Day #6 of the 2015 Arizona Trip #2 began with having breakfast in Albuquerque with some fellow beer can collectors after the previous day's show (two of whom passed away since then).
The first geology stop of Day #6 was on the western outskirts of Albuquerque, off of I-40, for the quick photos of a portion of the Albuquerque Volcanic Field, in this case, the three southernmost of the volcanoes. [More geology details about this area will be the subject of a future post.] The age estimates for the volcanic field range from 170,000 to 70,000 years ago.
Figure 1.
Sitting atop the probable fissure-erupted basalt flows (left to right) are JA Volcano, Black Volcano, and Vulcan Volcano. The basal (presumed) fissure-erupted flows overlie river terrace deposits.
As I was trying to save time, I got off at Exit 153, Arroyo Vista Blvd North and worked my way through some neighborhoods to get this view.
As I was trying to save time, I got off at Exit 153, Arroyo Vista Blvd North and worked my way through some neighborhoods to get this view.
Figure 2. JA Volcano.
Figure 3. Black Volcano.
As I felt pressed to "get back on the road", I failed to notice that the next exit, Atrisco Vista Blvd. North (Exit 149) would have gotten me much closer to these three volcanoes. (Going back and getting it right is now on my "Bucket List".)
[Admittedly, after I left the El Paso area in April 1991 and moved back to my native Atlanta, other than reading a few Rio Grande Rift field trip guides, with my mind than on finding work in Georgia and tending to my family, I sort of fell behind on New Mexico rift-related volcanics.]
After returning to I-40 West, a few miles later I again left the Interstate at Rio Puerco (Exit 140) to photograph a dissected (by erosion) volcano south of the freeway, as well as a basalt bluff and exposed terrace deposits near the Rio Puerco (seen below).
Figure 5.
I have yet to discover a name for this dissected (eroded) volcano, just east of the Rio Puerco and south of I-40.
Figure 6.
Old Rio Grande terrace deposits adjacent to the Rio Puerco (looking northward). Not sure if the basalt flows to the right overlie more terrace deposits or not.
Figure 7.
A larger "basalt bluff" east of Figure 8 location. Don't know if these and Figure 8 flows are related to the dissected volcano or not.
Figure 8.
I think this was Exit 126, with its Eastern Colorado Plateau Mesozoic exposures.
Figure 9.
Known variously as "Cubero Volcano" or "Flower Mountain"(?), this apparently dissected volcano sits atop presumed Cretaceous sedimentary rocks at Exit 104. This is a view of the southern escarpment facing the Rio San Jose Valley.
[I had some images of the other side of "Cubero Volcano", where I-40 "swings" behind it, but I can't seem to find them.]
The next 7 images are of young basalt flows along the vicinity of McCartys, New Mexico, on the Northside of I-40, with the best exposures between MM 96 and approximately MM 89 (near McBride Road). I may have just pulled off at a "good flat spot" on the right (not an actual exit), perhaps 1 mile West of Exit 96. [Hey, when a Geologist "must" have that photo, we do what we must.]
Figure 10.
Figure 11.
Figure 12.
In the foreground (above), is a wetland hosted within an apparently collapsed lava tube.
Figure 13. Vesicular texture.
Figure 14.
Between the basalt flows in the foreground and the flows capping the mesa in the background, are Mesozoic sedimentary rocks.
Figure 15.
Figure 16.
The McCartys flows are at the extreme northern end of the Zuni-Bandera Volcanic Field. The estimated ages range between 3,200 and 1,250 years old.
Figure 17. "Tachylite"
Tachylite "texture" on the surface of a McCartys flow. Because of the lack of internal structure (as with obsidian), the glossy surface readily decays upon long-term exposure to water. It is a sign of a really young lava flow.
South of the I-40 intersection with East Santa Fe Ave. (Exit 85) is the El Malpais National Monument, certainly a worthy photo stop. I wish I could have stopped and had seen more in the area, but I had a bit of ground to cover that day. (See the planned upcoming "Route 666" and "Shiprock to Aztec" posts.) There were still many geological photos to be taken.
It would be a pleasure to spend 2 or 3 days exploring the Zuni-Bandera Volcanic Field as well as the Mt. Taylor Volcanic Field. Several days of "homework" beforehand would yield more satisfying results.
[I had previously observed the geologic sights along I-40 from the Albuquerque Volcanic Field to the McCartys Basalts in 2003, during a family vacation. I only had a chance to shoot a few photos of the Albuquerque Volcanoes, as we were on our way to the Grand Canyon and then Phoenix.]
Further west on I-40 is more Colorado Plateau strata in the Wingate, NM. The cliff-forming red sandstone is probably the Jurassic Entrada Sandstone. (I tended to notice the cliffs to the north of I-40.)
The "last" noteworthy geologic structure before the Gallup exit is variously called the "Gallup Hogback" or the "Nutria Monocline".
Figure 18.
Secondary Hogbacks, east of main Hogback, south of I-40, dipping westward.
Figure 19.
Western slope of Gallup Hogback, north of I-40.
Figure 20.
The western slope of Gallup Hogback, south of I-40.
References (more to come)
Chronic, H. (1987) Roadside Geology of New Mexico, Mountain Press Publishing Co.
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