Roxborough State Park and Environs

On to Roxborough State Park which showcases four important Colorado geological formations. Starting from youngest to oldest they are the Dakota Sandstone, the Lykins Formation, the Lyons Sandstone and the Fountain Formation. A good cross section is found on this page.

Here are a couple pictures of Dakota Sandstone, the first layer in the famous Front Range hogback. Notice in this first picture the oak thickets and juniper on the flank of the hogback. I'm not sure why the plants prefer this environment on the Dakota, but this phenomena seems to be consistent along the Front Range.

The Dakota sandstone is beach sand, and often has ripple marks, and I think the source for the sand was the ancestral Rockies, as massive rivers poured out of them and eroded them away. Dakota Sandstone was formed during the age of Dinosaurs, and so fossils are relatively abundant here. This part of Colorado was a giant shallow inland sea at the time when the sand was deposited.

It was then uplifted during the Laramide Orogeny, which is a technical way of naming the time when the mountains we have today in Colorado were first created. All of these rocks here in the park form the limb of a syncline that dips to the east.

Next over is the Lykins and the Morrison Formation. The Lykins formation is just by the parking lot, and is composed of colonies of fossilized blue-green algae, probably similar to the health food supplement. These fossils are called stromatolites, and they form thin beds in the rock.

During the time when the Lykins Formation was formed, Colorado looked like Iraq, an area of shallow coastal mud flats and arid low lying inland areas. I didn't get a good photo of the Lykins, so I will offer you this one instead from the website of the Denver Museum of Nature and Science. Click on Lykins to see what the stromatolite layers look like. Here's an even better one.

Here in Roxborough, the Morrison Formation supports a healthy grass population, and isn't easily seen. I think the Morrison Formation is underneath this meadow here, as shown in the photo above.

The Lyons sandstone has grains that are more rounded compared to the Fountain Formation. Supposedly Ponderosa Pine and Kinniknnik are common here. This is just behind the upper parking lot.

Lyons Sandstone was formed during a time when the area was covered by coastal sand dunes but still had major rivers flowing through, perhaps like Egypt with the Nile or Iraq with Euphrates/Tigris system.

The Fountain Formation is easily identified by the relatively large, sharp grains of sandstone mixed with pebbles of quartz and feldspar. Also unique are the lichens that seem to prefer it as a substrate, shown in the second photo.

During the formation of the Fountain Formation, there was a lot of erosion from rivers that flowed out of the Ancestral Rockies, the mountain range that was here before the Rockies we know of.

Directions (from Highway 85/Louviers):

32.5 take ramp to Titan Parkway. Go west. Stay on road towards Roxborough (follow signs)

39.2 Dakota hogback approaches.

39.6 Road goes through Dakota Sandstone.

42.1 Roxborough State Park.