From the Desert to the Rainforest: Heading to Alaska

gwiles June 19, 2012 12:34 pm

(Guest Blogger: Lauren Vargo)

From the desert to the rainforest, several other Wooster geologists, Dr. Greg Wiles, Jenn Horton, and myself, traveled to southeast Alaska. The main goal of the trip was to investigate Adams Inlet in Glacier Bay National Park and Preserve where we planned to use tree rings and stratigraphy to gain a more detailed geologic history of the Inlet.

However, our journey started (and ended) in Juneau with hikes up to and around Mendenhall Glacier. On our first day in the capital city, we took a leisurely hike up to the Glacier where we ate lunch near the terminus and saw first-hand glacial calving.

 

Jenn and I at the start of our hike up to Mendenhall Glacier

 

Jenn and I with the Wooster flag at Mendenhall Glacier

 

On our last day in Alaska, instead of hiking to the Glacier, we hiked up to the snow near tree line. We cored mountain hemlock trees for samples to send to a Swiss group to do isotope research, as well as to update our existing chronology.

 

Jenn and I above Mendenhall Glacier, hiking up to tree line

 

Coring a mountain hemlock tree

 

 

In between these excursions in Juneau, we traveled to Adams Inlet, our main destination, to research and collect data for our Independent Studies. We were lucky enough to have beautiful, sunny weather on our first day in the field.

 

A map of Glacier Bay National Park, with Adams Inlet marked with the red star

Jenn and I on our first day in Adams Inlet, enjoying the sun and clear view of the mountains

 

Watching the sunset on our first night in the field

 

Jenn and Dr. Wiles with all of our gear and the kayaks

 

In the Inlet, we looked at and took careful notes of the stratigraphy of several different valleys. We spent a good deal of time using the ice axe to clear off weathered and eroded sediment exposing varves (annual layers of clay and silt deposited in lakes) and other layers, usually of sand, gravel and glacial diamict.

 

Glacial lake varves we uncovered in one valley

 

 

Jenn and I sitting on top of glacial lake varves with deltaic sediment and mountains in the background

 

Dr. Wiles clearing off sediment to expose layers of varves and oxidized sand and gravel (also, notice the mud slickenlines from mudslides in the area)

 

Layers of clay alternating with sand and gravel exposed by the river cutting into the sediment

 

A closer view of clay layers within oxidized sand and gravel

 

 

In addition to the stratigraphy, in one valley we saw an amazing matrix supported rock flow.

Check out the video here.

And a second video here. 

 

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Wooster’s Fossil of the Week: a long and skinny bryozoan (Upper Cretaceous of Wyoming and South Dakota, USA)

Mark Wilson June 17, 2012 1:35 am

Please say hello to Pierrella larsoni Wilson & Taylor 2012 — a new genus and species of ctenostome bryozoan from the Upper Cretaceous (Campanian-Maastrichtian) Pierre Shale of Wyoming and South Dakota. I imagine it as a graceful little thing spreading delicately through the dark interiors of baculitid ammonite conchs on a muddy Cretaceous seafloor. Above is a fossil of Baculites formed when sediment filled the shell and lithified. The shell itself dissolved away, leaving the internal mold  of rock (or steinkern) as a kind of cast of the interior. (But don’t ever call it a “cast”!) Pierrella larsoni encrusted the inside surface of Baculites and is thus preserved as a series of connected teardrops on the outside of the internal mold. The specimen is from Heart Tail Ranch, South Dakota, and the scale bar is 10 mm. (Baculites was described in an earlier Fossil of the Week post.)

My friend Paul Taylor (The Natural History Museum, London) and I had a wonderful field trip to South Dakota and Wyoming in June 2008. We were accompanied by my ace student John Sime (who is a spectacular field paleontologist) and greatly helped by the distinguished paleontologist and ammonite expert Neal Larson (Black Hills Institute of Geological Research), Bill Wahl (Wyoming Dinosaur Center), and Mike Ross, an avid amateur paleontologist in Casper, Wyoming. We also had assistance from Walter Stein (PaleoAdventures) and the enthusiastic and knowledgeable amateur paleontologist Jamie Brezina. You can see some images from our trip here.
The primary purpose of our expedition was to find and study Late Cretaceous bryozoans. Our paper describing this work has now appeared in a special volume on bryozoan research. The specimen above on the left is from Red Bird, Wyoming, and the one on the right is from the Heart Tail Ranch in South Dakota. The scale bars are 10 and 5 mm respectively.
Above is a typical example of the Pierre Shale exposures we worked with on this trip. This particular shot is from the Chance Davis Ranch in South Dakota, but they all looked pretty much the same. We crouched down and scanned miles of “outcrop” like this, picking fossils up from the ground.

Finding ctenostome bryozoans preserved like this is unusual. They did not (and do not today) have calcareous skeletons. These Pierre specimens were somehow preserved as the internal molds formed, most likely through some process of early cementation of the mud. I described this fossil fauna and its preservation in an earlier post from a GSA meeting.

Pierrella is named after the Pierre Shale; larsoni after our colleague Neal Larson. It is nice to have locked into the name direct reminders of that delightful summer under those big Western skies.

Reference:

Wilson, M.A. and Taylor, P.D. 2012. Palaeoecology, preservation and taxonomy of encrusting ctenostome bryozoans inhabiting ammonite body chambers in the Late Cretaceous Pierre Shale of Wyoming and South Dakota, USA. In: Ernst, A., Schäfer, P. and Scholz, J. (eds.) Bryozoan Studies 2010; Lecture Notes in Earth Sciences 143: 399-412.

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Final Field Day

mpollock June 14, 2012 7:21 pm

FILLMORE, UTAH – [Guest Bloggers Tricia Hall and Will Cary]

We arrived at the field site at 9:30am with the sun already beating down on the lava fields, which are the convenient color of black. Dr. Pollock, Whitney, and Kevin parted with the rest of the group to accumulate more xenolith samples for Kevin’s project. Their group was able to stay close to the cinder cone. This was not the case for the unfortunate followers of Matt Peppers, who had to make long treks across the lava flows.

Team Hot Water (Matt Peppers and followers) started by locating Chubman, the loveable fissure, and set out to track it north. We worked as rapidly as possible in the hope of retiring early from the heat of the day. As we followed the noble Chubman, we found several anastomosing gaping fissures. Some shows some displacement, which was measured by receiving third degree burns from the hot basalt.

Will and Matt measuring the width of the fissure.

Will and Tricia measuring vertical displacement of the fissure, which may indicate a relation with the local fault..

A quick break for lunch under an intense sun left us short of water. We then tried to follow the fissure system to the mapped fault. We ran into an area where basalt debris made it nearly impossible to follow the system farther. We made our way to the fault scarp nearby and measured jointing to help determine the nature of the faulting. After the tracking was done, we quickly measured a monocline along the west margin of the black flow before heading back, our water bottles empty.

Team Hot Water measured these joints along the fault scarp west of the fissure system.

 

 

Team Sandstone (Kevin and followers) travelled around Miter crater attempting to find samples not previously collected.  Kevin began the day with 18 samples and ended with 28 samples, which mean copious amounts of lab work for the young chap. STOP…Hammer time was revamped in an hour-long effort by Kevin Silver to dislodge the xenolith, affectionately named Neopolitan, from the resilient host rock. He did not succeed and resorted to smashing the xenolith with both a hammer and a mallet to analyze the pieces in the lab.

Team Utah wraps up field work for the season.

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A Visit to the Utah Core Research Center

mpollock June 13, 2012 7:20 pm

SALT LAKE CITY, UTAH – On Tuesday, Team Utah visited the Core Research Center at the Utah Geological Survey. The repository includes cores and cuttings from more than 4000 wells, on-site microscope facilities, and a friendly and knowledgeable staff. We suspect that the sedimentary xenoliths that Kevin has been finding represent Lake Bonneville sediments. Tom Dempster and Peter Nielsen pulled out some cuttings for us to look at and set up the microscope. Mark Gwynn showed us some core that they recently recovered from an area near our study site.

Kevin examines some cuttings under a binocular microscope and projects the image so that we can discuss it as a group.

We also had the chance to meet with Amanda Hintz, a UGS geologist with an expertise in the Black Rock Desert.

Amanda so graciously gave us part of her day to answer our questions about bombs, xenoliths, lava flows, and faulting.

Finally, Stephanie Earls, the UGS Research Librarian, was so helpful in finding historic aerial photographs for us.

Matt, Dr. Judge, and Whitney examine the aerial photos, trying to make sense of the lava flows surrounding our cinder cone.

After a productive day at the research center, we visited Bingham Canyon on the way out of town.

View of the Bingham Canyon mine from the visitor's center.

Although it make for a long day and a late night, our trip to Salt Lake City was instrumental in helping us think about our field area as we wrap up our field season. Thanks to all of the folks at the UGS for their help!

 

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The Joys of Mobbing

mpollock June 11, 2012 10:44 pm

FILLMORE, UTAH – [Guest Bloggers Matt Peppers, Whitney Sims, and Will Cary]

Wizard Will enjoys some early morning tomfoolery.

With our alarms set for 6:30, we guaranteed that we wouldn’t be up before 7 am. After a hurried lunch packing session, the group headed out to inaugurate Tricia into the research community. She will be doing a project focused on the origin of the basalt islands in the western channel. Hopefully, her project will be used as an analogue for the islands found in the rest of the lava field. We mobbed Tricia in the morning, and through a heroic effort, managed to complete her fieldwork in just under three hours. Dr. Shelley “The Machine” Judge burned through a majority of the 50 individual columnar joint orientation measurements that will help Tricia with her interpretations. While the measurement team ran through the orientation measurements, the rest of the group broke into two smaller teams to collect samples and track out the significant fractures in the area. With each person working toward his or her specialty, the data collection process flew by.

Mob mentality at work.

 

Riding high after a stellar group outing, we moved toward the western breach to take a look at a large fissure Dr. Pollock, Whitney, and Tricia had seen a few days before. When we came across the gaping fissure (nicknamed “Chubman”), we decided to take a well-earned lunch break in the shade of the nearby wall before tackling the measurement process. While Team Fissure worked on mapping and tracking the fissure in the northern end, Team Flow Bandits tracked the fissure south on their way to investigate the possibility of a nearby flow boundary. The familiar call and response of, “Whitney, do you want to take a sample here?” followed by a subdued, “Yes…” echoed throughout the flows as the day came to an end. We had a weary trek back through the sand and sagebrush back to the car, satisfied after a productive workday. Celebratory pie for desert was the icing on the cake to yet another day in paradise.

The "Chubman" Fissure dominates the landscape.

 

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A Rocky Start

mpollock June 11, 2012 12:21 am

FILLMORE, UTAH – Today’s return to field work after a fun day in Bryce Canyon was a little rocky at first.

We were a little confused about where to begin.

After a short while, we found our purpose.

Whitney and her team spent the day mapping lava flows that breached the northern rim of the cinder cone.

Fortunately, Whitney had Matt on her team, who chiseled samples from the solid rock with his raw strength.

Will and his team spent another day hunting bombs and blocks on the rim.

In the end, it was a fantastic field day. Will has nearly wrapped up his ballistics sampling and Whitney can practically redraw the lava flow map. Back to the lava fields tomorrow!

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Wooster’s Fossils of the Week: dinosaur gastroliths (Jurassic of Utah, USA)

Mark Wilson June 10, 2012 1:52 am

These rounded stones are labeled in our collections as gastroliths (literally “stomach stones”) from Starr Springs near Hanksville, Wayne County, Utah. I’m featuring them this week in honor of our Utah Project team working right now in the baking Black Rock Desert near Fillmore, Utah.

From their reported location, these stones are likely out of the Summerville Formation (Middle-Upper Jurassic) and, in another plausible supposition, probably from some sort of dinosaur. Sometimes we just have to trust the labels on our specimens, at least for educational purposes!

My friend Tony Martin recently wrote an excellent blog post on gastroliths, so I won’t repeat his insights here. The general wisdom is that these stones were consumed by herbivorous dinosaurs to aid in their digestion. They would have lodged them in the equivalent of a gizzard and used them to grind their food, much like modern birds. (And yes, dinosaurs were birds themselves.) Gastroliths usually have a resistant lithology to be useful as grinders. The gastroliths above are chert, one of the hardest rock types.

Identifying gastroliths correctly is a bit of a challenge if you don’t find them inside a dinosaur skeleton. The most common indicators are that they are very smooth, are in a location where they were unlikely to have been transported inorganically, and are of a lithology unlike the surrounding rock (“exotics” as geologists like to call them). Still, even with all these criteria met, we must be a tad suspicious if we didn’t find them associated with dinosaur bones. I would never, for example, buy a gastrolith in a rock shop. Without context, it could be just a stream-worn stone. I’m trusting the label on ours that we have the real deal!

References:

Stokes, W.L. 1987. Dinosaur gastroliths revisited. Journal of Paleontology 61: 1242-1246.

Wings, O. 2007. A review of gastrolith function with implications for fossil vertebrates and a revised classification. Acta Palaeontologica Polonica 52: 1-16.

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Team Utah Visits Bryce Canyon

mpollock June 10, 2012 1:01 am

BRYCE CANYON, UTAH – In recognition of National Get Outdoors Day, Team Utah visited Bryce Canyon National Park. The park is famous for its gorgeous hoodoos. Here are a few pictures from our day.

Team Utah representing Wooster at the Bryce Canyon Visitor Center.

Dr. Pollock tries not to be blown over the rim by the wind.

Dr. Judge shows off her field hat.

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STOP, Hammer Time

mpollock June 8, 2012 10:55 pm

FILLMORE, UTAH – [Guest Bloggers Matt Peppers and Will Cary]

On the morning of the 8th, all seemed well. Much like days before, we all arose and began to pack our lunches for the day. However, as we piled into the car, an ominous light started to blink on the dashboard. Low tire pressure. Concerned, Dr. Judge pulled us into a nearby gas station and checked the tires. Much to our dismay, the left rear tire was 10 psi lower than it should be, a repeat occurrence from a few days earlier. Not wanting to jeopardize our upcoming Mystery Fun Day, Drs. Judge and Pollock made the decision to take the car into a repair shop to have the problem diagnosed. While they were gone, they left us to wreak havoc upon the KOA Kampground. We started by swimming and relaxing by the pool, and ended by swimming and relaxing by the pool. All before lunchtime. We retired to our individual cabins to enjoy the lunches we had packed a few hours earlier in glorious air conditioned komfort.

 

Around 1 pm, the professors returned and it was business as usual. Even though we had lost half of our day to a small hole in the tire (curse you, basalt!) we rushed out to mob Kevin’s project for the afternoon. Arriving on the cinder cone at peak temperature made for a challenging work environment (especially after having spent most of the day in a sun-induced stupor) but we turned the afternoon into a very productive, albeit rushed, day. After reviewing the wall Kevin had used to map his xenoliths, we spread out and tried to collect as many of the 16 different types as we could find. After a few small injuries, stumbles, artistic work with a rock hammer, and some sore hands trying to pry the xenoliths out of the uncooperative host rock, we amassed a small mountain of samples for Kevin. As Whitney struggled to bag and record the samples in the gusting wind, the rest of us made one last sweep of the area for any xenoliths to claim.

Aptly named, the "Avocado" xenolith inspired some dinner choices this evening.

The "Sparkly" xenolith refuses to show its nature in photographs.

 

The "Black and Green" xenolith.

Tricia demonstrates proper hammer usage.

We trooped back down the van, and made the dusty trek back to the kampsite, just in time to shower and recover before we left for dinner at six. After a quick stop to pick up a package containing some hardier field notebooks we went of to dinner followed by a stop for ice cream, where the professors revealed the Fun Trip they had planned for Saturday. We will be driving down to Bryce Canyon on the morrow to spend the day in the park. None of us have been there, so it promises to be a unique experience for us all!

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Sailing the Basalt Isles

mpollock June 8, 2012 10:51 pm

FILLMORE, UTAH – [Guest Bloggers Whitney Sims and Kevin Silver]

As we arose for our fourth day of field study, the morning was chilly. However, this was to be short lived. A clear day unleashed the full power of the sun upon the Black Rock Desert as we parked our van and began our trek onto the lava flows once again.  It was Whitney and Matt’s day to lead again and the group was split in two to assist each of them.

Matt’s group was comprised of Dr. Judge, Kevin, and Will. Their goal was to look at the walls of the lava channel to find any structural features and to study the islands of basalt that were scattered across the floor of the lava channel. From there, they were planning to travel west towards a portion of the map that showed faulting near the end of the lava channel. Instead, they quickly deviated from the plan as the floor of the lava channel closer to the cinder cone showed great promise. Their day was spent tracking and measuring fissure fractures that ran both perpendicular and parallel to the walls of the lava channel. Many of these fissures were found to run right through the basalt islands. In addition, a large fault was discovered above the cliff face. Due to the wealth of data and the absolute lack of shade the study site provided, the work was very tedious and many of us, most noticeably the fairest-skinned of us, began suffering from exposure. It was a most joyous occasion when our two groups were reunited once more and were heading back to the van. Despite her preconceptions of horror, Dr. Judge found that accompanying the three boys in the field was nothing but pleasant interactions and behavior on the most professional of levels.

Tricia Hall standing on top of a basalt island

 

Whitney’s group was comprised of Dr. Pollock, Tricia, and Whitney. Their goal was to collect samples from different sections of the lava channel while travelling west to determine where the lava channel ended. They came upon what is believed to be the western breach of the flow that showed significant promise to Whitney’s project. Upon their trek, they came across a major fault that Dr. Pollock was really excited about.

 

Whitney Sims and Tricia Hall overlook a large fissure cutting through the lava flows of Ice Springs

The day was very productive and rich in data. It has become apparent that Matt currently holds the equivalent of three I.S. projects in his data and thus will not graduate in 2013. Whitney’s project is proving to be quite complex as Ice Springs is proving to hold some unusual structure and complexity within its flows. There is no certainty what future days in the field will reveal.

a lava tube, half filled with lava, in Ice Springs

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