Northern Utah

A few pictures I took earlier this month in northern Utah

 Bear Lake, looking to the east.

 Chokecherry blossoms.

 Cinquefoil flowers near Tony Grove.

 Echo Cliffs in Weber Canyon.

 Tony Grove lake in early July.

 

 Light band of Tintic Quartzite at Willard Canyon sits above gray Precambrian gneiss, schist, granite and pegmatite.

 Paleozoic outcrops at Temple Fork in Logan Canyon.

 Unconformity in Cretaceous rocks in Weber Canyon between younger conglomerate layers on top (flat) over older gently dipping conglomerates.

 Ricks Spring in Logan Canyon.

Flowers under the aspens near Tony Grove.

Moon Rise Over the Wasatch in October

Just a few shots of the full moon as it peaked through the clouds coming up over the mountains.

Views from Ice Cave Peak, Uinta Mountains

These are a few photos taken last week while out mapping along the south flank of the Uinta Mountains. Ice Cave Peak gives a great view of the Whiterocks River valley and the rocks that are exposed along that valley. Late June is a great time to visit because the mountains are so green and the temperatures are pleasant. In the higher mountains, rain clouds form almost every afternoon.

View to southwest from Ice Cave Peak across Whiterocks River valley. On the far side of the river you can see, starting at the far left on the far ridge, gray outcrops of the Pennsylvanian Weber Sandstone, then red outcrops of the Morgan Formation, also Pennsylvanian. At the bottom of the red Morgan cliffs is a thinner gray cliff of Round Valley Limestone, completing the Pennsylvanian outcrops.  The Round Valley Limestone sits above a dark streak of green trees that are growing in the strike valley formed by the soft shale of the Doughnut Formation (Mississippian). Then at the top of the closer ridge, and still dipping off to the left, is a somewhat covered slope (with trees and scrub) of the Humbug Formation sitting atop several ledges with some trees that comprise the Deseret and Madison Limestones, all Mississippian in age. These Mississippian units sit unconformably on a yellow orange unit, called the Red Pine Shale. The Red Pine Shale here appears to be almost horizontal. It is the oldest unit in the photo and is Proterozoic in age. That's probably more geology than you really wanted to know.

Another view to the southwest across Whiterocks River valley.

Looking to the north from Ice Cave Peak to the high rounded peaks of the Uinta Mountains with rain clouds gathering for their afternoon frolic.

A broader view to the northwest.

The storm clouds begin to dump their treasure onto the higher peaks.

Standing on the Mississippian limestones of the Madison Limestone that make up most of the outcrops around Ice Cave Peak and looking south. Below are a couple more shots to the northwest.

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.

The Late Triassic in the southern Uinta Mountains

One of my former graduate students (Paul Jensen) and one of my current graduate students (Skyler May) have worked on these Late Triassic Rocks along the south flank of the Uinta Mountains. They are interesting rocks with interesting sedimentary structures. We traveled out there this week to look at them again.

Panoramic view of one of the ships in the Red Fleet along the south flank of the Uintas. The particular rocks we are studying are the rocks that make up the "deck" of the ship and the red cliff above the lower slope. The lower slope is the Chinle Formation, the red cliff and deck of the ship are the Bell Springs Formation, and the upper lighter red rocks forming the top part of the ship are the Nugget Sandstone.

Rippled sandstone with small clay lumps on the ripples. As the water flowed past the clay lumps, they allowed sand grains to accumulate in their flow "shadow" showing that the water was flowing from the upper left to the lower right across this bed.

This layer of sand was covered by a thin layer of mud that dried out and cracked. The cracks were then filled in with more sand. Fossilized mudcracks are common in the Bell Springs Formation.

The massive red cliff sandstone is almost entirely composed of ripple laminated, very fine sand as seen in this photo. The individual ripple layers are 1-3 cm in thickness with ripple wavelengths typically 2-6 cm. In places, a few mud lumps are found in the sandstone, as seen near the top of this photo and some ripples have thin mud drapes.

Occasionally, small fluid escape tepees, as seen here, can be found in the rippled sandstone. In addition, the sand is pock marked with small burrows and bioturbation, seen here and below.

Color and b&w shot of bioturbated portion of the red sandstone cliff. Here the burrowing has almost completely destroyed the ripples, although some can still be seen in a place or two.

The small white rectangular blades and rosettes seen on this sandstone surface are salt casts: places where salt crystals grew in the sand and then later dissolved away. This layer of sandstone is at the top of the red cliff and forms the first layer of the deck of the Red Fleet ship.

Standing here on the surface with the salt casts is Doug Sprinkel of the Utah Geological Survey. Between Doug's feet and hat are a series of sand layers that lie like the shingles on a roof dipping to the left. These were likely deposited on the point bar of a small river.

Above the point bar deposits are layers with small cross-bed sets. The lower set seen here has been truncated by a second set. The contact between the two sets (a few inches above the hammer handle) is wavy and the first sand deposited into the waves has layering that follows the wavy boundary before the second sand set becomes established.

Here is a close up of the contact described above. The lower cross-bed set truncated along the wavy surface. Then the sand filling in the waves, then a thin crinkly bed with a slightly darker color, and finally the second cross-bed set.

Crinkly beds in these sandstones as seen here in this 2004 photo, may be due to algal growth on the sand shortly after it was deposited.

Cross-bedded sandstones about 0.5 m in thickness are separated by crinkly sandstone layers near the top of the red cliff in the Bell Springs Formation. This photo was taken in 2004.

Here the Bell Springs Formation is exposed in Dinosaur National Monument to the east of the Red Fleet section and the big cliff forming sandstone that was characteristic of the formation at Red Fleet is absent. Photo taken in 2012.

Ron Blakey's paleogeographic map of the Bell Springs Formation time period. According to his map, northeastern Utah would have been part of a broad fluvial plain stretching out to the west from the highland areas of Colorado to the ocean and island arc along the western margin of North America.

Uinta Mountains, South Flank Photos

Ashley Gorge on the south flank of the Uinta Mountains.

Site of a recent landslide on the south flank of the Uinta Mountains. The sediments that were activated in the landslide were deposited by glaciers that scoured these mountains during the last ice age.

View of Whiterocks River valley from Ice Cave Peak on the south flank of the Uinta Mountains. Precambrian through Mesozoic rocks dip here to the south off of the Uinta anticlinorium.

Red colored rocks grading up into gray are the Pennsylvanian Morgan Formation.

View from Ice Cave Peak across Whiterocks River valley. The tan beds capping the ridge above the cliffs is the Mississippian Humbug Formation. The cliffs are composed of the Deseret Limestone and Madison Limestone formations, both Mississippian in age. These Mississippian formations were deposited unconformably on the Proterozoic (Precambrian) Red Pine Shale that has been dated at about 770 million years old. You can read more about this area and other areas of Utah in the "Geologic History of Utah."