Friday, April 10, 2009

Imbricated thoughts on gravel, pt. 1

Have lately been thinking about gravel deposits along the Owyhee. Using the LiDAR data, it is possible to rapidly extract precise elevation data from any point within the swath. This allows for a quick appraisal of the potential significance of the positions of various gravel deposits. In this image, I have highlighted some interesting spots. Of particular interest here are the gravels at the 993-995 m level ('perimeter gravels'). These are roughly concordant with the height of the west edge of the the West Crater flow and probably define the position of the first established channel of the river on its way through the lava. These surfaces stand well above the highest gravels at Dogleg, but that gradient is controlled by the gradient of the lava flow. What of the large difference between the elevation of the perimeter gravels and the next level down at Dogleg...a 33 m difference over only 3 km? Steep.

Also of note in the figure are the gravel deposits in the 1017-1025 m range (need to step on these sites before too long). These deposits must pre-date the West Crater flow and would have flanked the paleochannel that it followed. I was pleased to notice that the 1017 m gravel coincides with a prominent scarp-ish feature that is fairly obvious on the east side of the valley. Suggestive of gooey paleovalley margin for sure.

More posts on other gravel issues to come. Feel free to participate.

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