16 February 2011

Outcrops of the LaHood Conglomerate

Posted by Callan Bentley

Remember the LaHood Conglomerate?

Here’s a few field photos of my Rockies class visiting it last July:

Amphibolite clast:

Marble clast:

I love how well-rounded these clasts can be — like eggs.

When these grains were loose cobbles, tumbling down into the Belt Sea, the Earth was only 3 to 3.5 billion years old. The rivers which carried them downhill flowed past a landscape devoid of plants and animals. Since then, they have been locked away underground, fused to their neighbors, and only recently brought to the surface and exposed for the eyes of curious hominids like us. What a wild journey…

A few shear bands cut across the LaHood in the outcrops on the north side of the Jefferson River Canyon, and slickensides are visible:

Nice place to check out a cool geologic unit.