Tuesday, May 9, 2017

Pine Valley and Carlin Canyon Squiggles

What is this?!!1?1!?
It all started when I was trying to find out what rock formations and rock types I was seeing while making the long trip to work and back out near Elko. Looking around, I found this geologic map (Smith and Ketner, 1972), which even had a kmz file so I could load it directly into Google Earth—and so I did.

There I was, fiddling around looking at rock types and contacts. The map wasn't easy to look at in Google Earth (GE) because it was in black and white, so I started drawing the contacts on to GE, and lo and behold, the contacts were all screwy. It took me a while to figure out that the kmz file didn't register properly on GE; perhaps it didn't have a NAD27 to WGS84 correction or some such thing. I plotted a few static, known localities that I could identify on both the map and GE and determined that everything was off in a northwesterly direction (map to GE) by about 1500 to 1900 feet.
The map and GE locations of a small dam and the ghost town of Palisade.
I thought Palisade looked occupied the last time MOH and I visited, which was in the summer of 2013 (it was the only time either one of us has ever been there), so I was surprised to find it listed by search engines as a ghost town, rather than as a "census-designated area."

I was frustrated by this mis-registration of the map on Google Earth—what is the point of a kmz file of a map, after all, other than to be able to use it easily and forthwith—so I continued drawing on a few contacts in the area I was initially interested in: the area near the small (or old) dam shown above.

Oh look, there's a huge landslide or slump block mapped! I always find these fascinating, so I zoomed in on that, after figuring out that, indeed, I had stopped along the road once—in a pullout near the dam—and had found ash-flow tuff in the roadcut, just like I had remembered! (Although in this case, it was probably slumped or slid ash-flow tuff rather than 100%-in-place ash-flow tuff.)

And then I remembered that I'd always thought there was a pediment in Pine Valley, and recent drives through the area seemed to confirm that, though I wasn't sure if it would be considered a pediment because it seemed to be formed on Quaternary-Tertiary sediments. A couple of old reports (Regnier, 1960 and Eakin, 1961) confirmed that a pediment (or two, even!) had been identified in the valley—and that's when I went nuts with my GE squiggles, and started drawing in all the Quaternary gravels so I could better visualize the valley's geomorphology. That resulted in the squiggles seen in the first image: an incompletely labeled map with missing contacts but with pediment gravels outlined in great detail.

Then, I moved up to Carlin Canyon and—unsuccessfully in my opinion—tried to plot the unconformity contact. (See Ron Schott's Gigapan of the Carlin Canyon unconformity here.) And then I moved to the Carlin Formation east of the Carlin Tunnels. The Carlin Formation forms golden-brown outcrops and cliffs right alongside the highway, great examples of tafoni weathering, so close but inaccessible. I wanted to see if any roads led into the area, and there are none, but I drew some squiggles for the geology in that area anyway, and then moved south of the highway to draw in a few more areas of the Carlin Formation, because once I've started on something, it's hard to get me to stop.
An expanded version of my GE squiggles.
And that's what it all looks like at this point. Hopefully I'll be able to grab a few great photos of the pediment surfaces later this summer, when I move back into the area for another round of work way out there.

By the way, the completed geologic map (Smith and Ketner, 1978), published in color, can be viewed here (but without a kmz file).


jusTodd said...

looks like that KMZ was done at 1:25,000 ... not sure what scale you were viewing, but it is not much good any closer. :)

Silver Fox said...

The kmz's usually adjust to whatever scale they are viewed in on Google Earth, so I don't think that should matter any. That is, all the USGS kmz files I've used before have been just fine at any zoom on Google Earth. (Although I might not always agree with all the contacts, they have always overlaid the topography exactly before this.)