Västervik - eine Formation aus der Montana-Zeit, die Brisantes zu bieten hat...
IS IT POSSIBLE FOR FOSSILS TO BE
PRESERVED IN METAMORPHIC ROCK?
Marc Srour, invertebrate palaeontologist
Yes, but only to a certain degree - anything with more pressure and temperature than greenschist facies will probably erase everything, as Sean Sultan says in his answer. This applies to both body fossils and to chemical ones (biomarkers, etc.).
In some cases, a tiny bit of metamorphism (200-400°C, so between prehnite-pumellyite and low-grade greenschist) after fossilisation can help preservation - this is what's allowed some of the oldest evidence of microbial life from the Archaean to be preserved. Or, it can be relatively harmless. The Hunsrück Slates, where I did my BSc. work, are all slightly-metamorphosed slates; this made fossils rare (you can only find them where the cleavage is parallel to the bedding), but didn't affect those that were preserved at all besides occasional shearing. And finally, most of the time, metamorphism is destructive, as in the Latham Shales of California (Lower Cambrian), a Burgess Shale-quality site, but all the preserved biota is more or less destroyed because of local low-grade metamorphism,
So, basically, metamorphism is mostly destructive, because the heat and pressure destroys fossils. But in some exceptional cases, it can promote mineralisation or lead to special diagenetic pathways that result in minerals getting replaced by more durable ones, meaning better fossils. But that's exceptional, and will only occur at very slight metamorphism.
Sean Sultan, Geology Student
Not likely. The intense heat and pressure involved in creating metamorphic rocks would erase any fossils originally present in the parent rock. I have been informed that some fossils still remain in slate but are usually smeared or stretched (http://geology.about.com/od/rock...). There are some images of this and some undeformed fossils in slate on google images if you search "fossils in slate." However, the processes which most metamorphic rocks undergo will erase any evidence of a fossil.
(Found in quora.com / Paleontology)