Out of the Valley of Death: Explorations in Red Rock Canyon

The next stop on our way to Death Valley National Park was one of the most ideal locations for learning the basics of stratigraphy to be found anywhere: Red Rock Canyon State Park in the El Paso Mountains along the Garlock Fault. The park protects exposures of the Miocene deposits of the Dove Springs formation (formerly the Ricardo formation), aged at about 8-12 million years. The formation of conglomerate, sandstone and claystone was laid down in alluvial fans, floodplains, and lakes in a semi-arid savanna environment. The region was home to a vast array of grazing mammals and predators, including extinct elephants, rhinos, three-toed horses, giraffe-like camels, saber-toothed cats, and bone-crushing dogs as well as smaller animals like ancestral skunks, martens, alligator lizards, rodents, and shrews. (follow the links to descriptions of each type of animal on the Los Angeles Natural History Museum website).

The park has stunning exposures of the sedimentary and volcanic rocks that illustrate many of the basic principles of stratigraphy (superposition, original horizontality, lateral continuity, and cross-cutting relationships). I worked with the students to observe and identify the rocks, and to work out a sequence of events that led to the formation of the exposures. And then I turned them loose to produce a rudimentary map of the geology of the area around the beautiful red cliffs.

It was February, and the sun was blazing! The temperature topped out at about 90 degrees. In a sense it was quite pleasant, especially compared to the frigid conditions back in the eastern United States, but it was also a reminder that we never had winter this year. There has been so little rain that there are parts of the Central Valley that have received less precipitation than Death Valley. It was a bit disturbing to realize how dry conditions are across the state.

Red Rock Canyon State Park has been the setting for numerous movies over the years, including old-time westerns, but my favorite movie scene was the opening sequence of Jurassic Park, where the protagonists were excavating velociraptors from Snakewater Creek or some such place in Montana. I sometimes find myself thinking "your cute little velociraptors wouldn't stand a chance against our bone-crushing dogs and sabertooth cats!".

Strangers in a Strange Land: Discerning the Story in the Rocks at Red Rocks

In the last post, we were introduced to the basic rules of stratigraphy as they stood exposed in the spectacular cliff faces of Red Rock Canyon State Park in California's Mojave Desert. A classroom chalk board can only provide a cartoon of these concepts, so there is nothing quite like being there and laying your hands on these records of the Earth's past. We were on the road with 30 community college students, most of whom were seeing this landscape for the first time. After an introduction to the stratigraphic principles of superposition, original horizontality, lateral continuity, and cross-cutting relationships, I sent the students forth to test their newly acquired knowledge against the cliffs above. We weren't quite to the point where we could do geologic mapping, but I provided them with an outlined photo of the scene (below) and asked them to describe the rocks, and identify any structures.

This is one of the finest moments a teacher gets to have. I wasn't teaching at all; my students were teaching themselves. They were crawling up and down the slopes, taking notes, and discussing what they were seeing. OK, it's true there was no cell phone service, so what else were they gonna do?

The layers were readily labeled on the basis of color alone, and most of the students developed some version of the picture below (click to enlarge):

I climbed up the slopes to have a closer look at some the exposures. What happened here 8-12 million years ago? The red and brown layers (A, C, and D) proved to be arkosic sandstones, the kind of thing one might find in river channels and alluvial fans in a region of relatively high relief (lots of rapid erosion). Some of the finer-grained brown sediments formed in river floodplains. These rocks had clearly formed on land.

The white layers (B) with puffy deposits that kind of looked like ground hamburger were ash deposits, evidence of regional volcanic activity. The ancient environment here was beginning to look a little bit dangerous!

The upper cliffs and slopes (layer F), proved to be evidence of the greatest geological violence possible, a rhyolitic tuff breccia. The rock formed when hot ash rolled over the landscape, picking up gravel and debris and incorporating the material in the nearly molten tuff deposit. This was no place to be hanging about...but plenty of animals did. The layers of the Dove Springs Formation are a treasure trove of Miocene fossils, one of richest beds found in California (or pretty much anywhere, really).

The animals found in the sedimentary sequences here include include extinct elephants, rhinos, three-toed horses, giraffe-like camels, saber-toothed cats, and bone-crushing dogs as well as smaller animals like ancestral skunks, martens, alligator lizards, rodents, and shrews. (follow the links to descriptions of each type of animal on the Los Angeles Natural History Museum website).

Faults in a cartoon drawing on a chalkboard are a lot easier to see than most faults in the real world. A number of the students noticed how the layers ended and identified the fault that caused them to be offset (see the arrows in the diagram above). I headed up to take a closer look at the fault surface...because I think everyone should know their faults...

We only had a few precious days to see as much as possible on this trip, so we couldn't spend as much time at Red Rock Canyon as we would have liked. A fair number of geology programs do mapping exercises here, spending several days on site. It sounds like fun...if it isn't too hot. It was time for us to move on, so we loaded up the vans and drove north on Highway 14 towards our next destination at the south end of the Owens Valley. That will be part of the next post.

If postings seem sparse in the coming week, it would be because we are about to embark on part two of our Strangers in a Strange Land journey: an exploration of the Mojave Scenic Preserve in the desert south of Death Valley. We're attending the spring meeting of the Far Western Section of the National Association of Geoscience Teachers at the Desert Research Center at Zzyzx. Hope to see a few of you there!