I'd never been to this before, but heard good reports of the day, so Jan and I got tickets for it.
After checking parking and trains we decided on driving over and using the Park&Ride - horribly early start but train would have been even earlier, and cost more.
We began to meet friends right from getting on the P & R bus at Pear Tree, and saw lots of familiar faces during the day. As we had plenty of time, and wouldn't get into the Museum of Natural History until 9.30, Andrew, who we met on the bus, suggested going on into the city centre and walking back to see a bit of Oxford before we were immured in the lecture theatre for the day. We walked along Broad Street and saw the Bodleian Library before turning up Parks Road which gave a good view of the backs of Balliol, St John's and Trinity Colleges (not quite sure which is which, must do a guided tour sometime!)
The
museum is a lovely building in its own right, 19th C with iron columns and a glass roof. There is a gallery around the first floor and columns on the balustrade edge are made of all sorts of different stones. These two are a, on the left, "schorlaceous granite" from Cornwall (one with lots of tourmaline presumably), and a serpentine from the Lizard.
We heard six full length talks during the day: three before, and three after, the lunch break. The first three were:
- Professor Ros Rickaby: Evolving Enzymes: a window into past atmospheres
- Professor Mark Williams: The geological Anthropocene impact of humans
- Professor Jane Francis: When Antarctica was green: Fossil plants reveal Antarctica's climate history.
Ros Rickaby is a biogeochemist and "fascinated by the jigsaw of complex interactions between the evolution of mineralising organisms, ocean chemistry, atmospheric composition and Earth's climate."
She gave an insight into the way organisms had evolved at the genetic level, tracking their response to changing trace metal availability and focusing on the extremely abundant enzyme Rubisco which is responsible for photosynthetic carbon fixation.
I was interested in her example of red algae needing less Cu and Zn than green algae, so that an increase in the latter ties in with Cu and Zn availability. These metals in turn had become more abundant as oxygen increased in the atmosphere as they were no longer locked into sulfides. This is what enables organisms to become multicellular, so their availability is key to evolution.
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| Professor Mark Williams introduces his talk |
Mark Williams talk linked in well to this as he began by looking at how rivers began at the Archaean-Proterozoic boundary, a world without a biosphere, as braided deposits, with a distinct mineralogical signal of e.g. reduced pyrite and uraninite; deposits were sheeted, there were unstable banks and a lot of erosion. Then, oxygen became available at around 2.4 Ga ago the reduced minerals disappeared and then as plants evolved, banks became more stable, and the geometry changed to a meandering style with finer grained deposits. This is being reversed by human action as the biosphere is degraded and river flux increased. He concluded by discussing markers for recognising an Anthropocene world: extinctions, neobiota spreading globally, modification of landscape and technological interaction with the biosphere.
Jane Francis is a palaeobotanist who is currently the Director of the British Antarctic Survey. She took us through the fossil record present in Antaractica, especially the well preserved and easily retrievable fossil flora found on the ice-free Seymour Island, off the Antarctic Peninsula.
A sunny day, though a chilly breeze, enabled us to eat our sandwiches outside, admiring the dinosaur footprint trail across the lawn (sorry about the finger!)
You can see this well in
Google Maps
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Jack Matthews explaining correlation of the D and E surfaces
across a 9 km length of coast. |
The Oxford Colloquium is run by the Oxford Geology Group and profits go towards supporting students' field work. After lunch, and before the afternoon talks, postgraduate student
Jack Matthews, this year's winner of OGG's McKerrow cup, was presented with the cup and gave us his winning presentation: "Post-preservational processes: Implications for understanding and conserving of our oldest animal ancestors". I was particularly interested in this one as Jack had done his field work in the Mistaken Point area at the southern end of Newfoundland's Avalon Peninsula which we had visited several years ago on an OUGS trip with Tom Sharp.
He has been able to correlate the important D and E surfaces which are exposed at Mistaken Point with other exposures to the west, and 9 km away to the NE, showing that the deep marine Ediacaran macrofossil communities were not geographically restricted to localised habitats as had been predicted by some previous ecological models.
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| OUGS viewing the exposure at Mistaken Point |
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OUGS on the exposure at MP - note no boots, and low angle of
sun which shows the fossils better |
The exposures at Mistaken Point are reached by a 12 km drive along a graded road and then a couple of km walk across the barrens.
The exposures are on gently dipping surfaces, which slope away from the sea and are generally above wave level. This helps to protect them in some ways, but a small stream flowing along the base of the cliff at the back of the exposure is slowly smoothing off the surface.
Jack particularly discussed the effect of exhumation and weathering on the different types of fossil.
Fractofusus a "spindle" type tends to lie within the top surface of the sediment so that it is well exposed when the overlying ash is eroded.
Charniodiscus on the other hand, tends to stand proud of the surface which means that it is eroded along with the surface.
This can produce a sampling bias, depending on the length of time a surface has been exposed to weathering.
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A Fractofusus (lower left) and others.
Some of the volcanic ash is on the
surface. |
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Charniodiscus (frond to the left and
disc to the right), with a coating of ash |
Post-lunch speakers were:
- Professor Katherine Cashman: Volcanoes and Human Societies: Past, present and future
- Professor James Jackson: Continental contrasts: variations in the structure and strength of the lithosphere
- Professor Richard Fortey: Survivors
Kathy Cashman gave the same talk as she plans to give at the "Geoff Brown Lecture" at our OUGS AGM in Bristol next month, though she says "it is different every time". She looked at global and local impacts of volcanic eruptions and the long term nature of the human responses that may be required. Towards the end of her talk she touched on the record of the Icelandic sagas, and how that can be linked to the geological record of eruptions.
Professor Jackson uses a variety of techniques to examine the deformation of continental crust, especially actively deforming crust, at all scales. Although I found the talk fascinating, his delivery was extremely fast - too fast for my poor post-prandial brain and although I took away a series of "sound bites" I didn't manage completely to follow his argument. :( One thing that struck me was that he was referring to mantle quakes when the temperature was < 600 degrees Celsius - this is something that often comes up in discussions since "if the mantle is plastic and flowing e.g. at depth above a subducting plate, how can it fracture in a brittle fashion to produce an earthquake?" Must have a look for any papers!
Finally we were treated to
Richard Fortey, who went at a more easily assimilated pace as he discussed what it is that enables some organisms to survive multiple mass extinctions, outliving trilobites and dinosaurs and entire biosphere reorganisation.
Well worth going to, despite the long day!
