I took a map from a report, exported it as a PNG, and georeferenced it in arcmap. I'm trying to combine this with a geologic map polygon shape file so that only the geologic map that lies within the georeferenced map will be there. I've tried spatially joining the files, but it does not give the PNG as an option. I've also tried exporting the georeferenced map to save it as a different type of file, but it is a strange shape, and it gets made into a rectangle with grey filling in around the edges. I'm a new user, so I'm probably just missing something simple.