Identification_Information: Citation: Citation_Information: Originator: Amy R. Clark Originator: Charles D. Blome Originator: Jason R. Faith Publication_Date: 2009 Title: Map Showing Geology and Hydrostratigraphy of the Edwards Aquifer Catchment Area, Northern Bexar County, South-Central Texas Edition: version 1 Geospatial_Data_Presentation_Form: vector digital data Series_Information: Series_Name: Open-File Report Issue_Identification: 2009-1008 Publication_Information: Publication_Place: Denver, Colorado Publisher: U.S. Geological Survey Online_Linkage: http://pubs.usgs.gov/of/2009/1008 Description: Abstract: The San Antonio metropolitan area in Bexar County, south-central Texas, is home to almost 2 million people whose primary source of water is supplied by the Edwards and Trinity aquifers. The carbonate rock units forming these aquifers include the Edwards and Trinity Groups. The regional geology is structurally complex due to deformation related to the Balcones fault zone, an intricate network of Miocene-age normal faults that trend northeast and are downthrown to the southeast. The Edwards aquifer is the most prolific ground-water source in Bexar County and supplies water for agricultural, residential, commercial, and industrial purposes. It also supplies major springs that support recreational activities and businesses, and offers habitat for several endangered species. Although the Edwards aquifer regional ground-water flow is east-northeast and parallels the major fault trend of the Balcones fault zone, local variations in ground-water flow patterns are most likely related to secondary fracture permeability produced by extensional deformation. The Trinity aquifer supplies water for residential, commercial, and industrial uses north of the San Antonio metropolitan area. The Glen Rose Limestone contains the upper Trinity aquifer and parts of the middle Trinity aquifer and it also forms the catchment area of the Edwards aquifer recharge zone to the south. The Glen Rose Limestone is relatively impermeable and is the primary lower confining unit of the Edwards aquifer. The Trinity aquifer also provides recharge to the Edwards aquifer by supplying base flow to several streams in the catchment area that flow south and down-gradient over the Edwards aquifer recharge zone. Recharge may also occur through subsurface, lateral migration of ground water into stratigraphically younger Edwards Group rocks that are faulted against rocks of the Trinity Group. An improved understanding of the relationship between the Edwards and Trinity aquifers is crucial for effective characterization and management of the aquifers, both locally and throughout the region. The Trinity aquifer is subdivided into upper, middle and lower segments. Although the upper member of the Glen Rose Limestone contains enough clay and marl beds to form a relatively impermeable unit that restricts infiltration of surface water and ground-water flow, the upper 150 m of the Glen Rose Limestone has substantial karst development. This may imply that the Glen Rose Limestone is not as an effective aquiclude as was previously thought and therefore the Trinity aquifer may have some lateral hydrologic connectivity with the Edwards aquifer. The lower member of the Glen Rose Limestone and the underlying Hensel Sand and Cow Creek Limestone contain the middle part of the Trinity aquifer, the most productive of the three aquifer segments. This middle part of the aquifer is largely unconfined but the Trinity water-bearing, down- faulted confined portions of the Balcones fault zone are suspected to lose water to the Edwards aquifer. A.K. Clark subdivided the upper member of the Glen Rose Limestone into five informal hydrostratigraphic zones (A-E) to better describe the unit’s hydrologic properties. The same five hydrostratigraphic subdivisions of the Glen Rose Limestone were used by Clark in 2005 when mapping the geology of Camp Stanley. R.W. Maclay and T.A. Small originally proposed a similar hydrostratigraphic subdivision for the Edwards Group (Person and Kainer Formations), which included the Georgetown Formation as its youngest member. The other Edwards hydrostratigraphic members of Maclay and Small include, in descending order, the Cyclic and marine, Leached and collapsed, Regional dense, Grainstone, Kirschberg evaporite, Dolomitic, and Basal nodular members. This study includes 1:50,000-scale hydrostratigraphic mapping of the northern Bexar County area, which encompasses all or parts of seven 7.5-minute quadrangles: Jack Mountain, Van Raub, Camp Bullis, Bulverde, San Geronimo, Helotes, and Castle Hills. The resulting geologic map shows the distribution of informal hydrostratigraphic members of both the Edwards Group and the underlying upper member of the Glen Rose Limestone. Exposures of Glen Rose Limestone alone cover approximately 467 square kilometers in northern Bexar County. The other purpose of this study is to describe and name the informal hydrostratigraphic members of the upper part of the Glen Rose Limestone. Purpose: The purpose of this study is to determine the geologic framework and to describe the hydrostratigraphic subdivisions of the Glen Rose Limestone outcropping within the catchment area of the Edwards aquifer in northern Bexar County, Texas. Exposures of Glen Rose Limestone cover approximately 467 square kilometers of Bexar County. Of these 467 square kilometers, an estimated 20 percent is urban or developed land whereas 80 percent remains undeveloped. The data are intended to illustrate the detailed geographical extent of the stratigraphic units and faulting of northern Bexar County, Texas. Supplemental_Information: The current map database incorporates geologic data from geologic mapping (2000-2004) by the U.S. Geological Survey (Texas Water Science Center – San Antonio) at a county-wide scale of 1:24,000. FILES INCLUDED IN THIS DATA SET: BEXAR_GEO(coverage) -- geologic units, contacts and faults BEXAR_GEO_POLYGON.SHP -- geologic units BEXAR_GEO_ARC.SHP -- geologic contacts and faults 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 metatdata file my include some ARC/INFO-specific terminology. Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 2009 Currentness_Reference: publication date Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -98.806402 East_Bounding_Coordinate: -98.372718 North_Bounding_Coordinate: 29.760868 South_Bounding_Coordinate: 29.572169 Keywords: Theme: Theme_Keyword_Thesaurus: AGI Glossary of Geology Theme_Keyword: Edwards Group Theme_Keyword: Edwards aquifer Theme_Keyword: hydrostratigraphic memberss Theme_Keyword: Edwards recharge zone Theme_Keyword: Trinity Group Theme_Keyword: Trinity aquifer Theme_Keyword: catchment area Theme_Keyword: Glen Rose Limestone Theme_Keyword: Balcones fault zone Theme_Keyword: Person Formation Theme_Keyword: Kainer Formation Place: Place_Keyword_Thesaurus: Board of Geographic Names Place_Keyword: Bexar County Place_Keyword: San Antonio Place_Keyword: South-central Texas Place_Keyword: Jack Mountain Place_Keyword: Van Raub Place_Keyword: Camp Bullis Place_Keyword: Bulverde Place_Keyword: San Geronimo Place_Keyword: Helotes Place_Keyword: Castle Hills Access_Constraints: none Use_Constraints: None. Acknowledgement of the U.S. Geological Survey would be appropriate in products derived from these data. Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Charles Blome Contact_Organization: U.S. Geological Survey Contact_Address: Address_Type: mailing address Address: Mail Stop 980, Bldg 025 Address: Box 25046 City: Denver State_or_Province: CO Postal_Code: 80225 Country: USA Contact_Voice_Telephone: 303.236.1278 Contact_Facsimile_Telephone: 303.236.5349 Contact_Electronic_Mail_Address: cblome@usgs.gov Hours_of_Service: 8:00 a.m. - 5:00 p.m. Browse_Graphic: Browse_Graphic_File_Name: http://pubs.usgs.gov/of/2009/1008/ Browse_Graphic_File_Description: graphical representation of map Browse_Graphic_File_Type: PDF Native_Data_Set_Environment: Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.0.0.535 Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: Attributes have been checked by available authors and reviewers for accuracy and completenes. Logical_Consistency_Report: Map elements were visually checked for overshoots, undershoots, duplicate features, and other errors. ARC/INFO software was used to create topological relations among features. Features were not duplicated, but coincident lines exist between data layers where appropriate. Completeness_Report: Original hydrostratigraphic map units were collected and digitized at appropriate resolution for portrayal at various scales. The digitized data were then compiled together throughout the study area for a seamless presentation. Data are complete--No features were eliminated or generalized. Unit properties are described in the map text. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: The original data were created by delineating the boundaries of hydrostratigraphic members on 7.5-minute USGS topographic maps at 1:24,000 scale. Potential exists for errors in location by the geologist in the field. Lineage: Process_Step: Process_Description: Hydrostratigraphic members were mapped in the field onto 7.5-minute topographic quadrangles. Process_Date: 2000 Process_Step: Process_Description: Mapped hydrostratigraphic members were digitized off the 7.5-minute topographic quadrangles and attributed. Process_Date: 2000 Process_Step: Process_Description: Topological errors were checked and corrected for duplicate polygons and lines, gaps, overshoots, undershoots, and dangles. Process_Date: 2006 Process_Step: Process_Description: Metadata imported. Process_Date: 2008 Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Grid_Coordinate_System: Grid_Coordinate_System_Name: Universal Transverse Mercator Universal_Transverse_Mercator: UTM_Zone_Number: 14 Transverse_Mercator: Scale_Factor_at_Central_Meridian: 0.999600 Longitude_of_Central_Meridian: -99.000000 Latitude_of_Projection_Origin: 0.000000 False_Easting: 500000.000000 False_Northing: 0.000000 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Planar_Distance_Units: meters Coordinate_Representation: Abscissa_Resolution: 10.0 Ordinate_Resolution: 10.0 Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1927 Ellipsoid_Name: Clarke 1866 Semi-major_Axis: 6378206.400000 Denominator_of_Flattening_Ratio: 294.978698 Entity_and_Attribute_Information: Overview_Description: Entity_and_Attribute_Overview: DATASETS: BEXAR_GEO item descriptions: GEOLOGY - abbreviated map unit symbol DESCRIPTION - brief geologic explanation of rock unit GROUP - the major litho-stratigraphic unit, higher in rank than Formation GEOLOGY DESCRIPTION GROUP Kgrc Cavernous hydrostratographic member- Trinity Group Glen Rose Limestone, upper member (Lower Cretaceous). Kgrcb Camp Bullis hydrostratographic member- Trinity Group Glen Rose Limestone, upper member (Lower Cretaceous). Kgrf Fossiliferous hydrostratographic member- Trinity Group Glen Rose Limestone, upper member (Lower Cretaceous). Kgrl Glen Rose Limestone, lower member Trinity Group (Lower Cretaceous). Kgrle Lower evaporite hydrostratographic member- Trinity Group Glen Rose Limestone, upper member (Lower Cretaceous). Kgrue Upper evaporite hydrostratographic member- Trinity Group Glen Rose Limestone, upper member (Lower Cretaceous). Kkbn Basal nodular hydrostratographic member- Edwards Group Kainer Formation(Lower Cretaceous). Kkd Dolomitic hydrostratographic member- Edwards Group Kainer Formation(Lower Cretaceous). Kkg Grainstone hydrostratographic member- Edwards Group Kainer Formation(Lower Cretaceous). Kkke Kirschberg evaporite hydrostratographic member- Edwards Group Kainer Formation(Lower Cretaceous). Kplc Leached and collapsed hydrostratographic member- Edwards Group Person Formation(Lower Cretaceous). Kprd Regional dense hydrostratographic member- Edwards Group Person Formation(Lower Cretaceous). item descriptions: DESCRIPTION - description of line features, using digital cartographic standards DESCRIPTION contact-approximately located fault-certain fault-inferred map boundary Entity_and_Attribute_Detail_Citation: none Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: U.S. Geological Survey Contact_Address: Address_Type: mailing address Address: Enterprise Publishing Network Address: Box 25046 Address: Denver Federal Center, MS-902 City: Denver State_or_Province: CO Postal_Code: 80225-0046 Country: USA Contact_Voice_Telephone: 303.236.5486 Resource_Description: Open-File Report 2009-1008 Distribution_Liability: Any use of trade, product or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although these digital spatial data have been subjected to rigorous review and are substantially complete, they are released on the condition that neither the USGS nor the United States Government may be held liable for any damage resulting from their authorized or unauthorized use. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: File_Decompression_Technique: ZIP archive (Windows) Format_Name: ArcGIS Coverage, Shapefile Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: http://pubs.usgs.gov/of/2009/1008 Fees: none Metadata_Reference_Information: Metadata_Date: 20090112 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Diana E. Pedraza Contact_Organization: U.S. Geological Survey Contact_Position: Geographer Contact_Address: Address_Type: mailing and physical address Address: 5563 DeZavala Rd. Suite 290 City: San Antonio State_or_Province: Texas Postal_Code: 78249 Country: USA Contact_Voice_Telephone: 210.691.9237 Contact_Facsimile_Telephone: 210.691.9200 Contact_Electronic_Mail_Address: dpedraza@usgs.gov Hours_of_Service: 8:00 am - 5:00 pm CST Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998 Metadata_Time_Convention: local time Metadata_Access_Constraints: none Metadata_Use_Constraints: none Metadata_Extensions: Online_Linkage: http://www.esri.com/metadata/esriprof80.html Profile_Name: ESRI Metadata Profile