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.