Archive for July, 2011

Wooster’s Fossil of the Week: A Conulariid (Lower Carboniferous of Indiana)

July 31st, 2011

I have some affection for these odd fossils, the conulariids. When I was a student in the Invertebrate Paleontology course taught Dr. Richard Osgood, Jr., I did my research paper on them. I had recently found a specimen in the nearby Lodi City Park. It was so different from anything I had seen that I wanted to know much more. I championed the then controversial idea that they were extinct scyphozoans (a type of cnidarian including most of what we call today the jellyfish). That is now the most popular placement for these creatures today, although I arrived at the same place mostly by luck and naïveté. (I love the critical marks in that word! And yes, I always have to look them up.)

The specimen above is Paraconularia newberryi (Winchell) found somewhere in Indiana and added to the Wooster fossil collections before 1974. (The scale below it is in millimeters.) A close view (below) shows the characteristic ridges with a central seam on one of the sides.
Conulariids range from the Ediacaran (about 550 million years ago) to the Late Triassic (about 200 million years ago). They survived three major extinctions (end-Ordovician, Late Devonian, end-Permian), which is remarkable considering the company they kept in their shallow marine environments suffered greatly. Why they went extinct in the Triassic is a mystery.

The primary oddity about conulariids is their four-fold symmetry. They had four flat sides that came together something like an inverted and extended pyramid. The wide end was opened like an aperture, although sometimes closed by four flaps. Preservation of some soft tissues shows that tentacles extended from this opening. Their exoskeleton was made of a leathery periderm with phosphatic strengthening rods rather than the typical calcite or aragonite. (Some even preserve a kind of pearl in their interiors.) Conulariids may have spent at least part of their life cycle attached to a substrate as shown below, and maybe also later as free-swimming jellyfish-like forms.

It is the four-fold symmetry and preservation of tentacles that most paleontologists see as supporting the case for a scyphozoan placement of the conulariids. Debates continue, though, with some seeing them as belonging to a separate phylum unrelated to any cnidarians. This is what’s fun about extinct and unusual animals — so much room for speculative conversations!

[Thanks to Consuelo Sendino of The Natural History Museum (London) for correcting the age range of these fascinating organisms.]

References:

Hughes, N.C., Gunderson, G.D. and Weedon, M.J. 2000. Late Cambrian conulariids from Wisconsin and Minnesota. Journal of Paleontology 74: 828-838.

Van Iten, H. 1991. Evolutionary affinities of conulariids, p. 145-155; in Simonetta, A.M. and Conway Morris, S. (eds.). The Early Evolution of Metazoa and the Significance of Problematic Taxa. Cambridge University Press, Cambridge.

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.

Wooster’s Fossil of the Week: An edrioasteroid (Upper Ordovician of Kentucky)

July 24th, 2011

This week’s fossil appeared previously in this blog when we discussed hiatus concretions and their fossil fauna. It is one of my favorites for both how we found it (see the entry linked above) and the way it introduced me to hard substrate fossils (it was my first). The edrioasteroid is the circular fossil in the center. Above it is a branching cyclostome bryozoan that will be the subject of another story someday. These fossils were found in the Kope Formation (Cincinnatian Group) of the Upper Ordovician in northern Kentucky, making them about 450 million years old.

Edrioasteroids (“seated stars”) were echinoderms (spiny-skinned animals) that lived from the Cambrian through the Permian periods (Sumrall, 2009). Their living relatives today include sea stars, sea urchins, sand dollars and crinoids. Edrioasteroids have a flattened disk-like body called a theca covered with plates of calcite. They attached themselves to hard substrates like shells, hardgrounds or cobbles (as in the photo above). On the upper surface of the theca are ambulacra extending outward from a central mouth. The anus is a little circular set of plates between two of the ambulacra. The ambulacra themselves had tiny little tube feet that extended upwards into the seawater  for filter-feeding suspended organic matter.

The fossil above, also represented in the diagram below, is Cystaster stellatus (Hall, 1866). It is a small edrioasteroid, as the group goes, and is characterized by straight, wide ambulacra.

(Image from the Cincinnati Dry Dredgers’ wonderful website.)

(Image from the public domain Encyclopaedia Britannica, 11th Edition.)

Edrioasteroids are favorite fossils for collectors. I learned this when I published a paper on the fauna that included the fossils above (Wilson, 1985) and later the outcrop was pillaged — not a single edrioasteroid remains there from the hundreds originally found.

References:

Sumrall, C.D. 2009. First definite record of Permian edrioasteroids; Neoisorophusella maslennikovi n. sp. from the Kungurian of northeast Russia. Journal of Paleontology 83: 990-993.

Wilson, M.A. 1985. Disturbance and ecologic succession in an Upper Ordovician cobble-dwelling hardground fauna. Science 228: 575-577.

Wooster’s Fossil of the Week: Pelican’s-foot snail (Pliocene of Cyprus)

July 17th, 2011

This week’s fossil was found on the same 1996 Keck Geology Expedition to Cyprus that produced the Thorny Oyster highlighted in January. Stephen Dornbos (’97) was there, but this fossil was not part of the Pliocene coral reef complex he and I described (Dornbos & Wilson, 1999), but it was in nearby shallow marine embayment muddy sediments.

The pelican’s-foot snail is Aporrhais pespelecani (Linnaeus, 1758). It got its common name before Linnaeus because of its resemblance to a pelican’s webbed foot. When the snail reached a mature size, it extended the outer lip of its aperture into spines as an anti-predatory defense (probably against crabs) and as possibly a way to spread its weight (“footprint”, if you like) on soft sediment.

A. pespelecani belongs to the Superfamily Stromboidea, a very large group that includes familiar snails like the true conch (Strombus). A recent morphological analysis suggests they are also related to the carrier shells (Xenophoridae), although genomic sequencing is needed for support (Simone, 2005).

The pelican’s-foot snail lives today in the eastern Atlantic as well as the Baltic, Black and Mediterranean seas. It is a carnivore on clams and has the ability to “flick” its muscular foot to escape predators.

These distinctive shells have been known in Europe for a very long time. I like this particular illustration by Niccolò Gualtieri (1688–1744) in which they appear to be dancing:

As is often the case with writing these little essays, I learned something about a brilliant scientist now almost forgotten. Niccolò Gualtieri was a Florentine polymath skilled in medicine, poetry, drawing, and the developing natural sciences. He had his own shell museum, so he can be said to be one of the first conchologists.

I’m sure we shared Gualtieri’s delight when we first saw these distinctive shells scattered across a dry Cypriot plain.

References:

Dornbos, S.Q. and Wilson, M.A. 1999. Paleoecology of a Pliocene coral reef in Cyprus: Recovery of a marine community from the Messinian Salinity Crisis. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 213: 103-118.

Gualtieri, N. 1742. Index Testarum Conchyliorum, quae adservantur in Museo Nicolai Gualtieri (“List of the shells of shellfish which are preserved in the museum of Niccolò Gualtieri”).

Manganelli, G. and Benocci, A. 2011. Niccolò Gualtieri (1688–1744): biographical sketch of a pioneer of conchology. Archives of Natural History 38: 174-177.

Simone, L.R.L. 2005. Comparative morphological study of representatives of the three families of Stromboidea and the Xenophoroidea (Mollusca, Caenogastropoda), with an assessment of their phylogeny. Arquivos de Zoologia 37: 141–267.

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.]

Exploring the Silurian at the Naturhistoriska Riksmuseet in Stockholm: Last day of work for the Wooster Geology Estonia Team

July 12th, 2011

STOCKHOLM, SWEDEN–No paleontological expedition is complete until it includes time in the collections of a museum. No single sampling trip like ours can describe the full diversity of a fossil site, no matter how many days we spend scouring the rocks. A traditional museum will combine the finds of hundreds of scientists over two centuries or more. The very best natural history museums, such as the Natural History Museum in London, the Smithsonian Institution National Museum of Natural History in Washington, DC, the Muséum national d’Histoire naturelle in Paris, and, of course, the Naturhistoriska Riksmuseet in Stockholm (shown above), have international collections from around the world. They set global standards for the documentation of living and extinct biodiversity. They are cathedrals of science to which we make regular pilgrimages, with all the awe and obligation that word includes.

The Naturhistoriska Riksmuseet (Royal Museum of Natural History; NRM) has the best collection of Silurian fossils in northern Europe, so we were anxious to go through the drawers and learn what we could about our own Silurian observations in Estonia. Thanks to Jonas Hagström, Senior Assistant Palaeontologist, we were given full access to the Silurian paleontology section.

Rachel Matt investigating the contents of a drawer in the NRM Silurian collections. Note the proper way of pulling open a specimen drawer: always have the drawer beneath partly open in case you accidentally pull the top drawer out too far!

The specimen drawers typically contain fossils in little cardboard trays with paper labels and a variety of stickers and numbers. Half the fun in a museum is figuring out what the organizational system is, then reading labels written in 19th Century cursive. (And in this case, in Swedish!)

Rachel making a simple photographic record of those fossils she finds that are similar to ours or should otherwise be documented for our work. Note that she has her computer open so that she can compare our field images to the museum specimens.

Nick found an excellent collection of eurypterids from the Rootsiküla Formation (Wenlock) in Estonia. He worked with these rocks in the field, but did not find any recognizable eurypterid fossils. Now he has a nice photographic collection of those in the NRM Silurian section.

After we finished our work in the collections, we toured the public displays in the NRM main building. They are fantastic. One of the highlights was this Silurian diorama showing many of our favorite extinct animals. By now you should be able to identify most of them!

Our final portrait of the trip: Nick Fedorchuk and Rachel Matt with an appropriately menacing Tyrannosaurus rex in the background. Tomorrow we leave for home! It has been an exciting adventure of science and culture.

Wooster Geologists in Sweden

July 11th, 2011

STOCKHOLM, SWEDEN–I had not realized how much water is in the city of Stockholm. Almost a third of the city’s area is water because the center is built on 14 islands connected by bridges and ferries. “The Venice of the North” some call it.

Rachel, Nick and I are here for a very short visit. We’ll spend tomorrow in the Naturhistoriska Riksmuseet (Royal Museum of Natural History), so for now we just explored the neighborhood around our hotel. It is called Östermalm and is one of the older parts of Stockholm.

The Nordiska museet (Nordic Museum) has a glorious array of building stones, all from Sweden. The simple blocks are sandstones and fine-grained metamorphic rocks, and the carved pieces are limestones.

The local bedrock is 1750-1900 million years old, formed during the Svecofennian (Svecokarelian) orogeny. The outcrops I saw, like this example of “living stone” at the base of a building, are metavolcanics (metamorphosed volcanic rocks, usually basalt). Apparently the bedrock of Stockholm is an engineering geologist’s dream because of its stability, moisture repelling capabilities, and uniform strength — great for bridge abutments and subway tunnels.

I spent my Stockholm afternoon in the museums found in an easy walk around our hotel. I was impressed with the Viking runestones on display in the Historiska muséet (History Museum), and I was touched by this one. The runes are translated as: “Una/Unna had this stone raised in memory of her son Eysteinn who died in christening robes. May God help his soul.” They are carved in a glacial granite boulder, the kind of rock we saw scattered across the Estonian western islands. Note the dark xenoliths.

A Day in Tallinn, Estonia

July 10th, 2011

TALLINN, ESTONIA–Like our Wooster Geology colleagues in Iceland, we also have a nearly-final day in a city. Tallinn is the capital of Estonia, the medieval town square of which is shown above. We started here briefly at the airport, and will leave from the same place early  tomorrow morning. The only difference is that we have one more big city to go: Stockholm, Sweden.

Tallinn, or at least a significant settlement in this place, goes back to the 11th Century, and before that there are Bronze Age artifacts. After the Danes conquered it in the 13th Century, it became known as Reval until the Estonian War of Independence in 1918-1920 when the Estonians could finally give it their own name: Tallinn (or Tallinna). It was a member of the Hanseatic League, being an important trade link between northern Europe and Russia. (And so the merchants in the town square are dressed in the Medieval garb of “Old Hansa”.) This year it is a European Capital of Culture. Tallinn does not sit on a major river but takes advantage of Ordovician limestone heights to raise it above the coastal swamps and bogs.

We enjoyed a day off in the city under (as you might have predicted) sunny skies. Tomorrow is another travel day, and then back to work one more time in Stockholm!

The newly renovated Freedom Square in Tallinn. The memorial is for the Estonian War of Independence (1918-1920).

Rachel and Nick can be barely made out here on the other side of Freedom Square.

Wooster’s Fossil of the Week: Ancient shrimp burrows (Middle Jurassic of Israel)

July 10th, 2011

This week we have a trace fossil, the burrow Thalassinoides. It is represented by one of my favorite images, reproduced above, showing a very large Thalassinoides suevicus in the Zohar Formation (Middle Jurassic, Callovian) of Makhtesh Qatan in the Negev of southern Israel. Holding the scale is Wooster geologist and Independent Study student Allison Mione (’05) during our 2004 Israel expedition. These burrows were originally described as giant desiccation cracks, but I.S. student Kevin Wolfe (’05), Israeli geologist Yoav Avni and I reinterpreted them as burrows in a rocky shore complex (see Wilson et al., 2005).

Thalassinoides is a complex trace fossil that is today made primarily by thalassinidean crustaceans (a type of shrimp; see below). We know a lot about how the burrows are made today by shrimp, and our knowledge is growing about how the ancient systems were excavated, at least in the Mesozoic and later. We have fossil shrimp preserved in Thalassinoides from the Jurassic (Sellwood, 1971) and the Cretaceous (Carvalho et al., 2007).

Pestarella tyrrhena, a modern thalassinidean shrimp. Image from Wikipedia.

Reconstruction of Mecochirus rapax in a Cretaceous Thalassinoides. A) In its burrowing life mode; B) Predominantly horizontal Thalassinoides suevicus burrow systems showing two successive event levels, with Mecochirus in life position. From Carvalho et al. (2007, fig. 3).

The burrow systems in the Zohar Formation of Israel were critical in working out the depositional environment of these carbonate sediments. We could see that first the water was comparatively deep (below wavebase) with worm burrows (Planolites). Then relative sea level dropped and the Thalassinoides burrows cut through the Planolites fabric, showing that the sediment was become stiffer. Finally bivalve borings (Gastrochaenolites) in the same rock indicated that the sediment had cemented into a shallow water hardground. This hardground showed tidal channels cut into its top surface (Wilson et al., 2005).

This work was done with virtually no “body fossils”, meaning evidence of the actual bodies of the organisms living in and on the sediment. Trace fossils, evidence of organism activity, were the only indications of this significant environmental change. This is why the study of trace fossils (ichnology) should be a part of the education of every paleontologist and sedimentologist.

References:

Carvalho, C.N., Viegas, P.A. and Cachao, M. 2007. Thalassinoides and its producer: Populations of Mecochirus buried within their burrow systems, Boca Do Chapim Formation (Lower Cretaceous), Portugal. Palaios 22: 104-109.

Sellwood, B.W. 1971. A Thalassinoides burrow containing the crustacean Glyphaea undressieri (Meyer) from the Bathonian of Oxfordshire. Palaeontology 14: 589-591.

Wilson, M.A., Wolfe, K.R., and Avni, Y. 2005. Development of a Jurassic rocky shore complex (Zohar Formation, Makhtesh Qatan, southern Israel). Isr. J. Earth Sci. 54: 171–178.

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.

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