Murray Batchelor Department of Theoretical Physics and Centre for Mathematics and its Applications, The Australian National University Mathematical approach to modelling the growth and form of microbial mats and stromatolites Wednesday 8th, September 14:05-14:55pm, Carslaw Lecture Theatre 273. In this seminar I will discuss attempts to model the growth and form of microbial mats from the perspective of the mathematics of evolving surfaces. Microbial mats arise from the environmental interactions of microbial communities (microbialites). The mats evolve over time to form internally laminated organosedimentary structures (stromatolites). We have proposed a biotic model which considers the relationship between upward growth of a phototropic or phototactic biofilm and mineral accretion normal to the surface. These processes are seen to be sufficient to account for the growth and form of many ancient stromatolities. These include domical stromatolites and coniform structures with thickened apical zones typical of Conophyton. More angular coniform structures, similar to the stromatolites claimed as the oldest macroscopic evidence of life, form when the photic effects dominate over mineral accretion. This work is part of a long term project with Bob Burne (Earth and Marine Sciences, ANU) and Bruce Henry (Applied Maths, UNSW), and most recently Tracy Slatyer (PhB program, ANU).