Sunday, February 16, 2014

Geo 730: Feb. 16, Day 412: Diatomite Interbed?

Though I didn't recognize or check it carefully at the time, that white layer running through the middle has the look of diatomite. If that is in fact the case, it would be a strong indicator that these tuffs were deposited in a lacustrine environment. Nothing for scale in the photo, but if you refer to yesterday's post, you can see that shaded fracture over on the left is about one Dana-height.

Photo unmodified. August 19, 2011.


Lyle said...

You say the scene is between Lakeview and Adel, If you look there are several shallow natural lakes in the area, such as Hart Lake, (5 foot deep now, but likely deeper during the wetter past. Given that one had eruptions thru lakes further West (Fort Rock), if the flows are about the same age lacastrine deposits are quite likley.

Lockwood said...

This section is much older than Pleistocene pluvial lakes, even older than Basin and Range structure- this would have been prior to eruptions of Columbia River Basalt. Don't know of any relationship between those eruptions and these lighter, more felsic eruptions, so don't mean to imply there is one.