Professor Maggie Cusack

(University of Glasgow)

at 7.30 pm in the Gregory Building, Lilybank Gardens, University of Glasgow

 Brachiopods – recording environmental conditions while under biological control

 

With their long geological history and stable low magnesium calcite, Rhynchonelliform brachiopods are attractive sources of environmental data such as past seawater temperature. The outer primary layer of acicular calcite is isotopically light in both δ¹⁸O and δ¹³C while the secondary layer calcite fibres are in oxygen isotope equilibrium with ambient seawater. The calcite fibres of the secondary layer are parallel to the shell exterior. Electron backscatter diffraction (EBSD) reveals that the fibres are effectively single crystals with the calcite c-axis perpendicular to the fibre axis. The granular nature of the fibres is evident in Atomic Force Microscopy (AFM) where the addition of bands of calcite granules to the growing fibre is clear. These bands of granules are thus added over the duration of fibre growth with crystallographic orientation being maintained throughout. Although there remains much to be understood about how this precise biological control is achieved, the attainment of isotope equilibrium under such strict biological influence is counter-intuitive.

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The Moine Thrust Belt is one of the great sites for world tectonics. The NW Highlands are visited by structural geologists from all over the world each year and generations of students have learnt how to map and understand mountain building processes. Some of this importance arises as an accident of history: the thrusts in NW Scotland were amongst the first to be so recognised anywhere. Additionally – the first systematic approaches to describing the processes and products of faulting come from Moine thrust sites. But research has continued since these roots in the late nineteenth century. Much of our understanding of grain scale deformation, critical for understanding how rocks flow, was derived from samples from NW Scotland. This talk will outline these scientific discoveries then explore how they have been applied around the world, to active mountain belts and continental tectonics, through to exploring for oil and gas in the deep oceans.

Advance notice of the Annual General Meeting at 7.30 pm after which there will be 2 short talks and then an opportunity to network, as it is called nowadays, with some festive fair.

Further details in the next billet

8th January 2009

Professor John Gordon

(Scottish Natural Heritage)

at 7.30pm in the Gregory Building, University of Glasgow