Friday, April 10, 2009

Imbricated thoughts on gravel, pt. 2

Now the high gravels. Maybe I haven't shared this with the entire group, but there are very, very sparse gravels in very few locations near the western edge of the Bogus Rim lava (Qbbr). Cooper and I spotted some in October 07 and I saw them again in Oct 08 and got a precise GPS reading on them of 1194 m. This is the level of the highest gravels upstream (skirting Little Owyhee Butte), but I haven't gotten a gps reading on them to really pin it down yet (May trip). Thus, these most likely represent the effect of damming by the Qbbr. The edge elevation of the Qbbr approaches 1204 m at the narrowest gap between it and the west edge of the Gorge at Iron Point. Note that the copious (6 m thick) volcanic-clast dominated overflow gravel appears downstream from the likley point of blockage at an elevation of 1160 to 1140. Suggests clearwater pour-over of the blockage to me.

Other high gravel elevations of note include the gravels on the Ice-Axe (1148 m), the low Rim Gravels on the tip of Bogus Point ( 1114 m), and the lone gravel deposit on the West Crater Kipuka (1050 m). More on them later.

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