Geofísica

Nazca subducted plate under stable South America (SA) influences the position and thickness of the transition zone (TZ) under the continent. TZ variations are associated with mantle temperature and also to mantle P- and S-waves velocities. TZ thickness is an indirect method to map Nazca slab position at greater depths. Recent tomography results show that Nazca plate is being held below TZ for latitudes around 20 o S and longitudes between 70-55 oW.

The South American continent is composed by diverse geological units, from its ancient Precambrian stable platform to the now active Andean orogenic belt. However, the structure of its lithosphere and the dynamics of its interaction with the underlying mantle are still unclear and debated. Waveform tomography can resolve 3D distribution of shear-wave velocity, sensitive to temperature and composition in the crust, upper mantle and transition zone, but, until recently, seismic data sampling was scarce and uneven.

Paleoclimate studies on speleothems commonly use oxygen isotopes as a record of precipitation variability and carbon isotopes to document soil, vegetation, and atmospheric processes. Magnetic minerals in speleothems record complementary paleoclimate information but need to be interpreted within the context of the particular geographic and geologic setting in which a karst environment occurs.