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>> Fossils are unlikely to "wash down" to younger layers because the younger sediments overlay the older ones. Only in an area where a tremendous upheaval has occurred and inverted the stratigraphy (like the rim rocks around Meteor Crater, AZ) or where faulting has aligned the sequence of adjacent rocks out of order would you be able to find older fossils washing down into younger fossil beds. << My wife and her former advisor are both taphonomists and have studied this issue. Also, I've worked on sites relevant to this question as well. Fossils from earlier time periods very often end up in later strata. For example, in the western rivers, like the Snake and it's tributaries, pleistocene fossils are today eroding out of the banks and being redeposited in sand bars that also contain bones of recently dead critters. So, for example, extinct camel bones are being buried together with regular cow bones! As you suggest, it is often easy to tell when this happens. For example, the fossils are rocks, not bones, so they are eroded, scraped, oriented, etc as rocks and not as bones, and thus show up as being very different. The bones that I have found fossilized from two dramatacially different time periods were very obviously fossilized in different ways, and although it was difficult to work out (took years of research and a bunch of geologists, well, really one or two really smart geologists and about a half hour, but those guys didn't show up for the frist two years <g>) to figure out the exact (more or less) sequence of events. Those fossils were from about 2.5 million years and about 6,000 years in age! Cheers, GTL – Greg Laden, Written 19-Aug-1994 @ 14:11:14 Using: Windows NavCIS PRO 1.25