A new study led by Victor Piedrahita and J. Li suggests the collision between Central and South America occurred earlier than previously believed, with the most intense phase of tectonic compression ending before approximately 10 million years ago. Researchers analyzed magnetic characteristics of volcanic rocks in Colombia to reach this conclusion.
Geologists examining volcanic rocks from the Combia Volcanic Province in central Colombia have revised the timeline of the Americas’ collision. The research team, led by Victor Piedrahita (first author) and J. Li (corresponding author), focused on late Miocene volcanic rocks, dating back approximately 12-6 million years, formed during the interaction between the South American and Central American plates.
The team employed magnetic fabric analysis, a technique that studies the orientation of magnetic minerals within rocks to determine if deformation occurred before, during, or after their formation. “Volcanic rocks can preserve a remarkably detailed record of geological processes,” says Dr. Victor A. Piedrahita. “Their magnetic fabrics help us determine whether deformation occurred before, during, or after the rocks were emplaced.”
Analysis revealed that many of the rocks retained primary magnetic fabrics, indicating little to no major tectonic deformation during the late Miocene. While some locations showed signs of deformation, these effects were limited in strength and geographic extent. This suggests that the strongest crustal shortening and collision-related deformation in the Northern Andes had largely concluded before the late Miocene period.
Piedrahita and Li explain that “Our data indicate that the most significant collisional events between Central and South America occurred earlier than we previously thought, mainly during the Oligocene-middle Miocene. By the time these volcanic rocks formed, tectonic deformation had become weaker and more localized.” The findings, published in *Earth and Planetary Physics*, could help scientists improve their understanding of the tectonic history of the Americas.
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