Geoffrey M.H. Ruiz, Geological Institute, University of Neuchatel, Switzerland
Sala d'actes de l'Institut Jaume Almera, 12.15H

Studies of active orogenic belt indicate that atmospheric and geodynamic processes may be strongly coupled through erosion ­ a hypothesis that has led to a debate over the relative importance of climate and far-field tectonic forcing in influencing erosion. I will address this debate by first 1) introducing low-temperature thermochronology (methods and limits), and secondly 2) developing the detailed long-term erosional history of a transect along the eastern slope of the Peruvian Andes for comparison with the climate and tectonic forcing histories of the region. Patterns of apatite fission-track apparent ages with elevation as well as compilation from far east oil datasets indicate a ten-fold increase in apparent erosion rate between 4 Ma and today in SE Peru. The time frame for this change corresponds to that of global climate cooling since the Pliocene associated with the onset of widespread glaciation and the development of El Niño like conditions. There is no informat
We dedicate our effort today to another poorly constrained mountain range i.e. the High and Anti-Atlas of SW Morocco. Climatic conditions are there drastically different from the Andes: it is dry and there is no assymetry in climate from one side (NW) to the other (SE) as across the Andes. So parameters other than active tectonism that may have an influence on the observed geomorphological assymetry can be excluded: mean annual precipitations are nearly identical from one side of the HA to the other in the region of investigation, and there is no obvious difference in rock types or structural grain between the northern and southern slopes . Little is known about the timing, rates and controls on the orogenic growth of the Atlas chain.