Identification_Information:
Citation:
Citation_Information:
Originator: Gale C. Blackmer, Senior Geologic Scientist, Pennsylvania Bureau of Topographic and Geologic Survey, Department of Conservation and Natural Resources
Publication_Date: October, 2005
Title:
Geologic units of a portion of the Wilmington 30- by 60-minute quadrangle
Geospatial_Data_Presentation_Form: vector digital data
Series_Information:
Series_Name: Open-File Report
Issue_Identification: OFBM 05-01.0
Publication_Information:
Publication_Place: Harrisburg, PA
Publisher: Pennsylvania Bureau of Topographic and Geologic Survey (Pennsylvania Geological Survey)
Description:
Abstract:

The Wilmington 30- x 60-Minute Quadrangle includes rocks that range in age from Middle Proterozoic to Silurian, and in metamorphic grade from lowest greenschist to granulite facies. Tectonic environments represented in the quadrangle include continental basement rocks, shelf sediments, marine sediments spanning rift to drift, a fragment of a magmatic arc, and deep-seated plutons. By way of introduction, a speculative tectonic history for the area follows. This history is compiled from discussion with all the authors whose work contributed to this map, with additional input from Plank and others (2000) and Srogi (2004). As the Iapetus Ocean opened during the latest Precambrian to early Cambrian, a rift margin developed on the eastern side (present coordinates) of Laurentia. Sediments that became the Glenarm Group, Glenarm Wissahickon, and Mt. Cuba Wissahickon were deposited in marine rift basins floored by continental crust represented by the Baltimore Gneiss. In these rift basins, the sediments intermingled with continental rift-related basalts that became the White Clay Creek Amphibolite. The Kennett Square Amphibolite with its ocean-floor geochemical signature, now found associated with the Mt. Cuba Wissahickon, represents the transition from rift to drift. The Peters Creek Schist, with its interlayers of oceanic-affinity Bald Friar Metabasalt, may represent the culmination of sedimentation in the rift basins. As true sea-floor spreading progressed during the Cambrian, a passive margin formed inboard of the rift basins. The transgressive shelf sequence of the Chickies Formation, Antietam and Harpers Formations, and Conestoga Formation through Vintage Formation was deposited at this time over Laurentian continental basement gneiss. The clay-rich sediments that became the Octoraro Formation were deposited on the continental slope and rise. In the early Ordovician, the Wilmington Complex metaigneous rocks were forming as part of a magmatic arc built over an east-dipping subduction zone in the Iapetus Ocean. The boninitic amphibolites in the Rockford Park Gneiss indicate subduction of relatively young and hot lithosphere, possibly even a mid-ocean ridge. Intimate interlayering of Mt. Cuba Wissahickon with Wilmington Complex rocks in Pennsylvania and Delaware suggest that the eastern part of the Mt. Cuba may have been deposited with Wilmington Complex volcanic rocks in a forearc basin, or it may have been tectonically incorporated into the forearc accretionary prism during subduction. The sliver of Mt. Cuba Wissahickon east of the Wilmington Complex exhibits a metamorphic episode contemporaneous with arc magmatism. Evidence of shelf drowning and deformation in the sedimentary rocks of central and eastern Pennsylvania indicates that the Taconic Orogeny reached this area in the late Ordovician. Finding evidence of the same orogeny in the deep-seated rocks of the Pennsylvania Piedmont is more problematic. As yet, no evidence of metamorphic mineral growth during the late Ordovician has been found. However, growth of metamorphic monazite during the early Silurian is common to the Wilmington Complex, Wissahickon Formation (restricted sense, as defined herein), and Mt. Cuba Wissahickon formation at least as far west as the Delaware state line (the western Mt. Cuba and the Glenarm Wissahickon have not been investigated). A metamorphic event of this magnitude and intensity requires tectonic burial, perhaps as the magmatic arc overrode its forearc accretionary complex. Northeast-trending fabrics and major thrust faults in the area date from this period of subduction and collision. The position of the Wissahickon Formation (restricted sense; eastern part of the historic Wissahickon Formation) throughout the preceding period is enigmatic. It must be early Silurian or older in age because it is intruded by the Silurian-aged Springfield Granodiorite. Unlike the adjacent Mt. Cuba Wissahickon, it carries no evidence of stratigraphic interrelation to the Wilmington Complex, or of a metamorphic episode that might be related to Wilmington Complex magmatism. The geochemistry of interlayered amphibolites suggest that it may have been deposited in a back-arc basin with continental crustal input, perhaps in some other part of Iapetus. The Silurian was a period of high heat flow in the Pennsylvania Piedmont, marked by high-temperature metamorphism centered on the Brandywine Blue Gneiss and emplacement of both mafic and felsic plutons. The Arden Plutonic Supersuite, the Springfield Granodiorite, and the Ridley Park Granite were emplaced at this time. Because the trace element geochemistries of Silurian mafic igneous rocks are close to back-arc basin basalts, Plank and others (2001) suggest an extensional environment with high mantle heat flow. Such an environment could have resulted from slab break-off following oblique collision of the Wilmington Complex arc, or from back-arc extension over a newly-established west-dipping subduction zone. Early Devonian metamorphism recorded by monazite growth in the Wissahickon Formation (restricted sense) marks renewed plate convergence. Late fabrics and motion along high-angle ductile shear zones (Rosemont Fault, Cream Valley Fault, zone marked by Peters Creek tectonite) are probably related to the Alleghanian Orogeny. Minor high-angle brittle faults, some of which exhibit undeformed slickensides, probably date from Mesozoic extension.

Purpose:

For use as primary or supplementary data in mapping and/or decision making.

Supplemental_Information:

The datasets are not intended to be used for detailed or site-specific analyses, nor are they intended to be used at any scale finer (larger) than 1:50,000 (e.g., use at 1:24,000 scale is inappropriate). This report has not been reviewed for conformity with the publication standards of the Bureau of Topographic and Geologic Survey.

Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 2005
Ending_Date: 2005
Currentness_Reference:

publication date

Status:
Progress: Complete
Maintenance_and_Update_Frequency: As needed
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -75.878493
East_Bounding_Coordinate: -75.249004
North_Bounding_Coordinate: 40.003029
South_Bounding_Coordinate: 39.721352
Keywords:
Theme:
Theme_Keyword_Thesaurus: Geology
Theme_Keyword: Ardentown Granitic Suite
Theme_Keyword: Geologic map
Theme_Keyword: Bedrock geology
Theme_Keyword: Areal geology
Theme_Keyword: Geologic units
Theme_Keyword: Pegmatite
Theme_Keyword: Glenarm Wissahickon formation
Theme_Keyword: Amphibolite
Theme_Keyword: Cockeysville Marble
Theme_Keyword: Setters Formation
Theme_Keyword: Setters quartzite
Theme_Keyword: Baltimore Gneiss
Theme_Keyword: Cambrian
Theme_Keyword: Late Proterozoic
Theme_Keyword: Ultramafic Rock
Theme_Keyword: Ridley Park Granite
Theme_Keyword: Mafic gneiss
Theme_Keyword: Springfield Granodiorite
Theme_Keyword: Wilmington Complex
Theme_Keyword: Arden Plutonic Supersuite
Theme_Keyword: Brandywine Blue Gneiss
Theme_Keyword: Lima Granite
Theme_Keyword: Conestoga Formation through Vintage Formation, undivided
Theme_Keyword: Chester Park gneiss
Theme_Keyword: Antietam and Harpers Formations, undivided
Theme_Keyword: Chickies Formation
Theme_Keyword: Octoraro Formation
Theme_Keyword: Peters Creek Schist
Theme_Keyword: Mt. Cuba Wissahickon formation
Theme_Keyword: Glenarm Wissahickon formation
Theme_Keyword: Cockeysville Marble
Theme_Keyword: Glenarm Group
Theme_Keyword: Setters microcline gneiss
Theme_Keyword: Perkins Run Gabbronorite Suite
Theme_Keyword: Biotite tonalite
Theme_Keyword: Avondate schist
Theme_Keyword: Green Lawn marble
Theme_Keyword: Baker gneiss
Theme_Keyword: Doe Run schist
Theme_Keyword: Laurels schist
Theme_Keyword: Greystone schist
Theme_Keyword: Undifferentiated Baltimore Gneiss
Theme_Keyword: Undifferentiated amphibolite facies gneiss
Theme_Keyword: mafic amphibolite facies gneiss
Theme_Keyword: Franklin Marble
Theme_Keyword: Sycamore Mills gneiss
Theme_Keyword: Undifferentiated granulite granulite facies gneiss
Theme_Keyword: Quartzofeldspathic granulite facies gneiss
Theme_Keyword: Intermediate and mafic granulite facies gneiss
Theme_Keyword: Mafic and felsic gneiss
Place:
Place_Keyword: Chester County
Place_Keyword: Piedmont physiographic province
Place_Keyword: Piedmont Upland section
Place_Keyword: Montgomery County
Place_Keyword: Philadelphia County
Place_Keyword: Coatesville 7.5-minute quadrangle
Place_Keyword: West Grove 7.5-minute quadrangle
Place_Keyword: Newark East 7.5-minute quadrangle
Place_Keyword: Unionville 7.5-minute quadrangle
Place_Keyword: Kennett Square 7.5-minute quadrangle
Place_Keyword: West Chester 7.5-minute quadrangle
Place_Keyword: Wilmington North 7.5-minute quadrangle
Place_Keyword: Media 7.5-minute quadrangle
Place_Keyword: Marcus Hook 7.5-minute quadrangle
Place_Keyword: Lansdowne 7.5-minute quadrangle
Place_Keyword: Bridgeport 7.5-minute quadrangle
Place_Keyword: Wilmington 30- by 60-minute quadrangle
Access_Constraints: None
Use_Constraints:

The data for the geologic units, structures, and other features contained in these maps and shapefiles may be used provided that credit for the original (unaltered) datasets is given to the author, Gale C. Blackmer, and the publisher, Pennsylvania Bureau of Topographic and Geologic Survey, Department of Conservation and Natural Resources. Users shall clearly indicate the source of the data. Users who modify the data in any way are obligated to describe the types of modifications they have made, including modifications to hard-copy maps. Users are not to misrepresent Pennsylvania Bureau of Topographic and Geologic Survey (Pennsylvania Geological Survey, or PaGS) datasets, nor to imply that changes they (users) have made were approved by the PaGS. These datasets are public information and, as such, the data may be used as a reference source and may be interpreted by organizations, agencies, units of government, or others based on needs; however, each user is responsible for the appropriate application of the data. Federal, state, or local regulatory bodies are not to reassign to the Bureau of Topographic and Geologic Survey any authority for the decisions they make using these datasets. The datasets are not meant for site-specific analysis or for use at scales finer (i.e., larger, more detailed) than 1:50,000. Users are not to misrepresent the datasets by presenting them at scales for which they are not intended, nor to imply that presentation at such scales is approved by the PaGS. Not for commercial resale. Please refer also to the section on Distribution_Liability for important information concerning the appropriate use of the datasets.

Point_of_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Gale C. Blackmer
Contact_Organization: Pennsylvania Bureau of Topographic and Geologic Survey, Department of Conservation and Natural Resources
Contact_Position: Senior Geologic Scientist
Contact_Address:
Address_Type: mailing and physical address
Address:

3240 Schoolhouse Road

City: Middletown
State_or_Province: PA
Postal_Code: 17057
Country: USA
Contact_Voice_Telephone: 717-702-2032
Contact_Facsimile_Telephone: 717-702-2065
Contact_Electronic_Mail_Address: gblackmer@state.pa.us
Hours_of_Service: 8:00 a.m.- 4:30 p.m., Monday-Friday
Browse_Graphic:
Data_Set_Credit:

Bedrock geology and digital data - Gale C. Blackmer, Bureau of Topographic and Geologic Survey, Middletown, PA 17057.

Security_Information:
Security_Classification_System: None
Native_Data_Set_Environment:
Microsoft Windows 2000 Version 5.0 (Build 2195) Service Pack 4; ESRI ArcCatalog 9.1.0.722
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Data_Quality_Information:
Completeness_Report:

Map is a compilation of eleven 7.5-minute quadrangle maps. Mapping is as complete as the time frame allowed. Further research and revision is always possible and encouraged. Soils and surficial materials were not mapped and are not included in this report.

Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:

Geologic contacts were seldom directly observed in the field. In general, the horizontal accuracy of geologic contacts (which include faults) is no better than the distance between the observations. Contacts were placed using the author's best judgment based on outcrop lithologic observations, observed structural patterns, driller's logs for water wells, and in some cases, topography. Data stations were located in the field on 1:24,000-scale quadrangle maps and using GPS. The final composite map was compiled at 1:50,000 scale.

Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:

The vertical positional accuracy of geologic contacts and faults is unknown but is no better than the standard for 1:24,000-scale quadrangle maps with 10-foot topographic contours, which is ±5 feet or half the contour interval for 90 percent or more of vertical points tested.

Lineage:
Source_Information:
Source_Citation:
Citation_Information:
Originator: Blackmer, G. C.
Publication_Date: 2005
Title:
Bedrock geology of the Coatesville quadrangle, Chester County, Pennsylvania: Pennsylvania Geological Survey, 4th ser., Atlas 189b, CD-ROM.
Series_Information:
Publication_Information:
Type_of_Source_Media: CD-ROM
Source_Citation_Abbreviation:
Blackmer, G. C., 2004
Source_Information:
Source_Citation:
Citation_Information:
Title:
Blackmer, G. C., field mapping 1999-2002 (STATEMAP).
Type_of_Source_Media: Map
Source_Citation_Abbreviation:
Blackmer, G. C., 1999-2002
Source_Information:
Source_Citation:
Citation_Information:
Publication_Date: Unpublished Material
Title:
Wiswall, C. G., field mapping 2002-2005 (STATEMAP).
Type_of_Source_Media: Map
Source_Citation_Abbreviation:
Wiswall, C. G., 2002-2005
Source_Information:
Source_Citation:
Citation_Information:
Publication_Date: 2000
Title:
Schenck, W. S., Plank, M. O., and Srogi, L., 2000, Bedrock geologic map of the Piedmont of Delaware and adjacent Pennsylvania: Delaware Geological Survey Map Series No. 10, scale 1:36,000.
Other_Citation_Details:
Map Series No. 10
Type_of_Source_Media: Map
Source_Citation_Abbreviation:
Schenck, W. S., Plank, M. O., and Srogi, L., 2000,
Source_Information:
Source_Citation:
Citation_Information:
Title:
Bosbyshell, H., field mapping 2002-2004 (STATEMAP).
Type_of_Source_Media: Map
Source_Citation_Abbreviation:
Bosbyshell, H., field mapping 2003-2004 (STATEMAP).
Source_Information:
Source_Citation:
Citation_Information:
Title:
Williams, S., field mapping, 2002.
Type_of_Source_Media: Map
Source_Citation_Abbreviation:
Williams, S., 2002.
Process_Step:
Process_Description:

Map is a compilation of previous geologic mapping (see data sources). The final map was prepared using ESRI ArcView 9.1 software.

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Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Vector
Point_and_Vector_Object_Information:
SDTS_Terms_Description:
SDTS_Point_and_Vector_Object_Type: G-polygon
Point_and_Vector_Object_Count: 43
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Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Grid_Coordinate_System:
Grid_Coordinate_System_Name: Universal Transverse Mercator
Universal_Transverse_Mercator:
UTM_Zone_Number: 18
Transverse_Mercator:
Scale_Factor_at_Central_Meridian: 0.999600
Longitude_of_Central_Meridian: -75.000000
Latitude_of_Projection_Origin: 0.000000
False_Easting: 500000.000000
False_Northing: 0.000000
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: coordinate pair
Coordinate_Representation:
Abscissa_Resolution: 0.000128
Ordinate_Resolution: 0.000128
Planar_Distance_Units: meters
Geodetic_Model:
Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: Geodetic Reference System 80
Semi-major_Axis: 6378137.000000
Denominator_of_Flattening_Ratio: 298.257222
Vertical_Coordinate_System_Definition:
Altitude_System_Definition:
Altitude_Resolution: 0.000010
Altitude_Encoding_Method: Explicit elevation coordinate included with horizontal coordinates
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Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label: Polygons
Attribute:
Attribute_Label: Shape
Attribute_Definition:

Feature geometry.

Attribute_Definition_Source:
Attribute_Domain_Values:
Unrepresentable_Domain:
Coordinates defining the features.
Attribute:
Attribute_Label: FID
Attribute_Definition:

Internal feature number.

Attribute_Definition_Source:
Attribute_Domain_Values:
Unrepresentable_Domain:
Sequential unique whole numbers that are automatically generated.
Attribute:
Attribute_Label: Lithology
Attribute:
Attribute_Label: Symbol
Attribute:
Attribute_Label: Order_
Attribute:
Attribute_Label: Shape_Leng
Attribute:
Attribute_Label: Shape_Area
Attribute_Definition:

Area of feature in internal units squared.

Attribute_Domain_Values:
Unrepresentable_Domain:
Positive real numbers that are automatically generated.
Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label: faults05
Attribute:
Attribute_Label: FID
Attribute_Definition:
Internal feature number.
Attribute_Definition_Source:
ESRI
Attribute_Domain_Values:
Unrepresentable_Domain:
Sequential unique whole numbers that are automatically generated.
Attribute:
Attribute_Label: Shape
Attribute_Definition:
Feature geometry.
Attribute_Definition_Source:
ESRI
Attribute_Domain_Values:
Unrepresentable_Domain:
Coordinates defining the features.
Attribute:
Attribute_Label: Type
Attribute:
Attribute_Label: Fault_Name
Attribute:
Attribute_Label: Shape_Leng
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Distribution_Information:
Resource_Description: Downloadable Data
Distribution_Liability:

These data files and documentation are provided "as is," and the user assumes the entire risk as to their quality and performance. The Commonwealth of Pennsylvania makes no guarantee or warranty concerning the accuracy of information contained in the geographic data or accompanying documentation. The Commonwealth of Pennsylvania further makes no warranties, either expressed or implied, as to any other matter whatsoever, including, without limitation, the completeness or condition of the product, or its fitness for any particular purpose. The burden for determining fitness for use lies entirely with the user. Although these data have been processed successfully on a computer system at the Department of Conservation and Natural Resources, the Commonwealth of Pennsylvania makes no warranty, expressed or implied, regarding the use of the data files or accompanying documentation on any other computer system, nor does the act of distribution constitute any such warranty. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the Commonwealth of Pennsylvania government or any agency thereof. The user shall save the Commonwealth of Pennsylvania harmless and indemnify it from any suits, claims, or actions arising out of the use of or any defect in the data files or accompanying documentation. The Commonwealth of Pennsylvania assumes no legal liability for the accuracy, completeness, or usefulness of the data files and accompanying documentation. In no event shall the Commonwealth of Pennsylvania have any liability whatsoever for payment of any consequential, incidental, indirect, special, or tort damages of any kind, including, but not limited to, any loss of profits arising out of use of or reliance on the geographic data. Not for commercial resale.

 
 
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Metadata_Reference_Information:
Metadata_Date: 20051017
Metadata_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Gale C. Blackmer
Contact_Organization: PA DCNR, Bureau of Topographic and Geologic Survey
Contact_Position: Senior Geologic Scientist
Contact_Address:
Address_Type: mailing and physical address
Address:

3240 Schoolhouse Road

City: Middletown
State_or_Province: PA
Postal_Code: 17057
Country: USA
Contact_Voice_Telephone: 717-702-2032
Contact_Electronic_Mail_Address: gblackmer@state.pa.us
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Metadata_Time_Convention: local time
Metadata_Use_Constraints:
Material from this report may be published if credit is given to Department of Conservation and Natural Resources, Bureau of Topographic and Geologic Survey. Bureau of Topographic and Geologic Survey, 3240 Schoolhouse Road, Middletown, PA 17057-3534
Metadata_Extensions:
Online_Linkage: http://www.esri.com/metadata/esriprof80.html
Profile_Name: ESRI Metadata Profile
 
 
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