Wednesday, April 28, 2010

Lacustrine sediment between Bogus Rim lava and older Bogus lava

The photo below is looking north across Jackson Creek Canyon on river left. The upper lava is good ol' Bogus Rim, the white stuff is probably lacustrine silt. The little wedge of lava upon which the silt lies is what I call the lower Bogus...but may correspond to the Bogus Point lava (?).

Click on the image to enlarge. The wedge that sits conspicuously below the silt has a couple of companion wedges on the canyon wall below where I am standing. It is clearly inset into the older rocks. Note that the higher wedge that is perched on the silts is a small landslide block of the Bogus Rim lava.

Note also how the lacustrine silt grades abruptly upward into bedded gravel. As the image below attests, some of the light colored fines are interbedded with the trib gravels. The Bogus Rim lava is also capped by the gravels in this outcrop.

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