Speaker: Gustavo Martinez Mekler (Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México)

Title: Evolution of a Paleolake Subject to Volcanic Activity

Abstract:

On certain occasions Nature gives us access to privileged sources of information, such is the case of diatomite beds from a paleolake in Mexico that was heavily disturbed by volcanic eruptions over 2 million years ago. Computed tomography (CT) measurements, along blocks chiseled out of mine walls dug out from the extinct lake's bed, provide a sediment density fluctuation series. This information together with diatom species microscopy determinations and proton induced X ray emission studies (PIXE), suggests, in the light of a complex systems analysis, a scenario for the lake's evolution [1].
Statistical scaling properties are studied by tools previously developed for the study of intermittency in turbulent flows [2]. Within this framework, the determination of correlations puts into evidence the role of rare events (strong volcanic perturbations) in the onset of scale invariant regimes. These findings, in conjunction with diatom cluster analysis resulting from microscopy observations, suggest the presence of an underlying self-organized diatom dynamics [2,3]. Additionally, the occurrence of a threshold in the lake's depth above which a sharp dominance shift between the main coexisting diatom species took place is also inferred. The overall picture is a transition from eutrophic to mesotrophic conditions, which is opposite to the usual pattern. Our analysis attributes geological activity, mainly volcanism and faulting as main factors for the lake´s ecological transformations [1]. Comments on the modeling of this system in terms of both stochastic and deterministic dynamics will also be forwarded. The study is based on an interchange between theory, experiment and field work, supported by the confluence of geology, physics, mathematics, statistics, biology and ecology, both at the level of methods and concepts.

[1] G. Vilaclara, G. Martínez-Mekler, E. Cuna, E. Ugalde, “Diatom-inferred palaeoenvironmental changes of a Pliocene lake disturbed by volcanic activity”, Journal of Paleolimnology, Vol 44, 203-215 (2010).
[2]Edgardo Ugalde, Gustavo Martínez-Mekler, Gloria Vilaclara, “Scaling and extended scaling in sediment registers of a paleolake perturbed by volcanic activity, Physica A, Vol. 366, 485-494 (2006).
[3] G. Martínez-Mekler, E. Ugalde, G. Vilaclara, “Power spectrum crossover in sediments of a paloelake distrubed by volcanism”, Eur. Phys. J., Special Topics, 143, 217-222 (2007)

Lunch group: 4