Entry_ID: (required) Entry_Title: Preliminary Lithogeochemical Map Showing Near-Surface Rock Types in the Chesapeake Bay Watershed, Virginia and Maryland Group: Data_Set_Citation Originator(s): John D. Peper; Lucy B. McCartan; J. Wright Horton, Jr.; James E. Reddy Title: Preliminary Lithogeochemical Map Showing Near-Surface Rock Types in the Chesapeake Bay Watershed, Virginia and Maryland Publication: U.S. Geological Survey Open-File Report Publication_Date: 2001 Publication_Place: Reston, Virginia Publisher: U.S. Geological Survey Edition: 1.0 Data_Presentation_Form: Map URL: http://pubs.usgs.gov/openfile/of01-187/ End_Group Keyword: Virginia Keyword: Maryland Keyword: Chesapeake Keyword: Bay Keyword: Watershed Keyword: Lithogeochemical Keyword: Geologic Keyword: Geology Group: Temporal_Coverage Start_date: 1995 Stop_date: 2001 End_Group Data_Set_Progress: Complete Group: Spatial_Coverage Southernmost_Latitude: 36.50 Northernmost_Latitude: 39.75 Westernmost_Longitude: -80.75 Easternmost_Longitude: -75.00 End_Group Location: Virginia Location: Maryland Location: Chesapeake Location: Bay Location: Watershed Group: Data_Resolution Latitude_Resolution: 0.001 Longitude_Resolution: 0.001 End_Group Access_Constraints: None Use_Constraints: Although all data released in this report have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials and (or) the functioning of the software. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government Originating_Center: (required) Group: Data_Center Data_Center_Name: U.S. Geological Survey Dataset_ID: USGS Open-File Report 01-187 Group: Data_Center_Contact Last_name: U.S. Geological Survey First_name: N/A Email: whorton@usgs.gov Phone: 703-648-6933 Group: Address National Center, MS926A Reston, Virginia 20192 USA End_Group End_Group End_Group Group: Distribution Distribution_Media: online Distribution_Format : Arc/Info export-interchange Distribution_Size: 7.0 megabytes Fees: None End_Group Group: Multimedia_Sample URL: Format: GIF Group: Description Reduced-size image showing the general layout of map sheet. 864x597 pixels, 24-bit color. End_Group End_Group Group: Reference End_Group Group: Summary The purpose of this preliminary digital map is to provide a geographically referenced data base showing regional patterns in the distribution of rock types in the Virginia and Maryland parts of the Chesapeake Bay watershed. The map may be used to evaluate the hypothesis that lithology of rocks and sediments significantly influences the chemistry and quality of waters traveling over and through them on a regional scale. This preliminary experimental lithogeochemical map shows the distribution of rock types in the Virginia and Maryland parts of the Chesapeake Bay watershed. The map was produced digitally by classifying geologic-map units according to composition, mineralogy, and texture; rather than by age and stratigraphic relationships as shown on traditional geologic maps. This map differs from most lithologic maps in that the lithogeochemical unit classification distinguishes those rock units having key water-reactive minerals that may induce acid neutralization, or reduction, of hosted water at the weathering interface. The validity of these rock units, however, is independent of water chemistry, because the rock units are derived from geologic maps and rock descriptions. Areas of high soil carbon content, and sulfide metal deposits are also shown. Water-reactive minerals and their weathering reactions yield five lithogeochemical unit classes: 1) carbonate rock and calcareous rocks and sediments, the most acid-neutralizing; 2)carbonaceous-sulfidic rocks and sediments, oxygen-depleting and reducing; 3) quartzofeldspathic rocks and siliciclastic sediments, relatively weakly reactive with water; 4) mafic silicate rocks/sediments, oxygen consuming and high solute-load delivering; and, 5) the rarer calcareous-sulfidic (carbonaceous) rocks, neutralizing and reducing. Earlier studies in some parts of the map area have related solute loads in ground and stream waters to some aspects of bedrock lithology. More recent preliminary tests of relationships between four of the classes of mapped lithogeochemical units and ground water chemistry, in the Mid-Atlantic area using this map, have focused on and verified the nitrate-reducing and acid-neutralizing properties of some bedrock and unconsolidated aquifer rock types. Sulfide mineral deposits and their mine-tailings effects on waters are beginning to be studied by others. Additional testing of relationships among the lithogeochemical units and aspects of ground and surface water chemistry could help to refine the lithogeochemical classification, and this map. The testing could also improve the usefulness of the map for assessing aquifer reactivity and the transport properties of reactive contaminants such as acid rain, and nitrate from agricultural sources, in the Chesapeake Bay watershed. Data were originally collected in UTM coordinates, zone 18, NAD 1927, and projected to geographic coordinates (Lat/Long), NAD 1983. The data base is accompanied by a large format color map, a readme.txt file, and a explanatory PDF pamphlet. End_Group Group: Related_URL URL_Type: URL: http://www.mgs.md.gov/index.html Group: Description Originator: Cleaves and others Publication_Date: 1968 Title: Geologic Map of Maryland Online_Linkage: http://www.mgs.md.gov/index.html End_Group End_Group Group: Related_URL URL_Type: URL: http://www.mme.state.va.us/DMR/home.dmr.html Group: Description Originator: Virginia Division of Mineral Resources Publication_Date: 1993 Title: Geologic Map of Virginia Other_Citation_Details: Online_Linkage: http://www.mme.state.va.us/DMR/home.dmr.html End_Group End_Group Group: DIF_Author Last_name: U.S. Geological Survey First_name: N/A Email: jreddy@usgs.gov Phone: 607-266-0217, x3014 Group: Address 30 Brown Road Ithaca, New York 14850 USA End_Group End_Group DIF_Revision_Date: 20010830 Science_Review_Date: