Between Dixon and Picuris

[I originally wrote this in October 2011, but never posted this series on the local geology. The pictures are still worth seeing.]

Now that I have a new camera I have to test it.

My usual method for day tripping has been to look at the map, find something that looks interesting, load the ice chest, and start driving.

There is nothing that can repeat the absolute surprise you feel when you come upon something like the Abiquiu Dam when you’re not expecting it and nothing you want to do to deaden that heart-stopping awe, that sense of unity with all the explorers from the stone age to the present who’ve been there before.

When I get home, I start to read about the place I’ve just been. Then when I go back, I have some better ideas what to look for and some idea about where it’s safe to pull off the road.

Saturday, I took the new camera back to that road beyond Dixon where I had problems with my tires earlier this summer.

After NM 75 leaves Dixon, it feels very much like a typical mountain road with the Rio Embudo on the right side, an occasional gorge coming down from the left, and continually open V’s as the road climbs towards the Sangre de Cristo south of the Picuris mountains. The trees are all still juniper, but closer together than they were below.

Then I came to a section where raw rock was exposed, standing on edge. It looked like shale at the Rio Grande end, then layers of sandstone. However, they seemed so weathered they had no distinct colors, and I’m not sure I even know what shale looks like, other than it’s gray.

My first thought was, why on earth did anyone go to the expense of blasting a road through here. This is New Mexico, where they didn’t widen the road to Los Alamos until after I moved here. Route 75 was described as "a graded dirt road" in the 1930’s WPA Guide when the road that came up from Chimayó through Truches and Las Trampas could get you to Picurus pueblo and Peñasco.

I spent yesterday learning absolutely nothing.

The Española Basin, which tilts west down to the Rio Grande, ends at Velarde. The San Luis Basin, which tilts east, begins farther north. Between the two lies a diagonal belt of disruption that goes from the Picuris mountains to the northeast through the Embudo Fault across the peninsula between the Chama and Rio Grande rivers towards the opening into Santa Clara Canyon.

I presume I was somewhere on the edge of that fault, but can get no confirmation. Is this what a fault looks like?

I did pick up a piece of gray fallen rock to take to the Rock Queen to see if she knows if it’s shale or not. It is sedimentary, contains some quartz and mica, and crumbles a bit.