Theory to Practice: An Early GSA Abstract

May 11th, 2012

This semester, I’ve had the pleasure of teaching a special topics lab course in geochemistry. Given our new lab facilities, I decided to approach the class as an analytical geochemistry course. We explored sampling strategies, data quality, and the theory and techniques behind X-ray methods (XRF), electron-beam methods (SEM-EDS), and mass spectroscopy methods (ICP-MS).  Unlike a typical survey course, our course was entirely research-based. We actually became analytical geochemists by conducting an authentic research project on a suite of Icelandic basalts. Our goal was to investigate the development of a structural basin in northern Iceland by interpreting the petrogenesis of lavas that were erupted during different phases of basin construction. This week, we’ve accomplished our goal and have written an abstract to submit to the Fall 2012 meeting of GSA.

Here is the text of the abstract:

A GEOCHEMICAL ANALYSIS OF THE VATNSDALFJALL STRUCTURAL BASIN, SKAGI PENINSULA, NORTHWEST ICELAND

Matthew Peppers, Sarah Appleton, Lindsey Bowman, Andrew Collins, Whitney Sims, Melissa Torma, Meagen Pollock

Vatnsdalfjall, in northwest Iceland, exposes the upper ~700 m of crust formed ~7 Ma ago at the extinct Hunafloi-Skagi rift zone. In general, the lava flows dip gently westward toward the abandoned rift axis, but are interrupted by a local area of steeply dipping lava flows known as the Vatnsdalur Structural Basin (VSB). The VSB is composed of three sequences of lava flows emplaced before, during, and after subsidence. Using the geochemistry (XRF, ICP-MS) of samples gathered in the field in 2006 and 2007 and previous data from Ackerly (2004) and McClanahan (2004), we were able to establish a basic eruptive history for the sequences. Major element analysis shows diverse rock types, including basalt, basaltic andesite, dacite, and rhyolite. Sequence 1 shows the greatest diversity and was primarily affected by mineral accumulation, while Sequences 2, 3, and the dikes follow the trend of a shallow level fractional crystallization model based on a modified parent magma from Sequence 1. Trace element ratios suggest the presence of 1 (or 2) parent magmas, although the intermediate to silicic lavas appear to be generated by a separate process. Sequence 1 contains various lava flows, each with a uniform thickness, emplaced on relatively flat terrain. Sequence 2 was emplaced on top of Sequence 1 as subsidence of the basin was occurring, creating lava flows that thicken toward the basin interior. Intermediate to silicic rocks are absent during this interval and dikes cut Sequence 1 to feed lavas in Sequence 2. After a period of erosion, Sequence 3 was erupted above Sequence 2. Dikes that feed Sequence 3 cut through Sequence 2. The development of the VSB may have been associated with a waning period in the magmatic system, where magmas cooled and evolved (following an evolutionary trend controlled by fractional crystallization) and there was little partial melting of the crust (given the lack of intermediate to silicic lavas).

And some key figures:

Geologic map that shows the location of our samples on Sequence 1 (green), Sequence 2 (pink), and Sequence 3 (blue).

CaO vs. MgO (wt%). Symbols for dikes and Sequences 1, 2, and 3 are as shown on the geologic map. Previous data outlined by the dashed line. Fractional crystallization model shown by the black like. Arrows indicate effects of mineral accumulation. Plagioclase (pentagons) and clinopyroxene (stars) are also shown.

Schematic model (not to scale) for the development of the basin.

I applaud all of the students for their excellent work. They really took ownership of this project and deserve all of the credit. Look for us at GSA in the fall!

Wooster Geologists: Communicating New Knowledge

April 7th, 2012

AMHERST, MA – Congratulations to Wooster Geology Seniors Katharine and Andrew for their excellent presentations at today’s Keck Symposium! Andrew presented the results of his remote sensing investigation of channels on Ascraeus Mons on Mars. Andrew compared his channels to those on Pavonis Mons and in Hawaii. He characterized his channels as volcanic in origin based on their spatial distribution, surface stratigraphy, and geomorphological relationships.

Andrew poses by his poster during a rare quiet moment at the poster session.

Katharine presented her study of the Hrafnfjordur central volcano in the West Fjords of northwest Iceland. She found a complicated sequence of eruptive units that includes pyroclastic material, basalt, andesite, and dacite. Using geochemistry, Katharine determined that the units fall on different, genetically unrelated trends, suggesting that the Hrafnfjordur central volcano has a complex magmatic history.

Katharine enthusiastically explains her study to a thoughtful listener.

Overall, the Keck students are truly a motivated and talented bunch. It’s amazing to see what these students have accomplished over the course of a year. The symposium is not only a celebration of their achievements, it’s a powerful moment in which these students officially become part of the Keck alumni family.

The 2011-2012 Wooster Keck alumni.

Field Trip Friday

April 6th, 2012

AMHERST, MA – If you were following our adventures last summer, you’ll remember that Wooster helped lead a 6-student Keck trip to the West Fjords in northwest Iceland. You may not know that we also had a Wooster presence on the Keck Mars project. Now, after nearly a year of hard work, all of the Keck students are coming together at the Keck Symposium to share their findings and celebrate their accomplishments. This year, we’re at Amherst College in Massachusetts. The symposium kicked off today with glorious weather and a local field trip featuring “The ABV’s of Valley Geology: Arkose, Bedrock, and Varves.”

Our first stop was in the Moretown Formation. These early Paleozoic rocks were originally deposited on the edge of the continent and were subsequently deformed during the Taconic and (perhaps) the Acadian Orogenies. The outcrop consisted of interbedded schist and quartzite that had been metamorphosed to upper greenschist – lower amphibolite facies. We observed tight folds that showed fantastic crenulation cleavage, which developed as a result of multiple folding events.

Side-view of the crenulation cleavage, almost looking down the cleavage crenulation hinge.

The light reflects off of the wavy surface of micaceous schist layers. The pen is nearly aligned with the cleavage crenulation hinge.

Garnet porphyroblasts in the Moretown Formation.

After a brief stop at the Yankee Candle Company (what’s not to like about hot coffee, clean restrooms, and plentiful scented candles?), we made our way to Mt. Sugarloaf. Here, we visited the type locality for the Triassic Sugarloaf Arkose, a feldspar-rich sandstone and matrix-supported conglomerate. The arkose was deposited in the Deerfield rift basin during the opening of the Atlantic. Abundant orthoclase suggests that the sediment was close to its source. Most of the sediment was deposited by debris flows, but there is some evidence for reworking by a braided stream system.

Conglomeratic section of the Sugarloaf arkose.

We hiked to the top of Mt. Sugarloaf for a scenic lunch stop, where we had a breathtaking view of the Mesozoic rift valley in which the Sugarloaf arkose was deposited.

View from the top of Mt. Sugarloaf.

After lunch, we traveled back to 15,000 years ago, when the rift valley was filled with proglacial lake Hitchcock. The lake was over 200 km long, stretching from upstate Vermont to central Connecticut. Seasonal layers of silt and clay were deposited on the lake bottom, forming varves. It’s the flat-lying varves that make the valley floor so flat. The annual layers were also critical in the development of the New England Varve Chronology, which suggest that the lake existed for over 4,000 years.

Lake Hitchcock varves.

Close-up view of the annual layers in the Lake Hitchcock varves.

Our last stop of the day was to see the trace fossil Eubrontes (aka dinosaur footprints). The three-toed tracks are subparallel. If the tracks are the same age, then they may have recorded a passing herd. If the tracks are on different bedding planes, then this area may have been on a migration route. The Amherst College Beneski Museum of Natural History hosts the largest collection of dinosaur tracks world, primarily collected by Edward Hitchcock (also of the proglacial lake, third president of Amherst College, 1845-1854).

Three-toed dinosaur footprint. Do you see it?

It was nice of the dinosaurs to outline their footprints in chalk to make it easier for us to see!

We finished the evening with a reception at the museum (a drool-worthy collection that will be the focus of a future post). After a quick pizza dinner, the Iceland group is meeting for the last time to work on tomorrow’s presentations. It’s a bittersweet meeting; it’s fun to bring everyone together to compare findings and pat ourselves on our backs for a job well done, but it’s a bit sad to know that our Keck experience is coming to an end.

The Iceland crew on the Keck Field Trip.

Keck Mission Accomplished

August 7th, 2011

WOOSTER, OH – After a month of hard work, the Iceland Keck group parted ways on Saturday. We arrived in Wooster immediately after returning from Iceland and put in a solid week of work in the lab, preparing our samples for thin sections and XRF analyses. In one week, the students produced over 120 thin section billets, powders, and pressed pellets, and almost as many glass beads. Even though the work was tedious and the hours were long, I think we’re all glad that we’ll have data at the start of the school year. Well done, team!

A dessicator full of pressed pellets ready to analyze on the XRF.

 

Challenges of lab work. We tracked the number of samples that were prepared. This student prepped 20 pressed pellets "of varying degrees of brilliance + some epic failures."

Katharine works her magic on the scale.

Erica grinds the saw marks off of her sample.

Nina presses a brilliant pellet.

Thad oxidizes his samples in the muffle furnace.

Emily celebrates a glass bead that hasn't cracked.

Brennan and Katie troubleshoot the GIS file.

Of course, our work isn’t complete. Once we have the chemistry and thin section observations, we can put the data into the context of the mapped field relationships to understand the volcanic history of one of the oldest central volcanoes in Iceland. We’ll have much to present at the Keck Symposium in the spring and are already looking forward to our reunion.

A Keck Adventure at 66 North

July 28th, 2011

West Fjords, Iceland – We’re happy to report that the 2011 Iceland Keck crew has safely completed a productive field season. Nearly two weeks ago, a boat dropped us off in Hornstrandir, a nature preserve that encompasses most of the northern portion of the West Fjords. Our field area centered around Hrafnsfjordur, or Raven Fjord, in the southern extent of Hornstrandir. We had no idea that Hrafnsfjordur was a popular destination; it’s one of the primary drop-off and pick-up points for backpackers in the region. We must have seen at least half a dozen hikers during our stay. Hiking trails snake their way around the fjord and over the passes, which was fortunate for us since we had to access all of our field areas on foot.

A very still day in Hrafnsfjordur.

After a couple of days of recon hiking as a group, the students selected their projects and went to work. Most students chose to map a portion of the fjord, although one student focused on mapping and sampling dikes. Students worked in teams of two, each team being assisted by a faculty member.

A very sunny day in Hornstrandir.

Field work was challenging. Like our Alaskan colleagues, we had dramatic stream crossings, treks across snow, and hikes up steep terrain. Although we never saw a bear, we spotted an arctic fox in the distance. Thankfully, the fox wasn’t interested in our food. Dehydrated meals at the end of a long field day never tasted so good!

Coast guard performing drills outside our hostel in Isafjordur.

The weather was mostly good, by Iceland standards. It seems as if we were constantly confronted with either bugs, wind, or rain, but always just one at a time. Whenever Emily worked in her area, though, the sun would shine!

Hiking up snow to reach the peak.

We took a chartered boat back to Isafjordur on Wednesday and spent one last day in the field mapping a local mountain called Sauratindur. Now that we’re finished with field work and have returned to civilization, we realize how thankful we are for hot showers and soft mattresses. Still, there are some things that we’re already missing: the view from our tents, the sound of the waterfall (especially at night), the soft moss, our own private fjord, the hot cocoa, our special treat at the end of each day, and the freshness of the air.

Our Keck adventure in Hrafnsfjordur, in Hornstrandir.

Tomorrow, we start our long journey back to the states (via Reykjavik). We’re eager to get back to Wooster to start processing our samples. Hrafnsfjordur offered us an amazing amount of what we think are intermediate lava flows, which would be unique for Iceland. Dominated by basalt with local regions of rhyolite around central volcanoes, intermediate lavas are relatively sparse. Our field mapping, thin section observations, and geochemical analyses should yield some insights into the formation of Hrafnsfjordur’s central volcano. Stay tuned!

Panorama from the top of Manafell in Hrafnsfjordur.

Students playing a game of rock while waiting on the boat.

Textbook hanging valley in Isafjordur.

The boat that came to pick us up- one trip for gear and rocks!

The view from my tent in Hranfsfjordur, Keck.

Familiar scene for geo types- hiking up waterfall cuts for good exposure.

2011 Keck Iceland is Official

July 15th, 2011

2011 Keck Iceland Group on columns.

ICELAND – As Lindsey and Travis were leaving Iceland, the Keck students were arriving. The Keck Geology Consortium consists of 18 schools whose geology departments are dedicated to providing undergraduates with high-quality research experiences. Funded through NSF and contributions from its members, the Keck Consortium supports several research projects each year. This year, I’m working with Dr. Brennan Jordan (University of South Dakota) on a 6-student Keck project in the West Fjords of Iceland. We’ll spend three weeks working in the field, then return to Wooster for another week in the lab.

After spending a day in Reykjavik recovering from jet lag and getting to know each other, we left for a four-day field trip to south central Iceland. The field trip serves several purposes: (1) build a sense of community, (2) get a sense for the provisions we’ll need in the field, and (3) observe geologic features that might be exposed in our study site.

We started by touring the Reykjanes Peninsula, visiting some sites that Travis and Lindsey had just seen. We observed marine pillow basalts, tuffs with embedded blocks, a dike feeding a lava flow, and lots of fissures. We ended the first day at Thingvellir and had our first taste of the dehydrated meals that will be our dinners for the time we’re in our field area. We all agreed that they tasted better and were more filling than we expected!

The second day began at an amazing exposure of subglacial pillow basalts. We almost didn’t get to visit this site because a film crew was shooting a car commercial at the exposure (complete with a thundering herd of Icelandic horses). Fortunately, they were kind enough to let us in for a short time, and it was worth it! Afterward, we visited Geysir (the original) and Gullfoss, where we saw glacial striations and a stunning waterfall.

Amazing pillow basalts near Thingvellir.

The second day ended (and the third day began) at Landmannalauger, a popular hot spring destination (I’ll let the Keck students tell you about their hot spring experience). Landmannalauger is surrounded by rhyolite slopes that form the walls of a giant caldera. Just behind the campground, a hiking trail winds its way over a blocky rhyolite flow, where we observed lots of flow banding, obsidian, and pumice altered to a beautiful green color. On the way out of Landmannalauger, we saw a few more rhyolite flows, a gorgeous cinder cone, and some Hekla tephra. You may recall that Hekla was recently reported in the news as “ready to erupt.” Rest assured that all was peaceful when we were there.

Before we returned to Reykjavik on the last day, we made a couple of quick stops in south-central Iceland near Dyrholaey to see spectacular columnar joints.

Dike intruding through tuff on the southern Reykjanes peninsula.

Back in Reykjavik, we caught our flight to Isafjordur in the West Fjords. We’re all eager and ready to go to our field site. Having seen a wide range of geologic features, we feel prepared for whatever our field site offers. Tomorrow, we’ll take a boat to the site, one of the most remote places in Iceland. Look for another post when we return from the field. Wish us luck!

*Sorry about the lack of pictures! If you know a way to post pictures to a blog from the iPad, please let me know! As an alternative, feel free to check out the pictures that I’ve posted on my twitter feed: twitter.com/meagenpollock

[Images added on July 18, 2011, from Meagen Pollock's Twitter feed.]

A Day in Akureyri

July 9th, 2011

AKUREYRI, ICELAND – Since we finished Travis’ field work a day early, we were able to spend Friday in Akureyri, Iceland’s second-largest city. Akureyri has an idyllic location, nestled between a fjord and snow-capped mountains in north-central Iceland.

 

Snow-capped peaks make a scenic background for Akureyri.

Our first stop was at the Botanical Gardens, which hosted a surprising variety of plants, given Akureyri’s rugged climate. We saw some familiar flowers that reminded us of the field:

 

This yellow flower was common in our field areas (it's Icelandic name is Argentina egedii Skeljamura).

We saw this delicate purple flower often, too (Viola canina Tysfjola).

This sweet flower grew in the jagged spaces between rock piles (Silene uniflora Holurt).

There were other flowers that were more exotic:

 

The vivid blue petals of this Meconopsis grandis Fagurblasol were stunning.

And then there were flowers that were much too familiar:

 

A well-established specimen of our friend, the dandelion.

Next to the Botanical Gardens, we contemplated statues on the campus of Akureyri’s University.

 

Dr. Pollock interpreted this sculpture to mean that basalt is the foundation of the world.

Next, we admired the Akureyrarkirkja, a columnar basalt-themed church that was designed by the same architect who built Reykjavik’s famous Hallgrimskirkja.

 

The Akureyrarkirkja.

Finally, we visited the historic district for some food and shopping.

 

View of historic Akureyri. We highly recommend Cafe Paris, in the blue building on the right. The soup and bread is delicious!

 

 

 

Perhaps a little light reading for the trip home?

 

Lindsey and Dr. Pollock find hats for their next field experience.

A day in Akureyri was the perfect way to celebrate the successful end of two I.S. field projects. We happily headed back to our cabin in Blonduos, where we packed up for our journey back to Hafnarfjordur and started working on our GSA abstracts, which our Estonian colleagues have inspired.

Return to Vatnsdalfjall

July 9th, 2011

BLONDUOS, ICELAND – Meagen and guest blogger, Travis

We returned to Vatnsdalfjall for the second day of field work on the Monocline. The weather was the best we’ve experienced in Iceland yet.

View of the steeply dipping Monocline as it dives under the Hjallin Lens.

After a long hike through fields of sadness (so named by a previous IS student), we finally made it to our first exposure. We found lots of interesting amygdules (filled vesicles):

Vesicles half-filled with chalcedony in horizontal layers suggests that the lavas were tilted before the chalcedony precipitated.

Zeolites come in a variety of habits, including these hair-like fibers that are about 1 cm long.

We sampled and made observations all of the way to the top of the Monocline. We were quite pleased with ourselves when we made it to the top, and slightly surprised to see that it was already 8 pm! In the land of the midnight sun, field work could last for 24 hours a day.

Lindsey and Travis getting ready to head down the mountain at 8 pm at night.

After such a hard day of work, we relaxed in the evening and made plans to visit Akureyri the next day.

Travis relaxes in the hot tub.

 

First day at Vatnsdalsfjall

July 7th, 2011

BLONDUOS, ICELAND: Guest Blogger: Lindsey

Yesterday was our first day of field work on Vatnsdalsfjall, a mountain located on the Skagi peninsula. Vatnsdalsfjall exposes lavas erupted 7 million years ago from an ancient rift located to the West. We know this because the lava flows in this area dip towards the ancient rift axis in the West; yes Dr. Judge, we used a Brunton compass! We hiked up through a sheep field to the base of the outcrop; we then continued hiking up a gulley until we started to see zeolites. The first zeolites we saw were also found with a green clay:

Green clay and filled vesicles in our first zeolite-bearing outcrop

As we climbed higher, we continued to see zeolites in a variety of sizes. Travis’s tip to me was to look for the white zeolites, as these are more diagnostic of their environment of formation (temperature). It was important to keep track of the units we were climbing up through, as boundaries between flows were frequent.

Travis demonstrates proper use of a field notebook

Because of the steeply dipping flows, we had to bear in mind that as we got higher, the units being exposed were actually stratigraphically underlying the units we had seen earlier at the base of the gully. One particular unit of note was a gorgeous plagioclase rich marker bed; it also had zeolites in it that we sampled:

Plagioclase-phyric marker bed

Overall yesterday, we sampled a total of 50 meters of zeolites, and according to Rob Lydell’s (’10) notes, we have about 50 meters left to sample today. Due to the fog we experienced yesterday morning, we decided to go out this afternoon so that we could see a little bit better:

Travis perches on a slope to take notes, notice the fog in the background!

Unfortunately, this has given me more time to dread this afternoon’s hike-Travis and I are pretty sure that Vatnsdalsfjall literally translates to “Death Mountain” in english as this is the steepest thing he or I have ever hiked.

"How do Mountain goats do this?!?!" -Travis

Not only is it steep, the loose apple to watermelon-sized talus makes every step treacherous; I bit it a couple of times and I have the bruises to show for it! I know our Alaskan colleagues probably have no sympathy as it sounds like their hiking was rigorous as well! However, the successful sampling we completed yesterday as well as the panoramic views of the valley below over PB&J at lunchtime make it well worth it.

Thingvellir and the trip North

July 6th, 2011

Blonduos, Iceland-

[Guest blogger: Travis Louvain]

So as we completed the research on the Reykjanes Penninsula, we traveled up north to the Skagi Peninsula to a town called Blonduos.

Car pictures are always a necessity.

On the way we stopped at a place called Thingvellir. This site is home of the first Icelandic Parliament and a beautiful national park.

A beautiful stream that cuts right through the middle of the main fissure.

The place was chosen by the early Icelanders because it was relatively easy to access and because it is a amazingly flat valley. Why is this? Well that’s where the geology comes in. This national park is not only home to the first parliament but also it is a site of active rifting.

 

Path through the middle of a large fissure leading to the site of the original parliament. When it met they used to make speeches from the taller side of the fissure to a crowd listening on the other side.

So the flat valley is actually the result of the two plates rifting away from one another. This can clearly be seen in the large fissures which are a highlight of this site.

 

Large fissures run through the ground all over the place. Some are only a foot deep, but some drop for tens of feet.

The rift valley from atop the large fissure.

After this we continued driving north mostly along the coast. At one point we went under a large fjord by way of tunnel and under the following mountain before coming out on the other side where we stopped for lunch. As we drove we saw many sheep and horse farms. We also drove up into the mountains where the mountain tops were still covered with snow.

Snowy mountaintop. We continued seeing sheep roaming even at these high altitudes.

As we drove to Blonduos we passed my field site and decided to ask permission to go up the mountain side. As I sat in the car wondering whether or not I was going to have an I.S. or not, I couldn’t help but laugh at Dr. Pollock making gestures with her arms while talking to the lady who owned the land. It turns out that the lady spoke English fairly well and Dr. Pollock was just using large hand gestures cause she liked to, but the good news was that she gave us permission to go up the mountain.

After this, we continued to Blonduos which happened to be very close. We checked in to our cabin which was complete with a kitchen, bathroom, fridge, propane grill, and a hot tub. Yes, a hot tub!

Well to wrap up today I finished a video that I’ve been working on from our fourth day where we explored the southern portion of the Reykjanes Peninsula. I hope you enjoy it.

The Southern Reykjanes Adventure

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