Are you referring to the New Chronology proposed by Fomenko? Or just in general? Historical Archaeology? Paleontology? Things like Piltdown man and...oh there was another one someone posted a link to a video a week ago but I can't remember the name...

No but I have seen augmented archeological evidence, to suit territorial claims.

Most claims of this happening in this day and age are utter nonsense. Archaeology is the pursuit of knowledge, and is considered by many be a science (or soft science). We care about evidence. Interpretation of such evidence will vary, so the only cover-ups I can really see happening include the interpretation being skewed toward previously existing understanding of the past, which isn't exactly conscious or malicious.

Otherwise, things could be "covered up" or ignored and not reported on because a developer wants their project done quickly and in the spot they want it done, and some inconvenient archaeology showed up during excavation. This would not be an academic cover-up, but an industry one. I'm quite sure that happens on occasion, and it shouldn't.

[en.wikipedia.org]

Here is something that has been covered up. Read carefully and note the description of the first ossuary on the list. The implications are enormous. ​

Can you elaborate?

What? Like dirt?