LONG-TERM LANDSCAPE EVOLUTION OF THE ATLANTIC PASSIVE CONTINENTAL MARGIN, BUENOS AIRES, ARGENTINA

The project deals with the evolution of the South Atlantic passive continental margin (SAPCM-A) in eastern Argentina. The aim is to quantify processes, like uplift-, exhumational and erosional events by using three different geochronometers.

Combining apatite- and zircon-FT-data together with (U-Th-Sm)/He-data, it is possible to reconstruct the time-temperature-history (t-T-history) of each sample by using modeling-software.

The modeling-software (HeFTy and PECUBE) leads to detailed information of the evolution of the continental margin and therefore also to information to understand the recent Topography.

Passive continental margins are important geoarchives, which store information about incidents related to mantle dynamics, break-up of continents and other of exogenic and endogenic forces.

The SAPCM-A trends NE-SW and is linked to the SE-NW trending Salado-basin and the also SE-NW-trending Colorado-basin. These two basins are separated by the Sierras Septentrionales and the Sierras Australes, which both also trend NE-SW. FT-data, generated from samples from the different stratigraphic Lithologies of both of the two mountain-ranges will be combined with HeFTy- and PECUBE-models, to get new insights in the kinematic processes like cooling, exhumation/inversion, uplift rates and erosional events, which have taken place and formed the recent topography of the region. This area is also a key area to study the influence of Fracture Zones (transform faults, transfer zones) on the evolution of the SAPCM.

The Sierras Septentrionales is a flat mountain system and is surrounded by the Pampean plain. The hills reach their maximum of about 500 m a.s.l. near Tandil. The Sierras Septentrionales is build up of proterozoic crystalline basement covered by sedimentary rocks (Demoulin et al, 2005). The Sierras Australes is a fold belt trending in NW direction and can be sectioned in two main orographic units (Cobbold et al, 1986; Harrington, 1947). These two different units show different styles of deformation and different grades of metamorphism. The western part of the Sierras Australes is a very highly deformed unit and is build up of rocks from the lower greenschist facies (Cobbold et al, 1986). The eastern part shows much lower grades of deformation and metamorphism than the western part.