I tried this and immediately got a message saying that it was 'uploading 104 photos' (the number on the iPad). A progress bar appeared which moved to about 10 % and has not changed.
If iTunes is trying to upload 104 photos, then the albums or events are not deselected in iTunes. Have you checked all checkmarks in the list of synced items, if still an album or event, Faces or Places are selected? Or your iPhoto library may have an iPod Photo cache folder that has a corruption. Then it would help to remove the cache from your iPhoto Library. See this help text: iTunes: Understanding the iPod Photo Cache folder
could it be that the photos were originally in iPhoto on my iPad which no longer exists after upgrading to OS 8
iPhoto on your iPad has only been showing you photos that are stored elsewhere. It has referenced the photos in other apps and only stored albums with edited copies.
Have you migrated your iPhoto Library to the Photos.app? Migrating from iPhoto for iOS to Photos on iOS 8
Then you should be able to delete all photos in Photos, that have been migrated to Photos.