_NAME (40 45 C), ROCK_TYPE (4 5 I). ROCK_NAME comes from the Principal Aquifers Data set, 1998. The first digit of the three digit aq_code, refers to aquifer lithology. 100 series are numbers for unconsolidated sand and gravel aquifers 200 series are numbers for semiconsolidated sand aquifers 300 series are numbers for sandstone aquifers 400 series are numbers for carbonate-rock aquifers 500 series are numbers for sandstone and carbonate-rock aquifers 600 series are numbers for volcanic-rock aquifers 999 is given for non aquifer islands inside aquifer polygons e.) The following items were verified: --Digitizing RMS error (below 0.005) --Transformation RMS error (below 0.004) --Arcs match the traced mylar (no gaps between the plot and the compilation) --Arc and polygon topology exists --Coverage has a coordinate system defined --Attributes aq_name and aq_code have been added and populated correctly --Necessary files exist to redo any step 19970331 This step was done on an NT workstation. After plotting the extent at 1:2,000,000, the lines were checked with the documented sources. If needed, the lines were corrected to better represent the source data. This process may have included one or more of the following steps: --Reshaping the arc --Replacing the arc from the outcrop data, --Digitizing new lines polygons --Deleting polygons. 19991118 Due to a computer problem final corrected files were lost, however hard copy plots of those files were retained. This file was recreated from those plots using a similar process to that described above. Where extent lines were equal to the outcrop, data were extracted from the Principal Aquifers Data Set. Otherwise data were digitized from the retained hard copy plots using the same tolerances and software described above. A check plot was created and compared to the hard copy plot. Significant deviations, greater than approximately a line weight (0.005"), were corrected using ARCEDIT. Data were reviewed internally to assure compliance with original sources. 20000712 First draft of metadata created by J.M. Watermolen using FGDCMETA.AML ver.1.32 01/11/99 on ARC/INFO data set. 19991118 Documentation edited by S.M. Last, based on informal reviews. 20000107 Documentation updated by J.J. Skalet based on internal reviews. 20010504 Documentation, new data formats and metadata were checked and updated by Michael Ierardi 20140202 Vector Complete chain 120 Entity point 55 GT-polygon composed of chains 50 Point 2993 Albers Conical Equal Area 29.500000 45.500000 -96.000000 23.00000 0.000000 0.000000 coordinate pair 0.002048 0.002048 meters North American Datum of 1983 Geodetic Reference System 80 6378137.000000 298.257222 SILURIAN_EXT.AAT Line attributes U.S. Geological Survey LNTYPE The line category U.S. Geological Survey 1 coastline or international boundary U.S. Geological Survey 2 interior aquifer contact line U.S. Geological Survey SILURIAN_EXT.PAT Polygon attributes U.S. Geological Survey ROCK_NAME General lithology of the rocks that make up the aquifer Principal Aquifers Data set, 1998 Carbonate-rock aquifers Delineation of silurian-devonian aquifer Principal Aquifers Data set, 1998 ROCK_TYPE Code for rock name Principal Aquifers Data set, 1998 400 Carbonate-rock aquifers Principal Aquifers Data set, 1998 AQ_NAME Name of the aquifer Principal Aquifers Data set, 1998 Silurian-Devonian aquifers Delineation of aquifer boundary Principal Aquifers Data set, 1998 AQ_CODE Numeric code for a particular aquifer Derived to help manage the data when numerous aquifers are aggregated 410 Silurian-Devonian aquifers Principal Aquifers Data set, 1998 999 Code for aquifer absent Principal Aquifers Data set, 1998 The original aquifer data was compiled in arc/info coverage format. This data has been updated to GIS shape and Geo Data Base format for increased useability. 1.) Principal Aquifers of the 48 Conterminous United States, Hawaii, Puerto Rico, and the U.S. Virgin Islands available at https://water.usgs.gov/lookup/getspatial?aquifers_us 2.) Ground Water Atlas of the United States Hydrologic Investigations Atlas HA 730 available at https://pubs.usgs.gov/ha/ha730/ U.S. Geological Survey Michael Ierardi IT Specialist mailing and physical address

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Reston VA 20192 USA 1-888-275-8747 (1-888-ASK-USGS) mierardi@usgs.gov Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data. The act of distribution shall not constitue any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials. Shape Online accessible data WinZip compressed file 0.11 https://water.usgs.gov/GIS/dsdl/Silurian-Devonian_aquifers_shp.zip GeoDataBase Online accessible data WinZip compressed file 0.28 https://water.usgs.gov/GIS/dsdl/Silurian-Devonian_aquifers_gdb.zip ARC export Online accessible data WinZip compressed file 0.41 https://water.usgs.gov/GIS/dsdl/silurian.zip None. This dataset is provided by USGS as a public service. 20201117 U.S. Geological Survey Ask USGS -- Water Webserver Team mailing

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Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) mierardi@usgs.gov FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998