Archive for July, 2010

A Great Unconformity

July 16th, 2010

I almost forgot our quick side trip at the end of the day. With the Green River Formation behind us (literally, in this photo), we turned to view a fantastic example of an angular unconformity here in central Utah. Although there are several significant unconformities in the area, this unconformity is probably my favorite, because it shows paleotopography as you follow it regionally from west to east.

The photo above shows the unconformity that places the Paleogene Colton Formation on top of the vertical Jurassic Twist Gulch Formation.

The photo above shows the unconformity that places the Paleogene Colton Formation on top of the vertical Jurassic Twist Gulch Formation.

If We Only Had a Rock Saw in the Field…

July 16th, 2010

Today was our final day on one of the Green River cuestas. We decided to top it off by working a quite extensive section of the formation with a great climb to reach the stromatolites. However, the climb was completely worth it, because the view of the Valley was amazing.

The photo shows one of the smaller stromatolites that we encountered today.

The photo shows one of the smaller stromatolites that we encountered today.

Some of the stromatolitic or thrombolitic structures that are within the Green River are quite large. In the photo above, there are thin laminations at the very top of this structure, which are possibly a result of an algal mat. Other structures in this more massive bed are approximately 2 feet thick and might be stromatolites or thrombolites or...???...It is just too bad that we didn't have a rock saw in the field. If I only had a saw to see these features in cross-section. Don't worry, though, we have about 500 pounds of stromatolites coming back to Scovel Hall!!

Some of the stromatolitic or thrombolitic structures that are within the Green River are quite large. In the photo above, there are thin laminations at the very top of this structure, which are possibly a result of an algal mat. Other structures in this more massive bed are approximately 2 feet thick and might be stromatolites or thrombolites or...???...It is just too bad that we didn't have a rock saw in the field. If I only had a saw to see these features in cross-section. Don't worry, though, we have about 500 pounds of stromatolites coming back to Scovel Hall!!

The fabric on some of the beds was amazing. We have really come to appreciate the various textures that can be seen within stromatolitic beds.

The fabric on some of the beds was amazing. We have really come to appreciate the various textures that can be seen within stromatolitic beds.

After we completed our cuesta stratigraphy, we drove to Soldier Canyon to admire the exposures of the Green River in all of its glory. Elizabeth, who has really taken to the west, decided to do a little house hunting. There were several of these dwellings within the formation, but this one seemed to be the most spacious. You should see the interior design!! Elizabeth just loved what they've done with the decor.

After we completed our cuesta stratigraphy, we drove to Soldier Canyon to admire the exposures of the Green River in all of its glory. Elizabeth, who has really taken to the west, decided to do a little house hunting. There were several of these dwellings within the formation, but this one seemed to be the most spacious. You should see the interior design!! Elizabeth just loved what they've done with the decor.

To the Victor Goes the Spoils…

July 16th, 2010

The Utah gang was back at it in the Green River Formation, which is exposed in one of the cuestas in the Sanpete Valley. It was a wonderful 100 degrees by midafternoon, and I think that even the fossil ostracodes were beginning to sweat. Our goal today was to investigate a couple of quarries, and first thing in the morning, Jesse found an very intriguing stromatolite layer about 5 feet above the top of our first quarry. There were smaller stromatolites, which provided a base for the much larger stromatolites.

This photo highlights the size differences between the stromatolites that were found within the same interval in our first quarry. A penny in the photo is used for scale.

This photo highlights the size differences between the stromatolites that were found within the same interval in our first quarry. A penny in the photo is used for scale.

Elizabeth noticed that several centimeters of the surface of some stromatolites had a very interesting tube-like fabric. We cannot wait to get this back to the Wooster lab for some additional work to identify these structures (and for some expert opinions from Dr. Wilson!!).

Elizabeth noticed that several centimeters of the surface of some stromatolites had a very interesting tube-like fabric. We cannot wait to get this back to the Wooster lab for some additional work to identify these structures (and for some expert opinions from Dr. Wilson!!).

We were able to look at three different quarries within the cuesta. While Elizabeth and I were working in quarry #2, Jesse went to one of the other cuestas in the Sanpete Valley for some recon work on the quality of the stromatolites there. The Black Hill quarry that Jesse visited is enormous, but he reported back that the quantity of stromatolites was disappointing. So, we hiked to quarry #3, where Elizabeth attracted yet another scorpion. (As I have learned, Elizabeth seems to have a real gift for attracting scorpions, wasps, huge bees, and fire ants.)

Quarry #3 was great!! Although we were supposed to be looking for mudcracks, our attention strayed. First, we were fascinated that the small scorpion seemed to be very angry at Elizabeth for flipping over a stromatolite (its home), and seemed to chase her. But, then things got very interesting…The scorpion rested near a small bush, and before you knew it, a lizard was stalking the scorpion. In a flash of an eye, we watched the lizard grab the scorpion and run away with the prize, all the while capturing everything with the camera. National Geographic, here I come!!

Notice the small lizard in the top center of the photo. This was the instant that the lizard grabbed the scorpion from between the small bush. Things in the photo are a little fuzzy, because the lizard moved so quickly.

Notice the small lizard in the top center of the photo. This was the instant that the lizard grabbed the scorpion from between the small bush. Things in the photo are a little fuzzy, because the lizard moved so quickly.

Our fierce lizard scrambled to a nearby rock to celebrate its find. Sadly, the scorpion had no chance.

Our fierce lizard scrambled to a nearby rock to celebrate its find. Sadly, the scorpion had no chance.

The utility of trace fossils

July 16th, 2010

LOGAN, UTAH–Today we hiked north of Tony Grove Lake in Logan Canyon to explore an Ordovician sequence of rocks. The most interesting unit (to my surprise) was the Swan Peak Quartzite, an orange-brown unit at the base of a white dolomite and gray limestone. It weathers in sharp edges and large blocks tumbled down the slopes. Quartzite began as a quartzose sandstone which was metamorphosed into a rock where the silica cement is as hard as the quartz grains. Most fossils are destroyed in this metamorphosis, along with almost all sedimentary features, so I didn’t expect to see much in the Swan Peak.

Outcrop of the Swan Peak Quartzite (Ordovician) north of Tony Grove Lake, Utah. This photograph was taken facing north at N41° 54.198', W 111° 38.72'.

Google Earth image of the Swan Peak Quartzite exposure. The green arrow is the location from where the outcrop photograph above was taken. The stepped nature of the rocks is easily visible in the middle of the image.

The Swan Peak Quartzite is exposed here as a series of large steps looking something like a side of an eroded Egyptian pyramid. Why does it erode into this kind of stairway instead of one large block? A close examination of the rock surfaces revealed trace fossils were preserved — the kind of fossils which could be clues to the character of this formation.

Horizontal burrow systems preserved in remnant bedding planes of the Swan Peak Quartzite. These traces give the rock its local name of "Fucoidal Quartzite". Fucoidal is an old word for trace fossils.

Vertical burrow systems (Skolithos) exposed on vertical faces of the Swan Peak Quartzite.

It appears that the step surfaces have horizontal burrow systems, and the “risers” have vertical burrows (Skolithos). There is an alternation of beds with horizontal burrows and beds with vertical burrows through the Swan Peak Quartzite. The horizontally-burrowed units are less resistant than the vertically-burrowed units, so this alternation produces the stepped erosion pattern.

My hypothesis is that the horizontal burrows represent slightly deeper water than the vertical burrows, based on the distribution to such burrow systems in other formations and in today’s oceans. The alternation between the two trace fossil types may thus show fluctuating sea levels as the Swan Peak sediments were deposited way back in the Ordovician.

So, this unpromising rock may indeed be providing clues to its ancient depositional environment through the trace fossils it contains.

Ancient shorelines

July 16th, 2010

LOGAN, UTAH–The Wooster geology team currently in central Utah pointed out in the distance Pahvant Butte which has a set of relict shorelines from the famous — and immense — Lake Bonneville. In the spirit of sharing common field experiences between Wooster geologists this summer, we have Bonneville shorelines up here in northern Utah as well. This pluvial lake was extraordinarily large, filling a good portion of the Great Basin between 32,000 and 14,500 years ago. Its shores were energetic with strong waves pounding away at the confining mountain slopes and forming wave-cut platforms which extended inland hundreds of meters in some places. The area around Logan, Utah, has especially well developed Bonneville shoreline platforms.

Looking west at the Utah State University campus in Logan sitting on a Lake Bonneville wave-cut platform. In the background are the Wellsville Mountains, with the Cache Valley in between.

Wave-cut platforms (or terraces) on the flank of the Bear River Range in Logan, Utah. The oldest levels are the highest because they have eroded away previous shorelines. The lower platforms represent decreasing lake levels over time.

The Great Salt Lake of Utah is a remnant of the once vast Lake Bonneville. Tomorrow I hope to see where the lake catastrophically drained about 14,500 years ago (the Bonneville Flood).

Hey Icelandic Researchers, We’ve Got Some Basalt, Too!!

July 15th, 2010

After many successful field days in sedimentary strata, yesterday we had a day of exploration. We traveled with the Ohio State field camp to Fillmore, Utah, to investigate the Black Rock Desert. Specifically, we spent our time in the Ice Springs Volcanic Field, which provides the youngest volcanic activity in the Black Rock Desert (~600 years old).

We thought that the Icelandic Team would be especially interested in some of our photos, since basalt seems to be near and dear to their hearts.

Jesse Davenport, studious as ever, is listening intently to a lecture on the Ice Springs Volcanic Field. The rough, brecciated aa of the field is behind him.

Jesse Davenport, studious as ever, is listening intently to a lecture on the Ice Springs Volcanic Field. The rough, brecciated aa of the field is behind him.

Elyssa Krivicich (left, '09) and Elizabeth Deering (right) proudly display the Utah basalt. The Red Dome cinder cone is in the background. Hey Dr. Pollock and Becky Alcorn (our Icelandic Team)...do you like it?

Elyssa Krivicich (left, '09) and Elizabeth Deering (right) proudly display the Utah basalt. The Red Dome cinder cone is in the background. Hey Dr. Pollock and Becky Alcorn (our Icelandic Team)...do you like it?

This is a photo of a cross-section through the Red Dome cinder cone, which is quarried for landscaping purposes. Take a look at the pronounced bedding that is due to successive pulses of air-fall deposits. We collected volcanic blocks and bombs both at the base of the cinder cone and then at the very top.

This is a photo of a cross-section through the Red Dome cinder cone, which is quarried for landscaping purposes. Take a look at the pronounced bedding that is due to successive pulses of air-fall deposits. We collected volcanic blocks and bombs both at the base of the cinder cone and then at the very top.

The view from the top of the Red Dome cinder cone is amazing. You can see a smaller cinder cone nearby. In the distance, you can see Pahvant Butte. If you look close enough, the ancient shorelines of Lake Bonneville are exposed at the base of Pahvant Butte.

The view from the top of the Red Dome cinder cone is amazing. You can see a smaller cinder cone nearby. In the distance, you can see Pahvant Butte. If you look close enough, the ancient shorelines of Lake Bonneville are exposed at the base of Pahvant Butte.

Cutting through the Paleozoic in northern Utah

July 15th, 2010

LOGAN, UTAH–Logan Canyon cuts perpendicularly through the Bear River Range in Cache County, northern Utah. It neatly dissects a complex section of Paleozoic sedimentary rocks in the Logan-Huntsville Allochthon noted in my last post. Conveniently, US Highway 89 runs through the length of the canyon providing spectacular views of the quartzites, dolomites and limestones.

The mouth of Logan Canyon as viewed from Logan, Utah.

After exiting the canyon in the east, Highway 89 meets a most unusual body of water with a prosaic name: Bear Lake. Running north-south across the Utah-Idaho border, Bear Lake is one of the oldest existing lakes in North America. Studies of its sediments show the lake has existed for at least 220,000 years, and maybe more. Its water is strangely blue because it contains lots of dissolved calcium carbonate from the surrounding limestone mountains in its watershed. The lake was formed by tectonic processes, sitting now in a half-graben which is still active. Its human history is interesting too — in the early 19th Century it was a gathering point for mountain men, including Jim Bridger and my hero Jedediah Smith.

Bear Lake viewed from the west in the Bear River Range.

Let the Work Begin

July 15th, 2010

Guest blogger: Becky Alcorn

Today was our first day of field work in Undirlithar quarry. Although a lot of the quarry has been filled in in the last year, we had a very successful day and found three dikes that can be used in my IS. We began mapping the south wall that will be the focus of my IS and collected several samples for future analysis when we return to Wooster. We’re even returning to the quarry later tonight to continue our work since the sun never sets and we never sleep.

The smallest of the three dikes I will be working with

A close up on some wonderful plagioclase (about 1cm) and olivine crystals in the same dike as above

Trying to see the "sparkly" vesicles in a sample

Breaking in my new rock hammer on my first sample

Yet another Wooster geologist in Utah

July 14th, 2010

LOGAN, UTAH–I’m here to spend a few days with my parents who are “summer citizens” on the Utah State University campus. Logan is in the far northeastern corner of Utah near Idaho.  Like all of the state, it has fascinating geology. Only California can match Utah for geological diversity and splendor. There is a reason why so many geologists find themselves coming back often to Utah.

This evening we walked to the eastern edge of the USU campus and looked at the Bear River Range a few kilometers away. It is a very complex packet of rocks, part of the Logan-Huntsville Allochthon (an allochthon is a set of Paleozoic rocks pushed out of place by tectonic activity). The East Cache Fault Zone separates the valley which contains Logan from the mountains.  Some geologists believe it represents the boundary between the Basin and Range Province to the west and the Middle Rocky Mountains Province to the east.  In the image below you can see that the zone is primarily a set of normal faults. In the Logan area it shows movement during the Holocene, and it is still active today.

Looking east at the Bear River Range from Logan, Utah. The East Cache Fault Zone is in the foreground. Note the faceted spurs on the flanks of the mountains.

Tomorrow we explore Logan Canyon, which cuts perpendicularly through the Bear River Range, and look at the exposed carbonate rocks in detail. I can smell the fossils from here.

The Golden Circle Tour

July 14th, 2010

Guest Blogger: Becky Alcorn

Today we took the Golden Circle tour in Iceland. I think I saw more amazing geologic sites on this one tour than I’ve ever seen before. Our tour began at Thingvellir in the rift valley where we hiked along the Mid-Atlantic Ridge and spent a good deal of time trying to calculate the spreading rate. We then drove to Geysir where I saw my first geyser! (and enjoyed the wonderful smell of sulfur). I also got to enjoy my first taste of hamburger sauce at the visitor center there. Our tour ended with a stop at Gullfoss, an incredible waterfall with only a small rope in some places to prevent you from falling in (take your kids at your own risk, I guess).

A panoramic view of Thingvellir

Standing on the edge at Thingvellir

The original Geysir

Strokkur geyser at Geysir

The Gullfoss (Golden Waterfall)

As you can see you can get as close to the water at Gullfoss as you'd like

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