Lecture: Thursday November 19th 2015
Meston Lecture Theatre 1 at 6.30pm
The evolving impacts of the microbial
biosphere on the geosphere, from Earth’s
oldest fossils to last October
Dr. Alex Brasier (University of Aberdeen)
Earth is 4600,000,000 years old. I am thirty four. The
only way to really understand where we (organisms)
came from, and where we are going, is to look at the
evidence preserved in rocks. This story begins with a
critical re-examination of what were long called
Earth’s oldest fossil organisms (Wacey et al., 2015). I
will then leap forwards one billion years to ‘Planet
Earth’s mid-life crisis’. Here, 2.4 to 1.9 billion years
ago, rising atmospheric oxygen levels from oxygenic
photosynthesis possibly caused a global ‘snowball
Earth’ glaciation (Brasier et al., 2013) and then turned
the planet toxic for most of their anaerobic microbe
friends. In the rocks we see the results of this
chemical warfare: sulphate and iron oxide minerals,
formed in an atmosphere with free oxygen; carbon
isotopes of carbonate rocks compatible with vast
volumes of photosynthesising microbes in the oceans
(Brasier et al., 2011) and anaerobic microbes
retreating into the ocean sediment, forming new rock
types. Over the last year I have been examining
Recent abiotic and microbial carbonates of Mono
Lake, California, and initiating lab experiments in
Aberdeen aimed at recreating some of the processes
that might have fossilised our Precambrian microbial
ancestors. This talk will include an update on Mono
Lake findings, with some consideration of future plans
for astrobiogeochemographological research in
Aberdeen.
Join us as usual in the Map Room of the Geology Department for tea and biscuits from 5.30pm
Aberdeen Geological Society www.aberdeengeolsoc.org.uk
President : Alan Holmes, Secretary : Alex Fordham, Treasurer : Hugh Morel
c/o University of Aberdeen, Dept of Geology & Petroleum Geology, Meston Building, King’s College, Aberdeen, AB24 3UE