Geofísica

Based on analytical, numerical or purely conceptual models, in the last decades different mechanisms were proposed to explain the existence of large escarpment along divergent continental margins persisting for more than 100 million years, invoking both syn- and post-rift geodynamic processes.

The evolution of escarpments bordering the coast during the post-rift phase is numerically simulated mostly by landscape surface processes models. However, there are few thermomechanical models that were applied to study the post-rift evolution of these escarpments.

we model some accepted brittleness indicators in rich organic shales. The rock is modeled as an effective poroelastic vertical transversely isotropic medium (VTI), composed by clay minerals and kerogen. The elastic properties of this composite medium are computed using the anisotropic theory of Ciz and Shapiro.

The formation and evolution of the present transcontinental Amazon river, the largest drainage system on Earth, is a result of the combined effect of different geodynamic processes. The Andean uplift and the increase in surface denudation along the cordillera affected the stratigraphic evolution of interior and marginal sedimentary basins in northern South America.

The Florianópolis Dyke Swarm is located in the Santa Catarina Island (Southern Brazil), encompassing also the nearby coast. This swarm belongs to the Paraná Magmatic Province, whose emplacement preceded the South Atlantic opening. The dykes are tholeiitic (very few transitional are found) and most of them trend NE-SW, with subordinate NW-SE orientation. The rocks have SiO2 varying from 50 to 55 wt% and TiO2 >3 wt%.

The greatest drainage system in the world, the Amazon River system, drains an area of about six million square kilometers in Northern South America, including parts of the Central and Northern Andean Cordillera, the Amazonian Craton and lowlands. Based on evidences from the Foz do Amazonas basin, the establishment of this transcontinental river system flowing eastward occurred in Late-Miocene. However, the landscape evolution of Amazonia that culminated in this huge drainage system is a matter of debate, as well as the processes that guided this evolution.

The Paraná Magmatic Province (PMP) is one of the largest in the world, and the primary volcanic phase took place at 134-133 Ma, preceding the Western Gondwana breakup. The northern PMP is characterized by dominant high-Ti basalts (Pitanga and Paranapanema types), with rare low-Ti ones (Ribeira type), whereas the southern PMP is marked by widespread low-Ti basalts (Esmeralda and crustalcontaminated Gramado types) and limited high-Ti rocks (Urubici type). Hafnium isotope data for 30 representative samples of these groups (except Gramado) are presented.