Just outside of Abiquiu, before steep climb to Abiquiu Dam and Chama River Overlook, and right before “Red Rocks” roadside marker on right side of road, is forest road and an arroyo that goes to Copper Canyon on your right. Kempter says that Copper Canyon is in a little ways and he hikes up the black dike on the right to get a good view of Copper Canyon--there is no trail up the dike--which he describes as an expansive canyon.
Red rocks on way to Abiquiu Dam, off US 84, are pre dinosaur. CO Plateau rose in elevation but very stable--didn’t rift or form mountains--maybe because the sediments are so thick.
230 mya, NM at sea level. Rivers, etc., deposited sediments, including Entrada Formation (fossilized sand dunes) and ocean deposits. 70 mya North American and Farallon plates collided in Pacific and NM rises above sea level, raising sedimentary layers and then they are eroded over time. Rocky Mountains formed during intense uplift 70-40 mya. Then, last 40 my, Basin and Range pulling apart and extension occurs with a north south trending lineation. Extension of crust allows magma from mantle to find its way to the surface. CO Plateau uplifted but not much deformation. San Juan Mountains are the north boundary of the CO Plateau. Mesa de Abiquiu is another name for the long, dark mesa called Black Mesa. Ojo Caliente sandstone is another fossilized sand dune.
Abiquiu Formation was the earliest deposit in the Rio Grande Rift and it is mainly pumice and ash washed down from the Taos Volcanic Field (may also be called the Latir Volcanic Field). It is 20-30 my old. The surface of the cliff above the Rio Chama at the roadside Overlook is Paleo sandstone. Cerrito de la Ventana is the dark dike that crosses US 84.
We took CR 155 to Plaza Blanca or White Place, which Georgia O’Keeffe has painted. We passed Helen Hunt’s, of Hunt’s Ketchup fame (I coined The Lycopene Queen), and Marsha Mason’s ranches. Marsha Mason grows lavender. Abiquiu Formation is very silica rich and hence its white color. Ojo Caliente sandstone is 12 to 9 my old. CR 155 is washboardy. Kempter pointed out CR 156, off of CR 155, and said it leads to Shirley McLaine’s property and also to a piece of property that he co-owns and would like to build a 1000 square foot dwelling on one day.
Sierra Negra is capped by 6 my old basalt and that is why it has not eroded down--same with Mesa de Abiquiu or Black Mesa. Lots of erosion occurred between Sierra Negra and the mesas to the west and Polvadera. Faulting and erosion makes the CO Plateau landscape look complex but underneath are all the broad, formerly continuous layers of the CO Plateau.
After we parked at Plaza Blanca (parking and hiking here graciously allowed by the Dar Al Islam Mosque), we met some hikers coming back who said that they found a small labyrinth but we didn’t stumble across it in our walk.
It is so elemental in Plaza Blanca with the hard-baked, glinting soil and the rock and boulder littered landscape, all set off by the whiteness of the place. Kempter pointed to the upper levels of the Abiquiu Formation to a layer of big boulders and told us that was a former river level. The whiter, more laminated layers of the fantastic turrets in Plaza Blanca are flood sheet deposits of the Abiquiu Formation. Ojo Caliente sandstone is deposited on the Abiquiu Formation. Also, the area has some young, Quaternary sediments (orange) from 60,000 years ago that redeposited over the Abiquiu Formation after the Ojo Caliente and El Rito Formations eroded away. Some of the boulders, large and small, in the present day channels, washed down from the Tusas Mountains--Ortega Quartzite. The arroyo with pink sand is from the Quaternary deposits of 60,000 years ago (although they look orange when viewed from afar in place on the mesa tops.) Kempter says that these 60,000 year old Quaternary deposits were basically from the ancestral Chama River. Chunks of black basalt on the modern day surface are from the black dike to the north of Plaza Blanca.
Attending these field trips and listening to Kempter explain the scenery is like seeing Geology Revealed!! Kempter says that 500 mya, this area was above sea level, 300 mya it was below sea level and the ocean came into this area. By the Cretaceous, the sea had come down from the Alberta area and up from the Gulf of Mexico and that essentially the land that is now the United States formed 2 islands. From 65 mya, the land was always above sea level and the ocean had disappeared from this area. Volcanism didn’t begin until 40 mya. In all that time, a lot of layers have eroded away. The Chama El Rito formation originated from the Sangres. The Ojo Caliente layer was aeolian. Before the layers eroded away, the whole area was once as high as Sierra Negra.
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