Archive for June, 2017

Revisiting the Gironde Estuary for our last day of fieldwork in southwestern France

June 7th, 2017

La Barde, France — Today Paul Taylor, Macy Conrad (’18) and I had our last fieldwork in France for this expedition. We returned to sites along the eastern shore of the Gironde Estuary to study the Biron Formation (Campanian, Upper Cretaceous), thus completing our three-part stratigraphic survey along with the Barbezieux and Aubeterre Formations. Macy is seen above crouching at the Caillaud South locality.

This is a view of the Caillaud South cliff from the south. The camera can’t convey how very white the rocks are and still keep the rest of the image in a correct exposure. A salt marsh is in the foreground.

The Pycnodonte vesicularis oysters are common at the Caillaud south locality, but they are well cemented into the limestone matrix. We’re looking here at an articulated shell with the right valve on top. This would have been the oyster’s living position.

There is a normal fault exposed in the Caillaud. It is still Biron Formation in either block, but the facies are slightly different on one side from the other.

This part of the estuary was the site of a significant Gallo-Roman settlement.

We also revisited the north side of Caillaud, where again it is Biron Formation with about a meter of Barbezieux on top of the cliff. The structures to the left are fishing towers.

Bryozoans are abundant in this exposure. Here is a nice bryozoan colony, probably the cyclostome Meliceritites, according to Paul.

Talmont-sur-Gironde from the south. This tiny place receives half a million visitors a year. Note the tidal mudflat in the foreground. We were near low tide.

This is an aerial view of the village, courtesy of Wikipedia. It is nearly surrounded by the sea at high tide. The village was founded in 1284 by Edward I of England. In 1652 it was destroyed by the Spanish. I’m surprised it survived World War II.

I’ll end this post with a French wildflower of some type we saw today. It symbolizes the beautiful countryside we had the privilege to explore. Thank you again to Paul and Patricia Taylor for hosting us so elegantly. Paul was also a spectacular field driver on the small country roads, and his knowledge of the fossils and stratigraphy is astonishing.

We have one more day in southwestern France, and then Macy and I head back to Paris.

 

 

A day of rocks and churches in southwestern France

June 6th, 2017

La Barde, France — This is our second-to-last day in southwestern France on this research expedition. Macy Conrad (’18), Paul Taylor (Natural History Museum, London) and I are continuing our study of sclerobionts on Upper Cretaceous (Campanian) oysters. I know the images of us facing into yet another set of white rocks are getting dull, so we’ll get the field shots out of the way first! Above, Macy is looking at the Barbezieux Formation just outside the village of Bonnes, a locality new to us on this trip.

Our second stop was one we visited last week: the Barbezieux Formation exposed in a narrow lane (“Chemin”) in Aubeterre. Another successful day with the Cretaceous oysters and their associates.

We visited two notable churches during our journey today. This one in St. Aulaye is notable for its very old tower and preserved Romanesque facade.

The Medieval carvings around the entrance are delightful. This is a man and what is apparently his donkey.

The second church we visited as in Bourg-du-Bost. This is a Thirteenth-Century building mostly intact.

The interior is richly decorated, and had automated organ music playing as we entered. The lights also switched on and off in a pattern I didn’t catch.

This church is known for its 13th century frescoes still mostly in place with their original colors.

The ceiling of the sanctuary is magnificent. Much attention was given over the centuries to detailed ornamentation and preservation in this relatively small country church. It survived countless wars in this region, including the most devastating ones of the 20th century.

Location GPS Unit Position
Bonnes 171 Barbezieux N45° 14.735′ E0° 08.935′

A day of collecting Cretaceous fossils on the southwestern coast of France

June 5th, 2017

La Barde, France — Today Team France returned to the Gironde Estuary on the southwest coast of France to study the Upper Cretaceous (Campanian) fossiliferous limestones and marls. We visited new sites and some we scouted out last week. Above is Pointe de Suzac, just south of Royan, where the Aubeterre Formation is well exposed. It was another beautiful day. Rather cool, in fact, during the morning.

The oyster beds we’re interested in are very well exposed here. The shells appear to be in random orientations, likely the result of storm waves stacking them up in piles.

In fact, at the outcrop is the modern equivalent: recent oyster valves piled together.

The southern side of Pointe de Suzac shows at least six of these oyster beds in the Aubeterre Formation, each separated by a thin marl rich in erect bryozoan fragments. The bedding planes are also exposed here, giving us a three-dimensional view of the deposits.

The sediments below the oyster beds are rich in other fossils. Macy found regular echinoids, rudists, pectenids, unknown flat bivalves, and isolated large oysters. The unit is thoroughly riddled with Thalassinoides shrimp burrows.

The branching fossils here are bryozoans. The small disks are large foraminiferans.

The headlands of Pointe de Suzac are dominated by thick concrete bunkers and gun emplacements that were part of the “Atlantic Wall” built by the Germans in World War II. Note the battle damage on this one.

This area held the last pockets of German resistance to the Allies in Europe. It was heavily bombed and shelled in 1945 during the liberation of Royan, which was a horrible event for the local French citizenry.

Later in the day we returned to the roadcut above Plage des Nonnes to see the oyster beds in the Aubeterre Formation. Macy and Paul are examining the shells in, again, six beds, separated by the same fossiliferous marls.

Not all localities are beautiful in France! Our last stop of the day was in a parking lot in Mirambeau. Here we looked at a very bryozoan-rich part of the Barbezieux Formation.

Another successful day. Thank you again to Paul for the expert guidance and driving!

Location GPS Unit Position
Pointe de Suzac 168 Aubeterre N45° 34.933′ W0° 59.352′
Pointe de Suzac south 169 Aubeterre N45° 34.599′ W0° 59.382′
Mirambeau 170 Barbezieux N45° 22.211′ W0° 34.252′

Wooster Geologists get to work in southwestern France

June 4th, 2017

La Barde, France — After a day of almost solid rain, we woke up the next morning to brilliant weather in southwestern France. Macy, Paul and I drove to the small town of Archiac, where we collected a bag full of gorgeous specimens of the oyster Pycnodonte vesicularis from the Aubeterre Formation.

The oysters could be easily pulled from the marly matrix. Our goal was to collect as many specimens with fossil sclerobionts on them as we could. Sclerobionts are organisms that live in or on hard substrates, in this case it means borings and encrusters.

Thanks to Paul Taylor for this modification of the stratigraphic column from Platel (1999). The three formations we are collecting from are the Biron, Barbezieux, and Aubeterre, all in the Upper Campanian.

We also visited an outcrop of the Segonzac Formation near Segonzac itself so Paul could collect bryozoans. We were at the edge of a vineyard.

The view from our last outcrop was wonderful. Peaceful countryside. That’s our field car parked on the roadside.

Location GPS Unit Position
Archiac 166 Aubeterre N45° 31.413′ W0° 17.909′
Chez Allard 167 Segonzac N45° 37.040′ W0° 11.546′

A day of geology on the coast of southwestern France

June 2nd, 2017

La Barde, France — Today we traveled west to the Gironde Estuary on the southwest coast to continue our survey of Campanian fossils. It looks like we will be working on the sclerobionts found with the extensive Pycnodonte oyster beds. Macy is above examining one of the best exposures of these fossils at a roadcut above Plage des Nonnes.

Our first stop was a roadcut in Mortagne of the Segonzac Formation, the oldest of the Campanian units we’ve seen so far.

The next outcrop was of the Biron Formation at the southern side of Caillaud. It is flanked by a salt marsh, with more open ocean conditions farther along.

Macy stands here on the fossiliferous Biron Formation at Caillaud south.

Another place where the ocean would love to kill me.

The Caillaud north locality was very fossiliferous, including excellent cheilostome bryozoans like Onychocella above. Despite the diversity of fossils here, there aren’t enough encrusted and bored oysters for us.

The cliffs just south of Plage des Nonnes. Definitely a location to visit at low tide.

These are some of the abundant Pycnodonte oysters we saw in the roadcut above Plage des Nonnes. We will certainly return to this outcrop later.

Besides the research, there were of course many other sites of interest. I took several images of this salt marsh at Caillaud south, for example, to use in my Sedimentology & Stratigraphy course.

We found this large jellyfish at Plage des Nonnes. The thickness and rigidity of the “jelly” is amazing.

This is the Talmont church perched on an outcrop above the sea.

The Romanesque, intricately carved entrance to the Talmont church.

It was an excellent day of culture and geology in France!

Location GPS Unit Position
Mortagne 160 Segonzac – lower N45° 28.763′ W0° 47.496′
Cliff north of Mortagne 161 Segonzac – upper N45° 28.963′ W0° 47.943′
Caillaud south 162 Biron N45° 31.805′ W0° 53.629′
Caillaud north 163 Biron N45° 31.916′ W0° 54.206′
Plage des Nonnes 164 Aubeterre N45° 33.534′ W0° 57.895′
Roadcut above Plage des Nonnes 165 Aubeterre N45° 33.627′ W0° 57.894′

 

Wooster Geologists begin fieldwork in southwestern France

June 1st, 2017

LA BARDE, FRANCE–Macy Conrad and I began our paleontological fieldwork in what may be the most beautiful part of Europe: southwestern France. Our superb guide and colleague is Natural History Museum scientist Dr. Paul Taylor, a long-time friend who has a home in this region with his wife Patricia. Above is a view of our first location: Aubeterre-sur-Drone. Extraordinary. And note the weather!

French food is indeed all it is said to be. This was my lunch: Gallette au Thon. Simple, I know, but very good.

This is our first outcrop. Macy is standing at an exposure of the Biron Formation, a Cretaceous (Campanian) limestone full of fossils, especially Pycnodonte oysters. Many of these oysters are encrusted by bryozoans. This is the “Garage Esso” location, also known as Route D17, in Aubeterre. We are in the exploratory phase of the project — essentially sorting out projects.

The overlying Barbezieux Formation (also Campanian — all the units are Campanian today) has well-exposed Pycnodonte oyster banks. These are of particular interest to us, especially if they are bored or encrusted. This is the “Chemin” section in Aubeterre.

More Barbezieux Formation further up the lane.

Our third unit is the Aubeterre Formation, which dominates the top of the city. This is the “car park outcrop”. All of these rocks are cliff-forming white limestones with abundant fossils.

Paul knew a field near Le Maine Roy where fossils from the Maurens Formation are exposed. This did not sound like a productive site, but it was the best of the day. Above you see a pile of rocks marked by a stake. These are larger stones removed from the fields by farmers. (I was reminded of what many French farmers in the north continually extract from their soil: World War I artillery shells!)

The many fossils include numerous large rudistid clams. It is  hard to imagine these large cones as bivalves, but they are. Rudists go extinct at the end of the Cretaceous.

This is a view of the top of a rudist with its right (capping) valve intact. It has a beautiful mesh structure.

Our last stop of the day was a roadcut near Chalais exposing the Biron Formation. It had a great diversity of fossils, including echinoids, sponges, oysters, and ammonites. It did not have an abundance of sclerobionts, so it probably won’t be a site for us in the future.

In Aubeterre we visited two fantastic churches. The first was St. Jacques. Most of it had been destroyed in the 17th century religious wars, but the Romanesque facade remains. This is the main entrance.

The primary attraction of the remnants of St. Jacques is a set of Medieval carvings. They are extraordinarily detailed, depicted all sorts of mysterious fantastical animals and people.

The second church in Aubeterre is very geological. St. Johns is underground, being carved as a cavern from the Barbezieux Formation. Here is a view of the entrance to what remains.

Inside is a huge space in which the sanctuary is carved. This is one of the largest such underground structures known.

The centerpiece is this reliquary, designed to look like the structure over the tomb of Jesus in the Church of the Holy Sepulchre in Jerusalem. Again, all this is carved out of the limestone.

We are staying in the gorgeous French home of Paul and Patricia Taylor in La Barde. It is an 1820 converted farmhouse, both beautiful and comfortable. The River Dronne is just a few steps away. We’ll have more photos of this wonderful and peaceful place in later posts.

I’ll end this day’s post with a view of some peaceful French woods near a field site.

Location GPS Unit Position
Garage Esso, Route D17, Aubeterre 153 Biron N45° 16.212′ E0° 10.274′
Route D17, Aubeterre 154 Barbezieux N45° 16.127′ E0° 10.268′
Chemin, Aubeterre 155 Barbezieux N45° 16.088′ E0° 10.257′
50 m up lane, Aubeterre 156 Barbezieux N45° 16.115′ E0° 10.229′
Back Chateau entrance, Aubeterre 157 Aubeterre N45° 16.362′ E0° 10.262′
Car Park, Aubeterre 158 Aubeterre N45° 16.344′ E0° 10.176′
Le Maine Roy 159 Maurens N45° 19.383′ E0° 07.885′
Chalais roadcut 160 Biron N45° 16.642′ E0° 02.395′

 

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