Archive for August, 2017

Wooster’s Fossils of the Week: Oysters from the Upper Cretaceous (Campanian) of southwestern France

August 22nd, 2017

Wooster’s Fossil of the Week returns from its summer hiatus. It is appropriate, then, to feature as our first fossil of the new season an oyster species prominent in our summer research. This is Pycnodonte vesicularis (Lamarck, 1806), a very common fossil in the Cretaceous around the world. These particular specimens are from the Aubeterre Formation (Upper Campanian, Upper Cretaceous) exposed in the town of Archiac in southwestern France. They were collected by Macy Conrad (’18), Paul Taylor (Natural History Museum, London) and me during our June 2017 expedition. Above is the interior of a deeply concave left valve. The large spot near the middle is the single adductor muscle scar (thus the oyster, like all oysters, is monomyarian). It was a free-living oyster in soft, shallow platform marine sediments. This species has been used for all sorts of studies, from investigating paleoecology and evolution to paleoseasonality (see references below for a start).

This is the interior of the right valve, showing the corresponding muscle scar. The valves are very different in size and shape, so this oyster is termed inequivalved.The exterior of the right valve, with characteristic faint radiating ridges. The tag, by the way, indicates the locality. Every one of our hundreds of oysters is tagged in this way.Macy Conrad (’18) is seen here at the Archiac outcrop collecting specimens of Pycnodonte vesicularis.

A typical bed of P. vesicularis in the Upper Campanian of SW France. This one is exposed along the sea cliffs at Pointe de Suzac.

References:

Brezina, S.S., Romero, M.V., Casadío, S. and Bremec, C. 2014. Boring polychaetes associated with Pycnodonte (Phygraea) vesicularis (Lamarck) from the Upper Cretaceous of Patagonia. A case of commensalism? Ameghiniana 51129-140.

De Winter, N.J., Vellekoop, J., Vorsselmans, R., Golreihan, A., Petersen, S.V., Meyer, K.W., Speijer, R.P. and Claeys, P. 2017. Cretaceous honeycomb oysters (Pycnodonte vesicularis) as palaeoseasonality records: A multi-proxy study. EGU General Assembly Conference Abstracts 19: 4359.

Lamarck, J.B. 1806. Suite des mémoires sur les fossiles des environs de Paris. Annales du Muséum National d’Histoire Naturelle 7: 130-139.

Platel, J.-P. 1996. Stratigraphie, seédimentologie et évolution géodynamique de la plate-forme carbonatée du Crétacé supérieur du nord du basin d’Aquitaine. Géologie de la France 4: 33-58.

Videt, B. 2003. Dynamique des paléoenvironnements à huîtres du Crétacé supérieur nord-aquitain (SO France) et du Mio-Pliocène andalou (SE Espagne): biodiversité, analyse séquentielle, biogéochimie (Doctoral dissertation, Université Rennes 1).

Wooster Geology Professor Frederick W. Cropp III (1932-2017)

August 11th, 2017

Professor Fred Cropp taught geology at Wooster from 1964 to 1997. He was an extraordinary teacher and, in his own words, “a cheerleader for geology”. Many, many Wooster students became geologists in response to his enthusiasm, energy and spirit. I was one of them. His obituary and memorial page is here.

The Cooper Plots – Ecological Succession in Glacier Bay National Park and Preserve, Alaska

August 9th, 2017

I recently had the pleasure to work with a team of ecologists for eight days in Glacier Bay National Park and Preserve. The point of the trip was to reoccupy and expand investigations of the Cooper Plots established over 100 years ago in the wake of the retreating ice in the West Arm. A nice rundown of this ecological succession work is presented here on Glacier Hub. The ecology team recently published on their rediscovery of the plots, which was heroic considering the immense lands, intense brush and  sometimes cryptic description of the plot locations.

The accommodations and views in the West Arm of Glacier Bay were spectacular. Logistics of the project were supported by the National Park Service, who we gratefully acknowledge.

The team of ecologists included (left to right) Drs. Allison Bidlack (Director, Alaska Coastal Rainforest Center, University of Alaska Southeast), Sarah Bisbing (University of Nevada – Reno) and Brian Buma (University of Alaska Southeast). I was along to core trees at the sites (Wooster Tree Ring Lab) and to measure the size of alders.

Sarah and Brian cordon off one of Cooper’s 1-meter plots with string so we don’t trample the vegetation. Sarah reals out a 15-meter tape with Allison on the end somewhere deep in the alders. The group then carefully described the species present at each site among other observations and measurements.

The Russell Island raft served as headquarters for much of the trip.

Chasing Brian across the fjord was the typical start of a day working the Cooper Plots.

As it turns out there are multiple species of willow and distinguishing them from each other is not as straightforward as one might imagine.

Allison pauses in the West Arm on the way over to view Reid Glacier.

Not only did I learn more about the biosphere of Southeast Alaska, but I also learned something about cooking in the field and Wooster trips may benefit from this in the future.

This grizzly visited us a few times – quite possibly the most adorable bear in the region.

An excellent view of Marble Mountain looms in the distance.