A rainy day in the Mainz Basin

August 12th, 2010

View of the vineyards near Wöllstein, Germany.

View of the vineyards near Wöllstein, Germany.

OPPENHEIM, GERMANY–I want this termed Wilson’s Law: “The amount of mud encountered at an outcrop is inversely proportional to the quality of the fossils found.” Maybe it is my desert heritage, but I absolutely detest mud on my boots. Especially deep sticky quarry mud that grips lug soles and builds a progressively larger glob with every step. I try very hard to avoid slogs through it, but I’ve been spectacularly unable to avoid it in some places. Far too often I’ve slipped and slid through the glutinous stuff to find the rocks at the end to be distinctly unfossiliferous. Well mudded for little reward. Such was the case at the Rüssingen Limestone Quarry pictured below:

Today was a wet one in the Mainz Basin, and my fossil bag remained relatively empty except for some mollusk shells with borings (many of which are well described on this amateur’s page). Still, the geology was very interesting. The Mainz Basin is not a true basin in the geological sense. It is better described as a fracture zone at the western border of the Upper Rhine Graben. We were most interested in the shallow marine and brackish water Oligocene sediments deposited within these boundaries. Some of the sediments rested directly on sea cliffs of Permian rhyolite which was spectacular (but alas, not photogenic).

Clasts in the Alzey Formation (Oligocene, Rupelian) exposed near Wöllstein, Germany. The large pebble by the two-Euro coin is a Permian rhyolite; the white pebbles are from quartz veins in metamorphic rock. Both clast types were derived from nearby rocky cliffs during deposition.

Our last stop of the day was the Naturhistorisches Museum Mainz (Mainz Natural History Museum). This was much fun, especially since we had a special dinner with the director and staff in the galleries. The collection and displays are very good. I could have the usual photo of some vertebrate fossil in a case, but instead I was taken with a humble drawer of fossil snails packed in cotton so that they appeared to be floating in clouds:

Wooster Geologist in The Netherlands

August 8th, 2010

An outcrop of the Type Maastrichtian in Maastricht, The Netherlands. The square tunnels were dug in the Middle Ages for building stone. The rock is a limestone.

MAASTRICHT, THE NETHERLANDS–This is the first day of the International Bryozoology Association post-conference field trip. We took a train south from Kiel to Hamburg, Germany, and then connected with another train to Cologne. After spending a half-hour at the Cologne Cathedral (right next door to the train station), we took a bus west to Maastricht, The Netherlands, on the Maas River. We then spent the rest of the day in the ENCI cement quarry exploring the very fossiliferous Maastricht Formation, which is the type section of the Maastrichtian Stage described yesterday.

One of my favorite fossils in the Maastricht quarry. This is an external mold of an aragonitic shell in which the borings were filled with calcitic sediment. The result is a set of casts of the original borings.

The last of Scorpion Wash

June 11th, 2010

MITZPE RAMON, ISRAEL — The 2010 Wooster Geology Israel team finished its work today in the Upper Cretaceous rocks at our northern locality, Wadi Aqrav.  We measured several dozen cobbles from the base of the Menuha Formation, and then collected fossils from the Zihor Formation which we had previously measured.  We are now looking forward to a shabbat dinner at the home of our hosts Yoav and Noa, and then a trip tomorrow to visit Masada and the Dead Sea.

View of the cobble-bearing bedding plane at the base of the Menuha Formation (Late Cretaceous) from the cliff above.

An abraded oyster attached to the bored surface of one of the cobbles. This is the kind of hard-substrate paleontology I enjoy.

On the left is a large ammonite found in the middle of the Zihor Formation. It is encrusted on one side by oysters. On the right is a bit of vertebrate bone incorporated in the cobbles at the base of the Menuha Formation. (Yes, I think it must be from a dinosaur.)

Which came first?

May 27th, 2010

NEW ALBANY, MISSISSIPPI — The Cretaceous oyster above was collected from the Coon Creek Beds of the Ripley Formation (Upper Cretaceous) near Blue Springs, Mississippi.  The holes are borings called Entobia which were produced by clionaid sponges which built a network of connected chambers inside the shell so that they could carry out their filter-feeding with some safety from grazing predators.  The branching white fossil is a cyclostome bryozoan, probably Voigtopora thurni.  Which was present first on the shell, the borings or the bryozoan?  Is there evidence that they were living at the same time?  The largest holes are about two millimeters in diameter.

Wooster Geologists in Alabama!

May 20th, 2010

Mark Wilson (Wooster), Caroline Sogot (University of Cambridge), Megan Innis (Wooster) and Paul Taylor (Natural History Museum, London) on our first evening in Alabama. This is our "before" photograph. Let's see what we look like in 10 days of mud, sun and mosquitoes.

GREENVILLE, ALABAMA–We were told many times before this trip that we will find the people in the Deep South to be friendly.  This has been very much the case from the employees at the Atlanta airport to the young man in Greenville who insisted on carrying our few small bags of groceries out to the car.  We also knew it would be hot, muggy, and that at the store we could buy (if we ever wanted to) loads of pig’s ears and feet!  It is a delight to experience such cultural gradients in our own country.

Megan Innis, a senior geology major at The College of Wooster, is here with me to pursue her Independent Study project on changes in bioerosion patterns across the boundary between the Mesozoic and Cenozoic Eras (the “K/T” boundary marking the end-Cretaceous extinctions).  This event 65 million years ago was the result of an asteroid impact which triggered a global ecological catastrophe, most famously taking out the dinosaurs.  Megan and I want to see what happened to the community of organisms which bore and drill shells and other hard substrates.  Some of the best exposures of rocks associated with this extinction are found here in southern Alabama and neighboring Mississippi.

My friend and colleague Paul Taylor of the Natural History Museum in London is here with his PhD student Caroline Sogot (University of Cambridge) to investigate similar patterns in the other hard substrate faunas across the boundary, especially bryozoans.  We have joined forces so that we can most efficiently measure sections and collect specimens, many of which we will be sharing in later laboratory analyses.

Tomorrow is our initial orientation in the field.  We have been joined by Peter Harries of the University of South Florida and two of his graduate students, and in the morning we will meet Jon Bryan of Northwest Florida State College.  Peter and Jon are Cretaceous experts who know the local outcrops and are enthusiastic about the chance to talk paleontology for days on end!

Wooster Geologist in Ohio!

December 16th, 2009

CAESAR CREEK STATE PARK, OHIO–I’ve definitely extended my field season as far as possible.  (And what a season it has been.)  My last fieldwork at the end of this research leave was in Ohio, about three hours south of Wooster.  I visited Caesar Creek State Park this morning where a large cut through an Upper Ordovician section has been set aside as a fossil preserve of sorts.  It is an emergency spillway for Caesar Creek Lake, which is maintained by the US Army Corps of Engineers.  Many Wooster paleontology field trips have stopped here.  Fossils can be collected, but only with a permit (obtained at the visitor center) and following significant regulations.  The fossils are diverse and abundant, including all the stars of the Ordovician seafloor.

My task was to find, photograph and measure an old trace fossil friend: the boring Petroxestes pera.  This is a slot-shaped excavation in carbonate hard substrates formed by bivalves (probably in this case the modiomorphid Corallidomus).

The boring Petroxestes pera (the name means "purse-shaped rock-grinding") in a hardground at Caesar Creek State Park.

The boring Petroxestes pera (the name means "purse-shaped rock-grinding") in a hardground at Caesar Creek State Park.

These elongated holes are among the first bivalve borings.  Some of my students and I think they may have been formed in clusters, and they also may be oriented relative to each other and their local environment.  In any case, I found plenty.  It was an astonishingly cold morning, though, so I didn’t waste any time on the outcrop!

Yes, this photo is here mainly to show just how tough Wooster Geologists are.  And there are some very nice brachiopods and bryozoans!

Yes, this photo is here mainly to show just how tough Wooster Geologists are. And there are some very nice brachiopods and bryozoans!

A very bored Permian brachiopod

November 15th, 2009

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COLLEGE STATION, TEXAS–I never get tired of that too-obvious joke. I found the above productid brachiopod on the last outcrop of our little Texas expedition. It has been drilled by barnacles, which leave a distinctive slit-shaped hole with a tiny little comma shape at one end. It may not look special here photographed on my backpack in the sunlight, but it is. Hard substrate communities in the Permian are still poorly known. This specimen tells us that a future trip may reveal many more such specimens.

Paleontologists (and anyone else) should be able to tell me whether these borings were produced during the life of the brachiopod or after its death. Your determination can be posted in the comments below!

Wooster Geologist in Texas

November 12th, 2009

Halbouty Geosciences Building on the campus of Texas A&M University

Halbouty Geosciences Building on the campus of Texas A&M University

COLLEGE STATION, TEXAS–I arrived this afternoon in beautiful central Texas to give a talk at Texas A&M University on bioerosion.  If you click the link you can see my PowerPoint slides.  The talk went well enough and there were many questions.  It is a fun topic because it is at an intersection of geology and biology.

Tomorrow Tom Yancey and I drive to Brownwood, Texas, to begin a field project in the Permian.  There are some very curious “worm tube” clusters that I hope to post photos of soon.  I’m excited to be able to work in the Permian, which I haven’t done since my dissertation days.

The weather is absolutely perfect here!

Jurassic Cryptic Marine Ecosystems

September 8th, 2009

Note the curly worm tubes and borings made by another type of worm.  There are also tiny little sponges in this view, and even tinier brachiopods.  This is a "cryptic community", meaning it lived in a protected space, in this case on the underside of a coral colony just above the sea floor.  The study of cryptic marine communities and their evolution has been a speciality of the Wooster paleontology lab.  (Matmor Formation, Jurassic, Makhtesh Gadol.)

Note the curly worm tubes and borings made by another type of worm. There are also tiny little sponges in this view, and even tinier brachiopods. This is a "cryptic community", meaning it lived in a protected space, in this case on the underside of a coral colony just above the sea floor. The study of cryptic marine communities and their evolution has been a speciality of the Wooster paleontology lab. (Matmor Formation, Jurassic, Makhtesh Gadol.)

Tools of My Trade (At Least for Today)

September 3rd, 2009

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MAKHTESH GADOL, ISRAEL–The fieldwork could not have been better, although if you watched me all day in the desert sunlight you would have thought otherwise. After I hiked up into the Matmor Hills to find the right horizon, I spent hours in the same place collecting fossils off the surface and sieving the sediments to obtain tiny shells (especially of thecideide brachiopods). The goal is to thoroughly understand the paleontology of this unit, including how these organisms interacted with each other in that ancient Jurassic sea. The persistence paid off with a diverse set of brachiopods, corals, sponges, echinoids, serpulid worms, bivalves, gastropods, and the first ammonite I’ve seen in the Matmor Formation. There is enough complexity in this one site to support at least another two Senior Independent Study projects.

This view of a coral in cross-section shows how complex bioerosion can be.  You can see several holes in the brown coral matrix filled with white sediment.  Inside these borings are cross-sections of bivalve shells.  Note that some borings have more than one set, meaning the hole was occupied by nestling clams after the borer died.  The patches of shiny grey are silicified regions of the coral skeleton.  Since the coral was aragonitic, its original skeleton has been replaced by several minerals.

This view of a coral in cross-section shows how complex bioerosion can be. You can see several holes in the brown coral matrix filled with light tan sediment. Inside these borings are cross-sections of bivalve shells. Note that some borings have more than one set, meaning the hole was occupied by nestling clams after the borer died. The patches of shiny grey are silicified regions of the coral skeleton. Since the coral was aragonitic, its original skeleton has been replaced by several minerals.

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