A record of ancient earthquakes

December 15th, 2009

MAYSVILLE, KENTUCKY–Strong earthquakes produce seismic waves which can do much damage on land, as we well know.  They can also disturb unconsolidated sediments on shallow oceanic shelves and platforms, producing characteristically swirled structures called seismites.  The Upper Ordovician outcrop we visited today has three horizons of well-preserved seismites associated with those strange blocks described previously.

The "ball-and-pillow" structures in this view of the Kentucky Route 11 outcrop of the Fairview Formation are seismites produced by Late Ordovician earthquakes.  There are two seismite horizons, each with a flattened top produced by later erosion and redistribution of the sediments by oceanic currents.

The "ball-and-pillow" structures in this view of the Kentucky Route 11 outcrop of the Fairview Formation are seismites produced by Late Ordovician earthquakes. There are two seismite horizons visible here, each with a flattened top produced by later erosion and redistribution of the sediments by oceanic currents.

Closer view of a seismite in the Kentucky Route 11 outcrop.  I couldn't reach this high to place my hammer for scale.  The structure is about a meter thick.

Closer view of a seismite in the Kentucky Route 11 outcrop. ( I couldn't reach this high to place my hammer for scale; the structure is about a meter thick.)

The earthquakes which caused these seismites were probably associated with orogenic (mountain-building) activity to the east where the present (and much later) Appalachian Mountains sit.  Careful measurement and mapping of seismites can tell us much about the specific locations and magnitudes of these earthquakes, as well as the consistency of the sediments they disturbed long ago on those ancient seafloors.

Mysterious out-of-place rocks in the Ordovician of Kentucky

December 15th, 2009

MAYSVILLE, KENTUCKY–Our short geological expedition to northern Kentucky today was to look at some odd blocks of limestone that sit suspended in the sediments as if they were dropped in while the sequence was accumulating.

An eroded, bored and encrusted limestone block in the Fairview Formation (Upper Ordovician) of northern Kentucky at the Route 11 outcrop (N38.61243°, W83.75575°).

An eroded, bored and encrusted limestone block in the Fairview Formation (Upper Ordovician) of northern Kentucky at the Route 11 outcrop (N38.61243°, W83.75575°).

These rocks are bored by worms and encrusted by bryozoans on their top and sides, and they often sit at high angles to the surrounding strata.

Bryozoans encrusting a side of the block above. The beautiful pinkish bryozoan on the left is the holdfast of a ptilodictyoid which in life held an erect bifoliate portion of the colony. The field of view here is about 10 cm wide.

Bryozoans encrusting a side of the block above. The beautiful pinkish bryozoan on the left is the holdfast of a ptilodictyoid which in life held an erect bifoliate portion of the colony. The field of view here is about 10 cm wide.

It is difficult to imagine a mechanism which deposited large, lithified limestone blocks in the middle of a shallow carbonate ramp. They are almost certainly related to “seismite” structures in the outcrop (see next post), but how these earthquakes would have transported such rocks is a mystery.  We also do not know how quickly the limestone had been lithified before emplacement.  We do know that the sides of these blocks were exposed on the seafloor long enough to accumulate encrusters and borers.

Plenty yet to discover in these well-studied rocks.  It is a continuing lesson for scientists: the more you see the more questions you have.

Wooster Geologist in Kentucky

December 15th, 2009

MAYSVILLE, KENTUCKY–Today I visited the University of Cincinnati for a meeting of Aaron House’s thesis committee, on which I serve.  (Aaron is a 2004 geology graduate from The College of Wooster.)  It all went very well and soon after Aaron took me and two other geologists on a short field trip to an Upper Ordovician outcrop near the Ohio River town of Maysville.

Outcrop of the upper Fairview Formation (Upper Ordovician) on Kentucky Route 11 near Maysville, Kentucky (N38.61243°, W83.75575°).

Outcrop of the upper Fairview Formation (Upper Ordovician) on Kentucky Route 11 near Maysville, Kentucky (N38.61243°, W83.75575°). A distant Aaron House for scale.

Many Wooster students and alumni will immediately recognize all the elements of a typical roadside outcrop of the Cincinnatian Group in winter: gray rocks matching the gray sky, the muddy ditch at the base, and the thin verge of grass extending to the road.  Alternating limestones, siltstones and shales give the outcrop its jagged appearance.

Some of the best Ordovician fossils in the world are found in these sedimentary sequences, and the stratigraphy holds many mysteries despite over a century and a half of intensive study by geologists.  Wooster students have completed dozens of Independent Study theses with these rocks, and there are many more to come.  Aaron House is now pursuing a masters degree by assessing and interpreting the preservation of mollusk fossils in the Cincinnatian.

The wonder of natural history museums

July 9th, 2009

TALLINN, ESTONIA–Scientific museums preserve specimens and information from generations of researchers, collectors and students. The interiors of a typical paleontological museum contains windowless rooms filled almost to the ceiling with cabinets, each with dozens of drawers containing carefully labeled and cataloged specimens. Because information grows rapidly in science, the most important information on those labels is not the identity of the fossils but where they were found. The names and even systematic categories often change over the years as we learn new characteristics of particular groups, but the location information will always be critical for the value of the specimen for future researchers.

Today we visited the Institute of Geology at the Tallinn University of Technology. We were hosted by Dr. Helje Pärnaste, a paleontologist who specializes in Ordovician trilobites. She generously spent the day with us going through the collections. Using one of the best electronic cataloging systems we have ever seen, she was able to take us to drawers containing specimens from our study localities. We were able to add to our faunal lists and see better preserved fossils which will help in our future identifications. We concentrated on crinoids, of course, and were able to calibrate what we found which was truly new and see many other examples.

The Estonia Geology Research crew examining specimens in the Institute of Geology collections (left); a typical museum drawer (right).

The Estonia Geology Research crew examining specimens in the Institute of Geology collections (left); a typical museum drawer (right).

Much of our work involves finding specimens from our study locations and making quick and simple photographs for later reference.

Much of our work involves finding specimens from our study locations and making quick and simple photographs for later reference.

Again another scientific colleague we did not know before this trip helped us immensely and has become a friend. It is a remarkable universal fellowship. I hope we are able to return many such favors back in the United States.

A full geological circle

July 8th, 2009

View from a room in the St. Barbara Hotel, downtown Tallinn, Estonia.

View from my room in the St. Barbara Hotel, downtown Tallinn, Estonia (N59.431802°, E24.743355°).

The Wooster Geology Estonia team is now safely in Tallinn preparing for our visit to the paleontological collections in the university museum tomorrow. For me a private joy is that our hotel building is made of Ordovician limestone, the very same stone that I studied a month ago in Russia.

A Great Geological Day in Norway

June 24th, 2009

OSLO, NORWAY–This Wooster geologist had an excellent time here in the capital city of Norway today. I met up with Hans Arne Nakrem, a Norwegian paleontologist with the Natural History Museum, University of Oslo, and we looked at specimens he had collected from Jurassic strata on Spitsbergen, the Arctic island I am visiting tomorrow. He and his colleagues have some fascinating geological and paleontological hypotheses about some of the carbonate units and structures preserved with large marine reptile bones. There are opportunities here to help sort out the scenarios, especially with trace fossils.

Hans Arne also showed me one of the most famous fossils found in modern times: Darwinius masillae, an Eocene (Lutetian) stem group primate also known as “Ida” (pronounced “ee-dah”). It may be a transitional form between the prosimian and simians.

The fossil on the left (it is about 10 cm long) and a reconstruction on the right.

The fossil on the left (it is about 58 cm long) and a reconstruction on the right.

This fossil, which was found in 1983 in Germany, was only recently acquired by the Natural History Museum and formally described. In fact, we had lunch today in a sunny courtyard in the Botanical Gardens with Jørn Hurum, the paleontologist who led the research team studying D. masillae (and who is also famous for finding “Predator X“, an enormous pliosaur from the Jurassic of Svalbard). Inspiring.

Later Hans Arne gave me a tour of Oslo on what must have been one of the most beautiful days of the year. Among the many sights were some outcrops, including the Middle Ordovician interbedded shales and limestones shown below at the shoreline of the Oslo Fjord.

Middle Ordovician shales and limestones on the western shoreline of the Oslo Fjord.

Middle Ordovician shales and limestones on the western shoreline of the Oslo Fjord.

Thoughts on Future Wooster Geology Research in Russia

June 17th, 2009

I was very impressed by the Ordovician rocks I saw in the Leningrad Region on this past trip.  I had seen parts of the Ordovician System in Estonia nearby, but not to this extent nor this particular facies.  My model for Ordovician rocks had been based too strictly on those I’ve worked with in North America.  Now I realize that the environmental conditions and faunas were significantly different on the ancient continent of Baltica — enough to produce unexpected trace fossils, especially on and in the hardgrounds.  My perspective was changed, and thus the kinds of questions my students and I will be addressing in the next few years.

Nikolai, Sergei, Andrei, me, and my host Andrey in the Sablino Mines. I really don't know why there was a decorated Christmas tree in this cavern!

Nikolai, Sergei, Andrei, me, and my host Andrey in the Sablino Mines. I really don't know why there was a decorated Christmas tree in this cavern.

My Russian host, Andrey Dronov, was extremely generous and patient, freely sharing with me his scientific thoughts and his passion for Russian history and culture.  I could not have asked for better.  Remarkably, I met him for the first time on this expedition.  My other Russian colleagues were great fun, and they also taught me much about Russia and its geology.

I learned that field geology in Russia is difficult and certainly could not be done without a knowledgeable Russian host.  Every outcrop was farther, muddier, steeper and more overgrown than I expected.  In fact, we looked at outcrops American geologists would have given up on years ago.  If the rocks were there, we found them by hacking through the vegetation and digging them out with shovels.

Do you see the outcrops of limestone along the banks of the Lynna River?  Neither do I.  They are there, though, and Andrey and I found them with an epic jungle journey.

Do you see the outcrops of limestone along these banks of the Lynna River? Neither do I. They are there, though, and Andrey and I found them with an epic jungle journey on our last field day.

The major catch to doing Independent Study work in Russia for a student is that we could not take specimens back to Wooster.  We could, though, work in the geological lab facilities at the Academy of Sciences in Moscow, collecting enough data and images to keep a student busy for a year back home.  I would look forward to showing a student these unusual rocks and fossils, and I now know how better to prepare for work in Russia!

Goal!

June 8th, 2009

BABINO, LENINGRAD REGION, RUSSIA–Today we visited an active quarry, which is a different experience from the riverbank exposures and abandoned quarries we have been frequenting.  Quarry mud has a special character — a kind of purified mud, the kind of mud all mud aspires to be.  There are also very large trucks splashing by, giant rock saws whining, cranes lifting large blocks, and small groups of curious workmen who want to see what we are doing there with our hammers that now seem so small.  Active quarries can produce the very best exposures for geologists, especially those interested in the boundaries between rock units as we are.  This quarry at Babino N60.03035°, E32.38613°) is particularly good because they quarry Ordovician limestone by first cutting it vertically, and then lifting the rocks away in sections, revealing smooth surfaces perpendicular to bedding.

Cut surface through Ordovician section, Babino Quarry.

Cut surface through Ordovician section, Babino Quarry.

I want most to see the boundary between the Lower and Middle Ordovician rocks, and look at the trace fossils above and below it.  This boundary — a plane in the rocks which extends across northeastern Russia, Scandinavia, and parts of northern Europe — could not be better displayed than the way we saw it here.  It is an erosional surface which has been cemented into a carbonate hardground and then bored (to some extent that we are debating) and abraded smooth.  Above it is a significant change in the fossil fauna, a change which can be seen around the world.  In no place is this boundary better presented to geologists than here.

Lower/Middle Ordovician boundary in the Babino Quarry.

Lower/Middle Ordovician boundary in the Babino Quarry.

The trace fossils along this boundary are complex and may show both boring and burrowing behavior.  The distinction depends on when the sediments were soft, firm and cemented, and on the varieties of organisms which did the work.

Borings in the Lower/Middle Ordovician boundary at Babino Quarry.

Borings in the Lower/Middle Ordovician boundary at Babino Quarry.

I can’t take these specimens home for further examination.  I’d very much like to make thin-sections (slices of rock shaved down until almost transparent for microscopic analysis) of all the critical intersections, but that will have to wait.  Andrey collected many samples he can cut up and share from his lab in Moscow.

Typical Geological Field Day in This Part of the World

June 8th, 2009

LENINGRAD REGION, RUSSIA–Before I describe the usual routine we have for this fieldwork, I should note that we are in the “Leningrad Region”, which is distinct from the “St. Petersburg Region” in a formal political sense.  The Leningrad Region is essentially the rural portion of Russia outside the city of St. Petersburg.  The people who live here voted to retain the name “Leningrad” after the dissolution of the Soviet Union.  My colleagues say these people are “more conservative” and thus include many more communists than in St. Petersburg.  Interesting use of the term “conservative”, I’d say.

We rise from our finally-warm beds rather late for typical geological fieldwork, usually around 8:00 a.m.  I’ve at last figured out why: the “white nights” mean we have usable sunlight until deep into the evening.  We typically return to the field house at 8:00 p.m. and then begin the process of our dinner, which is usually ready by 10:00 p.m.  Not quite my Wooster schedule, but I’ve adapted!

We drive to our outcrops in a 1990s Russian version of a Fiat which, although lacking most of the modern conveniences, has heated seats!  (It is the only place I’m truly warm.)  The roads are poorly marked, so we spend a bit of time in orientation.  Since the pavements on the secondary roads — if there is a pavement — is badly potholed, we move slowly.  Most of our outcrops have been on riverbanks, so we stop on the top and then climb down a nearly vertical path (inevitably lined with stinging nettles and mosquitoes waiting for that outstretched hand) to the river itself.  After a geological introduction from Andrey, we scatter and explore the cliff, meeting together in an hour or so to exchange observations.  Andrey knows the stratigraphy precisely, with names for units as thin as a few centimeters which correlate for hundreds of kilometers.

On our way to an outcrop of Ordovician rocks along the Sass River.

On our way to an outcrop of Ordovician rocks along the Sass River.

Mud.  Mud everywhere.  Every slope is slick with it, and every outcrop has its roots in brown, sticky mud.  I am overly concerned with it only because I have a fixed set of clothes and no laundry possibilities for at least another week.  I desperately do not want to fall in it.

Typical riverbank fieldwork.

Typical riverbank fieldwork.

Every day has had rain in it.  I’m not good at predicting it here, even though the skies are extraordinarily wide above these forests.  As it starts to pour that old cowboy verse comes to mind: “Cloudy in the west, looks like rain.  Danged ol’ slicker’s in the wagon again.”

We do all this, of course, because the rocks are fantastic, with each exposure a puzzle to be solved, and every piece you break off shows a sight no human has seen.  Scientific and historical treasures await us every day.  It is also the time our diverse team bonds over common goals and wonders.  No language is needed when one geologist grins and shows another a particularly well-preserved fossil, or a sequence boundary stunning in its clarity.  I have the best job ever.

Ordovician Hardgrounds

June 7th, 2009

SASS RIVER, LENINGRAD REGION, RUSSIA–The main geological attractions for me on this expedition are the abundant carbonate hardgrounds in the Lower and Middle Ordovician in this part of the world.  A carbonate hardground is a cemented seafloor.  What were soft sediments on the bottom were cemented with carbonate minerals (calcite in the Ordovician) so that they became a rocky surface several centimeters thick.  The sediment is usually carbonate mud and shells, so the result is essentially a limestone seafloor.  Many invertebrate animals colonize these hard surfaces by wither encrusting them or boring into them.  Those eocrinoids illustrated earlier, for example, often encrusted Early and Middle Ordovician hardgrounds.

Today at the Sass River Carbonate Mound locality (N60.02316°, E32.62471°) we saw numerous hardgrounds bored by a shallow variety of a trace fossil called Trypanites.

Borings in Ordovician hardground fragments.

Borings in Ordovician hardground fragments.

These are the most common borings in hardgrounds.  This particular type of Trypanites is remarkably shallow — often appearing as pits rather than the usual penetrating cylinder.  Another difference between these hardground fossil faunas and those I know best in North America and western Europe.

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