Here is an article about a hammer found in cretaceous rock. Athough the article places doubts, the artifact is a good example of how cretaceous rock may not be millions of years old. Of course I don't believe it is. The hammer also looks old but intelligently put together.
http://paleo.cc/paluxy/hammer.htm
The biggest problem with this one is that it was not documented in situ and as such the association with the Cretaceous can not be confirmed. This one problem renders it useless.
Dinosaur tracks found in cretaceous