Central and South America collided earlier than expected

Geologists analyzing magnetic features of ancient volcanic rocks in Colombia’s Northern Andes established on September 7, 2026, that Central America and South America underwent their primary tectonic collision earlier than prior scientific estimates indicated. Rock signatures demonstrate that the major collision stages occurred before roughly 10 million years ago.

First author Victor Piedrahita and corresponding author J. Li coordinated an international team of geoscientists to examine the geological timeline. They focused on late Miocene volcanic deposits dating from roughly 12 to 6 million years ago in the Combia Volcanic Province located across central Colombia. The structures originated while the South American Plate converged directly against the continental mass of Central America.

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How magnetic minerals preserve records of ancient tectonic shifts

To reconstruct the tectonic movements of the era, the research team implemented magnetic fabric analysis, a method that measures the internal alignment of magnetic minerals to distinguish whether the underlying rock architecture stems from primary volcanic flow or from subsequent structural deformation triggered by tectonic compressions.

“Volcanic rocks can preserve a remarkably detailed record of geological processes,” said Victor A. Piedrahita. “Their magnetic fabrics help us determine whether deformation occurred before, during, or after the rocks were emplaced.”

The analysis verified that numerous rock samples retain primary fabrics generated by shifting magma or debris flows. This condition indicates that minimal tectonic disruption altered the Combia deposits during the late Miocene. Localized deformation remained strictly bounded.

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Evidence reveals peak crustal compression ended earlier than thought

Compiled geological data shows that the primary crustal shortening and heavy deformation in the Northern Andes concluded prior to the late Miocene. The most aggressive phases of mountain compression ceased before these volcanic formations developed.

“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,” stated Piedrahita and Li. “By the time these volcanic rocks formed, tectonic deformation had become weaker and more localized.” The measurements confirmed this regional pattern.

These conclusions allow researchers to refine evolutionary models of the Andes mountain range while charting how continental plate encounters shaped regional landmasses. The methodology also confirms magnetic evaluation as an effective tool for mapping ancient tectonic stress throughout volcanic zones.

The National Natural Science Foundation of China funded the geological investigation through research grants awarded to J. Li and Victor Piedrahita.