Baked fanglomerate

A quick post to share a few images of an outcrop I visited last September out in California’s Owens Valley. This is a spot where alluvial fans coming off the eastern Sierra Nevada were overrun by a basaltic lava flow (Jeff, Kim, Fred, and Kurt for scale):

contact_meta_sub_lavaflow02

The unofficial term for these conglomerates deposited by alluvial fans is “fanglomerate,” and it’s pretty cool to see the contact metamorphism at the top of the fanglomerate. There’s also some weakly-developed columnar jointing in the basalt. Here’s an annotated version, in case the contact wasn’t quite obvious enough:

contact_meta_sub_lavaflow02_anno

Here’s a close up (Doug for scale), showing the orange zone of thermal metamorphism at the top of the fanglomerate as the lava flow above baked the hell out of it:

contact_meta_sub_lavaflow01

Groovy, eh? Where’s your favorite example of contact metamorphism?

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4 Responses

  1. Until I saw this, it was a group of mudstones (Aguja Fm., Terlingua, TX) overlain by some Tertiary volcanics…which bake the muddies from brown to yellow(ish) to the original color of the rock.

    But this is very cool. It reminds me of a good cassarole, with a “cooked to a golden brown” top.

  2. That’s a lovely example, but my favorite example of contact metamorphism is going to have to be from a pluton in Vermont… at least until I finish the figures on the paper I’m writing!

  3. […] was trying to find a nice example of a baked contact so that I could jump on the geomeme that Callan and Silver Fox started earlier this week. I thought about maybe using a skarn contact (I think […]

  4. […] below last summer. What didn’t dawn on me in the field, but jumped right out at me after our recent geomeme of baked contacts, was that it’s also a great example of a baked contact in […]

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