Magmatic rifting of Pangaea linked to onset of South American plate motion

The causes of the transition from amagmatic to magmatic rifting during continental break-up are not always clear and have been often linked to the break-through of a plume. However, stress fields recorded in the crust may offer new insights into the relationship between changes in the stress field and the onset of magmatism. In this paper stress fields recorded in the crust of North America are used to test possible causes of the break-up of Pangaea and the transition from amagmatic to magmatic rifting. Finite element models reveal that the most likely scenario for the break-up involves the initial northwest motion of North America at 230 Ma, followed by a south-southeast motion of South America at 200 Ma with the initiation of magmatism, and finally a weakened area between North and South America sometime soon after 200 Ma which resulted in North America being dominated by northwest motion once again. It was also determined that plate boundary structure and orientation play a large part in the recorded stress fields and must be taken into consideration when modeling continental break-ups and rifting.