The Great Unconformity

[stoutfellow]

The Great Unconformity is a paleontological mystery: there is a stratigraphic boundary where the rocks below are much, much older than the rocks above. An explanation has been proposed: it's the result of worldwide erosion by glaciers during one of the Snowball Earth episodes. It may also explain the apparent suddenness of the Cambrian Explosion, when the number and diversity of life forms on Earth rose sharply.

I remember Isaac Asimov, in one of his 1960s science columns, proposing that it was the result of massive tides from the much-nearer Moon, but that has the disadvantage of not explaining the suddenness of the transition. Still, it seems that he was in the vicinity of a better answer.

Comments

[ndrosen]

One of uncles sent the family email list a link to a popular article about this; another uncle, who is a geologist, commented that the Snowball Earth period has long been known, and the popular science press has apparently finally noticed.

Not that I mean to speak ill of the authors of the paper you linked to; they may have done a good job of making connections and setting forth the reasons supporting the explanation they propose.

[stoutfellow]

Yes, that's the main thing: the authors have identified certain changes in the isotopic composition of zircon that are consistent with this idea. (I have no idea whether that makes sense, but I assume the people at PNAS do.)