Significance of the Onondaga Map Layers 
Map layers associated with the Marcellus Shale in the interactive mapping system include various Onondaga map layers. This is confusing to many users--i.e., why don't we use maps showing the Marcellus structure? The answer is simple--because we don't yet have those specific map layers for the Marcellus Shale. In order to provide this geological information, we are using map layers created for adjacent stratigraphic units to provide approximately similar information as for the Marcellus. 

Structure Map Layers - The Onondaga Limestone and equivalent units underlie the Marcellus Shale. The top of the Onondaga Limestone and equivalents is approximately equal to the base of the Marcellus Shale. So, a map showing the structure on the top of the Onondaga Limestone provides essentially the same information as a structure map on the base of the Marcellus Shale.

Map display is in "Web Mercator" projection.  Data download of GIS files are in NAD 1983, UTM zone 17 north projection.
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{'Title': 'West Virginia Marcellus Shale', 'Author': 'West Virginia Geological and Economic Survey (WVGES)', 'Comments': 'Significance of the Onondaga Map Layers \nMap layers associated with the Marcellus Shale in the interactive mapping system include various Onondaga map layers. This is confusing to many users--i.e., why don\'t we use maps showing the Marcellus structure? The answer is simple--because we don\'t yet have those specific map layers for the Marcellus Shale. In order to provide this geological information, we are using map layers created for adjacent stratigraphic units to provide approximately similar information as for the Marcellus. \n\nStructure Map Layers - The Onondaga Limestone and equivalent units underlie the Marcellus Shale. The top of the Onondaga Limestone and equivalents is approximately equal to the base of the Marcellus Shale. So, a map showing the structure on the top of the Onondaga Limestone provides essentially the same information as a structure map on the base of the Marcellus Shale.\n\nMap display is in "Web Mercator" projection.  Data download of GIS files are in NAD 1983, UTM zone 17 north projection. \n', 'Subject': 'Wells, thickness, outcrop and Onondaga Structure pertaining to Marcellus Shale in West Virginia.', 'Category': '', 'AntialiasingMode': 'None', 'TextAntialiasingMode': 'Force', 'Keywords': 'Marcellus,"Marcellus Shale","Marcellus Geology",Onondaga,"Onondaga Geology","Shale Gas"'}
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