Some Features on the Nugget/Navajo Sandstone, San Rafael Swell, Utah

A dinosaur track in the top of the Jurassic Nugget Sandstone (also called the Navajo Sandstone) on the San Rafael Swell, Utah. This was located in the bottom of a wash and has since been covered or eroded away. The middle toe must have been loaded with mud as the dinosaur stepped into this spot.

An interesting structure on the same surface as the dino print above. I thought this might be a burrow of some type, but my friend and colleague, Dr. Steven Hasiotis, who is an expert in trace fossils was unconvinced. We decided it must be some kind of fluid "pebble dike" like structure, where the solid sandstone was broken up and then redeposited as water or other fluids moved through the rock.

Also found on the Nugget Sandstone on the San Rafael Swell, this picture shows the individual avalanche deposits of sand that tumbled down the dune face before this became a rock.

Here is another view of this dune in the Nugget Sandstone. You can see the surface with the avalanche deposits in the foreground and in the background a lower face of the dune that is covered with ripples.

In one spot on this petrified dune, there were these small circle-like structures (see piece of chalk for scale). I am not sure what caused them.

Just below the dunes shown above, the sandstone is ribbed with giant polygonal cracks filled with sandstone that is slightly more resistant to erosion. My colleague, Ron Blakey at Univ. of Northern Arizona has published several papers on these structures.

One of the most interesting features to me found on a couple of the dune faces were these  triangular and rectangular structures. They represent salt or gypsum that crystallized in the sand and, after leaving an impression, dissolved away.

Another probable dinosaur undertrack on the top of the Nugget.

Along the edge of the wash, a series of these possible dino tracks seem to form a trackway.

A Few Photos from the Archives

Thistle Landslide in Spanish Fork Canyon, Utah in the spring of 2000.

Light green Jurassic Curtis Formation atop the brown stripes of the Summerville Formation on the San Rafael Swell, Utah

Light greenish gray beds of the Tertiary Green River Formation overlying red beds of the Wasatch Formation in southwestern Wyoming.

Scenic San Rafael Swell, Utah.

Spring flowers on the San Rafael Swell, Utah.

Light green beds of the Cretaceous Cedar Mountain Formation above the purples and reds of the Jurassic Morrison Formation near the Dalton Wells dinosaur quarry north of Moab, Utah.

Red blossoms bloom on a cactus in springtime on the San Rafael Swell, Utah.

In this photo, the brick red Triassic Moenkopi Formation is at the base of the cliff. It is overlain by a greenish and purplish slope of the Triassic Chinle Formation (with the prominent Black Ledge Member near the top of this formation). At the top of the cliff is the massive sandstone cliff of the Triassic (and perhaps partly Jurassic) Wingate Sandstone.

Rock art in the Tertiary Green River Formation of Wyoming. This circular feature is call a concretion.

Sandstones and coal beds of the Cretaceous Blackhawk Formation just west of Helper, Utah.

Vineyards stretch across the Sonoma Valley, California in the spring of 2000.

Clear Lake, California located north of the Sonoma Valley.