Young earth explanations for Angular Unconformities

Looks like a pretty good summary of basic geology. I'm going to put that link into another topic. Will link to that topic here, when I track it down.

Moose

From www.evcforum.net/cgi-bin/dm.cgi?action=msg&f=7&t=210&m=13#13 -->www.evcforum.net/cgi-bin/dm.cgi?action=msg&f=7&t=210&m=13#13">http://www.evcforum.net/cgi-bin/dm.cgi?action=msg&f=7&t=210&m=13#13:

Iceage writes: What is always ignored is the simple fact that the bottom layer is often metamorphosed. The A/U at the bottom of Grand Canyon is high grade metamorphic rock - requiring high temperature/pressure/time. The temperature of that massive formation would have to be several hundred degrees!.

I took exception to the above statement (in the Admin mode) but I considered further discussion of it there to bee off-topic.

What is always ignored is the simple fact that the bottom layer is often metamorphosed.

The lower rock of an angular unconformity may or may not be metamorphosed. But if it were to be high grade metamorphosed it would no longer be a bedded sediment. By definition, an unconformity with the lower rocks being high grade metamorphics or intrusives would be a nonconformity.

The A/U at the bottom of Grand Canyon is high grade metamorphic rock

There are two unconformities at the bottom of the Grand Canyon. The lowest one indeed is over high grade metamorphics, and is a nonconformity. The higher (the Great Unconformity) is an angular unconformity. The lower ("angular") rocks of that are at most low grade metamorphics, and I suspect, are unmetamorphosed.

See here for a cross-section.

Moose

Maybe this has been posted in this topic before, but even if, I think it worthy of more exposure.

Found via this topic at Evolution Fairytales.

Moose