Basement-Related Geospatial Database for Pennsylvania and GIS Products Generated Using the Database
Prepared by the Project Team (in alphabetical order): S.S. Alexander 1, R. Cakir 2, A. G. Doden3, D.P. Gold1, and S. I. Root4
1Department of Geosciences, The Pennsylvania State University
2Department of Geo-Environmental Engineering, The Pennsylvania State University
3GMRE Inc., State College, PA
4Department of Geology, College of Wooster, Ohio
This new integrated geospatial database provides an important resource for future scientific studies, classroom instruction, exploration for oil, gas and mineral resources and natural hazards assessments.
The principal objectives of this project are (1) to assemble a comprehensive geospatial database related to the basement structure and other basement related features in Pennsylvania, and (2) to make this database available electronically via the internet to users such as research scientists, educators, government agencies, private industry, and the public in general.
GIS DATA LAYERS
- Geographical (Pennsylvania Boundaries and Counties)
- Topographic (Digital Elevation Model, DEM)
- Satellite Imagery (Landsat TM)
- Geologic (Surface Geology Map)
- Tectonic (Faults and Dikes)
- Geophysical (Seismic, Gravity, Magnetic, Faults and Lineaments)
- Earthquakes (Historical and Instrumental Events)
- Boreholes (Deep Wells)
- Mineralogical (Lead-Zinc Mineral Deposits)
- A comprehensive geospatial database related to the basement geologic structure in Pennsylvania has been assembled and used to generate an initial (Version 1.0) basement contour map with associated geological and geophysical features superimposed.
- This geospatial database has also been used to generate other interesting combinations of the GIS data layers that can be used for future research or practical applications.
- This new comprehensive geospatial database is available to interested users via the Internet.
The basic GIS model depicted here illustrates the structure and use of the geospatial data sets comprising the GIS database. Any combination of the data layers can be used to construct a desired type of output product. The featured product in this project is a composite PA basement map (below) comprised of a combination of all the data layers.
A combination of all the data layers in the geospatial database was used to generate the composite basement depth contour map with the other basement-related features superimposed as shown below. This Version 1.0 map is the main GIS product produced in this project and it is included with the report. It should be regarded as a dynamic representation of basement features, because it will change anytime new observations are made or when additional existing data are identified and incorporated into the database. It is anticipated that periodic updates of this Version 1.0 map will be made indefinitely into the future. Users may also make alternative maps from the geospatial database to reflect their own interpretations of the data layers.
Several other products elucidating various features of the PA basement were produced using combinations of the data layers. Shown below is an overlay of gravity, faults and lineaments for Pennsylvania. The gravity anomalies are basement-related reflecting both the basement depth and the influence of density variations in the basement. The major lineaments shown coincide with abrupt spatial changes in major gravity anomalies, hence in basement structure.
Another combination of data layers illustrating correlated basement features is shown below. The magnetic field directly reflects variations in basement depth and composition, as the thick Paleozoic sequence above the basement contributes only negligibly to the observed anomalies. The major lineaments shown coincide with abrupt changes in the magnetic anomalies, controlled by the basement structure and composition. Historic and recent seismic activity is clustered in southeastern and northwestern PA and larger events appear to be associated with known mapped faults or boundaries between major magnetic anomalies or both. The earthquake focal mechanisms shown define the causative faults’ geometry and the principal tectonic stress orientations; the maximum stress is compressive, nearly horizontal and oriented at about N60E, consistent with other crustal stress measurements in eastern North America.
Shown below is a composite of topography, Landsat Thematic Mapper multispectral imagery and counties in eastern Pennsylvania along the Susquehanna River. The multispectral channels of Landsat imagery have been transformed to their principal components and three of them (color coded), each sensitive to different surface features, are used to generate the color composite map shown. Purple areas shown in the eastern portion of the map correspond to crystalline basement rocks that are present at the surface. This illustration is included here to show the versatility of the database more than to emphasize prominent basement features, however.
Shown below is a perspective view of the magnetic anomalies, lineaments and faults. The magnetic anomalies are depicted as topography in the top panel where the peaks are magnetic highs and valleys are minimums. Superimposed are the major lineaments (purple) and faults (red). The map view of these features (bottom) is shown directly below the magnetic relief display. The vertical relief scale and perspective viewing angle are arbitrary and can be easily changed to view features from any direction (e.g. along-strike or perpendicular to strike to enhance certain spatial features). Other types of anomalies (e.g. gravity) can be similarly displayed as topographic relief and correlated spatially with various other features of interest.
These are only a few of the combinations of the GIS data layers that can be used to investigate relationships among various types of geospatial data in this database. Users are encouraged to generate their own combinations (with or without supplementary data and information) to address particular problems of interest to them. (See “Software Requirements” that describes how this geospatial database can be accessed using a standard GIS software.)